Evaluation of Muscular Atrophy and Fatty Infiltration Using Time-zero Magnetic Resonance Imaging as Baseline Data, After Rotator Cuff Repair

Abstract

Background: This study evaluated postoperative changes in the supraspinatus from time-zero to 6 months, using magnetic resonance imaging (MRI). We hypothesized that restoration of the musculotendinous unit of the rotator cuff by tendon repair immediately improves the rotator cuff muscle status, and maintains it months after surgery.

Methods: Totally, 76 patients (29 men, 47 women) with rotator cuff tears involving the supraspinatus tendon who underwent arthroscopic rotator cuff repairs were examined. MRI evaluation showed complete repair with intact integrity of the torn tendon at both time-zero and at 6 months follow-up. All patients underwent standardized MRI at our institution preoperatively, at 1 or 2 days postoperative, and at 6 months after surgery. Supraspinatus muscular (SSP) atrophy (Thomazeau grade) and fatty infiltrations (Goutallier stage) were evaluated by MRI. The cross-sectional area of SSP in the fossa was also measured.

Results: As determined by MRI, the cross-sectional area of SSP significantly decreased 11.41% from time-zero (immediate repair) to 6 months post-surgery, whereas the Goutallier stage and Thomazeau grade showed no significant changes (p < 0.01). Furthermore, compared to the preoperative MRI, the postoperative MRI at 6 months showed a no statistically significant increase of 8.03% in the cross-sectional area. In addition, morphological improvements were observed in patients with high grade Goutallier and Thomazeau at time-zero, whereas morphology of patients with low grade factors were almost similar to before surgery.

Conclusions: Our results indicate that cross-sectional area of the initial repair appears to decrease after a few months postoperatively, possibly due to medial retraction or strained muscle.

Keywords: Fatty infiltration; Muscular atrophy; Rotator cuff repair; Time-zero magnetic resonance imaging.

Fig. 1.

The area was measured using the Centricity-Radiology RA1000 workstation (GE Healthcare Integrated IT Solutions, Barrington, IL, USA) by use of a mouse-point cursor and automated computer calculation for distance and angle. All measurements were performed twice by 2 independent observers. SD: standard deviation, Max: maximum, Min: minimum.

Fig. 2.

The pain visual analogue scale (PVAS), function visual analogue scale (FVAS), and American Shoulder and Elbow Surgeons (ASES) were significantly improved from preoperative to postoperative 6 months (p<0.001), from 6 months to 1 year (p<0.001), and from preoperative to the final follow-up evaluations (p<0.001). Constant scores were significantly improved from preoperative to postoperative 6 months (p<0.001), and from 6 months to 1 year (p<0.001).

Fig. 3.

(A) Goutallier stages were significantly improved from preoperative magnetic resonance imaging (MRI) to time-zero MRI (p=0.0034). However, no significant changes were observed between preoperative to 6-month follow-up MRI (p=0.06), and time-zero to 6-month follow-up MRI (p=0.93). (B) Goutallier stage 3 and 4 were significantly decreased from preoperative MRI to time-zero MRI (p<0.01). (C) Thomazeau grade were significantly improved from preoperative MRI to time-zero MRI (p=0.0015), although there were no significant differences between preoperative and follow-up MRI, and time-zero and follow-up MRI (p=0.60, p=0.67). (D) Thomazeau grades 3 were significantly decreased from preoperative MRI to time-zero MRI (p<0.01).

Fig. 4.

(A) Cross-sectional area of the supraspinatus significantly improved from 373.76 mm² preoperatively to 444.12 mm² time-zero magnetic resonance imaging (MRI) (p<0.0001). Cross sectional area of supraspinatus changes were: (B) increased 21.72% from preoperative MRI to time-zero MRI (p<0.0001), (C) decreased 11.41% from time-zero MRI to follow-up MRI (p<0.0001), and (D) increased 8.03% from preoperative to follow-up MRI, although difference was statistically not significant (p=0.14).

Fig. 5.

The schematic drawing presents the cross-sectional area of the supraspinatus muscle on the same scapular plane. The cross-sectional area of the supraspinatus was increased immediately after surgery. However, cross-sectional area was decreased without re-tear 1 month after repair. One of the factors that reduced cross-sectional area is thought to be the medial retraction of repaired tendon. MRI: magnetic resonance imaging.