Luis Saura Beltran MD, Presenter: Nothing to Disclose

Amado Ross Sussmann MD, Abstract Co-Author: Nothing to Disclose

Jenny T. Bencardino MD, Abstract Co-Author: Nothing to Disclose

To determine if a low lying medial triceps muscle and tendon insertion are MR predictors of ulnar neuritis

A retrospective review of 542 consecutive elbow MR exams from 1/2009 to 9/2011 yielded 25 patients (13M, 12W, age: 24-82 mean 48) with clinical diagnosis of ulnar neuritis comprising the study group, and 50 patients (32M, 18W, age: 20-79 mean 45) without clinical or MR evidence of medial elbow pathology comprising the control group. The following variables were measured by one reader blinded to clinical history and MR findings: Medial triceps muscle belly (MTMB) and tendon insertion (MTTI) distance relative to the superior olecranon (see figure), average (ACSA) and maximum ulnar nerve cross section area (MCSA), and nerve-to-muscle signal ratio (NMSR). Subjects were divided into three groups: 1) low lying muscle (<0) and low lying tendon (<0), 2) low lying muscle (<0) and non low lying tendon (≥0), and 3) non low lying muscle and tendon (both ≥0). The prevalence of clinical ulnar neuritis was calculated for each group. The association of this classification of subjects with ulnar neuritis was calculated using Chi-square analysis. Exact Mann-Whitney tests were used to compare subjects with and without ulnar neuritis in terms of each measure.

Mean values in the study group were: ACSA=0.110 (SD=0.034), MCSA=0.156 (SD=0.062), MTMB=0.448 (SD=2.760), MTTI=-4.208 (SD=1.652), and NMSR=2.586 (SD=1.063). The mean values in the control group were: ACSA=0.095 (SD=0.027), MCSA=0.133 (SD=0.052), MTMB =0.856 (SD=2.777), MTTI=-3.808 (SD=2.023), and NMSR=1.803 (SD=0.757). The prevalence of ulnar neuritis was 37.5% (6/16) in group 1, 34.5% (19/55) in group 2, and 0% in group 3. There was no significant association of this classification of subjects with ulnar neuritis (p=0.3391). Only NMSR significantly predicted ulnar neuritis (p=0.0022), with diagnostic accuracy maximized for the threshold of 2.6047. Using this threshold achieved 52% (13/25) sensitivity and 90% (45/50) specificity.

Since no measure other than nerve-to-muscle signal ratio was a significant MR predictor of ulnar neuritis, our data do not support the contention that there is a medial muscle belly or tendon insertion distance below which ulnar neuritis is more likely.

The presence of a low lying medial triceps muscle or tendon insertion on MRI does not significantly predict ulnar neuritis.

Beltran, L, Sussmann, A, Bencardino, J, Low Lying Medial Head of Triceps on MR Imaging: Is It a Reliable Predictor of Ulnar Neuritis?.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12023646.html