Recentering the humeral head does not necessarily improve glenohumeral abduction: A cadaveric biomechanical study.

Purpose: To explore if recentering the humeral head could improve shoulder abduction in shoulders with irreparable massive rotator cuff tears (IMRCTs).

Methods: Nine fresh-frozen cadaveric shoulders were used to simulate the intact condition and IMRCTs as controls. Four 'recenter' interventions were then sequentially applied: subacromial interposition (SI) using 4- and 8-mm spacers and superior capsule reconstruction (SCR) using two- and four-layer fascia lata grafts. Dynamic biomechanical experiments were performed for each condition. The primary outcomes were glenohumeral abduction angle (GAA). The secondary outcomes were acromiohumeral distance (AHD) and subacromial contact pressure.

Results: In the intact condition, the GAA was significantly greater compared to the IMRCT condition at most deltoid force levels (p < 0.05 for all except at 80 N). IMRCT significantly increased maximum contact pressure (MCP) compared to intact (Δ +0.09 MPa, p = 0.029). For recentering interventions, neither SI nor SCR improved GAA (p > 0.05). The 8-mm spacer and four-layer SCR condition significantly increased MCP compared to the intact condition (Δ +0.22 MPa, p = 0.048, Δ +0.24 MPa, p = 0.012, respectively).

Conclusion: Both SCR and SI could effectively recenter the humeral head, but neither technique improved shoulder abduction, with both even significantly increasing subacromial contact pressures. These findings suggest that surgical goals focusing solely on recentering humeral head may need re-evaluation, particularly, for patients with high functional demands on shoulder abduction.

Level of evidence: N/A.