# Pain relief after CT-guided pars injections in lumbar spondylolysis: analysis of MRI findings and CT-contrast distribution

## TL;DR

This study found that CT-guided injections for lower back pain in spondylolysis patients can provide significant pain relief, with MRI showing bone marrow edema as a key predictor of success.

## Contribution

The study identifies isthmic bone marrow edema on MRI as a novel predictor of successful pain relief after CT-guided pars injections in spondylolysis patients.

## Key findings

- Pain relief was reported in 55% of patients one month after CT-guided pars injections.
- Isthmic bone marrow edema on MRI was strongly associated with successful pain relief.
- CT-contrast distribution during injection did not predict pain relief outcomes.

## Abstract

To analyze pain relief in spondylolysis patients with chronic lower back pain (CLBP) after CT-guided bilateral pars injections and investigate MRI findings and CT-contrast distribution as predictors of successful pain relief.

Patients with bilateral spondylolysis and CLBP receiving CT-guided pars injections were assessed for pain relief 15 min and 1 month post-injection, using a numeric rating scale (NRS) and percentage pain reduction (PPR). Two radiologists assessed lumbar findings on prior MRI and CT-contrast distribution during injection. Successful pain relief was defined as PPR ≥ 50%. Logistic regression was used to investigate imaging predictors of successful pain relief.

In 134 patients (mean age 43.9 ± 16.2 years), average NRS pain score dropped from 5.7 at baseline to 3.7 (PPR 34 ± 47.3%) 15 min post-injection, and to 3.2 (PPR 48 ± 43%) 1-month post-injection (all p < 0.001). At 15 min, 56/134 patients (42%) and at 1-month post-injection, 73/134 patients (55%) reported PPR ≥ 50%. Isthmic bone marrow edema (BME) was the only MRI predictor associated with successful pain relief (all p ≤ 0.006). Patients with isthmic BME were 6–9 times more likely to show successful pain relief 15 min post-injection, and 2–3 times more likely to show successful pain relief 1 month post-injection (all p ≤ 0.046). CT-contrast distribution did not correlate with pain relief (all p ≥ 0.27).

Pars injections allowed successful pain relief in 55% of spondylolysis patients after 1 month, with a PPR of 48% on average from baseline. Isthmic BME was an important MRI predictor of successful pain relief for pars injections, whereas CT-contrast distribution was not.

Question Imaging predictors of successful pain relief in lumbar spondylolysis patients with CLBP receiving bilateral pars injections are unknown.

Findings Isthmic BME on MRI was a significant predictor of successful pain relief immediately and 1-month post-injection. CT-contrast distribution did not influence pain relief.

Clinical relevance CT-guided pars injections offer successful pain relief in spondylolysis patients with CLBP. Isthmic BME on MRI is a significant predictor for successful pain relief, whereas CT-contrast distribution during injection is not.