Clinical outcomes based on planned glenoid baseplate retroversion in reverse total shoulder arthroplasty

Background

While surgeons attempt to correct the baseplate version of a reverse total shoulder arthroplasty (rTSA), clinical outcomes based on the planned final version remain unknown. The purpose of this study is to determine the clinical and radiographic outcomes of rTSA based on the planned final version of the baseplate. Our hypothesis is that increasing component retroversion will not affect outcomes.

Methods

All primary rTSA patients in a multicentered international registry with a 2-year minimum follow-up implanted with computer navigation were included, except fracture and revision indications. A single medialized glenoid/lateralized humerus rTSA implant system was used with a standard or augmented baseplate. Patients were stratified by baseplate type and final planned baseplate version into 2 cohorts: 0°-5° (Group 1) or 6°-15° (Group 2) of retroversion. Demographics, radiographic outcomes, range of motion, and patient-reported outcome scores were compared between groups using Welch’s t-test and Fisher’s Exact test.

Results

Five hundred and thirty-five patients (307 females/226 males/2 unknown) were identified, with a mean follow-up of 30 months. Demographics were similar between the cohorts. The mean native and final retroversion was 9.0° and 1.5° in Group 1 and 16.3° and 8.6° in Group 2, respectively. Preoperatively, 72% of patients were 6°-15° retroverted. Postoperatively, 73% of patients were 0°-5° retroverted and 27% were 6°-15°, with 97% of patients having less than or equal to 10° of planned baseplate retroversion. Without stratifying for baseplate types, there were no clinically significant differences between the cohorts with regards to postoperative pain, range of motion, or patient-reported outcome scores, except for abduction and internal rotation greater in the 6°-15° and 0°-5° cohorts, respectively. Scapular notching was low (7% vs. 8%) and less than reported without computer navigation. Complication and revision rates were similar between the 2 groups. Patient satisfaction was high (much better/better, 94% vs 95%) and not significantly different between the 2 groups.

Discussion

There were no significant clinical differences between cohorts. This study demonstrates that favorable outcomes are achieved with a planned final baseplate version of less than 15° retroversion, with few differences between 0°-5° and 6°-15°. rTSA is forgiving enough such that one may plan to correct preoperative retroversion to less than 15° postoperatively in lieu of targeting postoperative version between 0°-5° for patients with higher native retroversion, potentially requiring less eccentric reaming especially when combined with other corrective measures.