JSES - 2026-06-01 - Journal Article; Multicenter Study; Randomized Controlled Trial; Comparative Study
Patient-specific instrumentation vs. a free-hand technique for glenoid baseplate and peripheral screw placement in reverse total shoulder arthroplasty using the Exactech implant system: a multicenter randomized controlled trial.
Kim H, Lee H, Lim TK, Kim SH, Lee HJ, Jeong HJ, Shon MS, Jeon IH, Koh KH
Topics
Key Takeaway
PSI did not improve glenoid baseplate positioning versus free-hand technique (version error 5°±5° vs. 5°±5°), but significantly reduced clinically relevant peripheral screw angular errors, including anterior SI gap errors (11.3% vs. 43.4%).
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Summary
This multicenter superiority RCT across 7 tertiary centers randomized patients ≥65 years undergoing primary rTSA with the Exactech system 1:1 to PSI versus free-hand glenoid baseplate placement, with CT-based deviation from preoperative plan as the primary outcome. Baseplate version, inclination, and positional offset were statistically equivalent between groups. PSI significantly improved peripheral screw accuracy, reducing clinically relevant anterior SI gap errors from 43.4% to 11.3% and superior SI gap errors from 41.5% to 20.8%.
Key Limitation
The study reports only imaging-based accuracy endpoints with no clinical outcomes, complication rates, or implant survival data, making it impossible to determine whether the statistically significant improvements in screw placement translate to reduced SSN injury, baseplate failure, or functional benefit.
Original Abstract
BACKGROUND
Accurate positioning of the glenoid baseplate and peripheral screws is critical in reverse total shoulder arthroplasty (rTSA). Patient-specific instrumentation (PSI) has been introduced to improve surgical accuracy, but its benefits over conventional free-hand techniques remain uncertain. This study aimed to evaluate the accuracy of glenoid baseplate and peripheral screw placement between PSI-assisted and conventional free-hand rTSA.
METHODS
We conducted a prospective, multicenter, parallel-group, single-blinded, superiority randomized controlled trial across 7 tertiary centers between March 2022 and December 2024. Patients aged ≥65 years undergoing primary rTSA were randomized 1:1 to PSI or free-hand group through a centralized web-based electronic case report form. No cross-over occurred and all analyses were performed on an intention-to-treat basis. A standardized implant system (Exactech, Gainesville, FL, USA) was used in all cases. The primary outcome was the proportion of patients with postoperative computed tomography-based deviation error from preoperative planning, including version (≥5°), inclination (≥5°), or position offset (≥2.5 mm) errors. The secondary outcomes included continuous deviation values and accuracy of peripheral screw placement (anteroposterior [AP] gap, superoinferior (SI) gap, and length gap deviations). Effect sizes with 95% confidence intervals (CIs) were reported.
RESULTS
Of 106 patients, 53 were included in the PSI and free-hand groups each. Baseline demographics and clinical characteristics were comparable between the groups. Baseplate positioning was similar between the groups, with version error 5 ± 5° vs. 5 ± 5°, inclination error 6 ± 5° vs. 5 ± 4° (mean difference +0.9°, 95% CI -0.8 to +2.6; P = .309), and positional offset 3 ± 2 mm vs. 4 ± 2 mm (mean difference -0.3 mm, 95% CI -1.1 to +0.5; P = .496). Conversely, PSI significantly improved peripheral screw placement accuracy, including AP gap (-1 ± 3° vs. 1 ± 6°; mean difference -1.9°, 95% CI -3.7 to -0.1; P = .041), SI gap (-2 ± 4° vs. 1 ± 6°; mean difference -2.7°, 95% CI -4.7 to -0.8; P = .008), superior length gap (1 ± 6 mm vs. -2 ± 8 mm; mean difference +3.0 mm, 95% CI 0.2 to 5.8; P = .039), and inferior AP gap (1 ± 6° vs. -3 ± 6°; mean difference +4.2°, 95% CI 2.0 to 6.4; P < .001). Additionally, clinically relevant errors (>5°) were significantly less frequent in the PSI group for anterior (11.3% vs. 43.4%; P < .001) and superior (20.8% vs. 41.5%; P = .035) SI gap.
CONCLUSION
In primary rTSA, PSI did not improve glenoid baseplate positioning compared to the free-hand technique but significantly enhanced the accuracy of peripheral screw placement.