Improved Outcomes Following Arthroscopic Superior Capsular Reconstruction May Not Be Associated With Changes in Shoulder Kinematics: An In Vivo Study

Middle trapezius tendon transfer using Achilles allograft for irreparable isolated supraspinatus tendon tears effectively restores the superior stability of the humeral head without restricting range of motion: a biomechanical study

BACKGROUND

Middle trapezius tendon (MTT) transfer has been suggested for promising treatment of irreparable isolated supraspinatus tendon tears (IISTTs). However, there have been no attempts to assess the biomechanical efficacy of MTT transfer. This study aims to evaluate the biomechanical efficacy of MTT transfer in the setting of IISTTs.

METHODS

Eight fresh frozen cadaveric shoulders were tested in 3 conditions: (1) intact rotator cuff, (2) IISTT, and (3) MTT transfer using Achilles allograft for IISTTs. Total humeral rotational range of motion (ROM), superior translation of the humeral head, and subacromial contact characteristics were measured at 0°, 20°, and 40° glenohumeral abduction (representing 0°, 30°, and 60° shoulder abduction). Superior translation and subacromial contact pressures were measured at 0°, 30°, 60°, and 90° external rotation (ER). Two different MTT muscle loading conditions were investigated. A linear mixed effects model and Tukey post hoc test were used for statistical analysis.

RESULTS

Total ROM was significantly increased after IISTT at 20° abduction (P = .037). There were no changes in total ROM following MTT transfer compared to the IISTT condition (P > .625 for all comparisons). The IISTT condition significantly increased superior translation compared to the intact rotator cuff condition in 0° and 20° abduction with all ER angles (P < .001), 40° abduction-30° ER (P = .016), and 40° abduction-60° ER (P = .002). MTT transfer significantly decreased superior translation of the humeral head at all abduction angles compared to the IISTT condition (P < .026). MTT transfer significantly decreased peak contact pressure by 638.7 kPa (normal loading) and 726.8 kPa (double loading) at 0° abduction-30° ER compared to the IISTT condition (P < .001). Mean contact pressure was decreased by 102.8 kPa (normal loading) and 118.0 kPa (double loading) at 0° abduction-30° ER (P < .001) and 101.0 kPa (normal loading) and 99.2 kPa (double loading) at 0° abduction-60° ER (P < .001). MTT transfer at 20° abduction-30° ER with 24 N loading significantly decreased contact pressure by 91.2 kPa (P = .035).

CONCLUSIONS

The MTT transfer biomechanically restored the superior humeral head translation and reduced the subacromial contact pressure in a cadaveric model of IISTT, while not restricting total ROM. These findings suggest that MTT transfer may have potential as a surgical treatment for IISTTs.

Biomechanical Comparison Between Superior Capsular Reconstruction and Lower Trapezius Tendon Transfer in Irreparable Posterosuperior Rotator Cuff Tears

BACKGROUND

Superior capsular reconstruction (SCR) and lower trapezius tendon transfer (LTT) have recently been used to manage irreparable posterosuperior rotator cuff tears (PSRCTs). There has been a paucity of comparative biomechanical considerations between the 2 procedures.

PURPOSE

To compare the glenohumeral stability and biomechanical properties between SCR and LTT in PSRCTs involving the entire infraspinatus tendon region.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight fresh-frozen cadaveric shoulders were tested at 0°, 20°, and 40° of shoulder abduction. Maximum internal, external, and total humeral range of motion (ROM), superior translation of the humeral head, and subacromial contact characteristics were compared among 4 conditions: (1) intact rotator cuff, (2) PSRCTs involving the entire infraspinatus tendon region, (3) LTT using Achilles allograft (12 N and 24 N of loading), and (4) SCR using fascia lata allograft.

RESULTS

Although a decrease in total ROM was noted in LTT with 12 N compared with the tear condition, LTT with both 12 N and 24 N as well as SCR did not restrict total rotational ROM compared with the intact condition. LTT had decreased total ROM compared with tear condition at 20° of abduction (P = .042), while no significant decrease was confirmed at all abduction angles after SCR. SCR and LTT with 24 N decreased superior translation compared with the PSRCT condition at 0° and 20° of abduction (P < .037) but not significantly at 40° of abduction, whereas LTT with a 24-N load decreased glenohumeral superior translation at all abduction angles (P < .039). Both SCR and LTT decreased subacromial contact pressure compared with the tear condition (P < .014) at all abduction angles. SCR decreased subacromial contact pressure at 0° and 40° of abduction (P = .019 and P = .048, respectively) compared with LTT with 12 N of loading, while there was no difference between SCR and LTT with 24 N of loading in all abduction angles. SCR increased the contact area compared with the PSRCT condition at all abduction angles (P < .023), whereas LTT did not increase the contact area.

CONCLUSION

SCR and LTT decreased glenohumeral superior translation and contact pressure compared with PSRCT conditions. The LTT was superior to SCR in terms of superior translation of the humeral head at a higher shoulder abduction angle, whereas the SCR showed more advantageous subacromial contact characteristics compared with LTT.

CLINICAL RELEVANCE

These biomechanical findings provide insights into these 2 fundamentally different procedures for the treatment of young and active patients with PSRCTs involving the entire infraspinatus tendon region.

Margin convergence vs. superior capsular reconstruction for massive irreparable rotator cuff tears: outcomes are equivalent unless there is preoperative pseudoparesis

BACKGROUND

Margin convergence (MC) and superior capsular reconstruction (SCR) are common treatment options for irreparable rotator cuff tears in younger patients, although they differ in associated costs and operative times. The purpose of this study was to compare range of motion, patient-reported outcomes (PROs), and reoperation rates following MC and SCR. We hypothesized superior outcomes after SCR relative to MC regarding functional outcomes, subjective measures, and reoperation rates.

METHODS

This was a multicenter retrospective review of 59 patients from 3 surgeons treating irreparable rotator cuff tears with either MC (n = 28) or SCR (n = 31) and minimum 1-year follow-up from 2014-2019. Visual analog scale (VAS) for pain, Subjective Shoulder Value (SSV), active forward flexion (FF), external rotation (ER), retear rate, and conversion rate to reverse shoulder arthroplasty were evaluated. t tests and χ2 tests were used for continuous and categorical variables, respectively (P < .05).

RESULTS

Baseline demographics, range of motion, and magnetic resonance imaging findings were similar between groups. Average follow-up was 31.5 months and 17.8 months for the MC and SCR groups, respectively (P < .001). The MC and SCR groups had similar postoperative FF (151° ± 26° vs. 142° ± 38°; P = .325) and ER (48° ± 12° vs. 46° ± 11°; P = .284), with both groups not improving significantly from their preoperative baselines. However, both cohorts demonstrated significant improvements in VAS score (MC: 7.3 to 2.5; SCR: 6.4 to 1.0) and SSV (MC: 54% to 82%; SCR: 38% to 87%). There were no significant differences in postoperative VAS scores, SSV, and rates of retear or rates of conversion to arthroplasty between the MC and SCR groups. In patients with preoperative pseudoparesis (FF < 90°), SCR (n = 9) resulted in greater postoperative FF than MC (n = 5) (141° ± 38° vs. 67° ± 24°; P = .002).

CONCLUSION

Both MC and SCR demonstrated excellent postoperative outcomes in the setting of massive irreparable rotator cuff tear, with significant improvements in PROs and no significant differences in range of motion. Specifically for patients with preoperative pseudoparesis, SCR was more effective in restoring forward elevation. Further long-term studies are needed to compare outcomes and establish appropriate indications.

Superior Capsular Reconstruction Versus Middle Trapezius Tendon Transfer for Isolated Irreparable Supraspinatus Tendon Tears: Static Versus Dynamic Reconstruction

BACKGROUND

Both superior capsular reconstruction (SCR) and middle trapezius tendon (MTT) transfer can be performed in nonarthritic young and active patients with isolated irreparable supraspinatus tendon tears (IISTTs). However, to our knowledge, no comparative clinical studies have been conducted on these procedures.

PURPOSE

To evaluate and compare the clinical and radiological outcomes of SCR and arthroscopic-assisted MTT transfer in patients with IISTTs.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 60 patients with IISTTs were categorized into 2 groups according to the surgical procedure-Group S underwent SCR (n = 34); Group M underwent MTT transfer (n = 26). The clinical outcomes included the visual analog scale score for pain, active shoulder range of motion, American Shoulder and Elbow Surgeons score, and University of California, Los Angeles, shoulder score. Radiological outcomes included the assessment of the acromiohumeral distance, progression of cuff tear arthropathy (Hamada grade), subacromial bone erosion, and graft failure.

RESULTS

The mean follow-up time was 39.3 ± 5.2 months (range, 26-59 months) and 37.6 ± 9.8 months (range, 27-54 months) in Group S and Group M, respectively. Significant improvements in clinical outcomes were observed in both groups, while the active forward flexion (148.2°± 24.1° vs 165.9°± 8.7°; P = .003) and abduction (131°± 37.3° vs 152.5°± 17.9°; P = .035) were significantly higher in Group M at the final follow-up. No significant differences were found in the postoperative Constant, American Shoulder and Elbow Surgeons, and University of California, Los Angeles, shoulder scores between the 2 groups. Radiologically, although no difference was found in the Hamada grade at the final follow-up between the 2 groups (P = .143), the rates of acromial wear (58.8% vs 15.4%; P < .001) and graft retear (47.1% vs 7.7%; P < .001) were significantly higher in Group S than in Group M.

CONCLUSION

Both SCR and MTT transfer improved the overall clinical outcomes of IISTTs postoperatively, whereas MTT transfer was superior to SCR in terms of active forward flexion and abduction range of motion. Although higher rates of graft failure and subacromial bone erosion were observed in Group S, no difference was found in the clinical scores between the 2 groups at the short-term follow-up. However, further well-structured, prolonged comparative trials should be conducted in the future.

Postoperative Graft Volume Reduction Is Associated With Inferior Clinical Outcomes of Superior Capsule Reconstruction Using an Acellular Dermal Matrix Allograft

PURPOSE

To evaluate whether postoperative graft volume reduction is associated with clinical outcomes after superior capsule reconstruction (SCR) and to identify factors related to graft volume change.

METHODS

Between May 2018 and June 2021, patients who underwent SCR with acellular dermal matrix allograft for irreparable rotator cuff tear with a minimum 1-year follow-up and who had intact graft continuity in postoperative 6-month magnetic resonance imaging were retrospectively reviewed. The lateral half to the medial half of the graft volume ratio was defined as lateral half graft volume ratio. The difference between the preoperative and postoperative lateral half graft volume ratio was defined as lateral half graft volume change. Patients were divided into 2 groups: those with preserved graft volume (group I) and those with reduced graft volume (group II). Intergroup differences in clinical and radiological characteristics were analyzed.

RESULTS

A total of 81 patients were included, with 47 (58.0%) in group I and 34 (42.0%) in group II. Group I showed significantly lower lateral half graft volume change (0.018 ± 0.064 vs 0.370 ± 0.177; P < .001) than group II. Group II showed significantly greater preoperative Hamada grade (1.3 ± 0.5 vs 2.2 ± 0.6, P < .001), an anteroposterior distance of the graft at the greater tuberosity (APGT) (30.3 ± 4.8 vs 35.2 ± 3.8, P < .001), and fatty infiltration of infraspinatus (2.3 ± 0.9 vs 3.1 ± 0.8, P < .001) and subscapularis (0.9 ± 0.9 vs 1.6 ± 1.3, P = .009) than group I. Group II had a significantly lower proportion of patients achieving MIC in Constant score than group I (70.2% vs 47.1%, P = .035). The Hamada grade, APGT, and fatty infiltration of infraspinatus and subscapularis were independent factors of graft volume change.

CONCLUSIONS

Although SCR improved pain and shoulder function, postoperative graft volume reduction was related to a lower rate of minimal important change achievement in the Constant score compared with preserved graft volume. The preoperative Hamada grade, APGT, and fatty infiltration of infraspinatus and subscapularis were associated with graft volume reduction.

LEVEL OF EVIDENCE

Level III, retrospective case-control study.

Editorial Commentary: Decreased Superior Capsular Reconstruction Postoperative Graft Volume Is More Common in Patients With Advanced Rotator Cuff Arthropathy and Is Associated With Inferior Outcome: Cause or Effect?

Recent research has investigated the impact of graft condition on the outcomes of shoulder superior capsular reconstruction for irreparable rotator cuff tears. A decreased lateral graft volume compared with the medial graft volume is more common in patients with rotator cuff arthropathy and is associated with inferior clinical outcomes. This would suggest that aside from simply failing at the suture-graft junction, grafts with thinner lateral segments may exhibit diminished biomechanical strength over time. This may explain, in part, the discrepancy in outcomes between thinned grafts and grafts with preservation of tissue thickness. However, a significant association is also shown between grafts with lateral thinning and factors that portend worse clinical outcomes, including a higher Hamada grade, larger anteroposterior distance of the graft spanning the greater tuberosity, increased fatty infiltration in the infraspinatus and subscapularis muscles, and higher rate of subscapularis retears postoperatively. This would suggest that reductions in graft volume may be a product of worse initial pathology, which in and of itself may explain the worse postoperative outcomes. Thus, it remains unclear whether the findings represent cause or effect.

Do Magnets Have the Potential to Serve as a Stabilizer for the Shoulder Joint in Massive Rotator Cuff Tears?: A Biomechanical Cadaveric Study

Background

Disruption of the rotator cuff muscles compromises concavity compression force, which leads to superior migration of the humeral head and loss of stability. A novel idea of using the magnetic force to achieve shoulder stabilization in massive rotator cuff tears (MRCTs) was considered because the magnets can stabilize two separate entities with an attraction force. This study aimed to investigate the biomechanical effect of the magnetic force on shoulder stabilization in MRCTs.

Methods

Seven fresh frozen cadaveric specimens were used with a customized shoulder testing system. Three testing conditions were set up: condition 1, intact rotator cuff without magnets; condition 2, an MRCT without magnets; condition 3, an MRCT with magnets. For each condition, anterior-posterior translation, superior translation, superior migration, and subacromial contact pressure were measured at 0°, 30°, and 60° of abduction. The abduction capability of condition 2 was compared with that of condition 3.

Results

The anterior-posterior and superior translations increased in condition 2; however, they decreased compared to condition 2 when the magnets were applied (condition 3) in multiple test positions and loadings (p < 0.05). Abduction capability improved significantly in condition 3 compared with that in condition 2, even for less deltoid loading (p < 0.05).

Conclusions

The magnet biomechanically played a positive role in stabilizing the shoulder joint and enabled abduction with less deltoid force in MRCTs. However, to ensure that the magnet is clinically applicable as a stabilizer for the shoulder joint, it is necessary to thoroughly verify its safety in the human body and to conduct further research on technical challenges.

Superior Capsular Reconstruction Partially Restores Native Glenohumeral Joint Loads In A Dynamic Biomechanical Shoulder Model

PURPOSE

To evaluate the effect of an irreparable posterosuperior rotator cuff tear (PSRCT) on glenohumeral joint loads and to quantify improvement following superior capsular reconstruction (SCR) using an acellular dermal allograft.

METHODS

Ten fresh-frozen cadaveric shoulders were tested using a validated dynamic shoulder simulator. A pressure mapping sensor was placed between the humeral head and glenoid surface. Each specimen underwent the following conditions: (1) native, (2) irreparable PSRCT, (3) SCR using a 3mm-thick acellular dermal allograft. Glenohumeral abduction angle (gAA) and superior humeral head migration (SM) were measured using 3D motion tracking software. Cumulative deltoid force (cDF) and glenohumeral contact mechanics, including contact area (gCA) and contact pressure (gCP), were assessed at rest,15°,30°,45°, and maximum angle of glenohumeral abduction.

RESULTS

The PSRCT resulted in a significant decrease of gAA along with an increase in SM, cDF, and gCP (P<.001, respectively). SCR did not restore native gAA (P<.001), however, SM was significantly reduced (P<.001). Further, SCR significantly reduced deltoid forces at 30° (P=.007) and 45° of abduction (P=.007) when compared to the PSRCT. SCR did not restore native cDF at 30°(P=.015), 45°(P<.001), and maximum angle (P<.001) of glenohumeral abduction. Compared to the PSRCT, SCR resulted in a significant decrease of gCP at 15°(P=.008), 30°(P=.002), and 45°(P=.006). However, SCR did not completely restore native gCP at 45° (P=.038) and maximum abduction angle (P=.014).

CONCLUSION

In this dynamic shoulder model, SCR only partially restored native glenohumeral joint loads. However, SCR significantly decreased glenohumeral contact pressure, cumulative deltoid forces, and superior migration, while increasing abduction motion, when compared to the posterosuperior rotator cuff tear.

CLINICAL RELEVANCE

These observations raise concerns regarding the true joint preserving potential of SCR for an irreparable posterosuperior rotator cuff tear, along with its ability to delay progression of cuff tear arthropathy and eventual conversion to reverse shoulder arthroplasty.

Management of Irreparable Posterosuperior Rotator Cuff Tears-A Current Concepts Review and Proposed Treatment Algorithm by the AGA Shoulder Committee

Posterosuperior rotator cuff tears range among the most common causes of shoulder complaints. While non-operative treatment is typically reserved for the elderly patient with low functional demands, surgical treatment is considered the gold standard for active patients. More precisely, an anatomic rotator cuff repair (RCR) is considered the most desirable treatment option and should be generally attempted during surgery. If an anatomic RCR is impossible, the adequate choice of treatment for irreparable rotator cuff tears remains a matter of debate among shoulder surgeons. Following a critical review of the contemporary literature, the authors suggest the following evidence- and experience-based treatment recommendation. In the non-functional, osteoarthritic shoulder, treatment strategies in the management of irreparable posterosuperior RCT include debridement-based procedures and reverse total shoulder arthroplasty as the treatment of choice. Joint-preserving procedures aimed at restoring glenohumeral biomechanics and function should be reserved for the non-osteoarthritic shoulder. Prior to these procedures, however, patients should be counseled about deteriorating results over time. Recent innovations such as the superior capsule reconstruction and the implantation of a subacromial spacer show promising short-term results, yet future studies with long-term follow-up are required to derive stronger recommendations.

Early Treatment of Shoulder Pathology Is Necessary but Not Enough Is Being Performed

Delayed treatment of shoulder instability results in bone loss requiring more-complicated surgery, in turn resulting in less-optimal outcomes. Similarly, delayed treatment of repairable rotator cuff tears results in irreparable tears requiring more-complicated surgery and resulting in less-optimal outcomes. Delayed treatment of shoulder pathology is a problem. Solutions include education and research investigation.

Kinematic coupling of the glenohumeral and scapulothoracic joints generates humeral axial rotation

Glenohumeral and scapulothoracic motion combine to generate humerothoracic motion, but their discrete contributions towards humerothoracic axial rotation have not been investigated. Understanding their contributions to axial rotation is important to judge the effects of pathology, surgical intervention, and physiotherapy. Therefore, the purpose of this study was to investigate the kinematic coupling between glenohumeral and scapulothoracic motion and determine their relative contributions towards axial rotation. Twenty healthy subjects (10 M/10F, ages 22-66) were previously recorded using biplane fluoroscopy while performing arm elevation in the coronal, scapular, and sagittal planes, and external rotation in 0° and 90° of abduction. Glenohumeral and scapulothoracic contributions towards axial rotation were computed by integrating the projection of glenohumeral and scapulothoracic angular velocity onto the humeral longitudinal axis, and analyzed using one dimensional statistical parametric mapping and linear regression. During arm elevation, scapulothoracic motion supplied 13-20° (76-94%) of axial rotation, mainly via scapulothoracic upward rotation. The contribution of scapulothoracic motion towards axial rotation was strongly correlated with glenohumeral plane of elevation during arm elevation. During external rotation, scapulothoracic motion contributed 10° (8%) towards axial rotation in 0° of abduction and 15° (15%) in 90° of abduction. The contribution of scapulothoracic motion towards humerothoracic axial rotation could explain the simultaneous changes in glenohumeral plane of elevation and axial rotation associated with some pathologies and surgeries. Understanding how humerothoracic motion results from the functional coupling of scapulothoracic and glenohumeral motions may inform diagnostic and treatment strategies by targeting the source of movement impairments in clinical populations.

Editorial Commentary: Clinical Improvements of Superior Capsular Reconstruction Are Not Due to Maintained Dynamic Acromiohumeral Distance

Biomechanical data often help inform clinical decision-making in orthopaedic surgery. However, there are times when the biomechanical data and clinical data do not align. This is seen in cases of statistical but clinically irrelevant differences. This is also seen at times in cases of demonstrated clinical improvements with a poorly understood mechanism. Superior capsular reconstruction has gained significant traction since the original description in 2012. It has taken a central role in the armamentarium of treatment options of irreparable rotator cuff tears. There is robust published literature on the time zero biomechanics of superior capsular reconstruction and its stabilizing effects on the glenohumeral joint, especially with regards to superior migration of the humeral head. There also is demonstrated good early patient-reported outcomes with superior capsular reconstruction. However, the cause and effect may not be as simple as the biomechanical studies may suggest, and the underlying mechanism of why the superior capsular reconstruction appears to improve early outcomes remains poorly understood. These mechanisms are important to understand in order to inform technique changes and improvements and help us optimize treatment of the patient with an irreparable rotator cuff tear.