Bone regeneration in the proximal femur following implantation of modular revision stems with distal fixation

Introduction

A quantitative analysis of the response of proximal femur bone to implantation of revision stems with distal fixation and of the factors that affect that response has not previously been published.

Materials and methods

A prospective study of 138 stem revision operations involving replacement with cementless, modular, titanium revision stems with distal fixation (Revitan, Zimmer GmbH, Winterthur, Switzerland) was designed to assess Barnett and Nordin scores at the proximal femur obtained immediately after surgery and at a 3-year follow-up examination in order to analyze bone regeneration in the proximal femur and associated response-modifying factors.

Results

In general, a bone formation with increase of the Barnett and Nordin score was observed. However, stress shielding occurred in cases of osteoporosis or more severe bone defects. A statistical analysis of possible factors that might affect the bone response revealed that the degree of bone regeneration was directly related to the Barnett and Nordin score obtained immediately post-surgery and the severity of the bone defect and only indirectly to the length of the stem, which is determined by the type of bone defect, and to the necessity of interlocking screws.

Conclusion

Distally fixed titanium revision stems do not result in stress shielding per se. Proximal bone response depends mostly on the condition of the bone before and immediately after the operation and not, as stated in many reports, on surgical procedures such as method of approach or the thickness of the prosthesis.