Radiological evaluation of allograft reconstruction in acetabulum with Ganz reinforcement ring in revision total hip replacement.

BACKGROUND

In revision total hip replacement (THR), cages and rings are commonly used for the reconstruction of bone defects that are due to mechanical loosening of the acetabular cup and migration of the femoral head prosthesis. The purpose of this study was to evaluate the radiological results of the use of Ganz reinforcement rings with bone allografts in acetabular revision THR.

METHODS

We reviewed 30 hips of 28 patients who underwent allograft reconstruction of the acetabulum with a Ganz reinforcement ring in revision THR. The average postoperative follow-up period was 8 years. The position of the acetabular socket was measured on anteroposterior radiographs. Loosening of the acetabular component was defined as a change in the cranial or central direction of the cup or a change in the cup inclination angle at the time of last follow-up. In cases of segmental bone defects in weight-bearing areas, we used two or three strut screws prior to incorporation of the Ganz reinforcement ring to act as struts for the ring. Kaplan-Meier survivorship analysis was performed. The end point was revision surgery done because of defined loosening of the acetabular component at the time of the last follow-up.

RESULTS

All five acetabular components (16.7%) defined as showing aseptic loosening were type D defects (cranio-central defects), but no patient needed revision surgery during the follow-up period. Nine revision surgeries with strut screws for type D acetabular bone defects were performed. The calculated Kaplan-Meier survival rate at 5 years was 96.0%, and the rate at 10 years was 80.2%, using defined loosening of the acetabular component as the end point.

CONCLUSIONS

Allograft reconstruction of the acetabulum with a Ganz reinforcement ring is a useful technique for revision THR. Occasionally, a special technique (the strut screw technique) was required for the reconstruction of type D bone defects.