We enrolled 75 patients between October 2003 and July 2006 who met the following inclusion criteria: the patient had to (1) have a full-thickness rotator cuff tear verified by preoperative MR arthrography (MRA), (2) have surgery, (3) be available for postoperative CT arthrography (CTA) to evaluate cuff integrity and FD of cuff muscles, and (4) be available a minimum of 1 year after the operation. We excluded patients with partial-thickness rotator cuff tears, isolated glenohumeral abnormalities (superior labral anterior-posterior lesion, instability, etc), revision of surgical cuff repair, any previous shoulder surgery, isolated subscapularis tear, and irreparable cuff tear. There were 38 men and 37 women with a mean age of 59.35 years (range, 39–77 years; standard deviation [SD], 8.77). The dominant shoulder was involved in 61 patients (81.3%). We obtained prior Institutional Review Board approval for the study protocol.
We performed arthroscopy-assisted mini-open repair in 30 patients (40%), and all-arthroscopic repair in 45 (60%). All surgical procedures were performed by the senior author (JHO) and there was no partial repair. The anteroposterior (AP) dimension and retraction of the cuff tear was measured during arthroscopy with a probe. The mean AP dimension of the cuff tear at footprint was 2.46 cm (range, 0.60–5.00 cm; SD, 1.36) and the mean retraction length was 2.34 cm (range, 0.50–6.60 cm; SD, 1.28). When the rotator cuff tears were categorized according to the tear size (AP dimension), there were 18 small (< 1 cm) (24%), 26 medium (1–3 cm) (34.7%), and 31 large to massive tears (> 3 cm) (41.3%).
For preoperative MRA, the contrast media was injected into the joint with fluoroscopic guidance through an anterior approach. A 22-gauge spinal needle was placed in the glenohumeral joint, and 1 to 5 mL iodinated contrast material (Telebrix 30®; Guerbet, Villepinte, France) was used to verify intraarticular injection. Diluted gadopentetate dimeglumine (12–20 mL) (Omniscan™; GE Healthcare Amersham, Oslo, Norway) at a concentration of 2.5 mmol/L was injected. MRI was performed on a 1.5-T system (Philips Gyroscan Intera; Philips Medical Systems, Utrecht, The Netherlands). MRI was started immediately after contrast was injected (within 5 minutes of intraarticular injection). The shoulders were placed in a neutral position in a dedicated, phased-array, Flex-M coil (Philips Medical Systems). We obtained fat-suppressed T1-weighted spin-echo images in the transverse plane (TR/TE: 400–700 ms/10–20 ms; 3-mm section thickness; 0.3-mm interval; 160- × 160-mm field of view; 256- × 512-pixel matrix) in the oblique coronal plane parallel to the supraspinatus muscle and in the oblique sagittal plane parallel to the joint surface of the glenoid. T1-weighted spin-echo images without fat suppression were obtained in the oblique coronal plane. We obtained T2-weighted spin-echo images in the coronal plane and in the oblique sagittal plane (TR/TE: 2500–3500 ms/89–100 ms). Three-dimensional gradient echo images (3DWatSc; TR/TE: 20 ms/9–10 ms; 20° flip angle) were obtained in the transverse plane.
For postoperative CTA, we injected 12 to 20 mL diluted (65%) iodinated contrast material (Telebrix 30®). CT was performed using a 16-multidetector CT system (Mx 8000 IDT; Philips Medical Systems), with the following scan parameters: tube voltage, 120 kV; tube current, 245 mAs; 1-mm slice thickness; 0.5-mm increment; beam collimation, 0.75 mm; effective pitch, 0.9; 150-mm field of view; 1024- × 512-pixel matrix. For data analysis, we generated oblique coronal, oblique sagittal, and axial reconstructions at a three-dimensional workstation with a 2-mm section thickness and no reconstruction interval for the axial images and a 2-mm reconstruction interval for oblique coronal and sagittal images. Oblique coronal images were reconstructed parallel to the supraspinatus muscle and oblique sagittal images parallel to the joint surface of the glenoid with identical section thickness and reconstruction interval.
Two musculoskeletal radiologists (JAC, YK) (experience level: 7 years and 2 years after fellowship training in musculoskeletal imaging) and three shoulder fellowship-trained orthopaedic surgeons (CHO, KHJ, JHO) (experience level: 2, 3, and 5 years) determined the FD of each rotator cuff muscle using the grading system of Goutallier et al. using preoperative MRA and postoperative CTA (Table ). Also, data of the FD grades by Goutallier et al. were converted into the system of Fuchs et al. [6
], which was developed to minimize choice variability, in which the five grades in the system of Goutallier et al. were reduced to three stages by grouping, ie, Goutallier’s Grades 0 and 1 are regarded as normal muscle, Grade 2 as moderately pathologic muscle, and Grades 3 and 4 as advanced degeneration (Table ).
Criteria for grading fatty degeneration of rotator cuff muscles
To assess interobserver reliability, the two radiologists and three orthopaedic surgeons reviewed preoperative MRA and postoperative CTA scans and graded the FD of the cuff muscles. All five raters were aware all patients enrolled in the study had rotator cuff tears and had undergone repair. Several meetings were held before the interpretation regarding which image cuts of the preoperative MRA and postoperative CTA should be selected for evaluation of the FD: the FDs of the supraspinatus, infraspinatus, and subscapularis muscles were measured on the oblique sagittal T1-weighted image at the level showing the coracoid base and where the spine and body of the scapula form a Y shape [6
]. For evaluation of CTA, the same level of the sagittal reconstruction image was used (Fig. ). All observers were free to observe all scans and choose one representative scan for the evaluation. The first rating for the five observers at the same time was used to evaluate interobserver reliability.
For the FD evaluation, the oblique sagittal T1-weighted image was used at the level that shows the coracoid base and where the spine and body of the scapula form a Y shape in (A) MRA and (B) CTA.
To assess intraobserver reliability, all raters performed the second radiographic evaluation with the same image for the FD of the cuff muscles. Before the second rating, all raters were unaware of the first rating.
The intraobserver and interobserver reliabilities of the five raters were evaluated with the ICC, a two-way random model with absolute agreement, for each FD of the cuff on preoperative and postoperative images. The value can range from 0 to 1; close to 1 indicates high reliability of measurement. All analyses were performed using the SPSS® software package (Version 12.0; SPSS Inc, Chicago, IL).