Three-Dimensional Computed Tomography Analysis of Pathologic Correction in Total Shoulder Arthroplasty Based on Severity of Preoperative Pathology.

BACKGROUND: The purpose of this study was to quantify correction of glenoid deformity and humeral head alignment in anatomic total shoulder arthroplasty (TSA) as a function of preoperative pathology (modified Walch classification) and glenoid implant type in a clinical cohort using three dimensional (3D) computed tomography (CT) analysis.

METHODS: Patients undergoing anatomic TSA with a standard glenoid (SG) (n=110) or posteriorly stepped augmented glenoid (AG) (n=62) component were evaluated with preoperative CT and a postoperative CT within 3 months of surgery. Glenoid version, inclination, and medial-lateral (ML) joint line position, and humeral head alignment were assessed on both CT scans, with preoperative to postoperative changes analyzed relative to pathology and premorbid anatomy based on modified Walch classification and glenoid implant type.

RESULTS: On average, correction to premorbid ML joint line position was significantly less in A2 compared to A1 glenoids (-2.3±2.1mm versus 1.1±0.9mm, p<0.001). Correction to premorbid version was not different between B2 glenoids with AG components and A1 glenoids with SG components (-1.7±6.6° versus -1.0±4.0°, p=0.57), and premorbid ML joint line position was restored on average in both groups (0.3±1.6mm versus 1.1±0.9mm, p=0.006). Correction to premorbid version was not different between B3 glenoids with AG components and A1 glenoids with SG components (-0.6±5.1° versus -1.0±4.0°, p=0.72), but correction relative to premorbid ML joint line position was significantly less in B3 glenoids with AG components compared to A1 glenoids with SG components (-2.2±2.1mm versus 1.1±0.9mm, p<0.001). Postoperative humeral glenoid alignment was not different in any group comparisons.

DISCUSSION: In cases with posterior glenoid bone loss and retroversion (B2, B3 glenoids), an AG component can better correct retroversion and glenoid ML joint line position compared to a SG component, with correction to premorbid version comparable to an A1 glenoid with a SG component. However, restoration of premorbid ML joint line position may not always be possible with SG or AG components in cases with more advanced central glenoid bone loss (A2, B3 glenoids). Further follow-up is needed to determine the clinical consequence of these findings.