Shoulder Positioning during Superior Capsular Reconstruction: Computational Analysis of Graft Integrity and Shoulder Stability

The shoulder position during fixation of the graft may be a key factor impacting the outcome of arthroscopic superior capsular reconstruction (ASCR) in irreparable rotator cuff tears (IRCTs). However, biomechanical evidence regarding this effect is lacking. The aim of this study was to evaluate the influence of the shoulder position during fixation of the graft on shoulder stability and graft tear risk in ASCR. A 3-D musculoskeletal model of the upper limb was modified to account for the fixation of the graft in ASCR, assuming a full-thickness tear of the supraspinatus tendon. The concomitant tenotomy of the long head of the biceps (LHB) tendon was also studied. The biomechanical parameters evaluated included the strain of the graft and the glenohumeral joint reaction force (GH JRF), which were used to evaluate graft integrity and shoulder stability, respectively. Fixation of the graft considering abduction angles greater than 15° resulted in a high risk for graft tearing when the arm was adducted to the side of the trunk. For abduction angles below 15°, the mean shoulder stability improved significantly, ranging between 6% and 20% (p < 0.001), compared with that in the preoperative condition. The concomitant tenotomy of the LHB tendon resulted in loss of stability when compared to ASCR with an intact LHB tendon. The position of the shoulder during fixation of the graft has a significant effect on shoulder stability and graft tear risk after ASCR in IRCTs. This study provides new and important information regarding the role of shoulder positioning during fixation of the graft.

Glenoid concavity has a higher impact on shoulder stability than the size of a bony defect

Purpose Surgical treatment of shoulder instability caused by anterior glenoid bone loss is based on a critical threshold of the defect size. Recent studies indicate that the glenoid concavity is essential for glenohumeral stability. However, biomechanical proof of this principle is lacking. The aim of this study was to evaluate whether glenoid concavity allows a more precise assessment of glenohumeral stability than the defect size alone. Methods The stability ratio (SR) is a biomechanical estimate of glenohumeral stability. It is defined as the maximum dislocating force the joint can resist related to a medial compression force. This ratio was determined for 17 human cadaveric glenoids in a robotic test setup depending on osteochondral concavity and anterior defect size. Bony defects were created gradually, and a 3D measuring arm was used for morphometric measurements. The influence of defect size and concavity on the SR was examined using linear models. In addition, the morphometrical-based bony shoulder stability ratio (BSSR) was evaluated to prove its suitability for estimation of glenohumeral stability independent of defect size. Results Glenoid concavity is a significant predictor for the SR, while the defect size provides minor informative value. The linear model featured a high goodness of fit with a determination coefficient of R2 = 0.98, indicating that 98% of the SR is predictable by concavity and defect size. The low mean squared error (MSE) of 4.2% proved a precise estimation of the SR. Defect size as an exclusive predictor in the linear model reduced R2 to 0.9 and increased the MSE to 25.7%. Furthermore, the loss of SR with increasing defect size was shown to be significantly dependent on the initial concavity. The BSSR as a single predictor for glenohumeral stability led to highest precision with MSE = 3.4%. Conclusion Glenoid concavity is a crucial factor for the SR. Independent of the defect size, the computable BSSR is a precise biomechanical estimate of the measured SR. The inclusion of glenoid concavity has the potential to influence clinical decision-making for an improved and personalised treatment of glenohumeral instability with anterior glenoid bone loss.

Improved shoulder stability through plyometric, proprioceptive and strength exercises in rugby players. A randomized clinical trial

Background: The shoulder is one of the most frequently injured joints in rugby. Improving muscle strength can increase glenohumeral joint stability, thus preventing injuries to this joint. Purpose: Evaluating the effectiveness of a plyometric, proprioceptive and strength exercise program in promoting shoulder stability in rugby players. Study design: Randomized single blind clinical trial, with follow up. Level of evidence, 2. Methods: Thirty federated rugby players were included in the study and randomized to the two study groups. The experimental group performed an exercise program including plyometric exercises using a fitness ball, proprioceptive exercises with BodyBlade® and strength training with elastic bands. The intervention lasted four weeks, with two weekly sessions lasting 15 minutes each. The control group continued with their usual routine. The study variable was glenohumeral stability, measured with the Closed Kinetic Chain Upper Extremity Stability test and the Y-Balance test. Three evaluations (pre-treatment, post-treatment and follow-up) were carried out. Changes were calculated after each evaluation and repeated measures analysis was performed. Results: Stability improved after the intervention and when comparing pre-treatment and follow-up assessments (P < 0.05) in the experimental group. There were differences between the two groups (P < 0.05) and between the different study evaluations (P < 0.001). Conclusion: A protocol based on plyometric, proprioceptive and strength exercises improves glenohumeral stability. This improvement can be maintained for four weeks.

Rotator Cuff Repair Improves Clinical Function and Stability in Patients Older Than 50 Years With Anterior Shoulder Dislocations and Massive Rotator Cuff Tears

Background: Older patients with shoulder instability have a higher prevalence of rotator cuff tears and anterior capsular lesions. Simultaneous rotator cuff repair and labral repair are commonly performed to improve shoulder stability and function. Purpose: To investigate the clinical outcomes of arthroscopic rotator cuff repair for older patients with shoulder dislocations combined with massive rotator cuff tears and intact labral tissue. Study Design: Case series; Level of evidence, 3. Methods: A cohort consisting of 11 patients older than 50 years with shoulder dislocations and massive rotator cuff tears undergoing arthroscopic rotator cuff repair was identified between December 2015 and January 2018. Rotator cuff repair was performed after Bankart, superior labral anterior-posterior, and humeral avulsion of the glenohumeral ligament lesions were excluded during arthroscopic surgery. Preoperative and 12-month postoperative outcomes including modified University of California Los Angeles (UCLA), American Shoulder and Elbow Surgeons (ASES), Western Ontario Shoulder Instability Index (WOSI), and visual analog scale for pain scores as well as range of motion (ROM) were recorded. Results: The supraspinatus tendon was torn in all patients. Also, 36.4% of the patients had 3 rotator cuff tendons torn. For shoulder function, the preoperative UCLA score (12.1 ± 2.5 [range, 9-16]) and ASES score (35.4 ± 12.7 [range, 24-44]) significantly improved to 29.4 ± 4.3 (range, 24-35; P < .001) and 79.4 ± 16.0 (range, 45-95; P < .001), respectively, at 12 months postoperatively. None of the patients experienced shoulder redislocations at 12 months after surgery. For shoulder stability, the postoperative WOSI score (156.8 ± 121.0 [range, 45-365]) was significantly better than was the preoperative score (713.0 ± 238.6 [range, 395-1090]) ( P < .001). For comparisons between preoperative and postoperative ROM, forward flexion, abduction, and external and internal rotation at the side significantly improved. Conclusion: For patients older than 50 years with shoulder dislocations combined with massive rotator cuff tears and an intact labrum, arthroscopic rotator cuff repair alone achieved satisfactory functional outcomes and ROM without the recurrence of dislocations.