Histologic Differences in Human Rotator Cuff Muscle Based on Tear Characteristics

Comparison of functional outcomes following early and delayed arthroscopic repair for traumatic and non-traumatic rotator cuff injuries

BACKGROUND

The effects of the timing of surgical repair on the outcomes of traumatic and non-traumatic rotator cuff injuries (RCI) remain elusive. Thus, this study aimed to compare differences in outcomes following the repair of traumatic and non-traumatic RCI at varying time points.

METHODS

The study population comprised 87 patients with traumatic and non-traumatic RCI who underwent arthroscopic rotator cuff repair and were followed up for a minimum of 6 months. Next, the trauma and the non-trauma groups were stratified into subgroups according to the time of injury (early repair: occurring within 3 months; delayed repair: occurring after 3 months). Measurements before and after surgical interventions were compared to evaluate the effect of the duration of RCI on the functional status of patients in the trauma and non-trauma groups. Primary evaluation indices included the Visual Analog Scale (VAS) pain score, American Shoulder and Elbow Surgeons (ASES) score, Constant shoulder function score, and the University of California, Los Angeles (UCLA) shoulder score. Secondary evaluation indices consisted of shoulder range of motion (ROM), postoperative rotator cuff retear rate, and incidence of joint stiffness.

RESULTS

Among the 40 patients in the trauma group, 22 underwent early repair, whereas the remaining 18 underwent delayed repair. In the non-trauma group consisting of 47 patients, 18 underwent early repair, whereas the remaining 29 underwent delayed repair. The minimum clinical follow-up time was 6 months, with an average follow-up time of 10.2 months. During postoperative follow-up, 1 and 6 patients who underwent early and delayed repair experienced re-tear in the trauma group, respectively. Contrastingly, 3 and 8 patients who underwent early and delayed repair presented with re-tear in the non-trauma group, respectively.

CONCLUSION

Early repair of traumatic RCI yielded superior outcomes, including improved range of motion, lower pain symptoms, and lower risk of postoperative re-tears compared to delayed repair. Additionally, non-surgical treatment is recommended as the preferred approach for patients with non-traumatic RCI.

Risk factors for intracellular fatty accumulation in rotator cuff muscle: a histologic analysis

BACKGROUND

Fatty accumulation in rotator cuff muscles has been associated with shoulder dysfunction, risk of repair failure, and poor postoperative outcomes. This study sought to assess risk factors associated with true fatty accumulation based on histologic analysis and determine whether preoperative function directly correlated with this fatty rotator cuff accumulation.

METHODS

Supraspinatus muscle biopsy specimens obtained prospectively from patients undergoing arthroscopic rotator cuff repair were stained with LipidTOX to quantify lipid accumulation. Two-step cluster analysis with Goutallier classification was used to define the fatty and non-fatty rotator cuff groups. We further performed a receiver operating characteristic curve analysis to confirm the group cutoff values.

RESULTS

In total, 51 patients (aged 60.1 ± 10.5 years) were included. There were 19 high-grade partial tears, 10 small tears, 7 medium tears, 10 large tears, and 5 massive tears. Both cluster and receiver operating characteristic curve analyses yielded a cutoff value of 30% LipidTOX/4',6-diamidino-2-phenylindole (DAPI) separating the fatty vs. non-fatty groups. In the univariate analysis, patients with fatty rotator cuffs were aged 63.2 years on average compared with 59.7 years in the non-fatty group (P = .038). Female patients made up 57.1% of the fatty cohort, which was statistically higher than the non-fatty group (P = .042). Massive and large tears were more likely to occur in the fatty group (P = .005). In the multivariate analysis, full tendon tears had the largest predictive status of falling into the fatty group (odds ratio, 15.4; P = .008), followed by female sex (odds ratio, 4.9; P = .036). Patients in the fatty group had significantly higher American Shoulder and Elbow Surgeons scores (P = .048) and lower visual analog scale scores (P = .002).

DISCUSSION AND CONCLUSION

This prospective histologic assessment revealed that full-thickness rotator cuff tears and female sex were the largest risk factors for intracellular lipid accumulation. Although tear size correlated with fatty accumulation, the sex disparity is a noteworthy finding that warrants further research.

Cell Sheet Technology: An Emerging Approach for Tendon and Ligament Tissue Engineering

Tendon and ligament injuries account for a substantial proportion of disorders in the musculoskeletal system. While non-operative and operative treatment strategies have advanced, the restoration of native tendon and ligament structures after injury is still challenging due to its innate limited regenerative ability. Cell sheet technology is an innovative tool for tissue fabrication and cell transplantation in regenerative medicine. In this review, we first summarize different harvesting procedures and advantages of cell sheet technology, which preserves intact cell-to-cell connections and extracellular matrix. We then describe the recent progress of cell sheet technology from preclinical studies, focusing on the application of stem cell-derived sheets in treating tendon and ligament injuries, as well as highlighting its effects on mitigating inflammation and promoting tendon/graft-bone interface healing. Finally, we discuss several prerequisites for future clinical translation including the selection of appropriate cell source, optimization of preparation process, establishment of suitable animal model, and the fabrication of vascularized complex tissue. We believe this review could potentially provoke new ideas and drive the development of more functional biomimetic tissues using cell sheet technology to meet the needs of clinical patients.

Anatomic characteristics of shoulder based on MRI accurately predict incomplete rotator cuff injuries in patients: relevance for predictive, preventive, and personalized healthcare strategies

Background and PPPM-related working hypothesis

In the diagnosis of incomplete rotator cuff injuries (IRCI), magnetic resonance imaging (MRI) and ultrasound examination often have false-positive and false-negative results, while arthroscopy is expensive, invasive, and complex. From the strategy of predictive, preventive, and personalized medicine (PPPM), shoulder anatomical characteristics based on MRI have been demonstrated to accurately predict IRCI and their clinical applicability for personalized prediction of IRCI.

Aims

This study aimed to develop and validate a nomogram based on anatomical features of the shoulder on MRI to identify IRCI for PPPM healthcare strategies.

Methods

The medical information of 257 patients undergoing preoperative MRI examination was retrospectively reviewed and served as the primary cohort. Partial-thickness rotator cuff tears (RCTs) and tendinopathy observed under arthroscopy were considered IRCI. Using logistic regression analyses and least absolute shrinkage and selection operator (LASSO), IRCI was identified among various preoperative factors containing shoulder MRI and clinical features. A nomogram was constructed and subjected to internal and external validations (80 patients).

Results

The following eight independent risk factors for IRCI were identified:AgeThe left injured sidesThe Goutallier classification of supraspinatus in oblique coronal positionThe Goutallier classification of supraspinatus in the axial positionAcromial thicknessAcromiohumeral distanceCoracohumeral distanceAbnormal acromioclavicular joint signalsThe nomogram accurately predicted IRCI in the development (C-index, 0.932 (95% CI, 0.891, 0.973)) and validation (C-index, 0.955 (95% CI, 0.918, 0.992)) cohorts. The calibration curve was consistent between the predicted IRCI probability and the actual IRCI ratio of the nomogram. The decision curve analysis and clinical impact curves demonstrated that the model had high clinical applicability.

Conclusions

Eight independent factors that accurately predicted IRCI were determined using MRI anatomical findings. These personalized factors can prevent unnecessary diagnostic interventions (e.g., arthroscopy) and can assist surgeons in implementing individualized clinical decisions in medical practice, thus addressing the goals of PPPM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-023-00333-5.

Association Between Supraspinatus Tendon Retraction, Histologic Myofiber Size, and Supraspinatus Muscle Atrophy on MRI

BACKGROUND

Atrophy of the rotator cuff is a negative prognostic indicator after rotator cuff repair. Although full-thickness rotator cuff tears accompanied by tendon retraction are commonly associated with decreased muscle cross-sectional area (CSA) on magnetic resonance imaging (MRI), it is unclear whether this is accompanied by histologic atrophy of rotator cuff myofibers.

PURPOSE

To evaluate the effect of supraspinatus tendon retraction and myofiber size on supraspinatus atrophy on MRI.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Supraspinatus muscle biopsy specimens were obtained from consecutive patients undergoing arthroscopic shoulder surgery. Rotator cuff tears were classified according to size. Preoperative MRI was used to measure tendon retraction and CSA of the supraspinatus muscle in the Y-shaped view. The occupation ratio of the supraspinatus was calculated by dividing the supraspinatus CSA by the supraspinatus fossa CSA. Muscle biopsy specimens were examined using laminin to quantify myofiber CSA. The association between supraspinatus tear size and measures of histologic and MRI muscle atrophy were compared using standard statistical tests. Multivariable logistic regression analysis was used to identify independent predictors of muscle atrophy on MRI.

RESULTS

A total of 38 patients were included: 8 with no tear, 14 with a partial-thickness tear, and 16 with a full-thickness tear. Increasing tear size was associated with greater distance of tendon retraction (P < .001), smaller mean histologic myofiber size (P = .004), lower mean supraspinatus CSA on MRI (P < .001), and lower occupation ratio: 0.73 (control), 0.66 (partial tear), 0.53 (small to medium full-thickness tear), and 0.38 (large to massive full-thickness) (P < .001). On Pearson correlation analysis, tendon retraction demonstrated strong correlation with occupation ratio (-0.725; P < .001) and weak correlation with myofiber size (-0.437; P = .006), while occupation ratio showed moderate correlation with myofiber size (0.593; P < .001). Multivariable linear regression analysis demonstrated that increasing tendon retraction (P < .001), age (P = .034), and smaller histologic myofiber CSA (P = .047) were independently associated with greater supraspinatus atrophy on MRI.

CONCLUSION

Supraspinatus muscle atrophy appreciated on MRI is independently associated with patient age, tendon retraction, and atrophy of the supraspinatus myofibers at the histologic level.