In vivo measurement of facet joint nitric oxide in patients with chronic low back pain

Study Design. Prospective case-control study testing a new diagnostic method. Objective. The aim of the present study was to investigate the concentration of nitric oxide ( NO) in the perifacetal region in patients with chronic low back pain and healthy controls. Summary of Background Data. Facet joint arthrosis may be a pain source in chronic back pain. Increased concentrations of NO, an oxygen-free radical, have been demonstrated in temporomandibular and knee joints with osteoarthritis. Patients and Methods. Patients with at least 6 months' duration of chronic low back pain and signs of facet joint osteoarthrosis ( n = 24) and healthy volunteers ( n = 7) were included. A detailed questionnaire, including visual analogue scale, was completed before and 6 weeks after the measurements. NO was measured with a custom-designed electrochemical real-time NO sensor inserted under fluoroscopic guidance. All patients received corticosteroids and local anesthetics after NO measurements. Results. NO measurements were obtained from all participants. No adverse effects were noted. The patients with chronic low back pain demonstrated higher concentrations of NO in the perifacetal region compared with healthy controls ( 1.66 +/- 0.28 vs. 0.46 +/- 0.14 nmol/ L, P = 0.007). No association between NO concentration and pain duration or pain level was detected. Patients with a positive response to local anesthetics and corticosteroid injection ( defined as a >= 20 mm reduction of visual analogue scale at the 6-week follow-up visit) had higher NO concentrations than patients without positive response. Conclusions. The study demonstrates that it is feasible and safe to measure NO with a real time-sensor in or around the facet joints. The findings of higher concentrations of NO in the perifacetal region in chronic low back patients compared with healthy controls indicate that the degenerative process of the joints in these patients may cause increased NO production. The observation of higher NO concentrations in the perifacetal region in patients responding to corticosteroid/ local anesthetic infiltration indirectly suggest a more pronounced inflammatory process in these patients.