Improved Glenoid Component Screw Placement for Reverse Shoulder Arthroplasty by Surgeon Designed Patient-specific Instrumentation versus Conventional Method : A Comparative Study

Abstract

Introduction: Glenoid component fixation in reverse shoulder arthroplasty (RSA) is critical to prevent loosening. Long angle stable screws in the superior and inferior glenoid bone is the preferred method. However, this can be technically challenging especially in patients with smaller glenoid dimensions. Here, we assess the efficacy of a surgeon-designed three dimensional (3D)-printed patient-specific instrumentation (PSI) in enhancing the accuracy of screw placement compared with conventional instrumentation. Methods: Multicentre retrospective comparative study of RSA was performed using conventional instrumentation against a surgeon designed, in-house produced 3D-printed PSI jigs for glenoid guide pin orientation and superior-inferior screw placement. The outcome measurements were screw length attainable for superior and inferior screw placement, operating time, and complications. Results: Twenty-nine RSAs were performed with 11 using PSI and 18 with conventional instrumentation. Average anteroposterior glenoid diameter was 27.1 mm (range, 24.9-29.2 mm) in the conventional group and 23.6 mm (range, 21.6-29.3 mm) in the PSI group. Superior and inferior screw lengths were significantly longer by a mean of 7.70 mm and 10.58 mm, respectively in the PSI group compared with conventional group (p=0.02, 95% confidence interval [CI]=1.13-14.3; p=0.01, 95% CI=3.34-17.8). The mean superior screw lengths were 46.2 mm (range, 36-48 mm) and 38.5 mm (range, 20-48 mm) for PSI and conventional instrumentation, respectively, while the mean inferior screw lengths were 46.2 mm (range, 36-48 mm) in PSI and 35.6 mm (range, 20-48 mm) in conventional instrumentation. Conclusion: Significantly longer screws were placed using PSI. Long screws were reliably placed even in small glenoids with anteroposterior diameter of <25 mm. Routine use of PSI can improve placement of screws in RSA.