[Biomechanical aspects of complex reconstructions following radical resection of thoracolumbar spinal tumors]

Revision strategy and follow-up for implant failure in a case of combined anterior and posterior reconstruction after three-level en bloc vertebral body replacement and replacement of the aorta for chondrosarcoma of the thoracic spine

OBJECTIVE

In 2013, we reported a case of combined anterior and posterior reconstruction after three-level en bloc vertebral body replacement and replacement of the aorta for chondrosarcoma of the thoracic spine. Eight years after, we observed an implant failure and now report on revision strategy and 2-year follow-up (f/u) after revision.

METHODS

We report about the 2-year f/u of the same now 51-year-old gravedigger who needed to undergo revision surgery after implant failure. We did a combined anterior and posterior correction vertebral interbody fusion by (1) removal of broken screws in Th9 and L2, removal of broken titanium bars, correction of kyphosis, enhancement of the vertebral interbody fusion from Th8 to L4 using monoaxial titanium screws and cancellous bone transplantation and (2) removal of the broken plate and the loose cage, implantation of a novel expandable PEEK cage from Th11 to L1 and anterior stabilization from Th9/10 to L2/3, as well as autologous and allogeneic cancellous bone transplantation.

RESULTS

Two years after revision surgery, the patient presented fully reintegrated without any complains. No painkillers needed to be taken. Pain was reported with 2 out of 10 on the VAS.

CONCLUSION

Both procedures offer a good primary stabilization with excellent pain reduction and good return to life. Limited information on long-term survivors is known. Therefore, the theoretical advantage of a biological solution needs to be checked in the long-term f/u for consistency.

Quantitative in vivo fusion assessment by (18)F-fluoride PET/CT following en bloc spondylectomy

PURPOSE

The purpose of this retrospective analyses was to evaluate the bone viability in the ventral column of the spine following large segmental defect reconstructions. Osseous integration of implants following spinal fusion procedures is an essential precondition to provide adequate mechanical strength to any applied forces and subsequently satisfying patient outcomes. Although CT scan is the non-invasive gold standard for fusion assessment, it lacks the ability to visualize bone viability and, therefore, discrepancy remains about sensitivity and specificity of CT as evaluation tool of spinal fusion.

METHODS

A novel modality, (18)F Fluoride PET/CT, specifically allows quantitative in vivo evaluation of metabolic activity of the osseous integration. Bone viability following large segmental reconstructions in patients after mono- and multi-level en bloc spondylectomies (EBS) was analyzed. Spinal fusion was assessed on plain radiographs and CT scans according to the FDA fusion criteria as well as (18)F PET/CT.

RESULTS

A total of eight patients underwent (18)F PET/CT were included (one 4-level-, one 3-level, two 2-level and four 1-level EBS). The average follow-up between EBS and radiographic studies was 24.8 months. On plain radiographs and CT scans, successful fusion was confirmed in all patients. However, (18)F PET/CT showed non-union in all cases. The metabolic bone activity within the cage was fourfold decreased compared to the reference vertebra, whereas the metabolic activity of the adjacent endplates was 1.6-fold increased compared to the reference vertebra.

CONCLUSION

This study suggests a discrepancy between fusion rates assessed by plain radiographs and CT scan compared to (18)F PET/CT.