Rotator cuff tear reaching the superior half portion of the humeral head causes shoulder abduction malfunction

Abstract

Purpose To examine the biomechanical properties governing posterosuperior rotator cuf (RC) tear progression and dynamic shoulder abduction function, in the absence of excess loading. Methods Twelve freshly frozen cadaveric shoulders were evaluated via an established dynamic shoulder abduction stimulator. The shoulder abduction functions were primarily evaluated using subacromial contact pressure (SACP) during an abduction procedure, and subsequent middle deltoid force (MDF) under 5 conditions: (1) intact, (2) anterior 1/3 posterosuperior rotator cuf (PSRC) tear, (3) anterior 2/3 PSRC tear, (4) entire PSRC tear, and (5) global RC tear (tear involving the entire superior RC). Results No obvious diferences were observed in the peak MDF required for abduction, and in the peak SACP among the four PSRC tear statuses (49.8 ± 9.2 N, 0.39 ± 0.05 mPa [1/3 PSRC tear]; 49.3 ± 6.8 N, 0.40 ± 0.06 mPa [2/3 PSRC tear]; 51.6 ± 7.0 N, 0.44 ± 0.08 mPa [entire PSRC tear]), as well as intact statuses (48.3 ± 9.8 N, 0.40 ± 0.05 mPa). However, signiicant elevations in the peak MDF and peak SACP levels were observed among the four PSRC tear statuses and global RC tear (68.1 ± 9.3 N; 4.12 ± 1.50 mPa, P < 0.01). ConclusionIn the absence of excess loading, the biomechanical function of the shoulder was not impaired by a simple PSRC tear. However, once the tear size reached the half superior portion of the humeral head, the humeral head migrated to the surface of the subacromion, and this action markedly decreased shoulder abduction function.

Effect of Anterior Acromial Coverage on Functional and Radiological Outcomes After Arthroscopic Repair of Anteroposterior Massive Rotator Cuff Tears

“…Of note, the inclusion criteria of the present study were confined to AP-MRCTs, which were reportedly correlated with shoulder dysfunction and a poor prognosis. 17,40,51,52,60 Ernstbrunner et al 17,18 revealed that global extension of RCTs (no remaining rotator cuff attachment above the equatorial line of the humeral head) and the involvement of the inferior subscapularis tendon were strong predictors of chronic pseudoparalysis or pseudoparesis. Compared with anterosuperior and posterosuperior MRCTs, AP-MRCTs demonstrated higher GTE, GFII, and failure rate of arthroscopic rotator cuff repair (18%-56%).…”

Durable immunomodulatory hierarchical patch for rotator cuff repairing

“…Current therapeutic strategies often involve incorporating anti-inflammatory small molecules into scaffolds, using various techniques such as coatings or blending [ 15 , 16 ]. However, these compounds typically have a short half-life of about one week and are prone to accelerated release kinetics in the dynamic in vivo environment [ [17] , [18] , [19] ]. This rapid release hinders the sustained establishment of an anti-inflammatory niche, thereby impeding tissue regeneration [ [20] , [21] ].…”