Michielsen J, Sys J, Rigaux A, Bertrand C. J Bone Joint Surg Am. 2013; 95(10):873–880. doi: 10.2106/JBJS.L.00137.
The authors reported a single-center, single-surgeon, prospective, randomized, controlled trial undertaken to assess the clinical and imaging findings of the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) vs autologous bone in patients treated with an instrumented single-level posterior lumbar interbody arthrodesis with polyetheretherketone cages.
Forty patients were randomized into either treatment with 8 mg of rhBMP-2 (study group; n=20) or treatment with 2.5 mL of autologous bone harvested unilaterally from the iliac wing (control group; n=20).
Inclusion criteria included lytic and degenerative spondylolisthesis, disk degeneration that was not responsive to non-operative treatment modalities for at least 6 months, disk herniation in patients with severe disk degeneration and persisting sciatica despite epidural steroid injections, and single-level disk abnormality.
Exclusion criteria included a history of spinal surgery other than diskectomy; chronic use of corticosteroids or non-steroidal anti-inflammatory drugs; skeletally immature patients or patients older than 70 years; history of osteoporosis, systemic disease, or a malignant lesion; disk abnormality at adjacent levels; and patients undergoing multilevel surgery.
A posterior lumbar interbody arthrodesis with posterior pedicle screw fixation was performed. Pedicle screws were placed under fluoroscopic guidance, followed by a complete laminectomy and diskectomy. The vertebral body endplates were prepared by curetting until point bleeding was seen. A titanium segmental instrumentation rod system (Colorado 2; Medtronic Sofamor Danek, Memphis, Tennessee) was used for posterior instrumentation, and 2 polyetheretherketone cages (Telamon; Medtronic Sofamor Danek) were used for interbody arthrodesis. The bone morphogenetic protein used was rhBMP-2 on an absorbable collagen sponge (InductOs; Wyeth Europa, Taplow, United Kingdom).
Clinical results were measured using the Oswestry Disability Index, the Short Form 36, and the visual analog scale for pain preoperatively and at 3, 6, 12, and 24 months postoperatively. Imaging results were measured using anterior, lateral, and flexion-extension radiographs of the lumbar preoperatively and at 3, 6, and 12 months postoperatively, and computed tomography scans with coronal and sagittal reconstructions at 3, 6, and 12 months postoperatively. Using the computed tomography scans, the status of the interbody fusion was quantified using the bridging trabecular bone scale.
Baseline demographic data showed no significant difference between groups, except for body mass index, which was higher in the study group (P=.032). The operative procedure took significantly longer (P=.010) and blood loss was significantly higher (P=.008) in the control group.
No significant differences existed in the clinical results between the groups at each postoperative visit. At 3 months, endplate resorption was noted around the cages in all patients in the study group. Bridging trabecular bone scale scores and bone density measures were significantly lower in the study group. Osteolysis and ectopic bone formation occurred in 7 of 19 patients in the study group and did not occur in the control group. At 1 year postoperatively, computed tomography scans showed osseous healing in all patients.
Clinical results between the groups at 24 months postoperatively were not significant with regard to improvement in visual analog scale scores (P=.987), Oswestry Disability Index scores (P=.577), and both the Short Form 36 physical (P=.536) and mental (P=.278) component summary scores between the groups.
Imaging results revealed that bone density measures were significantly different between the groups at 3, 6, and 12 months postoperatively (P=.002, .024, and .014, respectively). A significant difference was also found between the groups with regard to interbody healing on the bridging trabecular bone scale at 3, 6, and 12 months postoperatively (P=.021, .004, and .014, respectively). Fusion on the computed tomography scan (a bridging trabecular bone scale score of 3, 4, or 5) was ultimately achieved in all patients.
No clinical difference was found when rhBMP-2 was used in posterior lumbar interbody arthrodesis compared with autologous bone. On computed tomography scans, fusion was equally achieved when rh-BMP-2 was used; however, trabecular bone formation occurred at a slower rate and interbody bone density was lower within the first postoperative year after surgery when rhBMP-2 was used.