Adjacent vertebral body osteolysis with bone morphogenetic protein use in transforaminal lumbar interbody fusion

Background context: Recent studies have demonstrated cases of adjacent vertebral body osteolysis when assessing the effect of bone morphogenetic protein (BMP) on fusion rates. However, no study to date has evaluated the course of osteolysis at different periods. Purpose: To determine the incidence and resolution of osteolysis associated with BMP used in transforaminal lumbar interbody fusions (TLIF). Study design: Retrospective review. Patient sample: All TLIF cases using BMP performed at one institution with routine postoperative computed tomography (CT) scans at defined intervals. Outcome measures: Area of osteolysis and fusion as determined by CT scan. Methods: We performed a retrospective analysis of all patients at our facility who underwent TLIF with BMP. Included were all patients who had obtained a CT scan within 48 hours of surgery, 3 to 6 months postoperatively, and 1 to 2 years postoperatively. Areas of osteolysis were defined as lucency within the vertebral body communicating with the interbody spacer that was not present on the immediately postoperative CT scan. Areas of osteolysis were measured in all three planes and the volume used for comparison of the 3 to 6 months CT scans with the greater than 1 year CT scan. Results: Twenty-three patients who underwent TLIF with BMP had obtained CT scans at all time periods required for evaluation. Seventy-eight vertebral bodies/end plates were assessed for osteolysis (39 levels). The incidence of osteolysis 3 to 6 months postoperatively in the adjacent vertebral bodies was 54% compared with 41% at 1 to 2 years. The mean volume of osteolysis was at 0.216 cm³ at 1 to 2 years compared with 0.306 cm³ at 3 to 6 months (p=.082). The area/rate of osteolysis did not appear to significantly affect the rate of fusion or final outcome with an overall union rate of 83%. Conclusions: The rate of osteolysis decreased at 1 year compared with 3 to 6 months, but only 24% of the vertebral bodies with evidence of osteolysis at 3 to 6 months completely resolved by 1 year.