Suprascapular nerve injury after reverse total shoulder arthroplasty: correlation with screw out of vault penetration and functional situation: prospective study.

BACKGROUND: Baseplate screws have been suggested as a possible cause of suprascapular neuropathy after reverse total shoulder arthroplasty. This study aims to investigate the association between screw penetration out of the vault, electromyographic study, and the clinical outcomes. METHODS: A total of 31 patients who underwent reverse total shoulder arthroplasty for cuff tear arthropathy were prospectively enrolled. They were followed up for a minimum of 24 months. All patients underwent computed tomography 6 months postoperatively to determine the extraosseous position of the screws (perforation of the second bone cortex and protrusion into the supra- or infraspinatus fossa). Electrodiagnostic evaluation was performed preoperatively and postoperatively to stablish any relation between cortex perforation of the screw and suprascapular nerve (SSN) injury. Clinical outcomes pre- and postoperatively (Constant score, ranges of motion, and visual analog scale) of patients with and without documented injury were recorded. RESULTS: A total of 14 patients (45.2%) had an abnormal preoperative SSN electrodiagnostic study (chronic or disuse injuries), and 6 patients (19.4%) had an abnormal postoperative study (acute injury). Of the 6 patients, 2 cases appeared over the pre-existing lesion and 4 appeared over an intact preoperative nerve, all of them affecting the infraspinatus branch of the SSN. Perforation of the second cortex was detected for 60% of superior screws and 40% of posterior screws. The mean lengths of the superior and posterior screws were 30 and 18.2 mm, respectively. Patients with screw perforation of the second cortex were assessed as having a high risk of nerve injury (40% vs. 9.5%). CONCLUSIONS: Preoperative SSN injuries do not have a significant clinical impact and do not predispose to an acute postoperative SSN lesion. The Constant score and visual analog scale score for patients with acute SSN injuries were not statistically different from those without SSN injury. The extraosseous position of the screw increases the probability of an SSN injury to 31%. This risk is higher with the posterior screw, which leads us to question whether it is really necessary to use it.

Glenoid vault perforation in total shoulder arthroplasty: Do we need computer guidance?

The proliferation of computer 3D simulation and computer-generated guides is aimed at minimizing perforation of the glenoid vault by glenoid pegs in shoulder arthroplasty, based on assumptions that perforation leads to worse outcomes by component loosening and potential failure. We evaluated outcomes of glenoid peg perforation testing the assumption that perforation produces worse results. Eighty-three shoulders underwent shoulder arthroplasty with pegged hybrid fixation (bone-ingrowth flanged central glenoid peg and peripheral cemented pegs) without precision signal injector guides or use of 3D planning software. Outcomes were determined by American Shoulder and Elbow Score and Oxford Shoulder Score. Fine slice CT determined the presence of vault perforation and the extent of lucent lines at the prosthesis-bone interface and bony morphology of the vault perforation. Follow-up was 46.7 months (24-99). Seven shoulders (8%) demonstrated perforation of glenoid vault. Bony ingrowth and cortical overgrowth occurred despite perforation, with no clinically significant differences in clinical or radiological outcomes in shoulders with and without glenoid vault perforation. None of these patients underwent revision surgery. Despite not utilizing computer planning and/or guides, 92% of implants did not perforate the glenoid vault. However, glenoid vault perforation in our series produced excellent outcomes with no increased risk of revision as a result of glenoid vault perforation.