Tears at the myotendinous junction of the infraspinatus: Ultrasound findings

A Case Report on Myotendinous Junction

Myotendinous junction is the transition zone between the muscle and its tendon. Hence, it is subject to immense stress within the muscle. In this study, it is found that muscles having a greater tensile have a more arranged myotendinous junction compared to muscles with lesser tensile strength. Cadaveric specimens - plantaris, gastrocnemius, and soleus have been histologically studied to study the same.

Emerging Role of Quantitative Ultrasound-Based Imaging Techniques for Characterizing Rotator Cuff Tears: A Scoping Review

Rotator cuff myosteatosis following cuff tears is very common and one of the most important prognostic factors in clinical management. Quantitative ultrasound-based imaging techniques (QUBIT) are frequently used along with magnetic resonance imaging (MRI) to evaluate rotator cuff fatty degeneration. However, the examination of rotator cuff tissue integrity by QUBIT is lacking a standardized imaging protocol and procedural methodologies. In this scoping review, we synthesized the current state of QUBIT against the reference imaging modalities in patients with rotator cuff tears. The literature search was extracted from 963 studies, with 22 studies included in the final review in accordance with the preferred reporting items for systematic reviews and meta-analyses extensions for scoping reviews. The selected studies included human participants and focused on measuring at least one prognostic or diagnostic factor using ultrasonography-based imaging with reference to MRI. The findings suggest both conventional B-mode ultrasound and shear wave elastography imaging were comparable to MRI-based imaging techniques for the evaluation of fatty infiltration and rotator cuff tear characterization. This review establishes guidelines for reporting shoulder-specific QUBIT aimed at developing a standardized imaging protocol. The objective was to enhance the diagnostic and prognostic capabilities of QUBIT in the clinical setting.

Myotendinous Junction: Exercise Protocols Can Positively Influence Their Development in Rats

The myotendinous junction (MTJ) is an interface that different stimuli alter their morphology. One of the main stimuli to promote alterations in the MTJ morphology is physical exercise. The present study aimed to investigate the morphology and molecular MTJ adaptations of biceps brachii muscle in adult Wistar rats submitted to different ladder-based protocols. Forty Wistar rats (90 days old) were divided into four groups: Sedentary (S), Climbing (C), Overload Climbing (OC), Climbing, and Overload Climbing (COC). The results of light microscopy demonstrated the cell and collagen tissue reorganization in the experimental groups. The sarcomeres lengths of different regions showed a particular development according to the specific protocols. The sarcoplasmic invaginations and evaginations demonstrated positive increases that promoted the myotendinous interface development. In the extracellular matrix, the structures presented an increase principally in the COC group. Finally, the immunofluorescence analysis showed the telocytes disposition adjacent to the MTJ region in all experimental groups, revealing their network organization. Thus, we concluded that the different protocols contributed to the morphological adaptations with beneficial effects in distinct ways of tissue and cellular development and can be used as a model for MTJ remodeling to future proteomic and genetic analysis.

Hernando M, Abascal F, Cerezal L. Myotendinous junction tear of the anterior bundle of the supraspinatus muscle—a rare pattern of injury involving rotator cuff muscles

Myotendinous junction injuries are rare and often present with distinctive imaging findings that should be differentiated from purely tendinous degenerative ruptures.

Myotendinous junction tears are common in the lower limb but rarely involve rotator cuff muscles. Considering rotator cuff muscles, the infraspinatus and supraspinatus muscles are the most frequently implicated.

The intrinsic anatomy of the supraspinatus muscle gives it a greater contractile force and consequently a propensity for rupture. It is composed of two bundles: anterior and posterior (with the latest further divided in a deep anterior, a medial and a superficial posterior portion). These two components have distinctive anatomy with the anterior bundle having a long intramuscular tendon and bipennate configuration and the posterior bundle having a smaller intramuscular tendon and parallel muscle fibres. This distinctive anatomy grants a greater contractile force to the anterior bundle of the supraspinatus muscle and for this reason it is more prone to myotendinous rupture.

This type of injury has been associated with a rapid progression to severe fatty infiltration and should be differentiated from purely tendinous tears that are more frequent and associated with degenerative changes. Myotendinous tears occur centrally located in the muscle belly and are not associated with full thickness tears of the distal tendon attachment.

A case series of recurrent myotendinous rotator cuff tears repaired and augmented with dermal allograft: clinical outcomes at two years

When rotator cuff tears occur after a primary repair at the footprint, they often fail medially at the myotendinous junction, also called type II tears. These are difficult tears to treat, and little research has been published on how to address tears at the myotendinous junction and the clinical outcomes of the revised repairs. The purpose of this study is to evaluate the outcomes of type II rotator cuff tears repaired with a dermal allograft augmentation.

MATERIALS AND METHODS

We conducted a retrospective chart review of 9 patients with a type II rotator cuff tear medially at the myotendinous junction, arthroscopically repaired and augmented with acellular dermal allograft by a single surgeon. Two-year follow-up was obtained to evaluate pain, function, range of motion, and structural integrity of the repair via ultrasound.

RESULTS

Of all 9 patients, the mean visual analog scale preoperatively was 5.1 (standard error, ±2.1). With 9 patients having 2-year follow-up, the mean visual analog scale score continued to improve to 1.9 (standard error, ±2.4). At 2 years, the mean American Shoulder and Elbow Surgeons based on 8 patients was 76.1, and the mean Short Form 36 for all 9 patients was 78.7. All 9 patients with 2-year follow-up had an intact repair on ultrasound read by a musculoskeletal fellowship-trained radiologist.

DISCUSSION

Based on the early outcome data, patient satisfaction scores, and intact repairs visualized on ultrasound at 2 years postoperatively, the use of acellular human dermal matrix augmentation appears to be an efficacious and worthwhile treatment option for patients with recurrent rotator cuff tears at the medial myotendinous junction.

Myotendinous junction adaptations to ladder-based resistance training: identification of a new telocyte niche

The present study shows chronic adjustments in the myotendinous junction (MTJ) in response to different ladder-based resistance training (LRT) protocols. Thirty adult male Wistar rats were divided into groups: sedentary (S), calisthenics (LRT without additional load [C]), and resistance-trained (LRT with extra weight [R]). We demonstrated longer lengths of sarcoplasmatic invaginations in the trained groups; however, evaginations were seen mainly in group R. We showed a greater thickness of sarcoplasmatic invaginations in groups C and R, in addition to greater evaginations in R. We also observed thinner basal lamina in trained groups. The support collagen layer (SCL) adjacent to the MTJ and the diameters of the transverse fibrils were larger in R. We also discovered a niche of telocytes in the MTJ with electron micrographs of the plantar muscle and with immunostaining with CD34+ in the gastrocnemius muscle near the blood vessels and pericytes. We concluded that the continuous adjustments in the MTJ ultrastructure were the result of tissue plasticity induced by LRT, which is causally related to muscle hypertrophy and, consequently, to the remodeling of the contact interface. Also, we reveal the existence of a collagen layer adjacent to MTJ and discover a new micro anatomic location of telocytes.

Efficacy of Imaging Modalities Assessing Fatty Infiltration in Rotator Cuff Tears

BACKGROUND

Fatty atrophy is a diagnosis characterized by the combination of fatty infiltration and muscle atrophy of the rotator cuff. Studies have shown a strong positive correlation between the level of fatty infiltration and the risk of experiencing a chronic rotator cuff tear. Therefore, the purpose of the present study was to review the current literature on radiographic imaging of fatty infiltration and fatty atrophy to better aid surgeons in predicting functional outcome and to help guide patient decisions.

METHODS

We conducted a literature search in PubMed. The exact search queries included "rotator cuff" in the MeSH Terms field; "fatty atrophy," fatty infiltration," and "fatty muscle degeneration" in the Title/Abstract field; and various combinations of these searches. We initially found 184 articles using these keywords, including both human and animal studies. The 25 animal studies were excluded, leaving 159 articles. The abstracts of all remaining articles were reviewed and selected on the basis of our inclusion criteria of focusing on patients with rotator cuff tears (preoperatively and postoperatively), fatty infiltration, fatty atrophy, and imaging modalities. We excluded an additional 127 articles, leaving 32 articles that were selected for the final review and inclusion in this study.

RESULTS

Among 45 shoulder specialists across different studies, interrater agreement for Goutallier staging with use of magnetic resonance imaging (MRI) ranged from 0.24 to 0.82 and intrarater agreement for supraspinatus fatty changes ranged from 0.34 to 0.89. Our review also showed strong positive correlations when assessing the severity of fatty atrophy of the rotator cuff between MRI and ultrasound or ultrasound modalities such as sonoelastography.

CONCLUSIONS

Increasing fatty infiltration of the rotator cuff is associated with greater repair failure rates and hence poorer overall clinical outcomes. MRI remains the gold standard for the imaging of rotator cuff tears and postoperative healing. Ultrasound can decrease health-care expenditures associated with the assessment of repair integrity postoperatively, although ultrasound is not as precise and has some limitations compared with MRI.

Supraspinatus Myotendinous Junction Injuries: MRI Findings and Prevalence

OBJECTIVE

The purpose of this study is to describe the MRI findings and evaluate the prevalence of supraspinatus myotendinous injuries.

MATERIALS AND METHODS

Among 1001 consecutive shoulders that underwent either conventional MRI or MR arthrography between January and December 2016, 843 shoulders were included. All MR images were retrospectively analyzed for identification and classification into the appropriate grade of acute or chronic rotator cuff myotendinous injuries. Other MRI findings, such as the presence of rotator cuff tendon insertional tears, and clinical information were also evaluated.

RESULTS

At MRI, 0.47% (4/843) of shoulders had supraspinatus myotendinous injuries involving the anterior muscular bundle exclusively. Chronic grade III (n = 2), acute grade III (n = 1), and acute grade II (n = 1) injuries were identified in three men and one woman (mean age, 44 years) with a clinical history of trauma (n = 2) or of progressive shoulder pain (n = 2). A concurrent supraspinatus insertional tendon tear with either partial (n = 1) or full (n = 1) thickness was present in half the cases. Loss of tension of the myotendinous junction in grade III myotendinous junction injuries led to severe atrophy and fatty infiltration of the anterior supraspinatus.

CONCLUSION

Supraspinatus myotendinous junction injuries are uncommon at MRI. These lesions invariably involve the anterior bundle of the supraspinatus muscle and may occur with a concomitant insertional tendon tear. High-grade chronic injuries lead to selective atrophy and fatty infiltration of the anterior supraspinatus muscle.

Arthroscopic Intramuscular Side-to-Side Repair of an Isolated Infraspinatus Tear

Intramuscular, full-thickness rotator cuff tears are uncommon and present a challenging clinical scenario for repair because traditional suture anchor or transosseous repair techniques are less feasible. The goal of repair is to achieve a tension-free reduction of both ends of the muscle to allow for adequate healing over time. Intramuscular tears of the infraspinatus specifically have rarely been reported. The clinical presentation of these patients can be challenging to interpret, and other causes of rotator cuff dysfunction, including compression to the suprascapular nerve, must be ruled out. In this Technical Note, we describe our technique for arthroscopic side-to-side suture repair of an isolated intramuscular infraspinatus tear.

Rotator Cuff Tears at the Musculotendinous Junction: Classification and Surgical Options for Repair and Reconstruction

Although uncommon, rotator cuff tears that occur medially at the musculotendinous junction can result from acute trauma, anatomic force imbalance, or medial row cuff failure following a previous rotator cuff repair. The quality of the torn muscle and tendon along with the length of the remnant tendon stump should be considered before deciding on the most appropriate repair technique. When muscle and tendon quality are sufficient, the tear can often be repaired directly to the remnant tendon stump and compressed onto the greater tuberosity. If the remnant tendon stump is degenerative, of insufficient length, or lacks tendon in which to place sutures, an allograft patch can be used to augment the repair. When the quality of the remaining muscle and tendon are poor or when the muscle is retracted too far medially and is nonmobile, a bridging technique such as superior capsule reconstruction is preferable. The purpose of this report is to (1) highlight that medial cuff failure can occur both primarily and after previous repair; (2) define and classify the 3 major tear patterns that are encountered, and (3) describe the authors' preferred techniques for medial cuff repair that specifically address each of the major tear patterns.

Delaminating infraspinatus tendon tears with differential retraction: imaging features and surgical relevance

OBJECTIVE

To describe infraspinatus tendon injuries with associated intramuscular edema in light of more recently elucidated anatomical knowledge.

MATERIAL AND METHODS

A retrospective review was performed to identify MRI cases with infraspinatus tendon injury accompanied by muscle edema. MR images were reviewed to evaluate the location of the injury, to assess the degree of tendon retraction, and to assess for muscular changes. Clinical and surgical data were reviewed when available.

RESULTS

Twenty-three patients were identified (13 males, 10 females, mean age of 52 years). MRI demonstrated infraspinatus muscle edema in all cases with variably retracted infraspinatus tendon fibers. Three patients (13 %) presented acutely after traumatic falls, 11 patients (48 %) presented after a minor trauma or recalled event, and 9 patients (39 %) presented with more chronic symptoms. Of the nine patients who underwent arthroscopic surgery, six patients (67 %) did not have an identifiable corresponding lesion, despite the findings described on the preoperative MRI. In these six cases, some superficial fibers of the transverse portion of the infraspinatus tendon remained intact on the MRI. Three patients (13 %) had follow-up MRI examinations with one progressing to severe muscle atrophy, one without progression of existing muscle atrophy, and one with no atrophy on the initial or subsequent evaluation. Eighteen of 23 patients had concomitant partial-thickness or full-thickness tears of the adjacent supraspinatus tendon.

CONCLUSION

Injuries of the infraspinatus tendon with resultant muscle edema and variable muscle atrophy may, in fact, represent delaminating type injuries with differential retraction of a layered tendon and may be missed on arthroscopy.