Effect of Preoperative Fatty Degeneration of the Deltoid and the Teres Minor Muscles on the Clinical Outcome after Reverse Total Shoulder Arthroplasty

Moon, Sung Hoon; Nam, Woo Dong; Rheu, Chang Hyun; Lee, Jae Woo

Abstract

BACKGROUND
To evaluate the effect of preoperative fatty degeneration of deltoid and teres minor muscles on the clinical outcome in patient with reverse total shoulder arthroplasty (RTSA).
METHODS
Nineteen patients with RTSA were enrolled. The mean follow-up period was 16.1 months. The fatty degeneration of three distinct parts in each deltoid and the teres minor muscle was measured using a preoperative magnetic resonance imaging. Postoperatively, the muscle strengths for forward elevation (FE), abduction (Abd), and external rotation (ER) were measured using a myometer at the last follow-up. The parameters for clinical outcome were Constant Score (CS) and Korean Shoulder Score (KSS).
RESULTS
The number of cases was 10 in group 1 and 9 in group 2. The strength of FE and Abd were significantly higher in group 1 (p<0.001 and p<0.001, respectively), and the strength of ER was not different significantly between two groups (p=0.065). For the clinical outcome, both CS and KSS were higher in group 1 (p=0.002 and p=0.002, respectively). The number of patients in group A was 11, and group B was 8. Although there was not a significant difference in terms of FE and Abd between group A and B (p=0.091, p=0.238), ER was significantly higher in group A (p=0.012). We did not find a significant difference in the clinical scores (CS, p=0.177 and KSS, p=0.238).
CONCLUSIONS
These findings suggest the importance of a preoperative evaluation of the fatty degeneration of deltoid and teres minor muscles for predicting postoperative strength and clinical outcome.