Artikel
Radiographic Analysis of the Response of the Proximal Femur to the Silent Hip Prosthesis
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Autoren
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K. Junghans
- ENDO-Klinik, Orthopädie, Hamburg, Germany
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J. Sullivan
- ASAM Australian School of Advanced Medicine, Sydney, Orthopaedic Surgery, Sydney, Australia
| Veröffentlicht: | 21. Oktober 2010 |
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Gliederung
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Objective: Background With people living longer and the trend to earlier intervention, many patients will outlast the lifetime of current hip implants and require a revision procedure. Traditional THR involves a low neck cut and the insertion of a stem into the femoral shaft. This technique unloads the proximal femur, causing stress shielding. The SilentTM hip stem is a conservative collarless neck-only femoral prosthesis with less resection of bone and does not disturb the shaft. The prosthesis is designed to transfer loads in a more physiological manner to avoid loss of proximal femoral bone through stress shielding.
Methods: Methods We analyzed the radiographs of 47 patients (mean age 54.8 years) in a maximum follow-up of 66-months (mean 33.0 months) to determine the response of the proximal bone around the implant. To categorize these changes we used a modified Gruen classification. We also investigated the effect of the positioning of the prosthesis (insertion angle and penetration depth) on proximal remodelling.
Results and conclusions: Results At the latest follow-up 46 SilentTM hips (97.9%) were radiologically stable without signs of loosening. One stem was excluded from the study because of an early periprosthetic fracture. 29 stems (63.0%) presented positive calcar remodelling (modified zone 5) between 12 and 24 months, depending on stem positioning. Both a smaller prosthesis to shaft angle and a bigger distal clearance caused a significant higher incident of positive calcar remodelling (p<0.001). 30 out of 39 stems (76.9%) presented a trabecular bone formation between the tip and the lateral cortex, significantly correlating with a higher prosthesis to shaft angle (p=0.019).
The SilentTM hip femoral prosthesis is a good alternative conservative option for the younger patient, presenting a physiological loading of the femur with good calcar bone preservation. Smaller prosthesis to shaft angles (mean 133°) and a bigger distal clearance (mean 5.2mm) favor positive remodelling at the calcar, higher angles (mean 138°) favour positive remodelling at the tip of the stem.
