Friday, September 28, 2018 10:30 AM–12:00 PM abstracts: innovation, surface technology and biomechanics: 183. Correlation of intervertebral disc TNFα concentration with clinical characteristics of patients with acute and chronic inflammatory radiculopathy secondary to lumbar disc herniation

BACKGROUND CONTEXT The exact etiology of spinal nerve root injury associated with sciatica secondary to herniated nucleus pulposus (S/HNP) remains uncertain. The mechanism of injury is thought to be mediated in part, through an acute inflammatory response that involves the up-regulation of specific inflammatory cytokines. TNFα has been implicated as a key component of an inflammatory cascade that results in a painful “chemical radiculitis”. However, a randomized clinical trial has demonstrated that the IV administration of a TNFα inhibitor to patients with acute S/HNP has no added value when compared to saline infusion. A prospective cohort study has reported inconsistent therapeutic value to TNFα inhibition in patients with chronic S/HNP. PURPOSE To correlate HNP TNFα concentration with clinical characteristics of patients with acute and chronic S/HNP treated surgically. STUDY DESIGN/SETTING Prospective clinical assessment of patients with acute and chronic S/HNP. Enzyme linked immunosorbent assay (ELISA) of serum and disc tissue inflammatory cytokine content. PATIENT SAMPLE Inclusion: S/HNP of less than 1 year duration undergoing surgery; McCulloch score of 5/5 spinal nerve root motor score of >3/5; Exclusion: red flag condition, prior lumbar surgery, other active inflammatory disease. OUTCOME MEASURES Duration of sciatica symptoms at time of surgery. VAS and mRDQ scores within two weeks of time of surgery. TNFα concentration in extruded disc material measured by (ELISA) immunoassay. METHODS After obtaining informed consent, eligible patients with S/HNP undergoing laminectomy or discectomy surgery were enrolled. Clinical history including of date of onset of sciatica and spinal-nerve root neurological examination findings were recorded. Herniated disc tissue removed at the time of surgery was immediately placed in buffered solution containing protease inhibitors and was frozen or stored at −80°C. Disc tissue homogenates were analyzed in duplicate using ELISA (BioRad). Research ethics approval was obtained. RESULTS A total of 24 patients with sciatica secondary to HNP undergoing lumbar discectomy surgery were included in this study. The duration of sciatica symptoms ranged from 3 to 12 months. Herniated disc tissue TNFα concentrations ranged from 0.9 to 24pg/ml. TNFα concentration was highest in patients with acute sciatica CONCLUSIONS In this study population, the concentration of TNFα in herniated disc tissue diminished dramatically after 12 weeks duration of sciatica symptoms, but was not associated with VAS or mRDQ scores. TNFα concentrations were consistently low in patients with chronic sciatica. High disc tissue TNFα concentration was found in the majority of patients with clinical signs of severe nerve root irritation. These findings provide biochemical evidence that the etiology of both acute and chronic lumbosacral radiculopathy secondary to herniated nucleus pulposus is multifactorial and does not directly correlate to extruded disc material TNFα concentration. Treatment strategies based upon TNFα inhibition are likely to have limited therapeutic benefit beyond 12 weeks post onset of sciatica.