Is a single direct MR arthrography series in ABER position as accurate in detecting anteroinferior labroligamentous lesions as conventional MR arthography?

Abstract

Purpose: The purpose of this study is to retrospectively compare accuracy of single magnetic resonance (MR) arthrography series in Abduction External Rotation (ABER) with conventional MR arthrography for detection and characterisation of anteroinferior labroligamentous lesions, with arthroscopy as reference standard. Inter-observer variability of both protocols was determined.

Methods and materials: Institutional review board approval was obtained; informed consent was waived. MR arthrograms, including oblique axial fat suppressed T1-weighted images in ABER position and conventional imaging directions of 250 patients (170 men, 80 women; mean age, 36 years), were retrospectively and independently evaluated by three reviewers. Reviewers were blinded to clinical information and arthroscopic results. Labroligamentous lesions were registered in both ABER and MRa. The lesions were sub-classified (Bankart, Perthes, anterior labrum periosteal sleeve avulsion (ALPSA) or lesions not otherwise specified). Inter-observer agreement was assessed by Kappa statistics for all 250 patients. Ninety-two of 250 patients underwent arthroscopy. Sensitivity, specificity and accuracy of ABER versus conventional MR arthrography were calculated and compared using paired McNemar test.

Results: Kappa values of the ABER and conventional MR arthrography ranged from 0.44 to 0.56 and 0.44 to 0.62, respectively. According to arthroscopy, 45 of 92 patients had an intact anteroinferior labrum, and in 44 patients, a labroligamentous lesion (eight Bankart, seven Perthes, 29 ALPSA and three lesions not otherwise specified) was diagnosed. There were no statistically significant differences between ABER and conventional MR arthrography regarding sensitivity (85-89%, 89-96%), specificity (82-91%, 84-89%) and overall accuracy (50-62%, 53-63%).

Conclusion: The results of a single MR arthrography series in ABER position are comparable with those of conventional MR arthrography for detecting anteroinferior labroligamentous lesions.

Fig. 1

Bankart lesion. a T1-weighted fast field echo (FFE) MR arthrography image in an axial plane at the level of the inferior glenoid labrum with the arm in neutral position; avulsion of the anteroinferior labrum with stripping and complete disruption of the periosteum (arrow). b T1-weighted fat suppressed turbo spin echo (TSE) MR arthrography image in an oblique axial plane at the level of the inferior glenoid labrum with the arm positioned in abduction and exorotation (ABER) demonstrates the avulsed anteroinferior labrum with stripping and complete disruption of the periosteum (arrow). Note the bony glenoid defect

Fig. 2

Perthes lesion. a T1-weighted FFE MR arthrography image in an axial plane at the level of the inferior glenoid labrum with the arm in neutral position demonstrates no obvious anteroinferior labroligamentous lesion. b T1-weighted fat suppressed TSE MR arthrography image of the same patient in an oblique axial plane in ABER position clearly demonstrates the avulsed anteroinferior labrum with medial stripping of an intact periosteum (arrow)

Fig. 3

Anterior Labrum Periosteal Sleeve Avulsion. a T1-weighted FFE MR arthrography image in an axial plane at the level of the inferior glenoid labrum with the arm in neutral position demonstrates a medially displaced and inferiorly rotated labrum (arrow). b T1-weighted fat suppressed TSE MR arthrography image in an oblique axial plane with the arm in ABER position shows a medially displaced and inferiorly rotated anteroinferior labrum (arrow)

Fig. 4

Patient selection and inclusion

Fig. 5

Overall accuracy