We report significant cobalt poisoning from a damaged hip replacement with cobalt containing implant and a slow abrasion of the metal by residual ceramic particles. Chelation therapy resulted in apparent benefit.

PURPOSE OF THE STUDYThe Burch-Schneider cages (BSC) are designed to manage severe acetabular defects by bridging large bone gaps and preventing medial and superior migration of the prosthetic cup. The purpose of the study was to evaluate the results of such revisions after prolonged follow-ups. MATERIAL AND METHODSFrom 1985 to 2000 sixty-nine acetabular revisions with BSC were performed in 68 patients with an acetabular defect classified as type Paprosky 3A (32) and 3B (37) at our institutions. After meticulous debridement of the entire acetabulum cancellous chips were pressurized into the bone defects to restore the hemispherical shape. The cage flange for the ischium was then placed after slight contouring into the foramen obturatum or inside the ischium. Finally, the cage was fixed against the ilium with at least three screws. The average age at the time of surgery was 67.9 years (range, 51-78), the mean follow-up equalled 8.3 years (range, 5-20), and the mean Harris hip score was 48 points (range, 29-76). A clinical follow-up study was performed with using conventional measures such as Harris hip score, x-ray analysis, strength of the abductor muscles, and ability to walk without support. RESULTSA total of 55 patients (80.9 %) remained without any revision until the latest follow-up. Six components were removed due to aseptic loosening (8.7 %); five for septic loosening (7.2 %), and two revisions had to be performed for recurrent instability (2.9 %). Moreover, there were another six hips definitely or probably loose according to x-ray analysis resulting in a 17.4 % (12/69) rate of aseptic failure. Successful cage re-replacement was achieved only in two cases while the remaining nine hips ended as resection arthroplasties. At the time of follow-up examinations the average Harris hip score was 74 points (range, 51-91), only twelve patients were able to walk without support (12/68, 17.6 %), and insufficiency of the abductor muscles was found in fifteen hips (15/69, 21.7 %). Consolidation of the bone graft was observed in 79.7 % (55/69) of our hips. DISCUSSIONThe severe acetabular bone defect reconstructions have been deteriorating with time as reported by most of the published studies. The results of the current study are no exception. On the other hand, the rate of complications observed in our study was comparable or even lower than in similar studies. CONCLUSIONSDespite relatively worse results with prolonged follow-ups, the BSC remains a considerable part of the current orthopaedic armamentarium especially when extensive acetabular bone loss is countered. Loosening belongs to the most common complications of the BSC.

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