Accuracy and efficacy of fluoroscopy-guided pars interarticularis injections on immediate and short-term pain relief

Purpose: To determine the accuracy and short-term efficacy of fluoroscopy-guided steroid/anesthetic injections for symptomatic pars interarticularis (pars) defects. Materials and methods: Following IRB approval, all fluoroscopically guided pars injections from a single institution (6/2010 to 3/2016) were retrospectively and independently reviewed by two MSK radiologists. The radiologists evaluated the fluoroscopic images to determine if all of the pars injections associated with each procedure were intra-pars (n = 57 procedures; 106 pars injections), peri-pars (n = 3 procedures; three pars injected), or a combination of intra-pars and peri-pars (n = 6 procedures; 12 pars injected). The patients were asked their pain score (graded on a scale of 0–10) pre-injection, 5–10 min and 1-week post-injection. Age, gender, and fluoroscopic times were recorded. Statistical analysis was performed on the all intra-pars injections only. Results: Exact inter-reader agreement was present in 92 % (112/121) of the injections, with 57 of the procedures (106 pars injections) performed on 41 patients (mean age 36; 18 M, 23 F) all intra-pars. The mean pre-injection and 5–10 min post-injection reduction in pain for the all intra-pars injections was −3.0 units (95 % CI: [−3.9, −2.1] units; p < 0.001) with a mean 1-week post-injection (n = 21 procedures; 38 pars) reduction in pain of −0.7 units (95 % CI [−1.5, 0.0]; p = 0.06). The geometric mean fluoroscopic time per pars injected was 42 s. Conclusions: Over 92 % of fluoroscopically guided injections for symptomatic spondylolysis are technically successful with minimum fluoroscopic time, resulting in statistically significant pain reduction immediately post-injection and a trend in pain reduction 1-week post-injection.