40 patients undergoing single-level posterior lumbar interbody arthrodesis were randomized to receive two polyetheretherketone cages filled with either recombinant human bone morphogenetic protein-2 (rhBMP-2) or an autologous iliac crest bone graft. The purpose of the study was to determine whether there were any differences in clinical and radiographic outcomes between the two groups of patients. Following 24 months of assessments, there were no significant differences in VAS pain, ODI, and SF-36 scores. However, bone density and trabecular bone formation were significantly lower in the rhBMP-2 group.