Proximally Coated Ingrowth Prostheses

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Abstract
Proximally coated femoral components for cementless total hip replacement were conceived in the early 1980s in response to the proximal stress shielding that was seen with extensively coated devices. The main purpose of this study was to analyze whether these prostheses remain viable options based on the results of presently used devices, while detailing the problems encountered with first generation devices. The evolution of these designs and how they were modified in response to early problems, was reviewed. Initial iterations were less successful because they were sometimes not stable, had problems with thigh pain, and progressive osteolysis. However, second generation devices with greater than 5 years clinical experience seem promising and have shown very low aseptic loosening rates (1%-3%), and less thigh pain (under 5% in most studies). The reader still must await longer term studies to know whether progressive osteolysis will be a problem. These encouraging midterm results can be attributed to improved geometry, instruments, and technique which ensure initial implant stability. Proximal coating must be circumferential, to seal the diaphysis from wear debris. After incorporating design changes in response to the significant failures of early devices, the concept of proximal coating for cementless femoral stems seems viable, as long as the twin requirements of circumferential coating and rigid initial stability are realized.