Summary

In this study, preoperative AHI and Goutallier measurements in rTSA performed slightly superior to aTSA in predictive ability, however, none of the optimal cut-points crossed the AUC threshold of 0.700, indicating an overall inability to achieve meaningful predictions of PROMs.

Abstract

Objectives: The study assessed the value of preoperative acromiohumeral interval (AHI) and Goutallier measurements using multiple imaging modalities for predicting significant improvements in common patient reported outcome measures (PROMs) following anatomic (aTSA) and reverse total shoulder arthroplasty (rTSA). Specifically, preoperative measurements were assessed for their ability to predict achievement of the minimal clinically important difference (MCID) and substantial clinical benefit (SCB) for the American Shoulder and Elbow Surgeons (ASES) scores at different time points post-operatively.

Methods

Patients who underwent aTSA and rTSA were identified from our institution’s shoulder arthroplasty registry and included if they had computed tomography (CT), magnetic resonance imaging (MRI), and x-ray (XR) within six months of surgery and complete ASES scores. Two raters independently measured AHI using XR, MRI, and CT and assigned a Goutallier score of the supraspinatus muscle using MRI and CT. Intraclass correlation coefficients (ICCs) were calculated for each measurement and imaging modality. Cut-point analysis using the Youden index was performed for each radiologic measurement to determine their ability to predict achievement of the MCID (13.6 pts) and SCB (31.5 pts) for ASES at 2 years. Additional logistic regression was performed as needed.

Results

199 patients (132 aTSA, 67 rTSA) were included. ICC values demonstrated moderate to strong agreement across modalities. Rates of MCID and SCB achievement did not differ significantly between aTSA and rTSA. Patients who underwent rTSA with AHI >6mm on CT (p=0.018) and >7mm on XR (p=0.044) were significantly more likely to achieve the MCID at 1 year. Neither of these associations were significant at 2 years. Patients who underwent rTSA with AHI >6mm on MRI were significantly more likely to achieve SCB at 1 year (p=0.031), but similarly this did not persist at 2 years. In cut-point analysis, all Area Under the Curve (AUC) measurements were less than 0.700, indicating poor predictive ability. When predicting MCID at 2 years in aTSA, a Goutallier score of 0.5 on MRI (AUC=0.667) and CT (AUC=0.649) were most predictive. When predicting MCID at 2 years in rTSA, Goutallier scores of 1.5 on CT (AUC=0.663) and MRI (AUC=0.624) were most predictive. For predicting SCB at 2 years in aTSA, only two AUCs were greater than 0.5 – AHIs of 8.35mm on XR (AUC=0.505) and 8.00mm on CT (AUC=0.548). For predicting SCB at 2 years in rTSA, a Goutallier score of 2 on CT had the greatest AUC (0.642) followed by AHI of 4.7mm on CT (AUC=0.639).

Discussion

In this study, preoperative AHI and Goutallier measurements in rTSA performed slightly superior to aTSA in predictive ability. However, none of the optimal cut-points crossed the AUC threshold of 0.700, indicating an overall inability to achieve meaningful predictions of PROMs. While an AHI threshold of 6mm on MRI and CT and 7mm on XR demonstrated an ability to discriminate differences for achieving significant clinical outcomes at 1-year for rTSA, this did not persist at 2 years. It remains important to consider factors beyond preoperative AHI and Goutallier measurements to improve long-term clinical outcome predictions in shoulder arthroplasty.