The pillars of the scapula.

Total shoulder replacement has been shown to provide predictable pain relief and functional improvement in patients with glenohumeral arthritis. Loosening of the glenoid component remains the most frequent indication for revision surgery at long-term follow-up. The component most widely used is an all-polyethylene keeled or pegged design cemented to the glenoid cavity of the scapula. The glenoid is small and its cup-shaped morphology allows only a restricted site for limited fixation devices. This is particularly so in revision surgery where there are often large bony defects of the glenoid. In an anatomical study, we investigated the scapula in order to identify substantial bony pillars for better component fixation. Forty cadaveric shoulders (mean age 86, range 67-101) were dissected, the glenoids were denuded from cartilage, and the subchondral and cancellous bone was removed. Two bony pillars approaching the glenoid were consistently identified in all scapulae investigated. These pillars were outlined by three cortices and orientated to the circle formed by the rim of the inferior quadrants of the glenoid. One pillar is directed inferiorly near the margo lateralis and the other pillar is directed superiorly into the spine of the scapula. We defined these pillars in length and direction, and three-dimensionally located them in relation to the joint surface. This study demonstrated two bony pillars as important anatomical landmarks in the scapula. They were constant in presence, surgically accessible, and have not been described before. These results can be used as a guideline in the development of prosthetic designs to improve the fixation of glenoid components.