A biomechanical analysis of rotator cuff deficiency in a cadaveric model

Fatigue-related changes in intermuscular electromyographic coherence across rotator cuff and deltoid muscles in individuals with and without subacromial pain

Neuromuscular fatigue induces superior migration of the humeral head in individuals with subacromial pain. This has been attributed to weakness of rotator cuff muscles and overactive deltoid muscles. Investigation of common inputs to motoneuron pools of the rotator cuff and deltoid muscles offers valuable insight into the underlying mechanisms of neuromuscular control deficits associated with subacromial pain. This study aims to investigate intermuscular coherence across the rotator cuff and deltoid muscles during a sustained submaximal isometric fatiguing contraction in individuals with and without subacromial pain. Twenty symptomatic and 18 asymptomatic young adults participated in this study. Surface electromyogram (EMG) was recorded from the middle deltoid (MD) and infraspinatus (IS). Intramuscular EMG was recorded with fine-wire electrodes in the supraspinatus (SS). Participants performed an isometric fatiguing contraction of 30° scaption at 25% maximum voluntary contraction (MVC) until endurance limit. Pooled coherence of muscle pairs (SS-IS, SS-MD, IS-MD) in the 2-5 Hz (delta), 5-15 Hz (alpha), and 15-35 Hz (beta) frequency bands during the initial and final 30 s of the fatigue task were compared. SS-IS and SS-MD delta-band coherence increased with fatigue in the asymptomatic group but not the symptomatic group. In the alpha and beta bands, SS-IS and SS-MD coherence increased with fatigue in both groups. IS-MD beta-band coherence was greater in the symptomatic than the asymptomatic group. Individuals with subacromial pain failed to increase common drive across rotator cuff and deltoid muscles and have altered control strategies during neuromuscular fatigue. This may contribute to glenohumeral joint instability and subacromial pain experienced by these individuals.NEW & NOTEWORTHY Through the computation of shared neural drive across glenohumeral muscles, this study reveals that individuals with subacromial pain were unable to increase shared neural drive within the rotator cuff and across the supraspinatus and deltoid muscles during neuromuscular fatigue induced by sustained isometric contraction. These deficits in common drive across the shoulder muscles likely contribute to the joint instability and pain experienced by these individuals.

Reduced retear rates yet similar clinical outcomes following arthroscopic partial repair of large and massive irreparable rotator cuff tears with biceps augmentation compared to repairs without biceps augmentation: A systematic review and meta-analysis

PURPOSE

To compare the clinical outcomes between arthroscopic partial rotator cuff repair with biceps augmentation (BA) and partial repair (PR) without BA.

METHODS

This systematic review included studies comparing outcomes of arthroscopic repair for large to massive irreparable rotator cuff tears with and without the BA. The focus was on postoperative clinical results and retear rates. Mean differences were used to express continuous outcomes, while odds ratios (ORs) were employed for dichotomous outcomes.

RESULTS

Ten studies (733 shoulders, all level 3 evidence) were included. The BA group showed a significant reduction in retear rates (OR = 0.40, 95% confidence interval [CI]: 0.20-0.77, P = 0.007) and comparable postoperative outcomes across various measures: American Shoulder and Elbow Surgeons (ASES) score, visual analogue scale for pain, University of California-Los Angeles shoulder score, active forward flexion motion and active external rotation at the arm-at-side position compared to the PR group. Subgroup analysis of two BA techniques-rerouting and supplementation following supraglenoid tenotomy-showed no significant differences in ASES score for either technique versus PR. However, rerouting significantly lowered retear rates (OR = 0.21, 95% CI: 0.12-0.36, p < 0.001), while supplementation showed similar retear rates to PR (OR = 0.87, 95% CI: 0.37-2.02, n.s.).

CONCLUSION

Arthroscopic partial rotator cuff repair with BA for large to massive irreparable rotator cuff tears is a reliable technique, resulting in improved postoperative outcomes. BA using supplementation following supraglenoid tenotomy showed similar clinical outcomes and range of motion but with lower retear rates compared to the PR group.

LEVEL OF EVIDENCE

Level III.

Influence of Critical Shoulder Angle and Rotator Cuff Tear Type on Load-Induced Glenohumeral Biomechanics: A Sawbone Simulator Study

Glenohumeral (GH) biomechanics after rotator cuff (RC) tears are not fully understood. The purpose of our study was to determine if the critical shoulder angle (CSA), type of RC tears, and level of weight bearing increase GH translation, instability based on the instability ratio, muscle forces and joint reaction force (JRF), and shifts the center of force (CoF) superiorly. A GH simulator with muscle-mimicking cable systems was used to simulate 30° abduction in the scapular plane. A Sawbone humerus and five specimen-specific scapular anthropometries were used to test six types of RC tears, three weight-bearing loads, and the native and adjusted (to different CSAs) deltoid origin sites. Linear mixed effects models (CSA, RC tear type, and weight bearing) with random effects (specimen and sex) were used to assess differences in GH biomechanics. With increasing CSA, GH translation increased, JRF decreased, and the CoF position was more inferior. RC tears did not significantly alter GH translation but shifted the CoF position superiorly, close to where glenoid erosion occurs in patients with RC tears with secondary osteoarthritis. Weight bearing significantly increased GH translation and JRF. RC and deltoid muscle forces increased with the presence of RC tears and increased weight bearing. The remaining RC muscles of intact tendons compensated for the torn RC tendons but not for the altered CoF position. GH translation remained comparable to shoulders with intact RC. These findings highlight the importance of early detection, clinical management, and targeted rehabilitation strategies for patients with RC tears.

Muscle and joint function in the rotator cuff deficient shoulder

Full-thickness rotator cuff tears can lead to poor coaptation of the humeral head to the glenoid, disrupting muscle forces required for glenohumeral joint stability, ultimately leading to joint subluxation. The aim of this study was to evaluate muscle forces and glenohumeral joint translations during elevation in the presence of isolated and combined full-thickness rotator cuff tears. Eight fresh-frozen upper limbs were mounted to a computer-controlled testing apparatus that simulated joint motion by simulated muscle force application. Scapular-plane abduction was performed, and glenohumeral joint translations were measured using an optoelectronic system. Testing was performed in the native shoulder, a following an isolated tear to the supraspinatus, as well as combined tears involving the supraspinatus and subscapularis, as well as supraspinatus, infraspinatus, and teres minor. Rotator cuff tears significantly increased middle deltoid force at 30°, 60°, and 90° of abduction relative to that in the native shoulder (p < 0.05). Significantly greater superior translations were observed relative to the intact shoulder due to combined tears to the supraspinatus and infraspinatus at 30° of abduction (mean increase: 1.6 mm, p = 0.020) and 60° of abduction (mean increase: 4.8 mm, p = 0.040). This study illustrates the infraspinatus-teres minor complex as a major humeral head depressor and contributor to glenohumeral joint stability. An increase in deltoid force during abduction occurs in the presence of rotator cuff tears, which exacerbates superior migration of the humeral head. The findings may help in the development of clinical tests in rotator cuff tear diagnostics, in surgical planning of rotator cuff repair, and in planning of targeted rehabilitation.

Effects of arthroscopic rotator cuff repair on isokinetic muscle function 6 months following surgery: influence of tear type, tear size, and tendon retraction

BACKGROUND

Rotator cuff tears are a common musculoskeletal condition which can lead to functional limitations and impairments in quality of life. The purpose of the present study was to investigate the effects of arthroscopic repair surgery on isokinetic muscle function before and 6-months after surgery. Additionally, the mediating effects of tear type, tear size and tendon retraction were examined.

METHODS

Data from n = 67 patients (56 ± 9 years) with full-thickness rotator cuff tears were analyzed. Before and 6-months after surgery, isokinetic muscle function in external/internal rotation and abduction/adduction movements was assessed. Further, tear size, tear type (Collin classification) and tendon retraction (Patte classification) were analyzed using magnetic resonance imaging.

RESULTS

After statistical analysis, a significant increase in limb symmetry index of external (P < .001), internal rotation (P < .01), abduction (P < .001), and adduction (P < .001) were observed from preto postsurgery. The results revealed that tear size and tendon tear type significantly mediated the functional outcome, with no significant effect of tendon retraction.

CONCLUSION

The present findings point toward the notion that the functional outcome following rotator cuff repair was significantly dependent on tear type and tear size but not tendon retraction. Patients with larger sized tears presented pronounced deficits following 6-months indicating that rehabilitation times need to be adjusted accordingly.

Joint-preserving treatment for global irreparable rotator cuff tears: combined anterior Latissimus dorsi and Teres major tendon transfer

INTRODUCTION

Treating global irreparable rotator cuff tears (GIRCTs) that involve both antero-and postero-superior cuff tendon tears could be a challenging problem. There has been limited joint-preserving treatment options in high-demand patients with minimal glenohumeral arthritis. The study aims to assess the clinical outcome of combined anterior latissimus dorsi and teres major tendon (aLDTM) transfer for patients with both GIRCTs and minimal glenohumeral arthritis.

MATERIALS AND METHODS

This retrospective study included patients who underwent combined aLDTM transfer for GIRCTs between 2018 May and 2020 October. Clinical outcomes include pain VAS, Constant, American Shoulder and Elbow Society (ASES), University of California Los Angeles (UCLA), activities of daily living requiring active internal rotation (ADLIR) score, active range of motion (aROM), strength, rates of pseudoparalysis or pseudoparesis reversal and return to work. Radiographic assessment included the acromiohumeral distance (AHD), Hamada grade, and transferred tendon integrity at final follow-up.

RESULTS

23 patients (mean age: 64.7 ± 5.9 years [55-74]) were included and the mean follow-up period was 28.2 ± 4.3 [24‒36] months. Postoperatively, VAS, Constant, ASES, UCLA, and ADLIR scores significantly improved at final follow-up (P < .001). Postoperative aROM was significantly improved in forward elevation (FE) to 129° ± 29°, abduction (ABD) to 105° ± t3°, and internal rotation (IR) at back to 5.9 ± 2.5. Strength of both FE and IR were also significantly improved (P < .001). Patients with preoperative pseudoparalysis (2 of 4 patients) and pseudoparesis (6 of 6 patients) experienced a reversal. No significant change in AHD and hamada grade was confirmed at final follow-up. 3 patients experienced partial tear of the transferred tendon.

CONCLUSIONS

In this study, we found significant improvement in clinical outcomes with no significant progression of arthritis by final follow-up. The aLDTM transfer could be an alternative choice of joint-preserving treatment option for young and active patients with GIRCTs and minimal glenohumeral arthritis. However, large and long-term studies should be conducted to establish its adequacy.

STUDY DESIGN

Case series.

LEVEL OF EVIDENCE

IV.

Differences in Osseous Shoulder Morphology, Scapulothoracic Orientation, and Muscle Volume in Patients With Constitutional Static Posterior Shoulder Instability (Type C1) Compared With Healthy Controls

BACKGROUND

Constitutional static posterior humeral decentering (type C1 according to ABC Classification) has been recognized as a pre-osteoarthritic deformity that may lead to early-onset posterior decentering osteoarthritis at a young age. Therefore, it is important to identify possible associations of this pathologic shoulder condition to find more effective treatment options.

PURPOSE

To perform a comprehensive analysis of all parameters reported to be associated with a C1 shoulder-including the osseous shoulder morphology, scapulothoracic orientation, and the muscle volume of the shoulder girdle in a single patient cohort.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A retrospective, comparative study was conducted analyzing 17 C1 shoulders in 10 patients who underwent magnetic resonance imaging (MRI) with the complete depiction of the trunk from the base of the skull to the iliac crest, including both humeri. The mean age of the patients was 33.5 years, and all patients were men. To measure and compare the osseous shoulder morphology (glenoid version, glenoid offset, humeral torsion, anterior acromial coverage, posterior acromial coverage, posterior acromial height, and posterior acromial tilt) and scapulothoracic orientation (scapular protraction, scapular internal rotation, scapular upward rotation, scapular translation, scapular tilt, and thoracic kyphosis), these patients were matched 1 to 4 according their age, sex, and affected side with shoulder-healthy patients who had received positron emission tomography (PET)-computed tomography. To measure and compare the muscle volume of the shoulder girdle (subscapularis, infraspinatus/teres minor, supraspinatus, trapezius, deltoid, latissimus dorsi/teres major, pectoralis major, and pectoralis minor), patients were matched 1 to 2 with patients who had received PET-MRI. Patients with visible pathologies of the upper extremities were excluded.

RESULTS

The C1 group had a significantly higher glenoid retroversion, increased anterior glenoid offset, reduced humeral retrotorsion, increased anterior acromial coverage, reduced posterior acromial coverage, increased posterior acromial height, and increased posterior acromial tilt compared with controls (P < .05). Decreased humeral retrotorsion showed significant correlation with higher glenoid retroversion (r = -0.742; P < .001) and higher anterior glenoid offset (r = -0.757; P < .001). Significant differences were found regarding less scapular upward rotation, less scapular tilt, and less thoracic kyphosis in the C1 group (P < .05). The muscle volume of the trapezius and deltoid was significantly higher in the C1 group (P < .05).

CONCLUSION

Patients with C1 shoulders differ from healthy controls regarding osseous scapular and humeral morphology, scapulothoracic orientation, and shoulder girdle muscle distribution. These differences may be crucial in understanding the delicate balance of glenohumeral centering.

The influence of rotator cuff tear type and weight bearing on shoulder biomechanics in an ex vivo simulator experiment

Glenohumeral biomechanics after rotator cuff (RC) tears have not been fully elucidated. This study aimed to investigate the muscle compensatory mechanism in weight-bearing shoulders with RC tears and asses the induced pathomechanics (i.e., glenohumeral translation, joint instability, center of force (CoF), joint reaction force). An experimental, glenohumeral simulator with muscle-mimicking cable system was used to simulate 30° scaption motion. Eight fresh-frozen shoulders were prepared and mounted in the simulator. Specimen-specific scapular anthropometry was used to test six RC tear types, with intact RC serving as the control, and three weight-bearing loads, with the non-weight-bearing condition serving as the control. Glenohumeral translation was calculated using instantaneous helical axis. CoF, muscle forces, and joint reaction forces were measured using force sensors integrated into the simulator. Linear mixed effects models (RC tear type and weight-bearing) with random effects (specimen and sex) were used to assess differences in glenohumeral biomechanics. RC tears did not change the glenohumeral translation (p > 0.05) but shifted the CoF superiorly (p ≤ 0.005). Glenohumeral translation and joint reaction forces increased with increasing weight bearing (p < 0.001). RC and deltoid muscle forces increased with the presence of RC tears (p ≤ 0.046) and increased weight bearing (p ≤ 0.042). The synergistic muscles compensated for the torn RC tendons, and the glenohumeral translation remained comparable to that for the intact RC tendons. However, in RC tears, the more superior CoF was close to where glenoid erosion occurs in RC tear patients with secondary osteoarthritis. These findings underscore the importance of early detection and precise management of RC tears.

Proximal Humerus Reconstruction for Bone Sarcomas: A Critical Analysis

» The proximal humerus is a common location for primary bone tumors, and the goal of surgical care is to obtain a negative margin resection and subsequent reconstruction of the proximal humerus to allow for shoulder function.» The current evidence supports the use of reverse total shoulder arthroplasty over hemiarthroplasty when reconstructing the proximal humerus after resection of a bone sarcoma if the axillary nerve can be preserved.» There is a lack of high-quality data comparing allograft prosthetic composite (APC) with endoprosthetic reconstruction of the proximal humerus.» Reverse APC should be performed using an allograft with donor rotator cuff to allow for soft-tissue repair of the donor and host rotator cuff, leading to improvements in shoulder motion compared with an endoprosthesis.

Relative contributions of the supraspinatus cord and strap tendons to shoulder abduction and translation

BACKGROUND

The supraspinatus (SS) is formed by a larger anterior bipennate muscle with a cord-like tendon and a posterior unipennate muscle with a strap-like tendon. There is a tendinous connection between the 2 SS subunits. Yet, the relative mechanical contribution of the SS cord and SS strap musculotendinous units to load transmission and subsequent shoulder abduction force is unknown. We hypothesized that a simulated SS cord vs. an SS strap tear would generate less shoulder abduction force and, further, an intact SS cord would offset the expected abduction loss from an SS strap tear, but the inverse would not be true.

MATERIALS AND METHODS

Twenty fresh-frozen cadaveric specimens were tested in a shoulder simulator with physiological load vectors applied to the upper and lower subscapularis, SS cord, SS strap, infraspinatus, and teres minor. The roles of the SS cord and SS strap muscles were delineated by varying their loads, while keeping constant loads on other muscles. The randomized testing trials included a native condition and 4 test cases that simulated tears by dropping the load and force transfer via the SS cord-to-SS strap connection by adding the load. Testing was completed at both 0° and 30° of abduction. During each test, shoulder abduction force, rotator cuff strains, and humeral translation were measured.

RESULTS

Simulated isolated SS cord and SS strap tears led to a significantly lower shoulder abduction force (P < .001). A simulated cord tear at 0° and 30° reduced the abduction force by 53% and 38%, respectively. A simulated strap tear at 0° and 30° dropped the abduction force by 27% and 23%, respectively. The decline in the abduction force was larger for the SS cord tear vs. SS strap tear (P ≤ .001). An SS cord tear with full-load transfer to the strap was able to recover to native values at both 0° and 30° (P ≥ .288). Likewise, an SS strap tear with full-load transfer to the SS cord showed a similar recovery to native values at both 0° and 30° (P ≥ .155). During full-load transfer, the tendon strain followed the loading pattern. An SS cord tear or SS strap tear did not cause a change in humeral translation (P ≥ .303).

DISCUSSION

The mechanical findings support the efficacy of nonoperative treatment of small (<10 mm) SS tears,11 because an intact SS strap tendon can effectively offset the abduction loss of a torn SS cord tear and vice versa.

Arthroscopic superior capsule reconstruction augmentation using a semitendinosus autograft in massive reparable rotator cuff tears

Background

Arthroscopic superior capsule reconstruction (SCR) augmentation is a viable treatment option for massive reparable cuff tears. This study aimed to retrospectively compare clinical and imaging outcomes of patients with reparable massive rotator cuff tears after arthroscopic rotator cuff repair (ARCR) with those after SCR augmentation using a semitendinosus autograft.

Methods

We retrospectively compared 50 patients with massive reparable rotator cuff tears who underwent ARCR and SCR augmentation (n = 25 each). Patients were clinically followed up for at least 2 years, and the American Shoulder and Elbow index, other patient-reported outcomes, active range of motion, and radiography and magnetic resonance imaging findings were assessed.

Results

At the final follow-up, both patient groups showed significant improvements in forward elevation in range of motion and visual analog scale scores. Improvements in the American Shoulder and Elbow scores in the SCR augmentation group were significantly superior to those in the ARCR group (48.3 and 28.9, P < .01). There was a significant difference in the retear rate between the SCR augmentation group and ARCR group (20% and 56%, respectively; P = .009).

Conclusion

Our study demonstrated that patient-reported outcomes and retear rates in patients who underwent SCR augmentation with rotator cuff repair for massive rotator cuff tears significantly improved compared with those in patients who underwent ARCR without augmentation. Augmentation with semitendinosus autografting during rotator cuff repair represents a solution for patients with massive reparable rotator cuff tears.

Effect of subscapularis repair on joint contact forces based on degree of posterior-superior rotator cuff tear severity in reverse shoulder arthroplasty

Massive irreparable rotator cuff tears (RCTs) affect the clinical outcomes of reverse shoulder arthroplasty (RSA). However, the effects of subscapularis repair on the outcomes of RSA, based on the degree of posterior-superior RCTs, are unclear. This study aimed to examine the effect of subscapularis repair on three-dimensional joint contact forces (JCFs) based on the degree of posterior-superior RCT severity in RSA. Ten human in vivo experimental data were used as input to the musculoskeletal model. A six-degrees-of-freedom (DOF) anatomical shoulder model was developed and validated against three-dimensional JCFs. The 6-DOF musculoskeletal shoulder model of RSA was then developed by importing the reverse shoulder implant into the validated anatomical shoulder model. Based on the various types of posterior-superior RCT severity, inverse dynamic simulations of subscapularis-torn and subscapularis-repaired models of RSA were performed: from isolated supraspinatus tears to partial or massive tears of the infraspinatus and teres minor. The intact rotator cuff model of RSA was also simulated for comparison with the different types of models. Our results showed that the more posterior-superior RCTs progressed in RSA, the more superior JCFs were observed at 90°, 105°, and 120° abduction in the subscapularis-torn model. However, subscapularis repair decreased the superior JCF at those angles sufficiently. In addition, the teres minor muscle-tendon force increased as infraspinatus bundle tears progressed in both the subscapularis-torn and -repaired models, in order to compensate for the reduced force during abduction. However, the teres minor muscle-tendon force was not as high as that of the infraspinatus muscle-tendon, which could result in muscle force imbalance between repaired subscapularis and teres minor. Therefore, our results suggest that repairing the subscapularis and the repairable infraspinatus during RSA can improve glenohumeral joint stability in the superior-inferior direction by restoring muscle force balance between the anterior cuff (i.e., subscapularis) and posterior cuff (i.e., infraspinatus and teres minor). The findings of this study can help clinician decide whether to repair the rotator cuff during RSA to enhance joint stability.

Superior capsular reconstruction for irreparable rotator cuff tear: a review of current methods

Irreparable massive rotator cuff tears can significantly impact daily life; and these types of tears can be difficult to repair completely, especially in younger patients who are more active and have higher functional requirements. Since its introduction by Mihata and the colleagues, superior capsular reconstruction (SCR) has gained popularity in the treatment of irreparable massive rotator cuff tears and has shown promising short-term results. A variety of studies have focused on the clinical and biomechanical outcomes of this procedure. This article reviews the biomechanics, indications for the surgical procedure, graft options, surgical technique, and rehabilitation from SCR.

Greater tuberosity morphology is altered in individuals with symptomatic isolated supraspinatus tendon tears

BACKGROUND

In the presence of an isolated supraspinatus tear, the force applied to the greater tuberosity is reduced, which may lead to bony morphologic changes. Thus, diagnostic or surgical identification of landmarks to properly repair the torn tendon might be difficult if the anatomy of the greater tuberosity is altered. The objectives of the study were to assess the presence of the superior, middle, and inferior facets of the greater tuberosity in individuals with symptomatic isolated supraspinatus tendon tears and the associations between tear size, tear location and presence of each facet.

METHODS

Thirty-seven individuals with symptomatic isolated supraspinatus tendon tears were recruited to participate in the study. Individuals underwent a high-resolution computed tomography scan of the involved shoulder and images were segmented to generate subject specific models of each humerus. The vertices comprising each facet were identified; however, if even a single vertex comprising the facet was missing, the facet was considered altered. Percentage agreement for correctly identifying the presence of each facet was determined using 2 additional observers and 5 randomly selected humeri. Ultrasonography was performed to assess anterior-posterior (AP) tear size and tear location. Outcome parameters included presence of the superior, middle, and inferior facets; AP tear size; and tear location. Point-biserial correlations were used to determine the associations between AP tear size, tear location, and presence of the superior, middle, and inferior facets.

RESULTS

Supraspinatus tear size and tear location was 13.1 ± 6.1 mm (range, 1.9-28.3 mm) and 2.0 ± 4.4 mm from the posterior edge of the long head of the biceps tendon (range, 0.0-19.0 mm), respectively. Overall, the superior, middle, and inferior facets were not altered in 24.3%, 29.7%, and 45.9% of individuals, respectively. Percentage agreement between observers was 83.4% on average. No associations were found between tear size or tear location and presence of the superior, middle, or inferior facet (P values ranged from .19 to .74).

CONCLUSION

Individuals with symptomatic isolated supraspinatus tears experience significant alterations in the bony morphology of the greater tuberosity that were irrespective of supraspinatus tear size and location. This information is useful for radiologists and orthopedic surgeons as the altered anatomy may influence the ability to identify important anatomic landmarks during diagnostic imaging or surgical procedures.

A comparative probabilistic analysis of human and chimpanzee rotator cuff functional capacity

Computational musculoskeletal modeling represents a valuable approach to examining biological systems in physical anthropology. Probabilistic modeling builds on computational musculoskeletal models by associating mathematical distributions of specific musculoskeletal features within known ranges of biological variability with functional outcomes. The purpose of this study was to determine if overlap in rotator cuff muscle force predictions would occur between species during the performance of an evolutionarily relevant horizontal bimanual arm suspension task. This necessitated creating novel probabilistic models of the human and chimpanzee glenohumeral joint through augmentation of previously published deterministic models. Glenohumeral musculoskeletal features of anthropological interest were probabilistically modeled to produce distributions of predicted human and chimpanzee rotator cuff muscle force that were representative of the specific anatomical manipulations. Musculoskeletal features modeled probabilistically included rotator cuff origins and deltoid insertion, glenoid inclination, and joint stability. Predicted human rotator cuff muscle force distributions were mostly limited to alternating between infraspinatus and teres minor, with both 100% and 0% muscle force predicted for both muscles. The chimpanzee model predicted low-to-moderate muscle force across all rotator cuff muscles. Rotator cuff muscle force predictions were most sensitive to changes of muscle origins and insertions. Results indicate that functional rotator cuff overlap is unlikely between chimpanzees and humans without greater modifications of the glenohumeral musculoskeletal phenotypes. The results also highlight the low efficacy of the human upper extremity in overhead, weight-bearing tasks, and propensity for rotator cuff injury.

Ex vivo experimental strategies for assessing unconstrained shoulder biomechanics: A scoping review

BACKGROUND

Biomechanical studies of the shoulder often choose an ex vivo approach, especially when investigating the active and passive contribution of individual muscles. Although various simulators of the glenohumeral joint and its muscles have been developed, to date a testing standard has not been established. The objective of this scoping review was to present an overview of methodological and experimental studies describing ex vivo simulators that assess unconstrained, muscular driven shoulder biomechanics.

METHODS

All studies with ex vivo or mechanical simulation experiments using an unconstrained glenohumeral joint simulator and active components mimicking the muscles were included in this scoping review. Static experiments and humeral motion imposed through an external guide, e.g., a robotic device, were excluded.

RESULTS

Nine different glenohumeral simulators were identified in 51 studies after the screening process. We identified four control strategies characterized by: (a) using a primary loader to determine the secondary loaders with constant force ratios; (b) using variable muscle force ratios according to electromyography; (c) calibrating the muscle path profile and control each motor according to this profile; or (d) using muscle optimization.

CONCLUSION

The simulators with the control strategy (b) (n = 1) or (d) (n = 2) appear most promising due to its capability to mimic physiological muscle loads.

Predictors of infraspinatus muscle degeneration in individuals with an isolated supraspinatus tendon tear

OBJECTIVE

Determine the demographic and clinical factors that predict infraspinatus muscle degeneration in individuals with an isolated supraspinatus tendon tear.

MATERIALS AND METHODS

A retrospective analysis was performed using the medical records of patients who had a shoulder MRI interpreted by 1 of 3 fellowship-trained musculoskeletal radiologists since the implementation of a standardized MRI 3 T protocol within our healthcare system. Demographic (e.g., age, sex) and clinical data (e.g., tear size, muscle degeneration, co-morbidities) were collected. Patients with an isolated supraspinatus tendon tear (n = 121) were assigned to one of two groups based on whether any infraspinatus muscle degeneration was present. Logistic regression was used to assess the univariate relationships between infraspinatus muscle degeneration and patient and clinical data, while least absolute shrinkage and selector operator (LASSO) logistic regression was used to assess the multivariable relationship.

RESULTS

Of the patients with an isolated supraspinatus tendon tear, 16.5% had evidence of infraspinatus muscle degeneration. The presence of infraspinatus muscle degeneration was independently associated with cardiovascular disease (P = 0.01), supraspinatus muscle degeneration (P < 0.01), and subscapularis muscle degeneration (P = 0.01). When the multivariable relationship is assessed, supraspinatus muscle degeneration emerged as the only variable of significant importance for detecting infraspinatus muscle degeneration (specificity: 87.1%, sensitivity: 80.0%).

CONCLUSION

Infraspinatus muscle degeneration is not uncommon in individuals with an isolated supraspinatus tear and is most associated with concomitant supraspinatus muscle degeneration. These findings highlight the need for clinicians to specifically assess the status of each rotator cuff muscle, even when the tendon itself is intact.

Rotator cuff muscle imbalance associates with shoulder instability direction

BACKGROUND

Although muscle weakness and/or imbalance of the rotator cuff are thought to contribute to the development of shoulder instability, the association between muscular dysfunction and shoulder instability is not completely understood. The purpose of this study was to evaluate rotator cuff and deltoid muscle cross-sectional areas in different types of shoulder instability (anterior, posterior, and multidirectional instability [MDI]) and to determine the associations between muscular imbalance and shoulder instability direction.

METHODS

Preoperative magnetic resonance images of patients with shoulder instability who subsequently underwent arthroscopic glenohumeral labral repair or capsular plication were evaluated. Shoulder instability was classified into 3 categories by direction: (1) anterior, (2) posterior, and (3) MDI. The rotator cuff (supraspinatus, subscapularis, and infraspinatus + teres minor) and deltoid (anterior and posterior portions, and total) muscle areas were measured on T1 sagittal and axial slices, respectively. The ratios of the subscapularis to infraspinatus + teres minor area and the anterior deltoid to posterior deltoid area were calculated to quantify the transverse force couple imbalance.

RESULTS

A total of 189 patients were included, where each group consisted of 63 patients. The infraspinatus + teres minor muscle area was smaller than the subscapularis muscle area in the anterior instability group (P = .007). The subscapularis muscle area was smaller than the infraspinatus + teres minor muscle area in the posterior instability and MDI groups (P ≤ .003). The anterior deltoid muscle area was smaller than the posterior deltoid muscle area in all groups (P ≤ .001). The subscapularis-to-infraspinatus + teres minor area ratio in the anterior instability group (1.18 ± 0.40) was higher than that in the posterior instability and MDI groups (0.79 ± 0.31 and 0.93 ± 0.33, respectively; P < .001). There was no difference in the anterior deltoid-to-posterior deltoid area ratio among the 3 groups.

CONCLUSION

Patients with anterior instability have smaller muscle area of the posterior rotator cuff as compared with the anterior rotator cuff. In contrast, patients with posterior instability and MDI have smaller muscle area of the anterior rotator cuff as compared with the posterior rotator cuff. Thus, the direction of shoulder instability is associated with rotator cuff muscle area.

Humeral head coverage in arthroscopic partial repair of massive rotator cuff tears improves functional outcomes: an analysis of influential factors

BACKGROUND

Although partial rotator cuff repair has shown good outcomes, differences in clinical outcomes remain concerns. This study was performed to determine whether patients with humeral head coverage would show better functional outcomes than patients without humeral head coverage and to identify the factors for humeral head coverage after arthroscopic partial repair of massive tears.

METHODS

We performed a retrospective study of 63 patients with massive rotator cuff tears who underwent arthroscopic partial repair between 2012 and 2018. Two to four margin convergences were first performed; then, the Mason-Allen technique was performed. The patients were divided into 2 groups: those with humeral head coverage (38 cases) and those without humeral head coverage (25 cases). The following factors were evaluated: age; sex; hypertension; diabetes; osteoporosis; preoperative and postoperative pseudoparalysis, visual analog scale (VAS) pain score, Constant score, acromiohumeral distance, and subacromial bony spur; and subscapularis tear and repair. Muscle atrophy and fatty degeneration were evaluated by magnetic resonance imaging preoperatively, and the integrity of the repaired cuff was evaluated by ultrasonography at a minimum of 2 years after surgery.

RESULTS

Compared with preoperative values, significant improvements in VAS pain scores (from 6.27 to 2.32 in patients with humeral head coverage and from 7.00 to 2.81 in those without humeral head coverage) and Constant scores (from 51.35 to 75.95 and from 44.62 to 69.81, respectively) were observed in both groups (P < .001). Statistical analysis revealed that postoperative VAS pain scores (2.32 vs. 2.81) and Constant scores (75.95 vs. 69.81) in patients with humeral head coverage were superior to those in patients without humeral head coverage (P = .044 and P = .003, respectively). The integrity of the repaired cuff was evaluated by ultrasonography, and partial tears were found in 4 of 37 patients with humeral head coverage and 2 of 26 patients without humeral head coverage (P = .816). Univariable logistic regression analysis revealed that age (P < .001), comorbidity (P = .005), symptom duration (P = .023), preoperative shoulder mobility (P < .001), maintained acromiohumeral distance (P = .006), subscapularis tear (P = .026), and less preoperative supraspinatus and infraspinatus muscle atrophy (P = .001 and P = .010, respectively) had significant correlations with humeral head coverage.

CONCLUSIONS

Overall satisfactory results were achieved in most patients regardless of high retear rates, but patients with partial repair covering the humeral head were associated with better outcomes than patients without humeral head coverage. Multivariable regression analysis revealed that age (<70 years, P = .003), capability of shoulder mobility (P = .005), maintenance of the acromiohumeral space (>7 mm, P = .016), and less atrophy of the rotator cuff muscles (P = .021) were favorable factors to achieve humeral head coverage during surgical partial repair of massive rotator cuff tears.

Biomechanical comparison of lower trapezius and latissimus dorsi transfer for irreparable posterosuperior rotator cuff tears using a dynamic shoulder model

BACKGROUND

In the setting of irreparable posterosuperior rotator cuff tears (PSRCTs), lower trapezius transfer (LTT) may be anatomically better positioned for restoring the muscular force couple compared with latissimus dorsi transfer (LDT). The purpose of the study was to evaluate the effect of LTT and LDT on glenohumeral kinematics using a dynamic shoulder model.

METHODS

Ten fresh-frozen cadaveric shoulders (mean age: 56.5 ± 17.2 years) were tested using a dynamic shoulder simulator. The maximum abduction angle (MAA), superior humeral head migration (SHM), and cumulative deltoid forces (CDFs) were compared across 4 conditions: (1) native; (2) irreparable PSRCT; (3) LTT using an Achilles tendon allograft; and (4) LDT. MAA and SHM were measured using 3-dimensional motion tracking. CDF was recorded in real time throughout the dynamic abduction motion by load cells connected to actuators.

RESULTS

Compared to the native state, the PSRCT resulted in a significant decrease (Δ-24.1°; P < .001) in MAA, with a subsequent significant increase after LTT (Δ13.1°; P < .001) and LDT (Δ8.9°; P < .001). LTT achieved a significantly greater MAA than LDT (Δ4.2°; P = .004). Regarding SHM, both LTT (Δ-9.4 mm; P < .001) and LDT (Δ-5.0 mm; P = .008) demonstrated a significant decrease compared with the PSRCT state. LTT also achieved significantly less SHM compared with the LDT (Δ-4.4 mm; P = .011). Further, only the LTT resulted in a significant decrease in CDF compared with the PSRCT state (Δ-21.3 N; P = .048), whereas LTT and LDT showed similar CDF (Δ-11.3 N; P = .346). However, no technique was able to restore the MAA, SHM, and CDF of the native shoulder (P < .001, respectively).

CONCLUSION

LTT and LDT both achieved a significant increase in MAA along with significantly less SHM compared with the PSRCT state. Although LTT required significantly less compensatory deltoid forces compared with the PSRCT state, this was not observed for the LDT. Further, the LTT prevented loss of abduction motion and SHM more sufficiently. In the challenging treatment of irreparable PSRCTs, LTT may restore native glenohumeral kinematics more sufficiently, potentially leading to improved postoperative functional outcomes.

Quantitative MRI indicators and features for partial subscapularis tendon tears on conventional shoulder MRI

Background

Diagnosing partial subscapularis (SSC) tendon tears still faces challenges. A failure rate of massive posterosuperior rotator cuff tear repair will be highly increased when extending more than one-third of SSC tendon. This study aims to investigate the quantitative indicators and features of partial SSC tears on conventional shoulder MRI and improve the preoperative diagnostic accuracy.

Materials and methods

Four hundred and thirty-seven patients underwent MRI and arthroscopy were retrospectively reviewed; 89 patients with partial SSC tears in case group and 50 patients with normal SSC in control group were included. Six MRI features with the explicit definition of some quantitative indicators were evaluated.

Results

Fissure sign showed the highest diagnostic efficiency for the partial SSC tears, with a specificity of 92%, sensitivity of 75.3%, and accuracy of 81.3%. Thinning of SSC, fluid collection under the coraco-glenoid arch (CGA), and combined SSP complete tear also showed high specificity of 86%, 80%, and 80%, respectively, while the sensitivity and accuracy were moderate, with a sensitivity of 38.2%, 50.6%, and 48.3%, respectively, an accuracy of 55.4%, 61.2%, and 59.7%, respectively. The specificity, sensitivity, and accuracy of lesser tuberosity cysts were all moderate with values of 68%, 56.2%, and 60%, respectively. However, fat accumulation under the CGA showed no significant difference between the partial SSC tears group and the control group.

Conclusion

Several specific MRI features with quantitative indicators defined in this study can be used to improve the accuracy of preoperative MRI diagnosis of partial SSC tears.

The Rotator Cable Does Not Stress Shield the Crescent Area During Shoulder Abduction

BACKGROUND

It is accepted by the orthopaedic community that the rotator cable (RCa) acts as a suspension bridge that stress shields the crescent area (CA). The goal of this study was to determine if the RCa does stress shield the CA during shoulder abduction.

METHODS

The principal strain magnitude and direction in the RCa and CA and shoulder abduction force were measured in 20 cadaveric specimens. Ten specimens underwent a release of the anterior cable insertion followed by a posterior release. In the other 10, a release of the posterior cable insertion was followed by an anterior release. Testing was performed for the native, single-release, and full-release conditions. The thicknesses of the RCa and CA were measured.

RESULTS

Neither the principal strain magnitude nor the strain direction in either the RCa or the CA changed with single or full RCa release (p ≥ 0.493). There were no changes in abduction force after single or full RCa release (p ≥ 0.180). The RCa and CA thicknesses did not differ from one another at any location (p ≥ 0.195).

CONCLUSIONS

The RCa does not act as a suspension bridge and does not stress shield the CA. The CA primarily transfers shoulder abduction force to the greater tuberosity.

CLINICAL RELEVANCE

The CA is important in force transmission during shoulder abduction, and efforts should be made to restore its continuity with a repair or reconstruction.

Associations between range of motion, strength, tear size, patient-reported outcomes, and glenohumeral kinematics in individuals with symptomatic isolated supraspinatus tears

BACKGROUND

Clinical failure associated with nonoperative treatment of rotator cuff tears may be due to inadequate characterization of the individual's functional impairments. Clinically, restricted passive range of motion (ROM) (restrictions imply capsular tightness), limitations in muscle strength, and larger rotator cuff tears are hypothesized to be related to altered glenohumeral kinematics. Understanding these relationships, as well as the relationship between glenohumeral kinematics and patient-reported outcomes (PROs) prior to exercise therapy, may help characterize functional impairments in individuals with rotator cuff tears. The objectives of the study were to describe the baseline presentation of individuals with an isolated supraspinatus tear, including passive ROM, rotator cuff muscle strength, tear size, PROs, and glenohumeral kinematics, and to determine associations among these variables.

METHODS

One hundred one individuals with symptomatic isolated supraspinatus tears were recruited for the study and underwent assessments of passive glenohumeral ROM, isometric muscle strength, and ultrasonography to assess anterior-posterior tear size. Glenohumeral kinematics during scapular-plane abduction were measured using biplane radiography. Furthermore, PROs including the American Shoulder and Elbow Surgeons (ASES) score and the Western Ontario Rotator Cuff Index (WORC) score were collected.

RESULTS

Individuals presented with decreased ROM, external rotation weakness compared with the uninvolved side, and pain and disability as measured by the ASES and WORC scores. These findings were not associated with glenohumeral kinematics, with the exception of a weak positive association between glenohumeral contact path lengths and WORC scores (ρ = 0.25, P = .03). Tear size was 11.7 ± 5.7 mm, and maximum anterior translation, superior translation, and contact path length were 3.0% ± 3.8% of glenoid width, 3.5% ± 3.8% of glenoid height, and 38.2% ± 20.7% of glenoid size, respectively.

CONCLUSION

Individuals with a symptomatic isolated supraspinatus tear presented with decreased ROM, external rotation weakness, and pain and disability as measured by the ASES and WORC scores. However, no abnormal kinematics associated with these limitations were observed. Thus, given that the tear is isolated to the supraspinatus tendon and no capsular restrictions are present, normal function of the glenohumeral joint may be possible during scapular-plane abduction.

Do partial glenohumeral degenerative changes in patients undergoing arthroscopic rotator cuff repair influence clinical outcomes?

BACKGROUND

The prognostic factors for patients with full-thickness rotator cuff tears (RCTs) include tear size, muscle atrophy and fatty infiltration. However, the influence of early coexisting degenerative changes on RCT outcomes is unappreciated. The purpose of this study was to calculate the impact that pre-existing partial glenohumeral cartilaginous changes have on patients undergoing arthroscopic RCT repair.

METHODS

A study of 54 patients undergoing arthroscopic RCT repair was undertaken. The presence of co-existing patches of glenohumeral degenerative cartilaginous changes and RCT size was recorded at surgery. Pre- and postoperative outcomes were assessed using traditional (Oxford Shoulder Score [OSS], 5-level EuroQol-5D [EQ-5D-5L] questionnaire and EuroQol visual analog scale [EQ-VAS]) and patient-centric re-formatted prisms. Outcomes were assessed as an entire dataset, and sub-group analysis was performed according to the grade of co-existing arthritis and tear size.

RESULTS

Significant improvements (p<0.05) in clinical outcomes were recognized when assessed using either the traditional or reformatted prisms (average % improvements in OSS, EQ-5D-5L and EQ-VAS were 47%, 33% and 43%, respectively; average improvements in pain, function, and psychological well-being were 48%, 33% and, 29%, respectively). Positive gain was noted in all sub-groups of arthritic grading and tear size.

CONCLUSIONS

Good clinical outcomes can be achieved following RCT repair even in the presence of local partial degenerative cartilage changes and advancing tear size. These benefits are patient-centered but require RCT repairability.

Biomechanical analysis of latissimus dorsi, pectoralis major, and pectoralis minor transfers in subscapularis-deficient shoulders

BACKGROUND

Irreparable subscapularis (SSc) tears alter the dynamic force coupling of the shoulder, resulting in pain, weakness, and impaired shoulder function. Pectoralis major (Pma), pectoralis minor (Pmi), and latissimus dorsi (LD) transfers are treatment options for irreparable SSc tears, but clinical outcomes vary. The purpose of this study was to compare the biomechanical properties of Pma, Pmi, and LD transfers in an SSc-deficient shoulder using a computational model.

METHODS

A computer shoulder model was used to investigate the moment arms of Pma, Pmi, and LD tendon transfers compared with an intact SSc. Nine computed tomography scans from subjects without osteoarthritis were used. Virtual Pma, Pmi, and LD transfers were performed to the upper border of the SSc insertion site on the lesser tuberosity of the humerus. Muscle moment arms were computed for functional motions of 0°-80° of internal rotation with the arm in 20° and 90° of shoulder abduction and 0°-150° of shoulder abduction. The results were compared with those of the native SSc moment arms. A repeated-measures analysis of variance was then performed to determine significant differences.

RESULTS

Internal rotation moment arms of the transferred Pma and Pmi decreased significantly after 30° and 40° of internal rotation compared with the SSc moment arm of the intact shoulder, whereas the moment arm of LD transfer more closely mimicked that of the native SSc through 0°-80° of internal rotation. All 3 tendon transfer configurations demonstrated weak abductive moment arms (7.6-8.0 mm), comparable to the intact SSc (7.8 mm) but significantly lower than the intact adductive moment arms of the native Pma and LD (26.8 mm and 28.2 mm, respectively).

CONCLUSION

LD transfer most closely approximates the native SS regarding internal rotation moment arms. However, LD transfer also showed a reduction in adductive moment arms.

Functional and Structural Outcomes After Retears of Arthroscopically Repaired Large and Massive Rotator Cuff Tears

Background:

Most studies have shown acceptable clinical results in patients with large or massive tears treated by arthroscopic rotator cuff repair (ARCR); however, the effects of retears after surgery in these patients remain unknown.

Purpose:

To evaluate functional and structural outcomes after retears of large and massive rotator cuff tears treated by ARCR.

Study Design:

Case series; Level of evidence, 4.

Methods:

A total of 196 consecutive patients with large to massive rotator cuff tears underwent physical examination and magnetic resonance imaging before and after ARCR at 6, 12, and 24 months. Of these, 9 patients were lost at 6 months after surgery. Therefore, 187 patients were followed up for 24 months after surgery; 148 patients showed no postsurgical ruptures. Consequently, the remaining 39 patients with postsurgical ruptures were included in this study (mean age at surgery, 64.2 ± 8.7 years). Functional outcome measures comprised the University of California, Los Angeles (UCLA) and Japanese Orthopaedic Association (JOA) scores. Structural outcome measures consisted of the global fatty degeneration index (GFDI), mediolateral tear size, and residual tendon attachment area as evaluated by our own scoring system.

Results:

The mean UCLA and JOA scores significantly improved from 16.3 ± 3.9 and 63.2 ± 10.7 preoperatively to 27.9 ± 5.5 (P < .0001) and 84.5 ± 9.4 (P < .0001) at final follow-up, respectively. The mean mediolateral tear size (P = .03, .02, and .02, respectively) and residual tendon attachment area (P = .04, .03, and .04, respectively) significantly improved from preoperatively to 6, 12, and 24 months postoperatively. The correlation analysis between the functional and structural variables confirmed significant associations between the residual tendon attachment area, the JOA and UCLA scores at 24 months postoperatively, and the preoperative GFDI (r = –0.81 to 0.78).

Conclusion:

The residual tendon attachment area after a retear was significantly larger at 24 months after surgery than before surgery. In addition, significant associations were confirmed between preoperative fatty degeneration, the residual tendon attachment area, and functional outcomes after a retear. These results may explain why functional outcomes significantly improved even after retears in this series.

Superior capsule reconstruction using a single 6-mm-thick acellular dermal allograft for massive rotator cuff tears: a biomechanical cadaveric comparison to fascia lata allograft

BACKGROUND

Success of superior capsule reconstruction (SCR) using both fascia lata (FL) and human acellular dermal (ACD) allografts have been reported. One possible explanation for a discrepancy in outcomes may be attributed to graft thickness. SCR with commercially available 3-mm-thick ACD allograft is not biomechanically equivalent to FL. Our hypothesis was that SCR with a single 6-mm-thick ACD allograft will restore the subacromial space distance (SubDist) and peak subacromial contact pressures (PSCPs) to intact shoulder and will be comparable to SCR with an 8-mm FL allograft.

METHODS

Eight cadaveric shoulders were tested in 4 conditions: intact, irreparable supraspinatus tear (SST), SCR FL allograft (8-mm-thick), and SCR single ACD allograft (6-mm-thick). SubDist and PSCP were measured at 0°, 30°, and 60° of glenohumeral abduction in the scapular plane. Parameters were compared using a repeated measures analysis of variance with Tukey post hoc test, and graft dimensions were compared using a Student t test.

RESULTS

SST had decreased SubDist (P < .05) and increased PSCP (P < .05) compared with the intact state. At all angles, the SCR ACD allograft demonstrated increased SubDist compared with the tear condition (P < .001), with no difference between grafts. Furthermore, there was decreased PSCP after both ACD and FL SCR compared with the intact condition, with no difference between grafts at 0° (P = .006, P = .028) and 60° abduction (P = .026, P = .013). Both ACD and FL grafts elongated during testing.

CONCLUSIONS

Our results suggest SCR with a single 6-mm-thick ACD allograft is noninferior to FL regarding SubDist and PSCP while completely restoring the superior stability of the glenohumeral joint compared with the intact state.

The biomechanics of the rotator cuff in health and disease - A narrative review

The rotator cuff has an important role in the stability and function of the glenohumeral joint. It is a complex anatomic structure commonly affected by injury such as tendinopathy and cuff tears. The rotator cuff helps to provide a stabilising effect to the shoulder joint by compressing the humeral head against the glenoid cavity via the concavity compression mechanism. To appreciate the function of the cuff it is imperative to understand the normal biomechanics of the cuff as well as the mechanisms involved in the pathogenesis of cuff disease. The shoulder joint offers a wide range of motion due to the variety of rotational moments the cuff muscles are able to provide. In order for the joint to remain stable, the cuff creates a force couple around the glenohumeral joint with coordinated activation of adjacent muscles, which work together to contain the otherwise intrinsically unstable glenohumeral joint and prevent proximal migration of the humerus. Once this muscular balance is lost, increased translations or subluxation of the humeral head may result, leading to changes in the magnitude and direction of the joint reaction forces at the glenohumeral joint. These mechanical changes may then result in a number of clinical presentations of shoulder dysfunction, disease and pain. This narrative review aims to highlight the importance of functional rotator cuff biomechanics whilst assessing the kinetics and kinematics of the shoulder joint, as well as exploring the various factors involved in cuff disease.

Three-dimensional kinematic features in large and massive rotator cuff tears with pseudoparesis

BACKGROUND

Although massive rotator cuff tears occasionally lead to severe impairment of shoulder function, the criteria for losing the ability to elevate the arm are unclear. This study aimed to analyze the features of both tear size and 3-dimensional (3D) shoulder kinematics that correspond to the loss of the ability to elevate the arm in patients with large and massive rotator cuff tears.

METHODS

We prospectively enrolled patients with rotator cuff tears, including the supraspinatus and more than half of the subscapularis or more than two-thirds of the infraspinatus, without severe pain. A total of 13 patients (15 shoulders) were divided into 2 groups: 9 shoulders in the pseudoparesis (P) group and 6 shoulders in the non-pseudoparesis (NP) group. Fluoroscopic images were collected during active scapular-plane elevation, and 3D shoulder kinematics was analyzed using 2-dimensional-3D registration techniques. The radiographic findings and 3D kinematic results were compared between the groups. The correlation between tear size and 3D kinematics was also investigated.

RESULTS

The most superior position of the humeral head center was significantly higher in the P group (6.7 ± 3.0 mm in P group vs. 3.6 ± 1.3 mm in NP group, P = .0321). Superior migration, which was defined as the most superior position > 5 mm, was significantly more frequent in the P group (7 shoulders and 1 shoulder in the P and NP groups, respectively; P = .0201). Thoracohumeral external rotation was significantly smaller in the P group (16° ± 31° in P group vs. 91° ± 21° in NP group, P < .0001). The total tear size and the tear sizes of the anterior and posterior rotator cuffs were significantly correlated with the superior (r = 0.68, P = .0056), anterior (r = 0.68, P = .0058), and posterior (r = -0.80, P = .0004) positions of the humeral head center. The tear size of the posterior rotator cuff also tended to be correlated with glenohumeral external rotation (r = -0.48, P = .0719).

CONCLUSION

Anterior and posterior rotator cuff tears cause significant superior and anteroposterior translations of the humeral head, and posterior cuff tears may lead to loss of glenohumeral external rotation. With these abnormal kinematics, superior migration and loss of thoracohumeral external rotation were identified as features of pseudoparesis.

Bursal Acromial Reconstruction (BAR) Using an Acellular Dermal Allograft as a Surgical Solution for the Treatment of Massive Irreparable Rotator Cuff Tears

Massive, irreparable rotator cuff tears in patients without severe signs of osteoarthritis remains a major challenge for orthopaedic surgeons. These can be a source of significant pain and functional loss occurring most commonly in a relatively frail, elderly patient population. A plethora of surgical techniques covering minimally invasive, arthroscopic techniques and open, salvage procedures have been described for this challenging patient cohort. Continuous evolvement of arthroscopic techniques has led to all-arthroscopic superior capsular reconstruction techniques using allografts, thereby reducing donor side morbidity along with decreased soft tissue dissection. However, conventional superior capsular reconstruction is noted to be a technically complex, time-consuming, and high-cost surgery, which may put this technique beyond the confidence of many shoulder surgeons. The subacromial balloon spacer has emerged as a potential solution in these patients, providing interposition between the humeral head and acromion. However, the subacromial balloon biodegrades rapidly and its effect is only temporary. Thus this technique article presents using an acellular human dermal allograft to reconstruct the bursal layer, which is normally interposed between the humeral head and the acromion. The proposed technique provides a permanent interposition graft preventing humeral acromial contact, which does not undergo rapid biodegradation. The surgical technique is technically feasible, both minimizing surgical time and therefore operative risk to the patient.

The modern use of the extended humeral head (cuff tear arthropathy) hemiarthroplasty

Today, the treatment of osteoarthritis in the rotator cuff–deficient population is largely dominated by reverse shoulder arthroplasty (RSA). Despite the popularity of and increased familiarity with this procedure, the complication rate of RSA remains significant. An extended humeral head hemiarthroplasty may provide a less invasive alternative for select patients with cuff tear arthropathy (CTA) and preserved glenohumeral active elevation. With the indications for reverse arthroplasty expanding to younger patients, there are concerns about the longevity of this implant, as well as the associated revision burden. In the setting of failed RSA, the bone stock available for glenosphere baseplate fixation can be inadequate for reimplantation. The treatment strategies for complex shoulder deformities and failed RSA are limited by patient-specific issues, such as anatomy and risk factors. In this review, we discuss the potential role of extended humeral head hemiarthroplasty (CTA hemiarthroplasty) as a primary surgical option in select patients (1) who have preserved elevation > 90°, (2) who have maintained stability (intact coracoacromial ligament), and (3) who desire to circumvent the complications associated with RSA. Furthermore, CTA hemiarthroplasty may be used for severe glenoid erosion, for a fragmented acromion, and in the revision setting for failed RSA aimed at a reliable salvage procedure.

Graft Tensioning in Superior Capsular Reconstruction Improves Glenohumeral Joint Kinematics in Massive Irreparable Rotator Cuff Tears: A Biomechanical Study of the Influence of Superior Capsular Reconstruction on Dynamic Shoulder Abduction

Background:

Superior capsular reconstruction (SCR) for massive, irreparable rotator cuff tears has become more widely used recently; however, ideal tensioning of the graft and the influence on joint kinematics remain unknown.

Purpose/Hypothesis:

The purpose of this study was to assess the effects of graft tensioning on glenohumeral joint kinematics after SCR using a dermal allograft. The hypothesis was that a graft fixed under tension would result in increased glenohumeral abduction motion and decreased cumulative deltoid forces compared with a nontensioned graft.

Study Design:

Controlled laboratory study.

Methods:

A total of 10 fresh-frozen cadaveric shoulders were tested using a dynamic shoulder simulator. Each shoulder underwent the following 4 conditions: (1) native, (2) simulated irreparable supraspinatus (SSP) tear, (3) SCR using a nontensioned acellular dermal allograft, and (4) SCR using a graft tensioned with 30 to 35 N. Mean values for maximum glenohumeral abduction and cumulative deltoid forces were recorded. The critical shoulder angle (CSA) was also assessed.

Results:

Native shoulders required a mean (±SE) deltoid force of 193.2 ± 45.1 N to achieve maximum glenohumeral abduction (79.8° ± 5.8°). Compared with native shoulders, abduction decreased after SSP tears by 32% (54.3° ± 13.7°; P = .04), whereas cumulative deltoid forces increased by 23% (252.1 ± 68.3 N; P = .04). The nontensioned SCR showed no significant difference in shoulder abduction (54.1° ± 16.1°) and required deltoid forces (277.8 ± 39.8 N) when compared with the SSP tear state. In contrast, a tensioned graft led to significantly improved shoulder abduction compared with the SSP tear state (P = .04) although abduction and deltoid forces could not be restored to the native state (P = .01). A positive correlation between CSA and maximum abduction was found for the tensioned-graft SCR state (r = 0.685; P = .02).

Conclusion:

SCR using a graft fixed under tension demonstrated a significant increase in maximum shoulder abduction compared with a nontensioned graft; however, abduction remained significantly less than the intact state. The nontensioned SCR showed no significant improvement in glenohumeral kinematics compared with the SSP tear state.

Clinical Relevance:

Because significant improvement in shoulder function after SCR may be expected only when the graft is adequately tensioned, accurate graft measurement and adequate tension of at least 30 N should be considered during the surgical procedure. SCR with a tensioned graft may help maintain sufficient acromiohumeral distance, improve clinical outcomes, and reduce postoperative complications.

Instantaneous helical axis estimation of glenohumeral kinematics: The impact of rotator cuff pathology

The rotator cuff is theorized to contribute to force couples required to produce glenohumeral kinematics. Impairment in these force couples would theoretically result in impaired ball-and-socket kinematics. Although less frequently used than traditional kinematic descriptors (e.g., Euler angles, joint translations), helical axes are capable of identifying alterations in ball-and-socket kinematics by quantifying the variability (i.e., dispersion) in axis orientation and position during motion. Consequently, assessing glenohumeral helical dispersion may provide indirect evidence of rotator cuff function. The purpose of this exploratory study was to determine the extent to which rotator cuff pathology is associated with alterations in ball-and-socket kinematics. Fifty-one participants were classified into one of five groups based on an assessment of the supraspinatus using diagnostic imaging: asymptomatic healthy, asymptomatic tendinosis, asymptomatic partial-thickness tear, asymptomatic full-thickness tear, symptomatic full-thickness tear. Glenohumeral kinematics were quantified during coronal plane abduction using a biplane x-ray system and described using instantaneous helical axes. The degree to which glenohumeral motion coincided with ball-and-socket kinematics was described using the angular and positional dispersion about the optimal helical axis and pivot, respectively. No statistically significant difference was observed between groups in angular dispersion. However, symptomatic individuals with a full-thickness supraspinatus tear had significantly more positional dispersion than asymptomatic individuals with a healthy supraspinatus or tendinosis. These findings suggest that symptomatic individuals with a full-thickness supraspinatus tear exhibit impaired ball-and-socket kinematics, which is believed to be associated with a disruption of the glenohumeral force couples.

Shoulder proprioception following reverse total shoulder arthroplasty

Joint replacement affects the proprioception, as shown in knees, elbows, and shoulder studies.

AIM

The aim was to evaluate shoulder joint position sense (JPS) following reverse total shoulder arthroplasty (rTSA) for patients with cuff arthropathy.

METHODS

Twenty-nine patients that underwent unilateral rTSA (19 females, 10 males) and 31 healthy volunteers evaluated for JPS of shoulder using a dedicated high accuracy electronic goniometer. Error of active reproduction of joint position (EARJP) was assessed at the following reference positions: 30°, 60°, 90°, and 120° for forward flexion and abduction and 15°, 30°, and 45° for internal and external rotation in rTSA, contralateral non-operated, and control shoulders.

RESULTS

Results of EPRJP for rTSA, contralateral, and control (respectively) are as follows:Forward flexion: 30° = (8.0 ± 5.7, 9.8 ± 6.1, and 4.9 ± 3.0), 60° = (5.0 ± 2.8, 5.9 ± 2.7, and 5.1 ± 3.2), 90° = (3.1 ± 1.6, 5.5 ± 2.6, and 3.2 ± 1.4), and 120° = (3.4 ± 2.1, 5.6 ± 4.0, and 3.5 ± 1.7)Abduction: 30° = (5.2 ± 2.5, 9.1 ± 6.1, and 4.6 ± 2.3), 60° = (5.2 ± 3.6, 6.6 ± 4.1, and 5.3 ± 3.1), 90° = (3.8 ± 2.0; 7.4 ± 5.5, and 4.1 ± 1.9), and 120° = (5.3 ± 2.9, 7.7 ± 5.3, and 4.2 ± 1.9)Internal rotation: 15° = (4.3 ± 3.1, 6.2 ± 4.4, and 2.8 ± 1.2), 30° = (3.2 ± 1.9, 4.5 ± 2.3, and 3.3 ± 1.4), and 45° = (3.5 ± 2.0, 4.1 ± 1.8, and 2.8 ± 1.0)External rotation: 15° = (3.0 ± 1.7, 4.2 ± 2.2, and 3.6 ± 1.4) and 30° = (3.1 ± 1.5, 3.8 ± 2.6, and 3.4 ± 1.6)The results showed significantly better JPS (lower EPRJP) in shoulders following rTSA and normal control shoulders comparing with the patient's contralateral shoulder. The explanation can be that rTSA improves joint kinematics and stability, which allows better muscular performance and proprioception feedback.

CONCLUSION

Shoulders following rTSA show JPS superior to non-operated contralateral shoulders and comparable with healthy population shoulders. It seems that rTSA restores shoulder proprioception.

Evaluation of the Electromyographic Amplitude-to-Work Ratio in the Infraspinatus Muscle During External Shoulder Rotation Exercises: A Comparison of Concentric Isotonic and Isokinetic Exercises

Background:

Isotonic exercise is commonly adopted for shoulder rehabilitation, but the efficacy of isokinetic exercise for rehabilitation has not been evaluated.

Purpose:

To evaluate the efficacy of isotonic and isokinetic external shoulder rotation exercises.

Study Design:

Controlled laboratory study.

Methods:

Using surface electromyography (EMG) and the Biodex system, we investigated the EMG amplitude of the infraspinatus (IS), total work (tWK), and EMG(IS)/tWK ratio and examined the relative IS and posterior deltoid (PD) contributions to all exercises. A total of 24 healthy participants without musculoskeletal injuries were included. Participants performed isotonic external shoulder rotation at 10%, 20%, 30%, 40%, and 50% of the maximum voluntary isometric contraction (MVIC) as well as isokinetic external shoulder rotation at angular velocities of 60, 120, 180, 240, and 300 deg/s. Levels of intensity were classified from 1 to 5: level 1 corresponded to 10% of the MVIC and a 300-deg/s angular velocity; level 2 corresponded to 20% MVIC and 240 deg/s; level 3 corresponded to 30% MVIC and 180 deg/s; level 4 corresponded to 40% MVIC and 120 deg/s; and level 5 corresponded to 50% MVIC and 60 deg/s. Normalized IS and tWK amplitudes were calculated for each exercise.

Results:

During isotonic exercise, the EMG(IS)/tWK ratio significantly decreased from level 5 to 3, 2, and 1; from level 4 to 2 and 1; and from level 3 to 1. During isokinetic exercise, the EMG(IS)/tWK ratio at level 3 was greater than that at all other levels except level 1. Statistical differences were found between isotonic and isokinetic modes at levels 1, 2, and 3. The IS/PD activation ratios were not significantly different between exercise modes at any level.

Conclusion:

Isokinetic resistance may provide more effective stimulation of the IS muscle compared with isotonic resistance.

Clinical Relevance:

Isokinetic exercise needs to be considered as a method of rehabilitation that effectively increases infraspinatus muscle activity.

Retrospective review of open and arthroscopic repair of anterosuperior rotator cuff tears with subscapularis involvement: a single surgeon's experience

BACKGROUND

There have been conflicting results when comparing outcomes of open vs. arthroscopic anterosuperior rotator cuff repairs with subscapularis involvement. The purpose of this study was to evaluate midterm outcome differences and complications following open vs. arthroscopic repair of rotator cuff tears involving the subscapularis by a single surgeon.

METHODS

This was a retrospective review of 57 rotator cuff repairs involving the subscapularis performed by a single surgeon over a 10-year period. During this time, the surgeon transitioned from open to arthroscopic repair. Preoperative and postoperative range of motion, lift-off test, belly press test, and American Shoulder and Elbow Surgeons (ASES) Standardized Shoulder Assessment form scores were measured.

RESULTS

Eighteen patients had open procedures and 39 had arthroscopic repair. The mean preoperative ASES score for the open group was 39 and postoperatively was 79. The mean preoperative ASES score for the arthroscopic group was 44 and improved to 80 postoperatively. There was no significant difference in score or change in score between the 2 groups (P > .05). There was only 1 complication. It occurred in the open group and was a superficial wound dehiscence.

CONCLUSIONS

This study demonstrated no outcome differences between open and arthroscopic rotator cuff repair involving the subscapularis, even with large subscapularis tears. Both techniques significantly improved shoulder function. Arthroscopic and open rotator cuff repairs including the subscapularis are relatively safe procedures, and either technique is an acceptable option.

Three-dimensional in vivo comparative analysis of the kinematics of normal shoulders and shoulders with massive rotator cuff tears with successful conservative treatment

BACKGROUND

This study used in vivo three-dimensional to two-dimensional image registration techniques to compare the glenohumeral kinematics of shoulders with massive rotator cuff tears that were successfully treated conservatively and those of normal shoulders.

METHODS

Ten patients (age, 67.4 ± 3.63 years) with massive rotator cuff tears on one side and without contralateral tears were enrolled. We performed computed tomography and fluoroscopy on both shoulder joints and created three-dimensional bone models of the humerus and scapula using image registration techniques. We measured the humeral superoinferior translation, angle of humeral external rotation, scapular upward rotation, scapular anteroposterior tilt, and scapular external rotation of the torn shoulders with good range of motion after effective conservative treatment and compared these measurements to those of the contralateral normal shoulders.

FINDINGS

There was a significant difference in the initial position of the humeral head relative to the glenoid in the tear group; it was 2.0 mm higher than that in the normal group (p < .05). This difference disappeared in the range from 40° to full elevation. The scapular motion of the tear group was significantly more upwardly rotated than that of the normal group: by 9.9° at rest (p < .05) and by 11.6° at terminal elevation (p < .05). No significant differences were detected for humeral head external rotation, scapular anteroposterior tilt, and scapular external rotation between the two groups.

INTERPRETATION

Kinematics of shoulders with massive cuff tears could not be recovered completely even though the patients had no significant symptoms after successful conservative treatment.

Prevalence and risk factors for development of subscapularis and biceps pathology in shoulders with degenerative rotator cuff disease: a prospective cohort evaluation

BACKGROUND

The prevalence of subscapularis and long head of biceps (LHB) in relation to the presence and severity of posterosuperior (PS) rotator cuff disease is not known.

METHODS

Subjects with asymptomatic rotator cuff tears were enrolled for this prospective longitudinal study (n = 354) and followed annually with shoulder ultrasonography and clinical evaluations to assess for the presence of subscapularis, LHB, and PS rotator cuff pathology and pain development.

RESULTS

Subscapularis pathology developed in 14% of shoulders over a median follow-up of 5 years, with partial-thickness tearing occurring most commonly (83%). Age, sex, and hand dominance were not associated with subscapularis pathology. A greater proportion of concomitant full-thickness PS cuff tears were observed in shoulders that developed subscapularis tears (76% vs. 50%, P = .002). The PS cuff tear width (10 mm vs. 14 mm, P = .01) at the time of enrollment and both tear width (10 mm vs. 15 mm, P = .003) and length (12 mm vs. 15.5 mm, P = .02) at the time of diagnosis of subscapularis pathology were greater in subscapularis-torn shoulders. LHB pathology was prevalent in 34% of shoulders, with dislocation/subluxation occurring in 63% and higher prevalence in subscapularis-torn shoulders (71% vs. 12%, P < .01). Subscapularis-torn shoulders were more likely to develop pain (67% vs. 45%, P = .004), and concomitant PS cuff tear enlargement was associated with greater risk for pain development (76% vs. 36%, P = .01).

CONCLUSIONS

The development of subscapularis and LHB pathology is significantly related to the size of the PS cuff tear. Subscapularis involvement is associated with greater risk of pain development in degenerative rotator cuff disease.

Superior Capsule Reconstruction With Subacromial Allograft Spacer: Biomechanical Cadaveric Study of Subacromial Contact Pressure and Superior Humeral Head Translation

PURPOSE

To investigate the biomechanical effects of superior capsule reconstruction with subacromial allograft spacer on superior humeral head translation and subacromial contact pressure.

METHODS

Eight cadaveric shoulder specimens were tested in 4 conditions: (1) intact rotator cuff, (2) supraspinatus tear and superior capsule excision, (3) superior capsule reconstruction with human dermal allograft, and (4) superior capsule reconstruction with subacromial resurfacing using human dermal allograft. In each condition, specimens were tested at 0, 30, 60, and 90° of shoulder abduction in balanced and unbalanced loaded states for subacromial contact pressure and superior humeral head translation. Statistical comparisons were made using a repeated-measures analysis of variance test, followed by a Tukey post hoc test for pairwise comparisons. A P value <.05 was set as statistically significant.

RESULTS

Superior humeral head translation and subacromial contact pressure were increased after irreparable rotator cuff tear (P = .001). There was no significant difference between superior capsule reconstruction and intact cuff in regard to superior humeral head translation and subacromial contact pressure at all abduction angles. Superior capsule reconstruction with subacromial resurfacing decreased superior humeral head translation relative to intact (0°, P = .004; 30°, P = .02; 60°, P = .08; 90°, P = .01), superior capsule reconstruction (0°, P = .001; 30°, P = .003; 60°, P = .019; 90°, P = .001), and cuff-deficient states (P = .001). Superior capsule reconstruction with subacromial resurfacing resulted in nonsignificant increases in subacromial contact pressure relative to intact cuff at 0 to 90° abduction angles.

CONCLUSIONS

Superior capsule reconstruction with subacromial resurfacing using human dermal allograft results in decreased superior humeral head translation relative to superior capsule reconstruction with human dermal allograft only, while increasing subacromial contact pressure.

CLINICAL RELEVANCE

Superior capsule reconstruction with subacromial resurfacing using human dermal allograft reduces superior humeral head translation while increasing subacromial contact pressure in a cadaveric model.

Biomechanical Effect of Superior Capsule Reconstruction Using a 3-mm and 6-mm Thick Acellular Dermal Allograft in a Dynamic Shoulder Model

PURPOSE

To biomechanically compare the effect of superior capsule reconstruction (SCR) using a 3- and 6-mm thick acellular dermal allograft for the treatment of irreparable rotator cuff tears.

METHODS

Eight fresh-frozen cadaveric shoulders were tested using a dynamic shoulder model. Maximum abduction angle (MAA), glenohumeral superior translation (ghST), subacromial peak contact pressure (sPCP), and cumulative deltoid force (cDF) were compared among 4 conditions: (1) intact shoulder, (2) simulated irreparable rotator cuff tear (RCT), (3) SCR using a 3-mm-thick acellular dermal allograft, (4) SCR using a 6-mm-thick acellular dermal allograft.

RESULTS

Compared with the intact state, simulated irreparable RCTs significantly decreased MAA (P < .001), while significantly increasing ghST (P = .001), sPCP (P < .001), and cDF (P < .001). SCR with a 3-mm-thick graft significantly increased MAA (P = .01) and decreased ghST (P = .01) compared with the RCT state, however, showed similar sPCP and cDF. Compared with the torn state, SCR with a 6-mm-thick graft significantly increased MAA (P < .001) and significantly decreased ghST (P < .001), sPCP (P < .001), and cDF (P = .001). Using a 6-mm-thick graft demonstrated similar MAA, ghST, sPCP, and cDF compared with the intact state. When comparing the 3-mm to the 6-mm thick graft, significant differences were found in ghST (P = .03), sPCP (P < .001), and cDF (P = .02).

CONCLUSIONS

SCR with a 6-mm-thick acellular dermal allograft better restored normal glenohumeral joint position and forces compared with a 3-mm-thick graft for the treatment of irreparable RCTs.

CLINICAL RELEVANCE

Graft thickness may affect the clinical success following SCR with commercially available dermal allografts. Using a thicker (>3 mm) graft was able to biomechanically better restore native glenohumeral joint properties.

Diagnostic Value of Acromiohumeral Distance in Rotator Cuff Pathology: Implications for Advanced-Practice Physiotherapists

Purpose: The primary purpose of this study was to examine the inter-tester reliability and criterion validity of reduced acromiohumeral distance (AHD; <6 mm) visualized on plain radiographs in detecting rotator cuff (RC) pathology. The secondary objective was to examine the relationship between this radiographic feature and patient demographics and clinical examination. Method: This was a diagnostic study of patients seen in a tertiary care centre. Two advanced-practice physiotherapists measured AHD in two radiographic views. MRI was used as the gold standard. Results: A total of 150 consecutive patients (mean age 59 [SD 11] y, 57 women, 93 men) were included. AHD less than 6 millimetres was highly specific in both views for the presence of tear (99%), tear size (96%-98%), and fatty infiltration in the supraspinatus and infraspinatus muscles (93%-96%). The absence of AHD less than 6 millimetres was associated with a lack of advanced fatty infiltration in the supraspinatus and infraspinatus muscles (92%-100%). Sensitivity values were low for the presence and size of RC tear (21%-55%). We found a statistically significant positive association between the AHD categories and clinically observed muscle wasting and weakness of the RC muscles (p < 0.05). Conclusions: AHD less than 6 millimetres was reliably measured in plain radiographs and was strongly associated with important clinical and imaging features of advanced RC pathology; this may assist with clinical decision making by allowing judicious use of more costly investigations and referral for surgery.

Does strength deficit correlate with shoulder function in patients with rotator cuff tears? Characteristics of massive tears

BACKGROUND

The correlation between shoulder strength deficits and function in rotator cuff tears remains uncertain. This study aimed to determine the correlation between shoulder strength deficits and shoulder function evaluated by various clinical scoring systems.

METHODS

A total of 262 patients (mean age, 59.67 years [standard deviation, 8.06 years]) who underwent full-thickness rotator cuff repair were included. Patients in group I (n = 188) had small to large rotator cuff tears, whereas those in group II (n = 74) had massive rotator cuff tears. Demographic factors, isokinetic test results, and shoulder function evaluated using various scoring systems were obtained. Correlation differences according to severity of the rotator cuff tear were evaluated.

RESULTS

We found weak correlations between shoulder strength deficits (peak torque and total work) and clinical outcomes in patients with rotator cuff tears (r = -0.288). For patients in group I (nonmassive tears), we found a weaker correlation (r = -0.242) according to the tear pattern. However, shoulder strength deficits in group II patients (massive tears) were strongly correlated with American Shoulder and Elbow Surgeons (r = -0.598), Constant (r = -0.582), and Short Form 36 (r = -0.511) scores, especially regarding internal rotator strength deficits.

CONCLUSIONS

Shoulder strength deficits measured via isokinetic testing and shoulder function were weakly correlated in patients with rotator cuff tears. However, shoulder strength deficits in patients with massive tears considerably worsened shoulder function and systemic disability, but not regional disability. In particular, internal rotator strength deficits were strongly correlated with poor shoulder function.

[Osteoarthritis of the shoulder: pathogenesis, diagnostics and conservative treatment options]

PATHOGENESIS

Osteoarthritis of the shoulder is characterized by a progressive degenerative process, which is based on chronic inflammation with intra-articular release of different cytokines and proteolytic enzymes. The main predisposing factors are a history of trauma or surgery, as well as chronic overuse or instability of the glenohumeral joint. Affected patients especially suffer from impaired joint function and pain, which are often associated with cognitive and psychosocial restrictions.

DIAGNOSTICS

Possible co-pathologies have to be evaluated carefully both clinically and radiologically as they must be taken into account in the therapeutic procedure. If arthroplasty of the shoulder is planned, a pre-operative CT scan is mandatory in order to evaluate the bone stock of the glenoid, which has a decisive influence on the choice of implant.

TREATMENT

Conservative treatment options are oral pain medication, physical therapy, and intra-articular injections, whereby, in comparison to corticosteroids, hyaluronic acid seems to be advantageous especially with respect to the duration of a positive clinical effect.

Patient-Reported Outcomes After Isolated and Combined Arthroscopic Subscapularis Tendon Repairs

PURPOSE

To analyze minimum 2-year postoperative patient-reported outcomes of a large group of patients after arthroscopic subscapularis (SSc) repair with respect to surgical findings and concurrent procedures.

METHODS

Patients who underwent arthroscopic SSc repair from January 2010 to April 2016 completed the Patient-Reported Outcomes Measurement Information System for Upper Extremity (PROMIS-UE) test and postoperative visual analog scale pain score. Medical records were reviewed for the preoperative visual analog scale pain score and surgical findings. SSc tears were considered partial or complete. Concomitant pathology and treatment of the supraspinatus (SS), infraspinatus (IS), and biceps tendon were recorded. We compared preoperative variables and outcomes between isolated partial SSc repair, partial SSc with SS and/or IS repair, isolated complete SSc repair, and complete SSc with SS and/or IS repair.

RESULTS

One hundred forty-five shoulders were included with an average age of 62.0 ± 9.8 years and average follow-up period of 52.2 ± 19.5 months. A significant reduction in the pain score occurred, from 4.8 (95% confidence interval [CI], 4.4-5.2) to 0.9 (95% CI, 0.6-1.1) (P < .001), with a mean postoperative PROMIS-UE score of 50.7 (95% CI, 49.5-52.0). Most SSc tears were partial with SS and/or IS repair (44.1%). Isolated partial SSc tears (29.9%), complete SSc tears with SS and/or IS repair (20.1%), and isolated complete SSc tears (5.9%) were less common. A significant difference in the mean postoperative PROMIS-UE score was not found between groups (P = .609). Biceps tendon pathology was significantly more common in complete SSc tears than partial SSc tears (P < .001), but there was no difference in the rate of biceps intervention (P = .110) or the PROMIS-UE score based on biceps intervention (P = .471).

CONCLUSIONS

We observed significant improvements in pain and patient-reported outcomes in line with population means for a large group of patients after SSc tendon repair. Importantly, outcomes were similar despite the size of SSc tear or concurrent SS and/or IS repairs. Biceps pathology was common, and neither its presence nor its treatment influenced postoperative patient outcomes.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

The grade of preoperative subscapularis muscle atrophy as a prognostic factor for postoperative retears: A double-center retrospective series

The aim of the study was to investigate whether subscapularis muscle atrophy is a negative prognostic factor leading to increased risk of retears in patients treated with an arthroscopic subscapularis tendon repair. We hypothesized that fatty infiltration of the subscapularis muscle deteriorates the clinical and sonographic outcome of the arthroscopic repair and inhibits reparability of the ruptured tendons. A double- center, multinational, retrospective, blind (in the follow-up) clinical study regarding 32 patients who underwent an arthroscopic subscapularis repair was conducted. Patients were divided into two groups according to the preoparative fatty infiltration grade of subscapularis muscle (group A: grade<II, group B: grade II or higher). Reparability was not influenced by the grade of preoperative fatty infiltration of subscapularis muscle. The preoperative MRI scans showed significantly higher grades of fatty infiltration (group B) in the subscapularis muscle of patients with clinical evidence of retear after the arthroscopic repair. Low grades of preoperative subscapularis muscle atrophy are significantly correlated with low clinical and sonographic retear’s rate after subscapularis arthroscopic repair, while high grades were a clear negative prognostic factor for the clinical outcome of the aforementioned patients.

Factors associated with pain in nonsurgically treated rotator cuff tears -A study with magnetic resonance imaging

BACKGROUND

In rotator cuff tears, some cases become asymptomatic with nonsurgical treatment, others remain symptomatic. The purpose of this study was to identify factors associated with pain in nonsurgically treated rotator cuff tears using magnetic resonance imaging (MRI).

METHODS

In total, 108 shoulders diagnosed with supraspinatus (SSP) tendon tears using MRI were nonsurgically treated, and MRI was repeated after more than a year. The patients were divided into pain or improvement group according to whether the pain persisted or disappeared. Bursal fluid accumulation; SSP tendon retraction; subscapularis (SSC) tendon tears; infraspinatus (ISP) tendon tears; and Goutallier classification into SSC, SSP, and ISP were included as evaluation factors. Predictive factors for persistent pain on initial MRI and factors associated with persisting pain after nonsurgical treatment on repeat MRI were statistically analyzed using multivariate logistic regression analysis.

RESULTS

The improvement group showed a significant decrease in bursal fluid accumulation compared with the pain group (p < 0.01). SSC tendon tears (OR, 4.42; 95% CI, 1.16-16.9; P = 0.03) on initial MRI were significantly associated with persistent pain. Bursal fluid accumulation (OR, 2.44; 95% CI, 1.18-5.07; P = 0.02) and SSC tendon tears (OR, 2.25; 95% CI, 1.15-4.39; P = 0.02) on repeat MRI were significantly associated with persistent pain.

CONCLUSIONS

Bursal fluid accumulation decreased when pain improved. The involvement of SSC tendon tears can serve as a predictive factor for persistent pain. Pain may persist although patients with rotator cuff tears including SSC tendon tears are nonsurgically treated.

LEVEL OF EVIDENCE

Level IV case-control study.

The Volume of Subscapularis Muscle Remains Unaffected by Supraspinatus Tendon Tears: Three-dimensionally Reconstructed Magnetic Resonance Imaging Analysis

Background

This study aimed to compare the subscapularis muscle volume between the intact groups (group I) and supraspinatus tendon tear groups (group T) based on the sex and three different age groups.

Methods

Subjects with a group I and subjects with group T without any other lesions were retrospectively evaluated from among patients who received a magnetic resonance imaging (MRI) scan between January 2011 and December 2013. The MRI scans were studied by a consultant radiologist. The subscapularis muscle volume was compared according to the age and sex; the age groups were categorized as patients in their 40s, 50s, and 60s. The volume of subscapularis muscle was measured by three-dimensional reconstructed images acquired through the axial section of 1.5T MRI.

Results

No statistically significant differences were observed between subscapularis muscle volume of the group I and group T, except for male patients in their 50s (group I: 100,650 mm³ vs. group T: 106,488 mm³) and 60s (group I: 76,347 mm³ vs. group T: 99,549 mm³) (p<0.05). Males had a larger mean volume of subscapularis muscle than females, and the subscapularis muscle volume decreased in a linear manner with increasing age.

Conclusions

Decrease in subscapularis muscle volume was observed with increasing age, and the impact of supraspinatus tear on subscapularis muscle volume is age and sex dependent.