Direct Visualization of A2, A3, and A4 Finger Flexor Pulley Injuries at 3-T and 7-T MRI: An Ex Vivo Study

Introduction Our aim was to evaluate the feasibility and to compare image quality and diagnostic performance of 3-T and 7-T magnetic resonance imaging (MRI) for direct depiction of finger pulley ruptures using anatomical preparation as a reference.

Material and Methods A total of 30 fingers from 10 human cadavers were examined at 3 T and 7 T before and after being subjected to iatrogenic pulley ruptures. MRI protocols were comparable in duration. Two experienced radiologists evaluated the MRIs and defined the location and morphology of the finger pulley lesions. Image quality was graded according to a 4-point Likert scale. The diagnostic performance was assessed with anatomical preparation as the gold standard. Interobserver agreement was calculated using Cohen’s κ coefficients.

Results Sensitivity and specificity were comparable in 7 T versus 3 T for the detection of A2, A3, and A4 pulley lesions: 100% versus 95% and 98% versus 100%, respectively. In the assessment of A3 pulley lesions, sensitivity of 7-T was superior to 3-T MRI (100% versus 83%), whereas specificity was lower (95% versus 100%). Image quality assessed before and after iatrogenic rupture was comparable, 2.74 for 7 T and 2.61 for 3 T, reflecting adequate image quality on average, whereas visualization of the A3 finger flexor pulley before rupture creation was significantly better for 7 T (p < 0.001). Interobserver variability was substantial at 7 T (κ = 0.90) and 3 T (κ = 0.80).

Conclusion MRI at 3 T and 7 T allows direct visualization of traumatic A2, A3, and A4 pulley lesions with slightly higher agreement rates for 7 T. Hence high field MRI may be a helpful approach for presurgical evaluation compared with indirect techniques such as ultrasound that depends on bowstringing.