Biomechanical Comparison of 3 Glenoid-Side Fixation Techniques for Superior Capsular Reconstruction

BACKGROUND

Superior capsular reconstruction (SCR) was recently introduced as a treatment for irreparable superior rotator cuff tears in younger patients. Purpose/Hypothesis: The purpose was to assess the biomechanical strength of 3 methods for fixation of the graft to the glenoid for SCR. It was hypothesized that a 4-anchor technique would provide greater load to failure than 3-anchor techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-six cadaveric specimens were randomized into 3 groups of previously established glenoid-side graft fixation techniques: (1) three 3.5-mm knotless screw-in anchors, (2) three 3.0-mm knotless push-in anchors, and (3) a 4-anchor hybrid construct with two 3.0-mm knotted push-in anchors and two 2.9-mm knotless push-in anchors. The repairs were cyclically loaded at 0.5 Hz from 10 to 200 N, then pulled to failure. Elongation, stiffness, maximum load at failure, and mode of failure were recorded and calculated.

RESULTS

There were no significant differences in graft elongation or stiffness among the 3 techniques ( P > .37 and P > .26, respectively). Maximum load to failure was significantly greater in technique 1 (mean ± SD, 427.85 ± 119.70 N) than technique 3 (319.5 ± 57.60 N) ( P = 0.024). There were no significant differences in load to failure between techniques 1 and 2 or between techniques 2 and 3.

CONCLUSION

Glenoid-side graft fixation with 3 threaded 3.5-mm suture anchors showed a significant superior pull-out strength when compared with a 4-anchor hybrid technique and thus might be recommended in SCR for patients with irreparable superior rotator cuff tears to achieve maximum stability.

CLINICAL RELEVANCE

SCR presents a novel alternative for treatment of irreparable superior rotator cuff tears in younger patients. Glenoid fixation is essential to provide adequate fixation of the graft to prevent the humeral head from rising and to restore normal biomechanics.

Fatty infiltration of stage 1 or higher significantly compromises long-term healing of supraspinatus repairs

BACKGROUND

Fatty infiltration (FI) compromises outcomes of rotator cuff repairs. Most clinicians consider FI of the infraspinatus, whether it is torn or intact, because it is most rapidly affected. The purpose of this study was to report long-term outcomes of isolated supraspinatus repairs and to determine their associations with FI of the infraspinatus and supraspinatus.

METHODS

The records of 182 patients who underwent repair of isolated supraspinatus tears and had preoperative magnetic resonance imaging were retrieved. Of these, 147 patients were evaluated at 10 years' follow-up using the Constant score and magnetic resonance imaging scans.

RESULTS

Preoperative FI was greater in the supraspinatus (52% stage ≥1) than in the infraspinatus (29% stage ≥1). The 10-year Constant scores were influenced by FI of the supraspinatus (P = .006) but not of the infraspinatus (P = .422). Multivariable regression confirmed that Constant scores were significantly lower for female patients, repetitive work, and stage 1 and stage 2 FI of the supraspinatus in addition to open surgery. Retear rates (Sugaya types IV-V) were also influenced by FI of the supraspinatus (P = .001) but not of the infraspinatus (P = .979). Shoulders with supraspinatus FI at stages 0, 1, and 2 had retear rates of 10%, 22%, and 31%, respectively. Multivariable regression affirmed that the odds of retears are significantly increased by both stage 1 and stage 2 FI of the supraspinatus.

CONCLUSIONS

The Constant scores and retear rates were significantly associated with FI of the torn supraspinatus (stage ≥1) but not of the intact infraspinatus. The authors recommend that rapid surgical intervention be considered, before accumulation of fat, especially for young, active patients.

Ten-year clinical and anatomic follow-up after repair of anterosuperior rotator cuff tears: influence of the subscapularis

BACKGROUND

Anterosuperior rotator cuff tears are more frequent than expected. We report the results of a 10-year follow-up study after repair. Our hypothesis was that the extent of the subscapularis tear influenced the prognosis.

MATERIALS AND METHODS

The study population consisted of all 138 patients who underwent surgery in 14 participating centers in 2003 for full-thickness tears of the rotator cuff with lesions in the subscapularis and supraspinatus tendons. The patients were divided into 2 groups, depending on whether the subscapularis lesion affected only the superior half of the tendon (group A) or extended into the lower half (group B). Ninety-two patients (56 ± 7 years; 71 in group A and 21 in group B) were available for follow-up after 10 years (127 ± 16 months) with magnetic resonance imaging to evaluate tendon healing and muscle condition.

RESULTS

The mean Constant scores were 59 ± 16 before surgery and 77 ± 14 at follow-up (P = 1.7 × 10^-12). The retear rates were 25% for the supraspinatus and 13.5% for the subscapularis tendon. The clinical results for group A patients were better than those for group B. Severe fatty infiltration was observed more frequently in the subscapularis than in the supraspinatus muscle (27% vs. 12% of cases). Supraspinatus healing influenced subscapularis healing and fatty infiltration.

CONCLUSIONS

Repair of anterosuperior rotator cuff tears is satisfactory at 10 years, particularly if the subscapularis tear is not extensive. An extensive subscapularis tear is a negative prognosis factor. Postoperatively, fatty infiltration of the subscapularis muscle was frequently observed despite tendon healing.

Effect of glenohumeral elevation on subacromial supraspinatus compression risk during simulated reaching

Mechanical subacromial rotator cuff compression is one theoretical mechanism in the pathogenesis of rotator cuff disease. However, the relationship between shoulder kinematics and mechanical subacromial rotator cuff compression across the range of humeral elevation motion is not well understood. The purpose of this study was to investigate the effect of humeral elevation on subacromial compression risk of the supraspinatus during a simulated functional reaching task. Three-dimensional anatomical models were reconstructed from shoulder magnetic resonance images acquired from 20 subjects (10 asymptomatic, 10 symptomatic). Standardized glenohumeral kinematics from a simulated reaching task were imposed on the anatomic models and analyzed at 0, 30, 60, and 90° humerothoracic elevation. Five magnitudes of humeral retroversion were also imposed on the models at each angle of humerothoracic elevation to investigate the impact of retroversion on subacromial proximities. The minimum distance between the coracoacromial arch and supraspinatus tendon and footprint were quantified. When contact occurred, the magnitude of the intersecting volume between the supraspinatus tendon and coracoacromial arch was also quantified. The smallest minimum distance from the coracoacromial arch to the supraspinatus footprint occurred between 30 and 90°, while the smallest minimum distance to the supraspinatus tendon occurred between 0 and 60°. The magnitude of humeral retroversion did not significantly affect minimum distance to the supraspinatus tendon except at 60 or 90° humerothoracic elevation. The results of this study provide support for mechanical rotator cuff compression as a potential mechanism for the development of rotator cuff disease. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2329-2337, 2017.

Transtendon repair in partial articular supraspinatus tendon tear

INTRODUCTION

Partial thickness rotator cuff tears (PTRCTs) are common, with an incidence between 17% and 37%, and a high prevalence in throwing athletes. Different surgical procedures are suggested when partial tears involve the articular portion of the rotator cuff, including arthroscopic debridement of the tear, debridement with acromioplasty, tear completion and repair, and lately transtendon repair. This systematic review describes the transtendon repair and examines indications, contraindications, complications and clinical outcome.

SOURCE OF DATA

We identified clinical studies listed in the Pubmed Google Scholar, CINAHL, Cochrane Central and Embase Biomedical databases in English and Italian concerning the clinical outcomes following treatment of partial articular supraspinatus tendon tear using transtendon surgical repair.

AREAS OF AGREEMENT

Eighteen studies fulfilled our inclusion criteria. All were published between 2005 and 2016, three were retrospective, and 15 prospective. The total number of patients was 507 with a mean age of 50.8 years.

AREAS OF CONTROVERSY

Tear completion and repair and transtendon repair alone produce similar results.

GROWING POINTS

Transtendon surgical repair allows to obtain good-excellent results in the treatment of partial articular supraspinatus tendon tears.

AREAS TIMELY FOR DEVELOPING RESEARCH

Further studies are needed to produce clear guidelines in the treatment of partial articular supraspinatus tendon tears.

LEVEL OF EVIDENCE

IV.

Functions of the subregions of the supraspinatus muscle

The aim of this study was to investigate the functions of the six subregions of the supraspinatus muscle (SSP) determined by Kim et al. in Clin Anat 2007;20:648-655, using real-time tissue elastography (RTE). Twelve young male volunteers participated. The muscular hardness of the SSP was measured at rest and with contraction of the MMT3 in internal, neutral and external rotations. The SSP was functionally divided into five groups on the basis of the RTE results. These functional areas were roughly classified into three property groups: the anterior-superficial, anterior-middle, and anterior-deep subregions, which produce contractile force for abduction; the posterior-deep subregion, which produces contractile force for external rotation; and the posterior-superficial and posterior-middle subregions, which maintain tension. RTE was appropriate for measuring the functions of these muscular subregions. Clin. Anat. 30:347-351, 2017. © 2017 The Authors Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

Atelocollagen Enhances the Healing of Rotator Cuff Tendon in Rabbit Model

BACKGROUND

Failure of rotator cuff healing is a common complication despite the rapid development of surgical repair techniques for the torn rotator cuff.

PURPOSE

To verify the effect of atelocollagen on tendon-to-bone healing in the rabbit supraspinatus tendon compared with conventional cuff repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

A tear of the supraspinatus tendon was created and repaired in 46 New Zealand White rabbits. They were then randomly allocated into 2 groups (23 rabbits per group; 15 for histological and 8 for biomechanical test). In the experimental group, patch-type atelocollagen was implanted between bone and tendon during repair; in the control group, the torn tendon was repaired without atelocollagen. Each opposite shoulder served as a sham (tendon was exposed only). Histological evaluation was performed at 4, 8, and 12 weeks. Biomechanical tensile strength was tested 12 weeks after surgery.

RESULTS

Histological evaluation scores of the experimental group (4.0 ± 1.0) were significantly superior to those of the control group (7.7 ± 2.7) at 12 weeks ( P = .005). The load to failure was significantly higher in the experimental group (51.4 ± 3.9 N) than in the control group (36.4 ± 5.9 N) ( P = .001).

CONCLUSION

Histological and biomechanical studies demonstrated better results in the experimental group using atelocollagen in a rabbit model of the supraspinatus tendon tear.

CLINICAL RELEVANCE

Atelocollagen patch could be used in the cuff repair site to enhance healing.

P2 porous titanium implants improve tendon healing in an acute rat supraspinatus repair model

BACKGROUND

Current techniques in rotator cuff repair often lack structural integrity. P² porous titanium-coated constructs (DJO Surgical, Austin, TX, USA) promote osseointegration and soft tissue ingrowth. This study examined the ability of this material to improve the structural integrity of supraspinatus tendon repair in a rat model. We hypothesized that P² implants placed at the tendon-to-bone interface would improve mechanical and histologic measures of supraspinatus healing.

METHODS

Forty rats underwent supraspinatus repairs with P² implants in 1 shoulder and standard repair in the other. Rats were humanely killed at time 0 (n = 3), 2 weeks (n = 8), 4 weeks (n = 15), and 12 weeks (n = 14). Tendon-to-bone composite specimens were harvested and evaluated mechanically and histologically.

RESULTS

Tendon cross-sectional area was decreased in the P² implant group at 4 weeks, percentage of relaxation was increased at 2 weeks, elastic modulus was increased at 4 weeks, and maximum load and maximum stress were both increased at 2 and 4 weeks. Histologic analysis revealed no foreign body reactions within or around the P² implant, and healthy viable bone was visible within the P² implant.

CONCLUSION

The results support our hypothesis, specifically in early healing, in this randomized controlled animal study. These data support the use of P² porous titanium implants to improve tendon-to-bone healing.

Fibrosis, low vascularity, and fewer slow fibers after rotator-cuff injury

INTRODUCTION

Rotator-cuff injury (RCI) represents 50% of shoulder injuries, and prevalence increases with age. Even with successful tendon repair, muscle and joint function may not return.

METHODS

To explore the dysfunction, supraspinatus and ipsilateral deltoid (control) muscles were biopsied during arthroscopic RCI repair for pair-wise histological and protein-expression studies.

RESULTS

Supraspinatus showed fiber atrophy (P <  0.0001), fibrosis (by Sirius Red, P = 0.05), reduced vascular density (P <  0.001), and a lower proportion of slow fibers (P <  0.0001) compared with the ipsilateral control muscle. There were also higher levels of atrogin-1 (P = 0.05), vascular endothelial growth factor (VEGF, P <  0.01), and dystrophin (P <  0.008, relative to fiber diameter) versus control.

CONCLUSIONS

Adaptive changes in vascular endothelial growth factor and dystrophin were likely associated with reduced vascular supply, fatigue resistance, and fibrosis, accompanied by disuse atrophy from mechanical unloading of supraspinatus after tendon tear. Treatment to promote growth and vascularity in atrophic supraspinatus muscle may help improve functional outcome after surgical repair. Muscle Nerve 55: 715-726, 2017.

The validity and reliability of ultrasound on identifying supraspinatus tears during passive external rotation from 0° to 30°: a pilot project

BACKGROUND

Controversy exists regarding how much external rotation should be allowed following rotator cuff repair. Clinicians may use ultrasound imaging (USI) to visualize the supraspinatus (SSp) tendon during passive external rotation. However, the validity and reliability of USI used to assess supraspinatus tendon gap formation during external rotation needs to be established prior to using this technique in patient cohorts.

METHODS

Ten subjects with magnetic resonance imaging (MRI) confirmation of full-thickness SSp tears were matched to 10 control subjects. Images of the SSp were obtained at 0°, 10°, 20° and 30° of external rotation by a blinded tester on two occasions to establish both validity and reliability of the measure.

RESULTS

Validity was established as 70% agreement between the USI and MRI confirmed SSp tear group; reliability was established at greater than 0.90 at all positions of external rotation measured.

CONCLUSIONS

USI may be used to detect SSp tears with 70% validity, and the technique is reliable in all positions of external rotation.

Collagen V expression is crucial in regional development of the supraspinatus tendon

Manipulations in cell culture and mouse models have demonstrated that reduction of collagen V results in altered fibril structure and matrix assembly. A tissue-dependent role for collagen V in determining mechanical function was recently established, but its role in determining regional properties has not been addressed. The objective of this study was to define the role(s) of collagen V expression in establishing the site-specific properties of the supraspinatus tendon. The insertion and midsubstance of tendons from wild type, heterozygous and tendon/ligament-specific null mice were assessed for crimp morphology, fibril morphology, cell morphology, as well as total collagen and pyridinoline cross-link (PYD) content. Fibril morphology was altered at the midsubstance of both groups with larger, but fewer, fibrils and no change in cell morphology or collagen compared to the wild type controls. In contrast, a significant disruption of fibril assembly was observed at the insertion site of the null group with the presence of structurally aberrant fibrils. Alterations were also present in cell density and PYD content. Altogether, these results demonstrate that collagen V plays a crucial role in determining region-specific differences in mouse supraspinatus tendon structure. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2154-2161, 2016.

Effect of simvastatin on rat supraspinatus tendon mechanical and histological properties in a diet-induced hypercholesterolemia model

Hypercholesterolemia is a common condition and is a risk factor for tendon rupture, specifically in the supraspinatus tendon. In the clinic, statins are commonly prescribed to lower cholesterol, but little information is available examining the effect of statin treatment on the musculoskeletal system. Therefore, the objective of this study was to determine the biomechanical and histological effects of statin treatment in a diet-induced hypercholesterolemia model. We hypothesized that hypercholesterolemic rats treated with statins would have improved tendon biomechanical and histological properties compared to hypercholesterolemic rats not receiving daily statin treatment. Thirty adult male Sprague-Dawley rats ate either high-cholesterol (HC) diet (n = 20) or normal chow (CTL, n = 10). After 6 months, a subset of HC rats began daily oral simvastatin dosing (HC+S) at 20 mg/kg. All rats were sacrificed after a total of 9 months (3 months of statin treatment) and evaluated for histology and mechanics. For mechanics, at the insertion region, HC+S group had increased tendon cross-sectional area decreased and modulus. No differences were noted in mechanical properties at the midsubstance. For histology, no differences were noted in the insertion region. In the midsubstance region, HC+S group had more spindle shaped cells. Our results suggest that 3 months of simvastatin treatment in a diet-induced hypercholesterolemia rat model alters some tendon mechanical and histological properties, although a strong conclusion in support of improved parameters cannot be drawn. Therefore, we conclude that simvastatin treatment does not negatively affect tendon properties. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2009-2015, 2016.

Interobserver Agreement in the Classification of Partial-Thickness Rotator Cuff Tears Using the Snyder Classification System

BACKGROUND

At present, there is no widely accepted classification system for partial-thickness rotator cuff tears, and as a result, optimal treatment remains controversial.

PURPOSE

To examine the interobserver reliability and accuracy of classifying partial rotator cuff tears using the Snyder classification system. We hypothesized that the Snyder classification would be reproducible with high reliability and accuracy.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

Twenty-seven orthopaedic surgeons reviewed 10 video-recorded shoulder arthroscopies. Each surgeon was provided with a description of the Snyder classification system for partial-thickness rotator cuff tears and was then instructed to use this system to describe each tear. Interrater kappa statistics and percentage agreement between observers were calculated to measure the level of agreement. Surgeon experience as well as fellowship training was evaluated to determine possible correlations.

RESULTS

A kappa coefficient of 0.512 indicated moderate reliability between surgeons using the Snyder classification to describe partial-thickness rotator cuff tears. The mean correct score was 80%, which indicated "very good" agreement. There was no correlation between the number of shoulder arthroscopies performed per year and fellowship training and the number of correct scores.

CONCLUSION

The Snyder classification system is reproducible and can be used in future research studies in analyzing the treatment options of partial rotator cuff tears.

The Effect of a High Pitch Volume on Musculoskeletal Adaptations in High School Baseball Pitchers

BACKGROUND

Shoulder range of motion and strength adaptations occur at an early age in baseball pitchers.

PURPOSE/HYPOTHESIS

The purpose of this study was to examine the effect of pitch volume on in-season and year-to-year range of motion (ROM) and strength adaptations in high school baseball pitchers. The hypothesis was that a high pitch volume will not affect range of motion asymmetries but will impair supraspinatus strength.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Pre- and postseason ROM and strength measures were performed on pitchers from 3 high schools for 4 consecutive seasons, for a total of 95 player-seasons (mean ± SD participant age, 16 ± 1 years). Preseason measures were repeated the next year on players returning to the teams, for a total of 71 consecutive player-seasons. ROM tests included internal-external rotation and posterior shoulder flexibility. Strength tests (hand-held dynamometer) included internal-external rotation, supraspinatus, and scapular retraction. Pitchers were categorized by pitch count for the season (high, >400; moderate, 180-400; low, <180). ROM and strength changes in the dominant versus nondominant arm were assessed by analysis of variance.

RESULTS

Dominant versus nondominant ROM differences did not change from pre- to postseason (P = .36-.99) or from one year to the next (P = .46-.86), with no effect of pitch volume (P = .23-.87). Supraspinatus strength decreased in the dominant arm during the season, with 13% loss in high-volume pitchers (P < .001) and insignificant losses in moderate- (6%) and low-volume pitchers (2%). Strength in other tests was unaffected by pitch volume. Consistent with physical development, strength increased bilaterally from one year to the next (supraspinatus, 12%; external rotation, 15%; internal rotation, 14%; scapular retraction, 23%; P < .001). Supraspinatus strength gain in the dominant arm was affected by prior pitch volume (P = .02): 24% in low-volume pitchers (P < .01), with no significant change in moderate-volume (0%; P = .99) or high-volume (5%; P = .99) pitchers.

CONCLUSION

Dominant versus nondominant ROM differences did not progress during the season, or from one year to the next, and were unaffected by pitch volume. A high pitch volume was associated with in-season supraspinatus weakness and diminished strength gains from one year to the next. In conclusion, a high pitch volume appeared to have a catabolic effect on supraspinatus strength.

Collagen V-heterozygous and -null supraspinatus tendons exhibit altered dynamic mechanical behaviour at multiple hierarchical scales

Tendons function using a unique set of mechanical properties governed by the extracellular matrix and its ability to respond to varied multi-axial loads. Reduction of collagen V expression, such as in classic Ehlers-Danlos syndrome, results in altered fibril morphology and altered macroscale mechanical function in both clinical and animal studies, yet the mechanism by which changes at the fibril level lead to macroscale functional changes has not yet been investigated. This study addresses this by defining the multiscale mechanical response of wild-type, collagen V-heterozygous and -null supraspinatus tendons. Tendons were subjected to mechanical testing and analysed for macroscale properties, as well as microscale (fibre re-alignment) and nanoscale (fibril deformation and sliding) responses. In many macroscale parameters, results showed a dose-dependent response with severely decreased properties in the null group. In addition, both heterozygous and null groups responded to load faster than in wild-type tendons via earlier fibre re-alignment and fibril stretch. However, the heterozygous group exhibited increased fibril sliding, while the null group exhibited no fibril sliding. These studies demonstrate that dynamic responses play an important role in determining overall function and that collagen V is a critical regulator in the development of these relationships.

The champagne toast position isolates the supraspinatus better than the Jobe test: an electromyographic study of shoulder physical examination tests

BACKGROUND

While Jobe's test is widely used, it does not isolate supraspinatus activity. Our purpose was to examine the electromyographic (EMG) activity within the supraspinatus and deltoid with resisted abduction to determine the shoulder position that best isolates the activity of the supraspinatus.

METHODS

We performed EMG analysis of the supraspinatus, anterior head of the deltoid, and middle head of the deltoid in 10 normal volunteers. We measured EMG activity during resisted shoulder abduction in the scapular plane to both manual resistance and a standardized load in varying degrees of abduction and rotation. To determine which position best isolates supraspinatus activity, the ratio of supraspinatus to deltoid activity (S:D) was calculated for each position. Results were analyzed with a repeated-measures analysis of variance with Bonferroni correction. The posterior deltoid was excluded as it serves mostly to extend and externally rotate.

RESULTS

Our study confirmed Jobe's findings of maximal supraspinatus activity at 90° of abduction. However, decreasing abduction significantly increased S:D for both resisted manual testing and testing against a standardized load (P = .002 and .001, respectively). The greatest S:D ratio (4.6 ± 3.4 for standardized load testing) was seen at the "champagne toast" position, i.e., 30° of abduction, mild external rotation, 30° of flexion, and 90° of elbow flexion. The smallest ratio (0.8 ± 0.6) was seen at Jobe's position.

CONCLUSIONS

Testing of abduction strength in the champagne toast position, i.e., 30° of abduction, mild external rotation, and 30° of flexion, better isolates the activity of the supraspinatus from the deltoid than Jobe's "empty can" position.

Arthroscopic rotator cuff repair in the weight-bearing shoulder

BACKGROUND

In wheelchair-dependent individuals, pain often develops because of rotator cuff tendon failure and/or osteoarthritis of the glenohumeral joint. The purposes of this study were to investigate (1) specific rotator cuff tear patterns, (2) structural healing, and (3) clinical outcomes after arthroscopic rotator cuff repair in a cohort of wheelchair-dependent patients.

METHODS

Forty-six shoulders with a mean follow-up of 46 months (range, 24-82 months; SD, 13 months) from a consecutive series of 61 shoulders in 56 patients (46 men and 10 women) undergoing arthroscopic rotator cuff repair were available for analysis. Clinical outcome analysis was performed using the Constant-Murley score, the Subjective Shoulder Value, and the American Shoulder and Elbow Surgeons score. The integrity of the repair was analyzed by ultrasound.

RESULTS

Of the shoulders, 87% had supraspinatus involvement, 70% had subscapularis involvement, and 57% had an anterosuperior lesion involving both the supraspinatus and subscapularis. Despite an overall structural failure rate of 33%, the patients showed improvements in the Constant-Murley score from 50 points (range, 22-86 points; SD, 16 points) preoperatively to 80 points (range, 40-98 points; SD, 12 points) postoperatively and in the American Shoulder and Elbow Surgeons score from 56 points (range, 20-92 points; SD, 20 points) preoperatively to 92 points (range, 53-100 points; SD, 10 points) postoperatively, with a mean postoperative Subjective Shoulder Value of 84% (range, 25%-100%; SD, 17%).

CONCLUSION

Failure of the rotator cuff in weight-bearing shoulders occurs primarily anterosuperiorly. Arthroscopic rotator cuff repair leads to a structural failure rate of 33% but satisfactory functional results with high patient satisfaction at midterm follow-up.

Microvascular blood flow in normal and pathologic rotator cuffs

BACKGROUND

Microvascular blood flow in the tendon plays an important role in the pathogenesis of rotator cuff abnormalities. There are conflicting views about the presence of a hypovascular zone in the supraspinatus tendon. Besides, no studies have looked at the pattern of blood flow around a partial-thickness tear. Our aim was to measure microvascular blood flow in normal and a range of pathologic rotator cuff tendons using laser doppler flowmetry.

METHODS

A total of 120 patients having arthroscopic shoulder surgery were divided into 4 equal groups on the basis of their intraoperative diagnosis: normal rotator cuff, subacromial impingement syndrome, and partial-thickness or full-thickness rotator cuff tear. Microvascular blood flow was measured at 5 different regions of each cuff using a laser doppler probe. The values were compared to assess variability within and between individuals.

RESULTS

Total blood flow was greater in the normal rotator cuff group compared with the groups with pathologic rotator cuffs, with the largest difference seen in the subacromial impingement group. Within individuals, blood flow was highest at the musculotendinous junction and lowest at the lateral insertional part of the tendon. Among groups, the blood flow was significantly lower at the anteromedial and posteromedial cuff in the groups with impingement and full-thickness tears compared with the group with normal cuff.

CONCLUSION

Real-time in vivo laser doppler analysis has shown that microvascular blood flow is not uniform throughout the supraspinatus tendon. Blood flow in the pathologic supraspinatus tendon was significantly lower compared with the normal tendon.

Florid Suprascapular Neuropathy after Primary Rotator Cuff Repair Attributed to Suprascapular Notch Constriction in the Setting of Double Crush Syndrome

This report describes a patient who had an open repair of a small supraspinatus tendon tear performed 6 months after an arthroscopic acromioplasty with debridement had failed to provide pain relief. Three months prior to the tendon repair, he had a two-level cervical spine discectomy and fusion (C4-5, C5-6) that improved his neck pain. Florid suprascapular neuropathy was detected 10 weeks after the open rotator cuff repair. Evidence of some nerve recovery resulted in a long period of observation. But unsatisfactory improvement warranted decompression of the suprascapular notch, which was found to be very stenotic. At surgery, there was no evidence of neuroma, cyst, or other compressing lesion or tissue. Therefore, it was ultimately hypothesized that there was an exacerbation of a preexisting, but clinically unrecognized, entrapment of the suprascapular nerve in the suprascapular notch in the setting of cervical radiculopathy (primarily C5). Retrospectively it was also concluded that had this compressive etiology been recognized, it would have favored prompt decompression rather than the long observation period. Three years was required to achieve a good result following suprascapular notch decompression. The underlying C5 radiculopathy may have created a "double crush syndrome" that contributed to the propensity for injury and the prolonged recovery. There should be heightened awareness of this problem in patients who do not have satisfactory improvement in shoulder pain from previous shoulder and neck surgery.

Rotator Cuff Tendinopathy: Navigating the Diagnosis-Management Conundrum

Synopsis The hallmark characteristics of rotator cuff (RC) tendinopathy are pain and weakness, experienced most commonly during shoulder external rotation and elevation. Assessment is complicated by nonspecific clinical tests and the poor correlation between structural failure and symptoms. As such, diagnosis is best reached by exclusion of other potential sources of symptoms. Symptomatic incidence and prevalence data currently cannot be determined with confidence, primarily as a consequence of a lack of diagnostic accuracy, as well as the uncertainty as to the location of symptoms. People with symptoms of RC tendinopathy should derive considerable comfort from research that consistently demonstrates improvement in symptoms with a well-structured and graduated exercise program. This improvement is equivalent to outcomes reported in surgical trials, with the additional generalized benefits of exercise, less sick leave, a faster return to work, and reduced costs to the health care system. This evidence covers the spectrum of conditions that include symptomatic RC tendinopathy and atraumatic partial- and full-thickness RC tears. The principles guiding exercise treatment for RC tendinopathy include relative rest, modification of painful activities, an exercise strategy that initially does not exacerbate pain, controlled reloading, and gradual progression from simple to complex shoulder movements. Evidence also exists for a specific exercise program being beneficial for people with massive inoperable tears of the RC. Education is an essential component of rehabilitation, and attention to lifestyle factors (smoking cessation, nutrition, stress, and sleep management) may enhance outcomes. Outcomes may also be enhanced by subgrouping RC tendinopathy presentations and directing treatment strategies according to the clinical presentation and the patient's response to shoulder symptom modification procedures outlined herein. There are substantial deficits in our knowledge regarding RC tendinopathy that need to be addressed to further improve clinical outcomes. J Orthop Sports Phys Ther 2015;45(11):923-937. Epub 21 Sep 2015. doi:10.2519/jospt.2015.5941.

Scleraxis is required for the development of a functional tendon enthesis

The attachment of dissimilar materials is a major engineering challenge, yet this challenge is seemingly overcome in biology. This study aimed to determine how the transcription factor Scleraxis (Scx) influences the development and maturation of the tendon-to-bone attachment (enthesis). Mice with conditional knockout (cKO) for Scx (Scx(flx/-), Prx1Cre(+)) and wild-type [(WT) Scx(flx/+) or Scx(flx/flx)] littermates were killed at postnatal days 7-56 (P7-P56). Enthesis morphometry, histology, and collagen alignment were investigated throughout postnatal growth. Enthesis tensile mechanical properties were also assessed. Laser microdissection of distinct musculoskeletal tissues was performed at P7 for WT, cKO, and muscle-unloaded (botulinum toxin A treated) attachments for quantitative PCR. cKO mice were smaller, with altered bone shape and impaired enthesis morphology, morphometry, and organization. Structural alterations led to altered mechanical properties; cKO entheses demonstrated reduced strength and stiffness. In P7 attachments, cKO mice had reduced expression of transforming growth factor (TGF) superfamily genes in fibrocartilage compared with WT mice. In conclusion, deletion of Scx led to impairments in enthesis structure, which translated into impaired functional (i.e., mechanical) outcomes. These changes may be driven by transient signaling cues from mechanical loading and growth factors.

Atrophy, inducible satellite cell activation, and possible denervation of supraspinatus muscle in injured human rotator-cuff muscle

The high frequency of poor outcome and chronic pain after surgical repair of shoulder rotator-cuff injury (RCI) prompted this study to explore the potential to amplify muscle regeneration using nitric oxide (NO)-based treatment. After preoperative magnetic resonance imaging (MRI), biopsies of supraspinatus and ipsilateral deltoid (as a control) were collected during reparative surgery for RCI. Muscle fiber diameter, the pattern of neuromuscular junctions observed with alpha-bungarotoxin staining, and the γ:ε subunit ratio of acetylcholine receptors in Western blots were examined in tandem with experiments to determine the in vitro responsiveness of muscle satellite cells to activation (indicated by uptake of bromodeoxyuridine, BrdU) by the NO-donor drug, isosorbide dinitrate (ISDN). Consistent with MRI findings of supraspinatus atrophy (reduced occupation ratio and tangent sign), fiber diameter was lower in supraspinatus than in deltoid. ISDN induced a significant increase over baseline (up to 1.8-fold), in the proportion of BrdU+ (activated) Pax7+ satellite cells in supraspinatus, but not in deltoid, after 40 h in culture. The novel application of denervation indices revealed a trend for supraspinatus muscle to have a higher γ:ε subunit ratio than deltoid (P = 0.13); this ratio inversely with both occupancy ratio (P < 0.05) and the proportion of clusters at neuromuscular junctions (P = 0.05). Results implicate possible supraspinatus denervation in RCI and suggest NO-donor treatment has potential to promote growth in atrophic supraspinatus muscle after RCI and improve functional outcome.

A new tear pattern of the rotator cuff and its treatment: Fosbury flop tears

Purpose:

The purpose of this report is to describe a new full-thickness tear pattern of the posterosuperior rotator cuff with reversal healing. We describe the specific radiologic signs associated with this tear pattern and the arthroscopic rotator cuff repair technique.

Materials and Methods:

A prospective radiologic and clinical study collected all patients with a magnetic resonance imaging arthrogram that underwent an arthroscopic rotator cuff repair over a 1 year period.

Results:

Among 97 patients, five demonstrated a tear of the posterosuperior rotator cuff with reversal healing. Characteristic radiographic findings included a thicker tendon than normal, the presence of a stump and accumulation of liquid in the superior-medial part of the subacromial bursa, and adhesions between the supraspinatus tendon and the wall of the subacromial bursa.

Conclusion:

Avulsion of the posterosuperior rotator cuff with reversal healing on its bursal-side is a less common condition. This type of lesion and distinct radiographic signs that can be recognized to facilitate anatomic repair of the rotator cuff.

Level of evidence:

Level IV.

Suture placement near the musculotendinous junction in the supraspinatus: implications for rotator cuff repair

BACKGROUND

Transosseous-equivalent rotator cuff repair has an increased incidence of medial rotator cuff failure compared with single-row repair. No studies have evaluated the influence of the proximity of the suture row to the musculotendinous junction (MTJ) on cyclic gapping and failure properties.

HYPOTHESIS

A single row of horizontal mattress sutures placed within the supraspinatus tendon lateral to the MTJ will experience less gap formation and higher failure loads than a similar suture row placed at the MTJ.

STUDY DESIGN

Controlled laboratory study.

METHODS

Paired supraspinatus tendons were isolated from human cadaveric specimens and resected at the tendon insertion to the humerus. Randomized within a pair, a single row of 4 horizontal mattress sutures was placed either in the tendon 5 mm lateral to the MTJ or at the MTJ. The tied sutures secured the tendon to a fixture that ensured consistent placement of the suture row in the tendon and static fixation of the row. The muscle belly was gripped in a cryoclamp, and a servohydraulic materials testing machine was used to provide uniaxial tensile deformation for 500 cycles at 1 Hz, followed by load to failure at 1 mm/s. Fiducial markers with video tracking were used to quantify gap formation at the suture line, while the materials testing machine recorded loading for the cyclic and failure tests.

RESULTS

During cyclic loading, both constructs experienced gross initial gap formation, followed by progressive gap formation that plateaued after cycle 200. The MTJ specimens had significantly higher mean cumulative gapping than the tendon specimens: 3.6±1.0 mm versus 2.4±0.6 mm, respectively (P=.012). The tendon specimens had significantly higher mean loads to failure than did the MTJ specimens: 567.1±121.8 N versus 434.2±148.1 N, respectively (P=.013). The mean failure displacement did not differ between groups for the tendon and MTJ: 5.7±2.5 mm versus 4.5±2.0 mm, respectively (P=.144).

CONCLUSION

A horizontal suture row placed at the MTJ has inferior mechanical properties (increased gapping, decreased load support) as compared with a suture row placed 5 mm laterally within the tendon.

CLINICAL RELEVANCE

The integrity of rotator cuff repair may be compromised if sutures are placed too close to the MTJ.

Feasibility assessment of shear wave elastography to rotator cuff muscle

Pre-surgical measurement of supraspinatus muscle extensibility is important for rotator cuff repair. The purpose of the present study was to explore the potential feasibility of a shear wave ultrasound elastography (SWE)-based method, combined with B-mode ultrasound, to measure the in vivo stiffness of the supraspinatus muscle non-invasively and thus obtain key information about supraspinatus muscle extensibility. Our investigation comprised two steps. First, we determined the orientation of the supraspinatus muscle fibers in cadaveric shoulders without rotator cuff tear in order to optimize the ultrasound probe positions for SWE imaging. Second, we investigated the feasibility of quantifying the stiffness of the normal supraspinatus muscle by SWE in vivo. The supraspinatus muscle was divided into four anatomical regions: anterior superficial (AS), posterior superficial (PS), anterior deep (AD), and posterior deep (PD). Each region was examined by SWE. The SWE stiffnesses of AD, AS, PD, and PS were 40.0 ± 12.4, 34.0 ± 9.9, 32.7 ± 12.7, 39.1 ± 15.7 kPa, respectively. SWE combined with B-Mode ultrasound imaging could be a feasible method for quantifying the local stiffness of the rotator cuff muscles.