Utility of minimum F-wave latencies compared with F-estimates and absolute reference values in S1 radiculopathies: Are they still needed?

Introduction: The utility of F-waves in assessing radiculopathies is debated. The aim of this study is to determine the frequency of abnormal minimum tibial F-wave latencies compared to an F-estimate and an absolute reference value in patients with electromyography (EMG) confirmed S1 radiculopathies. Methods: A retrospective review of F-waves in patients with an EMG-confirmed isolated S1 radiculopathy was performed. The minimum and mean latencies of 8 tibial F-waves were compared with the calculated F-estimate and to an absolute reference value, and the frequencies of abnormal responses were determined. Results: Of the 50 patients with an S1 radiculopathy, 4% had prolongation of the minimum reproducible F-wave latency, and 8% had prolongation of the mean latency relative to the calculated F-estimate. Conclusions: The minimum and mean F-wave latencies are infrequently abnormal when compared with an estimated F-wave latency in S1 radiculopathies and are insensitive in the assessment of S1 nerve root injury.