# Errors in implant orientation estimation in novice vs. experienced surgeons during reverse shoulder arthroplasty for a superior glenoid wear pattern

## TL;DR

This study compares how accurately novice and experienced surgeons estimate glenoid implant orientation during shoulder surgery, finding significant errors in both groups.

## Contribution

The study reveals that both novice and experienced surgeons make large errors in estimating glenoid implant orientation during surgery.

## Key findings

- Visual assessments of glenoid baseplate orientation showed poor to fair correlation with 3D CT measurements.
- Experienced surgeons had larger errors in inclination (up to 20°) compared to novices.
- Novice surgeons made significant errors in supero-inferior center of rotation offset (up to 8 mm).

## Abstract

Glenoid baseplate orientation in reverse shoulder arthroplasty influences clinical outcomes, complications, and failure rates. This study aimed to determine novice and experienced shoulder surgeon’s ability to accurately characterize glenoid component orientation in an intraoperative scenario.

Glenoid baseplates were implanted in 8 fresh frozen cadavers by novice surgical trainees. Glenoid baseplate version, inclination, augment rotation, and superior-inferior center of rotation offset were then measured using in-person visual assessments by novice and experienced shoulder surgeons immediately after implantation. Glenoid orientation parameters were then measured using 3-dimensional (3D) computed tomography (CT) scans with digitally reconstructed radiographs (DRRs) by 2 independent observers with a 1-month time interval between repeat measurements. Bland-Altman plots were produced to determine the accuracy of glenoid orientation using standard intraoperative assessment compared to postoperative 3D CT scan results. Interclass correlation coefficients were produced for measurements, rated as 0.01-0.39 poor, 0.40-0.59 fair, 0.60-0.74 good, and 0.75-1.00 excellent.

Visual assessment of glenoid baseplate orientation showed “poor” to “fair” correlation to 3D CT DRR measurements for both novice and experienced surgeon groups for all measured parameters. There was a large discrepancy between intraoperative visual assessments and 3D CT DRR measurements for all parameters. Errors in visual assessment of up to 20° of inclination by experienced surgeons (P = .03), and 8 mm supero-inferior center of rotation offset by novice surgeons (P = .50) occurred. Experienced surgeons had greater measurement error than novices for all measured parameters.

Intraoperative measurement errors in glenoid placement are present for both inexperienced and experienced surgeons. Kinesthetic input during implantation may improve orientation understanding.