Trudeau Maxwell T, Peters Jonathan J, Hawthorne Benjamin C, Wellington Ian J, LeVasseur Matthew R, Mancini Michael R, Obopilwe Elifho, Giacomo Giovanni Di, Cerciello Simone, Mazzocca Augustus D
Department of Orthopaedic Surgery, University of Connecticut School of Medicine, Farmington, Connecticut, USA.
Department of Shoulder Surgery, Concordia Hospital for Special Surgery, Rome, Italy.
Orthop J Sports Med. 2022 Sep 26;10(9):23259671221118943. doi: 10.1177/23259671221118943. eCollection 2022 Sep.
Acromioclavicular joint (ACJ) injuries are common, and many are adequately treated nonoperatively. Biomechanical studies have mainly focused on static ligamentous stabilizers. Few studies have quantified ACJ stabilization provided by the trapezius.
PURPOSE/HYPOTHESIS: To elucidate the stabilization provided by the trapezius to the ACJ during scapular internal and external rotation (protraction and retraction). It was hypothesized that sequential trapezial resection would result in increasing ACJ instability.
Controlled laboratory study.
A biomechanical approach was pursued, with 10 cadaveric shoulders with the trapezius anatomically force loaded to normal. The trapezius was then serially transected over 8 trials, which alternated between clavicular defects (CD) and scapular defects (SD); each sequential defect consisted of 25% of the clavicular or scapular trapezial attachment. After each defect, specimens were tested with angle-controlled scapular internal and external rotation (12°) with rotary torque measurements to evaluate ACJ stability.
The mean resistance in rotary torque for 12° of scapular internal rotation (protraction) with native specimens was 7.0 ± 2.0 N·m. Overall, internal rotation demonstrated a significant decrease in ACJ stability with trapezial injury ( < .001). Eight sequential defects resulted in the following significant percentage decreases in rotary torque from native internal rotation: 1.5% (25% CD; 0% SD), 5.6% (25% CD; 25% SD), 5.1% (50% CD; 25% SD), 6.5% (50% CD; 50% SD), 3.8% (75% CD; 50% SD), 7.1% (75% CD; 75% SD), 6.7% (100% CD; 75% SD), and 12.3% (100% CD 100% SD) ( < .001). The mean resistance in rotary torque for 12° of scapular external rotation (retraction) with native specimens was 7.1 ± 1.7 N·m. External rotation did not demonstrate a significant decrease in ACJ stability with trapezial injury ( = .596). The 8 sequential defects resulted in decreases in rotary torque from native external rotation of 0%, 3.8%, 4.0%, 3.2%, 3.5%, 3.4%, 4.2%, and 0.7%.
Trapezial injury resulted in increased instability in the setting of scapular internal rotation (protraction) of the ACJ.
These findings validate the inclusion of deltotrapezial fascial injury consideration in the modified Rockwood classification system. Repair of the trapezial insertion on the ACJ may provide improved outcomes in the setting of ACJ reconstruction.
肩锁关节（ACJ）损伤很常见，许多损伤通过非手术治疗即可得到充分处理。生物力学研究主要集中在静态韧带稳定结构上。很少有研究对斜方肌提供的肩锁关节稳定作用进行量化。
目的/假设：阐明在肩胛骨内旋和外旋（前伸和后缩）过程中斜方肌对肩锁关节的稳定作用。假设依次切除斜方肌会导致肩锁关节不稳定增加。
对照实验室研究。
采用生物力学方法，对10具尸体肩部进行研究，将斜方肌按解剖结构加载至正常力。然后在8次试验中依次切断斜方肌，试验在锁骨缺损（CD）和肩胛骨缺损（SD）之间交替进行；每个连续缺损由锁骨或肩胛骨斜方肌附着点的25%组成。每次缺损后，通过角度控制的肩胛骨内旋和外旋（12°）并测量旋转扭矩来测试标本，以评估肩锁关节的稳定性。
正常标本在肩胛骨内旋12°（前伸）时旋转扭矩的平均阻力为7.0±2.0 N·m。总体而言，随着斜方肌损伤，内旋时肩锁关节稳定性显著降低（P<0.001）。8个连续缺损导致与正常内旋相比旋转扭矩的显著百分比降低：1.5%（25% CD；0% SD）、5.6%（25% CD；25% SD）、5.1%（50% CD；
