The Effect of Concavity Restoration on Glenohumeral Stability in a Glenoid Bone Loss Model: Comparing Distal Tibial Allograft Reconstruction to Classic Latarjet.

Abstract

Background: Distal tibial allograft (DTA) reconstruction for glenoid bone loss (GBL) has gained popularity. While recent studies have demonstrated that glenoid concavity is an important factor in native glenohumeral stability, there remains a paucity of data regarding concavity restoration during reconstructive procedures for GBL and its biomechanical effect.

Purpose: To compare the restoration of anterior glenohumeral stability and glenoid concavity after DTA and classic Latarjet procedures.

Study design: Controlled laboratory study.

Methods: Nine human cadaveric specimens (mean age, 62.2 years; range, 52-69 years) underwent pretesting computed tomography (CT) to assess native glenoid concavity as determined by the glenoid depth and bony shoulder stability ratio (BSSR). GBL was created so the DTA and Latarjet graft could restore 100% of the native glenoid width. The rotator cuff tendons were loaded, and anterior stability testing was performed using a KUKA robot to apply a controlled anterior force with the shoulder in 90° of abduction and neutral external rotation. A motion capture system recorded humeral head translation. The following conditions were tested: intact, soft tissue Bankart lesion; bone loss model with DTA reconstruction; classic Latarjet procedure without conjoint tendon loaded; and classic Latarjet procedure with conjoint tendon loaded (sling effect). All specimens underwent posttesting CT to measure the BSSR of the DTA and Latarjet reconstructions. A repeated-measures analysis of variance was performed to compare the BSSR and anterior translations between the DTA and Latarjet reconstructions.

Results: DTA produced greater concavity than the Latarjet procedure (BSSR: 0.45 vs 0.35; P < .001). There was no difference in anterior translation between the DTA and Latarjet procedures with the sling effect (5.1 mm vs 4.7 mm; P > .999). However, maximum anterior translation was decreased after the DTA procedure when compared with the Latarjet technique without the sling effect (5.1 mm vs 10.3 mm; P = .045).

Conclusion: DTA produces a more concave reconstruction and decreased anterior translation compared with the flatter reconstruction produced by the classic Latarjet procedure without the sling effect. DTA and the classic Latarjet procedure with conjoint tendon loading, however, yielded equivalent reductions in anterior translation.

Clinical relevance: Distal tibial allograft reconstruction is a biomechanically equivalent alternative to the classic Latarjet due to the restoration of glenoid concavity in addition to glenoid width. Surgeons should consider the role of concavity when addressing glenohumeral instability with bone loss.