Aging Aggravates the Progression of Muscle Degeneration After Rotator Cuff Tears in Mice.

PURPOSE: The purpose of this study was to evaluate the impact of aging on muscle degeneration after rotator cuff tear (RCT) in mice. METHODS: Young (12-week-old) and aged (50-to-60-week-old) female C57BL/6 mice were used (n = 29 for each group). The rotator cuff was transected, and the proximal humerus was removed to induce degeneration of the rotator cuff muscles. The mice were euthanized 4 and 12 weeks after the procedure (referred to as RCT-4wk mice and RCT-12wk mice, respectively) and compared with the sham-treated mice. The supraspinatus muscles were collected for histology, Western blot analysis, and gene expression analyses. RESULTS: There was a significant increase in fat tissue in aged RCT-4wk mice (P = .001) and aged RCT-12wk mice (P < .001) compared with sham-treated aged mice, and aged RCT-12wk mice had a significantly increased fat area ratio compared with aged RCT-4wk mice (P < .001). The fat area was significantly larger in both the aged RCT-4wk (P = .002) and RCT-12wk mice (P < .001) than in the corresponding young mice. Muscular fibrosis was significantly increased in aged RCT-12wk mice compared with aged sham-treated mice (P = .005) and young RCT-12wk mice (P = .016). There were also significant increases in the expression of perilipin and transcripts of adipogenic and fibrogenic differentiation markers in aged RCT mice compared with young RCT mice. CONCLUSION: The present results show that aging is critically involved in the pathology of muscular fatty infiltration and fibrosis after RCT, and muscular degeneration progresses over time in aged mice. CLINICAL RELEVANCE: Aging promotes the progression of muscle degeneration in a mouse RCT model. Furthermore, this study shows that muscle degeneration occurs in aged mice even without denervation and that the model described in the present study is a useful tool for studying the pathology of muscle degeneration.

Reproducibility of the modified Neer classification defining displacement with respect to the humeral head fragment for proximal humeral fractures.

BACKGROUND: Although the Neer classification is widely used for the assessment of proximal humeral fractures, its reproducibility has been challenged. The purpose of this study was to evaluate the reproducibility of the conventional Neer classification and a modified classification that defined fracture displacement with respect to the humeral head fragment. METHODS: The fracture patterns in 80 cases of proximal humeral fractures were independently assessed by 6 observers. The cases were grouped according to the conventional Neer classification using radiographs followed by computed tomography (CT) scans by each examiner twice with a 1-month interval. The fractures were then classified with the modified Neer classification, which defined displacement of the fragment as separation of more than 1 cm or angulation of more than 45° from the humeral head fragment, twice with a 1-month interval. Kappa coefficients of the conventional and modified Neer classifications were compared. RESULTS: The modified classification showed significantly higher intra-observer agreement than the conventional classification, both for radiographs (P = .028) and for CT scans (P = .043). Intra-observer agreement was also significantly higher for the modified classification than for the conventional classification, both for radiographs (P = .001) and for CT scans (P < .001). CONCLUSIONS: The present study showed that agreement for the Neer classification could be improved when fracture displacement was defined as separation or angulation from the humeral head. Considering vascularity to the humeral head, furthermore, the modified method might be more helpful for predicting patients' prognosis than the conventional Neer classification.

Cerclage Wiring Fixation for the Treatment of Long Oblique Fractures of the Distal Clavicle: A Report of 2 Cases.

CASE: A 49-year-old man and a 37-year-old man with long oblique fractures of the distal clavicle were successfully treated with cerclage wiring fixation without detachment of the trapezius and deltoid muscles and exposure of the fracture site. CONCLUSIONS: Long oblique fractures with the acromioclavicular and coracoclavicular ligaments being intact and attached to the distal fragment are relatively rare among distal clavicle fractures. Cerclage wiring fixation is a viable treatment option for the fixation of long oblique fractures of the distal clavicle, with good clinical results and rapid recovery of shoulder function.