Periprosthetic osseous changes 2, 4, and 6 years after implantation of cementless Zweymuller-stems - A cross-sectional study

Aim: According to the results of longitudinal studies, the use of distally anchored femoral prostheses leads to marked proximal stress shielding. Zweymuller stems should be controlled some years after implantation. Method: In a cross-sectional study, we examined 92 patients clinically, radiologically, and osteodensitometrically 2, 4, and 6 years after implantation in order to assess the osseointegration of Zweymuller shafts as independently as possible of age. The non-operated contralateral limb or Gruen's zone 4 below the prosthesis was used as a control group. Results: At no time did the parameters assessed indicate any reduction in proximal bone density as compared with the control group. Zone 7 (medial-proximal) even showed an increase in bone density after 2 and 4 years. Nevertheless, absolute bone density was lowest proximally both pre- and postoperatively. Six years after implantation women even showed a 15% increase in summated periprosthetic bone density as compared with the control group. No influence of femoral shape on bony remodeling was demonstrated. Conclusion: Periprosthetic bony remodeling cannot be attributed exclusively to the shape of the shaft. Longitudinal studies do not adequately reflect the reduction in periprosthetic bone mass that-occurs as a function of age and altered activity level. The osseointegration of hip prostheses is influenced by other factors such as musculoskeletal lines of force, sex, and age.