Ultrasound features of traumatic digital nerve injuries of the hand with surgical confirmation

Characterize the appearance of digital nerve injuries in different ultrasound planes and correlate the presence and size of neuromas with time from injury.

Surgically confirmed nerve injuries were retrospectively evaluated. Appearances of the nerve injury in the available imaging planes were reviewed by two readers. Associations between presence and size of neuroma with time from injury were analyzed.

Injuries of 29 digital nerves (3 incomplete lacerations, 17 complete lacerations, 6 with 7 stump neuromas, 3 neuromas-in-continuity) noted on ultrasound were surgically confirmed. Among the 20 lacerations, long-axis images were obtained in 15, of which 10 depicted the injury and 4 did not. Among the 10 depicting the injury in long axis, 2 showed a discrete gap, and 7 showed the nerve obscured by laceration tissue without a gap. In short axis, the nerve injury was visible in all 20, and nerve laceration was seen as a discrete gap in 2, and obscuration by laceration tissue in 14. Neuromas were hypoechoic and well-defined. There was a positive association between time and presence of neuroma (OR = 1.3, p = 0.002). Correlations between time and cross-sectional area (r_s = 0.45) and volume (r_s = 0.57) of neuromas were moderately positive.

Ultrasound long axis may be less useful, and those short axis may be more reliable for assessing digital nerve injuries than previously reported. Neuromas are hypoechoic and well-defined, and their size can vary based on time from injury.