The Effect of Concavity Restoration on Glenohumeral Stability in a Glenoid Bone Loss Model: Comparing Distal Tibial Allograft vs Medial Tibial Plateau Allograft vs Distal Clavicle Autograft

Abstract

Background:

Multiple grafts have been described for glenoid resurfacing in the setting of anterior shoulder instability with glenoid bone loss. The medial tibial plateau has been shown to have a similar radius of curvature to the glenoid and may be an appropriate anatomic match for glenoid resurfacing.

Purpose:

To evaluate restoration of glenoid concavity and anterior glenohumeral stability among the distal tibial allograft (DTA), distal clavicle autograft (DCA), and medial tibial plateau allograft (MTPA).

Study Design:

Controlled laboratory study.

Methods:

Nine sets of fresh-frozen unpaired shoulder, knee, and ankle cadaveric specimens were obtained (mean specimen age, 58.7 years; range, 51-63). Specimens underwent preoperative computed tomography to assess glenoid depth and radius to define the bony shoulder stability ratio (BSSR; glenoid depth over radius). A Kuka robot was used to assess shoulder stability with forces loaded through the rotator cuff and the shoulder in 90° of abduction and neutral rotation. Glenoid bone loss was created via a 10-mm cut, with each graft restoring 100% of the native glenoid width. The following conditions were tested: intact state followed by reconstructions with the DTA, MTPA, and DCA. Posttest computed tomography scans were obtained to calculate the reconstructed BSSR, and motion detectors were used to calculate maximum anterior humeral translation.

Results:

The BSSR was similar between the intact state (mean ± SD, 0.39 ± 0.11) and 3 reconstructed glenoid grafts (DCA, 0.46 ± 0.11 [P = .10]; MTPA, 0.43 ± 0.07 [P = .45]; DTA, 0.39 ± 0.11 [P = .21]). Maximum anterior translation did not differ between the 3 grafts (DCA, 6.4 ± 3.0 mm [P = .29]; MTPA, 8.4 ± 5.3 mm [P = .11]; DTA, 6.7 ± 3.6 mm [P = .21]) and the intact state (6.0 ± 2.8).

Conclusion:

By way of a cadaveric analysis, the DCA, MTPA, and DTA restored glenoid concavity to a point similar to the intact state. Future investigations with larger sample sizes are warranted to confirm these biomechanical trends and determine clinical significance.

Clinical Relevance:

Restoration of glenoid concavity is essential for achieving stability in patients with anterior shoulder instability and critical glenoid bone loss. This biomechanical study demonstrates that distal clavicle autograft, distal tibia allograft, and medial tibial plateau allograft each restore native glenoid concavity comparable to the intact state, supporting their use as reliable free bone block options for anatomic glenoid reconstruction. Future clinical studies are warranted to determine whether these biomechanical findings translate to improved clinical outcomes.