Purpose of review: Approximately 20% of patients undergoing surgery develop persistent lower extremity pain following total knee arthroplasty. Animal studies have confirmed that prolonged tourniquet time increases the risk of endoneural ischemia and can mediate or modulate the development of chronic pain. The use of Near InfraRed Spectroscopy (NIRS) adjacent to nerve tissue, previously described as ONG has been shown to detect early neural compromise and has demonstrated clinical utility in carpal tunnel diagnosis.
Recent findings: In this pilot study, we recruited 10 healthy adult volunteers to undergo oxyneurography (ONG) and sensory nerve conduction testing (sNCT). We performed testing on the upper and lower extremities in each individual. The tourniquet was applied followed by measurements of sNCT and ONG as described. We observed a significant drop in the mean ONG index at 3 and 5 min following tourniquet inflation in upper and lower extremities. Similar to raw ONG values, there was significant variability in sNCT measurements, which in general increased from baseline with tourniquet inflation. In the upper extremity, there was a significant increase in sNCT with tourniquet inflation, while in the lower extremity, there was a trend towards significance. The use of ONG can be supported as a diagnostic tool to detect nerve ischemia and to potentially reduce the incidence of tourniquet-mediated or -modulated neural ischemia and reduce the development of chronic post-tourniquet pain.
Keywords: Near InfraRed Spectroscopy; Neural ischemia; Oxyneurography index; Pain; Sensory nerve conduction.