Increased reflectivity and loss in bulk of the pronator quadratus muscle does not always indicate anterior interosseous neuropathy on ultrasound

Purpose: To assess if isolated atrophy of the pronator quadratus muscle indicates anterior interosseous neuropathy on ultrasound. Materials and methods: IRB approval and written informed from every patient were obtained. A prospective study including 100 consecutive wrist and hand ultrasound studies in 77 patients (46 females and 31 males; 23 patients had bilateral studies) with a mean age of 45 years (range, 21–86 years) was performed between March 2010 and January 2012. The patients were chosen irrespective of age, sex, and body mass index. The studies were performed for several reasons, the most common being wrist pain (n = 56), followed by ganglion cyst (n = 11) and soft-tissue masses (n = 10). Clinical histories, previous imaging studies and US examinations were evaluated to rule out anterior interosseous nerve neuropathy. US examinations were performed with a commercially available equipment. Pronator quadratus was checked for atrophy using flexor pollicis longus, flexor digitorum superficialis and profundus for comparison. Descriptive statistic was used. Results: US signs of pronator quadratus atrophy were present in 7/100 (7%) of patients. None of the patients had a bilateral atrophy of the pronator quadratus. In the patients with atrophy of the pronator quadratus, adjacent flexor muscles were normal. There was no significant difference between males and females (3 females vs 4 males) (p = 0.506). Conclusion: Increased reflectivity and loss in bulk of the pronator quadratus muscle does not always indicate anterior interosseous neuropathy on ultrasound.