Moderate to large engaging Hill-Sachs defects: an in vitro biomechanical comparison of the remplissage procedure, allograft humeral head reconstruction, and partial resurfacing arthroplasty.

BACKGROUND: The management of engaging Hill-Sachs defects (HSD) is controversial. The purpose of this study was to biomechanically compare 3 treatment strategies.

MATERIALS AND METHODS: Eight specimens were tested on a shoulder simulator. The protocol involved testing 2 unrepaired HSD (30% and 45%), which were then treated with remplissage, humeral head allograft (HHA), and partial resurfacing arthroplasty (PRA). Stability (defect engagement and glenohumeral stiffness) and range of motion (ROM) were measured.

RESULTS: All 30% and 45% HSDs engaged and dislocated. Remplissage and HHA effectively prevented engagement in all specimens; however, 62% of PRA engaged. No repair exhibited stiffness significantly greater than intact, but 30% and 45% remplissage produced a 74% and 207% increase, respectively, and were significantly greater than the unrepaired states (P ≤ .047). Stiffness results for HHA and PRA closely matched those of intact. In adduction, remplissage reduced internal-external ROM compared with both defects (P ≤ .01), but only 30% remplissage caused a significant decrease compared with intact (P = .049). In abduction, all repairs reduced ROM compared with HSD (P ≤ .04), but none compared with intact (P ≥ 0.05). In extension, remplissage had significantly less ROM than either HHA or PRA (P ≤ .02).

CONCLUSION: All procedures improved stability; however, unlike remplissage, results from HHA and PRA closely resembled intact. Remplissage (30% and 45%) improved stability and eliminated engagement but caused reductions in ROM. HHA and PRA re-established intact ROM, but PRA could not fully prevent engagement. The effects of each technique are not equivalent and further studies are required.