AJSM - 2026-04-04 - Journal Article
Restoring Glenoid Concavity: Angled Bone Blocks Provide Biomechanically Superior Function and Restore Glenohumeral Forces Over Flat Constructs in Glenoid Augmentation.
Bauer J, Rajan R, Singh R, Obopilwe E, Arciero R, Edgar C
Topics
Key Takeaway
A 30° angled distal tibial allograft restored glenohumeral contact forces to 86.6% of intact (62.17 N vs. 71.81 N) and distraction forces to 98.5% of intact, significantly outperforming flat graft placement in a 20% anterior glenoid defect model.
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Summary
This study compared biomechanical performance of flat versus 30° angled distal tibial allograft reconstruction in a standardized 20% anterior glenoid bone defect across 9 cadaveric shoulders. Angled constructs restored distraction forces to 98.5% of intact (45.64 N) versus 89.6% for flat constructs (41.83 N), and contact forces to 86.6% of intact (62.17 N) versus 65.3% for flat constructs (46.91 N). Humeral head contact with the graft occurred in 100% of angled trials versus 70% of flat trials, and no statistically significant difference was found between the angled construct and the intact shoulder for distraction forces.
Key Limitation
A single 20% defect size was tested; the biomechanical advantage of angled versus flat constructs at smaller (<15%) or larger (>25%) defects—which carry different clinical decision thresholds—remains unknown.
Original Abstract
BACKGROUND
Surgical treatment of shoulder instability with glenoid bone loss using a distal tibial allograft has achieved success, with the bone graft placed parallel, flush, or recessed to the articular surface, but questions remain about optimal graft positioning.
HYPOTHESIS
Given evidence that glenoid concavity and congruence influence stability, we hypothesized that angled bone blocks better restore native concavity and biomechanics compared to flat graft placement.
STUDY DESIGN
Controlled laboratory study.
METHODS
A total of 9 cadaveric shoulders were dissected, separating rotator cuff muscles from the capsule. Native glenoid dimensions were measured with a digitizer. A 20% anterior bone defect was created and then reconstructed with a distal tibial allograft (bone graft). There were 4 conditions tested: intact, defect, flat bone block, and angled bone block (30°). Using a testing machine, the humeral head was translated anteriorly 10 mm, and distraction and contact forces were recorded.
RESULTS
Mean peak distraction forces were as follows: 48.28 ± 8.06 N (intact), 33.99 ± 10.54 N (defect; 70.4% of intact), 41.83 ± 9.07 N (flat; 89.6% of intact), and 45.64 ± 9.03 N (angled; 98.5% of intact). Humeral head contact with the graft occurred in 100.0% of angled trials versus 70.0% of flat trials. Mean glenohumeral contact forces were as follows: 71.81 ± 16.42 N (intact), 31.39 ± 16.60 N (defect), 46.91 ± 4.12 N (flat), and 62.17 ± 9.26 N (angled). One-way analysis of variance showed a significant effect of construct type on both contact and distraction forces ( P < .001). Pairwise comparisons showed significant differences in distraction forces between intact and defect conditions and between defect and angled bone block conditions. Comparisons also demonstrated significant differences in contact forces between intact and defect, intact and flat bone block, defect and flat bone block, defect and angled bone block, and flat bone block and angled bone block conditions. No significant difference was observed between the intact shoulder and angled bone block repair.
CONCLUSION
Angled bone blocks more closely restored native glenoid concavity and were biomechanically superior to flat bone blocks in re-establishing stability and centering the humeral head after glenoid bone loss.
CLINICAL RELEVANCE
This study provides a quantitative comparison between different bony glenoid augmentation methods.