Clinical sequelae after rhBMP-2 use in a minimally invasive transforaminal lumbar interbody fusion.

Background Context: Recent reports of postoperative radiculitis, bone osteolysis, and symptomatic ectopic bone formation after recombinant human bone morphogenetic protein-2 (rhBMP-2) use in transforaminal lumbar interbody fusions (TLIFs) are a cause for concern.

Purpose: To determine the clinical and radiographic complications associated with BMP utilization in a minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) environment.

Study Design/setting: Retrospective clinical case series at a single institution.

Patient Sample: Five hundred seventy-three consecutive patients undergoing an MIS-TLIF.

Outcome Measures: Reoperation rates and total costs associated with complications of rhBMP-2 use and pseudarthrosis.

Methods: A retrospective review of 610 consecutive patients undergoing an MIS-TLIF (2007-2010) by a single surgeon at our institution was performed (mean age 48.7 years, range 26-82 years). All patients underwent an MIS laminectomy with bilateral facetectomy, single TLIF cage, unilateral pedicle screw fixation, and 12 mg (large kit) or 4.2 mg (small kit) of rhBMP-2. The BMP-2 collagen-soaked sponge was placed anteriorly in the disc space, followed by local bone graft, and then the cage was filled only with local bone and no BMP-2. Patients were evaluated at 6 months and 1 year with computed tomography (CT) scan. Those demonstrating neuroforaminal bone growth, osteolysis/cage migration, or pseudarthrosis were reviewed, and cost data including direct cost/procedure for both index and revision surgeries were collected.

Results: Of the 573 patients, 10 (1.7%) underwent 15 additional procedures based on recalcitrant radiculopathy and CT evidence of neuroforaminal bone growth, vertebral body osteolysis, and/or cage migration. Thirty-nine patients (6.8%) underwent reoperation for clinically symptomatic pseudarthrosis. Bone overgrowth was associated with nerve impingement and radiculopathy in all 10 patients (small kit, n=9; large kit, n=1). Osteolysis and cage migration occurred in 2 (20%) of these same 10 patients. Average total costs were calculated per procedure ($19,224), and the costs for reoperation equaled $14,785 per encounter for neuroforaminal bone growth and $20,267 for pseudarthrosis.

Conclusions: Symptomatic ectopic bone formation, vertebral osteolysis, and pseudarthrosis are recognized complications with the use of rhBMP-2 in MIS-TLIFs. Potential causes include improper dosage and a closed space that prevents the egress of the postoperative BMP-2 fluid collection. Management of these complications has a substantial cost for the patient and the surgeon and needs to be considered with the off-label use of rhBMP-2.