Distal Radius Allograft for Posterior Glenoid Bone Loss: A Cadaveric Graft Matching Study and Biomechanical Study

Abstract

Background:

Posterior glenoid reconstruction for shoulder instability is commonly performed with distal tibia allograft (DTA), but with variable results. Recent evidence shows that distal radius allograft (DRA) has a radius of curvature (ROC) that more closely matches that of the glenoid.

Hypothesis:

DRA would more closely match the posterior glenoid than DTA in ROC and bone mineral density (BMD), and DRA would have superior biomechanical characteristics in a posterior instability model.

Study Design:

Controlled laboratory study.

Methods:

Ten cadaveric shoulders, ankles, and wrists underwent computed tomography scans. ROC and BMD for the glenoid, DRA, and DTA were measured. Biomechanical analysis was performed for each shoulder by translating the humerus 10 mm posterior-inferiorly relative to the glenoid and recording the maximum force (N) required and lateral displacement (mm) of the humeral head. Five conditions were tested for each shoulder: intact, posterior capsulolabral tear, 30% glenoid bone loss, DRA, and DTA.

Results:

Ten shoulders were tested (mean age, 58.1 years [SD, 5.9 years]). The mean anterior-posterior ROC was 31.1 mm (SD, 6.9 mm) for the glenoid, compared to 14.0 mm (SD, 1.9 mm; P < .0001) for DRA, and 68.2 mm (SD, 29.1 mm; P < .0001) for DTA. The mean superior-inferior ROC was 30.2 mm (SD, 3.7 mm) for the glenoid, compared to 30.7 mm (SD, 3.2 mm; P = .901) for DRA, and 23.5 mm (SD, 5.4 mm, P < .001) for DTA. For biomechanical testing, DRA demonstrated increased resistance to force compared with the instability and bone loss states (42.1 N [SD, 14.3 N] vs capsulolabral tear 21.5 N [SD, 17.9 N; P = .002] and bone loss 14.3 N [SD, 7.8 N; P < .001], respectively). However, DRA showed no significant difference in force resistance when compared with DTA (36.3 N [SD, 9.3 N]; P = .362).

Conclusion:

The native glenoid ROC and BMD are more comparable with DRA than DTA. The DRA restores posterior forces comparable to those of the native glenoid and did not result in significantly greater resistance forces when compared with DTA.

Clinical Relevance:

These anatomic data support DRA use in posterior glenoid reconstruction.