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

OBJECTIVES

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.

MATERIALS AND METHODS

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.

RESULTS

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).

CONCLUSION

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.

KEY POINTS

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.