Abstract
Objectives:
The Goutallier grading scheme is widely used to assess the chronicity of rotator cuff (RC) tears, predict the likelihood of surgical repair, and provide prognostic information to the expected functional outcomes associated with repair. The limitations of the Goutallier grading scheme are well described and pertain to low rates of interobserver reliability, an inability to distinguish between extramuscular fat replacement and intramuscular fat infiltration (Fig. 1), and an exclusive focus on the supraspinatus. Therefore, a novel 3D magnetic resonance imaging (MRI)-based assessment has been designed to offer a more comprehensive characterization of the chronicity and severity of RC pathology. The Volumetric Score (VS) consists of three measurements of the RC unit: 1. Muscle Size Score (MSS), representing an average z-score of every patient’s normalized muscle volume compared to a control population; 2. Relative Contribution Score (RCS), using the weighted average of each of the RC muscle’s relative volume to produce a single score for all RC muscles; and 3. Fat Infiltration Score (FIS), averaging fat infiltration for each RC muscle weighted by all RC muscles’ relative volume contribution.
Objectives
Describe the correlation between the Goutallier grade and VS for supraspinatus muscle changes in RC tears,
Characterize the chronicity of RC tears in terms of muscle changes using the collective VS measurements, and
Compare the Goutallier grade and VS to determine which method most closely corresponds with preoperative functional patient reported outcomes (PROs).
Methods:
Patients with a history of primary arthroscopic RC repair performed at a single institution and preoperative MRI available for 3D assessment were included. For the MRI-based analysis, the four RC muscles, their respective intramuscular fat, and three upper extremity bones (scapula, clavicle and humerus) were segmented from T1 MRI scans using 3D Slicer and volumized. Segmentation engineers were blinded to all other preoperative, patient-specific variables. To account and normalize for variation in patient sizes, muscle volumes were divided by scapula volume and compared to age-matched controls. Measurements included: (1) muscle size via the MSS; (2) relative muscle volume via the RCS; and (3) intramuscular fat infiltration via the FIS. For each of the four RC muscles, three volumetric measures were obtained (MSS, RCS and FIS), resulting in a total of 12 volumetric scores. All MRIs were assessed independently by two fellowship trained Orthopaedic surgeons according to the Goutallier grading scheme. Patients’ preoperative function was assessed using the Patient-Reported Outcomes Measurement Information System (PROMIS) instrument. PROMIS physical function (PF) and pain interference (PI) T-scores were recorded. A univariate and multivariate linear regression was performed to analyze the correlation between MSS, RCS and FIS with the Goutallier grades on evaluation of the supraspinatus. A linear regression was performed to compare the Goutallier grades with preoperative PROMIS PF and PI T-scores, and a multivariate backwards linear regression model was used to determine which of the 12 VS measurements most closely correlated with PROMIS PF and PI preoperative PROs (Fig. 2).
Results:
Eighty-seven patients were included in the final analysis. The mean age was 54.8 ± 8.6 years with 56 male (64%) and 31 (36%) females. Goutallier grades ranged from grade 0 (n=36, 41.3%), grade 1-2 (n=45, 51.7%) and grade 3-4 (n=6, 6.89%). The univariate linear correlation coefficient (r) demonstrated a strong negative correlation between the supraspinatus MSS (r=-0.73, p<0.001) and RCS (r=-0.73, p<0.001) when compared to the Goutallier grade, while the FIS score (r=0.24, p=0.03) had a moderate positive correlation with the Goutallier grade (Fig. 3). On multivariate linear analysis of all three supraspinatus volumetric measurements, the RCS (p<0.001) most strongly correlated with the Goutallier grade (r=0.73, p<0.001). Very weak correlations were observed between Goutallier grade and both PROMIS PF and PROMIS PI (r=0.08, p=0.45 and r=0.06, p=0.58, respectively) (Fig. 4). On multivariate analysis, the RC muscle volumetric measurements that most strongly correlated with PROMIS PF and PI included the supraspinatus MSS (p<0.05), with a moderate positive correlation with preoperative PROMIS PF, and the supraspinatus RCS (p<0.05), with a moderate negative correlation in predicting preoperative PROMIS PF. The final multivariate linear regression for the volumetric measures to PROMIS PF resulted in a correlation of r=0.27 (p=0.18). The subscapularis MSS (p<0.05) and teres minor RCS (p<0.05) were moderate negative predictors of preoperative PROMIS PI. The final multivariate linear regression for the volumetric measures to PROMIS PI resulted in a correlation of r=0.37 (p=0.06).
Conclusions:
A strong correlation between the VS and Goutallier grades were observed in evaluation of the supraspinatus. However, although considered the gold standard in evaluation of RC pathology, Goutallier grade demonstrated almost no correlation with preoperative PROMIS PF and PI scores. The 3D MRI-based VS measurements demonstrated a stronger correlation with preoperative PROMIS PF and PI scores. The supraspinatus correlated more closely with PROMIS PF scores, while the subscapularis correlated more closely with preoperative PROMIS PI scores. These findings suggest that this novel 3D volumetric measurement modality, through a more holistic assessment of the RC unit, may provide a more accurate preoperative assessment of RC pathology and global shoulder function. Future research should be focused on assessing the prognostic utility of these novel assessments on postoperative PRO measures.
