MRI of the ulnar nerve pre- and post-transposition: imaging features and rater agreement
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SCIENTIFIC ARTICLE
MRI of the ulnar nerve pre- and post-transposition: imaging features and rater agreement Thiru Sivakumaran 1,2
&
Darryl B. Sneag 2 & Bin Lin 2 & Yoshimi Endo 2
Received: 11 May 2020 / Revised: 31 July 2020 / Accepted: 2 September 2020 # ISS 2020
Abstract Objective Determine the rater agreement of MRI features of the ulnar nerve pre- and post-transposition and association with recurrent symptoms. Materials and methods This IRB-approved retrospective cohort analysis examined 23 subjects who underwent elbow MRI preand post-ulnar nerve transposition from 1999 to 2018, 10 of whom developed recurrent symptoms. Pre- and post-transposition MRIs were evaluated by two blinded radiologists for ulnar nerve cross-sectional area, signal intensity, fascicular architecture, caliber change, and perineural scar. Inter-rater agreement was estimated using intraclass correlation coefficients (ICCs) for continuous variables and Gwet’s agreement coefficient (AC) for categorical variables. Binary logistic regression modeling probed associations between imaging markers and symptom recurrence. Results The ulnar nerve, post-operatively, demonstrated statistically significant increases in size (p < 0.001), signal intensity (p = 0.021), and abrupt caliber change (p = 0.024). None of the imaging features, except for higher signal intensity of the nerve pretransposition as demonstrated by one rater, were predictive of symptom recurrence. Inter-rater agreement for cross-sectional area measurements of the ulnar nerve at the cubital tunnel was excellent (ICCs of 0.91 and 0.83). Substantial-to-excellent inter-rater agreement was observed pre-operatively for nerve signal intensity, caliber change, and fascicular architecture. Post-operatively, agreement on nerve signal intensity and perineural scar was excellent (ACs of 0.90 and 0.88), but only slight for caliber change (0.15). Conclusion Inter-rater agreement for qualitative and quantitative assessment of the ulnar nerve was generally robust. Posttransposition, the ulnar nerve was generally larger and more T2-hyperintense, but MRI features were not predictive of recurrent ulnar neuropathy, except for perhaps the signal intensity of the nerve pre-transposition. Keywords Ulnar nerve . Transposition . MRI
Introduction Operative management of cubital tunnel syndrome with anterior subcutaneous or submuscular transposition of the ulnar nerve is unsuccessful in 10–20% of cases [1–4]. Treatment failure is multifactorial and attributed to several etiologies including inadequate decompression, injury to the medial antebrachial cutaneous nerve or ulnar nerve, and perineural
* Thiru Sivakumaran [email protected] 1
Department of Medical Imaging, Sunnybrook Hospital, University of Toronto, Toronto, ON, Canada
2
Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY, USA
fibrosis [5–11]. Electrodiagnostic testing of the ulnar nerve is robust but imperfect, with sensitivity of 71–78% for ulnar neuropathy in the pre-operative setting [12–14]. Imagi
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