Diagnostic Accuracy of Ultrasound for Digital Nerve Injuries
Ameya V Save, MD1; Ogonna K. Nwawka, MD1; Christian Victoria, MPH1; Steve K. Lee, MD2; Lydia Ko, MPH1
1Hospital for Special Surgery, New York, NY; 2Hand and Upper Extremity Surgery, Hospital for Special Surgery, New York, NY
The purpose of this study was to determine the accuracy of diagnostic ultrasound for the evaluation of digital nerve injuries. We hypothesized that there would be a high match rate between the pre-operative ultrasound assessment and intra-operative findings.
Materials and Methods:
A retrospective review was conducted of patients with clinically suspected digital nerve injuries who had a pre-operative diagnostic ultrasound of the finger prior to surgical exploration. Patients evaluated between March 2016 and March 2020 were included. Pre-operative clinical data, ultrasound reports, and operative findings were reviewed. In order to be considered accurate, the pre-operative ultrasound had to correctly identify the presence of a laceration, the degree of a laceration, and the presence or absence of neuroma formation based on subsequent intra-operative findings.
Twenty-nine patients and 33 clinically suspected nerve injuries were identified. Four patients had more than 1 nerve injury suspected. The average age was 38 years (range 11- 63 years). There were 11 male patients, and 18 female patients. There was a match between pre-operative ultrasound diagnosis and intra-operative findings in 26/ 33 cases (79%). There was a mismatch in 4/33 cases (12%). The pre-operative ultrasound was reported as inconclusive in 3/33 cases (9%). The accuracy rate improved with the amount of time that had elapsed between injury and when the ultrasound was performed. The four cases in which a mismatch was identified were all performed within 3 days of injury. The accuracy rate of ultrasound performed 0-3 days after injury was 67%, 4-7 days was 78%, and over 7 days was 92%. In cases where over 30 days had elapsed since injury, ultrasound correctly identified neuroma formation in 100% of cases. Poor visualization due to surrounding soft tissue edema was the most commonly identified reason for an erroneous or inconclusive ultrasound.
Ultrasound evaluation of digital nerve injuries matched intra-operative findings in 79% of cases. The accuracy of ultrasound improved with the amount of time since the injury had occurred, with all cases of mismatch occurring within 3 days of injury. Chronic nerve injuries were readily diagnosed by the presence of neuroma formation.
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