The remaining teres minor and subscapularis may contribute to preventing superior migration of the humeral head and progression of osteoarthritic change in rotator cuff tears.

Background: Superior migration of the humeral head is common in large and massive rotator cuff tears (RCTs). Humeral heads migrate superiorly according to an increase in the RCT size; however, the relevance of the remaining cuff has not been elucidated. This study investigated the relation between superior migration of the humeral head and the remaining rotator cuff, especially the teres minor (TM) and subscapularis (SSC), in RCTs involving tears and atrophy of the infraspinatus (ISP). Methods: Plain anteroposterior radiographic and magnetic resonance imaging examinations were performed on 1345 patients between January 2013 and March 2018. A total of 188 shoulders with tears of the supraspinatus and ISP with atrophic ISP were evaluated. Gradings of superior migration of the humeral head and osteoarthritic change were evaluated using the acromiohumeral interval, Oizumi classification, and Hamada classification on plain anteroposterior radiographs. The cross-sectional area of the remaining rotator cuff muscles was evaluated using oblique sagittal magnetic resonance imaging. The TM was classified as hypertrophic (H) and normal and atrophic (NA). The SSC was classified as nonatrophic (N) and atrophic (A). All shoulders were classified as groups A (H-N), B (NA-N), C (H-A), and D (NA-A). Age- and sex-matched patients with no cuff tears were also enrolled (control). Results: The acromiohumeral intervals of the control group and groups A-D were 11.4 ± 2.4, 9.5 ± 3.8, 7.8 ± 4.1, 7.2 ± 4.0, and 5.4 ± 3.5 mm (84, 74, 64, 21, and 29 shoulders, respectively), with significant differences between groups A and D (P < .001) and groups B and D (P = .016). Grade 3 of the Oizumi classification and grades 3, 4, and 5 of the Hamada classification were significantly higher in group D than in others (P < .001). Conclusion: The group showing hypertrophic TM and nonatrophic SSC prevented significantly migration of the humeral head and cuff tear osteoarthritis compared to the group showing atrophic TM and SSC in posterosuperior RCTs. The findings indicate that the remaining TM and SSC may prevent superior migration of the humeral head and progression of osteoarthritic change in RCTs. In treating patients with large and massive posterosuperior RCTs, the status of the remaining TM and SSC muscles should be assessed.

Hypertrophic teres minor restores shoulder strength and range of external rotation in posterosuperior rotator cuff tears.

BACKGROUND: In posterosuperior rotator cuff tears (PS-RCT), the progression of infraspinatus (ISP) muscle atrophy seems to induce compensatory hypertrophy of the teres minor (TM) muscles. However, the effect of these changes on shoulder strength and range of external rotation (ER) remains unclear. This study determined the strength and range of ER in patients with PS-RCT with atrophic ISP and hypertrophic TM and compared this with patients with PS-RCT and normal or deficient TM. METHODS: We investigated 35 patients with PS-RCT and atrophic ISP. TM muscles were classified as hypertrophic (type A) in 17, normal (type B) in 10, or deficient (type C) in 8. The strength ratio of the affected shoulder to the healthy contralateral shoulder was calculated, and the active range of motion was measured for both shoulders. RESULTS: The strength ratios of ER in types A, B, and C were 60%, 33%, and 7% (P < .01) with the patient's arm at the side and were 60%, 35%, and 5% (P < .001) at 90° abduction, respectively. The average ranges of ER in types A, B, and C were 22.6°, 15.0°, and -12.5° (P < .001) with the patient's arm at the side and were 71.6°, 44.5°, and 21.9° at 90° abduction (P < .01), respectively. The differences between shoulder types in other measures of strength or ER range were not significant. CONCLUSIONS: In patients with PS-RCT and atrophic ISP, shoulders with compensatory hypertrophy of the TM had greater strength and range of ER than shoulders with normal or atrophic TM.

Hypertrophic changes of the teres minor muscle in rotator cuff tears: quantitative evaluation by magnetic resonance imaging.

BACKGROUND: Few reports have assessed the teres minor (TM) muscle in rotator cuff tears. This study aimed to quantitatively analyze the morphologic changes of the TM muscle in patients with or without rotator cuff tears by magnetic resonance imaging (MRI). METHODS: This retrospective study consisted of 279 subjects classified on the basis of interpretations of conventional MRI observations into 6 groups: no cuff tear; partial-thickness supraspinatus (SSP) tear; full-thickness SSP tear; SSP and subscapularis tears; SSP and infraspinatus (ISP) tears; and SSP, ISP, and subscapularis tears. With use of ImageJ software (National Institutes of Health, Bethesda, MD, USA) for oblique sagittal MRI, we measured the areas of ISP, TM, and anatomic external rotation (ISP + TM) muscles on the most lateral side in which the scapular spine was in contact with the scapular body. The occupational ratios of the TM muscle area to the anatomic external rotation muscle area were calculated. Ratios above the maximum of the 95% confidence intervals of the occupational ratio in the no-tear group were defined as hypertrophy of the TM muscle. RESULTS: Occupational ratios of the TM muscle in the no-tear group followed a normal distribution, and ratios >0.288 were defined as hypertrophic. Hypertrophic changes of the TM muscle were confirmed in rotator cuff tears involving the ISP tendon. A negative correlation was found between the occupational ratios of TM and ISP (P < .001). CONCLUSION: The TM muscle appeared hypertrophic in rotator cuff tears involving the ISP, and the progression of ISP muscle atrophy seemed to induce the development of this compensatory hypertrophy.

New equations for predicting postoperative risk in patients with hip fracture.

UNLABELLED: Predicting the postoperative course of patients with hip fractures would be helpful for surgical planning and risk management. We therefore established equations to predict the morbidity and mortality rates in candidates for hip fracture surgery using the Estimation of Physiologic Ability and Surgical Stress (E-PASS) risk-scoring system. First we evaluated the correlation between the E-PASS scores and postoperative morbidity and mortality rates in all 722 patients surgically treated for hip fractures during the study period (Group A). Next we established equations to predict morbidity and mortality rates. We then applied these equations to all 633 patients with hip fractures treated at seven other hospitals (Group B) and compared the predicted and actual morbidity and mortality rates to assess the predictive ability of the E-PASS and Physiological and Operative Severity Score for the enUmeration of Mortality and Morbidity (POSSUM) systems. The ratio of actual to predicted morbidity and mortality rates was closer to 1.0 with the E-PASS than the POSSUM system. Our data suggest the E-PASS scoring system is useful for defining postoperative risk and its underlying algorithm accurately predicts morbidity and mortality rates in patients with hip fractures before surgery. This information then can be used to manage their condition and potentially improve treatment outcomes. LEVEL OF EVIDENCE: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

The effects of fibroblast growth factor-2 on rotator cuff reconstruction with acellular dermal matrix grafts.

PURPOSE: Our purpose was to determine whether the local application of fibroblast growth factor (FGF) 2 accelerates regeneration and remodeling of rotator cuff tendon defects reconstructed with acellular dermal matrix (ADM) grafts in rats. METHODS: Thirty adult male Sprague-Dawley rats were divided into equal groups undergoing FGF-treated and FGF-untreated repairs. All rats underwent placement of an ADM graft for the supraspinatus defect (3 x 5 mm). FGF-2 (100 microg/kg) in a fibrin sealant was applied to both shoulders in the FGF-treated group, whereas only fibrin sealant was applied in untreated group. At 2, 6, and 12 weeks after surgery, 5 rats (10 shoulders) in each group were sacrificed for histologic analysis (3 shoulders) and biomechanical testing (7 shoulders). The controls were 5 unoperated rats (3 histologic and 7 biomechanical control specimens). RESULTS: Unoperated control tendons inserted into the bone by direct insertion; there was a zone of fibrocartilage between the tendon and bone. At 2 weeks, the FGF-treated group had tendon maturing scores similar to those in the untreated group (P > .05). At 6 and 12 weeks, the FGF-treated group had significantly higher scores (P < .05). At 2 weeks, specimens in both the treated and untreated groups exhibited similar strength; the ultimate tensile failure load was 6.0 +/- 4.0 N and 5.8 +/- 2.0 N, respectively (P > .05). At 6 weeks, the FGF-treated specimens were stronger, with an ultimate tensile failure load of 10.2 +/- 3.1 N compared with 7.2 +/- 2.2 N in the untreated group (P = .02). At 12 weeks, the FGF-treated specimens were stronger, with an ultimate tensile failure load of 15.9 +/- 1.6 N compared with 13.2 +/- 2.0 N in the untreated group (P = .0072), and there were no significant differences in strength compared with the controls (17.8 +/- 2.6 N) (P > .05). CONCLUSIONS: The remodeling of ADM grafts placed in rat rotator cuff tendon defects was accelerated by the local administration of FGF-2. CLINICAL RELEVANCE: The application of FGF-2 may result in improved histologic characteristics and biomechanical strength in ADM graft constructs in humans.

The effect of a local application of fibroblast growth factor-2 on tendon-to-bone remodeling in rats with acute injury and repair of the supraspinatus tendon.

METHODS: We investigated the effect of application of fibroblast growth factor (FGF)-2 on the tendon-to-bone remodeling of repaired supraspinatus tendon in rats subjected to bilateral detachment. FGF-2 (100 mg/kg) in a fibrin sealant or sealant alone was applied on the right and left shoulders, respectively. Twelve animals each at 2, 4, and 6 weeks after surgery were sacrificed for histological analysis (n = 5) and biomechanical Q1 testing (n = 7). RESULTS: Histologically, at 2 weeks, FGF-treated specimens had significantly higher tendon-to-bone insertion maturing scores then untreated specimens (P < .002). At 4 and 6 weeks, the scores of FGF-treated and untreated specimens were similar (P > .05). Biomechanically, FGF-treated specimens were stronger at 2 weeks (P = .001); at 4 and 6 weeks, both specimens exhibited similar strength (P > .05). CONCLUSIONS: The initial tendon-to-bone remodeling was accelerated by a local application of FGF-2. This may represent a clinically important improvement in rotator cuff repair.

Reconstruction of large rotator-cuff tears with acellular dermal matrix grafts in rats.

HYPOTHESIS: With the acellular dermal matrix (ADM), it may be possible to bridge large rotator cuff tears and induce tendon regeneration. MATERIALS AND METHODS: A 3 x 5 mm defect of the rotator cuff was created on both shoulders of adult male Sprague-Dawley rats. The graft group (n = 15) underwent reconstruction of the rotator cuff defect with an ADM patch graft; in the defect group (n = 15) no repair was performed. We sacrificed 5 rats from each group at 2, 6, and 12 weeks after surgery and harvested both shoulders; 3 specimens were subjected to histological analysis and the other 7 specimens were used for biomechanical testing. The controls were 5 unoperated rats; they were sacrificed to obtain 3 histologic and 7 biomechanical control shoulder specimens. RESULTS: At each time points, the graft group had significantly higher modified tendon maturing scores than the defect group (p < 0.002); specimens from the graft group demonstrated a greater mean ultimate force to failure than those from the defect group (p < 0.05). Within 12 weeks, the ADM graft was histologically incorporated into a structure resembling control specimen; the mean ultimate force to failure in control was significantly greater than in specimens from both groups (p < 0.01). DISCUSSION: Although the defect was restored in the defect group, histologically and biomechanically specimens from the defect group were inferior to the graft group. CONCLUSION: ADM grafts were useful as a scaffold in the reconstruction of large rotator cuff defects in rats. LEVEL OF EVIDENCE: Basic science study.

Acute changes in the axonal cytoskeleton after mild stretching of the rat brachial plexus.

We have developed an animal model to investigate acute changes in the axonal cytoskeleton caused by a mild stretching of the peripheral nerve in the upper limbs of rats. Rat forelimbs were continuously stretched at 2 N for 1 h. Thereafter, a part of the brachial plexus and median nerve were harvested and processed for electron microscopic analysis. The total number of microtubules in the brachial plexus decreased to 55% of that of the control animals (p<0.05) without change in the number of neurofilaments. No significant changes in microtubules or neurofilaments were observed in the median nerve. By Western blotting analysis, the amount of tau protein in the stretch group significantly decreased in the brachial plexus but not in the median nerve. However, no significant changes in the amount of tubulin protein were observed in either the brachial plexus or median nerve. These results suggest that the microtubules were depolymerized by stretching of the brachial plexus and that the depolymerization may have been mediated by the decrease in the tau protein.