|Beitragstitel||Proximal bone restoration patterns in revision THA using distally fixed modular tapered titanium stems and an extended trochanteric osteotomy approach.|
Background: Mechanical failure at the modular junction of femoral revision stems is an uncommon but serious complication in revision total hip arthroplasty (THA). The lack of adequate osseous support to the proximal component, especially in cases of an extended trochanteric osteotomy (ETO) approach, is considered one of the risk factors for stem failure. In the current study, we analyse proximal bone regeneration patterns in patients undergoing revision THA for aseptic stem loosening through an ETO approach using an uncemented dual modular, tapered titanium stem.
Methods: We reviewed clinical and radiographic charts prior and immediately after surgery as well as 2, 6, 12 and 24 months postoperatively in all patients treated from 2000-2015. Radiographic analysis consisted of preoperative bone loss assessment according to Gross classification system. The femur was divided according to the Gruen zones. Formation of new cancellous bone as well as presence of direct osseous contact to the stem was noted in a timely manner for each Gruen zone. The presence of osseous support of the proximal modular component as well as at the level of the modular junction was examined.
Results: 54 patients with a median age of 73 ±11 years at revision THA were included. All patients showed restoration of proximal bone mass at final follow up examination. Radiographically visible new bone formation was first seen in gruen zones 13, 6, 2 and 9, emphasising that bone regeneration occurs in a distal to proximal direction. Cases with longer proximal components of the dual modular revision stem had a trend towards earlier osseous support at the modular junction than cases where a short proximal component was used. Overall, 75% of patients showed direct bony contact at the modular junction two years after surgery, while osseous support to the proximal component was observed in 81% of patients. No failure at the modular junction was observed.
Conclusion: Restoration of proximal bone in revision THA with transfemoral implanted, dual modular tapered stems seems to occur in a distal to proximal direction. Two years after surgery, radiologic signs of bony support to the modular junction and the proximal modular component can be expected in a high percentage of cases. However, the use of proximal modular components of a shorter size might lengthen time until osseous support to the component is accomplished and could possibly affect the risk of mechanical failure at the modular junction.