MicroRNA-26a deficiency attenuates the severity of frozen shoulder in a mouse immobilization model.

The main pathogenesis of the frozen shoulder is thought to be the inflammation of the intra-articular synovium and subsequent fibrosis of the shoulder joint capsule. However, the molecular pathogenesis of the frozen shoulder is still unknown. A class of noncoding RNAs, microRNAs contribute to various diseases including musculoskeletal diseases. MicroRNA-26a (miR-26a) has been reported to be associated with fibrosis in several organs. This study aims to reveal the role of miR-26a on fibrosis in the shoulder capsule using a frozen shoulder model in miR-26a deficient (miR-26a KO) mice. MiR-26a KO and wild-type (WT) mice were investigated using a frozen shoulder model. The range of motion (ROM) of the shoulder, histopathological changes such as synovitis, and fibrosis-related gene expression in the model mice were evaluated to determine the role of miR-26a. In WT mice, both inflammatory cell infiltration and thickening of the inferior shoulder joint capsule were observed after 1 week of immobilization, and this thickening further progressed over the subsequent 6 weeks. However, the immobilized shoulder in miR-26a KO mice consistently exhibited significantly better ROM compared with WT mice at 1 and 6 weeks, and histological changes were significantly less severe. The expression of inflammation- and fibrosis-related genes was decreased in the miR-26a KO mice compared with WT mice at 1 and 6 weeks. Together, miR-26a deficiency attenuated the severity of frozen shoulder in the immobilization model mouse. The present study suggests that miR-26a has the potential to be a target miRNA for therapeutic approach to frozen shoulder.

Factors affecting stress shielding and osteolysis after reverse shoulder arthroplasty: A multicenter study in a Japanese population.

BACKGROUND: Stress shielding and osteolysis around the humeral stem after reverse shoulder arthroplasty causes loosening and periprosthetic fractures and reduces bone stock during revision surgery. In Japanese patients, who have relatively small bodies, different characteristics may exist regarding the occurrence of these changes compared with the characteristics of Westerners, who have relatively larger frames. The purpose of this multicenter study was to investigate the incidence and clarify the predictors of stress shielding and osteolysis in Japanese individuals who underwent reverse shoulder arthroplasty. METHODS: The occurrence of stress shielding and osteolysis was investigated in 135 shoulders that had undergone reverse shoulder arthroplasty at least 2 years prior in five Japanese hospitals. During post-surgical follow-up, which was conducted every 3 months, the locations of the stress shielding occurrences, such as cortical thinning and osteopenia (which primarily occurred in zones 1, 2, and 7, where 1 is the greater tuberosity and 7 is the calcar part), spot weld, and condensation lines, were recorded. Cases without any abnormal findings on radiographs obtained up to ≥2 years after surgery were regarded as having no abnormalities. Finally, the predictors of cortical thinning and proximal humeral osteolysis were assessed using univariate and multivariate regression analyses. RESULTS: Cortical thinning and osteopenia occurred in 68 shoulders, a condensation line occurred in 37 shoulders, and spot weld occurred in 23 shoulders. In particular, greater tuberosity and calcar osteolysis occurred in 40 and 47 shoulders, respectively. Long stem, cementless stem, and a larger proximal filling ratio were independent predictors of cortical thinning and osteopenia, whereas a cementless stem, larger metaphysis diameter, and a larger proximal filling ratio were associated with proximal humeral osteolysis. CONCLUSIONS: The predictors of stress shielding and osteolysis included the use of long stems, cementless stems, larger proximal filling ratios, and larger metaphysis diameters. LEVEL OF EVIDENCE: retrospective comparative study (Level III).

Return to sports after arthroscopic Bankart repair in teenage athletes: a retrospective cohort study.

BACKGROUND: Anterior shoulder instability is frequent among young athletes. Surgical treatment for this injury aims to facilitate an early return to sports (RTS). However, the rate of recurrent instability after surgery is reportedly high among young patients, and it is unclear whether surgery ensures satisfactory RTS. The purpose of this study was to verify the clinical outcomes and RTS after arthroscopic Bankart repair in competitive teenage athletes without critical bone loss in the glenoid. METHODS: We retrospectively reviewed competitive teenage athletes who underwent arthroscopic Bankart repair. Patients with large bony defects in the glenoid, larger than 20% of the healthy side, were excluded. Clinical outcomes, recurrent instability, the final level of RTS, and the time needed for RTS were analyzed. RESULTS: In total, 50 patients with a mean follow-up period of 44.5 ± 19.6 (range, 24-85 months) months were included. The mean age at surgery was 16.8 ± 1.7 (range, 13-19 years) years. Two patients (4.0%) experienced recurrent instability. All patients returned to sports, 96% of patients participated competitively, and 76% achieved a complete return to the pre-injury level without any complaints. The time for RTS was 6.6 ± 2.7 months (range, 3-18 months), to competitions was 9.3 ± 4.0 (range, 6-24 months) months, and to complete return was 10.6 ± 4.3 (range, 8-24 months) months. The complete return rates varied by sports type, with 82% in contact athletes, 59% in dominant-hand overhead athletes, and 100% in other athletes (P = 0.026). Other preoperative factors or concomitant lesion such as bony Bankart, superior labrum tear, or humeral avulsion of glenohumeral ligament lesion did not affect the complete RTS. CONCLUSION: Arthroscopic Bankart repair is an effective surgical procedure for anterior shoulder instability, even among competitive teenage athletes. Sports type was the only factor associated with complete RTS after surgery.

Clinical outcomes and tendon lengthening after arthroscopic rotator cuff repair.

BACKGROUND: There is a phenomenon in which the tendon appears to increase the length after rotator cuff repair. However, it is unclear in which cases tendon lengthening occurs and how the degree of lengthening affects the surgical outcome. This study aimed to evaluate preoperative and postoperative musculotendinous junction (MTJ) and tendon length on magnetic resonance imaging and assess the postoperative tendon lengthening and its impact on postoperative outcomes. METHODS: We reviewed 109 patients with good repair integrity after arthroscopic rotator cuff repair. Patients whose supraspinatus tendons were simply pulled out laterally without any additional procedures were included. They underwent serial magnetic resonance imaging before surgery and at 3, 6, and 24 months after surgery. The location of the MTJ in relation to the line of the glenoid fossa and the supraspinatus tendon length were measured. Clinical evaluation was conducted 2 years after surgery, including the range of shoulder motion, shoulder strength index (affected/unaffected strength), Constant score, University of California, Los Angeles score, and pain numeric rating scale. The characteristics of the preoperative tendon, change in tendon length over time, amount of the lateral shift of MTJ location and tendon length, and impact of tendon lengthening on postoperative clinical outcomes were analyzed. RESULTS: The preoperative tendon retraction significantly correlated with the MTJ location (r = -0.75; P < .0001) and preoperative tendon length (r = -0.46; P < .0001). The tendon length at 3, 6, and 24 months after surgery was significantly longer than those before surgery (26.7 ± 5.8 mm, 27.9 ± 6.6 mm, 28.5 ± 5.6 mm, and 21.5 ± 5.1 mm, respectively). From before surgery to 24 months after surgery, the MTJ location moved 8.4 ± 8.6 mm laterally and the tendon length increased 7.0 ± 6.1 mm. A significant and weak negative correlation was found between tendon lengthening and the abduction strength index (r = -0.22; P = .03); however, no significant correlation with pain, range of shoulder motion, external rotation strength index, Constant score, and University of California, Los Angeles score was found. Multiple linear regression analysis also showed that tendon lengthening was only associated with the abduction strength index (standardized coefficient = -0.20, P = .03). CONCLUSIONS: Tendon lengthening and lateral shift of MTJ location were observed after arthroscopic rotator cuff repair, and they correlated with preoperative tendon retraction. Although the amount of tendon lengthening had negative weak correlation with abduction strength index, it did not affect other postoperative outcomes.

Range of Motion and Muscle Strength Changes in Japanese Professional Pitchers During the Baseball Season.

BACKGROUND: There are no studies examining changes in the physical function throughout the baseball season in Japanese professional players. We examined the range of motion (ROM) and muscle strength changes in professional baseball pitchers as the season progresses. MATERIALS AND METHODS: Five professional baseball pitchers were included. ROM, flexibility, and muscle strength of the trunk and shoulder, elbow, hip, knee, and ankle joints were measured pre-season (PRE), mid-season (MID), and post-season (POST). RESULTS: The total shoulder arc ROM of the dominant sides significantly decreased compared to that of the nondominant sides at MID and POST. Shoulder abduction muscle strength of the dominant sides significantly decreased at POST compared to that at PRE. In the trunk, lateral flexion ROM of bilateral sides significantly decreased at MID and POST compared to that at PRE, and the duration time of the side bridge test of the dominant sides significantly decreased at POST to that at PRE. Hip extension ROM and muscle strength and internal rotation ROM of the push-off leg significantly decreased at POST compared to that at PRE. CONCLUSION: The total shoulder arc ROM and shoulder abductor muscle strength of the dominant sides, trunk lateral flexion ROM and muscle strength, push-off leg hip joint extension muscle strength and ROM, and internal rotation ROM were more susceptible to changes as the season progressed. In order to maintain performance and prevent a throwing disorder, it is necessary to focus on these movements during the season and to appropriately train and condition these muscle groups.

Prevalence of Rotator Cuff Tears Among Older Tennis Players and Its Impact on Clinical Findings and Shoulder Function.

CONTEXT: Tennis is a noncontact sport playable at an individual's own pace. Thus, it is popular among the older adults. It is known that older adults often suffer from rotator cuff tears (RCTs), which may affect tennis activity. However, the prevalence and influence of RCTs on tennis play among older players are not well-known. This study aimed to evaluate the prevalence of RCTs in older tennis players and its impact on physical findings and shoulder function. DESIGN: A cross-sectional study. METHODS: Fifty-three tennis players (mean age: 70.7 y; range: 60-83 y) participating in a recreational-level tennis tournament were examined in this study. An ultrasonographic examination of both shoulders was performed to detect RCTs. Relationships between RCTs of the dominant shoulder and clinical findings, shoulder pain, and shoulder function including range of motion, shoulder strength, and Single Assessment Numeric Evaluation score, and Disability of the Arm, Shoulder and Hand-Sports Module score were assessed. RESULTS: RCTs were detected in 19 (36%) dominant shoulders and 6 (11%) nondominant shoulders. Asymptomatic RCTs were detected in 11 (58%) dominant shoulders and 5 (83%) nondominant shoulders. Increased crepitus and more positive results in the empty can test, and infraspinatus test were observed in the dominant shoulders with RCTs than in those without; however, there was no difference in shoulder pain, range of motion; strength; Single Assessment Numeric Evaluation score; and Disability of the Arm, Shoulder and Hand-Sports Module score between the players with and without RCTs. CONCLUSIONS: One-third of the older tennis players in this study had RCTs in the dominant shoulder with some positive physical sign of an RCT. However, shoulder pain and shoulder function did not differ between the players with and without RCTs, suggesting that RCTs had a minor impact on the tennis performance in the participants of this study.

Return to sports after arthroscopic bankart repair on the dominant shoulder in overhead athletes.

BACKGROUND: Arthroscopic Bankart repair (ABR) yields good results in young athletes with anterior shoulder instability. However, the treatment for overhead athletes is challenging because recovery of range of motion is necessary for return to play and repeated shoulder motion may lead to recurrent instability. The aim of this study was to investigate the clinical outcomes and return to sports after ABR on the dominant shoulder in overhead athletes. METHODS: This study included 24 competitive level overhead athletes who underwent ABR on their dominant shoulders. The mean age at surgery was 17.6 years, and the mean follow-up was 39.7 months. The range of bilateral shoulder motion, the Rowe score, the Japanese Shoulder Society Shoulder Instability Score (JSS-SIS), and the Japanese Shoulder Society Shoulder Sports Score (JSS-SSS) were evaluated before the surgery and at the final visit. Recurrent instability, the final level of return to sports, and the duration before returning to sports were confirmed, as well as the pre-, intra- and postoperative factors, which prohibited complete return to play. RESULTS: There were no cases of recurrent instability. The Rowe score, JSS-SIS, JSS-SSS, and the range of flexion, abduction, internal rotation significantly improved postoperatively. Fifteen athletes (62.5%) returned to the same or superior levels without any complaint in their shoulders. The mean duration needed for a complete return was 13.3 months. The postoperative external rotation deficit in abduction was larger in the athletes who returned incompletely than those who returned completely, 7.8° and 2.3°, respectively. CONCLUSIONS: ABR is a reliable surgery for preventing recurrent instability in overhead athletes, however the rate of a complete return to preinjury level was low and a long duration was needed for complete return to play. The postoperative external rotation may be necessary for a complete return to overhead sports. LEVEL OF EVIDENCE: Level IV: Retrospective Case Series.

Shoulder ranges of motion and humeral torsions of injured baseball players have different characteristics depending on their pitching sides.

BACKGROUND: Right- and left-side throwers in baseball may have different shoulder conditions and throwing biomechanics. This study aimed to compare the passive range of motion, humeral torsion, and clinical findings between right- and left-handed throwers who sustained throwing shoulder injuries and confirm the differences in the characteristics between throwing sides. METHODS: A total of 52 pitchers diagnosed with throwing shoulder injuries were included in this study: 27 patients were right-side throwers (R group), and 25 were left-side throwers (L group). We measured the bilateral passive external and internal rotation angles in abduction position (ABIR) and total arc at their first visit. To assess posterior shoulder tightness, the internal rotation angles in forward flexion (FIR), and the abduction angle (AA) and horizontal flexion angle (HFA) without scapula motion were measured. The bilateral humeral torsion angles were also measured using ultrasonography. These values were compared between the participants' throwing and non-throwing sides and between the R and L groups' throwing sides. Furthermore, several physical findings in the shoulders were assessed, and the positive ratio was compared between the R and L groups. RESULTS: On comparing the throwing and non-throwing sides, the R group had significantly greater external rotation angles in the abduction position and humeral torsion angle, and smaller ABIR, total arc, FIR, AA, and HFA in the throwing side, while the L group showed no significant differences, except for a smaller ABIR and larger HFA in the throwing side. On comparing the throwing side between the R and L groups, the R group had a smaller FIR, AA, and FHA than the L group. Regarding the physical findings, the posterior jerk test, Kim test, anterior and posterior drawer sign, sulcus sign, and scapular winging in the L group were significantly more positive than in the R group. CONCLUSION: The range of motion and humeral torsions differed between the left- and right-side throwers, as did the pathology between their throwing sides. Clinicians should consider the possibility that the pathological condition differs between left- and right-side throwers.

Effectiveness of measuring tension during arthroscopic rotator cuff repair.

PURPOSE: Arthroscopic rotator cuff repair (ARCR) for relatively small rotator cuff tears (RCTs) has shown promising results; however, such surgery for larger tears often results in failure and poor clinical outcomes. One cause of failure is over-tension at the repair site that will be covered with the tendon stump. Reports on the clinical outcomes using ARCR with tension ≤ 30 N are lacking. This study aimed to evaluate ARCR outcomes and failure rates using less tension (30 N) and to assess the prognostic factors for failure. METHODS: Our study group comprised of 118 patients who underwent ARCR for full-thickness RCTs with full tendon stump coverage of the footprint with a tension of ≤ 30 N, measured using a tension meter; no additional procedures, such as margin convergence or footprint medialisation, were performed. The failure rate was calculated, and the prognostic factor for failure was assessed using multivariate regression analyses. RESULTS: There were seven cases of failure in the study group. Postoperatively, flexion and internal rotation ranges of motion, acromiohumeral interval, muscle strength, and clinical results improved significantly. Using multivariate regression analyses, intraoperative concomitant subscapularis tendon lesion and pre-operative infraspinatus tendon retraction, assessed using radial-sequence magnetic resonance imaging, were significantly correlated with post-ARCR failure using less tension (p = 0.030 and p = 0.031, respectively). CONCLUSION: ARCR is likely to succeed for RCTs that can be extracted using tension ≤ 30 N. However, cases with more severe subscapularis tendon lesions and those with high infraspinatus tendon retraction may show surgical failure. LEVEL OF EVIDENCE: LEVEL IV Retrospective case series.