Removal of infected bone in-growth pelvic fixation implants and microcomputed tomography analysis of osseous integration: illustrative case

Background: A novel pelvic fixation screw fusion device (iFuse Bedrock Granite implant) was designed to promote bony fusion through self-harvesting fenestrations throughout the outer screw shank. Bone on-growth and in-growth using this design have been demonstrated in a sheep model, but data from human subjects have not been reported. A 66-year-old medically complex female with 2 prior spine fusions developed spondylodiscitis cephalad to a prior fusion, requiring the removal of instrumentation, which included screw fusion devices.

Observations: Within this case report, the authors present a novel bone-preserving technique for the removal of well-fixed screw fusion devices. One screw backed out with a driver, and the other 3 had to be trephined out. One screw sheared off the T30 torque driver, implying a removal torque greater than 270 inch-lbs (30.5 Nm). In addition, the removed implants were analyzed using microcomputed tomography (micro-CT) and demonstrated bone on-growth, in-growth, and through-growth in all 4 screws.

Lessons: Micro-CT clearly demonstrated osseous integration of the screw fusion devices and provided significant support for the use of these implants for lumbopelvic fixation. The authors' hope is that the novel bone-preserving technique will help other surgeons when faced with the difficult removal of well-fixed screw fusion devices. https://thejns.org/doi/10.3171/CASE24274.