Comparing Saphenous Nerve Conduction Study Techniques at the Knee and at the Ankle and Their Relationship to Body Mass Index

Chiodo A, Spiegelberg T, Tong HC. Comparing saphenous nerve conduction study techniques at the knee and at the ankle and their relationship to body mass index.ObjectiveTo evaluate the saphenous sensory response by 2 methods and the correlation of obtaining responses bilaterally with body mass index (BMI).DesignTwenty patients evaluated by 1 electromyographer and 10 patients evaluated by 2 blinded electromyographers.SettingUniversity electromyography laboratory.ParticipantsThirty healthy adult volunteers.InterventionsSaphenous sensory response with the recording electrode at the level of the medial malleolus, saphenous sensory response with the recording electrode at the level of the proximal tibia, and sural sensory response with the recording electrode posterior to the lateral malleolus.Main Outcome MeasuresSensory-evoked amplitude and distal latency.ResultsThe saphenous sensory response was obtained bilaterally at the knee in 77% of subjects, whereas it was obtained bilaterally at the ankle in only 50% of subjects (P<.05). BMI of greater than 25kg/m2 resulted in more difficulty in obtaining the saphenous sensory response at the ankle compared with the response at the knee (P<.05).ConclusionsThe saphenous sensory response at the knee is more consistently obtained than the saphenous sensory response at the ankle, and it is not affected by BMI.