Sonographic appearance of the posterior interosseous nerve at the wrist.

OBJECTIVES The purpose of this study was to determine whether sonography can identify the distal posterior interosseous nerve at the wrist. METHODS On the basis of previous anatomic descriptions, high-resolution musculoskeletal sonography was used in an attempt to identify the distal posterior interosseous nerve in the wrists of 20 unembalmed cadaveric specimens (11 male and 9 female; ages 54-98 years). High-frequency scanning (17-5 MHz) of the fourth dorsal extensor compartment revealed a small (1-3 mm) hypoechoic structure located on the compartment floor, presumed to represent the posterior interosseous nerve. Electronic calipers measured the distance between Lister's tubercle and this structure, as well as the structure's radial-ulnar width and volar-dorsal height. The presumed posterior interosseous nerves of 10 specimens were then injected with diluted colored latex using sonographic guidance. Subsequent dissection definitively identified the sonographically visualized and injected structure. RESULTS Dissection revealed latex within the posterior interosseous nerve in all 10 injected specimens, thus confirming that the sonographically visualized structure represented the distal posterior interosseous nerve. The nerve was identified sonographically in all 20 examined specimens, was located an average of 4.88 mm (range, 2.10-10.0 mm) ulnar to Lister's tubercle, and had an average width and height of 2.35 mm (range, 1.20-3.50 mm) and 1.01 mm (range, 0.80-1.40 mm), respectively. CONCLUSIONS High-resolution sonography can reliably identify the distal posterior interosseous nerve within the fourth dorsal extensor compartment. Clinicians should consider formal evaluation of the posterior interosseous nerve in patients presenting with dorsal wrist pain syndromes. Future investigations should explore the potential role of sonographically guided percutaneous procedures directed at the posterior interosseous nerve.