Abstract
Purpose of the study: The majority of acetabular bone defects observed during revision hip surgery can be treated with a hemispheric implant, associated or not with a bone graft. In many patients however, loss of bone stock is so great that a more complex system must be used with a sustaining ring, multilobulated implants, or massive allografts. All have their technical difficulties or problems with fixation. The purpose of this work was to evaluate a new technique for acetabular reconstruction using modular implants fashioned with a new biomaterial, porous tantalum, which had specific properties favoring osteointegration.
Material and methods: These modular implants were fashioned so as to enable reconstruction of the acetabular cavity in cases with complex loss of bone stock. The design allows simultaneous biological incorporation and mechanical support with a press-fit hemispheric cup. These implants were used for 16 hips (16 patients, 12 women and 4 men, mean age 63.6 years, age range 34–86 years). These patients were followed for 31.9 months on average (range 24–39 months). The acetabular defects were Paprosky 2A (n=1), 2B ‘n=3), 2C (n=1), 3A (n=5), 3B (n=6). On average, these patients had undergone 2.8 cup replacements (1–9) on the same hip.
Results: The mean Harris hip score improved from 39.31 (range 33–52) preoperatively to 75.18 (range 52–92) at last follow-up. Preoperatively, the center of rotation of the prosthetic hip was situated a a mean horizontal distance of 18.6 mm (range −3 to 46 mm) and a mean vertical distance of 27.6 mm (range −16 to 52 mm) from the ideal center of rotation according to Ranawat. Postoperatively, the prosthetic center of rotation was situated at a mean horizontal distance of 10.5 mm (range 1–25 mm) and a mean vertical distance of 7.4 mm (range −15 to 25 mm) front the ideal center of rotation. None of the implants presented loosening or migration at last follow-up.
Discussion: At short-term follow-up, this modular system for acetabular reconstruction has provided good results for acetabular reconstruction which can accept a hemispheric cup alone and which would have required use of other reconstruction methods such as structural allografts, sustaining rings or other.
Conclusion: A longer follow-up will be needed to determine whether these good clinical and radiological results persist with time.
Correspondence should be addressed to SOFCOT, 56 rue Boissonade, 75014 Paris, France.
