Ganz reinforcement rings in acetabular revision: indications and medium-term results

Metal reinforcement rings, systems used widely in the past for prosthetic revision surgery, are still effective, in that they allow us to restore the correct hip rotation center and protect the bone grafts used to increase acetabular bone stock. To provide a better definition of the current indications for use of reinforcement rings in acetabular revisions we conducted a retrospective study in a group of 25 patients in whom a Ganz reinforcement ring was used in association with autoclaved cancellous bone grafts. The Ganz ring is made of titanium and it has a lower hook that contributes to the mechanical stability of the implant. Mean age of patients was 72.5 years. Pre-revision acetabular bone defects were divided according to the Paprosky classification system: type 2A: 2 cases; type 2B: 6 cases; type 2C: 6 cases; type 3: 6 cases; type 3B: 5 cases. Clinical and radiographic results were evaluated after a mean follow-up of 4.6 years. Score based on the Harris evaluation form went from a mean preoperative value of 45 points to 92 points after revision. Overall, clinical results were excellent in 9 cases (36%), good in 12 cases (48%), fair in 3 cases (12%), poor in 1 case (4%). Radiographically, we observed a significant reduction (62%) in mean vertical distance of the hip rotation center after revision, that contributed to reduction in hypometria of the limb submitted to surgery, ranging from a mean preoperative value of 2.2 cm to 0.72 cm after surgery. Stability of the implant in time was evaluated based on the Gill criteria. None of the cases required further revision surgery; in 3 cases (12%) with type 3 preoperative defects, the implant was judged to be probably or possibly loosened because of the presence of radiolucent lines.