Releases of subscapularis contracture: an anatomic and clinical study

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.

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.

Muscle activities during shoulder internal rotation differ in arm position: a preliminary quantitative analysis using positron emission tomography

OBJECTIVE

To investigate the muscle activity patterns of the glenohumeral joint during internal rotation both with the arm at 0° and 90° of abduction using 2-deoxy-2-[¹⁸F] fluoro-D-glucose (FDG) positron emission tomography (PET) and magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Six healthy male volunteers underwent PET examination after performing active glenohumeral internal rotation exercise using an elastic band both with the arm at 0° and 90° of abduction. As a control, PET scan under resting condition was also performed. The exercise was performed before and after 18 fluorodeoxyglucose injection. Each PET image was fused to the corresponding MRI to identify each muscle. The standardized uptake value (SUV) of each muscle was compared between the two arm positions.

RESULTS

With the arm at 0° of abduction, the SUV increased significantly after exercise both in the middle and inferior 1/3 of the subscapularis, which were significantly higher than that of the superior 1/3 of the subscapularis (P < 0.05). The SUV of the inferior 1/3 of the subscapularis was significantly higher at 90° of abduction than at 0° of abduction and was significantly higher than that of the superior 1/3 at 90° of abduction (P < 0.01). The SUV after exercise in the inferior infraspinatus and teres minor increased.

CONCLUSIONS

The middle and inferior parts of the subscapularis are the main shoulder internal rotators in 0° of abduction, whereas the inferior part of the subscapularis is the main internal rotator in 90° of abduction.

Rehabilitation After Anatomic and Reverse Total Shoulder Arthroplasty: A Critical Analysis Review

Postoperative rehabilitation is believed to be essential in optimizing clinical outcome and function following shoulder arthroplasty. Despite this long-held notion, there is a paucity of high-quality evidence to guide rehabilitation protocols and practice. For patients undergoing anatomic total shoulder arthroplasty (ATSA), there are insufficient comparative data regarding type or duration of sling utilization. Based on current evidence, there is no appreciable benefit to early motion compared with a delayed-motion protocol following ATSA. There is insufficient literature to support the use of formal physical therapy over a physician-directed program following ATSA. At the present time, no high-quality evidence exists to guide the postoperative rehabilitation of patients undergoing reverse total shoulder arthroplasty (RTSA). Prospective randomized controlled trials evaluating postoperative management and rehabilitation following ATSA and RTSA are needed to guide best practices and optimize clinical outcomes.

Subscapularis Insufficiency: What’s All the Fuss About?

There has been increase attention to the surgical treatment of the subscapularis (SSC) tendon with risk of postoperative dysfunction and early failures following shoulder arthroplasty. Studies investigating the clinical results after shoulder arthroplasty indicate that SSC tendon detachment or incision techniques and rehabilitation concepts may impair SSC recovery and consequently the postoperative function. In response to these results, technical modifications have been proposed and evaluated anatomically, biomechanically, and clinically. The aim of this article is to give an overview of current SSC take-down approaches, subsequent repair techniques, and postoperative rehabilitation protocols as well as to present the diagnostic algorithm and clinical impacts of the increasingly acknowledged condition of SSC insufficiency following shoulder arthroplasty procedures.

Evaluation of the Translation Distance of the Glenohumeral Joint and the Function of the Rotator Cuff on Its Translation: A Cadaveric Study

PURPOSE

To evaluate the distance and position of humeral head translation during glenohumeral motion and to investigate the function of the rotator cuff in glenohumeral translation.

METHODS

Using 9 cadavers, glenohumeral translation during passive pendulum motion was tracked by an optical motion capture system. Tension was applied to 5 compartments of the rotator cuff muscles, and 7 different conditions of rotator cuff dysfunction were sequentially simulated. Three-dimensional glenohumeral structure was reconstructed from the computed tomography images of the specimens, and the distance and position of glenohumeral translation were compared among the conditions.

RESULTS

The average radius of glenohumeral translation was 10.6 ± 4.3 mm when static loading was applied to all rotator cuff muscles. The radius increased significantly in the models without traction force on the supraspinatus and total subscapularis tendons (P = .030). The position of the translation center did not change in the mediolateral direction (P = .587) and in the anteroposterior direction (P = .138), but it moved significantly superiorly in the models without supraspinatus and infraspinatus loading (P = .011) and in those without supraspinatus, infraspinatus, and teres minor loading (P < .001).

CONCLUSIONS

The distance and position of humeral head translation during glenohumeral motion changed with rotator cuff deficiency. The present study indicated that the subscapularis plays an important role in maintaining the central position of the humeral head, and that the infraspinatus acts as a major depressor of the humeral head during shoulder motion.

CLINICAL RELEVANCE

The results of this study suggest that extension of a tear into the subscapularis should be avoided to maintain the centering function of the glenohumeral joint in cases with rotator cuff tear.

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.

Management of the subscapularis tendon during total shoulder arthroplasty

Use of total shoulder arthroplasty has significantly increased during the past decade. For anatomic total shoulder arthroplasty, controversy exists regarding the best technique for detachment and repair of the subscapularis tendon. Options include tendon tenotomy, peel, lesser tuberosity osteotomy, and even subscapularis-sparing techniques. Inadequate healing of the subscapularis tendon can lead to postoperative pain, weakness, and instability. This review discusses the subscapularis pathoanatomy, different techniques for releasing and repairing the tendon, and reports biomechanical and clinical outcomes for each technique after total shoulder arthroplasty.

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.

Patterns of strain and the determination of the safe arc of motion after subscapularis repair--A biomechanical study

This study characterizes the strain patterns and safe arcs for passive range of motion (ROM) in the superior and inferior subscapularis tendon in seven cadaveric shoulders, mounted for controlled ROM, after deltopectoral approach to the glenohumeral joint, including tenotomy of the subscapularis tendon 1 cm medial to its insertion on the lesser tuberosity. The tenotomy was repaired with end-to-end suture in neutral rotation. Strain patterns were measured during passive ROM in external rotation (ER), ER with 30° abduction (ER+30), abduction, and forward flexion in the scapular plane (SP) before and after surgery. Percentages were calculated from 35 trials corresponding to five trials of each motion across seven specimens. With ER of 0-30°, 89% of trials of superior subscapularis tendon and 100% of trials of inferior subscapularis tendon achieved strains >3%, with very similar patterns noted in ER+30. In abduction of 0-90°, 5.8% of trials of superior and 85.3% of trials of inferior tendon achieved >3% strain. With passive ROM in SP, 26.5% of trials reached 3% strain in superior tendon compared to 100% in inferior tendon. Strain patterns in abduction and SP differed significantly (p < 0.001). Selective tenotomy and repair of the superior subscapularis tendon with open reparative or reconstructive shoulder procedures, when feasible, may be favorable for protected early passive ROM and rehabilitation postoperatively.

Deltopectoral approach for shoulder arthroplasty: anatomic basis

PURPOSE

The deltopectoral approach is a common surgical procedure for shoulder arthroplasty. Many surgeons are familiar with this procedure, but certain steps are still controversial. This is the case for the management of subscapularis, where surgeons must choose between tenotomy and the lesser tuberosity osteotomy.

METHODS

This article is conceived as a toolkit for the inexperienced surgeons, describing our tips and tricks to facilitate final exposure of the glenoid. For experienced surgeons, we analysed the tricky portions of the deltopectoral approach, comparing them with what is classically reported in the literature.

RESULTS

We describe an original technic for subscapularis reattachment after lesser tuberosity osteotomy in order to improve its stability. The medial part of the fragment is secondarily sculpted to obtain a step shape, which will be applied against the base of the prosthetic cup in a sort of "corner buttress".

CONCLUSIONS

Our work, based on our personal experience, confirms that there is no preferred single deltopectoral approach but, rather, multiple options. When embarking on this "shoulder highway", we encourage surgeons to respect the successive anatomic planes, which we believe is the only way to ensure easy and atraumatic dissection.

KEY POINTS

- The safe plane for going around the humeral head and positioning retractors is the plane of the subacromial deltoid bursa. - Always stay close to the bone during capsule release, whether on the humeral or glenoid side. - Never go medially to the conjoint tendon or its deep face.

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.

Long-term subscapularis strength assessment after Bristow-Latarjet procedure: isometric study

BACKGROUND

The subscapularis is the strongest rotator cuff muscle. Bristow-Latarjet procedure may impair subscapularis function. The aim of the study is to describe the difference in isometric subscapularis (SSC) strength after L-shape tenotomy versus muscle split in patients who underwent to Bristow-Latarjet procedure.

MATERIALS AND METHODS

From 2000 to 2006, we enrolled 376 patients for Bristow-Latarjet procedures. We identified 2 groups according to the subscapularis approach. Group A included 264 subjects with subscapularis L shape tenotomy; group B included 112 subjects with subscapularis muscle split. The subscapularis function was assessed with lift-off and belly-press tests. Isometric strength of rotator cuff muscle was assessed at an average follow-up of 45 months in group A and 42 months in group B, recording the maximum isometric peak torque (PT) (N), maximum isometric couple (Nm), relative strength index (N/Kg), strength, couple and external/internal rotator ratio. Constant and Rowe were used as scores.

RESULTS

Subscapularis assessment in the overall population showed 33 cases (8.8%) with a positive Lift-off test and 30 cases (8%) with a positive belly-press test. Rowe and Constant scores increased in both groups (P < .01). The mean PT in group A was lower of 24,8 Nw than group B (P < .01); similarly, the max PT values of group A were lower of 26.1 Nw than group B (P < .01).

CONCLUSION

L-shaped tenotomy in Bristow-Latarjet procedure has a weakening effect on the subscapularis and for these reasons we strongly recommend the muscle split approach for an optimal subscapularis function recovery.

Subscapularis management in open shoulder surgery

Management of the subscapularis in open shoulder surgery is a controversial topic. Subscapularis tenotomy has been the traditional approach, but other techniques have recently been developed to preserve the integrity of the subscapularis tendon. These include subscapularis peel, subscapularis split, and lesser tuberosity osteotomy. The biologic healing and biomechanical properties associated with each surgical approach must be evaluated to determine the best option for each patient. A strong, anatomic repair is required to achieve optimal clinical outcomes.

Clinical, radiographic, and ultrasonographic comparison of subscapularis tenotomy and lesser tuberosity osteotomy for total shoulder arthroplasty

BACKGROUND

Recently, a lesser tuberosity osteotomy has been promoted as an alternative to tenotomy for release of the subscapularis during shoulder arthroplasty. To our knowledge, no direct comparison of the clinical results of the two techniques has been presented.

METHODS

Thirty-five shoulders in thirty-four consecutive patients with osteoarthritis who had a primary total shoulder arthroplasty, performed with use of a standard subscapularis tenotomy (Group 1) or lesser tuberosity osteotomy (Group 2) to release the subscapularis, were evaluated retrospectively at an average of thirty-three months. Group 1 consisted of fifteen shoulders in fourteen patients (seven in males and eight in females, with an average age of sixty-seven years). Group 2 consisted of twenty shoulders in twenty patients (fourteen males and six females, with an average age of sixty-nine years). Assessment included a physical examination, clinical outcome questionnaires, conventional radiography, ultrasound examination of the subscapularis, and measurement of internal rotation strength.

RESULTS

The postoperative total Penn Shoulder Scores improved significantly from the preoperative levels in both groups (mean and standard deviation, 29 +/- 15 points to 81 +/- 20 points [p < 0.00001] in Group 1 and 29 +/- 16 points to 92 +/- 11 points [p < 0.00001] in Group 2). However, the postoperative mean total Penn Shoulder Score was higher in Group 2 (92 +/- 11 points) than in Group 1 (81 +/- 20 points) (p = 0.04). At one year, an abnormal subscapularis on ultrasound was associated with a lower mean Penn Shoulder Score in Group 1 (73 +/- 19 points compared with 92 +/- 3 points; p = 0.01). However, at a minimum two-year follow-up, this difference was not significant (mean, 74 +/- 24 points and 86 +/- 15 points, respectively; p = 0.25). There were more abnormal subscapularis tendons in Group 1 (six attenuated tendons and one full-thickness tear) than in Group 2 (two attenuated tendons). Internal rotation strength did not differ between the groups when controlled for sex (mean, 117 +/- 8 N and 127 +/- 21 N for males in Group 1 and Group 2, respectively [p = 0.22] and 77 +/- 27 N and 101 +/- 26 N, respectively, for females [p = 0.1]).

CONCLUSIONS

Both techniques resulted in improved clinical outcome scores. The lesser tuberosity osteotomy resulted in higher clinical outcome scores, a lower rate of subscapularis tendon tears, and universal healing of the osteotomy. This technique offers a means by which the rate of postoperative subscapularis tears may be reduced in patients undergoing total shoulder arthroplasty.

Subscapularis lengthening in shoulder arthroplasty

PURPOSE

To report the technique and outcome of subscapularis (SSC) lengthening in shoulder arthroplasty.

PROCEDURE

When external rotation measures less than 20 degrees, a coronal subscapularis lengthening is performed. This utilizes the interval between the anterior shoulder capsule and subscapularis to titrate the correct amount of anatomic length.

RESULTS

Average preoperative passive ER was -2 degrees. Average postoperative ER was 48 degrees. Belly press was graded as normal in 13 pts, mild in 12 pts, and poor in 2 pts.

CONCLUSION

Subscapularis tendon lengthening provides a large surface area for tendon healing and allows anatomic length to be restored. Subscapularis lengthening may preserve a better length-tension relationship of the SSC muscle in shoulders with significant IR contracture undergoing shoulder arthroplasty.

Primary total shoulder arthroplasty performed entirely thru the rotator interval: technique and minimum two-year outcomes

BACKGROUND

Total shoulder replacement (TSR) is an effective treatment of shoulder arthritis. However, subscapularis insufficiency after TSR remains a significant cause of poor outcomes after shoulder arthroplasty. We describe a novel technique for performing a TSR entirely through the rotator interval (RI) without tenotomy of the subscapularis or supraspinatus tendons and without dislocating the shoulder using the superior approach.

MATERIAL AND METHODS

We prospectively followed up 22 patients who underwent this procedure. Subjective patient satisfaction, Constant, Simple Shoulder Test (SST) scores, and range of motion (ROM) were evaluated preoperatively and postoperatively at a mean follow-up of 29 months. Radiographic findings are also presented.

RESULTS

Subjective patient satisfaction results were good in 5 of 17 patients and excellent in 12. Patients also had significant increases in Constant, visual analog scale, SST, and ROM scores. One patient was excluded due to a traumatic periprosthetic fracture (fall), 3 patients refused to return for follow-up, and 1 patient was lost to follow-up. Postoperative results included nonanatomic humeral head osteotomies in 6, residual inferior humeral neck osteophytes in 8, and the humeral head prosthesis was undersized in 5.

CONCLUSIONS

The patients had favorable clinical outcomes. This technique for TSR demonstrates that in the postoperative period, patients can immediately partake in unrestricted physical therapy. This study reports the clinical outcomes of this technique for TSR with a minimum of 2 years of follow-up.

LEVEL OF EVIDENCE

Level 4; Case series, treatment study.

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.

Subscapularis dysfunction following anterior surgical approaches to the shoulder

Subscapularis dysfunction following open surgical exposure of the glenohumeral joint has recently received attention. Clinical studies, in particular those that have investigated the results after open shoulder stabilization or shoulder replacement surgery, indicate that anterior approaches using different subscapularis tendon take-down or incision techniques may impair subscapularis recovery and can negatively influence the final clinical outcome. This review article will focus on the potential pathogenesis, diagnosis, and clinical impact of this more and more recognized condition and summarizes the currently available literature.

Subscapularis function after total shoulder replacement: results with lesser tuberosity osteotomy

Until recently, little consideration was placed on the integrity of the subscapularis tendon after total shoulder arthroplasty. We have noted that several of our patients exhibited loss of internal rotation strength and subscapularis function after total shoulder arthroplasty utilizing an anatomic soft tissue repair of the subscapularis, both with and without bone tunnels. On the basis of those results, we began removing the subscapularis with a small piece of bone by a lesser tuberosity osteotomy in an attempt to achieve improved subscapularis function through bony healing at the repair site. A retrospective review of 28 patients (30 shoulders) was done of patients who had total shoulder arthroplasty performed between 2001 and 2003. The lesser tuberosity and attached subscapularis were repaired through bone tunnels in all cases. The mean follow-up was 1.1 years. Terminal internal rotation was evaluated by the belly-press examination. Subscapularis function was assessed by the patient's ability to tuck in a shirt behind the back, and 25 of 30 patients (83.3%) reported no difficulty. Belly-press examination results were normal in 18 of 30 patients (60%). Removal of the subscapularis through a lesser tuberosity osteotomy results in reliable restoration of internal rotation strength after total shoulder arthroplasty, as measured by the ability to perform a stomach press and to tuck in a shirt. In comparing these results with our earlier cohort of patients with similar demographics and postoperative rehabilitation that had soft tissue repair, improved results were seen in the group that underwent lesser tuberosity osteotomy.

A Cadaveric Study of Strain on the Subscapularis Muscle

OBJECTIVES

To measure the strain on 3 fiber groups of the subscapularis muscle at various glenohumeral joint positions and to determine the appropriate shoulder position for subscapularis muscle stretching.

DESIGN

Repeated-measures design.

SETTING

Biomechanics laboratory.

SPECIMENS

Nine frozen-thawed glenohumeral joints obtained from 9 fresh cadavers.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

The strain on the upper, middle, and lower fiber groups of the subscapularis were measured by precise displacement sensors during 14 different glenohumeral joint positions.

RESULTS

The glenohumeral joint position that showed the largest strain varied among the 3 fiber groups. Although no position showed significantly large strain on the upper and middle fiber groups, external rotation at 30 degrees , 60 degrees , and 90 degrees of elevation, abduction, flexion, and horizontal abduction revealed significantly greater strain on the lower fiber groups (P<.005). Additionally, except for external rotation at 0 degrees of elevation, the strain on the lower fiber group was significantly greater than that on the upper and middle fiber groups in external rotation (P<.005).

CONCLUSIONS

The stretching position of each fiber group of the subscapularis differs depending on the glenohumeral joint position. External rotation at 30 degrees to 60 degrees of glenohumeral elevation, abduction, flexion, and horizontal abduction can significantly stretch the lower fiber group of the subscapularis muscle.

Biomechanical evaluation of subscapularis repair used during shoulder arthroplasty

Dysfunction of the subscapularis after total shoulder replacement has become concerning and may represent poor tendon healing after surgical repair. The objectives of this study were to evaluate the restoration of subscapularis footprint anatomy and failure strength for subscapularis repair via transosseous tunnels and a second anatomic repair via combined transosseous tunnels and direct tendon-to-tendon repair. Six matched pairs of fresh-frozen human cadaveric shoulders were used, with one shoulder from each pair randomly assigned to a transosseous repair and the contralateral shoulder assigned to a combined transosseous tunnel and direct tendon-to-tendon repair. The repair footprint was digitized. Cyclic loading to the tendon repair was performed followed by a constant ramp displacement to complete failure. The transosseous tunnel repair insertional footprint area (228.6 mm2) was significantly less than that of the native footprint (697.3 mm2), and the footprint centroid moved 9.1 mm medially (P = .0001) and 5.5 mm superiorly (P = .003). The combined repair required a statistically significantly greater number of cycles (P = .028) to reach a 5-mm gap (205.7 +/- 65.1) than did the isolated transosseous tunnel technique (76.4 +/- 34.2). A similar greater number of cycles was observed for the 10-mm gap (P = .01) for combined repair (307.5 +/- 82.4) compared with isolated transosseous repair (166.2 +/- 85.8). This study has shown that transosseous tunnel repair alters subscapularis insertional anatomy, resulting in weaker strength of fixation and less contact area when compared with combined transosseous tunnel and direct tendon-to-tendon repair.

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.