Intranerve ratio and ultrasonography reliability in increasing the diagnostic sensitivity of minimal ulnar nerve entrapment at the elbow

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Abstract

Objective

The aim of this study was to detect the role of intranerve ratio (IN-ratio) and high-resolution ultrasonography (HRUS) in increasing the diagnostic sensitivity of minimal ulnar nerve entrapment (UNE) at the elbow.

Methods

This study included 39 patients having clinical and electrophysiological evidence of UNE, 27 patients having only clinical evidence of UNE, and 28 apparently healthy volunteers. IN-ratios were calculated and HRUS of the ulnar nerve were performed for all individuals.

Results

The IN-ratio was significantly decreased in group II when compared with other groups. The cutoff value was 0.98 or less for IN-ratio and 10 mm2 or more for maximum cross-sectional area (CSA-max). In group II, the CSA-max values were significantly increased in patients with positive IN-ratios (≤0.98) compared with those with negative IN-ratios (>0.98). There was a significant negative correlation between IN-ratios and CSA-max values. Positive decreased IN-ratios (≤0.98) were detected in 26 patients. IN-ratios of 0.98 or less were more frequently observed in patients of group II compared with other groups. Moreover, a higher incidence of positive IN-ratios (≤0.98) along with positive CSA-max (≥10 mm2) values was observed among patients of group II compared with other groups. Sensitivity and specificity of IN-ratios in diagnosing UNE electrophysiological (UNE EF)− patients were 66 and 82%, respectively. Using both IN-ratios (≤0.98) and CSA-max (≥10 mm2) increased the diagnostic sensitivity and specificity of UNE to 85 and 94%, respectively.

Conclusion

When IN-ratio and HRUS (CSA-max) findings are positive, the patient could be classified as having ‘minimal UNE’.

Recommendation

Using this new electrophysiological test along with CSA-max as a routine screening test for minimal cases of UNE is beneficial.

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