Background: Clavicle fractures are frequent (5-10% of all fractures) with midshaft fractures being the most common, accounting for up to 80% of all clavicle fractures. The best treatment option is still debated. Aim of this study was to evaluate the rate of scapular dyskinesis, clinical, functional, and radiological outcomes in patients treated surgically or conservatively for midshaft clavicle fractures.

Methods: This retrospective monocentric study included midshaft clavicle fracture patients (AO 15. A) treated operatively or conservatively from 2009 to 2022. Outcomes evaluated were scapular dyskinesis, Costant score, Disabilities of Arm, Shoulder, and Hand (DASH) score, radiological outcomes (nonunion and mal union rates), aesthetic and general satisfaction.

Results: 124 patients were included, 69 (55%) in the surgical group and 55 (45%) in the conservative group. Mean age was 54 ± 9 years and mean follow-up time was 8 ± 2 years. Scapular dyskinesis was present in 19.1% (13 / 69) patients treated surgically and 54.5% (30 / 55) patients treated conservatively (p < 0.05). The surgical group showed statistically better Constant score (p < 0.05) and radiological healing (p < 0.05). DASH score, aesthetic and general satisfaction were similar for both groups (p = n.s.).

Conclusions: Surgical intervention leads to better clinical and radiological outcomes compared to conservative treatment, reducing the risk of developing scapular dyskinesis, nonunion and mal union. While conservative treatment leads to satisfactory results and can be proposed to patients with lower functional demand or higher surgical risk, surgery provides the best results for the treatment of midshaft clavicle fractures.

Introduction: Clavicle fractures represent up to 10% of all fractures, affecting mainly a young population. Open reduction and internal plate fixation provide good results, but evidence on the best plate positioning is still unclear. Aim of this study was compare superior and antero-inferior plating positioning in the surgical treatment of displaced midshaft clavicle fractures.
Methods: Patients aged >18 years, treated surgically with plate fixation for a midshaft clavicle fracture from January 2010 to April 2021 were included. Shoulder function was evaluated with the use of Constant-Murley Score (CMS) and Disabilities of the Arm, Shoulder, and Hand (DASH) score. Return to sport, aesthetic satisfaction, operative time, radiological outcomes, rate of implant removal, and overall patient satisfaction were documented as well.
Results: 104 patients (51 superior, 53 antero-inferior plating) were included. At the time of the visit, mean follow-up time was 6.7±2.6 years. Mean CMS was 94.1±10.0 points in the superior plating group and 93.4±11.6 points in the antero-inferior plating group. DASH score: 4.6±11.0 superior, 5.1±10.5 antero-inferior. Return to sport: 8.2±2.9 superior, 8.2±3.0 antero-inferior. Aesthetic satisfaction: 8.9±1.6 superior, 8.8±2.1 antero-inferior. Overall satisfaction: 9.1±1.5 superior, 8.9±1.7 antero-inferior. The comparison between groups showed no statistically significant differences (p=n.s.) for all outcome measures. Operative time: 101.6±27.3 minutes superior, 113.0±31.6 minutes antero-inferior (p=0.05). Radiological follow-up documented one non-union and one mal-union in the antero-inferior plating group. Overall, 63 patients underwent plate removal: 58.8% in the superior plating group and 62.3% in the antero-inferior plating group (p=n.s.). Main reason for plate removal was pain/discomfort.
Conclusions: Both superior and antero-inferior plating provided excellent clinical, functional, and radiological results for the treatment of displaced midshaft clavicle fractures, without significant differences among groups. The superior plating group showed a statistically shorter operative time. High rate of re-interventions with implant removal was documented in both groups.

Introduction: Proximal humerus fractures are among the most common fractures in the geriatric population, associated with substantial morbidity, mortality, and economic burden. However, little is known about their economic impact on the working-age population. This retrospective study aimed to investigate the economic burden of proximal humerus fractures in the working population, stratified by age, sex, and occupational class.

Methods: Data were extracted from the SUVA register of professionally active patients with proximal humerus fractures between 2014 and 2022. All patients diagnosed with a proximal humerus fracture, as indicated by the ICD-10 WHO code S42.2, were included. Patients with incomplete data and less than 2 years follow-up were excluded. Patients were categorized by age (15-24, 25-34, 35-44, 45-54, 55-64), sex, and occupation using the ISCO classification according to the International Labour Organization. Return-to-work rates were assessed at 1, 3, 6 months, and 1, 2, 5 years post-trauma. The cost-weight is presented in Swiss francs (CHF).

Results: A total of 29'886 proximal humerus fractures were identified, predominantly in males (male-to-female ratio: 1.5:1). The 45-54 age group was most frequently affected, followed by the 55-64 age group. Occupational groups 2-4 (i.e. professionals, technicians and office workers) had the highest occurance. Group 8 (i.e. machine operators) incurred the highest cost weight (17'131 ± 45'089 CHF). Return-to-work rates were lower in the 55-64 age group, with only 80.5% returning to full employment compared to 92% in the 15-24 age group. Consequently, the cost-weight was significantly higher in the 55-64 age group.

Conclusion: Proximal humerus fractures impose a substantial economic burden on the working-age population, with significant variations by age, sex, and occupational class. Strategies to mitigate this burden should target high-risk groups, particularly older workers, to enhance return-to-work rates and reduce economic costs.

Importance
Internationally, the optimal treatment strategy of proximal humerus fractures remains much debated.

Objective
To investigate whether operative treatment of displaced proximal humerus fractures is superior to nonoperative treatment.

Design
A prospective natural experiment (prospective cohort study) based on geographical randomization and clinical equipoise.

Setting
An international multicenter cohort study in the Netherlands and Switzerland
Participants In total 226 patients with acute (< 3 weeks) displaced proximal humerus fractures presenting from July 2020 until March 2022 were included after expert panel evaluation based on clinical equipoise. Patients were followed up for one year, and 191 (84%) had complete follow-up data.

Interventions
Operative treatment included plate fixation, intramedullary nailing and reverse shoulder arthroplasty at the discretion of the treating surgeon. Nonoperative treatment was sling immobilization. All patients received standardized outpatient rehabilitation and physiotherapy.

Main outcomes and measures
The primary outcome was QuickDASH after one year. Secondary outcomes included QuickDASH at six weeks and EuroQoL5D (EQ5D), Subjective shoulder value (SSV), numeric rating scale for pain (NRS) at six weeks and one year.

Results
No difference in QuickDASH score after one year (16.3 vs. 17.5, p = 0.836) was found. At six weeks, operative treatment resulted in lower NRS (4.2 vs 3.0, p < 0.001), higher EQ5D (0.59 vs. 0.68, p = 0.015) and higher SSV (41.8 vs. 53.6, p=0.002). At one year operative treatment resulted in higher SSV (70.9 vs. 83.5, p < 0.001). Increase in SSV was similar between groups (29.1 vs. 29.9, p = 0.234) and EQ5D was comparable after one year (0.87 vs. 0.86, p = 0.980).

Conclusion and relevance
No differences were observed in functional outcomes after one year. However, operative treatment resulted in lower NRS and higher EQ5D at six weeks. The SSV was better for the operative group at both six weeks and one year. Therefore, operative treatment might be beneficial in the short term for selected patients.

Introduction
Reverse total shoulder arthroplasty (RTSA) is a well-established treatment option for complex proximal humerus fractures in elderly patients.
One important factor for good clinical outcomes is the healing of the greater tuberosity (GT). The purpose of this study was to compare the outcomes of patients receiving GT refixation with a so-called “cow hitch” (CH) suture cerclage fixation or with the recommended standard suture cerclage fixation technique at a minimum follow-up of 2 years.

Methods
A retrospective case-control study was performed with 20 patients who underwent RTSA with CH fixation of the GT compared to a control group including 51 patients after RTSA with the recommended standard suture cerclage fixation of the GT for the tested implant.
Radiological healing of the GT was defined as the primary outcome parameter and was assessed with standard radiographs at last follow up visit. Clinical outcome was assessed as the secondary outcome parameter and was measured with the absolute and relative Constant-Murley score (aCS and rCS), subjective shoulder value (SSV), range-of-motion (ROM) assessment and patient’s reported outcome satisfaction (PROM).

Results
The mean follow-up duration was 37 ± 16 months in the CH group and 35 ± 15 months in the control group (P = .95). The radiographic findings revealed a 95% healing rate of the GT in the CH group compared to 75% healing rate in the control group (P = .09). No secondary displacement of the GT was observed in the CH group compared to 8 cases (15%) in the control group (P = .1).

At the latest follow-up, the aCS was significantly higher in the CH group than in the control group (68 ± 12 points vs 62 ± 14 points) (P = .04). The rCS and SSV was comparable between the two groups (82 ± 13 % vs 82 ± 18% (P = .06) and 86 ± 11 % vs. 83 ± 18% (P = 1), respectively). The CH group showed significantly better external rotation compared to the control group (31 ± 15° vs 18 ± 16°) (P = .01). No significant differences were observed for flexion and abduction. PROMs were comparable between the two groups.

Conclusion
The use of CH suture cerclage for refixation of the GT in RTSA following complex proximal humerus fractures was noninferior to the standard suture cerclage in terms of radiographic outcomes and PROMs but showed better external rotation.

Fracture sequelae after failed operative treatment of proximal humerus fractures represents a very complex pathology of the shoulder joint and is often associated with adverse events and complications due to osseous defects, rotator cuff deficiency, numerous previous surgeries and stiffness. However, RSA is often the only therapeutic option left to improve patient satisfaction. Glenoid lateralization may improve pretensioning of the deltoid muscle and the residual rotator cuff and reduce scapular notching.
Aim of this study was to evaluate complications as well as clinical and radiological results of RSA fracture sequelae situations.

This retrospective study from prospective data included patients who underwent RSA after failed operative treatment of a proximal humerus fracture. Inclusion criteria was previous reconstructive surgical treatment and secondary RSA implantation with or without metallic glenoid augmentation at one of two institutions with a minimum two year follow-up examination. All adverse events were recorded in addition to Constant Score (CS) and Subjective Shoulder Value (SSV) and range of motion, as well as radiographic evaluation was included.

52 patients treated with RSA for fracture sequelae (female n=32, male n=20; Ø=66 years) were included. Adverse events resp. complications occurred in seven patients (reversible axillary palsy, instability, periprosthetic fracture, glenoid loosening), resulting in a complication rate of 13%, of which four (8%) led to revision). 16 patients were treated with metallic glenoid augmentation of the baseplate.
All patients treated for fracture sequelae improved statistically significant in CS, SSV (p < 0.01) and all planes of range of motion (p < 0.05) compared to baseline function.
Patients with glenoid lateralization showed superior flexion (p=0.04), abduction (p=0.03), external rotation (p=0.03) and significant lower rates of scapular notching (0% vs 16%).

RSA provides reliable clinical and radiographic results as a treatment option for patients with fracture sequelae. Since the rate of adverse events resp. complication leading to revision are similar in lateralized and non-lateralized designs we continue to use metallic glenoid augmentation in this specific patient cohort due to superior functionality after RSA.

ABSTRACT:
Introduction: Reverse shoulder arthroplasty (RSA) is becoming an increasingly common surgical treatment option for elderly patients with proximal humerus fractures. Given the high rate of osteoporotic fractures and the increased risk of intraoperative fractures and/or postoperative loosening of the stem in this patient population, the use of cement is the standard of care. However, the use of cement has been associated with some risks. We analyzed clinical and radiological data two years postoperatively in patients treated with uncemented humeral stems.
Methods: From January 2019 to February 2022, 133 proximal humerus fractures underwent RSA at our institution. In total, 54 shoulders (52 patients) were treated with the same uncemented system (Global Unite Reverse Fracture, DePuy Synthes, Warsaw, IN, USA) and tubercula refixation method. Clinical (e.g., range of motion, Constant Score - CS, American Shoulder and Elbow Score - ASES and subjective shoulder valued - SSV) and radiological (e.g., ingrowth of the tubercula, osteoporosis, stem loosening, notching) parameters were assessed two years after surgery. In addition to describing the entire cohort, we compared patient groups according to the pathologic deltoid tuberosity index (DTI).

Results: The mean age was 78.6 years (±8; range 61-95), 87% were female, and 69% were osteoporotic fractures. At the two-year follow-up, the median SSV was 90% (IQR 80-95), the median CS was 76.5 (IQR 72-81), and the median ASES was 89.9 (IQR 82-93). The median active forward flexion reached 140° (IQR120-160), the mean external rotation 30° (IQR 20-30), and the median active internal rotation was 6 (IQR 4-8) points. The greater tuberosity (GT) healing rate was 94.5%. Although the osteoporotic fractures occurred more often in older patients (mean 81 vs. 72 years), there was no significant difference in clinical outcomes between the osteoporotic and non-osteoporotic fractures. However, there was one case of aseptic stem loosening in the osteoporotic group.
Conclusion: Even in osteoporotic fractures, the use of the cementless stems to treat patients with proximal humerus fractures is a valuable option and is not associated with a higher complication rate. The reattachment technique of GT resulted in a high rate of ingrowth two years postoperatively.

Background: Glenoid component loosening remains a challenge in anatomic total shoulder arthroplasty (aTSA). This study evaluates the longevity of aTSA using the Eclipse humeral component and cemented polyethylene pegged glenoid (Arthrex, Naples, FL, USA), comparing outcomes and complications in primary versus secondary osteoarthritis.
Methods: 211 cases of stemless aTSA with a pegged glenoid were enrolled in our local registry. Between 01/2011 and 12/2016, 197 individuals who underwent primary aTSA using the described components were retrospectively evaluated grouped into primary (G1) or secondary osteoarthritis (G2), 14 patients treated for other conditions than osteoarthritis were excluded. Clinical and radiological assessments were conducted 2,5, and 10 years postoperatively or if the patient has presented himself due to complaints, including: Constant Score, DASH, SPADI, SSV, EQ-5D-5L ,Walch Classification, Critical Shoulder Angle, Lateral Acromion Index, Glenohumeral Distance, Glenoid Cementation, Component Loosening. We compared complications, revision rates and survival rates between groups.
Results: G1 (n=153) and G2 (n=44) had follow-up durations averaging 74.2±29.9 and 77.2±28.2 months (p=0.54). G1, older at inclusion (67±8 years) compared to G2 (59±10 years, p < 0.001), demonstrated a revision rate of 50%, as opposed to 55% in G2. G1 exhibited longer mean survival (77±30 months vs. 66±23 months, p=0.015). No significant differences were found between titanium coated vs standard humeral components in terms of survival rates (p=0.76). Key revision causes were glenoid loosening (G1:n=65;G2:n=21), periprosthetic fractures (G1:n=7;G2:n=2), and low-grade infections (G1:n=2;G2: n=1). Preoperative functional scores (Constant Score:G1=36±16,G2=34±17; qDASH, SPADI: both groups 42±20, 42±23 respectively) and radiologic parameters (CSA,LAI) were similar across groups. Operative time was shorter for Group 1 (99±22 minutes vs. 109±23 minutes, p=0.016). Postoperative radiologic and clinical assessments at 2, and 5 years revealed no significant differences (p > 0.05) in non-revised patients.
Conclusion: Both groups demonstrated alarmingly high revision rates with comparable follow-up. Primary osteoarthritis patients showed longer mean survival despite being older. Glenoid loosening was the predominant revision cause, underscoring the need for further research into glenoid failure mechanisms to enhance patient outcomes and implant longevity.

Introduction: Reverse shoulder arthroplasty (RSA) is widely considered the standard treatment for the majority of patients with cuff tear arthropathy, but cases with a combined loss of active elevation and external rotation (CLEER) due to insufficient infraspinatus and teres minor muscles are challenging. Since RSA alone may not adequately restore external rotation, a modified L’Episcopo procedure (latissimus dorsi and teres major transfer) may be advantageous. Our study aimed to assess patient outcomes after RSA and a modified L’Episcopo tendon transfer.

Methods: 21 consecutive patients undergoing RSA (Delta XtendTM, DePuy Synthes, Warsaw, IN, USA) with a modified L’Episcopo between January 2017 and January 2022 were prospectively enrolled. Standardized implantation and tendon transfer techniques were performed through a single deltopectoral approach. Demographic information and pre- and postoperative (2-year) clinical and radiological data including the range of motion, Constant Murley Score (CS), Subjective Shoulder Value (SSV), American Shoulder and Elbow Score (ASES), complications, and reoperations were collected. Pre- and postoperative results were compared with paired t-tests and Wilcoxon signed-rank tests.

Results: The mean age was 77 years (±7.2), 76% (16) were female, the mean body mass index was 29.9 kg/m² (±6.8), and 95% (20) were dominant side shoulders. The mean active elevation increased from 58 (±27.6) to 139.5 (±21) degrees (p < 0.0001). Likewise, the median external rotation in abduction (ER2) increased from 0 (IQR 0-10) to 75 (IQR 70-80) degrees (p < 0.0001), and the mean external rotation in the neutral position (ER1) increased from -4.1 (±9.6) to 11.2 (±12.2) degrees (p < 0.0001). Internal rotation decreased significantly from 5.0 (±1.2) to 3.8 (±1.8) points (p=0.034). The mean pre- and postoperative CS (22.6 ±8.3 to 72.6 ±8.4 (p < 0.0001)), ASES (32 ±9.9 to 88 ±5.5 (p < 0.0001)), and the SSV (25 ±13 to 83.8 ±9.3 (p < 0.0001)) improved significantly. No reoperation was required, but in one patient the tendon transfer did not heal.

Conclusion: Our findings showed that RSA combined with a modified L’Episcopo effectively restores active external rotation and abduction in patients with CLEER. Most clinical and radiological long-term outcomes were satisfactory, while the complication rate was relatively low (4.8%). Due to the surgically altered ratio of internal to external rotators, mean internal rotation decreased.

Recent results confirm the trend towards lateralizing arthroplasty designs in reverse shoulder arthroplasty (RSA). Aim of this study was to evaluate clinical and radiological mid-term outcomes of bipolar lateralization (metallic vs. bony augmentation) with isolated humeral lateralization (Lat.) in patients with cuff arthropathy (CTA) and osteoarthritis (OA).

Patients who underwent RSA between 05/2013 and 08/2019 with CTA or OA in one of two orthopaedic institutions were included. All received a curved 145° onlay stem system for humeral lateralization and were divided into 3 groups based on glenoid lateralization: no glenoid lat. (A), metallic augmentation (B) and bony-increased offset (BIO-RSA, C). Clinical evaluation included Constant Score (CS), Subjective Shoulder Value (SSV) and range of motion. Fractures, instabilities or loosening, scapular notching, stress shielding, osteolysis and other complications were examined radiologically.

A total of 80 patients (CTA: n=58; OA: n=32) were examined after an average of 73 (48-120) months. They achieved a CS of 71 (23-94) points, a SSV of 83% (10-100) with following range of motion: flexion 144° (50-180), abduction 143° (45-180), external rotation 25° (0-75), internal rotation in CS points 6.3 (0-10). Patients with OA showed significantly better clinical function regarding CS (78 vs. 69 p.; p=0.02), abduction (157 vs. 138 °; p=0.01), flexion (156 vs. 140 °; p=0.01), internal rotation (7.3 vs. 5.8 CS points; p=0.07) and had greater abduction strength compared to CTA patients (5.3 vs. 4.0 kg; p=0.04). There were no significant differences within groups A (n=26; mean 80.0 years), B (n=38; mean 79.1 years) and C (n=16; mean 78.5 years) regarding CS (A: 71, B: 73, C: 68 points), SSV (A: 82, B: 82, C: 85%) or range of motion. Metallic lat. showed a reduced rate of scapular notching (A: 42%, B: 18%, C: 31%; p=0.08). 57 patients (59%) showed radiologic stress shielding. 23 patients (29%) showed osteolysis in the humeral metaphysis. These radiologic changes had no influence on clinical function. No fractures, instabilities or loosening were detected in any of the three groups.

Humeral lat. using a curved 145° onlay stem achieves excellent clinical results in primary reverse shoulder arthroplasty (with or without additional glenoid lat.). Patients with OA show superior outcome at mid-term FU patients compared to CTA patients. Metallic lat. has a positive influence on reducing rates of scapular notching.

Einleitung
Zementierte, anatomische Schultertotalendoprothesen mit gekielter PE-Glenoidkomponente weisen im mittleren bis langfristigen Nachuntersuchungszeitraum „radiolucent lines“ (RLL) in über 50% der Fälle auf mit ebenfalls hohen Lockerungsraten. Ziel dieser Studie war es, die langfristigen Ergebnisse einer standardisierten knochensparenden und voll verteilten Zementiertechnik inkl. in Hinblick auf die RLL und klinischen Outcomes der Patienten zu beurteilen.

Material und Methodik
Dazu wurde eine retrospektive Kohortenstudie mit 38 konsekutiven Patienten (w=20; m= 18), welche in Folge einer primären Omarthrose mittels einer anatomisch schaftlosen Schultertotalendoprothese mit u.g. Zementiertechnik versorgt wurden, durchgeführt. Das durchschnittliche Alter bei der Operation betrug 66 (± 9,7) Jahre. Die Zementiertechnik wurde wie folgt durchgeführt:
1) Fräsung unter Erhalt des subchondralen Knochens
2) Spongiosaverdichtung des Kielbetts
3) Glenoidale K-Draht Bohrungen zur Zementverankerung
4) Ausgiebige Lavage
5) Ossäre Hämostase (Applikation lokaler Vasokonstriktoren)
6) Vollbeschichtete Zementapplikation der PE Rückfläche inklusive des Kiels
6) Fünfzehnminütige manuelle Kompression auf das Implantat

Zusätzlich erfolgte die standardisierte, dynamische Impingmenttestung der Probe-Glenoidkomponente um die implantierte Humeruskopfkomponente (Nyffeler-Test).

Radiologisch wurden die RLL um die glenoidale Komponente evaluiert. Klinisch wurde der Constant-Score (CS) und Subjektiver Schulterwert (SSV) erhoben.

Ergebnisse:
Insgesamt konnten 21 (w=11; m=10) Schultertotalendoprothesen mit einem durchschnittlichen Alter von 76 (±10,5) Jahren nachuntersucht werden. Der durchschnittliche Nachuntersuchungszeitraum betrug 9,2 (7-13) Jahre. RLL zeigten sich bei 8 Schultern (38%) um die glenoidale Komponente. Der durchschnittliche RLL-Score lag bei 0,95 (0-3). Der durchschnittliche Constant-Score lag bei 75,4 Punkten und der durchschnittliche SSV lag bei 80%. Insgesamt wurden vier Patienten aus der Patientenkohorte revidiert, resultierend in einer mittleren Überlebenszeit von 85,9% nach 97 Monaten.

Diskussion:
Die standardisierte Zementiertechnik gekielter, anatomischer Schultertotalendoprothesen unter Verwendung des Nyffeler Tests zeigt im Vgl. zur Literatur geringere Raten an RLL und exzellente klinische Langzeitergebnisse mit hoher Überlebensrate.

Introduction: We aim to study the outcomes of the anatomic total shoulder arthroplasty in B2 glenoids both before and after the 2012 publication by Walch et al. that recommended the use of reverse total shoulder arthroplasty (rTSA) for Walch Type B2 glenohumeral joint arthritis.

Methods: Using PRISMA guidelines, publications were identified that reported the outcomes for anatomic total shoulder arthroplasty used to manage the B2 glenoid. Only studies with minimal 2 years of follow-up were considered.

Results: In our two groups, pre-2012 and post-2012, we have 774 osteoarthritic B2 shoulders that were treated with an anatomic shoulder arthroplasty. The average follow-up was 64.2 versus 48.27 months. Over the last 10 years, prosthesis-related complication rates using eccentric reaming have significantly decreased from 13.77% to 3.28% (odds-ratio: 3.5; p-value: 0.0002; CI: 1.49-8.64). The use of posterior augmented glenoid implants has increased substantially and has maintained a consistently low complication rate of 2.8% (odds-ratio: 0.64; p-value: 0.684, CI: 0.12 - 3.25) with a mean follow-up of 32.7 months. When combining all surgical options for aTSA in the presence of a B2 glenoid, the results showed that patients after 2012 had significantly lower revision rates than patients before 2012 (odds-ratio: 3.12; p-value: 0.0012 CI: 1.56 - 6.1). In the first group, after the implantation of 166 prostheses, 16 complications occurred (9.6%). While in the 2 groups, 26 complications occurred after 608 operations (4.2%).

Conclusions: Anatomic total shoulder arthroplasty (aTSA) outcomes since 2012 have improved with lower prothesis-related complication rates when eccentric reaming and posterior augmented glenoid components were used.

Aim
The aim of this study was to compare the accuracy of glenoid component implantation in consecutive series of patients undergoing reverse shoulder arthroplasty with and without navigation, according to the wear patterns of the glenoid.

Background
Indications for reverse shoulder arthroplasty (RSA) have increased over the years and seems to yield satisfactory functional results even in patients with severe glenoid wear. New technologies such as navigation have gained in popularity with the aim to increase implantation precision, which is a crucial factor for long term implant survivorship. However, these technologies remain costly and their widespread use for everyday cases has yet to be determined.

Methods
Two consecutive series of patients operated on by the same shoulder surgeon for RSA, with and without navigation using the NextAR system (Medacta, Castel San Pietro, Switzerland), were prospectively included in the study. Revision procedures or RSA requiring glenoid bone graft were not included. Patients demographics (age, sex, side, BMI), preoperative diagnosis and glenoid wear patterns in both the coronal and axial planes were analyzed and defined as mild and severe. Postoperative implantation accuracy measurements were carried out on postoperative CT scans and consisted in RSA angle, version, maximal bone purchase of peripheral screws and central peg, and glenosphere position from the inferior glenoid neck according to Nyffeler.

Results
56 shoulders were included, 28 in each group. There were no significant differences in patient demographics, preoperative diagnosis, and wear pattern severity between both groups. In the navigated group, patients with severe bone wear presented a significantly higher accuracy in all analysed parameters, whereas patients with mild glenoid defects did not show significant differences in glenoid implantation version and glenosphere position from the inferior glenoid neck.

Conclusion
Navigation significantly improves glenoid implantation accuracy, particularly in patients with severe glenoid wear patterns. While its applicability in standard cases is debatable for experienced shoulder surgeons, it could prove valuable for patients with severe bone defects. Further studies are needed to assess if this will impact clinical and long-term implant survival outcomes.

Introduction: Positioning of glenoid component in reverse total shoulder arthroplasty (RTSA) may impact procedure’s safety and efficacy. Bony increased offset technique adds a level of complexity to the glenoid component positioning process. Optimisation of final passive soft tissue tensions have been reported to be determinant of postoperative joint stability as well as potential complications such as acromial/glenoid neck fractures and nerve traction injuries. In parallel, optimisation of impingement-free ranges of motion represents a key determinant of the procedure’s efficacy. Three-dimensional planning combined with intraoperative navigation emerges as a technical development for intraoperative surgeon assistance. Primary objective of this study was the evaluation of 3D preoperative planning fidelity during the intraoperative phase using navigation. Secondary objective was the analysis of functional outcomes of the procedure.

Methods: A sequential cohort of 100 primary RTSA was prospectively analysed. Preoperative glenoid component planning data and intraoperative navigation data before screw insertion were recorded. Advanced functional assessment of the shoulder using 3D motion capture was acquired preoperatively and at 1 year postoperatively.

Results: Difference in glenoid component positioning (mean ± SD) compared to preoperative 3D planning was 0.93 ± 3.13 mm for superior inclination, -0.69 ± 3.23 mm for retroversion, and -6.99 ± 3.17 mm for depth. Range of motion (mean ± SD) in forward elevation increased from 87.31 ± 35.30° to 116.19 ± 30.73° with a calculated difference of 28.88 ± 32.62°. Auto-evaluated pain on a scale of ten decreased from (mean ± SD) 4.25 ± 2.70 to 1.31 ± 2.16 with a calculated difference of -2.94 ± 2.85.

Conclusions and perspectives: Three-dimensional planning associated with navigation allows for accuracy of bony increased offset glenoid component positioning below 1° error in inclination and retroversion. Accuracy in depth positioning before tightening of screws remained over 5 mm. Further studies concerning depth are required with tools allowing for implant position recording after screw insertion. Functional outcome measurements showed satisfactory improvements in ranges of motion as well as diminution of pain. Further comparative studies between 3D planning associated with intraoperative navigation and 3D planning alone are underway.

Background:
Preoperative planning software enables the evaluation of various implant configurations and positions for reverse total shoulder arthroplasty (RTSA), with the objective to achieve stable fixation and maximal theoretical range of motion (ROM). However, it has been shown that simulated ROM without posture adjustment does not correlate well with postoperative ROM. The objective of this study was to compare simulated range of motion (ROM) for RTSA with and without adjustment for scapulothoracic orientation in a global reference system. We hypothesized that values for simulated ROM in a preoperative planning software with and without adjustment for scapulothoracic orientation would be significantly different.

Methods:
A statistical shape model of the entire humerus and scapula was fitted into 10 shoulder CT scans randomly selected from 162 patients who underwent RTSA. Six shoulder surgeons independently planned an RTSA in each model using a prototype development software with the ability to adjust for scapulothoracic orientation, starting position of the humerus, as well as kinematic planes in a global reference system simulating previously described posture types A, B, and C. ROM with and without posture adjustment was calculated for a total of 240 different case-scenarios and compared in all movement planes.

Results:
All movement planes showed significant differences when comparing protocols with and without adjustment for posture. The largest mean difference was seen in external rotation with 62° without adjustment compared to 25° with posture adjustment (p < 0.001), with the highest mean difference of 49° in type C. Extension was 57° without adjustment versus 24° with adjustment (p < 0.001) and the highest mean difference of 47° in type C. Abducted internal rotation was 69° without adjustment versus 31° with posture adjustment (p < 0.001), showing the highest mean difference of 51° in type C.

Conclusion:
The present study demonstrates that accounting for scapulothoracic orientation has a significant impact on simulated ROM for RTSA in all motion planes, particularly rendering vastly lower values for external rotation, extension, and high internal rotation. The substantial differences observed in this study warrant a critical reevaluation of all previously published studies that examined component choice and placement for optimized ROM in RTSA using conventional preoperative planning software.

Purpose:
This study aimed to evaluate whether shoulder functional internal rotation (fIR) after reverse shoulder arthroplasty (RSA) differs according to the size of implanted glenosphere.
Patients and Methods:
We retrospectively reviewed patients who had RSA between September 2015 and September 2020; 222 patients were eligible for inclusion and were operated upon by a single surgeon using a single implant. 132 (59.4%) were females, and the mean patients' age was 72±8 years. A 36 mm glenosphere was implanted in 109 patients (49%) and 39 mm glenosphere in 113 patients (51%). Clinical evaluation was performed using Simple shoulder value (SSV) and Constant score. The functional internal rotation (fRI) was evaluated and classified into type I if the hand blocked to the buttock, type II lumbar sliding, and type III smooth motion. Where type I was considered nonfunctional and type II and III as fRI.
Results:
After a mean follow-up of 24.7±4.1 months, the mean overall Constant score improved significantly from 42.81±15.25 points preoperatively to 73.44±11.80 points at the last follow-up (P < 0.001). The SSV improved significantly from 43.61±16.68 to 79.68±13.17 (P < 0.001). The fIR was classified preoperatively as type I in 57 (25.6%) patients, type II in 106 (47.7%), and type III in 59 (26.5%), which changed at the last follow-up to type I in 64 (28.8%) patients, type II in 80 (36%), and type III in 78 (35.1%). There was a non-significant change (p=0.53) and (p=0.17) in the 36 mm and 39 mm glenosphere, respectively.
Conclusion:
We found that there was no significant impact exists between the different glenosphere sizes and postoperative fRI. Nearly 70% of the patients regain postoperatively a fIR.

Background: Movement limitations after RTSA have been observed in some patients postoperatively, with implant design and positioning recognized as influential factors. Recent analyses have identified three scapular postures in the population that might affect range of movement (ROM). However, no clinical study has explored their impact on clinical outcome so far. It was the aim of this study to correlate patient´s posture with the clinical outcome (including ROM) and further correlate photo documented posture to measurement of scapula position on computed tomography (CT).

Methods: A prospectively enrolled RTSA database was retrospectively reviewed, and 360 consecutive patients met the inclusion criteria at minimum follow-up of 2 years. Patient´s posture was analyzed using photo documentation. The posture was defined following Moroder´s classification as Type A (upright posture, retracted scapulae), type B (intermediate), type C (kyphotic posture with protracted scapulae). CT data were used to measure scapula position (internal rotation). Correlation analyses between them were conducted. Postoperative ROM and clinical outcomes (absolute and relative Constant Score (CSa, CSr)) were compared between the different posture types.

Results: According to the clinical posture type, the patients were divided into posture type A (n=69), B (n=253) and C (n=48). Average CSa differed significantly among groups (69±16 vs 69±14 vs 64±16, p < 0.05) favoring patients with posture types A and B over type C. In terms of ROM, flexion, abduction and internal rotation significantly differed among groups. Types A and B exhibited better flexion and abduction (flexion 124±26º and 123±23º vs. 113±25º, abduction 140±34º and 137±30º vs 128±34º). Patients with posture type A demonstrated superior internal rotation (5.86±2.94 vs 5.00±2.68 vs 4.38±2.79, p < 0.05). External rotation was similar between the groups (33 ± 17° vs 30 ± 16° vs 28 ± 18°, p=0.3) but significantly better for type A compared to type C. Correlation analysis between clinical assessment and CT measurement showed very poor reliability (Correlation = 0.35).

Conclusion: Patients with clinical posture types A and B exhibit improved ROM values compared to type C postures. Clinical outcome scores was also notably superior in types A and B. Scapulothoracic orientation should be a crucial consideration in RTSA planning, influencing ROM and clinical outcomes.

Introduction – Three-dimensional (3D) scapula morphology measures on CT are more accurate and precise than standard two-dimensional (2D) measurements. Equivalent 3D scapula morphology measurements on diagnostic MRI are impeded, however, due to the reduced image resolution and field of view which excludes the medical and inferior scapular borders. We hypothesised, that deep-learning based algorithms exploiting high resolution knowledge from CT, could enable automatic 3D scapular morphology analysis on diagnostic MRI, with equivalent accuracy to CT.
Methods - A deep-learning based segmentation network for prediction of the scapula from MRI was trained on CT and MRI data from the same shoulder of 20 rotator cuff tear patients. Manual segmentations from CT were aligned to the corresponding MRI and used to train a deep-learning network to automatically segment the scapular on multiplanar MRI (coronal, sagittal and transverse orientations). An algorithm to combine segmentation information from the three planes to generate high-resolution 3D models from the anisotropic MRI data was also developed. For the automatic calculation of common morphological measures, a second deep-learning network was trained to predict the location of anatomical landmarks and scapular axes on the 3D scapula models. Differences between morphology metrics automatically calculated on MRI and on corresponding CT were evaluated on 10 patients using the paired t-test and the intraclass correlation coefficient (ICC).
Results – Morphological measurements were automatically calculated on MRI, with no statistically significant differences from values calculated on CT (P < 0.05). The ICC between values calculated on CT and MRI were: 0.73 for the glenoid version, 0.81 for the glenoid width, 0.89 for the glenoid height, 0.93 for the glenoid inclination and 0.91 for the critical shoulder angle.
Conclusion – This study presents deep learning-based algorithms for automatic scapular morphology analysis from diagnostic MRI. By training deep-learning networks on higher resolution CT based complete scapular models and by combining the information from different MRI planes, challenges posed by the reduced resolution and restricted FOV of diagnostic MR was overcome. Our approach facilitates the application of accurate 3D scapula morphology analysis on patients with diagnostic MRI, eliminating reliance on CT imaging.

Background: First ray instability is known to be responsible for biomechanical changes in the foot leading to several foot disorders. The diagnosis is crucial to determine the treatment strategy, but tends to be based upon the surgeon’s experience and manual sensitivity. This is due to the lack of a practical and reliable instrument to quantify first ray hypermobility. We present a novel electromechanical tool measuring the relative dorsal mobility of the first ray (FRRM) compared with the one of lateral rays, by simulating ground reaction forces during gait. The aim of the study is to assess the intra- and inter-examiners reliabilities of the measurements obtained with this device.



Methods: The protocol includes 2 examiners assessing 22 feet of 11 volunteers (healthy with no history of foot disorder). This device equally applies a standardized, electronically controlled, and precise force under the first metatarsal head M1 as well as under the heads of the lesser metatarsals M2 to M5. The device is equipped with an adjustable heel support based on the patient's foot size. An automated adjustment of the two bearings supporting M1 and M2 to M5 in the transverse plane is performed by two optical sensors. The relative dorsal mobility between these two bearings is then measured as a function of the applied force, ranging from 0 up to 100N. 15 measurements were performed on each foot (3 sets of 5 trials) in order to assess inter- and intra-observer reliability. For this purpose, the interclass correlation coefficient (ICC), the error of measurement (SEM) and the Bland and Altman (B&A) graphical analysis were computed.



Results: Excellent ICC values (≥0.93) were obtained with the novel device for inter-rater (ICC = 0.96, IC95 [0.90-0.98]) and intra-rater reliability (ICC= 0.96, IC95 [0.91-0.99]) when using the FRRM calculation. The mean FRRM values are 5.89±2.34 (mm). The B&A analysis presented a bias between examiners of only −0.12 mm ranging from −0.54 to 0.29 mm.



Conclusion: This study demonstrates the capacity of this device to reliably measure the relative dorsal mobility of the first ray compared with the mobility of lateral rays. It is thus proven to be a reliable tool for proceeding with further studies to define the hypermobility of the first ray more scientifically.

Introduction: Weightbearing computed tomography (WBCT) scans allow for a better understanding of foot alignment in patients suffering from flatfoot deformity (FFD). However, soft tissue integrity (e.g., spring ligament complex or tibialis posterior tendon) cannot be easily assessed via WBCT. As performing both WBCT and magnetic resonance imaging (MRI) might not be cost effective, we aimed to assess whether there is an association between osseous and soft tissue findings in WBCT and MRI.

Methods: In this observational study, a consecutive cohort of 24 patients of various stages of FFD (mean age 51±18 years) underwent WBCT scans and MRI. 24 healthy individuals of similar age, body mass index (BMI) and sex with WBCT scans were used as a control group. In addition to osseous sinus tarsi impingement, four commonly used 3-dimensional (3D) measurements (talo-calcaneal overlap, TCO; talo-navicular coverage, TNC; Meary's angle, MA, axial/lateral) were obtained using a dedicated post processing software (DISIOR 2.1, Finland) on the WBCT datasets. Sinus tarsi obliteration, spring ligament complex, tibiospring ligament integrity, as well as tibialis posterior tendon degeneration were evaluated with MRI. Statistical analysis was performed for significant (P < 0.05) correlation between findings.

Results: None of the assessed 3D measurements correlated with either spring ligament complex or tibiospring ligament tears. Age, BMI, and TCO were found to be associated with tibialis posterior tendon tears. 75 % of patients with sinus tarsi impingement on WBCT also showed signs of sinus tarsi obliteration on MRI. Of the assessed parameters, only age and BMI were associated with sinus tarsi obliteration diagnosed on MRI, while the assessed WBCT based 3D measurements were, with the exception of MA axial, associated with sinus tarsi impingement.

Conclusion: The relationship between WBCT based 3D measurements and soft tissue impairment assessed via MRI is limited. Perhaps not surprisingly, we found partial or complete rupture of the tibialis posterior tendon more likely to occur in comparably older and overweight PCFD patients with an increased TCO. WBCT may not replace MRI and MRI does not replace WBCT regarding their diagnostic value. Both imaging options add different but important information possibly affecting decision-making in the treatment of FFD patients.

Introduction
Knowledge about articular joint mechanics can provide information about altered joint function and potential pathological mechanisms. In silico computational musculoskeletal simulations allow to estimate such contact parameters that cannot be feasibly measured in vivo. To gain insights into articular hindfoot mechanics, the aim of this study was to combine state-of-the-art in vivo 3D motion capture and dynamic in silico musculoskeletal simulations to estimate contact area and pressure of the ankle and subtalar joint in healthy subjects during activities of daily living.

Methods
9 healthy subjects (23±3 years; 23.1±2.0 kg/m2) with no history of foot-ankle injuries were assessed during repeated trials of level walking, stair ascent, and stair descent using a whole body skin-marker set (Boey et al, 2022). Articular joint mechanics were estimated using an extended foot-ankle OpenSim model (Malaquias et al., 2017), with incorporated cartilage geometries of the tibia, talus, and calcaneus. Generic models were scaled for each individual and kinematics calculated for every trial. Marker-based kinematics were then used to estimate articular joint mechanics of the ankle and subtalar joint using the OpenSim joint articular mechanics tool (Smith et al. 2018, Postolka et al. in review).

Results
Throughout the loaded stance phase of all three activities of daily living, mean contact pressures were higher at the ankle (average 2.35-2.93MPa) than at the subtalar joint (average 1.23-1.35MPa). Overall largest contact pressures were found at the ankle joint during stair ascent with peak pressures of 13.7+/-9.2MPa. For the ankle joint, both, contact area and pressure were correlated with ankle plantar/dorsiflexion. For the subtalar joint, however, almost no variations in contact area and pressure were found throughout the three activities of daily living.

Conclusion
By combining a musculoskeletal foot-ankle and contact model, this study provided estimations of articular ankle and subtalar joint contact area and pressure during activities of daily living. This analysis is a first proof-of-concept data set on in vivo articular joint mechanics and can help to gain a more detailed understanding of the relationship between hindfoot motion and loading in healthy individuals.

Acknowledgments
This study was supported by the Swiss National Science Foundation, the Research Foundation Flanders, and the Berghmanns Dereymaeker research Chair on Foot & Ankle Biomechanics.

Objectives: It has been postulated that the screws used in a percutaneous chevron akin procedure should not compress the capital fragment as compression is supposed to change the alignment unfavorably. Not all MIS surgeons have access to these special implants, though. We hypothesize that compression screws are suitable for MICA and can be used without increased risk for hardware failure (loosening, breakage, dislocation), non-union or malalignment.
Material & Methods: Between May 2018 and January 2022, 100 consecutive MICA cases have been performed in a single institution using fully-threaded headless cannulated compression screws (Arthrex FT 4.0 & 3.5mm, Arthrex Inc., Naples /USA). There were 85 female and 15 male patients with a mean age of 53y (range 16-78y). The mean preoperative intermetatarsal angle I/II (IMA) was 15.7°, the mean hallux valgus angle (HVA) 28.7° and the mean distal metatarsal arctiulation angle (DMAA) was 9.4°. All cases were followed at 6 & 12 weeks and 6, 12 & 24 months postop regarding radiologcial correction and surgery-asscoiated comp-lications using a modified Clavien-Dindo classification (CDC).Results: The average amount of radiological correction was 12.6° for IMA and 16.8° for HVA. DMAA was not negatively influenced by the compression screws but improved from a preop mean of 9.4° to 5.5° at latest f/u. Overall, there were four CDC type I complications (oral antibiotics), four type II complications (1x symptomatic osteotomy site displacement, 1x delayed union, 2x transfer metatarsalgia), 23 type III complications consisting of 22x secondary screw removals and 1x superficial wound debridement. All hardware removals were related to the square-headed design. There were no cases of hardware failure requiring revision surgery (no screw loosening, breakage or dislocation).Conclusion: Compression screws are well suited for MICA and provide excellent control of alignment and permanent stabilization. Our surgical technique of 3rd generation MICA is characterized by positioning the distal screw, which crosses the osteotomy site centrally and grasps the MT1 head medially, first. This can help not only to secure but also to improve DMAA.
Compared to bevel-headed screws, a square-headed screw design demonstrated a higher rate of secondary hardware removal due to discomfort at the prominent screw heads. Therefore, the use of bevel-headed screws is strongly recommended, regardless of whether they are compression screws or non-compression.

Introduction
About 10% of malleolar fractures are associated with an injury of the syndesmosis. Syndesmotic compromise is even higher in fractures requiring surgical reduction. Fractures classified as Weber type B and C present up to 40% and up to 80% associated syndesmotic lesions, respectively. A compromise of the syndesmotic ligaments can lead to widening in the ankle mortise, inducing ankle instability, increased risk of early osteoarthritis and chronic pain.
Moreover, the best treatment option for lesions of the tibiofibular syndesmosis remains subject to debate. The most used surgical treatment option is a rigid osteosynthesis by cortical screws. Alternative treatment options are flexible such as the suture-button-technique and k-wire fixation. This latter technique was rarely investigated.
Aim of the study is to assess the patient reported outcome in mid-term.
Methods
We performed a retrospective analysis of 20 consecutive patients who underwent surgical treatment in our center for a bi- or trimalleolar fracture with a K-wire syndesmosis fixation by a single surgeon. After fixation of the lateral and medial malleolus an intraoperative external rotation stress was performed. If a widening of the syndesmosis was confirmed two K- wire were inserted from lateral and caudal to medial and proximal with a 60° divergence angle on the frontal plane.
Patients answered a questionnaire on their functional abilities (EFAS, EFAS sport, SF-12scores) and an AP and lateral ankle X-ray were performed.
Results
The average follow-up of the 20 patients (mean age: 48.3; 15 female, 5 male) was 3.42 years. 55% had an initial dislocated fracture. There was a high energy trauma in 50% of the cases. 45% of the patients had an additional posterior malleolar fracture fixation. At follow-up the mean EFAS score was 22.65 / 24, mean EFAS sport 12.45 / 16, the SF-12: mean MCS was 59.10 and the average PCS 55.45. Anatomic reduction of the fracture was achieved in 70%. Hardware removal was performed in 95% of patients. Nevertheless, there was a 10% complication rate. No patient needed ankle arthrodesis or replacement. Progression of ankle osteoarthritis was not observed in any patient. 67% of patients had osteoarthritis Takakura stage I and 33% stage II.
Conclusion & perspectives
K-wire fixation seems to offer a reliable syndesmosis fixation with good mid-term clinical results and patient satisfaction. It should be discussed as a possible treatment option.

Introduction:
While artificial intelligence (AI) powered applications continue to advance rapidly, the existing literature lacks comprehensive studies on the segmentation of all bones within the human foot using AI. Moreover, conventional manual segmentation of foot bone structures is a time-consuming and labor-intensive task. In this study, we propose a novel approach utilizing deep learning models, specifically convolutional neural networks (CNN), to achieve fully automatic segmentation of every bone in foot scans (CT). Our work aims to provide detailed CT sections of the foot bones, offering precise information on fracture types and enhancing visualization of the limb’s architecture. Thanks to a very fast segmentation process compared to traditional methods, the key benefits of our approach include more accurate diagnosis, more precise fracture analysis, better 3D surgical planning, and optimal post-operative assessment. We firmly believe that the development of such a medical tool will significantly enhance foot-related healthcare, supporting healthcare professionals in their daily practice.

Methods:
We manually segmented foot bones from fifty CT scans. Out of these, forty-eight CT scans were utilized for training the CNN-based segmentation models, while the remaining two CT scans served as the evaluation dataset. We assessed the CNN’s performance in segmenting foot bones using the Dice coefficient and Intersection over Union (IoU) metrics.

Results:
The trained models accurately detected foot bones in the two test samples, achieving an average Dice coefficient of 0.97 and an IoU of 0.94.

Conclusion:
The CNN networks exhibited remarkable proficiency in identifying foot bone structures on CT scans, thereby paving the way for automatic, rapid (within seconds), and highly accurate foot bone segmentation.

Research Question: It is currently a significant challenge to produce and label a sufficient amount of ultrasound (US) data on anatomical structures, including bone surfaces and critical elements like nerves, to enable the training of artificial intelligence (AI) models. We aim to leverage co-registration with other imaging modalities, such as computer tomography (CT), magnet resonance imaging (MRI), and optical systems, to investigate whether an AI-enhanced data annotation approach can be facilitated for US without manual annotations. This study lays the groundwork for enhancing real-time bone registration and identifying key anatomical features like peripheral nerves in foot and ankle operations.

Methods: In this prospective study, we analyzed 14 ex-vivo human leg specimens to compile a detailed dataset for future AI algorithm development. Each specimen was fixed to a wooden model with optical tracker installed. We conducted CT and MRI scans and then collected US images of the sural nerve and the lower leg and ankle bone surfaces. We used an optically-tracked pointer during dissection to sample points along the nerve. Further, the annotated and segmented CT and MRI data were registered with the US images to obtain a multi-modal and automated annotation and segmentation. This processed US data is intended for use as training material for the AI algorithm.

Findings: Early results from our dataset reveal precise alignment between CT and US images for bones and high accuracy in detecting nerves. This accuracy of the multi-modal approach highlights the effectiveness in mapping nerve pathways and aligning bone imaging from CT with US data. These achievements are essential for advancing to the next stage of developing automated, machine learning-based detection and segmentation tools.

Conclusion: In the initial phase of our project, we created a comprehensive dataset from MRI/CT scans, US imaging of nerve and bone structures, dissection, and optical tracking of the sural nerve, achieving precise mapping of CT to US images and detailing the spatial relationship between nerves and bones. Our next research phase aims to develop a proof of concept that applies machine learning to automate and improve the diagnostic process, enhancing the detection of critical anatomical structures for better patient outcomes, reducing neuropathic pain post-surgery and improving the efficacy of minimally invasive surgical techniques.

Introduction
Several demographical and clinical risk factors for recurrent ankle instability have been described. The main objective of this study was to investigate the potential influence of morphological characteristics of the ankle joint on the occurrence of recurrent instability and the functional outcomes following a modified Broström-Gould procedure for chronic lateral ankle instability.

Methods
Fifty-eight ankles from 58 patients (28 males and 30 females) undergoing a modified Broström-Gould procedure for chronic lateral ankle instability between January 2014 and July 2021 were available for clinical and radiological evaluation. Based on the preoperative radiographs the following radiographic parameters were measured: talar width (TW), tibial anterior surface angle (TAS), talar height (TH), talar radius (TR), tibiotalar sector (TTS), ankle mortise angle (AMA). The history of recurrent ankle instability and the functional outcome using the Karlsson Score were assessed after a minimum follow-up of 2 years.

Results
Recurrent ankle instability was reported in 14 patients (24%). The TTS was significantly lower in patients with recurrent ankle instability (69.8 degrees vs 79.3 degrees) (P < .00001). The multivariate logistic regression model confirmed the TTS as an independent risk factor for recurrent ankle instability (OR = 1.64) (P = .003). The receiver operating characteristic curve analysis revealed that patients with a TTS lower than 72 degrees (= low-TTS group) had an 82-fold increased risk for recurrent ankle instability (P = .001). The low-TTS group showed a significantly higher rate of recurrent instability (58% vs 8%; P = .0001) and a significantly lower Karlsson score (65 points vs 85 points; P < .00001).

Conclusion
A smaller TTS was found to be an independent risk factor for recurrent ankle instability and led to poorer functional outcomes after a modified Broström-Gould procedure.

Introduction:
Literature trends indicate a generally lower rate of reoperation and revision associated with the fixed-bearing two-component design implant compared to the mobile-bearing three-component design for total ankle arthroplasty (TAA). Coronal deformity is also linked to poorer outcomes following TAA. The aim of this study was to assess the impact of intra-articular coronal deformity (non-concentric ankle arthritis) on both fixed and mobile implant designs. We hypothesized that non-concentric ankle arthritis and mobile bearings would be associated with a higher revision rate.

Methods:
This study retrospectively reviewed 202 patients who underwent TAA with either mobile-bearing or fixed-bearing implants at three centers in Switzerland by two surgeons between 2007 and 2018. Patients who underwent TAA from 2007 to 2013 received the mobile-bearing implant, while those who underwent TAA after November 2012 received the fixed-bearing implant. The primary outcomes were the rates of revision and reoperation within three years following the initial procedure. Reoperation was defined as any additional surgery post-index surgery, excluding revisions. Non-concentric ankles were identified by a talar tilt angle greater than 4 degrees on preoperative X-rays.

Results:
Of the 76 patients who received a mobile-bearing implant, 33 had non-concentric arthritis, and 43 had concentric arthritis. Of the 126 patients who received a fixed-bearing implant, 61 had non-concentric arthritis, and 65 had concentric arthritis. In the mobile-bearing group, 8 patients underwent revision and 9 underwent reoperation. In the fixed-bearing group, 4 patients underwent revision and 10 underwent reoperation. The revision rate was significantly higher (p < 0.05) for the mobile-bearing implant (15.2%) compared to the fixed-bearing implant (0%) in the non-concentric group. In the concentric group, there was no significant difference in revision rates between the fixed-bearing (6.2%) and mobile-bearing designs (7%).

Conclusion:
The study demonstrated that the use of mobile-bearing implants in patients with non-concentric arthritis is associated with a significantly higher revision rate compared to fixed-bearing implants. In patients with concentric arthritis, there was no significant difference in revision rates between the two implant designs. Additionally, the study found no significant difference in the reoperation rates across all groups.

Introduction
Alignment of the lower limb on plain radiographs is routinely assessed in an orthopaedic practice. The axis of the ankle joint is defined by the medial distal tibial angle (MDTA). The MDTA can be determined using the anatomical, mechanical, or surgical (referring to the tibial tuberosity) tibial axis. Several studies have found variations in measuring the medial distal tibial angle (MDTA), raising questions about current methods.
This study evaluated the three different methods to determine the MDTA on whole lower leg radiographs. The hypothesis predicted clinically significant disparities between the three methods and assessed the reliability of whole lower leg radiographs to measure the ankle joint axis.

Methods
43 eligible patients were recruited from June 2023 to January 2024. Weight-bearing, anteroposterior radiographs were first centred on the ankle joint to obtain a genuine anterior-posterior image (‘mortise view’), then shifted proximally to the centre of the tibial plateau. A stitching tool was used to get a mortise view extending up to the knee. A bead of lead was used to mark the tuberosity. The radiographs were captured twice in each patient to analyse the reliability of the overall approach. The MDTA was measured according to the various definitions in the literature. Two independent examiners measured each angle twice on both radiographs in each patient.

Results
The measurement of the MDTA using the mechanical axis resulted in the same reliability as the established measurement of the MDTA using the anatomical axis. Using the tibial tuberosity as the centre of the proximal tibia resulted in more diverse findings compared to using the method of bisecting the proximal tibia plateau as the tibial centre. Observed differences in MDTA measurements between image pairs could be mainly explained by intra-observer variation, i.e. the ability of observers to measure an MDTA in a reliable manner in a single image. The mean absolute difference between MDTAs across the two images was in the magnitude of 0.8°.

Conclusion
Weight-bearing, whole lower leg radiographs centred on the proximal tibia and ankle joint provide reproducible values for the MDTA. In these images, the clinically important mechanical axis can be determined with the same reliability as the anatomical axis, leading to more options for surgeons to calculate the MDTA. The tibial tuberosity should not be used as a reference to determine the MDTA.

Background:
Pressure distribution in the ankle joint is influenced by various factors, including hindfoot alignment. This study aims to assess the impact of hindfoot alignment on contact pressures in the ankle joint in the setting of supination external rotation (SER) type ankle fractures according to Lauge-Hansen.
Methods:
SER fractures were created in 10 human cadaver lower extremity specimens, creating progressive stages of injury: without fracture (step 0), SER fracture and intact deltoid ligament (step 1), superficial deltoid ligament disruption (step 2), and deep deltoid ligament disruption (step 3). At each step, varus and valgus alignment was simulated by performing an calcaneum osteotomy. Each limb was axially loaded following each osteotomy at a static load of 350N. The center of force (COF), contact area (CA), and peak contact pressure (PP) under load were measured, and radiographs of the ankle mortise were taken to analyze the medial clear space (MCS) and talar tilt (TT).
Results:
The COF (5,3mm; p = 0.030) and the CA (188,4mm2; p=0.015) changed significantly in step 3 in the valgus hindfoot alignment compared to baseline parameters, indicating the importance of deep deltoid ligament integrity in maintaining normal ankle joint contact stress in the valgus hindfoot. These changes were not seen in the setting of varus alignment (COF: 2,3mm, p=0.059; CA: 121mm^2, p=0.133). PP were found to not change significantly in either varus or valgus (varus: p=0.132, valgus p =0.464).
The MCS demonstrated significant widening in step 3 compared to step 0 (0,9mm; p = 0.020) in both varus and valgus hindfoot alignment. In contrast the TT increased significantly in step 3 in the valgus hindfoot (2,8°; p=0.020) compared to step 0.
Conclusion:
SER IV fractures with valgus hindfoot alignment revealed significant changes in pressure distribution and radiographic parameters when compared to SER IV fractures with varus hindfoot alignment. This should be considered in decision making when treating SER fractures in the clinical setting.

Introduction: Ankle osteoarthritis (OA) is predominantly caused by trauma, with common radiological bone changes comprise subchondral bone sclerosis and cyst formation. In this study, we describe the subchondral characteristics associated with secondary ankle OA using a recently developed histological scoring system (Osteoarthritis Bone Score).

Methods: Resection specimens of the distal tibia were harvested from five consecutive patients (3 female, age range [51-83 years]) undergoing ankle arthroplasty for secondary OA due to hemochromatosis (n=1), ligamentous injuries (n=2) and osseous injuries (n=2). Histopathological analyses were conducted on regions-of-interest containing cartilage lesions. Tissue sections were stained with Safranin-O to grade cartilage degeneration using Mankin score (0-14). A novel trichrome staining method (Picrosirius red, Alcian blue, Fast Green) was used to calculate the Osteoarthritis Bone Score (OABS: 0-7) which evaluates presence of cysts, fibrosis, inflammation, cartilage islands as well as trabecular thickening, blood vessel density and tidemark integrity in the subchondral bone.

Results: All specimens displayed severe chondropathy (Mankin score >10), with four out of five samples showing denuded subchondral bone (Mankin score 14). Histopathological features of subchondral bone tissues showed higher intra-patient variability, with high OABS observed in patients with osseous injuries (grade 6) and hemochromatosis (grade 4), and low grades observed in patients with ligamentous injuries (grade 1-3). Interestingly, none of the specimens showed signs of inflammation defined as hypercellular fibrovascular infiltration of marrow spaces. Cartilage islands (endochondral bone formation) and marrow fibrosis were common features among specimens. Osteoid formation, blood vessel density, and thickening of the subchondral cortical plate and trabeculae were increased in high OABS grades (osseous injuries, hemochromatosis) compared to low OABS grades (ligamentous injuries).

Conclusion: Osteoarthritis Bone Scores differed to a greater extent than chondropathy scores in secondary ankle OA. This suggests that subchondral bone changes are a specific feature of OA pathology that is not a mere consequence of cartilage degeneration. Improved understanding of the molecular and cellular changes leading to differential subchondral bone pathology may open new avenues for pharmacological treatment in ankle OA.

Introduction : Our first aim was to compare the long term clinical and radiological outcome of patients sustaining a trimalleolar fracture with a posterior malleolar fragment (PMF) between the patients who had a fixation of the PMF and those who didn’t.
Our secondary aims were to compare the postoperative complication rate, to identify independent risk factors associated with worse clinical and radiological outcome and to assess if the indication of PMF fixation was correlated with the fragment size.
Methods : For this monocentric retrospective comparative study, we included 69 consecutive patients who were operated for a trimalleolar fracture between 2008 to 2013. They completed the SF-12 and the EFAS score at least 10 years after surgery. The radiological osteoarthritis was assessed according to the Kellgren and Lawrence classification. Their demographics (BMI, sex, annual income, smoking status and presence of diabetes) were taken from the chart. The size of the PMF was measured in the preoperative x-ray and the CT and classified according to the Haraguchi classification
Results : 69 patients with trimalleolar fractures were included. 21 (30.4%) of them had a fixation of the PMF by plate and 48 (69.6%) of them had no fixation of the PMF. 49 patients were female (71.01%) and 20 (28.99%) were male. Mean follow-up was 11.3 years. Mean age was 51.4y.o and mean BMI was 26.7. 9 patients (13.04%) had diabetes and 20 patients (29.4%) were smokers. There was no difference between the two group in the long term clinical PROMS (EFAS, SF-12) nor in degree of osteoarthritis (p=0.05). Patients in the fixated PMF group had a higher complications rate (p=0.0004527). In the linear regression analysis diabetes was a predictor of negative outcome for the PCS (p=0.0078) and malreduction of the syndesmosis was a predictor of negative outcome for the EFAS score (p=0.031) and osteoarthritis (p < 0.0001). The PMF size was significantly higher in the fixated group and wasn’t correlated to the long term clinical outcome, except for the mental part of the SF-12 (p=0.029).
There was no significant difference between the two groups in the follow-up surgery rate(p=0.17).
Conclusion & perspectives: Fixation of PMF doesn’t change the clinical and radiological outcome in the long term if the ankle joint is congruent. In contrast the posterolateral approach presents more complications. Surgeons must be aware of this during their design making.

Introduction: Progressive collapsing foot deformity (PCFD) remains a challenge in the treatment of the foot and ankle disorders. Surgical planning hinges on the complexity of the deformity, emphasizing the need for precise differentiation through advanced imaging diagnostics. Traditionally, weightbearing radiographs are employed for PCFD patients. Conversely, the introduction of weightbearing computed tomography (WBCT) has revolutionized the 3D assessment of the deformity. In an effort to better understand how WBCT findings can be integrated in the evaluation of radiographs, we aimed to (1) compare specific X-ray measurements to corresponding WBCT measurements; (2) evaluate the accuracy of X-ray measurements of interest; and (3) investigate whether X-ray measurements can predict osseous impingement in the subtalar joint region identified through WBCT.

Methods: Two clinically established measurements were assessed on standardized weightbearing radiographs (manually) as well as on the WBCT datasets (auto-generated): (1) talo-calcaneal overlap (TCO, mm) and (2) talo-navicular coverage (TNC, °). In addition to the measurements, osseous impingement in the subtalar joint region was assessed on WBCT using three criteria: (1) joint obliteration; (2) cyst formation; and (3) signs of secondary instability. Two of the criteria needed to be fulfilled to confirm subtalar impingement.

Results: While no significant difference between X-ray and WBCT measurements was evident for TCO, significant differences were found for TNC. Inter- and intra-observer reliability was >0.9 for both measurements on X-ray. The mean bias of measurement (between X-ray and WBCT) was 0.2 mm for TCO and -22 degrees for TNC. Cohen’s Kappa for inter- and intra-rater reliability to assess patients for subtalar instability was >0.9. The probability to predict subtalar impingement was ≥0.85 if TCO was >15 mm or TNC was >25 degrees on X-ray.

Conclusion: The examined imaging parameters are reliably assessable through conventional radiographs (TCO/TNC) or weightbearing computed tomography (osseous subtalar impingement). In situations where WBCT is unavailable, X-ray-assessed TCO and TNC can serve as predictors for osseous sinus tarsi impingement. This finding plays a pivotal role in evaluating PCFD patients, aiding in the decision-making process between joint-preserving interventions (e.g., osteotomies) and joint-sacrificing procedures (e.g., realignment fusion) during surgical considerations.

Introduction:
Chronic Achilles tendinopathy with large defects are surgically challenging. Concerns
exist regarding transosseous transfer of the flexor hallucis longus (FHL) tendon due
to the shortened lever arm of flexion and weakening of the big toe. The aim of this
study was to demonstrate the long-term outcome of transosseous FHL transfer for
the treatment of large Achilles tendon defects.
Methods:
We retrospectively analyzed 28 patients who underwent FHL transfer. The extent of
the defect was measured with magnetic resonance imaging before (baseline) and
during the operation. Outcome parameters included the German Foot Function Index
(FFI-D) evaluated at baseline and 6, 12 and 24 months postoperatively, a specific
questionnaire to determine 24-month patient satisfaction, and the documentation of
complications throughout the postoperative course as well as restrictions concerning
plantar flexion strength of the great toe at 24 months.
Results:
Mean baseline FFI-D subscores of pain (37.2) and function (52.3) improved
significantly by 24 months post-surgery with lower mean subscores of 6.9 and 15.0,
respectively (p &lt; 0.001). At 24 months, 57% of patients were very satisfied and 25%
were satisfied since having undergone the procedure. All patients noted a relevant
improvement at the 2-year follow-up with only one stating that while they perceived
the flexion weakness of their big toe, this was not accompanied by any relevant
functional restriction. Lastly, we reported two patients each with minor complications
of delayed wound healing and one patient who experienced a major complication of
severe perifocal wound necrosis during the early postoperative period; the latter
required plastic surgery with an additional skin flap. By the 2-year follow-up, all three
patients were satisfied with their postoperative outcome and free of symptoms.
Conclusion:
This work shows that transosseous FHL transfer is a successful surgical treatment
for large defects of the Achilles tendon. The majority of patients were satisfied with
the outcome of the procedure and experienced a significant improvement in both
function and pain level. Flexion weakness of the big toe does not appear to be a
relevant issue after FHL transfer.

Introduction
Hallux valgus (HV) deformity is one of the most common foot pathologies. Maintaining the correction of the hallux postoperatively is essential for adequate bony and soft tissue healing, notably with the emergence of percutaneous surgery with no osteosynthesis hardware. Current solutions relying on toe spacers and tapes tend to be time-intensive and do not guarantee correction maintenance of the hallux. 3D printed orthoses are advantageous in terms of ease of use and comfort compared to traditional models. This study aims to explore the viability and benefits of employing a personalized foot orthosis in HV patients post-surgery through 3D printing technology.
Methods
Patients scheduled for HV surgery have been prospectively enrolled starting from November 2023. The patients' foot shape was captured preoperatively with the help of a 3D optical scan. The orthosis was numerically designed based on this scan, including a correction of the HV deformity. It features a customizable spacer between the hallux and the second toe (T2) to maintain a proper alignment for optimal bony and soft tissue healing. The orthosis was 3D printed in a flexible thermoplastic polyurethane (TPU). A questionnaire was developed for the assessment of clinical efficacy (wear duration, fit) and patient satisfaction (pain, comfort). The questionnaire was completed by orthopedic surgeons and participating patients during regular follow-ups for up to five weeks post-surgery.
Results
To date, six patients were enrolled, and four patients have been followed up until three to five weeks. All patients reported high overall satisfaction. Two patients noted discomfort due to friction at T2. Therefore, we adapted the design of this area. The device stayed in place while walking. The hallux remained safely stabilized in correct alignment. The orthosis could be easily adapted to oedema thanks to material flexibility and Velcro closure. Its lattice structure allowed for skin breathability. The orthosis was easy to put off and back on, facilitating wound care.
Conclusion
To our knowledge, this is the first description of using a 3D printed orthosis for HV surgery aftercare. The preliminary results suggest it is a reliable and comfortable option with the potential to replace traditional methods. Our ongoing patient inclusion and evaluation will allow us to refine the results. Further studies are required to validate these outcomes and compare them with traditional methods.

Introduction
The optimal duration of postoperative antibiotic treatment in orthopedic spinal infections is unknown. We report the 3rd interim analysis of the prospective randomized trial (SASI), emphasizing on material-related infections (ITT population between the study time points End-of-Treatment and Test-of-Cure).

Methods
A 1:1 randomization allocated adult spine patients with a residual infected implant into a short (6 weeks) or long (12 weeks) postoperative, systemic and targeted, antibiotic group. The major outcomes are "clinical failure" (reoperation for wound problems, new infections and/or uninfected mechanical reasons) and "microbiological recurrence" (infection relapse with the same pathogen(s) after therapy).

Results
In the database, we compare 81 infection episodes with 6 weeks’ therapy against 85 cases treated with 12-weeks of antibiotics. Overall, 11% in the short treatment arm revealed a “clinical failure” in the short and 14% in the long arm (9/83 vs. 12/85; Pearson-χ2-test; p=0.52). The corresponding numbers for “microbiological recurrence” were 2/83 (2%) vs. 1/85 (1%), p=0.55, respectively. The median number of surgical debridement was 1 in both arms (Wilcoxon-ranksum-test; p=0.28). Among 51 serious adverse events (SAE), there was a non-significant tendency in disfavor of the 12-weeks treatment arm (22/83 vs. 29/85 SAE, odds ratio 0.7; 95%CI 0.3-1,4; p=0.28). The formal non-inferiority for “micro-biologically-identical-recurrence” situated within a 5%-margin (2.1% percentage points [90%CI 2.2% to 4.6%]), that of “clinical failure” at a 10%-margin (5.2%, 90%CI 11% to 5%).

Conclusion
Equally at the 3rd interim analysis, a six-week antibiotic treatment remains noninferior to 12 weeks in residual implant-related spine infections after debridement. The SASI trial continue in terms of a long-term follow-ups targeting the scheduled per protocol analyses with a slightly higher sample size.

Introduction
Effective perioperative pain management and early mobilization after surgery are crucial to optimize recovery. The aim of this study was to determine the effect of the PEricapsular Nerve Group (PENG) block on postoperative (1) patient-reported pain, (2) total consumption of morphine and (3) length of stay (LOS) after primary anterior total hip arthroplasty (THA).

Methods
IRB-approved, single-center, multidisciplinary, prospective, randomized, double-blind controlled trial of patients undergoing primary anterior THA for osteoarthritis between June 2022 and April 2023. Preoperatively, patients were randomly assigned to either the study group (35 patients) or the control group (29 patients). Both groups underwent an ultrasound-guided injection of a 20 mL solution, the study group received 0.5% ropivacaine and the control group 0.9% NaCl. Each patient, anesthesiologist and surgeon were blinded to the solution injected. Four patients who required postoperative weight-bearing restrictions or whose documentation was incomplete were excluded from the study, resulting in a total of 60 patients (60 hips). The demographics of the two groups did not significantly differ. Overall the study population was 38% female, mean age was 64 ± 12 (34 to 84) years and mean body-mass-index was 27 ± 4 (19 to 38) kg/m2. We assessed (1) postoperative pain at 1h, 6h, 12h and 24h postoperatively via the Visual Analogue Scale (VAS) ranging from 0 (no pain) to 10 (maximal pain), (2) total morphine consumption in Morphine Equivalent Dose (MED) during the first 24 hours after surgery and (3) the LOS in days. Analysis were done using the Mann-Whitney test. The significance level was set at α < .05.

Results
VAS, at any of the four time points, did not differ significantly between the two groups (all P > .05). The lower 24-hour morphine consumption in the study group was not statistically significant (P = .110). The study group had a significantly shorter LOS than the control group (2.8 ± 1 [2 – 5] days vs 3.9 ± 1.5 [2 – 7] days, P = .003). No femoral motor nerve block or injection site infection were observed in either group.

Conclusion
In this prospective randomized controlled trial, the PENG block showed no significant difference in terms of postoperative reported VAS, a trend towards lower morphine consumption, though this did not reach statistical significance, and a statistically significant decrease in LOS after primary anterior THA when compared to a placebo.

Introduction: Reverse total shoulder arthroplasty (RTSA) offers satisfactory mid-term outcomes for a variety of pathologies but there is limited long-term follow up data. This study reports long-term clinical and radiographic outcomes, and predictive factors for outcome following RTSA implantation.

Methods: A prospective database of primary RTSAs performed at a single, tertiary referral center was analyzed at a minimum of ten years postoperative. Clinical outcomes included absolute and relative Constant-Murley score (CSa and CSr), Subjective Shoulder Value (SSV), range of motion, pain, complication rate and reintervention rate. Radiographic measurement included critical shoulder angle (CSA), lateralization and distalization shoulder angles (DSA, LSA), reverse shoulder angle (RSA), acromiohumeral distance (ACHD), center of rotation, glenoid height, analysis of notching, radiolucent lines, heterotopic ossification, and tuberosity resorption.

Results: 135 RTSAs (133 patients) were available for analysis at a mean follow-up of 10.9 ± 1.6 years. The mean age was 69 ± 8 years with 76 female shoulders (76 patients, 56%). Satisfactory results were achieved at long-term follow-up for CSa (64 ± 16), CSr (79% ± 18%), SSV (79% ± 21%), CS pain (14 ± 3) as well as flexion (117° ± 26°) and abduction (125° ± 35°). There was no deterioration in CSa, CSr and SSV, abduction and internal rotation over time. However, flexion and external rotation deteriorated while pain improved. Scapular notching, heterotopic ossification and radiolucent lines progressed during the study period. Analysis of predictive factors revealed younger age (p=0.040), notching grade II (p=0.048), tuberosity resorption (p=0.015), glenoid radiolucent lines (p=0.015) as predictive for impaired outcome. The complication rate was 28% with a reintervention rate of 11%.

Conclusion: RTSA can provide satisfactory long-term results without significant deterioration over time for most of the clinical parameters. Negative clinical outcome predictors were younger age, grade II notching, tuberosity resorption and radiolucent lines around the glenoid.

Introduction: Screw loosening following posterior spinal fusion surgery is a prevalent phenomenon, potentially leading to severe complications. A recent study conducted by our group has successfully demonstrated the feasibility of using patient-specific finite element (FE) modeling to predict screw loosening. However, the current modeling techniques demand significant manual effort and computational resources, limiting their practicality for routine clinical application. In response, we have innovated a framework designed to markedly diminish both the computational demands and manual intervention. This study evaluates the practicality of this automated framework and its effectiveness in predicting screws at risk of loosening during the medium-term postoperative period.
Methods: We retrospectively included 27 patients (96 pedicle screws) who underwent lumbar posterior spinal fusion surgery at our facility, consented to the use of their data for research, and had pre- and postoperative CT scans, with revision surgery within 27 months. Patient-specific FE models were generated by integrating bone segmentation and mechanical property estimates from preoperative CT scans with the configuration of surgical instrumentation (including screw types and placements) from postoperative CT scans. The external loading conditions were derived from the sagittal alignment and the body weight of each patient. Data from the surgical report of the revision procedure provided the basis for determining screw loosening. The framework's accuracy in identifying at-risk screws was gauged using the receiver operator characteristics (ROC) area under the curve (AUC).
Results: The automated modeling framework showcased robust performance across both initial and revision surgeries, regardless of the fused segments’ number or locations, demonstrating a high capability (Sensitivity: 56%, Specificity: 96%, ROC AUC: 0.740) in predicting the risk of screw loosening. Notably, beyond the initial steps of volumetric segmentation and data input, the process required no manual labor. Furthermore, simulations were completed in less than 5 minutes on an Intel Xeon (i9-7980) processor.
Conclusion: Our study introduces an important step towards utilizing automated biomechanical modeling to enhance outcomes in posterior spinal fusion surgeries.

Background
Multiple 2D MRI studies indicate that the size of the labrum adjusts in response to altered joint loading. In patients with hip dysplasia, it tends to increase as a compensatory mechanism for inadequate acetabular coverage.
Purpose
Using a deep learning based approach for automatic 3D segmentation of MRI we asked: What are the differences in labrum contribution to joint contact surface among different hip deformities and which radiographic parameters influence labral contribution to joint contact surface?
Study design Retrospective Cross-Sectional Study
Materials and Methods
This retrospective study was approved by the local ethics committee with waiver for informed consent. 98 patients (100 hips) with symptomatic hip deformities undergoing direct hip MR arthrography (3T) between January 2020-October 2021 were consecutively selected (mean age = 309; 64% female). Standard imaging protocol included multiplanar PD-w TSE images and an axial-oblique 3D T1 MP2RAGE sequence. According to acetabular morphology, hips were divided into subgroups: dysplasia (lateral center-edge [LCE] angle < 23°), normal coverage (LCE 23-33°), overcoverage (LCE 33-39°), severe overcoverage (LCE > 39°) and retroversion (retroversion index>10% and all 3 retroversion signs positive). A previously validated deep learning approach for automatic segmentation and software for calculation of joint contact surface were used. Labral contribution to joint contact surface was defined as: labrum surface area/(labrum surface area+cartilage surface area). One-way ANOVA with Tukey’s correction for multiple comparison and linear regression analysis was performed.
Results
Mean labral contribution of joint contact surface of dysplastic hips was 265 (17–33)% and higher compared to all other hip deformities (p ranging from 0.001 to 0.036).
Linear regression analysis identified LCE angle ( = -0.002, p < 0.001) and femoral torsion (=0.001, p=0.008) as independent predictors for labral contribution to joint contact surface with a goodness of fit of R2=0.35.
Conclusion
Labral contribution to joint contact surface differs among hip deformities and is influenced by lateral acetabular coverage and femoral torsion. This study paves way for a more in-depth understanding of the underlying pathomechanism and a reliable 3D analysis of the hip joint which can be indicative for surgical decision making in patients with hip deformities.

INTRODUCTION
Accurate pedicle screw placement in spine surgery is essential due to the proximity of vital neural structures, indicating the utilization of surgical navigation. State-of-the-art navigation systems still rely on pre- or intraoperative imaging with ionizing radiation, leading to increased radiation exposure and surgery time. To overcome this shortcoming, we propose a novel PSP planning method capable of calculating the navigation information, such as entry points and trajectories of the screws, directly from intraoperative camera data and without ionizing radiation. This study's objective was to compare our approach's accuracy against gold standard methods.

METHODS
Our approach employs an optical depth camera (ZED mini, StereoLabs) to provide a 3D reconstruction of visible surfaces, in our case, a 3D surface of the exposed dorsal lumbar spine. A first AI module processes this data to identify the individual vertebrae levels and predict their full 3D shape, including invisible parts, as 3D models. Based on the predicted 3D model, an AI-powered planning component identifies the entry points of the screw and trajectory. For evaluation, an ex-vivo dataset of 10 specimens was used, consisting of the camera data from two perspectives and ground truth CT data. The CT data was segmented to establish gold standard screw trajectories, which were then compared to our method for accuracy evaluation.

RESULTS
The PSP planning method showed an average entry point error of 1.98 mm and an average trajectory error of 8.78 degrees. Clinical outcome evaluation using the Gertzbein and Robbins classification method yielded 98.50% clinically acceptable grades (A and B) and 1.50% unacceptable grades (C).

CONCLUSION
The accuracy of our approach matches state-of-the-art CT-based PSP planning methods without requiring registration, thereby reducing radiation exposure. The method is planned to be integrated into a robotic platform to serve as an intraoperative navigation technology.