Introduction. Total shoulder arthroplasty is the fastest growing joint replacement in recent years, with projected compound annual growth rates of 10% for 2016 through 2021 – higher than those of both the hip and knee combined. Reverse total shoulder arthroplasty (RTSA) has gained particular interest as a solution for patients with irreparable massive rotator cuff tears and failed conventional shoulder replacement, for whom no satisfactory intervention previously existed. As the number of indications for RTSA continues to grow, so do implant designs, configurations, and fixation techniques. It has previously been shown that continuous implant migration within the first two years postoperatively is predictive of later loosening and failure in the hip and knee, with aseptic loosening of implant components a guaranteed cause for revision in the reverse shoulder. By identifying implants with a tendency to migrate, they can be eliminated from clinical practice prior to widespread use. The purpose of this study is to, for the first time, evaluate the pattern and magnitude of implant component migration in RTSA using the gold standard imaging technique radiostereometric analysis (RSA). Methods. Forty patients were prospectively randomized to receive either a cemented or press-fit humeral stem, and a glenosphere secured to the glenoid with either autologous bone graft or 3D printed porous titanium (Aequalis Ascend Flex, Wright Medical Group, Memphis, TN, USA) for primary reverse total shoulder arthroplasty. Following surgery, partients are imaged using RSA, a calibrated, stereo x-ray technique, at 6 weeks (baseline), 3 months, 6 months, 1 year, and 2 years. Migration of the humeral stem and glenosphere at each time point is compared to baseline. Preliminary results are presented, with 15 patients having reached the 6-month time point by presentation. Results. Implant migration of ten participants at the 3-month time point is presented. Maximum total point motion (MTPM) is a measure of translation and rotation of the point on the implant that has moved the most from baseline. Average MTPM ± SD of the humeral stem is 1.18 ± 0.65 mm and 0.98 ± 0.46 mm for press-fit (n = 6) and cemented (n = 4) stems, respectively; and 0.25 ± 0.09 mm and 0.47 ± 0.24 mm for bone graft (n = 4) and porous titanium (n = 6) glenosphere fixations, respectively, at the 3-month time point. Conclusion. There is a trend towards increased migration with the use of press-fit humeral stems and porous titanium glenosphere fixation, though no conclusions can be made from the current sample size. Further, though differences in migration magnitude may be observed at early postoperative time points, it is expected that all fixation techniques will show stability from 1 to 2 years postoperatively

Purpose. Chronic massive rotator cuff tears are challenging to repair completely because of the development of tendon retraction with inelasticity, muscle atrophy and fatty infiltration. The objective of this study was to investigate the clinical outcome and MRI findings after arthroscopic superior capsule reconstruction (ASCR) for symptomatic irreparable rotator cuff tears. Methods. From 2011 to 2013, 12 shoulders in 12 consecutive patients (mean, 70.8 years) with irreparable massive rotator cuff tears underwent ASCR using fascia lata. We used suture anchors to attach the graft medially to the glenoid superior tubercle and laterally to the greater tuberosity as same technique by Mihata et al. We added side-to-side sutures between the graft and infraspinatus tendon and between the graft and residual anterior supraspinatus/subscapularis tendon to improve force coupling. Physical examination, clinical rating system, and magnetic resonance imaging (MRI) were performed before surgery; at 6 and 12 months after surgery; and 6 months thereafter. Average follow-up was 19.1 months (12 to 28 months) after surgery. We assessed patients preoperatively by using the scoring systems of the shoulder index of the American Shoulder and Elbow Surgeons (ASES), the Japanese Orthopaedic Association, and the University of California, Los Angeles. Results. Mean active elevation increased from 59° to 111° significantly and external rotation increased from 28 to 33. The average preoperative scores were 16.0 points by ASES, 48.0 points by JOA, and 10.8 points by UCLA. Average clinical outcome scores all improved significantly after ASCR at the final follow-up (ASES, 73.3 points; JOA, 73.7 points; UCLA, 22.7 points). There was surgical complication as infection. Although infection was controlled by arthroscopic irrigation, the transplanted tendon was absorbed, and preoperative conditions did not functionally improve. Five patients had graft tear during follow-up. Postoperative active range of motion in the healed patients was significantly greater than in the unhealed patients who had graft tears. Conclusions. ASCR restored superior glenohumeral stability and function of the shoulder joint with irreparable rotator cuff tears compared to preoperative function in the cases without postoperative complications. However ratio of graft tears were 50% and clinical results of these cases were not improved sufficiently