MRI OF THE STENER LESION

Objective. To assess the utility of MR in detecting surgically induced Stener lesions (displaced thumb ulnar collateral ligaments) in cadave ric models. Design. Six cadaver thumbs had ulnar collateral ligament ( UCL) tears created surgically. MR examinations (2D STIR and 3D GRASS) were performed identically on all specimens both before displacement ( non-Stener) and after displacement (Stener lesion) of the UCL. The MR images were then randomly numbered. Each image was evaluated separatel y in blinded fashion by four musculoskeletal radiologists for the pres ence or absence of a Stener lesion, Each radiologist reinterpreted the images after an interval of several days. The interpretation was base d on previously published criteria for Stener lesion diagnosis by MR. Results. The sensitivity of GRASS ranged from 0.17 to 0.67 with the mo st experienced reader scoring the lowest. The specificity of GRASS ran ged from 0.33 to 1.0 (most experienced reader 0.67, 0.83). STIR had a sensitivity of 0.00-0.17 and a specificity of 0.53-0.83. The kappa val ues for inter- and intraobserver agreement were measured. The intraobs erver kappa for GRASS was 0.27-0.75 (most experienced reader 0.75). Co nclusions. 2D imaging is probably inadequate for the evaluation of Ste ner lesions. The most likely reason is that the STIR slice thickness o f 3 mm limits resolution of small UCLs. The poor sensitivity and speci ficity of GRASS as well as poor interobserver agreement suggest that M R may not be sufficiently accurate for Stener lesion evaluation.