A new look at the shoulder anterior capsuloligamentous complex complementing the insertion of the subscapularis tendon—Anatomical, histological and ultrasound studies of the lesser tuberosity enthesis

Surgical anatomical landmarks for arthroscopic repair of subscapularis tendon tears

BACKGROUND

Subscapularis repair has recently garnered significant interest. A thorough understanding of the tendon's anatomy is essential for precise and safe repair. Our objectives were to describe the anatomy of the subscapularis insertion, define its landmarks, and analyze nearby structures to guide arthroscopic repair.

METHODS

We conducted an anatomical study, dissecting 12 shoulders. We evaluated the distance from the footprint to the axillary nerve, the dimensions, and shape of the footprint, and its relationship with the humeral cartilage.

RESULTS

The distance to the axillary nerve was 32 mm (standard deviation [SD], 3.7 mm). The craniocaudal length of the footprint was 37.3 mm (SD, 4.6 mm). Its largest mediolateral thickness was 16 mm (SD, 2.2 mm), wider at the top and narrower distally. The distance between the footprint and the cartilage varied, being 3.2 mm (SD, 1.2 mm) in the upper part, 5.4 mm (SD, 1.8 mm) in the medium, and 15.9 mm (SD, 2.9 mm) in the lower part.

CONCLUSIONS

When performing a repair of the subscapularis tendon, the distance to the cartilage should be carefully evaluated as it varies proximally to distally, and the shape of the footprint (wider proximally, tapered distally) should be considered for implant positioning. The distance to the axillary nerve is approximately 30 mm. Anterior visualization guarantees direct control of all landmarks and allows accurate implant positioning with safe tendon release. Level of evidence: IV.

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.

Permeable spaces between glenohumeral ligaments as potential gateways for rapid regional anesthesia of the shoulder

Shoulder pain is a highly prevalent condition, often resulting in major life limitations, and requiring effective treatments. In this work, we explore the anatomical basis of a proposed approach to the regional anesthesia of the shoulder through a single injection under the subscapularis muscle. Bilateral experimental injections in shoulders from body donors (Radiolar ® and Methylene-Blue) under the subscapular muscle (n = 11) and cadaveric systematic dissections of other 35 shoulders from body donors were performed. Injectate spread was then qualitatively assessed. Long axis of permeable foramina in the anterior aspect of the shoulder joint capsule was measured in centimeters using a digital caliper. More than 40% of specimens had at least one permeable space (Weitbrech and/or Rouvière foramina) communicating the subscapular bursa and the articular space. We further demonstrate that an ultrasonography-guided injection under the subscapularis muscle allows the spread of the injectate through the anterior, inferior and posterodorsal walls of the articular capsule, the subacromial bursa, and the bicipital groove, as well as into the articular space for some injections. The odds of accidental intraarticular injection decrease when injecting with low volumes. This anatomical study provides a detailed description of foramina between glenohumeral ligaments. Furthermore, the data shown in this work supports, as a proof of concept, a safe alternative for rapid and specific blockade of terminal sensory branches innervating the shoulder joint capsule.

Superior Capsular Reconstruction Provides Sufficient Biomechanical Outcomes for Massive, Irreparable Rotator Cuff Tears: A Systematic Review

PURPOSE

To critically review the literature reporting biomechanical outcomes of superior capsular reconstruction (SCR) for the treatment of massive and/or irreparable rotator cuff tears.

METHODS

A systematic review was performed following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines using the PubMed, MEDLINE, and Cochrane Library databases in August 2020. Cadaveric studies were assessed for glenohumeral translation, subacromial contact pressure, and superior humeral translation comparing SCR with an intact cuff with reference to a torn control state.

RESULTS

A total of 15 studies (142 shoulders) were included in our data analysis. SCR showed improvements in superior humeral translation, subacromial contact force, and glenohumeral contact force when biomechanically compared with the massive and/or irreparably torn rotator cuff. No statistically significant differences were found between SCR and the intact rotator cuff regarding superior humeral translation (standard mean difference [SMD], 2.09 mm vs 2.50 mm; P = .54) or subacromial contact force (SMD, 2.85 mPa vs 2.83 mPa; P = .99). Significant differences were observed between SCR and the intact cuff for glenohumeral contact force only, in favor of the intact cuff (SMD, 1.73 N vs 5.45 N; P = .03).

CONCLUSIONS

SCR may largely restore static restraints to superior humeral translation in irreparable rotator cuff tears, although active glenohumeral compression is diminished relative to the intact rotator cuff.

CLINICAL RELEVANCE

Investigating the biomechanical outcomes of SCR will help surgeons better understand the effectiveness of this treatment option.

Anterior shoulder anatomy and subcoracoid impingement: An anatomical study

OBJECTIVE

The aim of our study was to describe the anatomy of the anterior shoulder, specifically structures potentially involved in subscapularis tears pathophysiology and also to identify structures at risk during surgical approaches of this area.

MATERIALS AND METHODS

We designed an observational, experimental study based on cadaveric models. Dissection was performed and several structures of the anterior shoulder were characterized including the subscapularis, coracoid morphology, the coracoacromial ligament, coraco-humeral distance, and the axillary and musculocutaneous nerves.

RESULTS

Our sample included 16 shoulders. The coracoacromial ligament presented two bands in 37.5%, and these variants were significantly wider and thinner, and were associated with inferior coraco-humeral distance in internal rotation. The subscapularis footprint was longer and the coracoid process was bigger in male specimens, and the median coracoid angle was 122°, corresponding to a Leite-Torres type I. The Subscapularis showed a median thickness of 0.7cm, while the coraco-humeral distance in our sample ranged from 0.30cm in internal rotation to 0.85cm in external rotation. Neurologic relevant structures were at least more than 2.55cm from the coracoid tip.

CONCLUSIONS

This is the first paper to explore the eventual relationship between the presence of a double band coracoacromial ligament variant and subcoracoid impingement. Also, to our knowledge, this is the first cadaveric model study to postulate a possible anatomic base for subcoracoid impingement, as the SS myotendinous junction thickness was found to be greater than the coraco-humeral distance in neutral position and in IR.

Novel and effective arthroscopic extracapsular stabilization technique for anterior shoulder instability-BLS

PURPOSE

Arthroscopic Bankart repair for the treatment of anterior shoulder instability is associated with a high rate of recurrent instability. Extracapsular stabilization of the glenohumeral joint with enhancement of anterior wall soft tissues may be an effective alternative treatment technique. The aim of this study is to retrospectively assess clinical outcomes in the treatment of anterior shoulder instability using a novel technique of anterior extracapsular stabilization-"between glenohumeral ligaments and subscapularis tendon" (BLS).

METHODS

Patients with anterior shoulder instability who underwent surgical treatment with a novel arthroscopic BLS technique between 2008 and 2016 were eligible for inclusion. According to the level of glenoid bone loss, patients were separated into four groups. Group 1 comprised patients with GBL equal to or less than 5%, group 2 patients with GBL 6-10%, group 3 patients with GBL 11-15%, and group 4 patients with GBL > 15%. A positive outcome in this study was defined as full restoration of joint stability. To evaluate clinical results, preoperative range of ER and IR measured in 90 degrees of abduction were compared with ER and IR measured at final follow-up. Additional outcome instruments used consisted of the Constant Score and the Walch-Duplay Score.

RESULTS

A total of 150 patients underwent arthroscopic BLS surgery. During the study period, 50 patients were lost to follow-up and 100 patients were available for final analysis. Mean patient age was 27.5 (± 10.3) years at the time of surgery. Mean duration of follow-up was 82.9 (± 29.4) months. At final assessment, 86 patients (86%) were categorized as having a positive outcome, with full restoration of joint stability. Recurrence of shoulder instability was observed in 14 (14%) patients, including 6 (6%) cases that were associated with major trauma. At final follow-up, the mean Constant Score was 88.2 ± 10.1, compared to 82.9 ± 9.1 preoperatively (p < 0.05). The mean final and mean preoperative Walch-Duplay Scores were 81.5 ± 18.9 and 52.2 ± 11.9, respectively (p < 0.05). There was no statistically significant limitation of external or internal rotation.

CONCLUSIONS

The BLS technique has been shown to be an effective method to anterior shoulder instability in patients without significant glenoid bone loss. It was shown that this technique provides significant improvement in shoulder function without reducing shoulder range of motion.

LEVEL OF EVIDENCE

IV.

Systematic Review of the Anatomic Descriptions of the Glenohumeral Ligaments: A Call for Further Quantitative Studies

PURPOSE

To perform a systematic review of the glenohumeral ligament anatomic attachments on the glenoid and humeral neck.

METHODS

A systematic review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, PubMed, MEDLINE, and Embase from 1980 to present. The inclusion criteria were as follows: cadaveric or clinical anatomic studies that qualitatively or quantitatively described the glenoid and humeral attachments of the glenohumeral ligaments in the English-language literature. Imaging and animal studies, editorial articles, and surveys were excluded from this study.

RESULTS

The 15 included studies analyzed a total of 983 shoulders. Only 5 studies reported quantitative measurements. The most common glenoid superior glenohumeral ligament attachment described was in the anterolateral region of the supraglenoid tubercle and was inserting on the humerus in close vicinity to the subscapularis tendon insertion. The superior labrum and lesser tuberosity were the most commonly reported middle glenohumeral ligament attachments. The inferior glenohumeral ligament was most commonly described to attach between the 2- and 4-o'clock positions of the glenoid and distally near the surgical neck of the humerus.

CONCLUSIONS

There were limited quantitative data on the attachments of the glenohumeral ligaments. Although the literature was discordant, the most common descriptions of the attachments were as follows: The anterolateral region of the supraglenoid tubercle, the superior labrum, and the glenoid (between the 2- and 4-o'clock positions) were the medial attachments for the superior glenohumeral ligament, middle glenohumeral ligament, and inferior glenohumeral ligament, respectively. Laterally, they inserted on the humerus in close vicinity to the subscapularis tendon insertion, on the lesser tuberosity, and near the surgical neck of the humerus, respectively.

CLINICAL RELEVANCE

The glenohumeral ligaments are important anatomic structures contributing to the dynamic stability of the glenohumeral joint. Further detailed quantitative descriptions of their attachments are required for truly anatomically based repairs.

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.

Subscapularis Management in Total Shoulder Arthroplasty: Current Evidence Comparing Peel, Osteotomy, and Tenotomy

The optimal approach to management of the subscapularis in total shoulder arthroplasty (TSA) is controversial. Options include the subscapularis tenotomy, lesser tuberosity osteotomy (LTO), and peel. This review provides a summary of subscapularis anatomy and function, outcomes associated with subscapularis management options in TSA, and postoperative subscapularis deficiency. Based on the available literature, LTO appears to result in improved function and subscapularis integrity relative to tenotomy, while peel and LTO have generally led to equivalent outcomes. The highest level of evidence to date is derived from a randomized controlled trial that demonstrated that outcomes following peel and LTO were not significantly different. There is currently a paucity of high-quality evidence as most studies have consisted of small retrospective series with varying outcome measures. Furthermore, the optimal approach to establishing the diagnosis of subscapularis deficiency following TSA is unclear.

Subject-specific shoulder muscle attachment region prediction using statistical shape models: A validity study

Subject-specific musculoskeletal models can predict accurate joint and muscle biomechanics thereby helping clinicians and surgeons. Current modeling strategies do not incorporate accurate subject-specific muscle parameters. This study reports a statistical shape model (SSM) based method to predict subject-specific muscle attachment regions on shoulder bones and illustrates the concurrent validity of the predictions. Augmented SSMs of scapula and humerus bones were built using bone meshes and five muscle attachment (origin/insertion) regions which play important role in the shoulder motion and function. Muscle attachments included Subscapularis, Supraspinatus, Infraspinatus, Teres Major and Teres Minor on both the bones. The regions were represented by subset of vertices on the bone meshes and were tracked using vertex identifiers. Subject-specific muscle attachment regions were predicted using external set of bones not used in building the SSMs. Validity of predictions was determined by visual inspection and also by using four similarity measures between predicted and manually segmented regions. Excellent concurrent validity was found indicating the higher accuracy of predictions. This method can be effectively employed in modeling pipelines or in automatic segmentation of medical images. Further validations are warranted on all the muscles of the shoulder complex.

The Rotator Cuff and the Superior Capsule: Why We Need Both

Tears of the rotator cuff are frequent. An estimated 250,000 to 500,000 repairs are performed annually in the United States. Rotator cuff repairs have been successful despite fatty infiltration and atrophy of the rotator cuff muscles. Although the emphasis in rotator cuff repair has historically focused on re-establishing the tendon attachment, there is growing interest in and understanding of the role of the superior capsule. The superior capsule is attached to the undersurface of the supraspinatus and infraspinatus muscle-tendon units, and it resists superior translation of the humeral head. Herein, we propose that it is the defect in the superior capsule that is the "essential lesion" in a superior rotator cuff tear, as opposed to the defect in the rotator cuff itself. We propose that rotator cuff repair must restore the normal capsular anatomy to provide normal biomechanics of the joint and thus a positive clinical outcome.