• Vivek Joseph and Yoga Raja Rampersaud.
• Divisions of Orthopedic Surgery, Krembil Neuroscience Centre, University Health Network, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.
• Spine. 2007 Dec 1;32(25):2885-90.

Study DesignObservational study with prospective CT analysis.ObjectiveTo assess the incidence and clinical sequelae of epidural bone formation following the adjunctive use of recombinant bone morphogenetic protein 2 (rhBMP2) with local autogenous bone graft use of (rhBMP2) in minimal access interbody (PLIF and TLIF) fusions.Summary Of Background DataThe use of rhBMP2 for interbody fusion is associated with high fusion rates. However, for posterior approaches, concerns regarding heterotopic bone formation within the epidural space have been raised.MethodsAn independent CT analysis of 33 consecutive patients following minimal access lumbar fusion (PLIF [n = 10] or TLIF [n = 23]) with [n = 23] and without [n = 10] rhBMP2 was performed. Bone formation was graded in a centrifugal manner (intradiscal, anular/ALL/PLL, epidural [canal/foramen] and beyond the spine). In all BMP cases, a constant dose of 4.2 mg/disc level was administered (lowest commercially available dose). In all cases, local autograft was used. Review and assessment of prospectively collected outcomes data were performed.ResultsAverage clinical and CT (minimum 6 months) follow-up was 25.0 and 7.9 months, respectively. Bridging bone (fusion) was seen in 100% of the BMP group and 90% without BMP. Epidural bone formation occurred in 20.8% with the use of BMP (5 levels: n = 1 spinal canal and n = 4 within the foramen) compared with 8.3% (1 level: canal) without BMP. Foraminal bone formation was seen only in the TLIF group. All epidural bone formation was heterotopic, and no ectopic bone formation occurred. There were no clinical sequelae associated with heterotopic bone formation. The mean preoperative and postoperative Oswestry Disability Index was 50.2% (range, 25%-75%) and 11.3% (range, 0%-38%) respectively.ConclusionAlthough the adjunctive use of rhBMP2 is associated with a higher incidence of heterotopic bone, there does not seem to be any associated clinical sequelae.

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