Long-term outcome of 73 Zweymüller total hip prostheses with a screw cup in patients under 50 years of age.

Total hip arthroplasty in young patients is associated with high failure rates and the best option for this demanding group of patients remains controversial. We report the long-term results of 73 consecutive Zweymüller total hip arthroplasties with a titanium threaded cup and a polyethylene insert in 67 patients aged under 50 years at the time of surgery (mean 43 years, range 23-49). Independent assessment was performed clinically and radiographically, and Kaplan-Meier analysis was used to determine survival for different end-points. Three hips were revised for septic loosening, three cups for aseptic loosening and one hip because of a periprosthetic fracture. Three patients (3 hips) died and seven patients (8 hips) were lost to radiographic follow-up without any reoperation. The mean follow-up was 17.5 (15-21) years and the mean HHS was 90 (52-100). Survival with an end-point of revision for any reason was 89% (95% C.I. 85-93) and of revision for aseptic loosening was 94% (C.I. 95-99) at 17 years. Zweymüller total hip arthroplasty with a titanium threaded cup and a polyethylene insert showed good long-term results, even in this group of young patients.

A new digital preoperative planning method for total hip arthroplasties.

Preoperative templating is an important part of a THA. The ability to accurately determine magnification of the hip on the radiograph and apply identical magnification to the radiograph and template will improve accuracy of preoperative templating of THA. We designed a templating method using a new way of determining the hip magnification with a linear relationship between magnification of the hip and the reference object on top of the pubis symphysis; the relationship was determined on 50 radiographs. We then compared our method with two other templating methods: an analog method assuming an average hip magnification of 15% and a digital method determining the hip magnification with a one-to-one relationship between the reference object and the hip. All methods were reproducible. Uniform undersizing occurred when templating with the digital method based on the one-to-one relationship; the analog method best predicted the implanted prosthesis size, closely followed by our new digital templating method; the new method will be particularly applicable for preoperative THA when analog methods are replaced by digital methods.