Ectopic bone formation with joint impingement after posterior lumbar fusion with rhBMP-2

Recombinant human bone morphogenetic protein-2 (rhBMP-2) was recently licensed for local administration during posterior lumbar fusion. In this indication, considerable uncertainty remains about the nature and mechanisms of the many adverse effects of rhBMP-2, such as ectopic bone formation. We report a case of ectopic bone formation with impingement on a facet joint and incapacitating low back pain after minimally invasive transforaminal L5-S1 interbody fusion with local application of rhBMP-2 (InductOs(®)). Revision surgery was eventually performed to alleviate the symptoms by removing the ectopic bone. Caution is in order regarding the use of rhBMP-2 during posterior lumbar fusion. Every effort should be made to minimise the risk of complications.