[Pedestal cup operation in acetabular defects after hip cup loosening. A progress report].

PURPOSE: An extreme extent of acetabular bone loss makes a primary stable cup fixation very difficult to achieve. No reliable operation method is as yet available. Defect filling with bone cement or bone grafts gives a high long-term failure rate. Further revisions are programmed.

METHODS: The titanium pedestal cup possibly offers a solution to these situations. It is fixed in the load-carrying upper vital part of the pelvis. A guide is necessary for this step. The tapered pedestal is reinforced by two large wings for rotational and structural stability. The physiological load transfer goes entirely through the pedestal. Thus, the cup serves only for articulation, sometimes without any contact to bone. Structural bone grafts are not implanted. Due to its modular length the pedestal very often allows a cup position at the original center of rotation.

RESULTS: A total of 139 pedestal cups have been implanted. Within a prospective study 51 hip revisions have been followed over 1-5 years. The indications include acetabular defects and resection arthroplasty. Implant related complications were few and consisted of a first generation screw failure and malpositioning of the pedestal.

CLINICAL RELEVANCE: After complete removal of all granulomatous tissue and restoration of physiological joint forces we observed early and spontaneous bone regeneration.

CONCLUSION: We doubt that a bony reconstruction exclusively happens after massive bone grafting. The acetabulum can recover even in catastrophic cases of pelvic discontinuity without allografts. Nearly all revision cases and rim defects can be managed with the pedestal cup.