GLENOID STRUCTURAL ANALYSIS: RELEVANCE TO ARTHROPLASTY

Total shoulder arthroplasty restores function in shoulders with end stage glenohumeral arthritis. The most common complication of arthroplasty is prosthesis loosening and glenoid prosthesis loosening occurs more frequently than humeral because of quantity and orientation of bone available for fixation. Increasing glenoid prosthesis longevity requires thorough understanding of scapula structure, especially glenoid morphology and bone density.The project aim was quantification of glenoid structure with specific relevance to improve arthroplasty. Detailed knowledge of glenoid's intra-articular geometry, subchondral structure, regional bone density and extra-articular relationships is needed for future prosthesis design optimization. Three-dimensional computer models were generated from CT images of 12 pairs of male cadaver scapulae aged 50.18 ± 11.77 years, and 8 pairs of female cadaver scapulae aged 60 ± 20.48 years. External glenoid morphological parameters measured included superior-inferior length, anterior-posterior width, and glenoid contour geometry (dimensions and angles). Internal morphological analysis included subchondral bone glenoid version measurement. Regional bone density measurements were made to determine glenoid cancellous bone distribution. Accuracy and reliability were defined using repeated measurements. The glenoid was pear shaped with superior-inferior length greater than anterior-posterior diameter. The inferior glenoid boundary was a 120° arc with average radius 11.2 ± 1.2 mm. The center of the arc (glenoid center) was located along the maximum superior-inferior length one-third this distance superior from infraglenoid tubercle and. Glenoid's articular surface version, and subchondral bone version averaged 2° ± 5°, and 1° ± 4° of retroversion, respectively. Highest density bone was in posterior glenoid, medium density anteriorly, and low density in central glenoid. Accuracy and reliability were defined as mean difference between repeated and original computer model measurement (0.5 ± 0.7 mm for lengths and 1.3° ± 4.4° for angles).3-D computer modeling permitted internal morphological analyses, which for the first time defined entire glenoid structure. External morphological and bone density measurements agreed with previously reported data. Advanced imaging and computer modeling tools enabled an accurate and reliable structural analysis of the complexly shaped glenoid. Work described in this project will be used for future studies whose goals are improved glenoid prosthesis and surgical instrumentation design