Acetabular revision. The role of rings and cages

This study reports on the successful long-term use of the acetabular roof ring and the antiprotrusio cage in acetabular reconstruction in which the hip center and acetabular biomechanics are normalized and bone stock is restored through the use of morselized allograft. The failure rate of the acetabular roof ring used in 57 patients who were followed up for a mean of 8.3 years was 12.5%. The failure rate of the antiprotrusio cage used in 38 patients who were followed up for a mean of 6.6 years was 5.4%. The higher failure rate of the acetabular roof ring resulted from its inappropriate use in patients with medial wall deficiency and protrusio. The acetabular roof ring is indicated for patients with isolated peripheral segmental or cavitatory defects. The antiprotrusio cage is indicated for patients with extensive combined segmental and cavitatory defects but particularly for those patients with protrusio and medial segmental bone loss. Both methods have given a high degree of success for evaluation of implant specific, patient subjective, and global health status instruments such as the Short Form-36.