Cuff Muscle Fatty Degeneration Research Articles

Fatty Degeneration of the Rotator Cuff Muscles Improves in Shoulders with Successful Arthroscopic Rotator Cuff Repair: A Prospective Study Using Quantitative T2 Mapping Techniques, with 2-Year Follow-up.

There remain arguments regarding whether fatty degeneration of the rotator cuff muscles improves following rotator cuff repair. The purpose of this study was to prospectively investigate changes in fatty degeneration of the rotator cuff muscles, quantitatively measured on magnetic resonance imaging (MRI) with use of transverse relaxation time (T2) mapping techniques, and to assess the relationship between these changes and clinical outcomes. Patients were included if they were scheduled for arthroscopic rotator cuff repair using the suture-bridge technique between June 2014 and December 2015, underwent preoperative MRI including the T2 mapping sequence, and consented to participate in the study. Exclusion criteria consisted of trauma within 2 months before preoperative MRI, isolated subscapularis tears, patch augmentation, neuromuscular disease, and a follow-up duration of <2 years. MRI scans were acquired preoperatively and at 2 years postoperatively, and T2 values of the supraspinatus and infraspinatus muscles were measured, with smaller T2 values indicating less fat content. Shoulders were evaluated on the basis of active range of motion (ROM), Constant and University of California Los Angeles Shoulder Rating Scale scores, shoulder external rotation strength with the arm at the side, and rotator cuff integrity on postoperative MRI. A total of 103 patients (103 shoulders) with a mean age of 65 ± 9 years (range, 42 to 83 years) were included, of whom 52 were male and 51 were female. There were 13 partial, 18 small, 35 medium, 33 large, and 4 massive tears. Concomitant subscapularis tears were observed in 35 shoulders. Overall, ROM, clinical scores, and external rotation strength significantly improved postoperatively. Retears were found in 27 shoulders (26%). External rotation strength significantly improved postoperatively only in shoulders without a retear. Among shoulders without a retear, the postoperative T2 values of the supraspinatus and infraspinatus were significantly smaller than the preoperative values (p < 0.001 for both); however, no improvement was seen in shoulders with a retear. Shoulders with successful repair demonstrated significantly smaller T2 values postoperatively as well as significantly improved external rotation strength. Fatty degeneration of the cuff muscles can be reversed, at least in part, and muscle strength improves in shoulders with successful repair. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Longitudinal MR Quantification of the Fat Fraction within the Supraspinatus and Infraspinatus Muscles in Patients with Shoulder Pain

Knowing the natural history of fatty degeneration of rotator cuff muscles is important for estimating the risk and rate of progression to cuff tear arthropathy (CTA). The purpose of this study was to investigate the changes in rotator cuff muscle fatty degeneration over time quantitatively in patients treated conservatively for shoulder pain. Thirty patients with a baseline and follow-up shoulder MRI, including a 2-point Dixon sequence, which were performed at least 1 year apart, were included. We classified patients into 3 groups: "full-thickness tear" (n=7), "partial-thickness tear" (n=13), and "no-tear" (n=10) groups. The fat fraction in the supra- and infraspinatus muscles, and the rate of change in the fat fraction (ΔFfr) were calculated using the formula "fat fraction of follow-up MRI/fat fraction of initial MRI." We investigated the difference in ΔFfr among the 3 groups and the degree of progression to CTA. Statistically significant differences in ΔFfr within the supraspinatus and infraspinatus muscles were found among full-thickness, partial-thickness, and no-tear groups (2.54 vs 1.02 vs 0.75, p < 0.001 and 1.96 vs 1.07 vs 0.73, p=0.021, respectively). Overall, 71.4% of the full-thickness tear group showed progression of CTA, and 28.6% of the full-thickness tear group needed reverse shoulder arthroplasty within an average follow-up period of 34 months. MR quantification, together with the knowledge of change in fatty degeneration over time, may be useful for the management of patients with shoulder pain.

In vivo testing of an injectable matrix gel for the treatment of shoulder cuff muscle fatty degeneration

Extracellular matrix (ECM) gels have shown efficacy for the treatment of damaged tissues, most notably cardiac muscle. We hypothesized that the ECM gel prepared from skeletal muscle could be used as a treatment strategy for fatty shoulder cuff muscle degeneration. We conducted experiments to (1) evaluate host biocompatibility to ECM gel injection using a rat modeland (2) examine the effect of ECM gel injection on muscle recovery after delayed repair of a released supraspinatus (SSP) tendon using a rabbit model. The host biocompatibility to the ECM gel was characterized by a transient rise (first 2 weeks only) in several genes associated with macrophage infiltration, matrix deposition, and inflammatory cytokine production. By 8 weeks all genes had returned to baseline levels and no evidence of fibrosis or chronic inflammation was observed from histology. When gel injection was combined with SSP tendon repair, we observed a significant reduction (7%) in SSP muscle atrophy (24 + 3% reduction from uninjured) when compared with treatment with tendon repair only (31 + 7% reduction). Although fatty degeneration was elevated in both treatment groups, fat content trended lower (2%) in response to combined tendon repair and intramuscular ECM injection (4.1 + 2.1%) when compared with tendon repair only (6.1 + 2.9%). Transcriptome analysis revealed adipogenesis and osteoarthritis pathway activation in the repair only group. These key pathways were abrogated in response to treatment using combined repair plus gel. The findings suggest that ECM injection had a modest but positive effect on muscle mass, fatty degeneration, and key cellular signaling pathways.

Role of transplanted bone marrow cells in development of rotator cuff muscle fatty degeneration in mice

Rotator cuff muscle fatty degeneration after a chronic tendon tear is an irreversible pathologic change associated with poor clinical outcomes of tendon repair, and its exact pathogenesis remains unknown. We sought to investigate the role of transplanted bone marrow cells in the development of fatty degeneration, specifically in adipocyte accumulation, using a mouse model. Fourteen mice were divided into 2 bone marrow chimeric animal groups: bone marrow transplantation (BMT) group and reverse BMT group. For the BMT group, C57BL/6J wild-type mice underwent whole body irradiation followed by BMT into the retro-orbital sinus from green fluorescent protein (GFP)-transgenic donor mice. For the reverse BMT group, GFP-transgenic mice received BMT from C57BL/6J wild-type donor mice after irradiation. The supraspinatus tendon, infraspinatus tendon, and suprascapular nerve were surgically transected 3 weeks after transplantation. The rotator cuff muscles were harvested 13 weeks after transplantation for histologic analysis and GFP immunohistochemistry. On histologic examination, both groups showed substantial fatty degeneration, fibrosis, and atrophy of the cuff muscles. The BMT group showed no noticeable GFP immunostaining, whereas the reverse BMT group showed significantly stronger GFP staining in most adipocytes (P < .001). However, both groups also showed that a small number of adipocytes originated from transplanted bone marrow cells. A small number of myocytes showed a large cytoplasmic lipid vacuole resembling adipocytes. This study's findings suggest that most adipocytes in fatty degeneration of the rotator cuff muscles originate from sources other than bone marrow-derived stem cells, and there may be more than 1 source for the adipocytes.

Reliability of MR Quantification of Rotator Cuff Muscle Fatty Degeneration Using a 2-point Dixon Technique in Comparison with the Goutallier Classification: Validation Study by Multiple Readers

Presurgical assessment of fatty degeneration is important in the management of patients with rotator cuff tears. The Goutallier classification is widely accepted as a qualitative scoring system, although it is highly observer-dependent and has poor reproducibility. The objective of this study was to quantify fatty degeneration of the supraspinatus muscle using a 2-point Dixon technique in patients with rotator cuff tears by multiple readers, and to evaluate the reproducibility compared to Goutallier classification. Two hundred patients with rotator cuff tears who underwent magnetic resonance imaging (MRI), including 2-point Dixon sequence at 3.0-T, were selected retrospectively. Qualitative and quantitative analyses of fatty degeneration were performed by two radiologists and three orthopedic surgeons independently. The fat quantification was performed by measuring signal intensity values of in phase (S(In)) and fat image (S(Fat)), and calculating fat fraction as S(Fat)/S(In). The reproducibility of MR quantification was analyzed by the intra- and interclass correlation coefficients and Bland-Altman plots. The interobserver agreement of the Goutallier classification among five readers was moderate (k = 0.51), whereas the interclass correlation coefficient regarding fat fraction value quantified in 2-point Dixon sequence was excellent (0.893). The mean differences in fat fraction values from the individual segmentation results were from -0.072 to 0.081. Proposed fat fraction grading and Goutallier grading showed similar frequency and distribution in severity of rotator cuff tears. Fat quantification in the rotator cuff muscles using a 2-point Dixon technique at 3.0-T MRI is highly reproducible and clinically feasible in comparison to the qualitative evaluation using Goutallier classification.

Knocking-out matrix metalloproteinase-13 exacerbates rotator cuff muscle fatty infiltration.

Rotator cuff (RC) tears are common tendon injuries. Clinically, both muscle atrophy and fatty infiltration have generally been attributed to poor functional outcomes. Matrix metalloproteinase-13 plays a crucial role in extracellular matrix remodeling in many physiological and pathological processes. Nevertheless, its role in rotator cuff muscle atrophy and fatty infiltration remains unknown. The purpose of this study is to define the functional role of MMP-13 in rotator cuff muscle atrophy and fatty infiltration using a mouse RC tears model. Unilateral complete supraspinatus and infraspinatus tendon transection and suprascapular nerve transection was performed on nine of MMP-13 (-/-) knockout and nine of MMP-13 (+/+) wildtype mice at 3 months old. Mice were sacrificed 6 weeks after surgery. Supraspinatus (SS) and infraspinatus (IS) muscles were harvested for histology and gene expression analysis with RT-PCR. Six weeks after RC surgery, no significant difference in muscle atrophy and fibrosis between MMP-13 knockout and wild type mice was observed. However, there was a significant increase in the amount of fatty infiltration in MMP-13 knockout mice compared to the wild types. Muscles from MMP-13 knockout mice have significantly higher expression of fatty infiltration related genes. Results from this study suggest that MMP-13 plays a crucial role in rotator cuff muscle fatty degeneration. This novel finding suggests a new molecular mechanism that governs RC muscle FI and MMP-13 may serve as a target for therapeutics to treat muscle FI after RC tears.

Fatty degeneration and atrophy of the rotator cuff muscles after arthroscopic repair: does it improve, halt or deteriorate?

The purpose of this study was to evaluate the changes in fatty degeneration and atrophy of rotator cuff muscles after arthroscopic repair. We further assessed the factors affecting the functional outcomes and integrity of the rotator cuff. One hundred and two prospectively followed patients who underwent single-row arthroscopic repair for full-thickness rotator cuff tears between 2008 and 2010 in our institution were included. All patients underwent shoulder MRI examination before the arthroscopic repair and at the final follow-up at least 2 years after the surgical repair. Supraspinatus muscle atrophy was measured and evaluated according to the Thomazeau classification. The fatty degeneration of the cuff muscles was graded according to the Goutallier classification. Functional outcomes were assessed with the Constant shoulder score. The changes in fatty degeneration and atrophy were analyzed during the treatment period. Correlation coefficients (Pearson r) and stepwise, multiple linear regression were used to determine the relationship between the outcome variables (final Constant score and integrity of the cuff), and the predictor variables, age, sex, follow-up duration, initial muscle atrophy, final muscle atrophy, initial fatty degeneration and final fatty degeneration. Of the 102 patients reviewed, 87 patients responded and concluded the final clinical follow-up and MRI examination (85.2 % follow-up rate). There were 67 females and 20 males with a mean age of 62.5 ± 8.3 years (range 40-80 years). Mean follow-up period was 30.1 ± 5.8 months (range 24-43 months). At the final follow-up, the mean Constant shoulder score was 94.2 ± 8.2 (range 70-100), and 66 (75.9 %) patients rated as excellent, 14 (16.1 %) as good, and 7 (8.0 %) as fair. No patient had poor results. There was re-rupture in 26 (29.9 %) patients on final MRI examination. No patient had improvement in muscle atrophy and fatty degeneration. The atrophic changes between intact tendon and re-rupture cases were statistically similar (p = 0.300). The deterioration of fatty degeneration was significantly higher in the re-rupture group (p = 0.0001). The Constant shoulder score was significantly lower in patients with re-rupture (97.4 ± 5.0 versus 86.6 ± 9.3, p = 0.001).Multiple stepwise regression analysis showed that the Constant score was dependent on the final integrity of the tendon and the size of the tear (R (2) 0.420, p 0.001). The final integrity of the tendon was dependent on the age of the patient, initial and final fatty degeneration of the cuff muscles and the size of the tear (R (2) 0.669, p 0.001). Initial muscle atrophy and fatty degeneration did not improve even after a successful rotator cuff repair where the tendon anatomic integrity was maintained for at least 2 years. It may continue to deteriorate, and the best possibility was preservation of the preoperative status. On the other hand, in cases of re-rupture, fatty degeneration and atrophy continued to worsen significantly. The factors affecting tendon integrity were found to be the age of the patient, the size of the tear and the severity of preoperative fatty degeneration in the rotator cuff.

Paper 167: Vitamin D Level in the Serum Correlates with Fatty Degeneration of Cuff Muscles in Patients with Rotator Cuff Tear

To analyze the relationship between vitamin D (25(OH)D3) level in the serum and the fatty degeneration of the rotator cuff muscles in patients with rotator cuff disorders. Consecutive 366 patients with shoulder disorders underwent magnetic resonance arthrography, and the serum concentrations of vitamin D (25(OH)D3) and intact parathyroid hormone (iPTH) were simultaneously measured. Two hundred twenty eight patients were found to have full-thickness cuff tear (group I) and the remaining 138 were diagnosed as other than full-thickness tear (group II). Data on various factors [full-thickness cuff tear, gender, age, symptom duration, FD of cuff muscles, size and retraction of tear, and abduction and external rotation (ER) torque of the affected and unaffected shoulders as measured by isokinetic muscle performance test] were collected, and finally, stepwise linear regression analysis was performed to identify the factors which account for the FD of cuff muscles. In group I, a lower serum level of 25(OH)D3 was related with female, a higher FD of the supraspinatus (SSP) and infraspinatus (ISP), a higher serum iPTH, lower abduction torque in unaffected shoulder, and lower ER torque of both affected and unaffected shoulder. The Spearman correlation coefficients were −0.22 (p = 0.001), −0.22 (p = 0.001) and −0.10 (p = 0.146) between the serum 25(OH)D3 level and the FD of the SSP, ISP and subscapularis, respectively. Stepwise linear regression analysis revealed that retraction (p < 0.001), the ER torque of the unaffected shoulder (p = 0.001), and serum level of 25(OH)D3 (p = 0.031) were independent variables for the FD of the SSP. In group II, the lower level of serum 25(OH)D3 was related with female, a higher FD of the SSP and ISP, lower abduction and ER torque in the affected and unaffected shoulders. The current study demonstrated the serum vitamin D level has a significant negative correlation with the FD of the torn cuff muscles and a positive correlation with the isokinetic muscle torque. Future study may be needed to confirm the local concentration of vitamin D in the cuff muscles, and whether supplementation with vitamin D affects the functional and anatomical outcomes, and also the improvement of FD after rotator cuff repair.

The effect of tear size and nerve injury on rotator cuff muscle fatty degeneration in a rodent animal model

Irreversible muscle changes after rotator cuff tears is a well-known negative prognostic factor after shoulder surgery. Currently, little is known about the pathomechanism of fatty degeneration of the rotator cuff muscles after chronic cuff tears. The purposes of this study were to (1) develop a rodent animal model of chronic rotator cuff tears that can reproduce fatty degeneration of the cuff muscles seen clinically, (2) describe the effects of tear size and concomitant nerve injury on muscle degeneration, and (3) evaluate the changes in gene expression of relevant myogenic and adipogenic factors after rotator cuff tears using the animal model. Rotator cuff tears were created in rodents with and without transection of the suprascapular nerve. The supraspinatus and infraspinatus muscles were examined at 2, 8, and 16 weeks after injury for histologic evidence of fatty degeneration and expression of myogenic and adipogenic genes. Histologic analysis revealed adipocytes, intramuscular fat globules, and intramyocellular fat droplets in the tenotomized and neurotomized supraspinatus and infraspinatus muscles. Changes increased with time and were most severe in the muscles with combined tenotomy and neurotomy. Adipogenic and myogenic transcription factors and markers were upregulated in muscles treated with tenotomy or tenotomy combined with neurotomy compared with normal muscles. The rodent animal model described in this study produces fatty degeneration of the rotator cuff muscles similar to human muscles after chronic cuff tears. The severity of changes was associated with tear size and concomitant nerve injury.

Single-Row Versus Double-Row Arthroscopic Rotator Cuff Repair: A Prospective Randomized Clinical Study (SS-26)

The aim of this study was to compare the outcome of arthroscopic rotator cuff repair with single-row and double-row technique in a prospective randomized study. Eighty patients with a full-thickness rotator cuff tear underwent an arthroscopic repair with suture anchors. They were divided in two groups of 40 patients each, according to repair technique. Results were evaluated using the Constant score, and the DASH and Work-DASH questionnaires. At two-year follow-up, double-row repair showed slightly better clinical outcome than single-row repair, although the difference was not significant. To compare the clinical outcome of arthroscopic repair of full-thickness rotator cuff tears with single-row and double-row technique in a prospective randomized study. Eighty patients with a full-thickness tear of the posterior-superior rotator cuff underwent an arthroscopic repair with metal suture anchors. They were divided in two groups of 40 patients each, according to repair technique: single-row technique in group 1, and double-row technique in group 2. Exclusion criteria were: partial-thickness and irreparable cuff tears, subscapularis tears, labral pathology, os acromiale, degenerative arthritis of glenohumeral joint, symptomatic arthritis of acromioclavicular joint, rotator cuff arthropathy, previous surgery to the same shoulder, and workers' compensation claims. Results were evaluated using the Constant score normalized for age and gender, and the DASH and Work-DASH self-administered questionnaires. On analyzing the results at a two-year follow-up, we considered the following independent variables: age, gender, dominance, location, shape, and area of cuff tear, tendon retraction, fatty degeneration of cuff muscles, treatment of the biceps tendon, and rotator cuff repair technique. Univariate and multivariate statistical analysis were performed in order to find out variables that were independently associated to the outcome. Significance was set at p < .05. The null hypothesis was that differences between the two groups at the clinical outcome were not significant. Eight patients (10%) were lost at follow-up: 3 in group 1 and 5 in group 2. Comparison between groups did not show significant differences for each variable considered. Overall results for Constant score were 100.5 points in group 1 and 104.9 points in group 2; for DASH score were 15.4 points in group 1 and 12.7 points in group 2; for Work-DASH score were 16.0 points in group 1 and 9.6 points in group 2. Univariate and multivariate analysis showed that only age and gender significantly and independently influenced the outcome. Differences between groups 1 and 2 were not significant for each scoring system considered. Therefore, the null hypothesis was not rejected. At a short-term follow-up, arthroscopic repair of rotator cuff tears with double-row technique showed slightly better clinical outcome than single-row repair, although the difference was not significant.

Influence of cuff muscle fatty degeneration on anatomic and functional outcomes after simple suture of full-thickness tears

Two hundred twenty shoulders with a rotator cuff tear repaired by simple tendon-to-bone suture were analyzed to determine whether the severity of presurgical fatty degeneration had an influence on their anatomic and functional outcome. Fatty degeneration was evaluated for each muscle with the 5-stage grading system developed by Goutallier et al. A global fatty degeneration index (GFDI), the mean value of the 3 muscles, was calculated for each shoulder. Cuff integrity was evaluated by magnetic resonance imaging (116 cases) or computed arthrotomography scan (104 cases) at a mean 37 months' follow-up, and functional outcomes were evaluated with the Constant score. A recurrent tear was found in 79 cases (36%) and was more frequently encountered in posterosuperior tears. The likelihood of a recurrent tear was greater for tendons whose muscle showed fatty degeneration greater than grade 1. Fatty degeneration of the infraspinatus or subscapularis muscles had an influence on supraspinatus tendon outcome. A GFDI lower than 0.5 was necessary to yield less than 25% retears. The mean global Constant score was 75 at revision, significantly lower when a retear was present (70.5 versus 77.5). In the subgroup of watertight cuffs, it was lower when GFDI was higher. Fatty degeneration is an important prognostic factor in rotator cuff surgery.