Delayed tendon reattachment does not reverse atrophy and fat accumulation of the supraspinatus--an experimental study in rabbits.

Muscle atrophy and fat accumulation occur after rotator cuff tearing. Whether these changes are reversible after a successful repair is still unknown. Imaging allows only a semi-quantitative assessment of muscle atrophy and fat deposition. As only experimental studies permit a quantification of both, a unilateral detachment and wrapping in a polyvinylidine fluoride membrane of the supraspinatus was done in 22 rabbits. After 12 weeks, the polyvinylidine fluoride membrane was removed in 10 rabbits and the tendon inserted into a bony trough. The opposite shoulder served as control. All rabbits were killed at 24 weeks. Accumulation of fat on the muscle surface as well as between the muscle fascicles and occasionally in the sarcoplasm was increased in both experimental groups when compared to controls (non-reattached 12.8%, reattached 23.5% vs controls 5.4%; all p < 0.005). The muscle atrophy was significant (non-reattached 9.2 ml, reattached 9.1 ml vs controls 10.7 ml; both p < 0.005). Neither atrophy nor fat accumulation were reversed by surgical reattachment of the supraspinatus tendon. On the contrary, the fat accumulation was higher in the reattached group (p < 0.005). The trauma of reattachment, the delay between detachment and reattachment or an insufficient duration of recovery may have contributed to both, the lack of reversibility of supraspinatus atrophy and fat accumulation.     

Muscle tissue atrophy, extramuscular and intramuscular fat accumulation, and fat gradient after delayed repair of the supraspinatus tendon: A comparative study in the rabbit

To investigate the atrophy of supraspinatus (SSP) muscle tissue and accumulation of extramuscular fat (e‐fat) and intramuscular fat (i‐fat) after delayed repair of the SSP tendon, and to correlate CT findings with histology. One SSP tendon of 36 rabbits was transected, then repaired in groups of 12 at 4, 8, or 12 weeks and then followed for 12 weeks. Thirty‐six normal shoulders served as controls. We compared the SSP muscle, e‐fat weights and volumes, muscle tissue and i‐fat areas on histology, e‐fat and attenuation values on CT between the experimental and control shoulders. CT‐to‐histology correlations were run. SSP muscle tissue atrophy, e‐fat and i‐fat accumulation were present after tendon repair delayed by 4, 8, or 12 weeks (all p < 0.05). Both e‐fat and i‐fat accumulation presented increasing proximal‐to‐distal gradients (both p < 0.05). CT depicted the muscle tissue atrophy, e‐fat and i‐fat accumulation, and increasing proximal‐to‐distal gradients (all p < 0.05). We found strong CT‐to‐histology correlations (p < 0.05). SSP muscles showed tissue atrophy, e‐fat and i‐fat accumulation after successful SSP tendon repairs delayed by 4, 8, or 12 weeks. Subtracting i‐fat from the muscle area determined the SSP muscle tissue atrophy. Increasing proximal‐to‐distal fat gradients were diagnostic if not pathognomonic of an initial SSP tendon disruption. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:781–786, 2012     

Effect of timing of surgical SSP tendon repair on muscle alterations

To investigate the impacts of delayed repairs of a supraspinatus tendon tear on the supraspinatus muscle, we used an animal model data from two previously published studies in which one supraspinatus (SSP) tendon was detached. In one cohort, the rabbits were killed in groups of 10 at 4, 8, and 12 weeks. In the other cohort, a repair was done at these time points, 12 rabbits each, and the animals killed were 12 weeks later. SSP fossa volume (Muscle belly plus extramuscular fat [e‐fat] volume), percentage of intramuscular fat (i‐fat), and muscle tissue volume (muscle belly volume minus i‐fat), as well as CT determination of e‐fat and i‐fat of both cohorts, were compared. Fossa volume increased (p < 0.05). Muscle belly and muscle tissue volumes did not increase after repair (p > 0.05), but early repair prevented further volume losses, a fact not seen after 8 and 12 weeks delay of repair. No reversal of e‐fat or of i‐fat occurred, in fact i‐fat almost doubled after 4 weeks delay of repair (p < 0.05). CT studies confirmed the fat results. We conclude that early repair prevented loss of muscle belly and muscle tissue volumes, but that it has no positive influence on fat accumulation. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1430–1435, 2014.     

Effects of botulinum toxin‐induced paralysis on postnatal development of the supraspinatus muscle

The mechanical environment plays an important role in musculoskeletal tissue development. The present study characterized changes in supraspinatus muscle due to removal of mechanical cues during postnatal development. An intramuscular injection of botulinum toxin type A (BTX) was used to induce and maintain paralysis in the left shoulders of mice since birth while the right shoulders received saline and served as contralateral controls. A separate group of animals was allowed to develop normally without any injections. Muscles were examined postnatally at various time points. The maximum isometric tetanic force generated by the muscle was significantly reduced in the BTX group compared to saline and normal groups. The paralyzed muscles were smaller and showed significant muscle atrophy and fat accumulation on histologic evaluation. Myogenic genes myogenin, myoD1, myf5, myf6, and fast type II myosin heavy chain (MHC) isoform were significantly upregulated while slow type I MHC isoform was significantly downregulated in the BTX group. Adipogenic genes C/EBPα, PPARγ2, leptin, and lipoprotein lipase were significantly upregulated in the BTX group. Results indicate that reduced muscle loading secondary to BTX‐induced paralysis leads to fat accumulation and muscle degeneration in the developing muscle. Understanding the molecular and compositional changes in developing supraspinatus muscles may be useful for identifying and addressing the pathological changes that occur in shoulder injuries such as neonatal brachial plexus palsy. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:281–288, 2011     

Asymmetric atrophy of the supraspinatus muscle following tendon tear.

Muscle atrophy is a known consequence of muscle disuse, muscle denervation and tendon tear. Whereas after nerve injury muscle atrophies in the denervated area, the distribution of muscle atrophy following tear of its tendon is not known. Standardized MRI scans of 64 consecutive, painful shoulders were evaluated for supraspinatus tendon tearing, myotendinous retraction, supraspinatus muscle atrophy, fatty infiltration, ratio of the scapular (deep) and fascial (superficial) muscle area ("symmetry") and position of the central tendon within the supraspinatus fossa. There were thirteen shoulders with no and eleven shoulders with partial thickness supraspinatus tendon tears. In the forty cases with full thickness tendon tear, there was significant muscle atrophy and fatty infiltration. Atrophy of the fascial muscle portion was 43%, on the bony side it was 9% (p<0.005). The position of the central tendon within the supraspinatus fossa, was unaltered. Muscular changes following tendon tear occur highly asymmetrically: the muscle portion originating from the fascia primarily atrophies, the portion originating from the scapula primarily undergoes fatty infiltration. Muscular changes are not simply a consequence of muscle disuse, but dependent on architectural changes in the muscle.     

Skeletal muscle atrophy and increased intramuscular fat after incomplete spinal cord injury

STUDY DESIGN: Cross-sectional and longitudinal design. OBJECTIVES: (1) To quantify skeletal muscle cross-sectional area (CSA) after correcting for intramuscular fat (IMF) in thigh muscle groups 6 weeks after incomplete spinal cord injury (SCI), (2) to monitor the changes in muscle CSA and IMF after 3 months from the initial measurement. SETTING: Academic institution Athens, GA, USA. METHODS: Six incomplete SCI patients (28+/-4 years, 178+/-5 cm and 78+/-6 kg, mean+/-SE, C7 to L3, American Spinal Injury Association B or C) were tested at 5+/-1 weeks and 3 months after the initial measurement. T1-weighted magnetic resonance images were taken of both thighs. Six able-bodied (AB) controls were matched in age, sex, height and weight (29+/-4 years, four male and two female subjects, 179+/-5 cm and 77+/-6 kg). RESULTS: At 6 weeks post-injury, muscle CSA was 82+/-4 cm(2) in incomplete SCI and 123+/-21 cm(2) in AB controls (P=0.04). IMF CSA was 5.2+/-1.3 and 2.3+/-0.6 cm(2) in incomplete SCI and AB controls, respectively (P=0.03). Relative IMF was three-fold higher (P=0.03) in the SCI group versus AB controls (5.8+/-1.4 versus 2.0+/-0.6%). After 3 months, IMF increased 26% in the SCI group compared to the initial measurement (P=0.02). CONCLUSIONS: Skeletal muscle atrophy is associated with greater IMF accumulation in SCI group 6 weeks post-injury compared to AB controls. Moreover, IMF continues to increase over time in incomplete SCI.     

A rat model of massive rotator cuff tears

Rotator cuff tears (RCTs) are the most common tendon injury seen in orthopedic patients. Massive RCT does not heal spontaneously and results in poor clinical outcomes. Muscle atrophy and fatty infiltration in rotator cuff muscles are major complications of chronic massive RCT and are thought to be the key factors responsible for the failure of attempted massive RCT repair. However, the pathophysiology of rotator cuff muscle atrophy and fat infiltration remains largely unknown, and no small animal model has been shown to reproduce the histologic and molecular changes seen in massive RCT. In this article, we report a novel rat massive RCT model, in which significant and consistent muscle atrophy and fat infiltration were observed in the rotator cuff muscles after rotator cuff tendon transection and denervation. The supraspinatus and infraspinatus muscle lost 25.4% and 28.9% of their wet weight 2 weeks after complete tendon transection, respectively. Six weeks after surgery, the average wet weight of supraspinatus and infraspinatus muscles decreased 13.2% and 28.3%, respectively. Significant fat infiltration was only observed in infraspinatus 6 weeks after tendon transection. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:588–595, 2011     

Lateral to medial fibro‐adipogenic degeneration are greater in infraspinatus than supraspinatus following nerve and tendon injury of murine rotator cuff

Small animal models of massive tears of the rotator cuff (RC) were introduced a decade ago and have been extensively used to study the pathophysiology of chronically injured RC. Transection of rodent suprascapular nerve and RC tendon results in progressive muscle atrophy, fibrosis and fat accumulation and affect the infraspinatus and supraspinatus muscles similarly to that seen in the setting of massive RC tears in humans. The purpose of this study was to perform a comprehensive and detailed analysis of the kinetics of fibrotic scar and adipose tissue development comparing phenotypic differences between chronically injured infraspinatus and supraspinatus. Automatic mosaic imaging was used to create large image of whole infraspinatus or supraspinatus sectioned area for quantification of spatial heterogeneity of muscle damage. Pathologic changes advanced from the lateral site of transection to the medial region far from the transection site. A prominent, accelerated muscle fibrosis and fat accumulation was measured in injured infraspinatus compared to supraspinatus. Furthermore, adipose tissue occupied significantly larger area than that of fibrotic tissue in both muscles but was greater in infraspinatus within 6 weeks post induction of injury. Our findings confirm that infraspinatus is more susceptible to accelerated chronic degeneration and can be used to identify the physiological functions that distinguish between the response of infraspinatus and supraspinatus in the setting of massive tears. Whether these pathologic differences observed in mice are reflected in humans is one key aspect that awaits clarification.     

Evaluation of morphologic changes of the rabbit supraspinal muscle]

The aim of this study was to evaluate morphologic changes within rabbit supraspinatus after detachment of its tendon from the greater tubercle along with infraspinatus and subscapularis tenotomy. Stained with hematoxylin and eosin muscle sample has been examined after 6 weeks (group A), 3 months (group B) and 6 months (group C). There were 10 rabbits in each group. The muscle atrophy was accompanied by statistically significant increase of the interstitium volume in group B (24.5%) and C (26.3%) as opposed to A (15.4%). Statistically significant differences were also found in interstitium volume of tenotomized and contralateral supraspinatus muscle.     

Supraspinatus muscle atrophy in relation to aging with or without shoulder pathology: A radiographic study

IntroductionSupraspinatus muscle atrophy is commonly associated with shoulder disease, but the effect of ageing on atrophy is not well understood. It was the aim of this study to investigate this effect using MRI scans in older patients.Methods and materialsA retrospective review of MRI scans in patients aged >70 years was performed between Jan 2016–Dec 2018.Both normal and abnormal scans were included in the analysis which included quantifying muscle atrophy of the supraspinatus using Thomazeu's occupation ratio.ResultsThere were 39 normal shoulder MRI scans with a mean age of 75 years (range: 70–88) and 163 abnormal scans with a mean age of 77 years (range: 70–93). The mean supraspinatus occupation ratio for normal MRI scans was 0.57 (range: 0.33–0.86) and abnormal scans 0.35 (range: 0.17–0.90). Occupation ratio was maintained with advancing until the age of 85 years before undergoing a significant declin following this.ConclusionThis study has shown that the occupation ratio is significantly reduced with shoulder disease, but normal shoulders do not undergo significant atrophy of supraspinatus tendon with increasing age. An occupation ratio of <0.32 is unlikely to occur in normal shoulders and this awareness may be useful when planning shoulder surgery, specifically shoulder arthroplasty.     

Is the Supraspinatus Muscle Atrophy Truly Irreversible after Surgical Repair of Rotator Cuff Tears?

Background

Atrophy of rotator cuff muscles has been considered an irreversible phenomenon. The purpose of this study is to evaluate whether atrophy is truly irreversible after rotator cuff repair.

Methods

We measured supraspinatus muscle atrophy of 191 patients with full-thickness rotator cuff tears on preoperative magnetic resonance imaging and postoperative multidetector computed tomography images, taken at least 1 year after operation. The occupation ratio was calculated using Photoshop CS3 software. We compared the change between pre- and postoperative occupation ratios after modifying the preoperative occupation ratio. In addition, possible relationship between various clinical factors and the change of atrophy, and between the change of atrophy and cuff integrity after surgical repair were evaluated.

Results

The mean occupation ratio was significantly increased postoperatively from 0.44 ± 0.17 to 0.52 ± 0.17 (p < 0.001). Among 191 patients, 81 (42.4%) showed improvement of atrophy (more than a 10% increase in occupation ratio) and 33 (17.3%) worsening (more than a 10% decrease). Various clinical factors such as age tear size, or initial degree of atrophy did not affect the change of atrophy. However, the change of atrophy was related to repair integrity: cuff healing failure rate of 48.5% (16 of 33) in worsened atrophy; and 22.2% (18 of 81) in improved atrophy (p = 0.007).

Conclusions

The supraspinatus muscle atrophy as measured by occupation ratio could be improved postoperatively in case of successful cuff repair.     

Glenoid version and rotator cuff tears.

The purpose of this study was to determine the relationship between rotator cuff (RC) tear and the orientation of the glenoid. Ninety-six shoulders (94 patients) that underwent open RC repair were grouped according to the type of tear. We measured on MRI the acromio-glenoid angle (AG) and the supraspinatus fossa glenoid angle on the anterior-posterior (SGAP) and axial (SGAX) views. RC patients had a smaller AG angle (76+/-7 degrees vs. 86+/-10 degrees ) and a larger SGAP angle (112+/-6 degrees vs. 102+/-7 degrees ) compared to controls (p<0.001). We also found a highly significant difference (p<0.001) in glenoid version measured by SGAX between anterior cuff tears (-5+/-4 degrees ) and posterior cuff tears (3+/-3 degrees ). Furthermore, we identified an association between RC tear and the orientation of the glenoid relative to the axis of the supraspinatus fossa. Greater retroversion is predictive of an anterior cuff injury and greater anteversion is predictive of a posterior cuff injury.     

桃红四物汤调控巨噬细胞极化对肩袖损伤的机制研究

目的基于白介素(IL)-4/信号传导及转录激活蛋白(STAT)6信号通路调控巨噬细胞极化,利用小鼠动物模型探讨桃红四物汤对肩袖撕裂术后愈合的影响及其作用机制。 方法将50只C57BL/6J小鼠随机分为空白对照组、肩袖损伤组(模型组)及桃红四物汤低、中、高剂量组,每组10只。除对照组外,其他组小鼠均构建肩袖撕裂重建模型。术后预防感染并正常饲养12周,桃红四物汤组小鼠灌胃相应药液,每次每只小鼠灌胃量均为2 ml;对照组每日清晨予等体积生理盐水;连续给药12周,1次/d。末次给药24 h后,进行冈上肌腱生物力学刚度测试;采用酶联免疫吸附测定法(ELISA)检测小鼠血清一氧化氮合酶(iNOS)、IL-6、甘露糖受体(CD206)的含量;采用实时定量PCR(RT-PCR)技术检测小鼠腱骨界面组织IL-1β、肿瘤坏死因(TNF)子-α、IL-10、炎症区域分子1(Fizz1)mRNA表达;采用Western Blot法检测腱骨界面组织iNOS、精氨酸酶-1(Arg-1)、IL-4、STAT6、磷酸化- STAT 6(p-STAT6)蛋白含量。多组间数据比较采用单因素方差分析,组间两两比较采用LSD-t检验。 结果用药干预后与肩袖损伤组比较,桃红四物汤各个剂量组拉断载荷、刚度测试数值上调(F＝64.822、58.431,均为P<0.05);iNOS、IL-6(M1极化标志物)水平下调(F＝82.618、61.372,均为P<0.05),CD206(M2极化标志物)水平上调(F＝58.942,P<0.05);桃红四物汤中、高剂量组IL-1β、TNF-mRNA(M1极化标志物)的表达下调(F＝38.631、33.714,均为P<0.05),而IL-10、Fizz1 mRNA(M2极化标志物)的表达上调(F＝41.731、67.431,均为P<0.05)。桃红四物汤低、中、高剂量组Arg1、IL-4、p-STAT6的蛋白表达上调(F＝26.841、29.750、26.863,均为P<0.05)。 结论桃红四物汤可促进肩袖撕裂小鼠的肌腱愈合,其机制可能与IL-4/STAT6信号通路调控巨噬细胞极化有关。     

两种不同术式治疗合并肩胛上神经损伤的巨大肩袖撕裂后神经恢复的临床对比研究

目的对比传统双排修复术与阔筋膜移植术两种术式治疗合并肩胛上神经损伤的巨大肩袖撕裂患者的功能恢复情况。 方法回顾性分析2013年1月至2018年1月因巨大肩袖撕裂损伤于本院行关节镜肩袖损伤修复术患者20例,其中传统双排缝合组（A组）10例,阔筋膜移植组（B组）10例。所有患者术前均经肩关节MRI及肌电图诊断为巨大肩袖损伤合并神经损伤。术后1个月、6个月定期随访患者。比较手术前后两组患者的疼痛视觉模拟评分（visual analogue scale,VAS）、美国加州大学洛杉矶分校（University of California at Los Angeles,UCLA）评分、Constant-Murely肩关节功能评分的变化情况。术后6个月复查肌电图及MRI评估肩袖愈合及神经恢复情况。 结果20例患者均获得随访,随访时间6~18个月。术后6个月A组VAS评分从术前（7.4±0.8）分下降到（2.3±1.7）分,差异有统计学意义（P<0.01）,UCLA评分从术前（11.5±1.4）分上升到（28.3±5.8）分,差异有统计学意义（P<0.01）,Constant-Murely评分从术前（45.6±6.2）分上升到（79.0±11.7）分,差异有统计学意义（P<0.01）。B组VAS评分从术前（7.9±0.6）分下降到（2.7±1.8）分,差异有统计学意义（P<0.01）,UCLA评分从术前（10.1±1.4）分上升到（26.9±6.9）分,差异有统计学意义（P<0.01）,Constant-Murely评分从术前（39.0±3.4）分上升到（72.9±9.4）分,差异有统计学意义（P<0.01）。术后6个月时两组患者VAS评分比较差异无统计学意义（P>0.05）,两组患者UCLA评分比较差异无统计学意义（P>0.05）,两组患者Constant-Murely评分比较差异无统计学意义（P>0.05）。术后6个月复查肌电图,A组患者无肩胛上神经损伤,B组患者中有5例患者仍有肩胛上神经损伤（P<0.01）。 结论关节镜下巨大肩袖损伤传统双排修复术及阔筋膜移植术均能改善患者肩关节功能,双排缝合对于肩胛上神经功能恢复的短期效果要比阔筋膜移植组好,但再撕裂可能性大。     

Arthroscopic Transosseous Reinsertion of the Rotator Cuff

Abstract Objective: Arthroscopic reinsertion of the supraspinatus and infraspinatus tendons by means of imitation of an open trans osseous reinsertion technique. Indications: Tears in the tendon cuffs of the supraspinatus and infraspinatus muscles. Patients < 75 years of age. Contraindications: Retracted tendons that cannot be sufficiently mobilized to provide a tension-free reinsertion. Tears of the tendon cuff of the subscapsularis muscle. Surgical Technique: The free edges of the tendons are sparingly resected. The tendon attachment site on the greater tuberosity is freed of soft tissue and decorticated using an arthroscopic bone burr. A full-radius burr is used to drill insertion sites for the sutures in the tuberosity. A hollow needle is inserted percutaneously to puncture the free edges of the tendon for a single reinsertion suture. The hollow needle is then fed through the greater tuberosity to the lateral portal. The suture is guided through the needle and advanced via a working cannula. If the tear is > 2 cm in width, a mattress suture should be placed via another channel in the bone. This is to provide plane contact of the tendon to the reinsertion site. Postoperative Management: Restriction of movement using a shoulder bandage for 6 weeks after the operation. Results: In the 75 patients treated using a single suture, there was an improvement compared to the related Constant Score from 55.8% before the operation to 80.4% at the follow-up examination, after an average of 26.8 months. The average age in this group was 58.2 years (range 35–75 years). In the 21 patients treated with a mattress suture, there was an improvement compared to the related Constant score from 59% before the operation to 83% at 14.3 months after the operation. The average age in this group was 58 years (range 35–75 years). The following is a reprint from Operat Orthop Traumatol 2006;18:1–18 and continues the new series of articles at providing continuing education on operative techniques to the European trauma community. Reprint from: Oper Orthop Traumatol 2006;18:1–18 DOI 10.1007/s00064-006-1159-1     

Spasticity may defend skeletal muscle size and composition after incomplete spinal cord injury

DESIGN: Cross-sectional. OBJECTIVES: (1) To determine the effects of the level of spinal cord injury (SCI) on skeletal muscle, intramuscular fat (IMF) cross-sectional areas (CSAs) and relative IMF; (2) to determine the relation, if any, of spasticity to each of these variables after incomplete SCI. SETTINGS: In-patient study at the Shepherd Center, Atlanta, GA, USA. METHODS: Thirteen individuals with incomplete SCI were classified according to their level of injury into a high level of injury group (HLI, C5-C7, n=8) and a low level of injury group (LLI, T12-L2, n=5). Spasticity was determined for thigh muscles using a modified Ashworth scale at 6 weeks post-injury. T1-weighted magnetic resonance (MR) images were taken 6 weeks post-injury to measure thigh skeletal muscle and IMF CSAs. RESULTS: Spasticity was significantly evident in the HLI group compared to the LLI group (P=0.023). Six weeks post-injury, muscle CSA was 103+/-18 cm(2) in the HLI group and 80+/-20 cm(2) in the LLI group (P=0.042). Relative IMF was 3.6+/-2.0% in HLI and 7.5+/-4.0% in LLI (P=0.021). Additionally, spasticity accounted for 54% of the variability in muscle CSA for all subjects (r (2)=0.54, P=0.006). CONCLUSIONS: Spasticity may be an important factor in defending skeletal muscle size and indirectly preventing IMF accumulation early after incomplete SCI.     

Muscle stem cell activation in a mouse model of rotator cuff injury

Rotator cuff (RC) tears are frequently complicated by muscle atrophy. Muscle stem cells (MuSCs) repair damaged myofibers following injury, but their role in the prevention or pathogenesis of atrophy following RC tears remains undefined. We hypothesized that the RC MuSC population would be affected by supraspinatus (SS) and infraspinatus (IS) tendon transection (TT) compared to uninjured muscle in a mouse model of RC tear. C57BL6/J mice underwent unilateral SS and IS TT and contralateral sham surgery. At 3, 8, or 14 weeks after injury, mice were euthanized, and SS and IS were harvested for FACS sorting of CD31‐/CD45‐/Sca1‐/ITGa7+/VCAM+ MuSCs or histological analysis. Ki‐67+ MuSCs from injured muscle increased 3.4‐fold at 3 weeks (p = 0.03) and 8.1‐fold at 8 weeks (p = 0.04) following TT injury, but returned to baseline by 14 weeks (p = 0.91). Myod1 remained upregulated 3.3‐fold at 3 weeks (p = 0.03) and 2.0‐fold at 14 weeks (p = 0.0003), respectively. Myofiber cross‐sectional area was decreased at both 3 and 14 weeks after injury, but the number of MuSCs per fiber remained relatively constant at 3 (p = 0.3) and 14 (p = 0.6) weeks after TT. In this study, we characterized the longitudinal effect of RC tendon injury on the MuSC population in supraspinatus and infraspinatus muscles. MuSCs are transiently activated, and are not depleted, in spite of persistent muscle atrophy. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1370–1376, 2018.

     

Inhomogeneous mechanical behavior of the human supraspinatus tendon under uniaxial loading.

Disorders of the rotator cuff, particularly tears of the rotator cuff tendons, cause significant shoulder disability. Among numerous factors thought to be responsible for the initiation and progression of supraspinatus tears are those related to the tendon's biomechanical properties. We hypothesized that in supraspinatus tendons subjected to tensile loading a strain gradient (difference) exists between the articular and bursal tendon surfaces, that regional strain differences exist on each of these two tendon surfaces, and that tendon surface strains vary with glenohumeral abduction. To test these hypotheses, the intrinsic inhomogeneous deformational characteristics of the articular and bursal surfaces of eight intact human cadaveric supraspinatus tendons were studied at three glenohumeral abduction angles using a novel multiple strain measuring system which simultaneously recorded surface marker displacements on two opposing soft tissue surfaces. Under applied tensile loads, the articular surface exhibited greater strain at 22 degrees (7.4+/-2.6% vs. 1.3+/-0.7%, p=0.0002) and 63 degrees (6.4+/-1.6% vs. 2.7+/-1.2%, p=0.0001) whereas the bursal surface exhibited greater strain at 90 degrees (7.6+/-2.8% vs. 4.9+/-0.4%, p=0.013). At all abduction angles, insertion strains were higher than those of the mid-tendon and tendon-muscle junction regions. The existence of inhomogeneous surface strains in the intact supraspinatus tendon demonstrates that intratendinous shear occurs within the tendon. The higher strain on the articular side of the tendon, especially at the insertion region, suggests a propensity for tears to initiate in the articular tendinous zone.     

Importance of Initial Peak Torque of the Supraspinatus Muscle during Shoulder Flexion

BackgroundMost previous studies have evaluated flexion strength to assess recovery after arthroscopic rotator cuff (RC) repair. However, limited data are available regarding peak torque at the initial angle (iPT) because most studies have measured flexion strength for peak torque (PT), particularly in small- and medium-sized supraspinatus tears. The purpose of this study was to compare conventional PT and iPT to evaluate supraspinatus muscle strength after arthroscopic RC repair in patients with small- and medium-sized supraspinatus tears.MethodsIsokinetic muscle performance testing was performed in 42 patients with small tears and in 47 patients with medium-sized tears. PT and iPT were evaluated before and 1 year after surgery and were recorded at an angular velocity of 60°/sec and 180°/sec with an isokinetic test.ResultsPT and iPT were significantly lower in the involved-side shoulders than in the uninvolved-side shoulders (PT: small tear, p < 0.001; medium tear, p < 0.001; iPT: small tear, p < 0.001; medium tear, p < 0.001) in both groups, preoperatively. However, postoperatively, in the involved-side shoulders, PTs were not different in both small- and medium-sized tears (all p > 0.05), but iPTs were significantly lower in the involved-side shoulders (small tear, p < 0.001; medium tear, p < 0.001). iPT was significantly lower in the involved side shoulders in the medium-sized tear group than in the small-sized tear group before and after surgery (p < 0.05). In the small- and medium-sized tear groups, tear size was significantly correlated with preoperative iPT in the involved-side shoulders (small tear: r = −0.304, p = 0.046; medium tear: r = −0.323, p = 0.027). However, pain visual analog scale was significantly correlated with preoperative (small tear: r = −0.455, p = 0.002; medium tear: r = −0.286, p = 0.044) and postoperative (small tear: r = −0.430, p = 0.005; medium tear: r = −0.354, p = 0.021) iPT in the involved-side shoulders. Furthermore, fatty infiltration grade of the supraspinatus muscle and global fatty degeneration index were not associated with preoperative and postoperative PT and iPT in each group (all p > 0.05).ConclusionsiPT is as important as conventional PT in isokinetic testing to assess supraspinatus muscle strength before and after RC repair.     

肩关节MRI对肩峰小骨与冈上肌和冈下肌损伤的相关性评估

目的:探讨肩峰小骨的MRI表现,并分析肩峰小骨与冈上肌和冈下肌损伤之间的相关性.方法:回顾性分析2010年1月至2020年8月诊断为肩峰小骨患者21例(有肩峰小骨组)的MRI资料,并匹配同期检查的21例无肩峰小骨者作为无肩峰小骨组.有肩峰小骨组男14例,女7例;年龄29～77(55.5±11.5)岁.无肩峰小骨组男10...