Abstract
Purpose
The management of moderate to large engaging Hill-Sachs lesions is controversial and surgical options include remplissage, allograft reconstruction, and partial resurfacing arthroplasty. Few in-vitro studies have quantified their biomechanical characteristics and none have made direct comparisons. The purpose of this study was to compare joint stability and range of motion (ROM) among these procedures using an in-vitro shoulder simulator. It was hypothesized that all procedures would prevent defect engagement, but allograft and partial resurfacing would most accurately restore intact biomechanics; while remplissage would provide the greatest stabilization, possibly at the expense of motion.
Method
Eight cadaveric shoulders were tested on an active in-vitro shoulder simulator. Each specimen underwent testing in 11 conditions: intact, Bankart lesion, Bankart repair, and two unrepaired Hill-Sachs lesions (30% & 45%) which were then treated with each of the three techniques. Anterior joint stability, ROM in extension and internal-external rotation, and glenohumeral engagement were assessed. Stability was quantified as resistance, in N/mm, to an anteriorly applied load of 70N.
Results
Remplissage significantly increased joint stiffness compared to both defects (6.43.8 N/mm, p=0.01) and the allograft and partial resurfacing (p <= 0.04). No technique significantly surpassed the stability of the intact state (p>0.05).
In adduction, the remplissage significantly reduced internal-external rotation compared to both defects (p <= 0.01), but only the 30% repair caused a significant change compared to the intact state (14.511.3 N/mm, p=0.05). In abduction, all repairs reduced rotation ROM compared to the Hill-Sachs defect (>= 8.24o, p <= 0.04), but none with respect to the intact condition (p >= 0.05).
Remplissage had significantly less extension than either resurfacing procedure (>= 15.4o, p <= 0.02) and resulted in a greater reduction in extension ROM for 45% defects compared to 30% defects (11.918.91, p=0.06). All unrepaired lesions engaged during extension. None of the remplissage or allograft reconstructions engaged, however, 75% of partial resurfacing arthroplasties partially engaged.
Conclusion
This study is the first biomechanical evaluation to directly compare three surgical procedures for engaging Hill-Sachs lesions. Each procedure enhanced stability; however, the enhancement provided by the resurfacing repairs more closely resembled the intact state. Remplissage of the 30% and the 45% defects improved stability and eliminated glenohumeral engagement but caused significant and progressive reductions in ROM. In comparison, both the allograft and partial resurfacing procedures re-established ranges of motion approaching those of the intact joint; however, the partial resurfacing could not fully prevent engagement. These findings indicate that the effects of each technique are not equivalent and further clinical and biomechanical studies are required.
