BACKGROUND:
Accurate placement of the glenoid baseplate is an important technical goal of reverse total shoulder arthroplasty (RSA). The use of computer navigated instrumentation has been shown to improve the accuracy and precision of intraoperative execution of preoperative planning. The purpose of this study was to compare early clinical outcomes of patients undergoing navigated reverse total shoulder arthroplasty versus a non-navigated matched cohort.

METHODS:
A retrospective review of a prospectively-collected shoulder arthroplasty database was used to identify 113 patients from a single institution who underwent navigated primary RSA with a minimum 2-year follow-up. A matched cohort of 113 non-navigated RSA was created based on gender, age, follow-up, and preoperative diagnosis. Preoperative and postoperative range of motion, functional outcome scores, and complications were reported.

RESULTS:
226 shoulders with mean age of 71 years were evaluated after navigated (113) or non-navigated (113) RSA. Mean follow-up was 32.8 months (range 21-54 months). At final postoperative follow-up the navigated group had better active forward elevation (135o vs 129o, p=0.023), active external rotation (39o vs 32o, p=0.003), and Constant scores (71.1 vs 65.5, p=0.003). However, when comparing improvements from the preoperative state, there were no statistically significant difference in range of motion or functional outcome scores between groups. Complications occurred in 1.8% (2) of patients undergoing navigated RSA compared to 5.3% (6) in the non-navigated group (p=0.28). Scapular notching (3.1% vs 8.0%, p=0.21) and revision surgery (0.9% vs 3.5%, p=0.37) was more common in non-navigated shoulders.

CONCLUSION:
At early follow-up, navigated and non-navigated RSA yielded similar rates of improvement in range of motion and functional outcome scores. Notching and reoperation was more common in non-navigated shoulders, but did not reach statistical significance. Longer follow-up and larger cohort size is needed to determine if intraoperative navigation lengthens the durability of RSA results and reduces the incidence of postoperative complications.





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