Clinical and structural results of open repair of an isolated one-tendon tear of the rotator cuff

BACKGROUND: The clinical outcomes of open rotator cuff repair are well established, but the structural results and their effect on clinical outcome are poorly known. We assessed the structural changes in the musculotendinous units after open rotator cuff repair and correlated these findings with the clinical outcome to establish a benchmark for future series. METHODS: Thirty-two consecutive standardized open repairs of a single tendon tear of the rotator cuff were analyzed in twenty-one men and eleven women with an average age of 59.0 years. The supraspinatus tendon was involved in twenty-two patients and the subscapularis tendon, in ten. The clinical outcome, including the Constant score, was assessed prospectively for all patients at an average of thirty-eight months postoperatively. The structural outcome was assessed on standardized magnetic resonance imaging scans. RESULTS: The mean overall subjective shoulder value was 82.8% of the value for a normal shoulder. On the average, the age and gender-adjusted Constant score increased from 63.9% preoperatively to 94.5% postoperatively (p < 0.0001); the score for pain, from 6.8 points to 13.2 points (p < 0.0001); and the score for activities of daily living, from 11.2 points to 17.9 points (p < 0.0001). The overall rerupture rate was 13% (four of the thirty-two shoulders). All reruptures were distinctly smaller than the original tear. Muscular atrophy or fatty infiltration did not significantly decrease after the tendon repair. In fact, fatty infiltration in the supraspinatus (p < 0.0053) and infraspinatus (p < 0.003) muscles increased significantly. CONCLUSIONS: Direct open repair of a complete, isolated tear of one tendon of the rotator cuff resulted in significant subjective and objective improvement and very high patient satisfaction. Successful direct repair was not associated with a decrease in preoperative muscular atrophy and was associated with increased fatty infiltration of the muscle.     

Magnetic resonance imaging of arthroscopic supraspinatus tendon repair

BACKGROUND: While a number of studies have documented the very good clinical results of arthroscopic rotator cuff repair, very few authors have specifically assessed cuff integrity, supraspinatus atrophy, and fatty infiltration and their influence on the clinical outcome. METHODS: We evaluated fifty-three consecutive patients (average age, 60.9 years) who had undergone arthroscopic repair of an isolated supraspinatus tendon tear. After an average duration of follow-up of 26.4 months, all patients were evaluated clinically with use of the Constant score and underwent standardized magnetic resonance imaging at our institution. The preoperative and postoperative magnetic resonance images were evaluated by two independent observers who were blinded to the clinical outcome of the patient. Evaluation criteria were cuff integrity; atrophy of the supraspinatus; and fatty infiltration of the supraspinatus, infraspinatus, and subscapularis. These findings were correlated to the clinical outcome. RESULTS: Regardless of the tendon integrity, every parameter of the Constant score was significantly improved after the repair. The overall average Constant score was improved from 53.5 to 83.4 points (p < 0.001). The retear rate in our series was 25% (thirteen of fifty-three). Patients who had a retear had significantly less abduction strength (p = 0.043) and a significantly lower total Constant score (p = 0.012) than those who had an intact repair. A higher degree of preoperative supraspinatus atrophy and Stage-2 fatty infiltration of the supraspinatus were positive predictors of a retear. Also, an older age was an important predictor of a retear (p = 0.011). Progression of structural changes in the rotator cuff was halted when the repair remained intact, but there was no significant reversal of fatty infiltration or muscle atrophy. When the repairs failed, there was significant progression of fatty infiltration and atrophy of the supraspinatus. CONCLUSIONS: The clinical and structural results of arthroscopic repairs of isolated supraspinatus tears are equal to those reported following open repair. Fatty infiltration and muscle atrophy cannot be reversed by successful arthroscopic repair. Higher degrees of muscular atrophy and fatty infiltration preoperatively are associated with recurrence of the tear as well as progression of fatty infiltration and muscular atrophy and an inferior clinical result.     

Botulinum toxin is detrimental to repair of a chronic rotator cuff tear in a rabbit model

Re‐tear continues to be a problem after rotator cuff repair. Intramuscular botulinum toxin (Botox) injection can help optimize tension at the repair site to promote healing but could have an adverse effect on the degenerated muscle in a chronic tear. We hypothesized that Botox injection would improve repair characteristics without adverse effect on the muscle in a chronic rotator cuff tear model. The supraspinatus tendon of both shoulders in 14 rabbits underwent delayed repair 12 weeks after transection. One shoulder was treated with intramuscular Botox injection and the other with a saline control injection. Six weeks after repair, outcomes were based on biomechanics, histology, and magnetic resonance imaging. Botox‐treated repairs were significantly weaker (2.64 N) than control repairs (5.51 N, p = 0.03). Eighty percent of Botox‐treated repairs and 40% of control repairs healed with some partial defect. Fatty infiltration of the supraspinatus was present in all shoulders (Goutallier Grade 3 or 4) but was increased in the setting of Botox. This study provides additional support for the rabbit supraspinatus model of chronic cuff tear, showing consistent fatty infiltration. Contrary to our hypothesis, Botox had a negative effect on repair strength and might increase fatty infiltration. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1152–1157, 2015.     

Correlation of atrophy and fatty infiltration on strength and integrity of rotator cuff repairs: a study in thirteen patients

In 13 patients, the development of supraspinatus muscle atrophy and fatty infiltration after rotator cuff tendon repair was quantified prospectively via magnetic resonance imaging. Intraoperative electrical nerve stimulation at repair showed that the maximal supraspinatus tension (up to 200 N) strongly correlated with the anatomic cross-sectional muscle area and with muscle fatty infiltration (ranging from 12 N/cm(2) in Goutallier stage 3 to 42 N/cm(2) in Goutallier stage 0). Within 1 year after successful tendon repair (n = 8), fatty infiltration did not recover, and atrophy improved partially at best; however, if the repair failed (n = 5), atrophy and fatty infiltration progressed significantly. The ability of the rotator cuff muscles to develop tension not only correlates with their atrophy but also closely correlates with their degree of fatty infiltration. With current repair techniques, atrophy and fatty infiltration appear to be irreversible, despite successful tendon repair. Unexpectedly, not only weak but also very strong muscles are at risk for repair failure.     

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.     

Isolated supraspinatus muscle atrophy and fatty infiltration associated with recurrent anterior shoulder instability: A case report and review of the literature

Supraspinatus muscle atrophy and fatty infiltration are two distinct muscle abnormalities which can be seen after a chronic massive tear or suprascapular neuropathy. Isolated supraspinatus muscle denervation due to suprascapular nerve injury after shoulder dislocation is extremely rare. We report on a patient who developed isolated supraspinatus muscle atrophy and fatty infiltration after traumatic anterior shoulder instability. Possible explanations and etiologies of this rare condition are discussed in this report.     

Rabbit supraspinatus motor endplates are unaffected by a rotator cuff tear

Rotator cuff tears are a major cause of morbidity. Following rotator cuff tears, muscle atrophy and fatty infiltration begin in the tissue, limiting repair potential and leading to a higher re‐tear rate and a worse functional outcome. We evaluated whether fatty degeneration resulting from a complete supraspinatus tear with retraction is associated with an injury to the suprascapular nerve. Four skeletally mature New Zealand white rabbits were randomized to receive an index procedure on either their right or left shoulder with the opposite shoulder serving as a control. At the index procedure, the supraspinatus tendon was transected at its insertion and allowed to retract. At 3 months, the rabbits were euthanized, and both supraspinatus muscles were harvested. The specimens were then examined with confocal microscopy and histology. Atrophy was grossly visible in all four test muscles, and fatty infiltration was confirmed with osmium tetroxide staining. In all four rabbits, the degree of denervation (p = 0.71) and partial denervation (p = 0.91) was not significantly different between control and experimental muscle. Rotator cuff tear does not affect the motor endplate or innervation status of the supraspinatus. Fatty infiltration occurs independent of denervation of the supraspinatus. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:99–104, 2012     

Atrophy of the supraspinatus belly Assessment by MRI in 55 patients with rotator cuff pathology

A study of 5 fresh cadaveric shoulders demonstrated that an oblique-sagittal plane which crosses the scapula through the medial border of the coracoid process offers a view of the supraspinatus fossa mostly limited by bone.This view could easily be reproduced by MRI and we called it the Y-shaped view. It allowed a reliable measurement of supraspinatus muscle atrophy by the calculation of the occupation ratio (R) which is the ratio between the surface of the cross-section of the muscle belly and that of the fossa.This ratio was calculated in a prospective study based on 55 shoulders divided into 3 groups with different rotator cuff status: group I, 15 controls; group II, 10 degenerative cuffs, without tears; group III, 30 operated tears. There was no difference between groups I (mean ratio 0.7) and II (mean ratio 0.62), but the ratio was decreased in group III (mean ratio 0.44), in which the extent of the tear in both the sagittal and coronal planes aggravated the muscle atrophy. We propose a three-stage classification to improve indications for rotator cuff tear treatment.     

Ruptures of the supraspinatus tendon: Cadaver dissection

Ninety-nine shoulders from 50 deceased with an average age of 73 years were dissected. There was a significant decrease in the thickness of the supraspinatus tendons with full thickness ruptures but not in partial ruptures. A highly significant increase in the length of the extramuscular supraspinatus tendon in shoulders with partial or full thickness supraspinatus ruptures was found. However, the total length of the supraspinatus aponeurosis was the same in shoulders with ruptures as in normal shoulders of the same age. This might indicate that the increase in length of the extramuscular portion of the tendon in ruptures is not caused by elongation of the tendon but is the result of muscular decay.     

An anatomic study of the effects on the suprascapular nerve due to retraction of the supraspinatus muscle after a rotator cuff tear

The purpose of this anatomic study was to assess the risk to the suprascapular nerve by measuring the tension on the nerve and the angle between the nerve and its motor branch at the scapular notch with medial supraspinatus tendon retraction. Twelve shoulders in six cadavers were dissected to evaluate the branching point of the first motor branch of the suprascapular nerve, the change in angle between the nerve and its first motor branch at the scapular notch with retraction of the supraspinatus tendon, and the resulting tension on the nerve. The first motor branch originated at the notch in 9 cadavers, just proximal in 1, and just distal in 2. With the supraspinatus muscle in its anatomic position, the suprascapular nerve and its first motor branch angle measured 142.6 degrees at the scapular notch. After retraction of the supraspinatus, the angle markedly decreased to 98.7 degrees and 34.6 degrees with 1 cm and 5 cm of medial retraction, respectively. The motor branch was taut in all specimens at 2 to 3 cm of retraction. Medial retraction of the supraspinatus tendon drastically changes the course of the suprascapular nerve through the scapular notch, creating increased tension on the nerve. The degree of rotator cuff muscle atrophy frequently observed after a massive tear may be explained by increased tension on the nerve due to muscle retraction.     

Atrophy of the rotator cuff muscles and site of cuff tears

We determined the relationship between the site of rotator cuff tears and atrophy of the cuff muscles. 28 shoulders (28 patients) had rotator cuff tears: 19 isolated tears of the supraspinatus tendon (isolatedtear group) and 9 combined tears of the supraspinatus and infraspinatus tendons (combined-tear group). The cross-sectional area of the subscapularis, supraspinatus, the infraspinatus and teres minor muscles in the coronal oblique MR images were measured before and after surgery. Although we found no difference in tear size, the cross-sectional areas of the muscles were smaller in the combined-tear group than in the isolated-tear group. We conclude that atrophy of the supraspinatus and infraspinatus muscles also depends on the site of the tear.     

Atrophy of the rotator cuff muscles and site of cuff tears

We determined the relationship between the site of rotator cuff tears and atrophy of the cuff muscles. 28 shoulders (28 patients) had rotator cuff tears: 19 isolated tears of the supraspinatus tendon (isolated-tear group) and 9 combined tears of the supraspinatus and infraspinatus tendons (combined-tear group). The cross-sectional area of the subscapularis, supraspinatus, the infraspinatus and teres minor muscles in the coronal oblique MR images were measured before and after surgery. Although we found no difference in tear size, the cross-sectional areas of the muscles were smaller in the combined-tear group than in the isolated-tear group. We conclude that atrophy of the supraspinatus and infraspinatus muscles also depends on the site of the tear.     

A rat model of massive rotator cuff tears

Rotator cuff tears (RCTs) are the most common tendon injury seen in orthopedic patients. Massive RCT does not heal spontaneously and results in poor clinical outcomes. Muscle atrophy and fatty infiltration in rotator cuff muscles are major complications of chronic massive RCT and are thought to be the key factors responsible for the failure of attempted massive RCT repair. However, the pathophysiology of rotator cuff muscle atrophy and fat infiltration remains largely unknown, and no small animal model has been shown to reproduce the histologic and molecular changes seen in massive RCT. In this article, we report a novel rat massive RCT model, in which significant and consistent muscle atrophy and fat infiltration were observed in the rotator cuff muscles after rotator cuff tendon transection and denervation. The supraspinatus and infraspinatus muscle lost 25.4% and 28.9% of their wet weight 2 weeks after complete tendon transection, respectively. Six weeks after surgery, the average wet weight of supraspinatus and infraspinatus muscles decreased 13.2% and 28.3%, respectively. Significant fat infiltration was only observed in infraspinatus 6 weeks after tendon transection. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:588–595, 2011     

Lower muscle regenerative potential in full-thickness supraspinatus tears compared to partial-thickness tears

Background and purpose Rotator cuff tears are associated with secondary rotator cuff muscle pathology, which is definitive for the prognosis of rotator cuff repair. There is little information regarding the early histological and immunohistochemical nature of these muscle changes in humans. We analyzed muscle biopsies from patients with supraspinatus tendon tears.

Methods Supraspinatus muscle biopsies were obtained from 24 patients undergoing arthroscopic repair of partial- or full-thickness supraspinatus tendon tears. Tissue was formalin-fixed and processed for histology (for assessment of fatty infiltration and other degenerative changes) or immunohistochemistry (to identify satellite cells (CD56+), proliferating cells (Ki67+), and myofibers containing predominantly type 1 or 2 myosin heavy chain (MHC)). Myofiber diameters and the relative content of MHC1 and MHC2 were determined morphometrically.

Results Degenerative changes were present in both patient groups (partial and full-thickness tears). Patients with full-thickness tears had a reduced density of satellite cells, fewer proliferating cells, atrophy of MHC1+ and MHC2+ myofibers, and reduced MHC1 content.

Interpretation Full-thickness tears show significantly reduced muscle proliferative capacity, myofiber atrophy, and loss of MHC1 content compared to partial-thickness supraspinatus tendon tears.     

Effect of tendon release and delayed repair on the structure of the muscles of the rotator cuff: an experimental study in sheep

BACKGROUND: Ruptures of the tendons of the rotator cuff lead to profound and possibly irreversible changes in the structure and physiological properties of the rotator cuff muscles. Muscle atrophy and fatty infiltration are important prognostic factors that affect the natural history and outcome of treatment. The purpose of this study was to examine the amount of muscle atrophy and fatty infiltration in an animal model and to determine whether the repair of a long-standing tendon tear can reverse these changes. METHODS: The infraspinatus tendon in six sheep was released and encased in a silicone tube to prevent spontaneous healing. The musculotendinous unit was allowed to retract for forty weeks. Throughout this period, the muscular changes were studied with use of computed tomography, histological analysis, and electron microscopy. At forty weeks, the elasticity, intramuscular pressure, and perfusion were measured intraoperatively and a tendon repair was carried out. The structural changes of the muscle were studied for thirty-five weeks after the repair. The animals were then killed, and the musculotendinous units were examined macroscopically and by computed tomography, histological analysis, and electron microscopy. RESULTS: At the time of the tendon release, the infraspinatus showed no fatty changes. The force needed to cause a tendon excursion of 1 cm was a mean (and standard deviation) of 6.8 +/- 1 N. The application of tension on the tendon did not alter the perfusion and decreased the intramuscular pressure. After the tendon release, muscular atrophy developed and there was a significant increase (p < 0.001) in interfascicular and intrafascicular fat, representing fatty infiltration rather than fatty degeneration. Furthermore, there was an increase of interstitial connective tissue. At the time of the tendon repair, between forty and forty-two weeks after the release, there was a sevenfold poorer elasticity of the musculotendinous unit but preserved muscle perfusion. The structural changes increased six weeks after the repair and then recovered partially at twelve and thirty-five weeks thereafter but only to the amount demonstrated before the repair. CONCLUSIONS: Musculotendinous retraction induced by tendon release is associated with profound changes in the structure and function of the affected muscle. Vascularization, intramuscular pressure, and individual fiber composition are not markedly affected, and muscle fibers do not appear to degenerate. However, muscle atrophy, infiltration by fat cells, and an increase of interstitial connective tissue lead to impairment of the physiological properties of the muscle. These changes were irreversible under the conditions of this experiment with the repair technique used.     

The influence of rotator cuff disease on the results of shoulder arthroplasty for primary osteoarthritis: results of a multicenter study

BACKGROUND: Rotator cuff disease is uncommon in primary glenohumeral osteoarthritis. Consequently, the prognostic implications of rotator cuff disease in patients undergoing prosthetic replacement for the treatment of primary glenohumeral osteoarthritis are uncertain. The purpose of this study was to report the effects of the condition of the supraspinatus tendon and the rotator cuff musculature on the results of shoulder arthroplasty in the treatment of primary osteoarthritis. METHODS: Five hundred and fifty-five shoulders in 514 patients who had an arthroplasty for the treatment of primary glenohumeral osteoarthritis as part of a multicenter study were evaluated. Forty-one shoulders had a partial-thickness tear of the supraspinatus, and forty-two had a full-thickness tear. Ninety shoulders had moderate (stage-2) fatty degeneration of the infraspinatus, and nineteen had severe (stage-3 or 4) degeneration. Eighty-four shoulders had moderate fatty degeneration of the subscapularis, and fifteen had severe degeneration. The influence of the condition of the supraspinatus tendon and the infraspinatus and subscapularis musculature on the postoperative outcome was evaluated with respect to the scores according to the system of Constant and Murley, active mobility, subjective satisfaction, radiographic result, and rate of complications. RESULTS: The shoulders were evaluated at a mean of 43.1 months postoperatively. With the numbers available, supraspinatus tears were not found to influence the postoperative outcome with respect to the total Constant score, active mobility, subjective satisfaction, radiographic result, or rate of complications. Additionally, the treatment of these tears did not markedly influence the outcome parameters. Conversely, both shoulders with moderate fatty degeneration and those with severe degeneration of the infraspinatus were associated with poorer results than those with no degeneration with respect to the total Constant score (p < 0.0005), active external rotation (p < 0.0005), active forward flexion (p = 0.001), and subjective satisfaction (p = 0.031). Similar although less dramatic results were seen with fatty degeneration of the subscapularis. CONCLUSIONS: This study demonstrates that minimally retracted or nonretracted rotator cuff tears that are limited to the supraspinatus tendon do not appreciably affect most shoulder-specific outcome parameters in shoulder arthroplasty performed for the treatment of primary osteoarthritis. Conversely, fatty degeneration of the infraspinatus and, less importantly, subscapularis musculature adversely affects many of these parameters.     

Editorial Commentary: Monitoring Tendon and Muscle Recovery After Rotator Cuff Repair Using Diagnostic Ultrasound Demonstrates that Early Repair is Beneficial for Many Patients With Reparable Tears

Rotator cuff repair is performed to effect healing of the enthesis; to restore shoulder comfort, strength, and function; to prevent tear propagation; and to prevent progression of atrophic muscle changes (fatty degeneration, fatty infiltration, and fatty atrophy) that eventually occur. Non-retracted and moderately retracted rotator cuff tears usually heal after repair, and muscle atrophy may recover over time. It follows that early rotator cuff repair is beneficial for many patients with chronic but reparable rotator cuff tears. Diagnostic ultrasound can provide quantitative information about the recovery of both muscle and tendon and represents a viable alternative to magnetic resonance imaging for evaluating healing after rotator cuff repair.     

Cross-sectional area of the tendon and the muscle of the biceps brachii in shoulders with rotator cuff tears

Background The intraarticular portion of the long head of the biceps tendon is often widened in shoulders with cuff tears. It is unclear whether this is a local phenomen or is caused by muscle hypertrophy.

Methods We investigated morphological changes of the biceps brachii in 14 embalmed shoulders: 7 with intact rotator cuff and 7 with rotator cuff tears.

We measured the cross-sectional area (CSA) of the tendon of the long head of the biceps (LHB) at 9 levels between the glenoid origin and the musculotendinous junction. The muscle volume and the muscle fiber length of the long and short heads of the biceps were measured to calculate the physiological CSA (PCSA) by dividing the volume by the fiber length.

Results The CSA of the LHB tendon at the entrance to the bicipital groove was greater in cuff tear shoulders than in normal shoulders. The PCSA of the biceps was similar in normal and cuff tear shoulders.

Interpretation Hypertrophy of the LHB tendon appears to be a localized morphological change near the entrance to the bicipital groove.