Tendon retracts more than muscle in experimental chronic tears of the rotator cuff

Traumatic and Atraumatic Rotator Cuff Tears Have the Same Rates of Healing

Background

To examine whether traumatic rotator cuff repairs (RCRs) differ in postoperative rotator cuff tendon integrity and functional outcomes from degenerative RCRs.

Methods

RCRs performed by a single surgeon were retrospectively identified. The inclusion criteria were repairable Goutallier grades 0 to 2 full-thickness rotator cuff tears. Demographic and clinical data as well as radiological results were compared. A multivariate logistic regression of the of patient acceptable symptom state for American Shoulder and Elbow Surgeons (ASES) score was performed to evaluate whether the origin of tear led to a different relative risk (RR) independently from tear and surgical characteristics.

Results

A total of 616 consecutive shoulders (304 traumatic and 312 degenerative) were finally included. Traumatic ruptures presented a greater distribution of male (72% vs 51%, P < .001) and younger patients (53 vs 57 years, P < .001), as well as earlier onset of symptoms (3 vs 15 months, P < .001), reduced range of motion in preoperative assessment for forward elevation (130° vs 150°, P < .001), and slightly greater preoperative ASES (46.5 ± 19.7 vs 50.0 ± 18.0, P = .022) and Constant (47.0 ± 20.2 vs 52.0 ± 18.9, P = .001) scores. Degenerative tears presented a lower proportion of grade 3 tendon coronal retraction (11% vs 18%, P = .031). Postoperative tendon integrity at 6 months was comparable for both groups, predominantly Sugaya types 1 and 2 (91% traumatic; 92% degenerative, P = .371). Both groups exhibited favorable outcomes in range of motion and postoperative functional scores at last follow-up. The multivariate regression confirmed that the tear origin was not significantly associated with patient acceptable symptom state achievement (P = .201) but rather with greater preoperative ASES score (RR, 1.01), men (RR, 1.16) and workers' compensation (RR, 0.65) (P < .05).

Conclusions

Traumatic cases were frequent, involved younger patients, more frequently affected the anterior rotator cuff, and were associated with more severe tendon retraction. Traumatic and degenerative RCRs lead to comparable clinical and radiologic results.

Level of Evidence

Level III, retrospective comparative study.

Structural Musculotendinous Parameters That Predict Failed Tendon Healing After Rotator Cuff Repair

Background

Healing of the rotator cuff after repair constitutes a major clinical challenge with reported high failure rates. Identifying structural musculotendinous predictors for failed rotator cuff repair could enable improved diagnosis and management of patients with rotator cuff disease.

Purpose

To investigate structural predictors of the musculotendinous unit for failed tendon healing after rotator cuff repair.

Study Design

Cohort study; Level of evidence, 2.

Methods

Included were 116 shoulders of 115 consecutive patients with supraspinatus (SSP) tear documented on magnetic resonance imaging (MRI) who were treated with an arthroscopic rotator cuff repair. Preoperative assessment included standardized clinical and imaging (MRI) examinations. Intraoperatively, biopsies of the joint capsule, the SSP tendon, and muscle were harvested for histological assessment. At 3 and 12 months postoperatively, patients were re-examined clinically and with MRI. Structural and clinical predictors of healing were evaluated using logistic and linear regression models.

Results

Structural failure of tendon repair, which was significantly associated with poorer clinical outcome, was associated with older age (β = 1.12; 95% CI, 1.03 to 1.26; P = .03), shorter SSP tendon length (β = 0.89; 95% CI, 0.8 to 0.98; P = .02), and increased proportion of slow myosin heavy chain (MHC)-I/fast MHC-II hybrid muscle fibers (β = 1.23; 95% CI, 1.07 to 1.42; P = .004). Primary clinical outcome (12-month postoperative Constant score) was significantly less favorable for shoulders with fatty infiltration of the infraspinatus muscle (β = -4.71; 95% CI, -9.30 to -0.12; P = .044). Conversely, a high content of fast MHC-II muscle fibers (β = 0.24; 95% CI, 0.026 to 0.44; P = .028) was associated with better clinical outcome.

Conclusion

Both decreased tendon length and increased hybrid muscle fiber type were independent predictors for retear. Clinical outcome was compromised by tendon retearing and increased fatty infiltration of the infraspinatus muscle. A high content of fast MHC-II SSP muscle fibers was associated with a better clinical outcome.

Registration

NCT02123784 (ClinicalTrials.govidentifier).

Clinical outcomes and tendon lengthening after arthroscopic rotator cuff repair

BACKGROUND

There is a phenomenon in which the tendon appears to increase the length after rotator cuff repair. However, it is unclear in which cases tendon lengthening occurs and how the degree of lengthening affects the surgical outcome. This study aimed to evaluate preoperative and postoperative musculotendinous junction (MTJ) and tendon length on magnetic resonance imaging and assess the postoperative tendon lengthening and its impact on postoperative outcomes.

METHODS

We reviewed 109 patients with good repair integrity after arthroscopic rotator cuff repair. Patients whose supraspinatus tendons were simply pulled out laterally without any additional procedures were included. They underwent serial magnetic resonance imaging before surgery and at 3, 6, and 24 months after surgery. The location of the MTJ in relation to the line of the glenoid fossa and the supraspinatus tendon length were measured. Clinical evaluation was conducted 2 years after surgery, including the range of shoulder motion, shoulder strength index (affected/unaffected strength), Constant score, University of California, Los Angeles score, and pain numeric rating scale. The characteristics of the preoperative tendon, change in tendon length over time, amount of the lateral shift of MTJ location and tendon length, and impact of tendon lengthening on postoperative clinical outcomes were analyzed.

RESULTS

The preoperative tendon retraction significantly correlated with the MTJ location (r = -0.75; P < .0001) and preoperative tendon length (r = -0.46; P < .0001). The tendon length at 3, 6, and 24 months after surgery was significantly longer than those before surgery (26.7 ± 5.8 mm, 27.9 ± 6.6 mm, 28.5 ± 5.6 mm, and 21.5 ± 5.1 mm, respectively). From before surgery to 24 months after surgery, the MTJ location moved 8.4 ± 8.6 mm laterally and the tendon length increased 7.0 ± 6.1 mm. A significant and weak negative correlation was found between tendon lengthening and the abduction strength index (r = -0.22; P = .03); however, no significant correlation with pain, range of shoulder motion, external rotation strength index, Constant score, and University of California, Los Angeles score was found. Multiple linear regression analysis also showed that tendon lengthening was only associated with the abduction strength index (standardized coefficient = -0.20, P = .03).

CONCLUSIONS

Tendon lengthening and lateral shift of MTJ location were observed after arthroscopic rotator cuff repair, and they correlated with preoperative tendon retraction. Although the amount of tendon lengthening had negative weak correlation with abduction strength index, it did not affect other postoperative outcomes.

Mesenchymal Stem Cell Delivery via Topographically Tenoinductive Collagen Biotextile Enhances Regeneration of Segmental Tendon Defects

BACKGROUND

Successful management of massive rotator cuff (RC) tendon tears represents a treatment challenge because of the limited intrinsic healing capacity of native tendons and the risk of repair failure. Biologic augmentation of massive RC tears utilizing scaffolds-capable of regenerating bulk tendon tissue to achieve a mechanically functional repair-represents an area of increasing clinical interest.

PURPOSE

To investigate the histological and biomechanical outcomes after the use of a novel biologic scaffold fabricated from woven electrochemically aligned collagen (ELAC) threads as a suture-holding, fully load-bearing, defect-bridging scaffold with or without mesenchymal stem cells (MSCs) compared with direct repair in the treatment of critically sized RC defects using a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 34 New Zealand White rabbits underwent iatrogenic creation of a critically sized defect (6 mm) in the infraspinatus tendon of 1 shoulder, with the contralateral shoulder utilized as an intact control. Specimens were divided into 4 groups: (1) gap-negative control without repair; (2) direct repair of the infraspinatus tendon-operative control; (3) tendon repair using ELAC; and (4) tendon repair using ELAC + MSCs. Repair outcomes were assessed at 6 months using micro-computed tomography, biomechanical testing, histology, and immunohistochemistry.

RESULTS

Specimens treated with ELAC demonstrated significantly less tendon retraction when compared with the direct repair group specimens (P = .014). ELAC + MSCs possessed comparable biomechanical strength (178 ± 50 N) to intact control shoulders (199 ± 35 N) (P = .554). Histological analyses demonstrated abundant, well-aligned de novo collagen around ELAC threads in both the ELAC and the ELAC + MSC shoulders, with ELAC + MSC specimens demonstrating increased ELAC resorption (7% vs 37%, respectively; P = .002). The presence of extracellular matrix components, collagen type I, and tenomodulin, indicating tendon-like tissue formation, was appreciated in both the ELAC and the ELAC + MSC groups.

CONCLUSION

The application of MSCs to ELAC scaffolds improved biomechanical and histological outcomes when compared with direct repair for the treatment of critically sized defects of the RC in a rabbit model.

CLINICAL RELEVANCE

This study demonstrates the feasibility of repairing segmental tendon defects with a load-bearing, collagen biotextile in an animal model, showing the potential applicability of RC repair supplementation using allogeneic stem cells.

Utility of Preoperative Shear-Wave Elastography of the Supraspinatus Muscle for Predicting Successful Rotator Cuff Repair: A Prospective Observational Study With MRI Correlation

BACKGROUND. After rotator cuff tear, properties of the torn muscle predict failed surgical repair. OBJECTIVE. The purpose of our study was to explore the utility of preoperative shear-wave elastography (SWE) measurements of the supraspinatus muscle to predict successful rotator cuff repair, including comparison with MRI-based measures. METHODS. This prospective study included 74 patients (37 men, 37 women; mean age, 63.9 ± 10.0 [SD] years) who underwent rotator cuff repair between May 2019 and January 2021. Patients underwent preoperative clinical shoulder MRI and investigational shoulder ultrasound including SWE using shear modulus. The mean elasticity values of the supraspinatus and trapezius muscles were measured, and the elasticity ratio (i.e., ratio of mean elasticity of supraspinatus muscle to mean elasticity of trapezius muscle) was calculated. The muscular fatty infiltration score (1-3 scale) was recorded on gray-scale ultrasound. On MRI, muscular fatty infiltration was assessed by Goutallier grade (0-4 scale), and muscular atrophy was assessed by the occupation ratio (ratio of cross-sectional areas of supraspinatus muscle and supraspinatus fossa) and by the muscle atrophy grade (0-3 scale). After rotator cuff repair, the surgeon classified procedures as achieving sufficient (n = 60) or insufficient (n = 14) repair. RESULTS. Patients with insufficient repair, versus those with sufficient repair, more commonly exhibited a large (3-5 cm) tear (100.0% vs 50.0%). Patients with insufficient, versus sufficient, repair exhibited higher mean Goutallier grade (3.8 ± 0.4 vs 1.9 ± 1.1), mean muscle atrophy grade (2.0 ± 0.8 vs 0.5 ± 0.7), mean supraspinatus elasticity (44.15 ± 8.06 vs 30.84 ± 7.89 kPa), mean elasticity ratio (3.66 ± 0.66 vs 1.83 ± 0.58), and mean gray-scale fatty infiltration grade (2.86 ± 0.36 vs 1.63 ± 0.66) and showed lower mean occupation ratio (0.3 ± 0.1 vs 0.6 ± 0.1) (all, p < .001). AUC for predicting insufficient repair was 0.945 for Goutallier grade, 0.961 for occupation ratio, 0.900 for muscle atrophy grade, 0.874 for mean elasticity, 0.971 for elasticity ratio, and 0.912 for gray-scale fatty infiltration grade. Elasticity ratio (cutoff ≥ 2.51) achieved sensitivity of 100.0% and specificity of 90.0% for insufficient repair. At multivariable analysis including tear size, the three MRI measures, elasticity ratio, and gray-scale fatty infiltration grade, the only independent predictors of insufficient repair were muscle atrophy grade of 2-3 (odds ratio [OR] = 9.3) and elasticity ratio (OR = 15.7). CONCLUSION. SWE-derived elasticity is higher in patients with insufficient rotator cuff repair; the elasticity ratio predicts insufficient repair independent of tear size and muscle characteristics. CLINICAL IMPACT. Preoperative SWE may serve as a prognostic marker in patients with rotator cuff tear.

The Regenerative Role of Gelatin in PLLA Electrospun Membranes for the Treatment of Chronic Massive Rotator Cuff Injuries

Failing to regenerate native tendon tissue in chronic massive rotator cuff tears (CMRCTs) results in high retear rates after surgery. Gelatin is a hydrolyzed form of collagen which is bioactive and biocompatible. This study intends to investigate the suitability of integrating gelatin to poly (l-lactic acid) (PLLA) fibrous membranes for promoting the healing of CMRCTs. PLLA/Gelatin electrospun membranes (PGEM) are fabricated using electrospinning technology. The fourier transform infrared, static contact angles are tested sequentially. Cytocompatibility is evaluated with rat tendon fibroblasts and human umbilical endothelial cells (HUEVCs) lines. CMRCTs rat models are established and assigned into three groups (the sham group, the repaired group, and the augmentation group) to perform histomorphological and biomechanical evaluations. Gelatin is successfully integrated into PLLA fibrous membranes by the electrospinning technique. In vitro studies indicate that PGEM shows a great cytocompatibility for rat tendon fibroblasts and HUEVCs. In vivo studies find that applications of PGEM significantly promote well-aligned collagen I fibers formation and enhance biomechanical properties of the repaired tendon in CMRCTs rat models. In summary, gelatin promotes tendon fibroblasts and HUEVCs adhesion, migration, and proliferation on the PLLA fibrous membranes, and PGEM may provide a great prospect for clinical application.

Anteroposterior tear size, age, hospital, and case number are important predictors of repair integrity: an analysis of 1962 consecutive arthroscopic single-row rotator cuff repairs

BACKGROUND

Retear or nonhealing of a surgically repaired rotator cuff is common, but the determinants of retear are poorly understood. We aimed to determine the relationship between preoperative and intraoperative factors and retear rate following rotator cuff repair and to formulate a predictive model based on this relationship, including any interaction effects between tear size, patient age, and surgical experience in contributing to the retear rate.

METHODS

We performed a post hoc analysis of prospectively collected data from 1962 consecutive patients who underwent a primary arthroscopic single-row rotator cuff repair performed by the senior author from 2007 through 2018 and postoperatively returned for 6-month follow-up ultrasonography.

RESULTS

Multiple logistic regression analysis revealed anteroposterior tear length to be the most important independent predictor of retear (Wald statistic, 90; P < .001). Other independent predictors included case number (Wald statistic, 59; P < .001), patient age at surgery (Wald statistic, 30; P < .001), and type of hospital (public vs. private) (Wald statistic, 17; P < .001). The data indicated that following rotator cuff repair, there was a 4-fold increase in the retear rate as the anteroposterior tear size increased from 1 cm to 3 cm; a 8-fold decrease when comparing case number 1000 with case number 3000; a 2-fold increase as patient age increased from 50 years to 70 years; and a 3-fold increase when comparing surgery performed in a public hospital vs. a private hospital. The area under the receiver operating characteristic curve was 0.81 (95% confidence interval, 0.78-0.84), indicating that our equation could predict 81% of retears.

CONCLUSIONS

Anteroposterior tear length was the most important independent predictor of retear or nonhealing. Other predictive factors included case number, patient age at surgery, and hospital type. The predictive effect of anteroposterior tear length, patient age, and case number in contributing to retear was additive. Our regression equation may be used to calculate patient rotator cuff retear risk at 6 months after repair.

Stiffness change of the supraspinatus muscle can be detected by magnetic resonance elastography

Magnetic resonance elastography (MRE) and ultrasound shear wave elastography (SWE) are imaging techniques to measure stiffness of the soft tissue using magnetic resonance imaging (MRI) and ultrasound images, respectively. The purpose of this study was to explore the feasibility of the MRE measurement to evaluate the change in supraspinatus (SSP) muscle stiffness before and after rotator cuff tear, and to compare the result with those of SWE. Six swine shoulders were used. The skin and subcutaneous fat were removed, and the stiffness value of the SSP muscle was measured by MRE and SWE. The MRE measurement was performed with 0.3 T open MRI and the vibration from a pneumatic driver system with active driver to a passive driver to create the shear wave in the tissue. The passive driver was placed on the center of the SSP muscle. The stiffness was estimated from the wave images using local frequency estimation methods. In the SWE measurement, the probe of the ultrasound was placed on the center of the SSP muscle. The shear wave propagation speed was measured at a depth of 1 cm from the surface, and the stiffness was calculated. After those measurements, the rotator cuff tendon was detached from the greater tuberosity, and MRE and SWE measurements were then performed in the same manner again. The differences in the stiffness values were compared between before and after the rotator cuff tendon tear on both the MRE and SWE measurements. The results indicated that stiffness values on MRE and SWE were 9.3 ± 1.8 and 10.0 ± 1.2 kPa respectively before the rotator cuff tear, and 7.3 ± 1.3 and 8.0 ± 0.8 kPa respectively after the tendon detachment. Stiffness values were significantly lower after the tendon detachment on both the MRE and SWE measurements (p < 0.05). Our results demonstrated that stiffness values of the SSP muscle on MRE and SWE were lower after rotator cuff detachment. From this result, MRE may be a feasible method for quantification of the change in rotator cuff muscle stiffness.

Consider Long Head of Biceps Tendon for Reconstruction of Massive, Irreparable Rotator Cuff Tear

Despite the different treatment options for irreparable and massive rotator cuff tears (RCTs), there is no optimal treatment. Thirty percent of total RCTs can be classified as irreparable because of the massive tear size and severe muscle atrophy. The reported treatment failure rate is approximately 40% for massive RCTs. RCTs may be treated conservatively or surgically depending on pain, disability, and functional demands. The surgical treatment options are many, but decision making is a challenge; the real challenge is to apply the correct procedure for the correct indication in each patient. The long head of the biceps tendon (LHBT) was used for augmentation to bridge the gap in immobile, massive RCTs. An arthroscopic biceps-incorporating technique was used for repair of large and massive RCTs, avoiding undue tension on the rotator cuff (RC). Recently, the LHBT was used for superior capsular reconstruction. This article describes the use of the LHBT for reconstruction of massive and irreparable RCTs through the following steps: (1) open exposure of the RCT, (2) debridement and subacromial decompression, (3) biceps tenotomy at the LHBT's origin on the glenoid, (4) LHBT and RC cuff mobilization, (5) passage of the LHBT through the mobilized RC and reflection onto itself, (6) tuberoplasty, and (7) fixation of the RC complex at the RC footprint.

Treatment of non-arthritic pseudoparetic shoulders with irreparable massive rotator cuff tears: arthroscopic procedures yield comparable midterm results to reverse arthroplasty

Background

Irreparable massive rotator cuff tears (IMRCTs) are a well-known cause for functional limitation and difficult to treat. Although several joint-preserving as well as joint-replacing procedures were found to provide pain relief and gain of function, midterm results are scarce, particularly in pseudoparetic shoulder joints unaccompanied by severe osteoarthritis. The purpose of this study was to compare the midterm functional outcomes of arthroscopic procedures to those of reverse total shoulder arthroplasty (RTSA) in pseudoparetic shoulders with IMRCTs unaccompanied by severe osteoarthritis.

Methods

All patients who underwent either joint-preserving (group A) or joint-replacing (group B) procedures for IMRCT unaccompanied by severe osteoarthritis with a pseudoparetic shoulder function were retrospectively included. Clinical assessment included the Constant Score (CS), the Subjective Shoulder Value (SSV) and the Visual Analog Score (VAS) at baseline and at latest follow-up. Furthermore, the complication and revision rates were assessed.

Results

Overall, a total 56 patients were included of whom each 28 patients formed group A (male, 36%) and B (male, 53%) with a mean patient age at time of surgery of 70 ± 7 years and 72 ± 7 years, respectively. The mean follow-up period was 56 ± 17 months. At final follow-up, the total CS (group A: 66 ± 14 points; group B 54 ± 15 points) was significantly increased after arthroscopic treatment when compared to RTSA (p=0.011). However, no significant differences were detected with SSV (p=0.583) and VAS (p=0.536). Although complication rate (11% versus 18%) was not significantly different (p=0.705), number of revision surgeries was significantly higher in group B when compared to group A (p=0.041).

Conclusions

In non-arthritic pseudoparetic shoulders, both joint-preserving and joint-replacing procedures yielded good clinical midterm outcomes for the treatment of degenerative IMRCTs. Despite of comparable functional and satisfactory functional improvement, increased complication rates and surgical invasiveness outweigh the benefits of primary RTSA and therefore reserve this procedure to a second-line treatment in pseudoparetic patients without any signs of severe cuff arthropathy.

Is residual tendon a predictor of outcome following arthroscopic rotator cuff repair? A preliminary outlook at short-term follow-up

BACKGROUND

Multiple factors including muscle atrophy, fatty infiltration, smoking, advanced patient age, and increasing tear size have been identified as risk factors for retear after rotator cuff repair. However, little is known about what effect the length of the residual rotator cuff tendon has on the success of repair and patient outcomes.

METHODS

This study included 64 patients. Patients were stratified based on a residual tendon length of greater than 15 mm (group 1, residual tendon) or 15 mm or less (group 2, no residual tendon). Rotator cuff tendon integrity was then evaluated using ultrasound imaging at 6 months. Outcome measures included the Single Assessment Numeric Evaluation score, visual analog scale score, EQ5D Index score, Global Rating of Change score, and Penn Shoulder Score.

RESULTS

No differences were found between groups regarding demographic data or repair configuration. Assessment of tendon healing demonstrated an increased rate of tendons that had "not healed" in group 2 (19.3% [n = 5] vs. 13.2% [n = 5]), but this difference was not statistically significant (P = .55). Functional outcome scores improved significantly from preoperatively to final follow-up in both groups and displayed no differences at 6-month follow-up.

CONCLUSION

A smaller residual tendon length was not a negative predictor of clinical outcomes following arthroscopic rotator cuff repair in patients with short-term follow-up. Although there was a trend toward a decreased rate of healing in patients with smaller residual tendons, this was not significant.

Influence of sutures configuration on the strength of tendon-patch joints for rotator cuff tears treatment

PURPOSE

Massive rotator cuff tears are common in the aging population. The incidence of failed rotator cuff repairs is still quite high, especially in the treatment of full-thickness tears or revision repairs. In this context, natural and synthetic meshes can be used as augmentation scaffolds or as devices to close the gap between a retracted tendon and the bone. The purpose of this work is to evaluate the ultimate tensile strength of different tendon-patch joints in order to consider their use in the treatment of massive cuff tears.

MATERIALS AND METHODS

Porcine tendons and a synthetic low-density polypropylene mesh have been used. A preliminary study on the tensile strength of tendons and patches has been performed. Different patch-tendon joints have been studied by modifying the number and the layout of the sutures. For every joint, the tensile test, performed through an electromechanical machine, has been repeated at least twice to obtain reliable data.

RESULTS

Experimental tensile tests on tendons and patches have given good results with very low dispersion data. Mean values of the calculated ultimate tensile stresses are, respectively, about 34 MPa and 16 MPa for tendons and patches. As regards the sutures arrangement, the staggered layout gave, for all joints, a higher tensile strength than the regular (aligned) one. Different ultimate tensile stress values, depending on the sutures number and layout, have been calculated for the joints.

CONCLUSION

Synthetic patches could be an interesting option to repair massive cuff tears and to improve, in a significant way, pain, range of motion and strength at time 0, so reducing the rehabilitation time. Obtained results demonstrated that joints with a suitable number and layout of sutures could ensure very good mechanical performances. The failure load of the tendon-patch joint, in fact, is higher than the working load on a healthy tendon.

Long-term results of reverse total shoulder arthroplasty for rotator cuff dysfunction: a systematic review of longitudinal outcomes

BACKGROUND

The aim of this systematic review was to evaluate the longitudinal evolution of midterm to long-term results of reverse total shoulder arthroplasty (RTSA) for patients with massive irreparable rotator cuff tears (miRCT).

METHODS

Databases were scanned for studies of RTSA for miRCT. Studies with a minimum Level IV of evidence were considered eligible. Studies were included if they reported a minimum of 5 years of follow-up and excluded if they reported RTSA combined with tendon transfers or as revision arthroplasty. Data were grouped based on results after 5 to 7 years, 7 to 10 years, and 10 to 20 years of follow-up.

RESULTS

Eight studies with a total of 365 shoulders were included. After a mean follow-up of 9.5 years (range, 5-20 years), the preoperative absolute and relative Constant scores were significantly improved from 24 to 59 points (P = .004) and from 33% to 74% (P = .009). The preoperative Subjective Shoulder Value improved from 23% to 72% (P = .049). Active anterior elevation and abduction also improved significantly (P = .004 and P = .014, respectively), but active external rotation remained unchanged (P = .855). None of the clinical scores or active ranges of motion significantly deteriorated up to 20 years after the operation (P > .05). After 10 years, 42% of the RTSAs showed grade III or IV inferior scapular notching.

CONCLUSION

Pooled long-term results of RTSA for miRCT show significant improvement of overhead function and of objective and subjective outcome scores up to 20 years after surgery. Shoulder function and outcome scores also showed no significant deterioration between 5 and 20 years of follow-up. Longer follow-up will be needed to determine ultimate longevity.

Shear Wave Elastography Can Predict Passive Stiffness of Supraspinatus Musculotendinous Unit During Arthroscopic Rotator Cuff Repair for Presurgical Planning

PURPOSE

To determine the feasibility of shear wave elastography (SWE) with B-mode ultrasound in predicting the stiffness of the rotator cuff muscle before arthroscopic rotator cuff repair to evaluate the difficulty of the surgical procedure, as well as to compare SWE with the Goutallier stage on magnetic resonance imaging (MRI).

METHODS

Thirty-eight patients with a full-thickness supraspinatus tear requiring arthroscopic rotator cuff repair participated. The Goutallier stage of fatty infiltration on MRI was measured before surgery, as was the SWE modulus of the anterior superficial, anterior deep, posterior superficial, and posterior deep (PD) regions of the supraspinatus muscle. To measure the stiffness of the supraspinatus musculotendinous unit during surgery, the supraspinatus tendon was axially stretched until the anatomic insertion site was reached, and force per deformation was recorded. The correlation between stiffness of the supraspinatus and SWE value in each region of the supraspinatus muscle or Goutallier stage was determined. In addition, patients were divided into 2 groups: (1) In the complete footprint coverage group, greater than 50% of the footprint was covered during the stiffness measurement, and (2) in the incomplete footprint coverage group, less than 50% of the footprint was covered during the stiffness measurement. Differences in SWE value and Goutallier stage were measured between the 2 groups.

RESULTS

The best correlation of stiffness with the SWE modulus of the PD muscle of the supraspinatus was R = 0.69, and the correlation of stiffness with the Goutallier stage on MRI was R = 0.48. The SWE value of the PD region was greater in the incomplete footprint coverage group than in the complete footprint coverage group, although the Goutallier stage was not significantly different.

CONCLUSIONS

The highest correlation with stiffness of the supraspinatus musculotendinous unit was with the SWE modulus of the PD muscle, as compared with SWE evaluation of the other regions or the Goutallier stage on MRI. Ultrasound SWE can predict the stiffness of the supraspinatus musculotendinous unit best.

CLINICAL RELEVANCE

Rotator cuff retraction adds difficulty to arthroscopic rotator cuff repair. Ultrasound SWE may be used for presurgical planning.

Extensibility of the supraspinatus muscle can be predicted by combining shear wave elastography and magnetic resonance imaging-measured quantitative metrics of stiffness and volumetric fat infiltration: A cadaveric study

BACKGROUND

A torn rotator cuff tendon will retract over time causing changes in muscle properties and decreasing its extensibility, or deformation. During surgery, large tensile loads are applied to bring the torn tendon to the footprint. Poor muscle extensibility and large tensile stresses at the repair might lead to gap formation or re-tear of the repair. A quantitative evaluation of muscle properties could be used to predict the extensibility of the supraspinatus (SSP) muscle.

METHOD

Magnetic resonance imaging (MRI)-measured volumetric fat fraction and shear wave elastography (SWE)-measured elastic modulus of the SSP muscle were obtained on seventeen cadaveric shoulders. Experimental extensibility and stiffness were then measured by axially pulling the tendon up-to 60 N. Univariate and multivariate analyses were used to determine the correlation and contribution of fat fraction and elastic modulus to experimental outcomes.

FINDINGS

SWE moduli negatively correlated with SSP muscle extensibility (r = 0.54-0.58, P ≤ 0.0259); fat fraction resulted in a positive correlation (r = 0.69, P = 0.0021). SWE measurements, solely, explained up to 34% and 33% of the variability in measured extensibility and stiffness, respectively. Fat Fraction, solely, explained 48% of the variability in extensibility and 36% of the variability in stiffness. These methods combined predicted up to 62% of the musculotendinous extensibility.

INTERPRETATION

This study showed a comprehensive quantitative assessment of SSP muscle properties using SWE to estimate stiffness and MRI to measure fatty infiltration. The extensibility of the detached muscle/tendon unit was highly correlated to material properties of the muscle when these methods were used in combination.

Reverse shoulder arthroplasty for irreparable massive rotator cuff tears: a systematic review with meta-analysis and meta-regression

BACKGROUND

Massive rotator cuff tears (MRCTs) are very large tears that are often associated with an uncertain prognosis. Indeed, some MRCTs even without osteoarthritis are considered irreparable, and nonanatomic solutions are needed to improve the patient's symptoms. Reverse shoulder arthroplasty (RSA) is an option that can provide a more predictable pain relief and recovery of function. Nonetheless, outcomes after RSA for irreparable MRCTs have not been well defined. The aim of this study was to quantitatively aggregate the findings associated with the use of RSA in this subset of patients and analyze the effect on patient functional status and pain.

METHODS

A comprehensive search was performed until October 2015 using MEDLINE, Scopus, Cochrane Database of Systematic Reviews, and Central Register of Controlled Trials databases. Studies that assessed the outcomes of RSA in patients with irreparable MRCT without osteoarthritis (with at least 2 years of follow-up) were included. If the results of MRCT without osteoarthritis were not possible to subgroup, the study was excluded. Methodologic quality was assessed using the Coleman Methodology Score.

RESULTS

Included were 6 studies (266 shoulders) with a follow-up ranging from 24 to 61.4 months. The mean Coleman Methodology Score was 58.2 ± 11.8 points. There was an overall improvement from preoperative to postoperative assessments of the clinical score (Cohen d = 1.35, P < .001), forward flexion (d = 0.50, P = .009), external rotation (d = 0.40, P < .001), function (d = 1.04, P < .001), and pain (d = -0.89, P < .001).

CONCLUSION

Patients with irreparable MRCT without presence of osteoarthritis have a high likelihood of achieving a painless shoulder and functional improvements after RSA.

Quantifying extensibility of rotator cuff muscle with tendon rupture using shear wave elastography: A cadaveric study

Surgical repair for large rotator cuff tear remains challenging due to tear size, altered muscle mechanical properties, and poor musculotendinous extensibility. Insufficient extensibility might lead to an incomplete reconstruction; moreover, excessive stresses after repair may result in repair failure without healing. Therefore, estimates of extensibility of cuff muscles can help in pre-surgical planning to prevent unexpected scenarios during surgery. The purpose of this study was to determine if quantified mechanical properties of the supraspinatus muscle using shear wave elastography (SWE) could be used to predict the extensibility of the musculotendinous unit on cadaveric specimens. Forty-five fresh-frozen cadaveric shoulders (25 intact and 20 with rotator cuff tear) were used for the study. Passive stiffness of 4 anatomical regions in the supraspinatus muscle was first measured using SWE. After detaching the distal edge of supraspinatus muscle from other cuff muscles, the detached muscle was axially pulled with the scapula fixed. The correlation between the SWE modulus and the extensibility of the muscle under 30 and 60N loads was assessed. There was a significant negative correlation between SWE measurements and the experimental extensibility. SWE modulus for the anterior-deep region in the supraspinatus muscle showed the strongest correlation with extensibility under 30N (r=0.70, P<0.001) and 60N (r=0.68, P<0.001). Quantitative SWE assessment for the supraspinatus muscle was highly correlated with extensibility of musculotendinous unit on cadaveric shoulders. This technique may be used to predict the extensibility for rotator cuff tears for pre-surgical planning.

Neer Award 2016: reduced muscle degeneration and decreased fatty infiltration after rotator cuff tear in a poly(ADP-ribose) polymerase 1 (PARP-1) knock-out mouse model

BACKGROUND

Disturbed muscular architecture, atrophy, and fatty infiltration remain irreversible in chronic rotator cuff tears even after repair. Poly (adenosine 5'-diphosphate-ribose) polymerase 1 (PARP-1) is a key regulator of inflammation, apoptosis, muscle atrophy, muscle regeneration, and adipocyte development. We hypothesized that the absence of PARP-1 would lead to a reduction in damage to the muscle subsequent to combined tenotomy and neurectomy in a PARP-1 knockout (KO) mouse model.

METHODS

PARP-1 KO and wild-type C57BL/6 (WT group) mice were analyzed at 1, 6, and 12 weeks (total n = 84). In all mice, the supraspinatus and infraspinatus muscles of the left shoulder were detached and denervated. Macroscopic analysis, magnetic resonance imaging, gene expression analysis, immunohistochemistry, and histology were used to assess the differences in PARP-1 KO and WT mice.

RESULTS

The muscles in the PARP-1 KO group had significantly less retraction, atrophy, and fatty infiltration after 12 weeks than in the WT group. Gene expression of inflammatory, apoptotic, adipogenic, and muscular atrophy genes was significantly decreased in PARP-1 KO mice in the first 6 weeks.

DISCUSSION

Absence of PARP-1 leads to a reduction in muscular architectural damage, early inflammation, apoptosis, atrophy, and fatty infiltration after combined tenotomy and neurectomy of the rotator cuff muscle. Although the macroscopic reaction to injury is similar in the first 6 weeks, the ability of the muscles to regenerate was much greater in the PARP-1 KO group, leading to a near-normalization of the muscle after 12 weeks.

Latissimus Dorsi Transfer in Posterior Irreparable Rotator Cuff Tears

BACKGROUND

Massive rotator cuff tears pose a difficult and complex challenge even for the experienced surgeon; inability to repair these tears by conventional means designates them as irreparable, while management becomes quite taxing. Several operative options have been suggested for the management of such lesions with varying degrees of success, while it is imperative to match patient demands and expectations to the predicted outcome.

METHODS

Research articles are examined and key concepts are discussed, in order to provide an evidence based review of the available literature. The anatomy and pathomechanics along with the indications, contraindications and surgical techniques are reported.

RESULTS

Transfer of the Latissimus dorsi has been used with success to restore shoulder function in deficits of the posterior rotator cuff. Although it can be used in a variety of settings, the ideal patient for a Latissimus dorsi tendon transfer is a young and active individual, with no glenohumeral osteoarthritis that has a severe disability and weakness related to an irreparable posterior cuff tear.

CONCLUSION

Tendon transfers have proved to be a successful treatment option in salvaging this difficult problem, providing pain relief and restoring shoulder function. Despite the excellent functional outcomes and pain suppression following operation, a variety of factors may affect the outcome; thus making indications and preoperative assessment a valuable component.

Tendon Collagen Crosslinking Offers Potential to Improve Suture Pullout in Rotator Cuff Repair: An Ex Vivo Sheep Study

BACKGROUND

The suture-tendon interface is often the weakest link in tendon to bone repair of massive rotator cuff tears. Genipin is a low-toxicity collagen crosslinker derived from the gardenia fruit that has been shown to augment collagen tissue strength and mechanically arrest tendon-tear progression.

QUESTION/PURPOSE

The purpose of the current study was to evaluate whether genipin crosslinking can sufficiently augment the suture-tendon interface to improve suture pullout strength using simple single-loop sutures and the modified Mason-Allen technique. The study also aimed to assess whether time of genipin treatment is a relevant factor in efficacy.

METHODS

In an ex vivo (cadaveric) sheep rotator cuff tendon model, a total of 142 suture pullout tests were performed on 32 infraspinatus tendons. Each tendon was prepared with three single-loop stitches. Two groups were pretreated by incubation in genipin solution for either 4 hours or 24 hours. Two corresponding control groups were incubated in phosphate buffered saline for the same periods. The same test protocol was applied to tendons using modified Mason-Allen technique stitch patterns. Each suture was loaded to failure on a universal materials testing machine. Suture pullout force, stiffness, and work to failure were calculated from force-displacement data, and then compared among the groups.

RESULTS

Median single-loop pullout force on tendons incubated for 24 hours in genipin yielded an approximately 30% increase in maximum pullout force for single-loop stitches with a median of 73 N (range, 56-114 N) compared with 56 N (range, 40-69 N; difference of medians = 17 N; p = 0.028), with corresponding increases in the required work to failure but not stiffness. Genipin treatment for 4 hours showed no added benefit for suture-pullout behavior (46 N, [range, 35-95 N] versus 45 N, [range, 28-63 N]; difference of medians, 1 N; p = 1). No tested genipin crosslinking conditions indicated benefit for tendons grasped using the modified Mason-Allen technique after 4 hours (162 N, [range, 143-193 N] versus 140 N, [range, 129-151 N]; difference of medians, 22 N; p = 0.114) or after 24 hours of crosslinking (172 N, [range, 42-183 N] versus 164 N [range, 151-180 N]; difference of medians, 8 N; p = 0.886).

CONCLUSION

Exogenous collagen crosslinking in genipin can markedly improve resistance to pullout at the tendon-suture interface for simple stitch patterns while the modified Mason-Allen stitch showed no benefit in an ex vivo animal model.

CLINICAL RELEVANCE

Tendon strength augmentation by genipin pretreatment offers the potential to improve suture retention properties. Future studies are warranted for the development of clinically viable intraoperative delivery strategies and in vivo testing for safety and efficacy.

Lengthening of the subscapularis tendon as a sign of partial tearing in continuity

BACKGROUND

The quantification of a subscapularis tendon lesion may be difficult on magnetic resonance imaging, as well as during arthroscopic inspection. Consequently, the surgical decision of whether to only debride a degenerated tendon or to lateralize the more intact tendon portion may be arbitrary. This study aims to quantify the length of the subscapularis tendon as a sign of partial tendon tearing.

METHODS

We retrospectively identified 92 magnetic resonance arthrography studies of suspected rotator cuff lesions obtained 3 months before shoulder arthroscopy. The myotendinous junction was identified, and the subscapularis tendon and muscle lengths were measured. Findings on arthroscopy performed later were used as the diagnostic gold standard for tendon integrity and compared with the magnetic resonance data.

RESULTS

Arthroscopy showed an intact subscapularis tendon in 43 patients, tendinopathy in 21 patients, and a partial rupture in 28 patients. The mean subscapularis tendon lengths were 40 mm in cases of intact subscapularis musculotendinous units, 45 mm in cases of tendinopathy, and 53 mm in cases of partial tears, whereas the mean subscapularis muscle lengths were 105 mm, 94 mm, and 95 mm, respectively, in these groups.

CONCLUSION

Partial tears of the subscapularis tendon lead to muscle shortening by approximately 10% and elongation of the tendon by approximately 32%, which may be interpreted as muscle retraction and a tendon rupture in continuity. If the subscapularis tendon has an apparent length of greater than 60 mm, the probability of a tear is 98%. Determination of the tendon length may therefore be a useful additional tool to quantify the integrity of the subscapularis tendon and degree of myotendinous retraction.

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.

Tendon quality in small unilateral supraspinatus tendon tears. Real-time sonoelastography correlates with clinical findings

PURPOSE

To investigate the feasibility of real-time sonoelastography in the assessment of the mechanical tendon properties in small unilateral supraspinatus tears, to describe the sonoelastographic properties of the torn supraspinatus tendons and to correlate real-time sonoelastography findings with clinical results and demographic data.

METHODS

All the patients presenting for a unilateral rotator cuff tear were prospectively scrutinized. Clinical evaluation included complete physical examination, VAS, Quick DASH, Constant-Murley score, Simple Shoulder Test, ASES score and UCLA score. Radiological evaluation was performed with conventional ultrasounds and real-time sonoelastography; this is a noninvasive method that uses ultrasounds to evaluate the mechanical properties of tissues, reflecting their quality, that can be semi-quantitatively estimated using the strain index. During the enrolment period, 92 patients were scrutinized, and 50 were included in the study.

RESULTS

A negative correlation between strain index and VAS for pain, a strong positive correlation between strain index and Constant-Murley score and ASES score were found. Comparable results were observed in male and female patients, but in males, we found a strong positive correlation also for Simple Shoulder Test and UCLA score.

CONCLUSIONS

Real-time sonoelastography was a feasible method applicable in the assessment of tendon quality in small supraspinatus tears, and its findings correlated with the clinical results of the patients. In day-by-day clinical practice, this information is very important because quality of tendons is one of the most important prognostic factors for surgeons performing rotator cuff repair.

LEVEL OF EVIDENCE

III.

Partial supraspinatus tears are associated with tendon lengthening

PURPOSE

Tendon tear may result in muscular retraction with the loss of contractile amplitude and strength of the rotator cuff muscles. Currently, neither a validated method of measuring supraspinatus tendon length nor normal values are known. It was therefore the purpose of this study to measure the normal length of the supraspinatus tendon and to determine whether partial tears are associated with changes in tendon length.

METHODS

MR examinations of 49 asymptomatic volunteers and 37 patients with arthroscopically proven, isolated partial tears of the supraspinatus tendon were compared. The ratio of the extramuscular tendon length to the distance between the footprint and the glenoid surface was calculated (TL/FG ratio). Tendon length measurements were taken by two independent readers at the bursal and articular surfaces at the anterior, the central and the posterior parts of the tendon.

RESULTS

TL/FG ratios at the bursal surface of tendons with partial tears were significantly higher than those in the control group [anterior: 0.78 ± 0.20 vs. 0.66 ± 0.15 (p < 0.05); central: 0.61 ± 0.13 vs. 0.52 ± 0.10 (p < 0.05); posterior: 0.57 ± 0.15 vs. 0.52 ± 0.10 (p < 0.05)]. At the articular surface, differences were significant only anteriorly [0.60 ± 0.13, vs. 0.54 ± 0.10 (p < 0.05)]. A cut-off TL/FG ratio of 0.63 for measurements at the bursal surface in the center of the tendon achieved a sensitivity of 46 % and a specificity of 92 % for the identification of partial cuff tearing.

CONCLUSION

A reproducible method for measurement of extramuscular supraspinatus tendon length is described. Partial tearing of the supraspinatus tendon is associated with significant tendon lengthening, suggesting failure in continuity, and this is most reliably measured on the bursal surface.

LEVEL OF EVIDENCE

III.

Animal model for chronic massive rotator cuff tear: behavioural and histologic analysis

PURPOSE

Massive rotator cuff tears (MRCT) are usually chronic lesions that present associated degenerative changes of the myotendinous unit that have been implicated in limitations for surgical repair. In order to develop effective therapies, it is important to establish animal models that mimic the hallmarks of the injury itself. Therefore, in the present work, we aimed to (1) optimize a rodent animal model of MRCT that closely reproduces the fatty infiltration of the cuff muscles seen in humans and (2) describe the effects of unilateral or bilateral lesion in terms of histology and behaviour.

METHODS

Massive tear was defined as two rotator cuff tendons-supraspinatus and infraspinatus-section. Twenty-one Wistar rats were randomly assigned to four groups: bilateral lesion (five animals), right-sided unilateral lesion (five animals), left-sided unilateral lesion (five animals) and control (six animals). Behaviour was analyzed with open field and staircase test, 16 weeks after lesion. After that, animals were killed, and the supraspinatus and infraspinatus muscles were processed.

RESULTS

Histologic analysis revealed adipocytes, fatty infiltration and atrophy in the injured side with a greater consistency of these degenerative changes in the bilateral lesion group. Behaviour analysis revealed a significant functional impairment of the fine motor control of the forepaw analyzed in staircase test where the number of eaten pellets was significantly higher in sham animals (sham = 7 ± 5.0; left unilateral = 2.6 ± 3.0; right unilateral = 0 ± 0; and bilateral = 0 ± 0, p < 0.05). A trend to reach a lower level of steps, in more injured animals, was also observed (sham animals = 3 ± 1.6 > left unilateral = 2 ± 2.1 > right unilateral = 0.8 ± 1.3 > bilateral = 0.8 ± 1.1).

CONCLUSIONS

The present study has been able to establish an animal model that disclosed the hallmarks of MRCT. This can now be used as a valuable, cost-effective, pre-clinical instrument to assist in the development of advanced tissue engineered strategies. Moreover, this animal model overcomes some of the limitations of those that have been reported so far and thus represents a more reliable source for the assessment of future therapeutic strategies with potential clinical relevance.

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.

Release of tensile strain on engineered human tendon tissue disturbs cell adhesions, changes matrix architecture, and induces an inflammatory phenotype

Mechanical loading of tendon cells results in an upregulation of mechanotransduction signaling pathways, cell-matrix adhesion and collagen synthesis, but whether unloading removes these responses is unclear. We investigated the response to tension release, with regard to matrix proteins, pro-inflammatory mediators and tendon phenotypic specific molecules, in an in vitro model where tendon-like tissue was engineered from human tendon cells. Tissue sampling was performed 1, 2, 4 and 6 days after surgical de-tensioning of the tendon construct. When tensile stimulus was removed, integrin type collagen receptors showed a contrasting response with a clear drop in integrin subunit α11 mRNA and protein expression, and an increase in α2 integrin mRNA and protein levels. Further, specific markers for tendon cell differentiation declined and normal tendon architecture was disturbed, whereas pro-inflammatory molecules were upregulated. Stimulation with the cytokine TGF-β1 had distinct effects on some tendon-related genes in both tensioned and de-tensioned tissue. These findings indicate an important role of mechanical loading for cellular and matrix responses in tendon, including that loss of tension leads to a decrease in phenotypical markers for tendon, while expression of pro-inflammatory mediators is induced.

Neuropathy of the suprascapular nerve and massive rotator cuff tears: a prospective electromyographic study

BACKGROUND

An association between massive rotator cuff tear (RCT) and suprascapular nerve neuropathy has previously been suggested. The anatomic course of the suprascapular nerve is relatively fixed along its passage. Thus, injury to the nerve by trauma, compression, and iatrogenic reasons is well documented. However, the association between retraction of the RCT and development of neuropathy of the suprascapular nerve remains unclear. We aimed to prospectively evaluate the suprascapular nerve for preoperative neurodiagnostic abnormalities in shoulders with massive RCT.

METHODS AND MATERIALS

A prospective study was performed in 2 centers. Fifty patients with retracted tears of both supraspinatus and infraspinatus were evaluated. This was confirmed with preoperative computed tomography arthrography, and the fatty infiltration of the affected muscles was graded. Forty-nine preoperative electromyograms were performed in a standardized fashion and the results analyzed twice.

RESULTS

Of 49 shoulders, 6 (12%) had neurologic lesions noted on electromyography: 1 suprascapular nerve neuropathy, 1 radicular lesion of the C5 root, 1 affected electromyogram in the context of a previous stroke, and 3 cases of partial axillary nerve palsy with a history of shoulder dislocation. No difference or diminution of the latency or amplitude of the electromyographic curve was found in the cases that presented significant fatty infiltration.

CONCLUSION

This study did not detect a suprascapular lesion in the majority of cases of massive RCT. With a low association of neuropathy with massive RCT, we find no evidence to support the routine practice of suprascapular nerve release when RCT repair is performed.

Influence of preoperative musculotendinous junction position on rotator cuff healing using single-row technique

PURPOSE

The purpose of this study was to evaluate the correlation of rotator cuff musculotendinous junction (MTJ) retraction with healing after rotator cuff repair and with preoperative sagittal tear size.

METHODS

We reviewed preoperative and postoperative magnetic resonance imaging (MRI) studies of 51 patients undergoing arthroscopic single-row rotator cuff repair between March 1, 2005, and February 20, 2010. Preoperative MRI studies were evaluated for anteroposterior tear size, tendon retraction, tendon length, muscle quality, and MTJ position with respect to the glenoid. The position of the MTJ was referenced off the glenoid face as either lateral or medial. Postoperative MRI studies obtained at a minimum of 1 year postoperatively (mean, 25 ± 13.9 months) were evaluated for healing, tendon length, and MTJ position.

RESULTS

We found that 39 of 51 tears (76%) healed, with 26 of 30 small/medium tears (87%) and 13 of 21 large/massive tears (62%) healing. Greater tendon retraction, worse preoperative muscle quality, and a more medialized MTJ were all associated with worse tendon healing (P < .05). Of tears that had a preoperative MTJ lateral to the face of the glenoid, 93% healed, whereas only 55% of tears that had a preoperative MTJ medial to the face of the glenoid healed (P < .05). Healed repairs that had limited tendon lengthening (<1 cm) and limited MTJ position change (<1 cm) from preoperative were found to be smaller, had less preoperative tendon retraction, had less preoperative MTJ medialization, and had less preoperative rotator cuff fatty infiltration (P < .05).

CONCLUSIONS

Preoperative MTJ medialization, tendon retraction, and muscle quality are all predictive of tendon healing postoperatively when using a single-row rotator cuff repair technique. The position of the MTJ with respect to the glenoid face can be predictive of healing, with over 90% healing if lateral and 50% if medial to the face. Lengthening of the tendon accounts for a significant percentage of the musculotendinous unit lengthening that occurs in healed tears as opposed to muscle elongation.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Age-related changes in the cellular, mechanical, and contractile properties of rat tail tendons

Tendon laxity following injury, cyclic creep, or repair has been shown to alter the normal homeostasis of tendon cells, which can lead to degenerative changes in the extracellular matrix. While tendon cells have been shown to have an inherent contractile mechanism that gives them some ability to retighten lax tendons and reestablish a homeostatic cellular environment, the effect of age on this process is unknown. To determine the effect of aging on cell number, cell shape, and tensile modulus on tendons as well as the rate of cell-mediated contraction of lax tendons, tail tendon fascicles from 1-, 3-, and 12-month-old rats were analyzed. Aging results in a decrease (p < 0.001) in cell number per mm(2): 1 m (981 ± 119), 3 m (570 ± 108), and 12 m (453 ± 23), a more flattened (p < 0.001) cell nuclei shape and a higher (p < 0.001) tensile modulus (MPa) of the tendons: 1 m (291 ± 2), 3 m (527 ± 38), and 12 m (640 ± 102). Both the extent and rate of contraction over 7 days decreased with age (p = 0.007). This decrease in contraction rate with age correlates to the observed changes seen in aging tendons [increased modulus (r(2) = 0.95), decreased cell number (r(2) = 0.89)]. The ability of tendons to regain normal tension following injury or exercise-induced laxity is a key factor in the recovery of tendon function. The decreased contraction rate as a function of age observed in the current study may limit the ability of tendon cells to retighten lax tendons in older individuals. This, in turn, may place these structures at further risk for injury or altered function.

Arthroscopic single-row modified mason-allen repair versus double-row suture bridge reconstruction for supraspinatus tendon tears: a matched-pair analysis

BACKGROUND

Arthroscopic double-row fixation of supraspinatus tendon tears compared with single-row techniques is still a matter of debate.

HYPOTHESIS

Arthroscopic double-row rotator cuff repair using the suture bridge technique provides better clinical results and lower retear rates than does single-row repair using a modified Mason-Allen stitch technique.

STUDY DESIGN

Cohort study; Level of evidence 3.

METHODS

Forty patients underwent either an arthroscopic single-row modified Mason-Allen stitch (SR) (n = 20; mean age ± SD, 61.5 ± 7.4 y) or a modified suture bridge double-row repair (DR) (n = 20; age, 61.2 ± 7.5 y). The anteroposterior extension was classified as Bateman I in 10% and Bateman II in 90% of patients in the SR group and as Bateman II in 80% and Bateman III in 20% of patients in the DR group. Patients were matched for sex and age. The subjective shoulder value (SSV), Constant-Murley score (CS), and Western Ontario Rotator Cuff Index (WORC) were used for clinical follow-up. Furthermore, MRI scans were conducted for analysis of tendon integrity, muscle atrophy, and fatty infiltration via semiquantitative signal intensity analysis. In addition, re-defect patterns were evaluated.

RESULTS

The mean follow-up time in the SR group was 16.8 ± 4.6 months. The mean SSV was 91.0% ± 8.8%, mean CS was 82.2 ± 8.1 (contralateral side, 88.8 ± 5.3), and mean WORC score was 96.5% ± 3.2%. The mean follow-up time in the DR group was 23.4 ± 2.9 months, with patients achieving scores of 92.9% ± 9.6% for the SSV, 77.0 ± 8.6 for the CS (contralateral side, 76.7 ± 17.1), and 90.7% ± 12.6% for the WORC (P > .05). No significant differences were detected in the clinical outcome between groups. Tendon integrity was as follows. Type 1, none in either group; type 2, 4 SR and 5 DR; type 3, 9 SR and 10 DR; type 4, 3 SR and 3 DR; and type 5, 3 SR and 2 DR. The failure rate was 31.6% (n = 6) in the SR group and 25% (n = 5) in the DR group (P > .05). No significant differences were obtained for muscular atrophy or fatty degeneration (SR group, 0.94 ± 0.16; DR group, 1.15 ± 0.5) (P > .05). Re-defects revealed lateral cuff failure in 83.3% of SR patients in contrast to patients treated with DR techniques. The re-defect pattern was medial cuff failure in 80% of the patients.

CONCLUSION

The clinical results after modified Mason-Allen single-row versus double-mattress suture bridge technique did not demonstrate significant differences in a matched patient cohort. Concerning the failure mode, single- and double-row techniques seem to demonstrate different re-defect patterns.

Re-establishment of cytoskeletal tensional homeostasis in lax tendons occurs through an actin-mediated cellular contraction of the extracellular matrix

Cytoskeletal tensional homeostasis is known to be an important factor in controlling catabolic gene expression in tendon cells. Loss of cell tension in lax rat tail tendon fascicles (RTTfs) has been associated with an upregulation of MMP-13 gene expression and protein synthesis. To determine the role of the actin cytoskeleton in re-establishing tensional homeostasis in lax tendons, RTTfs were allowed to freely contract in vitro for 8 days. The cultured RTTfs contracted rapidly, reaching 50% of their initial length by 3 days. This contraction was associated with the presence of α-smooth muscle actin positive cells within the tendon. Disruption of the actin network by cytochalasian D caused an immediate and significant elongation of the contracted RTTfs. Subsequent removal of the cytochalasian D re-initiated the contraction process. When lax RTTfs were allowed to contract between fixed clamps in culture and become taut, they demonstrated a marked decrease in MMP-13 staining intensity when compared to freely contracting RTTfs. The ability of native tendon cells to contract lax tendons and re-establish their homeostatic "set point" with respect to collagenase production may be an important mechanism in the recovery of tendons elongated by injury, surgical positioning, or cyclic, viscoelastic creep secondary to repetitive exercise.

Retraction of supraspinatus muscle and tendon as predictors of success of rotator cuff repair

BACKGROUND

The structural failure rate of rotator cuff repair can exceed 50%. Important predictors for repair failure are preoperative fatty muscle infiltration and myotendinous retraction.

PURPOSE

To quantitatively assess the prognostic value of preoperative retraction of both the supraspinatus muscle and tendon for the outcome of supraspinatus repair.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

In 33 shoulders with complete supraspinatus tendon ruptures subjected to arthroscopic repair, magnetic resonance imaging (MRI) scans taken preoperatively and after a mean follow-up of 24 months were studied. The exact position of the lateral extension of the supraspinatus muscle and of the tendon end was evaluated and correlated with the preoperative stage of fatty infiltration (Goutallier) and the failure rate of tendon repair.

RESULTS

The mean lengthening of the muscle and tendon end was -3 mm and 4 mm in the failed repairs (n = 19) and 14 mm and 8 mm in the successful repairs (n = 14). If the supraspinatus had preoperative Goutallier stages 2 to 3 and a tendon length of less than 15 mm, the failure rate was 92%, but if the tendon length was greater than 15 mm, the failure rate was only 33%. With Goutallier stages 0 to 1, the corresponding failure rates were 57% and 25%, respectively.

CONCLUSION

Rotator cuff repair lengthens the tendon, even if the repair fails. The possibility to lengthen the myotendinous unit is related to the preoperative length of the tendon. The combination of Goutallier grading and preoperative tendon length appears to be a more powerful predictor for the reparability of a tendon tear than Goutallier grading alone.

Device for lengthening of a musculotendinous unit by direct continuous traction in the sheep

Background

Retraction, atrophy and fatty infiltration are signs subsequent to chronic rotator cuff tendon tears. They are associated with an increased pennation angle and a shortening of the muscle fibers in series. These deleterious changes of the muscular architecture are not reversible with current repair techniques and are the main factors for failed rotator cuff tendon repair. Whereas fast stretching of the retracted musculotendinous unit results in proliferation of non-contractile fibrous tissue, slow stretching may lead to muscle regeneration in terms of sarcomerogenesis. To slowly stretch the retracted musculotendinous unit in a sheep model, two here described tensioning devices have been developed and mounted on the scapular spine of the sheep using an expandable threaded rod, which has been interposed between the retracted tendon end and the original insertion site at the humeral head. Traction is transmitted in line with the musculotendinous unit by sutures knotted on the expandable threaded rod. The threaded rod of the tensioner is driven within the body through a rotating axis, which enters the body on the opposite side. The tendon end, which was previously released (16 weeks prior) from its insertion site with a bone chip, was elongated with a velocity of 1 mm/day.

Results

After several steps of technical improvements, the tensioner proved to be capable of actively stretching the retracted and degenerated muscle back to the original length and to withstand the external forces acting on it.

Conclusion

This technical report describes the experimental technique for continuous elongation of the musculotendinous unit and reversion of the length of chronically shortened muscle.

Quantitative analysis of muscle and tendon retraction in chronic rotator cuff tears

BACKGROUND

Musculotendinous retraction is a limiting factor for repair of long-standing rotator cuff tears. However, it is currently unknown to what extent the muscle and tendon contribute to the degree of total retraction. Further understanding of this may possibly influence the strategy of musculotendinous reconstruction.

PURPOSE

To analyze the contribution of muscle and tendon to the process of myotendinous retraction.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Magnetic resonance imaging of 130 shoulders with intact (n = 20) or completely torn supraspinatus tendons was analyzed. Fatty infiltration of the supraspinatus muscle was graded according to Goutallier stages. The degree of retraction of the tendon stump and of the musculotendinous junction was assessed.

RESULTS

There were 30 shoulders without evidence of supraspinatus fatty infiltration, 25 with stage 1, 23 with stage 2, 25 with stage 3, and 15 with stage 4 changes. The corresponding tear sizes (distance of tendon end from greater tuberosity) were 4, 21, 27, 37, and 41 mm; the distance of the myotendinous junction from the greater tuberosity was 22, 33, 39, 48, and 48 mm; and the length of the tendons (distance of tendon end to myotendinous junction) was 19, 13, 12, 11, and 8 mm, respectively. In Goutallier stage 3 and above, and in case of a positive tangent sign, the musculotendinous junction was, in 90% of the cases, retracted to or beyond the glenoid.

CONCLUSION

Musculotendinous retraction in chronic rotator cuff tears results mainly from shortening of the muscle fibers but in advanced stages results also from shortening of the tendon tissue itself. The present data demonstrate, for the first time, that the residual tendon stump in a tendon tear does not have the length of the original tendon and is further shortened over time. Therefore, direct anatomic tendon reinsertion will result in lengthening of the supraspinatus muscle greater than what it would have been before the tear.

The management of rotator cuff tears in the elderly

Rotator cuff tears occur commonly in the elderly causing significant pain and disability. In light of new treatment options developed over recent years, this article reviews the diagnosis and operative options available for this condition.

Animal models for translational research on shoulder pathologies: from bench to bedside

Several animal models have been used for in vivo and in vitro shoulder research. In vitro models, consisting of cadaveric specimens, are useful in providing basic understanding of the functioning of the shoulder and for biomechanical experiments. In vivo models provide the means to model living phenomena, such as tendon healing process, tendinopathy, instability, and adaptive responses to surgery. However, intrinsic differences among different species make translation to human shoulder pathologies difficult. Most of the animals used in experimental settings are quadrupeds, using the forelimbs for weight-bearing during locomotion, with no or minimal overhead activity. The various animal models already used to study shoulder pathologies are presented in this article. However, there is a lack of validation for these animal models, which provides challenge to the further research in this field.

Structure of retracted tendons after staged repair following continuous traction

PURPOSE

The effect of staged repair involving continuous re-lengthening of the retracted musculotendinous unit after rotator cuff tear is not known. We quantified changes in chronically retracted tendons undergoing no repair or a staged repair involving an initial re-lengthening of the musculotendinous unit by traction in a sheep model of massive rotator cuff tear.

MATERIALS AND METHODS

Infraspinatus tendons of 12 sheep were released and allowed to retract for 4 months. Repair was performed after the retracted musculotendinous unit had been progressively returned to its original length through continuous traction in 8 sheep (group I). In the other 4 sheep (group II) traction was not successful and the tendons remained retracted. Tendon structure was assessed macroscopically, by MRI, histology, and TEM.

RESULTS

Normalized to their contralateral controls, at sacrifice, tendon thickness was unchanged in group I (116%, n.s) and increased in group II (129%, P < 0.05), however with substantial shortening. Increased collagen fiber crimping and disorganization was found in group II, whereas in group I the differences from normal tendon were less pronounced.

CONCLUSION

Retracted musculotendinous units have deteriorated tendons, characterized by increased collagen fiber crimp, and ultrastructural collagen fibril atrophy and disorganization. Continuous traction may arrest and partially restore degenerative changes in retracted tendon. The findings of this study might contribute to new approaches for the treatment of chronic "irreparable" rotator cuff tears.

Negative muscle pennation angle as a sign of massive musculotendinous retraction after tendon tear: paradoxical function of the vastus lateralis muscle

In the presented case, an isolated vastus lateralis tendon tear resulted in a negative pennation angle of the distal muscle fibers acting paradoxical to the physiological direction of the proximal muscle fibers. This observation makes the value of an in situ repair of a far retracted tendon tear with interposition of a graft questionable and emphasizes early over late anatomic surgical restoration of the muscle architecture after tendon tears.

An anatomical description of the pennation angles and central tendon angle of the supraspinatus both in its normal configuration and with full thickness tears

HYPOTHESIS

It is hypothesized that supraspinatus central tendon retraction is related to functional deficit; yet, there is no literature comparing the normal and pathological pennation and central tendon angles using magnetic resonance imaging (MRI). Therefore, the aim of this study was to quantify the anterior and posterior muscle pennation angles, central tendon angle, and retraction of the supraspinatus using MRI.

METHODS

Anterior pennation angle (APA), posterior pennation angle (PPA), and central tendon angle (CTA) were measured from 2 groups: no tear (NT, n = 157), full thickness tears (FTT) with retraction (FTT, n = 156).

RESULTS

No tear (NT) average APA, PPA, and CTA were 19.0° (SD 5.9), 4.0° (SD 3.2), and 17.8° (SD 5.1). All differences were statistically significant (PPA < APA, P < .001; PPA < CTA, P < .001; CTA < APA, P < .001). FTT averages were 17.6° (SD 8.6), 16.7° (SD 12.2), and 7.3° (SD 4.9). Increasing retraction correlated to PPA (P < .001), APA (P < .002), and CTA (P < .001).

CONCLUSION

The size of a supraspinatus tear is directly correlated with muscle pennation and tendon retraction, and provides a direct measurement from MRI that can now be employed in further studies of functional deficit and tendon tear size.

Preclinical models for translating regenerative medicine therapies for rotator cuff repair

Despite improvements in the understanding of rotator cuff pathology and advances in surgical treatment options, repairs of chronic rotator cuff tears often re-tear or fail to heal after surgery. Hence, there is a critical need for new regenerative repair strategies that provide effective mechanical reinforcement of rotator cuff repair as well as stimulate and enhance the patient's intrinsic healing potential. This article will discuss and identify appropriate models for translating regenerative medicine therapies for rotator cuff repair. Animal models are an essential part of the research and development pathway; however, no one animal model reproduces all of the features of the human injury condition. The rat shoulder is considered the most appropriate model to investigate the initial safety, mechanism, and efficacy of biologic treatments aimed to enhance tendon-to-bone repair. Whereas large animal models are considered more appropriate to investigate the surgical methods, safety and efficacy of the mechanical-or combination biologic/mechanical-strategies are ultimately needed for treating human patients. The human cadaver shoulder model, performed using standard-of-care repair techniques, is considered the best for establishing the surgical techniques and mechanical efficacy of various repair strategies at time zero. While preclinical models provide a critical aspect of the translational pathway for engineered tissues, controlled clinical trials and postmarketing surveillance are also needed to define the efficacy, proper indications, and the method of application for each new regenerative medicine strategy.

The influence of the mechanical environment on remodelling of the patellar tendon

An understanding of the remodelling of tendon is crucial for the development of scientific methods of treatment and rehabilitation. This study tested the hypothesis that tendon adapts structurally in response to changes in functional loading. A novel model allowed manipulation of the mechanical environment of the patellar tendon in the presence of normal joint movement via the application of an adjustable external fixator mechanism between the patella and the tibia in sheep, while avoiding exposure of the patellar tendon itself. Stress shielding caused a significant reduction in the structural and material properties of stiffness (79%), ultimate load (69%), energy absorbed (61%), elastic modulus (76%) and ultimate stress (72%) of the tendon compared with controls. Compared with the material properties the structural properties exhibited better recovery after re-stressing with stiffness 97%, ultimate load 92%, energy absorbed 96%, elastic modulus 79% and ultimate stress 80%. The cross-sectional area of the re-stressed tendons was significantly greater than that of stress-shielded tendons. The remodelling phenomena exhibited in this study are consistent with a putative feedback mechanism under strain control. This study provides a basis from which to explore the interactions of tendon remodelling and mechanical environment.

Long-term functional and structural outcome in patients with intact repairs 1 year after open transosseous rotator cuff repair

HYPOTHESIS

Tendon-to-bone suture and a fatty degeneration index (FDI) <or= 2 are required to achieve an intact cuff in the mid-term. Our primary objective was to determine the structural and functional long-term outcomes of repaired cuffs that were intact after one year.

MATERIALS AND METHODS

We studied 30 cuffs with FDI <or= 2 at surgery and no tear one year after tension-free tendon-to-bone suture. Mean follow-up was 9 +/- 0.8 years. Gross tendon-stump lesions were excised prior to repair.

RESULTS

Re-tear after one year was rare: only one cuff showed a recurrent tear. In the 29 intact cuffs, mean un-weighted Constant score and sub-scores improved significantly (P values, < .0001- .0002; final Constant score = 77) for two years then remained stable. FDI values increased during the first year and then remained stable. Mild osteoarthritis was noted in one shoulder at last follow-up.

CONCLUSION

Final functional outcomes correlated significantly to FDI at baseline and last follow-up. Tension free tendon-to-bone suture is effective functionally and structurally at nine years follow-up provided the FDI at surgery is <or= 2 and the repair is intact after one year.

LEVEL OF EVIDENCE

Level 3; Retrospective cohort therapeutic study.

Neer Award 2007: Reversion of structural muscle changes caused by chronic rotator cuff tears using continuous musculotendinous traction. An experimental study in sheep

HYPOTHESIS

Chronic rotator cuff tears are associated with irreversible architectural muscle changes and a high rate of repair failure. The changes observed in man and their irreversibility with a single stage repair can be reproduced in sheep. It was the purpose of this experiment to test the hypothesis that slow, continuous elongation of a retracted musculotendinous unit allows reversal of the currently irreversible structural muscle changes.

MATERIALS AND METHODS

The infraspinatus tendon of 12 sheep was released using a greater tuberosity osteotomy and allowed to retract for 4 months. Then, a new device was mounted on the scapular spine and used to extend the infraspinatus muscuculotendinous unit transcutaneously by 1 mm per day. Thereafter, the tendon was repaired back to the greater tuberosity. We assessed the muscular architecture using magnetic resonance imaging, macroscopic dissection, histology, and electron microscopy. Fatty infiltration (in Hounsfield units 1/4 HU) and muscular cross-sectional area (in % of the control side) were monitored with computed tomography at tendon release, initiation of elongation, repair, and at sacrifice.

RESULTS

Sixteen weeks after tendon release, the mean tendon retraction was 29 +/- 6 mm (14% of original length, P = .008). In 8 sheep, elongation was achieved as planned (group I), but in 4, the elongation failed technically (group II). The mean traction time was 24 +/- 6 days with a mean traction distance of 19 +/- 4 mm. At sacrifice, the mean pennation angle in the infraspinatus of group I was not different from the control side (29.8 degrees +/-7.5 degrees vs. 30 degrees +/-6 degrees , P = .575). In group II, the pennation angle had increased from 30 degrees +/-6 degrees to 55 degrees +/-14 degrees (P = .035). There was no fatty infiltration at the time of tendon release. After retraction, there was a significant increase in fatty infiltration of the infraspinatus muscle and a decrease of its cross-sectional area to 57% of the contralateral side (P = .0001). During traction, the degree of fatty infiltration remained unchanged (36 HU to 38 HU, P = .381), and atrophy improved to a muscle square area of 78% of the contralateral side (P = .0001) in group I. In group II, an increase of fatty infiltration was measured from 36 HU to 28 HU; however, this increase was not significant (P = .144). Atrophy did not change in group II (57-55%, P = .946). At sacrifice, the remaining muscle mass was 64% in group I and 46% in group II (P = .019).

DISCUSSION

Our preliminary results document, that continuous elongation of a retracted, fatty infiltrated and atrophied musculotendinous unit is technically feasible.

CONCLUSION

In the sheep, continuous elongation can lead to restoration of normal muscle architecture, to partial reversal of muscle atrophy, and to arrest of the progression of fatty infiltration.

LEVEL OF EVIDENCE

Basic science level 2; Prospective comparative therapeutic study.