Increased femoral anteversion is associated with altered lower-limb kinematics and impaired muscle functionality during gait [1,2], while it does not lead to increased joint loading in patients with an in-toeing gait pattern [3]. However, walking straight would require higher muscle forces and would lead to larger co-contractions in the transversal plane [2]. Increased femoral anteversion can be surgically addressed through femoral derotational osteotomy, which was shown to normalize most gait kinematics and kinetics post-operatively [4]. Nevertheless, no information is available on how this surgery affects joint and muscle forces. Therefore, the aim of this study was to analyze the effect of femoral derotational osteotomy on joint and muscle forces in patients with idiopathic increased femoral anteversion compared to controls.
Seventeen pediatric patients with isolated, CT-confirmed increased femoral anteversion (limbs=25, pre-op age: 13.2±2.2 years, pre-op anteversion: 49.0±7.1°) underwent 3D gait analysis pre and post-surgery. Knee (KCF) and hip (HCF) contact forces as well as hip joint spanning muscle forces were evaluated with inverse dynamics (AnyBody Technology, Denmark). Statistical parametric mapping paired t-tests were used to evaluate pre and post-op differences and two sample t-test to compare post-op results to controls.
Significant improvements in kinematics (hip rotation, foot progression, knee and hip flexion) could be observed pre to post. Absolute KCF and HCF remained unaltered after surgery and did not differ from controls. In terms of muscle functionality, gluteus minimus and deep external rotators muscle forces decreased in mid stance, while adductor muscle forces increased during stance post-op compared to pre-op. Due to an improved knee extension post-op, the rectus femoris muscle force decreased to normal values during mid and terminal stance. Post-op, only deep external rotators muscle forces differed from controls.
This study could show that the femoral derotational osteotomy can restore muscle functionality in addition to normal gait kinematics, while joint loading remains within normative ranges. This knowledge might also be more translated to other conditions where pathologic femoral anteversion is present.

[1]Alexander, et al, 2019, J Biomech,86,167-74.
[2]De Pieri, et al, 2023, Gait Posture,100,179-187.
[3]Alexander, et al, 2022, Front. Bioeng. Biotechnol.,10.
[4]MacWilliams, et al, 2016, Gait Posture, 49,202-206.

Introduction
Fibular hemimelia is a complex longitudinal malformation of the lower leg with partial or complete deficiency of the fibula resulting into dorso-fibular dislocation of the hindfoot. Typically associated are talo-calcaneal coalition, lacking rays of the foot, tibia procurvata, and longitudinal growth deficiency. It can be associated with proximal femoral deficiency typically combined with congenital deficiency of the anterior cruciate ligament. Many different techniques have been described for stabilization of the foot besides the option of amputation.
We have addressed correction of the deformity of the distal tibial epiphysis by a metaphyseal osteotomy to bend through the physis similarly to the Pemberton acetabular osteotomy. The technique was published with short term results of a maximum of 42 months follow-up (1). Meanwhile the first 4 patient treated have reached skeletal maturity and the long-term results shall be presented herein
Patient and Methods
Three patients with unilateral and one patient with bilateral fibular hemimelia were operated as described (1) at ages 7, 9, 15, and 18 months. Subsequently several other procedures have been performed on all patients mainly consisting in lengthening of the tibia combined with axial and foot alignment corrections.
Results
The Pemberton-like osteotomy lead to stable axial retainment of the hindfoot in all patients without premature closure of the physes. None of the patients would favor to have been treated by amputation inspite of the fact that most of them need adaptations of footwear.
Drawback of the study is lack of comparison with other techniques, rarity and the large spectrum of this malformation complex.
Conclusion
The technique has shown good results with continuing growth of the physis and axial weight bearing maintained at long-term. As the patients are satisfied with the results this method should be considered as an option in the management of fibular hemimelia.

1. Bending osteotomy through the distial tibial physis in fibular hemimelia for stable reduction of the hindfoot. J Pediatr Orthop B 2003; 12:27-32