Preoperative acromiohumeral interval may predict early achievement of clinically meaningful outcomes in reverse shoulder arthroplasty patients: a retrospective review of preoperative imaging studies

Hypothesis The aim of this study was to examine the predictive value of preoperative acromiohumeral interval (AHI) and Goutallier grade across multiple imaging modalities on patient-reported outcomes following both anatomic total shoulder arthroplasty (aTSA) and reverse total shoulder arthroplasty (rTSA). We hypothesized that a higher AHI and lower Goutallier grades preoperatively would predict better patient reported outcome measures following both aTSA and rTSA. 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 6 months of surgery and complete American Shoulder and Elbow Surgeons scores at 2 years. Two raters independently measured AHI on all three imaging modalities and assigned a Goutallier grade for supraspinatus muscle quality using MRI and CT. Logistic regression and cut-point analysis using the Youden index was performed for each radiographic measurement to determine their ability to predict achievement of the minimal clinically important difference (MCID) and substantial clinical benefit (SCB) for American Shoulder and Elbow Surgeons. Results A total of 199 patients (132 aTSA, 67 rTSA) were included. Interclass correlation coefficient values demonstrated moderate to strong agreement across modalities. Rates of MCID and SCB achievement did not differ significantly between the aTSA and rTSA groups. Patients who underwent rTSA with AHI >6 mm on CT ( P = .018) and >7 mm on XR ( P = .044) were significantly more likely to achieve the MCID at 1 year. Patients who underwent rTSA with an AHI >6 mm on MRI were significantly more likely to achieve SCB at 1 year ( P = .031). These significant associations did not persist at 2 years. No threshold for AHI or Goutallier was significantly associated with MCID or SCB in aTSA at any timepoint. In cut-point analysis, all area under the curve measurements were less than 0.700, indicating poor predictive ability. Conclusion The present study demonstrates that an AHI threshold of 6 mm on MRI and CT and 7 mm on XR may predict the achievement of significant clinical outcomes at 1-year for rTSA. These findings suggest that the rotator cuff may play a role in expediting the recovery process for patients undergoing rTSA. Despite this, however, there are no reliable optimal cut-points for predicting the achievement of meaningful clinical outcomes following aTSA and rTSA using AHI measurements and Goutallier grades. Factors beyond standard radiologic measurements should be considered when prognosticating long-term clinical outcomes following shoulder arthroplasty.