Randomised and non-randomised clinical trials (RCTs and non-RCTs) of chemonucleolysis with chymopapain or collagenase compared to placebo or surgery in patients with symptomatic lumbar disc herniation with sciatic pain who had undergone computerised tomography (CT), magnetic resonance imaging (MRI) or myelography were eligible for inclusion. Follow-up ranged from three months to two years. Patients ranged in age from 16 to 77 years. Most studies administered 4,000 IU chymopapain; the rest used between 2,000 IU and 4,000 IU. The outcome of interest was pain relief.
The authors stated neither how studies were selected for the review nor how many reviewers performed the study selection.