Three-dimensional analysis of baseplate screw penetration in reverse total shoulder arthroplasty: risk of iatrogenic suprascapular neuropathy by screw violation

Abstract Background Baseplate screws have been suggested to be a possible cause of suprascapular neuropathy after reverse total shoulder arthroplasty (RTSA). Three-dimensional (3D) analyses of screw penetration and confirmation of its clinical impacts are relevant. The study aims to investigate the association between the penetration and the clinical outcomes. Materials and Methods Eighty-two patients that received RTSA for a massive rotator cuff tear, cuff tear arthropathy, or osteoarthritis with rotator cuff tear were retrospectively enrolled. They were followed up for a minimum of 12 months and all underwent computed tomography (CT) at 1-year postoperatively. Lengths of superior and posterior baseplate screws were documented. Postoperative CT images were subjected to 3D analysis to determine whether superior or posterior screws penetrated the glenoid vault and where they penetrated into, and screw-to-nerve distances were measured to estimate risks of screw nerve violation and iatrogenic suprascapular neuropathy. Patients with any screw Results Mean lengths of superior and posterior screws were 28 ± 4 mm and 18 ± 3 mm, respectively. Penetration was detected for 13% of superior screws and 64% of posterior screws. Sixty-three percent of penetrating superior screws and 5% of penetrating posterior screws were Conclusion Twelve percentage of patients that received RTSA were assessed to be at high risk of iatrogenic suprascapular neuropathy by baseplate screw penetration. However, the clinical outcomes of RTSA at a minimum follow-up of 1 year were similar in high and lower risk groups.