Reproducibility and reliability of subscapularis tendon assessment using CT-arthrography.

BACKGROUND

Computed tomography (CT) coupled with arthrography remains the reference standard for the preoperative evaluation of rotator cuff tears. The objectives of this study were to evaluate intra-observer and inter-observer reproducibilities of CT-arthrographic assessment of the subscapularis tendon and to assess the validity and reliability of this investigation.

HYPOTHESIS

CT-arthrography is reliable and reproducible for the preoperative characterisation of subscapularis tendon lesions.

MATERIAL AND METHODS

We retrospectively reviewed 67 shoulders with rotator cuff tears in one or more tendons managed by arthroscopy, both to confirm the diagnosis and to allow therapeutic interventions. Each of the 67 preoperative CT-arthrograms was evaluated by three readers, of whom the first two evaluated the images twice at an interval of 30 days. The following were recorded at each reading: partial- or full-thickness tear in one or more rotator cuff tendons, intra-tendinous delamination, tendon stump retraction, and fatty degeneration of the muscles. The position of the long head of biceps tendon was assessed. A statistical analysis was performed using Fleiss' method to compute intra-observer and inter-observer variabilities in CT-arthrography assessment of the subscapularis tendon status. Validity of this assessment was measured by computing the concordance coefficients between CT-arthrography and arthroscopy.

RESULTS

Specificity of CT-arthrography was satisfactory for assessing the subscapularis tendon. Sensitivity was low. Significant inter-observer and intra-observer variabilities were documented. The concordance coefficients between CT-arthrography and arthroscopy indicated that major differences were common with all three readers. When assessing the subscapularis tendon by CT-arthrography, all readers experienced difficulties in distinguishing intact tendons, delaminated tendons, and tendons with tears confined to the upper third.

DISCUSSION

Although CT-arthrography remains the reference standard for the preoperative investigation of rotator cuff tears, significant variability occurs in assessing the continuity of the subscapularis tendon. Reliability of this assessment is not optimal, as shown by our evaluation of concordance with arthroscopy. Although our data should be interpreted in the light of the investigation and measurement biases present in our study, they suggest that CT-arthrography may fail to provide a valid and reproducible assessment of the subscapularis tendon. The development of magnetic resonance (MR) imaging and MR-arthrography will probably improve the preoperative evaluation of subscapularis tears in the near future.

LEVEL OF EVIDENCE

Level III; diagnostic value study.