Abstract
Background
There are no published studies investigating predictive values of psychological distress on effectiveness of epidural injection.
Aims
To evaluate response to epidural injection (EI) in patients with chronic lower back pain (CLBP) with and without psychological distress.
Methods
96 patients with CLBP were recruited to this prospective cohort study. They had preoperative level of distress measured using Modified Zung Index (MZI) and Modified Somatic Perception Questionnaire (MSPQ); pain with Visual Analogue Score (VAS) and McGill Pain Questionnaire (MPQ); back related disability with Oswestry Disability Index (ODI). Fluoroscopic caudal EI comprising 80 mg methylprednisolone and 8 mg of lignocaine was performed. Scores were repeated at 6, 12, and 26 weeks. Successful outcome was Minimal Clinically Important Change (MCIC) in any given measure.
Results
There were 62.5% not-distressed patients, 3.1% somatising, 15.6% depressed and 18.8% with mixed distress. Preoperative VAS was 82.4, MPQ 18.2 and ODI 51.6. Distress was associated with worse MPQ and ODI. Average VAS and MPQ improved significantly at 6 and 26 weeks. Mean change of ODI was significant but less than MCIC. Average magnitude of change of VAS and ODI did not differ between distressed and not-distressed. MPQ improved significantly more in the distressed. MZI was significant predictor of VAS-MCIC at 6 weeks while MZI and MSPQ at 6 months. None could predict this outcome independently. MSPQ was the only individual predictor of MPQ-MCIC at any time; MSPQ≥8 could predict MPQ-MCIC with 53%-sensitivity and 78%-specificity. MZI was significant predictor of ODI-MCIC but not individually.88% patients were satisfied with the treatment at 6 weeks and 63% at 6 months (significantly higher rate if somatising).
Conclusions
Early psychological screen was correlated with outcome following epidural injection in CLBP and capable of predicting some response to treatment. Minimal, short-lived improvement of distress was not related to post-treatment CLBP measures.
