Abstracts from the Ases 2017 Open Meeting/specialty Day

S FROM THE ASES 2017 OPEN MEETING/SPECIALTY DAY Paper #1 ± SUBSCAPULARIS SPARING TOTAL SHOULDER ARTHROPLASTY: A PROSPECTIVE, DOUBLE BLINDED, RANDOMIZED CLINICAL TRIAL Young W. Kwon, MD, PhD, Joseph D. Zuckerman, MD, NYU Hospital for Joint Diseases, Department of Orthopaedic Surgery, New York, New York, USA Introduction: While total shoulder arthroplasty (TSA) is generally associated with good to excellent outcomes in majority of patients, the integrity and the function of the subscapularis tendon may be compromised after the procedure and lead to inferior outcomes. Therefore, the efficacy of a subscapularis sparing TSA procedure was evaluated in a prospective, double blinded, randomized study. Methods: With IRB approval, patients with end stage osteoarthritis of the shoulder were enrolled into a prospective clinical trial from 2010 to 2014. These patients were randomized into two groups. Group 1 patients were treated with TSA using the subscapularis sparing surgical approach in which the prosthesis was inserted entirely through the rotator interval without violating the subscapularis tendon (SPARING). Group 2 patients were treated with TSA using the standard surgical approach with subscapularis tenotomy (STANDARD). Both the patient and the evaluators remained “blinded” to the surgical approach throughout the study period. Minimum 2 year outcome data was collected using the visual analog score (VAS) for pain and the American Shoulder and Elbow Surgeon (ASES) outcome score. Results: A total of 107 shoulders were enrolled (57 SPARING, 50 STANDARD). Of these, 14 TSA procedures could not be completed as initially randomized. In addition, 3 patients expired (unrelated to the procedure), 7 patients withdrew from the study, and 2 moved away. Of the remaining 81 patients, 2 year outcome data could not be collected from another 11. Thus, complete 2 year outcome data was collected from 32 SPARING and 38 STANDARD patients at an average follow up of 31.1 and 34.4 months, respectively. The ASES score and VAS for the SPARING group improved significantly from 29.3 ± 12.5 and 6.6 ± 2.1 to 82.6 ± 18.8 and 1.6 ± 2.2 (mean ± standard deviation). Similarly, the ASES score and VAS for the STANDARD group also improved significantly from 32.8 ± 16.1 and 6.3 ± 2.4 to 87.1 ± 14.5 and 1.0 ± 1.7. In comparison to their pre-operative status, the ASES score for the SPARING and the STANDARD groups improved 53.9 ± 22.3 and 54.0 ± 18.7 points, respectively. The VAS for the SPARING and the STANDARD groups also improved 5.1 ± 3.1 and 5.3 ± 2.5 points, respectively. Neither of these differences between the SPARING and the STANDARD groups reached statistical significance. Complication profiles were similar in both groups with 3 in the SPARING group and 2 patients in the STANDARD group requiring revision surgery during the study period. Discussion: At a short term follow up, the outcome of TSA using the subscapularis sparing surgical approach was similar to that after TSA using the standard surgical approach. Future studies with longer follow up of these patients will be required to document the potential benefits of this surgical technique. Paper #2 ± FINITE ELEMENT ANALYSIS OF GLENOID-SIDED LATERALIZATION IN REVERSE SHOULDER ARTHROPLASTY Patrick J. Denard, MDa,b, Evan S. Lederman, MDc,d, Bradford O. Parsons, MDe, Anthony A. Romeo, MDf, Southern Oregon Orthopedics, Medford, Oregon, USA; Department of Orthopaedic & Rehabilitation, Oregon Health & Science University, Portland, Oregon, USA; The Orthopedic Clinic Association, Phoenix, Arizona, USA; Department of Orthopedic Surgery, Banner University Medical Center, Phoenix, Arizona, USA; Leni and Peter W. May Department of Orthopaedic Surgery at the Icahn School of Medicine at Mount Sinai, New York, New York, USA; Rush University Medical Center, Chicago, Illinois, USA Background: The purpose of this study was to evaluate glenoidsided lateralization in reverse shoulder arthroplasty (RSA) and compare bony and prosthetic lateralization. The hypothesis was that stress and displacement would increase with progressive bony lateralization and be lower with prosthetic lateralization. Materials and Methods: A 3D finite element analysis (FEA) was performed on a commercially available RSA prosthesis. Stress and displacement were evaluated at baseline and following 5, 10, and 15 mm of bony or prosthetic lateralization. Additional variables included glenosphere size, baseplate orientation, and peripheral screw orientation. Results: Maximum stress for a 36 mm glenosphere without bone graft increased by 137% for the 5 mm graft, 187% for the 10 mm graft, and 196% for the 15 mm graft. Likewise, displacement progressively increased with increasing graft thickness. Stress and displacement were reduced with a smaller glenosphere, inferior tilt of the baseplate, and divergent peripheral screws. Compared to bony lateralization, stress was lower with prosthetic lateralization through the glenosphere or baseplate. Displacement with 5 mm of bony lateralization reached recommended maximal amounts for osseous integration, whereas this level was not reached until 10 to 15 mm of prosthetic lateralization. Conclusion: Baseplate stress and displacement in an FEA model is lower with a smaller glenosphere, inferior tilt, and divergent screws. Bony lateralization increases stress and displacement to a greater degree than prosthetic lateralization. It appears that at least 10 mm of prosthetic lateralization is mechanically acceptable during RSA, but only 5 mm of bony lateralization is advised (Figs. 1 and 2). Saturday, March 18, 2017, San Diego, CA Figure 1 Stress and lateralization.