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).

Evaluation of subscapularis tendon tears of the anterosuperior aspect using radial-sequence magnetic resonance imaging.

BACKGROUND: Magnetic resonance imaging (MRI) is widely used to diagnose subscapularis tendon tears; however, it is difficult to assess the anterosuperior aspect of these tears. Radial-sequence MRI can reveal the fiber components of the anterosuperior aspect, from perpendicular, by overcoming the partial volume effect. We aimed to classify the insertion of subscapularis tendon tears on radial-sequence MRI and determine the effectiveness of radial-sequence MRI for subscapularis tendon tear assessments. METHODS: We retrospectively investigated 196 patients (mean age, 66.7 ± 9.0 years; 118 men, 78 women) who underwent 1.5 T MRI before arthroscopic rotator cuff repair. Radial-sequence MRI findings of the anterosuperior aspect insertion of the subscapularis tendon were classified into five grades, and intraoperative findings compared with preoperative conventional MRI and radial-sequence MRI. We calculated sensitivity, specificity, accuracy, and positive and negative predictive values. Interobserver and intraobserver reliability for radial-sequence MRI classification was calculated using kappa (κ). RESULTS: Conventional MRI sensitivity of subscapularis tendon tears was 45.3%; specificity, 95.8%; accuracy, 82.1%; positive predictive value, 80.0%; and negative predictive value, 82.5%. Radial-sequence MRI sensitivity was 92.5%; specificity, 88.1%; accuracy, 89.3%; positive predictive value, 74.2%; and negative predictive value, 96.9%. Sensitivity (P < .001), accuracy (P = .04), specificity (P = .02), and negative predictive values (P < .001) in radial-sequence MRI were significantly higher than those in conventional MRI. Intraobserver and interobserver reliabilities for radial-sequence MRI classification were κ = 0.78 and 0.65, respectively, corresponding to high reproducibility, and defined as good. CONCLUSION: We provide evidence that radial-sequence MRI is an effective tool to evaluate subscapularis tendon tears, especially before surgery.

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.

Arthroscopic Rotator Cuff Repair With Muscle Advancement and Artificial Biodegradable Sheet Reinforcement for Massive Rotator Cuff Tears.

BACKGROUND: Because high failure rates have frequently been reported after arthroscopic rotator cuff repair (ARCR) of massive rotator cuff tears (mRCTs), we introduced the technique of ARCR with supraspinatus and infraspinatus muscle advancement (MA). However, for cases where the original footprint cannot be completely covered, additional surgery using an approved artificial biomaterial is performed. PURPOSE: To investigate the postoperative clinical outcomes and failure rate after MA-ARCR, with and without our reinforcement technique. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 74 patients (mean ± SD age, 68.7 ± 7.7 years) diagnosed with mRCT with a minimum postoperative follow-up of 2 years were included in the current study. Of these patients, 47 underwent MA-ARCR with polyglycolic acid (PGA) sheet reinforcement (study group), and 27 patients underwent MA-ARCR alone (control group). PGA reinforcement was performed when full coverage of the footprint could not be achieved by MA alone, but where the latter was possible, reinforcement was not required. Thus, the study group had significantly worse muscle quality than the control group (P < .05). The pre- and postoperative range of motion (ROM), isometric muscle strength, acromiohumeral interval, and clinical outcomes were evaluated and compared between these 2 groups. Cuff integrity during the last follow-up period was assessed with magnetic resonance imaging, and the failure rate was calculated. In addition, the postoperative foreign body reaction was investigated in the study group. RESULTS: In both groups, significant postoperative improvements were seen in acromiohumeral interval, clinical scores, ROM in anterior flexion, and isometric muscle strength in abduction, external rotation, and internal rotation (P < .001 for all). The failure rate of the study group was 12.8% (6 patients) and that of the control group was 25.9% (7 patients). No significant differences were noted between the 2 groups on any of the data findings, even regarding the failure rate. Foreign body reactions in the early period were found in 3 patients, although these spontaneously disappeared within 3 months. CONCLUSION: Patients who underwent PGA patch reinforcement for MA-ARCR when the footprint could not be completely covered had clinical results similar to isolated MA-ARCR when the footprint could be covered. Both procedures resulted in significant improvement in symptoms and function compared with preoperatively.

In Vitro Safety and Quality of Magnetically Labeled Human Mesenchymal Stem Cells Preparation for Cartilage Repair.

IMPACT STATEMENT: This study is very important for a preclinical assessment of the safety and quality of magnetically labeled mesenchymal stem cells (MSCs) for use in cartilage repair. The findings of this study show that magnetic labeling with an appropriate density of magnetic particles has no harmful effects on the safety and quality of MSCs.