Association of time to surgery with leg pain after lumbar discectomy: is delayed surgery detrimental?

Abstract

While it has been established that lumbar discectomy should only be performed after a certain waiting period unless neurological deficits are present, little is known about the association of late surgery with outcome. Using data from a prospective registry, the authors aimed to quantify the association of time to surgery (TTS) with leg pain outcome after lumbar discectomy and to identify a maximum TTS cutoff anchored to the minimum clinically important difference (MCID). TTS was defined as the time from the onset of leg pain caused by radiculopathy to the time of surgery in weeks. MCID was defined as a minimum 30% reduction in the numeric rating scale score for leg pain from baseline to 12 months. A Cox proportional hazards model was utilized to quantify the association of TTS with MCID. Maximum TTS cutoffs were derived both quantitatively, anchored to the area under the curve (AUC), and qualitatively, based on cutoff-specific MCID rates. From a prospective registry, 372 patients who had undergone first-time tubular microdiscectomy were identified; 308 of these patients (83%) obtained an MCID. Attaining an MCID was associated with a shorter TTS (HR 0.718, 95% CI 0.546-0.945, p = 0.018). Effect size was preserved after adjustment for potential confounders. The optimal maximum TTS was estimated at 23.5 weeks based on the AUC, while the cutoff-specific method suggested 24 weeks. Discectomy after this cutoff starts to yield MCID rates under 80%. The 24-week cutoff also coincided with the time point after which the specificity for MCID first drops below 50% and after which the negative predictive value for nonattainment of MCID first surpasses ≥ 20%. The study findings suggest that late lumbar discectomy is linked with poorer patient-reported outcomes and that-in accordance with the literature-a maximum TTS of 6 months should be aimed for.