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Deutscher Kongress für Orthopädie und Unfallchirurgie
74. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie
96. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie
51. Tagung des Berufsverbandes der Fachärzte für Orthopädie und Unfallchirurgie

26. - 29.10.2010, Berlin

Radiographic Analysis of the Response of the Proximal Femur to the Silent Hip Prosthesis

Meeting Abstract

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  • K. Junghans - ENDO-Klinik, Orthopädie, Hamburg, Germany
  • J. Sullivan - ASAM Australian School of Advanced Medicine, Sydney, Orthopaedic Surgery, Sydney, Australia

Deutscher Kongress für Orthopädie und Unfallchirurgie. 74. Jahrestagung der Deutschen Gesellschaft für Unfallchirurgie, 96. Tagung der Deutschen Gesellschaft für Orthopädie und Orthopädische Chirurgie, 51. Tagung des Berufsverbandes der Fachärzte für Orthopädie. Berlin, 26.-29.10.2010. Düsseldorf: German Medical Science GMS Publishing House; 2010. DocIN20-1289

DOI: 10.3205/10dkou123, URN: urn:nbn:de:0183-10dkou1232

Published: October 21, 2010

© 2010 Junghans et al.
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Outline

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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.