The subscapularis muscle and its glenohumeral ligament-like bands. A histomorphologic study

Arthroscopic subscapularis repair using the subscapularis interlocking (SICK)-stitch technique leads to restoration of clinical function with low complication and revision rates

Background

The purpose of this study is to determine the mid-term outcome after arthroscopic subscapularis tendon (SCP) reconstruction using the subscapularis interlocking (SICK)-stitch technique. The hypotheses are that arthroscopically repaired SCP lesions using the SICK-stitch show a good restoration of shoulder function with low complication and failure rates.

Methods

This is a retrospective monocentric study of n = 199 patients (n = 106 female) with arthroscopically treated SCP tears with the interlocking (SICK) stitch technique from July 2013 to October 2018. Inclusion criteria: minimum follow-up of 2 years. Exclusion criteria: irreparable and massive cuff tears, osteoarthritis, and fractures. The postoperative assessment consisted of the range of motion, constant score, simple shoulder test, simple shoulder value, disability of the shoulder and arm score, short form 12, and patient satisfaction.

Results

Mean age was 61 years (25-83); n = 4 (2%) patients were lost to follow-up with mean follow-up time of 63.6 months (36-96). Additional supraspinatus tendon lesions (n = 147) were repaired in n = 101 cases. SCP grading (n = 69) (35% traumatic) (Fox/Romeo): n = 113 grade II, n = 71 grade III, n = 11 grade IV. A positive preoperative lift-off test (n = 132, 68%) was corrected in n = 124 (94%) of cases. Ninety seven percent of patients would undergo surgery again with a mean satisfaction score of 14.4/15. Results at final follow-up (data: mean pre; post; P value): lexion (130; 166; .001), abduction (123;159; .001), external rotation (35;82; .001), internal rotation (52; 68; .07), constant score (50; 82; .001), disability of the shoulder and arm score (40; 19; .001), simple shoulder test (5; 10; .001), and simple shoulder value (44; 83; .001) significantly improved. The mean physical health scale short form 12 was 46 (24-63) and 51 (15-66) for mental health. Age, body mass index, SCP-grading, and supraspinatus tendon repair did not significantly affect any outcome parameter. Three (1.5%) patients underwent revision surgery, of which 1 (0.5%) had an infection.

Conclusion

Two years after arthroscopic SCP repair using the SICK-stitch technique, we observed excellent restoration of clinical function with low complication and revision rates. The SICK-stitch technique thus represents a good and reliable therapeutic option for the arthroscopic repair of SCP lesions.

The subscapularis muscle: A meta-analysis of its variations, prevalence, and anatomy

BACKGROUND

The subscapularis (SSC) is the largest rotator cuff muscle and is involved in the medial rotation, abduction, adduction, and anterior stabilization of the shoulder. It is anatomically variable, as is the morphology and prevalence of the accessory SSC (aSSC), a rare muscle slip attached to the SSC. There is no current review investigating the prevalence and morphometrics of the SSC and aSSC.

PURPOSE

To investigate the prevalence of the morphological variants of the SSC and aSSC via meta-analysis and review the relevant literature involving cadaveric, magnetic resonance imaging, and ultrasonographic studies.

STUDY DESIGN

Meta-analysis.

MATERIALS AND METHODS

Literature data reporting the prevalence rates and morphometrics of the SSC and aSSC and their variants were pooled. Literature searches and data analyses were performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Anatomical Quality Assurance guidelines.

RESULTS

Forty-six studies, totaling 2166 shoulders, were assessed. The SSC showed an overall length, thickness, cross-sectional area, and volume of 152.2 mm (95% confidence interval, CI, 103.8-200.5 mm), 5.6 mm (95% CI, 4.6-6.6 mm), 18.1 cm² (95% CI, 14.2-22.0 cm² ), and 126.9 cm³ (95% CI, 87.2-166.5 cm³ ), respectively. The SSC displayed substantial variations in its origin and insertion points and in the composition of its tendon. The aSSC had an overall pooled prevalence of 24.6% (95% CI, 0.0%-76.9%).

CONCLUSIONS

The SSC and aSSC have been implicated in multiple shoulder pathologies, including muscle and tendon ruptures and neurovascular compromise. A better understanding of SSC and aSSC variants when diagnosing and treating their related pathologies will reduce patient morbidity and improve treatment regimens.

Clinical outcomes and recurrence rate of 4 procedures for recurrent anterior shoulder instability: ASA, remplissage, open, and arthroscopic Latarjet: a multicenter study

BACKGROUND

The aim of the present study was to compare the clinical outcomes of 4 surgical techniques in patients with recurrent anterior shoulder dislocation, glenoid bone loss (GBL) <15% and Instability Severity Index (ISI) score >3.

METHODS

A retrospective multicenter study was conducted on 226 patients who underwent 1 of 4 different techniques (Bankart plus arthroscopic subscapularis augmentation (ASA), Bankart plus remplissage, Latarjet, Arthro-Latarjet). The inclusion criteria were: recurrent dislocation, GBL <15%, and ISI score >3. The exclusion criteria were: GBL >15%, voluntary instability, multidirectional instability, preexisting osteoarthritis, throwing athletes' first dislocation, and ISI score<3. Follow-up ranged from 24 months to 6 years. Hyperlaxity was clinically evaluated according to Neer and Coudane-Walch tests. Clinical outcomes were assessed using the Rowe score and the Western Ontario Shoulder Instability Index (WOSI) for each technique. Before surgery, all patients underwent magnetic resonance imaging and computed tomography scanning. The Pico area method was used to assess the percentage of GBL. The operations were performed by 10 experienced surgeons; the functional outcomes were evaluated by 2 independent observers.

RESULTS

A total of 226 patients who met the inclusion criteria were included in the present series. A total of 89.2% of patients in the ASA group reported an excellent Rowe score at the final follow-up, and their scores on the WOSI scale, improved from 838 to 235 points. A total of 79.9% of patients in remplissage (R) group reported an excellent Rowe score at the final follow-up, and their scores on the WOSI scale improved from 1146 to 465 points. A total of 98.5% of patients in the Latarjet (L) group reported an excellent Rowe score at the final follow-up, and their scores on the WOSI scale improved from 1456 to 319 points. A total of 81.6% of patients in the Arthro-Latarjet (AL) group reported an excellent Rowe score at the final follow-up, and their scores on the WOSI scale improved from 1250 to 221 points. The recurrence rates were as follows: ASA group (7%), remplissage group (6.1%), L group (1.5%), Arthro-Latarjet group (0%). Patients in the open L group had 15.5% (10/66) more complications.

CONCLUSION

The use of ASA and remplissage to augment the Bankart repair have been demonstrated to be effective for restoring joint stability, yielding good clinical outcomes similar to the L procedure in patients affected by recurrent anterior dislocation with GBL <15% and an ISI score score >3. Soft tissues augmentations of the Bankart repair have been demonstrated to be effective for addressing anterior soft tissue deficiency dysfunction and critical Hill-Sachs lesions.

Subscapularis repair in reverse total shoulder arthroplasty: a systematic review and descriptive synthesis of cadaveric biomechanical strength outcomes

Hypothesis/Background

There is no consensus on whether to repair the subscapularis in the setting of reverse total shoulder arthroplasty (rTSA). There have been an assortment of studies showing mixed results regarding shoulder stability and postoperative strength outcomes when looking at subscapularis repair in rTSA. The purpose of this systematic review was to investigate differences in biomechanical strength outcomes of cadaveric subscapularis repair vs. no repair in rTSA.Increased force will be required to move the shoulder through normal range of motion (ROM) in cadaveric rTSA shoulders with the subscapularis repaired when compared with no subscapularis repair.

Methods

A comprehensive literature review was conducted in accordance with the 2009 Preferred Reporting Items for Systematic Review and Meta-Analysis statement. The databases used to search the keywords used for the concepts of subscapularis, reverse total shoulder arthroplasty, and muscle strength were PubMed (includes MEDLINE), Embase, Web of Science, Cochrane Reviews and Trials, and Scopus. Original, English-language cadaveric studies evaluating rTSA and subscapularis management were included, with subscapularis repair surgical techniques and strength outcomes being evaluated for each article meeting inclusion criteria.

Results

The search yielded 4113 articles that were screened for inclusion criteria by 4 authors. Two articles met inclusion criteria and were subsequently included in the final full-text review. A total of 11 shoulders were represented between these 2 studies. Heterogeneity of the data across the 2 studies did not allow for meta-analysis. Hansen et al found that repair of the subscapularis with rTSA significantly increased the mean joint reaction force and the force required by the posterior deltoid, total deltoid, infraspinatus, teres minor, total posterior rotator cuff, and pectoralis major muscles. Giles et al found that rotator cuff repair and glenosphere lateralization both increased total joint load.

Conclusion

The present review of biomechanical literature shows that repair of the subscapularis in the setting of rTSA can effectively restore shoulder strength by increasing joint reactive forces and ROM force requirements of other rotator cuff muscles and of the deltoid muscle. Available biomechanical evidence is limited, and further biomechanical studies evaluating the strength of various subscapularis repair techniques are needed to evaluate the effects of these techniques on joint reactive forces and muscle forces required for ROM.

Risk factors of radiographic severity of massive rotator cuff tear

As massive rotator cuff tears progress, various radiographic changes occur; however, the factors associated with radiographic changes remain largely unknown. This study aimed to determine the factors that affect radiographic severity in massive rotator cuff tears using multivariate analyses. We retrospectively reviewed 210 shoulders with chronic massive rotator cuff tears. The dependent variables were superior migration of the humeral head (Hamada grades 2-3), narrowing of the glenohumeral joint (grade 4), and humeral head collapse (grade 5). Baseline variables that were significant in univariate analyses were included in multivariate models. There were 91, 59, 43, and 17 shoulders classified as Hamada grades 1, 2-3, 4, and 5, respectively. Multivariate analysis showed that infraspinatus tear (P = 0.015) and long head of biceps (LHB) tendon rupture (P = 0.007) were associated with superior migration of humeral head. Superior subscapularis tear (P = 0.003) and LHB tendon rupture (P < 0.001) were associated with narrowing of glenohumeral joint. Female sex (P = 0.006) and superior subscapularis tear (P = 0.006) were associated with humeral head collapse. This study identified the rupture of infraspinatus and LHB as risk factors of superior migration of humeral head, and the rupture of subscapularis and LHB and female sex as risk factors of cuff tear arthropathy.

Risk Factors for Loss of Active Shoulder Range of Motion in Massive Rotator Cuff Tears

Background:

Patients with massive rotator cuff tears often exhibit loss of active range of shoulder motion, which can interfere with activities of daily living. The risk factors for loss of motion remain largely unknown.

Purpose:

To clarify the predictive factors that affect the range of motion in chronic massive rotator cuff tears using multivariate analyses.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

The authors retrospectively reviewed 204 consecutive patients who were evaluated at their institution with chronic massive rotator cuff tears. In this study, the dependent variable was determined to be active anterior elevation limited to ≤90° or external rotation (ER) with the arm at the side limited to ≤0°. Explanatory variables included age; sex; affected side; duration of symptoms; smoking history; existence of diabetes, hypertension, or rheumatoid arthritis; involved tendons; presence of a 3-tendon tear; rupture of the long head of biceps tendon; superior migration of the humeral head; and cuff tear arthropathy. Baseline variables that were observed to be significant in the univariate analyses were included in multivariate models, which used logistic regression to identify independent predictors of loss of motion.

Results:

Overall, 73 patients (35.8%) exhibited limited anterior elevation, and 27 (13.2%) exhibited limited ER. Multivariate analyses showed that inferior subscapularis tear (odds ratio [OR], 14.66; 95% CI, 2.95-72.93; P = .001), smoking (OR, 4.13; 95% CI, 1.94-8.79; P < .001), superior migration of humeral head (OR, 3.92; 95% CI, 1.80-8.53; P = .001), and 3-tendon tear (OR, 3.29; 95% CI, 1.32-8.20; P = .011) were significantly associated with the loss of anterior elevation. Teres minor tear (OR, 73.37; 95% CI, 9.54-564.28; P < .001) and superior migration of the humeral head (OR, 3.55; 95% CI, 1.04-12.19; P = .044) were significantly associated with loss of ER.

Conclusion:

In the current study, a history of smoking, type of torn tendons, and superior migration of the humeral head were associated with loss of active shoulder motion. In particular, the status of inferior subscapularis or teres minor contributed to the onset of pseudoparalysis in massive rotator cuff tears.

Role of Subscapularis Tendon Repair in Reverse Total Shoulder Arthroplasty

In anatomic total shoulder arthroplasty (TSA), subscapularis repair is essential for shoulder stability and function postoperatively; however, the role of subscapularis repair in reverse TSA remains unclear. Some evidence suggests that subscapularis repair is associated with improved postoperative stability and range of motion, whereas other evidence indicates that repair is unnecessary and has no effect on clinical outcomes. In this review, we will analyze the existing literature addressing subscapularis repair during reverse TSA and discuss the effect of medialized and lateralized prosthesis designs on the utility of tendon repair.

Bankart Repair With Subscapularis Augmentation in Athletes With Shoulder Hyperlaxity

PURPOSE

The purpose of this study was to demonstrate that arthroscopic Bankart repair with associated arthroscopic subscapularis augmentation (ASA) could be a valid surgical option in the treatment of anterior shoulder instability, in collision and contact sports athletes, affected by shoulder hyperlaxity.

METHODS

In total, 591 arthroscopic Bankart repairs plus ASA were performed in 6 shoulder centers from 2009 to 2017. Inclusion criteria were the following: collision and contact sports activities, recurrent anterior instability associated with hyperlaxity and glenoid bone loss (GBL) < 15%. Exclusion criteria were GBL > 15%, voluntary instability, multidirectional instability, pre-existing osteoarthritis and throwing athletes. The minimum follow-up was 24 months. Hyperlaxity was clinically evaluated according to Neer and Coudane-Walch tests. Before surgery, all patients underwent magnetic resonance imaging and computed tomography scanning. Pico area method was used to assess the percentage of GBL. Patients were operated on by 6 surgeons, and their functional outcomes were evaluated by 2 independent observers. The Western Ontario Shoulder Instability Index (WOSI), Rowe, American Shoulder and Elbow Surgeons (ASES) scores were used to assess results.

RESULTS

Overall, 397 patients with evidence of shoulder hyperlaxity (positive sulcus sign in ER1 position and Coudane-Walch test > 85°) met all inclusion criteria. The mean WOSI score was 321; the mean Rowe score rose from 68.5 to 92.5 (P = .037), and the ASES score rose from 71.5 to 97.4 (P = .041). Seven patients (1.6%) had atraumatic redislocation, and 9 patients (2.2%) had post-traumatic redislocation. At final follow-up the mean functional deficit of external rotation was 15° with the arm in adduction (ER1 position) and 10° in abduction (ER2 position).

CONCLUSIONS

The Bankart repair plus ASA has been demonstrated to be safe and effective for restoring joint stability in patients practicing collision and contact sports or affected by chronic anterior shoulder instability associated with GBL (<15%) and hyperlaxity, without compromising external rotation.

LEVEL OF EVIDENCE

Level IV, case series.

Clinical Outcomes and Tendon Integrity in Patients With Chronic Retracted Subscapularis Tear After Arthroscopic Single-Row Oblique Mattress Suture Repair Technique

PURPOSE

To evaluate clinical outcomes and tendon integrity in patients with chronic retracted subscapularis tears using an arthroscopic single-row oblique mattress suture repair technique.

METHODS

Patients with full-thickness subscapularis tears retracted to the glenoid level and with at least 2 years of follow-up were included. Tendon retraction level was measured on preoperative axial magnetic resonance images and confirmed during arthroscopic surgery. The subscapularis tendon was repaired arthroscopically using the single-row oblique mattress suture technique on the medial margin of the lesser tuberosity. Two double-loaded suture anchors were used to obtain firm fixation between the tendon and the footprint. Clinical outcomes were assessed for all patients preoperatively and postoperatively using active range of motion, a visual analog scale score for pain, and American Shoulder and Elbow Surgeons and Constant scores. To evaluate structural integrity of the repaired tendon, all patients underwent magnetic resonance imaging at 6 months and ultrasonography at 1 year after surgery.

RESULTS

The shoulder function of the 33 patients analyzed was improved significantly after a mean follow-up period of 26.3 ± 3.5 months compared with preoperative values (American Shoulder and Elbow Surgeons score of 52.0 ± 7.9 preoperatively vs 79.6 ± 7.0 at last follow-up, P < .001, and Constant score of 43.0 ± 13.4 preoperatively vs 76.7 ± 9.2 at last follow-up, P < .001). Postoperative active range of motion improved significantly in forward flexion, external rotation, and internal rotation (P < .001). The mean visual analog scale pain score decreased by 3.42 (5.2 ± 1.6 preoperatively vs 1.9 ± 1.4 at last follow-up, P < .001). In 4 patients (12.1%), subscapularis retears were confirmed on postoperative magnetic resonance imaging.

CONCLUSIONS

Despite significant retraction, arthroscopic repair using a single-row oblique mattress suture technique in patients who had chronic subscapularis tears with retraction to the glenoid level yielded satisfactory clinical outcomes and reliable tendon healing.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Anatomy of the Subscapularis: A Review

The subscapularis is the largest and most powerful muscle of the rotator cuff. Occupying the vast majority of the subscapular fossa, it is the only internal rotator of the rotator cuff. The subscapularis innervation is classically taught as a dual innervation of 1 upper subscapular and 1 lower subscapular nerve arising from the posterior cord of the brachial plexus. However, there is a large amount of research that suggests there is significant variance in the innervation of the muscle from multiple upper subscapular nerves to multiple lower subscapular nerves arising from various portions of the plexus. Although one of the main functions of the subscapularis is to internally rotate the humerus, there is substantial evidence that displays its importance in glenohumeral stability as well. The insertion of the subscapularis is both tendinous as well as muscular. The more superior tendinous portion inserts on the lesser tuberosity while the more muscular portion inserts inferior to the less tuberosity. The medial to lateral spread of the insertion is quite variable ranging from only on the lesser tuberosity to merging with fibers from the supraspinatus. Understanding the anatomy of the subscapularis improves subscapularis management during shoulder arthroplasty including techniques for takedown, release, and repair.

Simultaneous, Bilateral Acute Subscapularis Ruptures and Their Arthroscopic Management

We present the first known case of bilateral, acute ruptures of the subscapularis tendons following a bicycle accident in a 43-year-old male. He underwent right shoulder arthroscopic, anatomic subscapularis tendon repair two weeks postinjury, with the left side staged for surgical treatment six weeks after the index procedure. Postoperatively, the patient remained in a sling for 6 weeks before advancing with therapy protocols. The interval between arthroscopic treatments allowed for independence with activities of daily living and focused, early therapy for each shoulder. This approach yielded a right-sided constant score of 89 and subjective shoulder value of 90%; the left side was 87 and 90%, respectively, at 33 months postoperatively. The patient’s only postoperative complaint was slightly diminished external rotation, a near-universal limitation after unilateral repair. This represents a successful outcome that balances functional independence, concentrated rehabilitation, and adherence to safe indications for primary repair. While bilateral traumatic shoulder injuries in a young person is a rare clinical entity, early and staged treatment can lead to good patient outcomes.

Volumetric evaluation of the rotator cuff musculature in massive rotator cuff tears with pseudoparalysis

BACKGROUND

If the balance of the rotator cuff force couple is disrupted, pseudoparalysis may occur, but the exact mechanism remains unknown. This study investigated the effect of rotator cuff force couple disruption on active range of motion in massive rotator cuff tear (mRCT) by rotator cuff muscle volume analysis.

METHODS

The study included 53 patients with irreparable mRCT: 22 in the nonpseudoparalysis group and 31 in the pseudoparalysis group. The volumes of the subscapularis (SBS), infraspinatus (ISP), and teres minor (TM) muscles were measured using magnetic resonance imaging (MRI), and the ratios of each muscle volume to the anatomic external rotator (aER) volume were calculated. A control group of 25 individuals with normal rotator cuffs was included.

RESULTS

Anterior-to-posterior cuff muscle volume ratio (SBS/ISP + TM) was imbalanced in both mRCT groups (1.383 nonpseudoparalysis and 1.302 pseudoparalysis). Between the 2 groups, the ISP/aER ratio (0.277 vs. 0.249) and the inferior SBS/aER ratio (0.426 vs. 0.390) were significantly decreased in the pseudoparalysis group (P= .022 and P= .040, respectively). However, neither the TM/aER ratio (0.357 vs. 0.376) nor the superior SBS/aER ratio (0.452 vs. 0.424) showed a significant difference between the two groups (P= .749 and P= .068, respectively). If the inferior SBS was torn, a high frequency of pseudoparalysis was noted (81.0%, P= .010).

CONCLUSION

The disruption of transverse force couple was noted in both irreparable mRCT groups, although no significant difference was found between the nonpseudoparalysis and pseudoparalysis groups. ISP and inferior SBS muscle volumes showed a significant decrease in pseudoparalysis group and, therefore, were considered to greatly influence the loss of active motion in mRCT. The TM did not exert significant effect on the incidence of pseudoparalysis.

Subscapularis tendon loading during activities of daily living

BACKGROUND

The purpose of this study was to determine the relative amount of load that is transmitted through the superior portion of the subscapularis during activities of daily living as compared with the load that is transmitted through the middle and inferior portions in a normal shoulder and in a shoulder with a supraspinatus tear.

METHODS

By use of the Newcastle shoulder model, the subscapularis was modeled with 3 lines of action encircling the humeral head. The load was measured in the entire subscapularis, and the percentage of this load in each of the 3 tendinous bands was calculated. Subsequently, a supraspinatus tear was simulated, and the forces generated by the subscapularis and glenohumeral joint contact forces were measured.

RESULTS

The maximum force produced by the entire subscapularis muscle for the various activities ranged from 3 to 43 N. Load sharing between the 3 subscapularis bands showed that the superior band bore the largest percentage of the total load of the muscle (95% ± 2%). The load in the subscapularis, particularly in the superior band, increased significantly when a supraspinatus tear was simulated (P < .0001).

CONCLUSION

The superior band of the subscapularis tendon bears the highest percentage of load compared with the middle or inferior band. The load in the subscapularis increased significantly in the presence of a simulated supraspinatus tear. Because a disproportionate amount of force is transmitted through the superior subscapularis, more clinical research is warranted to determine whether tears in this region should be routinely repaired.

Clinical Relevance of Classifying Massive Rotator Cuff Tears: Results Based on Functional and Radiological Findings After Arthroscopic Repair

BACKGROUND

Studies on the results of arthroscopic repair of massive rotator cuff tears have reported widely varied prognoses. Among other factors, the sizable discrepancy can be attributable to the fact that the current definition of massive rotator cuff tears covers an extensive area of tendons.

HYPOTHESIS

Functional and radiological results according to subgroups would show significant inter-subgroup differences preoperatively and postoperatively.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 104 patients who required arthroscopic repair for massive rotator cuff tears were prospectively evaluated. The patients were allocated into 3 groups according to tendon involvement as diagnosed by preoperative magnetic resonance imaging: group 1 (anterosuperior type involving the subscapularis and supraspinatus), group 2 (posterosuperior type involving the infraspinatus and supraspinatus), and group 3 (anteroposterior type involving the subscapularis, supraspinatus, and infraspinatus). We compared functional results (at 2 years postoperatively) and radiological findings (at 1 year postoperatively) for each group.

RESULTS

There were 34 patients in group 1, 54 in group 2, and 16 in group 3. In all 3 groups, functional results significantly improved after surgery. There were no statistically significant intergroup differences in functional results among the 3 groups. On the radiological evaluations, each group (groups 1, 2, and 3) showed a significantly different result in the preoperative acromiohumeral distance (AHD) (7.19, 5.44, and 5.22 mm, respectively), tear size (38.8, 39.3, and 46.4 mm, respectively), extent of retraction (33.9, 40.0, and 41.4 mm, respectively), postoperative AHD (8.92, 7.37, and 6.71 mm, respectively), and retear rate (23.5%, 51.9%, and 56.2%, respectively) ( P < .001 for all).

CONCLUSION

Massive rotator cuff tears can be divided into 3 types: anterosuperior (group 1), posterosuperior (group 2), and anteroposterior (group 3). Each group has distinctive characteristics and shows different results in the preoperative AHD, tear size, extent of retraction, postoperative AHD, and retear rate, which provide a reasonable basis for categorization. So far, massive rotator cuff tears have only been broadly defined, consequently being understood as a single category by many. However, to clearly understand and evaluate this injury, we suggest identifying differences within the category through proper subclassification.

The variable roles of the upper and lower subscapularis during shoulder motion

BACKGROUND

The varied roles of the subscapularis muscle as an internal rotator of the humerus, a shoulder abductor, a humeral head depressor and an anterior stabiliser may be a result of differing innervation and lines of torque between its superior and inferior components. The aims of the study were to investigate the differences in the level of muscle activation between the upper and lower subscapularis during abduction, flexion, internal and external rotation movements, and temporal characteristics during abduction and flexion.

METHODS

Intramuscular electrodes recorded electromyographic muscle activity from the upper and lower subscapularis muscles of the dominant throwing arm of twenty-four normal subjects. Participants completed ten repetitions of four shoulder movements - abduction, flexion, internal rotation and external rotation. Muscle activity was expressed as a percentage of maximum voluntary isometric contraction.

FINDINGS

The lower subscapularis was found to activate at a higher level than the subscapularis during abduction, flexion and external rotation movements and this was significant during concentric and eccentric phases of abduction and flexion (<0.001). During internal rotation, upper subscapularis muscle activity mirrored that of lower subscapularis, with a mean difference of 1.14%. Neither upper nor lower subscapularis had onset data commencing prior to the abduction movement; however upper subscapularis activated significantly later than lower subscapularis (P=0.018).

INTERPRETATION

The lower subscapularis has significantly higher muscle activity during shoulder elevation and this might reflect its greater role as a humeral head depressor and anterior stabiliser.

Relationship between massive chronic rotator cuff tear pattern and loss of active shoulder range of motion

BACKGROUND

Management of massive chronic rotator cuff tears remains controversial, with no clearly defined clinical presentation as yet. The purpose of the study was to evaluate the effect of tear size and location on active motion in patients with chronic and massive rotator cuff tears with severe muscle degeneration.

METHODS

One hundred patients with massive rotator cuff tears accompanied by muscle fatty infiltration beyond Goutallier stage 3 were prospectively included in this study. All patients were divided into 5 groups on the basis of tear pattern (supraspinatus, superior subscapularis, inferior subscapularis, infraspinatus, and teres minor). Active range of shoulder motion was assessed in each group and differences were analyzed.

RESULTS

Active elevation was significantly decreased in patients with 3 tear patterns involved. Pseudoparalysis was found in 80% of the cases with supraspinatus and complete subscapularis tears and in 45% of the cases with tears involving the supraspinatus, infraspinatus, and superior subscapularis. Loss of active external rotation was related to tears involving the infraspinatus and teres minor; loss of active internal rotation was related to tears of the subscapularis.

CONCLUSIONS

This study revealed that dysfunction of the entire subscapularis and supraspinatus or 3 rotator cuff muscles is a risk factor for pseudoparalysis. For function to be preserved in patients with massive chronic rotator cuff tears, it may be important to avoid fatty infiltration with anterior extension into the lower subscapularis or involvement of more than 2 rotator cuff muscles.

The influence of partial subscapularis tendon tears combined with supraspinatus tendon tears

BACKGROUND

With the advent of arthroscopy, more partial subscapularis tears are being recognized. The biomechanical effects of partial subscapularis tears are unknown, and there is no consensus as to their treatment. Therefore, the objective of this study was to evaluate and to quantify the changes in range of motion and glenohumeral kinematics for isolated subscapularis partial tears, combined subscapularis and supraspinatus tears, supraspinatus repair, and combined supraspinatus and subscapularis repair.

METHODS

Six cadaveric shoulders were tested in the scapular plane with 0°, 30°, and 60° shoulder abduction under 6 conditions: intact; ¼ subscapularis tear; ½ subscapularis tear; ½ subscapularis and complete supraspinatus tear; supraspinatus repair; and supraspinatus and subscapularis repair. Maximum internal and external rotation and glenohumeral kinematics were measured under physiologic muscle loading condition. A repeated measures analysis of variance with a Tukey post hoc test was used for statistical analysis.

RESULTS

Maximum external rotation was significantly increased after ¼ subscapularis tear at 30° abduction and in all abduction angles with ½ subscapularis tear (P < .05). The 2 repair conditions did not restore external rotation to the intact level. At maximum internal and external rotation, there was a significant superior shift in the humeral head apex position with ¼ subscapularis tear at 30° abduction and with ½ subscapularis tear at 60° abduction (P < .05). Repair of the supraspinatus tendon partially corrected abnormal kinematics; however, neither repair restored abnormal kinematics to intact.

CONCLUSION

Additional repair of the partial subscapularis tear with supraspinatus tear did not affect external rotation or glenohumeral kinematics. Further studies are needed to evaluate different subscapularis repair techniques.

LEVEL OF EVIDENCE

Basic science study, biomechanics.

MR imaging of subscapularis tendon injury in the setting of anterior shoulder dislocation

OBJECTIVE

To evaluate the degree and location patterns of subscapularis tendon injury in patients with prior anterior shoulder dislocation (ASD).

MATERIAL AND METHODS

Forty-five consecutive MR shoulder examinations in patients with a history of ASD and 20 consecutive MR examinations in patients without prior dislocation were reviewed. Two readers assessed for the presence and location of tendinosis and tearing in the subscapularis tendon, which was divided into three segments: superior, middle, and inferior. The readers also documented the presence of anterior labral tears, osseous Bankart defects and Hill-Sachs lesions. Fisher's exact tests were performed to analyze the different types of pathology and their locations.

RESULTS

Subscapularis tendinosis, and partial thickness and full thickness tears were more common in patients with a history of ASD. Tendinosis was found in 60-64.4% of the dislocation patients compared with 40% of the non-dislocation group. When stratified by location, the middle and inferior thirds were the most commonly affected with statistical significance (p < 0.05) found in tearing of the inferior third. Anterior labral tears, osseous Bankart defects, and Hill-Sachs lesions were more common in the dislocation group with statistically significant associations with tendinosis in the middle and inferior thirds and tearing of the middle third (p < 0.05).

CONCLUSION

Our study suggests an association between middle and inferior subscapularis tendon pathology and prior anterior shoulder dislocation. Based on our results, careful MR assessment of the subscapularis tendon by the radiologist is indicated in the setting of ASD as injury of this structure can be symptomatic and may be amenable to treatment.

Cysts within and adjacent to the lesser tuberosity: correlation with shoulder arthroscopy

OBJECTIVE

The purpose of our study was to determine if cysts in and adjacent to the lesser tuberosity are associated with rotator cuff pathology found at arthroscopy.

MATERIALS AND METHODS

A retrospective review was undertaken of the magnetic resonance (MR) imaging of 286 consecutive arthroscopic procedures performed by a single orthopedic shoulder surgeon from February 2001 to June 2009. Images of the shoulders were reviewed by an experienced fellowship-trained musculoskeletal radiologist, reader 1, and a musculoskeletal fellow, reader 2, for the presence and location of lesser tuberosity cysts. Cysts were grouped by their location into those within the lesser tuberosity and those adjacent to the lesser tuberosity. Interreader agreement was calculated using kappa values.

RESULTS

A total of 26 patients (17 men, 9 women; age range 14–84 years; mean of 61 years) had cysts in or adjacent to the lesser tuberosity. For reader 1, patients with cysts located in the lesser tuberosity were found to be significantly older(p=00.03) and more likely to have subscapularis tendon tears(p=00.02) than patients with cysts located adjacent to the tuberosity. No significant difference in any category between patients with a cyst located in the lesser tuberosity and those adjacent to the tuberosity was identified for reader 2. Interreader agreement of imaging findings ranged from fair to near perfect agreement.

CONCLUSION

Cysts located in the lesser tuberosity at the insertion of the subscapularis tendon are suggestive of subscapularis tendon pathology and may occur in older individuals.

The subscapularis: anatomy, injury, and imaging

The subscapularis is the largest and most powerful of the rotator cuff muscles and fulfills an important role in glenohumeral movement and stability. The spectrum and implications of subscapularis muscle or tendon injury differ from injury to other rotator cuff components because of its unique structure and function. Diagnosing subscapularis injury is clinically difficult and assessment of subscapularis integrity may be limited during arthroscopy or open surgery. Diagnostic imaging plays an important part in diagnosing and evaluating the extent of subscapularis injury. The radiologist should be aware of the anatomy of the subscapularis, the variations in muscle or tendon injury, and the potential implications for treatment and prognosis.

Morphology of deltoid origin and end tendons--a generic model

This study provides a model of the complex deltoid origin and end tendons, as a basis for further anatomical, biomechanical and clinical research. Although the deltoid is used in transpositions with upper limb paralysis, its detailed morphology and segmentation has not been object of much study. Morphologically, the deltoid faces two distinct challenges. It closely envelops a ball joint, and it reduces its width over a short distance from a very wide origin along clavicle, acromion and spina scapula, to an insertion as narrow as the humerus. These challenges necessitate specific morphological tendon adaptations. A qualitative model for these tendons is developed by the stepwise transformation of a unipennate muscle model into a functional deltoid muscle. Each step is the solution to one of the mentioned morphological challenges. The final model is of an end tendon consisting of a continuous succession of bipennate end tendon blades centrally interspaced by unipennate tendon parts. The origin tendon consists of lamellae that interdigitate with the end tendon blades, creating a natural segmentation. The model is illustrated by qualitative dissection results. In addition, in view of a proliferation of terms found in the literature to describe deltoid tendons, tendon concepts are reviewed and the systematic use of the unique and simple terminology of 'origin and end tendons' is proposed.

Human cadaveric study of subscapularis muscle innervation and guidelines to prevent denervation

The upper and lower subscapular nerves provide innervation to the subscapularis muscle. However, the axillary nerve may provide a significant innervation to the lower portion of the muscle. The prevalence and patterns of anomalous innervation of the subscapularis muscle were studied to determine if these variations increased the risk of muscle denervation during open shoulder surgery. Twenty human cadaveric shoulders were dissected, and the innervation to the subscapularis was defined. The distance from the nerve insertion to the shoulder joint was measured in neutral and maximal external rotation. In the most common variation, the lower subscapular nerve arose from the axillary nerve (5 specimens; 25%). Although external rotation of the shoulder brought the nerve insertion significantly more lateral (35.2 to 16.9 mm, P < .001), the origin of the nerve had no significant effect on nerve proximity to the joint. The closeness of the nerve insertions to the shoulder joint warrants care during an anterior approach to the shoulder and dissections on the anterior surface of the muscle. Subscapularis nerve damage or denervation may cause unexplained joint instability and subscapularis dysfunction.

The subscapularis footprint: an anatomic description of its insertion site

PURPOSE

The purpose of this study was to describe the anatomic footprint of the subscapularis tendon.

METHODS

We examined 19 cadaveric shoulder specimens in this study. Dissection was carried out to the level of the subscapularis through a deltopectoral approach. The subscapularis tendon was identified, and the dissection was continued, elevating the tendon, subperiosteally, from its insertion site at the lesser tuberosity. The dimensions of the footprint were measured superior to inferior, as well as medial to lateral, by a single observer.

RESULTS

The insertion of the subscapularis tendon on the lesser tuberosity was trapezoidal in shape. The mean length of the subscapularis tendon footprint was 2.5 cm (range, 1.5 to 3.0 cm). The superior portion of the footprint was the widest part of the subscapularis insertion. The mean width at the most superior aspect of the insertion site was 1.8 cm (range, 1.5 to 2.6 cm). The most inferior aspect of the footprint was much narrower, with a mean width of 0.3 cm (range, 0.1 to 0.7 cm).

CONCLUSIONS

The subscapularis insertion footprint has a broad and wide superior attachment that narrows distally to form a trapezoidal shape. We found the mean length of the footprint to be 2.5 cm. The mean superior width of the footprint was 1.8 cm, which was maintained for the upper 60% of the tendon insertion, at which point the footprint began to rapidly narrow to a minimum width of 0.3 cm at its most inferior aspect. The upper 60% of the footprint provided by far the major surface area for tendon insertion, consistent with prior findings of superior load transmission at the superior aspect of the footprint.

CLINICAL RELEVANCE

This broad attachment site superiorly is likely important in load transmission. Knowledge of the shape of the footprint of the subscapularis, with a broad superior attachment, makes it easier for the surgeon to perform an accurate anatomic surgical reconstruction of the torn subscapularis.

Ultrasound of the rotator cuff with MRI and anatomic correlation

Magnetic resonance imaging and high-resolution ultrasound (US) are frequently used for the detection of rotator cuff tears. The diagnostic yield of US is influenced by several factors as technique, knowledge of the imaging characteristics of anatomic and pathologic findings and of pitfalls. The purpose of this article is to illustrates that the standardized high-resolution US examination of the shoulder covers the entire rotator cuff and correlates with MR imaging and anatomic sections.

The influence of arthroscopic subscapularis tendon and anterior capsular release on glenohumeral translation: a biomechanical model

The effect of an arthroscopic release of the intraarticular portion of the subscapularis tendon and the anterior capsule on glenohumeral translation was investigated in a cadaveric model. Ten human cadaveric shoulders with a mean age of 63.5 years (range, 52-79 years) were tested in a robot-assisted shoulder simulator. Joint translation was measured before and after an arthroscopic release of the intraarticular portion of the subscapularis tendon and a subsequent release of the anterior capsule at 0 degrees , 30 degrees , 60 degrees , and 90 degrees of glenohumeral elevation. Translation was measured in the anterior, anterior-inferior, and inferior directions under 20 N of applied load. Testing of the specimen revealed that the release of the intraarticular portion of the subscapularis tendon and the anterior capsule increased translation in all directions. Significant increases in translation were observed after release of the intraarticular portion of the subscapularis tendon in the midrange of motion. The influence of the arthroscopic capsular release, in conjunction with the release of the subscapularis tendon, was very high above 60 degrees of elevation. The study indicates that the intraarticular component of the subscapularis tendon functions as a restraint to anterior-inferior translation primarily in the midrange of glenohumeral motion, whereas the anterior capsule adds anterior-inferior stability to the glenohumeral joint mainly above 60 degrees of elevation.

Simplified arthroscopic rotator interval capsule closure: an alternative technique

The anatomy of the "coracoid eclipse" of the rotator cuff, the rotator interval, has been studied extensively. Its importance in shoulder stability with respect to inferior and posterior translation has been described. Historically, open repairs for instability indirectly addressed interval lesions and closure based simply on the definition of the deltopectoral approach with its subscapularis advancement and capsular shift in a "pants-over-vest" manner. With results of arthroscopic repairs of glenohumeral instability approaching those of open procedures, the importance of simplification without sacrificing outcome has become a forefront in arthroscopic shoulder surgery. We present an alternative technique for interval closure by means of a 3/32-inch smooth Steinmann pin modified at its proximal and distal ends. A standard 3-portal technique consisting of the anterior superior portal, anterior mid-glenoid portal, and the posterior superior portal is used. The technique does not require the use of a suture shuttle nor does it require the placement of the arthroscope in the subacromial space for suture tying. A Tennessee slider knot is tied intra-articularly, thus allowing for tension modification before definitive alternate locking half-hitch placement. Intra-articular knot tying also allows for added security because suture slack is eliminated, thus avoiding air knots.

Subscapularis tendon tears

Pathology of the subscapularis tendon is both infrequently identified and not commonly considered as a major source of shoulder pain and dysfunction. Subscapularis tendon pathology can present as isolated tears; partial-thickness tears; anterosuperior tears, also involving the supraspinatus tendon; complete rotator cuff avulsion; and rotator interval lesions, in which instability of the long head of the biceps tendon may dominate the clinical presentation. Although an accurate physical examination is paramount, modalities such as arthroscopy, magnetic resonance imaging, and ultrasound have advanced knowledge of the spectrum of abnormalities involving the subscapularis tendon. Nonsurgical management may be effective for most partial tears. Surgically, open repair is more frequent than use of arthroscopic techniques. Tears of the subscapularis tendon portend a different prognosis than do supraspinatus tendon tears, especially when the injury is acute and diagnosis is delayed.

Quantitative assessment of thinning of the subscapularis tendon in recurrent anterior dislocation of the shoulder by use of magnetic resonance imaging

It is known that thinning and lengthening of the subscapularis tendon occur in shoulders with recurrent anterior dislocation. However, no studies have been performed to quantify the morphologic changes of the subscapularis tendon under such conditions. We retrospectively measured the thickness and cross-sectional area of the subscapularis tendon by use of magnetic resonance imaging in 22 shoulders in 11 patients with unilateral recurrent anterior dislocation of the shoulder. The contralateral shoulder in each patient served as a control. The thickness and cross-sectional area of the subscapularis on the affected side were smaller than those on the normal side (6.5 +/- 1.7 mm vs 8.0 +/- 1.9 mm, P = .001, and 388.6 +/- 120.0 mm 2 vs 547.9 +/- 128.5 mm 2 , P = .0001, respectively). We conclude that the subscapularis tendon undergoes an 18.7% decrease in thickness and a 29.1% decrease in cross-sectional area in shoulders with recurrent anterior dislocation.

The subscapular and subcoracoid bursae: descriptive and functional anatomy

The subscapularis and subcoracoid bursae, as well as the subscapularis muscle, were studied in 42 fresh cadaveric shoulders. Fibrous bands were found in the medial part of the muscle; they were intercalated with the distal tendon-like bands. The superior distal fibrous band was always found to be thicker than the others. Strong fibrous attachments of the subscapularis muscle were found along the lateral border of the scapula as well as along the medial third of the bony crests in the subscapular fossa. Between the crests, the muscle bundles were directly attached to the bone. In the lateral part of the scapula, the subscapularis muscle had only weak connective links with the bone. The subscapularis bursa was found in all cases as a pouch strongly attached to the scapular neck and the adjacent part of the joint capsule. The top of the bursa was linked to the coracoid process by a fibrous attachment called the suspensory ligament. The subcoracoid bursa had only weak connective links with the coracoid process. In 28% of cases, the subscapularis and subcoracoid bursae merged into a unique wide bursa. The subscapular bursa had two types of links with the muscle: (1). weak connective links with the superficial muscle bundles and (2). at least 2 fibrous arcs joining the lateral tendon-like bands, the bursa, and bony crests of the subscapularis fossa. These arcs allow the bursa to follow the course of the muscle exactly. During movements of the glenohumeral joint, the subscapularis muscle sustains huge changes of orientation, particularly the upper part of the muscle that coils around the coracoid process. The strong superior fibrous band enables the muscle to maintain contact with the coracoid process. It is the function of the subscapularis and subcoracoid bursae to manage the friction of the superficial fibers against the scapular neck, the humeral head, and the coracoid process.

Releases of subscapularis contracture: an anatomic and clinical study

Correction of anterior subscapularis contracture is an important step in soft-tissue balancing at the time of total shoulder replacement (TSR). An anatomic and clinical investigation was undertaken to investigate the effect of steps involved in subscapularis release. In 14 cadaveric shoulders studied, the subscapularis insertion consisted of three regions: a thick superior tubular tendon (STT), a flat middle tendon, and an inferior portion where the muscle fibers insert directly into the humerus. In 16 consecutive patients undergoing primary TSR for osteoarthritis, measurements of subscapularis length were taken after different releases. An average of 0.9 cm (confidence interval, 0.7-1.1 cm) of excursion was added after anterior capsular release, and an additional 0.7 cm (confidence interval, 0.5-0.9 cm) of excursion was obtained after STT release. Incision of the STT is an alternative means of gaining subscapularis length when balancing the soft tissues in patients with osteoarthritis undergoing TSR.

Neurohistological examination of the inferior glenohumeral ligament of the shoulder

The neural histology of the anterior band of the inferior glenohumeral ligament (IGHL) was studied in 11 fresh shoulder specimen using a special silver impregnation technique. Between the collagen fibers small myelinated and unmyelinated dendrites could be detected. The appearance of neurovascular structures in the adjacent synovial layer clearly exceeded the typical supply to soft tissues. Analysing about 11,000 sections Ruffini mechanoreceptors that are known to be slow adapting were found on the humeral insertion of the band. The sections containing these neural end organs were identified by means of transillumination and reflection-contrast microscopy and reconstructed using three-dimensional image processing. The presence of neural structures including Ruffini corpuscles in these most important passive stabilizers of the shoulder joint shows that these ligaments function also as an active safety device. There slow adaption is a prerequisite for muscular reflexes counteracting the tensile stresses to which the passive stabilizing structures of the shoulder are exposed. A disruption of the continuity of these structures by mechanical forces or surgery can reduce the biofeedback and proprioceptive quality and thus lead to a decrease of shoulder function and/or stability. These observations should be taken into account when planning surgical interventions involving the IGHL. Procedures like capsule shifts or plications may affect mechanoreceptor orientation and concentrations, thereby affecting the interaction between these structures and the synergistic muscles. When possible, these intervention should avoid receptor-dense regions while attempting to restore normal anatomical orientation and tissue tension.

Arthroscopic repair of isolated subscapularis tears: A prospective cohort with 2- to 4-year follow-up

PURPOSE

The goal of this study was to evaluate the outcomes of the arthroscopic repair of isolated subscapularis tears. Additionally, this study explores details of the clinical diagnosis, magnetic resonance arthrography findings, and surgical repair techniques.

TYPE OF STUDY

A prospective cohort.

METHODS

The preoperative and postoperative status of patients with isolated subscapularis tears were analyzed using the Constant Score, American Shoulder and Elbow Society Index (ASES Index), a visual analog pain scale (VAS), a single question of percent function compared with the opposite unaffected extremity, and a single question reflecting satisfaction: "Would you undergo the surgery and the postoperative rehabilitation to achieve the result you have today."

RESULTS

There was a statistically significant difference for all outcome measures from preoperative to postoperative follow-up at 2 to 4 years, except for the objective Constant Score. There were no differences based on gender. Preoperative magnetic resonance arthrography aids in the confirmation of the subscapularis tear.

CONCLUSIONS

The arthroscopic repair of the isolated subscapularis tear provides for reliable expectations of improvement in function, particularly the use of the arm behind the back, decreases in pain, decreases in biceps subluxation or instability, and the return of active normal internal rotation. Subjectively, magnetic resonance arthrography is better than magnetic resonance imaging for visualizing the subscapularis tear.

Arthroscopic visualization of the subscapularis tendon

PURPOSE

This study was conducted to define what portion of the subscapularis tendon is visualized during standard diagnostic glenohumeral arthroscopy and to determine the distance between the inferior aspect of the visible portion of the subscapularis tendon and the axillary nerve.

TYPE OF STUDY

Anatomic (cadaveric) analysis.

METHODS

Six fresh-frozen human cadaveric shoulders were placed in a simulated lateral decubitus position with longitudinal traction and 45 degrees of shoulder abduction. Glenohumeral arthroscopy was performed on each specimen using a standard posterior portal for visualization. The 4 corners of the visible portion of the subscapularis were tagged with arthroscopic sutures. The shoulders were subsequently dissected. The surface area defined by the 4 suture tags and the surface area of the entire subscapularis tendon were calculated for each specimen. The dimensions of these areas and the distance between the inferior aspect of the visible portion of the subscapularis tendon and the axillary nerve were measured with calipers.

RESULTS

The arthroscopically tagged portion of the subscapularis tendon represented only a small percentage (26% +/- 11%) of the entire tendon. The majority of the subscapularis tendon is veiled by the middle and inferior glenohumeral ligaments. There was a significant distance between the inferior aspect of the visible portion of the subscapularis tendon and the axillary nerve (32.8 +/- 6.0 mm). The mean height of the visible portion of the tendon represented 44% of the mean overall height of the subscapularis.

CONCLUSIONS

These data suggest that arthroscopic visualization of the subscapularis is incomplete. Lesions involving the concealed portion of the subscapularis tendon may not be detected arthroscopically. The wide margin of safety between the inferior aspect of the visible portion of the subscapularis tendon and the axillary nerve is relevant to the placement of anteroinferior (trans-subscapularis) arthroscopy portals as well as to performing arthroscopic anterior capsular releases.

The fibrous frame of the deltoid muscle. Its functional and surgical relevance

Black lines seen on magnetic resonance imaging in the middle part of the deltoid suggest the presence of fibrous bands. Anatomic study of 30 deltoid muscles was done. Eight half-cone shaped distal fibrous structures merged together into the distal tendon of the deltoid muscle. The middle part of the deltoid muscle contains four deep fibrous bands that glide inside the distal half-cones. The anterior and posterior parts of the deltoid muscle lacked such bands. Histologic study confirmed the presence of the bands and cones. In the middle part of the deltoid, muscle fibers are oblique between the bands or between the bands and the half-cones. This multipennate structure favors strength instead of range of excursion of the muscle. Because of its significant change of direction around the humeral head, at the onset of elevation of the arm, the deltoid muscle sustains forces that press the muscle against the head which then leads to deformation of the muscle. The fibrous bands make the muscle strong enough to support these forces. The middle part of the muscle is of greatest importance in comparison with the other parts. This should be considered during shoulder rehabilitation. The presence of the fibrous band originating from the anterior corner of the acromion may help create a strong repair after splitting the deltoid.

An anatomic study of the supraspinatus muscle and tendon

The gross and histologic anatomy of the myotendinous portion of the supraspinatus muscle was investigated with coronal and sagittal sections from 20 anatomic specimen shoulders. The anterior lateral portion of the supraspinatus contained more tendon than the posterior portion of the muscle in all 20 specimens. In seven specimens there were separate muscle fibers that originated from the most anteromedial area of the supraspinatus fossa. Knowledge of this anatomy aids in magnetic resonance image interpretation and open or arthroscopic evaluation of the supraspinatus. This consistent tendinous portion may be useful in rotator cuff repair and may provide a firm area for suture closure of the rotator interval. This prominent anterior tendinous area may serve to protect the supraspinatus during anterior forward flexion motion through the impingement arc.

Subscapularis, medial, and lateral head coracohumeral ligament insertion anatomy. Arthroscopic appearance and incidence of "hidden" rotator interval lesions

PURPOSE

The purpose of this study was to document the incidence of lesions of the rotator interval, illustrate the arthroscopic appearance of subtle differences in these lesions, and discuss how various lesions may affect biceps tendon stability in the bicipital groove.

TYPE OF STUDY

A Data Registry has been used in my office since 1995 (Microsoft Office Access). This study reports on the results of a retrospective database "query" of the prospectively entered data from 1995 to 1998. Thus, by default, the format of this study is a consecutive sample. Only patients with a disruption of rotator cuff tendons, labrum and/or gleno-coracohumeral ligaments are included by study design.

METHODS

This study has identified and reports on 46 arthroscopically identified subscapularis tears, 25 "hidden" rotator interval lesions (SGHL/MCHL complex) and 6 SGHL/CHL complex plastic deformation lesions in 165 patients undergoing shoulder arthroscopy for conditions ranging from anterior instability to rotator cuff tears. Arthroscopically identified lesions include partial or complete disruptions of the subscapularis tendon, disruptions of the superior glenohumeral/medial head coracohumeral ligament complex (SGHL/MCHL), disruptions of the lateral head coracohumeral ligament (LCHL), and various combinations of the above.

RESULTS

The incidence rate of subscapularis tendon involvement in 165 arthroscopically treated shoulder patients was 27%. The incidence rate of subscapularis tendon disruptions with rotator cuff pathology was 35%. The incidence rate of SGHL/MCHL lesions (tear or stretch) in 165 arthroscopically treated shoulder patients was 18%. The incidence rate of SGHL/MCHL tears in 165 arthroscopically treated shoulder patients was 15%. Forty-seven percent of all subscapularis tears involved the SGHL/CHL complex. Ten percent of all rotator cuff tears involving the supraspinatus tendon involved the LCHL.

CONCLUSIONS

This study has recorded the incidence of lesions of the subscapularis, SGHL/MCHL complex and/or the LCHL, and combinations thereof in degenerative cuff and instability patients. Primary lesions of the rotator interval can occur and regardless of the associated pathology, and if these lesions are not repaired, biceps tendon subluxation may exist.

Anatomical composition of the anterior shoulder joint capsule. A cadaver study on 12 glenohumeral joints

Twelve right cadaver shoulder joints were investigated after alcohol-formalin-glycerol fixation. The tendons of the "rotator cuff" were separated from the joint capsule. The capsulo-ligamentous structures: Lig. coracohumerale, Lig. coracoglenoidale and Ligg. glenohumeralia were dissected. In addition to the Ligg. glenohumerale superius, medium et inferius, an "unknown glenohumeral ligament" coursed in the midline of the superficial layer of the anterior shoulder joint capsule. It arose from the axillary part of the Lig. glenohumerale inferius and the insertion tendon of the Caput longum m. tricipitis brachii, coursed upwards laterally and fused with the Lig. glenohumerale medium. Between the Ligg. glenohumerale medium et inferius it was connected with the shoulder joint capsule by loose connective tissue. Craniolaterally it melted into the superior portion of the M. subscapularis and inserted together with its tendon to the Tuberculum minus of the Humerus. The ascending fibres of the "unknown glenohumeral ligament" and the oblique, descending fibres of the Ligg. glenohumeralia medium et inferius crossed twice and formed X-shape connections between the ligaments. In external rotation and abduction or anteversion the course of fibres of the "unknown glenohumeral ligament" was spiral. According to the shape and anatomical position of the "unknown glenohumeral ligament" we propose to name it "Lig. glenohumerale spirale".

Structural properties of the subscapularis tendon

The subscapularis muscle is an important mover and stabilizer of the glenohumeral joint. The purpose of this study was to measure regional variations in the structural properties of the subscapularis tendon in two joint positions. Subscapularis tendons from cadaveric shoulders were divided into four sections superiorly to inferiorly and tested to failure at 0 or 60 degrees of glenohumeral abduction. Arm position had a significant influence on stiffness in the inferior and superior portions (p < 0.05). The inferior region showed a higher stiffness in the hanging-arm position (0 degrees) than at 60 degrees of abduction (27.4+/-17.7 compared with 9.5+/-5.9 N/mm). Meanwhile, stiffness of the superior portion was higher at 60 degrees of abduction than in the hanging-arm position (208.7+/-60.9 compared with 147.2+/-32.3 N/mm). In the hanging-arm position (0 degrees) and at 60 degrees of abduction, the superior and midsuperior portions failed at significantly higher loads (superior: 623.2+/-198.6 and 478.2+/-206.6 N at 0 and 60 degrees of abduction, respectively; midsuperior: 706.2+/-164.6 and 598.4+/-268.4 N, respectively) than did the inferior portion (75.1+/-54.2 and 30.3+/-13.0 N, respectively). Likewise, stiffness of the superior and midsuperior portions was significantly higher than that of the inferior region in both positions. Higher stiffness and ultimate load in the superior tendon region may explain the infrequent extension of rotator cuff tears into the subscapularis tendon. Conversely, the significantly lower ultimate load and stiffness in the inferior tendon region could facilitate anterior dislocation of the humeral head when this portion stabilizes the joint in a dislocated position. Therefore, repair of torn inferior portions of the subscapularis tendon should be considered in surgery for glenohumeral instability.

Mechanical properties of the posterior rotator cuff

BACKGROUND

The infraspinatus is an important active and passive stabilizer of the glenohumeral joint. It functions as external rotator and participates in elevation of the arm. As its main posterior component, it is frequently involved in rotator cuff tears.

OBJECTIVE

The purpose of this study was to determine the structural and mechanical properties of the infraspinatus tendon structure, including the midsubstance and insertion regions, in the superior, mid-superior, mid-inferior, and inferior portions, in two joint positions.

METHODS

The infraspinatus tendons from 22 fresh frozen cadaver shoulders were divided into four strips. The tendons were held in a cryo-jaw and tested with a material-testing machine in 0 degrees or 60 degrees of glenohumeral abduction corresponding to 90 degrees arm abduction. Ultimate load, displacement and failure mode were recorded. Stiffness, ultimate stress and elastic modulus were calculated.

RESULTS

Significant differences between glenohumeral abduction positions were detected only for the elastic modulus. The mid-superior (676.5 N, S.D. 231.0 N) and the inferior portion (549.9 N, S.D. 284.6 N) had the highest failure loads while the superior (462.8 N, S.D. 237.2 N) and the mid-inferior portions (315.3 N, S.D. 181.5 N) were weaker. Similar trends across the tendon strips were shown for stiffness, ultimate stress and elastic modulus.

RELEVANCE

Position dependent changes in mechanical properties of the infraspinatus tendon probably do not play a role in the pathomechanism of posterior shoulder dislocation. Peaks in stiffness in mid-superior and inferior tendon sections explain the low incidence of posterior dislocations. The low ultimate failure loads in the superior portions might explain the frequent extension of rotator cuff ruptures into the infraspinatus tendon.

The intra-articular component of the subscapularis tendon: anatomic and histological correlation in reference to surgical release in patients with frozen-shoulder syndrome

Recently, arthroscopic surgical techniques have been reported for release of glenohumeral capsular contractures in selected patients with frozen-shoulder syndrome. The purpose of the current study was to assess the anatomy and histology of the subscapularis muscle, including its intra-articular component. Ten cadaveric shoulders underwent arthroscopy and dissection, and an additional 3 specimens underwent histological analysis. To provide clinical correlation, 35 patients who underwent arthroscopic capsular release completed a modified questionnaire developed by the authors. The anterior-posterior diameter and cephalad-caudad height of the intra-articular subscapularis tendon (IASS) averaged 5 mm and 11 mm, respectively. This represented 83% of the sagittal diameter and 25% of the total height of the subscapularis at the point of release. Histological analysis confirmed these anatomic observations. All patients had reduction of pain and improved function at an average of 22 months after surgery. Only 1 patient had mild subjective symptoms of instability. The current study indicates that the IASS can be released during arthroscopic capsular release for frozen shoulder with minimal risk of secondary anterior instability to the patient.

Anatomy and biomechanics of the shoulder

The anatomies and biomechanics of the glenohumeral joint and the scapulothoracic articulation are the subjects of this article. The anatomies of bones, joints, ligaments, and muscles are described in detail, and current biomechanical concepts concerning motion, stability, and force are presented. Morphologic and biomechanical changes in pathologic conditions briefly are described.

Abduction moment arm of transposed subscapularis tendon

OBJECTIVE

The purpose of this study was to analyze the effects of the procedure of superior transposition of the subscapularis on the biomechanics of glenohumeral abduction.

DESIGN

The abduction moment arms of the subscapularis muscle for the normal attachment and transposed tendon were measured on 10 cadaver shoulders and compared to that for the normal supraspinatus tendon for which it is intended to substitute.

BACKGROUND

Superior transposition of the subscapularis tendon has been recommended for surgical repair of massive tears of the rotator cuff, but the effect of this procedure on shoulder biomechanics has not been reported.

METHODS

The moment arm about an instantaneous center of rotation was derived, based on the slope of tendon excursion-glenohumeral angle curve. To simulate the insertion of the transposed subscapularis tendon, pseudo-insertion sites were created.

RESULTS

Superior transposition of the subscapularis tendon significantly increased its abduction moment arm. The effect was optimal when the simulated insertion site was lateral rather than medial and, to a lesser extent, anterior versus posterior.

CONCLUSIONS

The results provided a biomechanical rationale for subscapularis tendon transposition in restoring the loss of abduction strength of the shoulder in a massive cuff tear.