Vascularized Bone Grafting for Reconstruction of Oncologic Defects in the Spine: A Systematic Review and Pooled Analysis of the Literature.

BACKGROUND: Resection of primary spinal tumors requires reconstruction for restoration of spinal column stability. Traditionally, some combination of bone grafting and instrumentation is implemented. However, delayed healing environments are associated with pseudoarthrodesis and failure. Implementation of vascularized bone grafting (VBG) to complement hardware may present a solution. We evaluated the use of VBG in oncologic spinal reconstruction via systematic review and pooled analysis of literature. METHODS: We searched PubMed/MEDLINE, Embase, Cochrane, and Scopus for studies published through September 2017 according to the PRISMA guidelines and performed a pooled analysis of studies with n > 5. Additionally, we performed retrospective review of patients at the Johns Hopkins Hospital that received spinal reconstruction with VBG. RESULTS: We identified 21 eligible studies and executed a pooled analysis of 12. Analysis indicated an 89% (95% confidence interval [CI]: 0.75-1.03) rate of successful union when VBG is employed after primary tumor resection. The overall complication rate was 42% (95% CI: 0.23-0.61) and reoperation rate was 27% (95% CI: 0.12-0.41) in the pooled cohort. Wound complication rate was 18% (95% CI: 0.11-0.26). Fifteen out of 209 patients (7.2%) had instrumentation failure and mean time-to-union was 6 months. Consensus in the literature and in the patients reviewed is that introduction of VBG into irradiated or infected tissue beds proves advantageous given decreased resorption, increased load bearing, and faster consolidation. Downsides to this technique included longer operations, donor-site morbidity, and difficulty in coordinating care. CONCLUSIONS: Our results demonstrate that complication rates using VBG are similar to those reported in studies using non-VBG for similar spinal reconstructions; however, fusion rates are better. Given rapid fusion and possible hardware independence, VBG may be useful in reconstructing defects in patients with longer life expectancies and/or with a history of chemoradiation and/or infection at the site of tumor resection.

C-arm Positioning Using Virtual Fluoroscopy for Image-Guided Surgery.

INTRODUCTION: Fluoroscopically guided procedures often involve repeated acquisitions for C-arm positioning at the cost of radiation exposure and time in the operating room. A virtual fluoroscopy system is reported with the potential of reducing dose and time spent in C-arm positioning, utilizing three key advances: robust 3D-2D registration to a preoperative CT; real-time forward projection on GPU; and a motorized mobile C-arm with encoder feedback on C-arm orientation. METHOD: Geometric calibration of the C-arm was performed offline in two rotational directions (orbit α, orbit ß). Patient registration was performed using image-based 3D-2D registration with an initially acquired radiograph of the patient. This approach for patient registration eliminated the requirement for external tracking devices inside the operating room, allowing virtual fluoroscopy using commonly available systems in fluoroscopically guided procedures within standard surgical workflow. Geometric accuracy was evaluated in terms of projection distance error (PDE) in anatomical fiducials. A pilot study was conducted to evaluate the utility of virtual fluoroscopy to aid C-arm positioning in image guided surgery, assessing potential improvements in time, dose, and agreement between the virtual and desired view. RESULTS: The overall geometric accuracy of DRRs in comparison to the actual radiographs at various C-arm positions was PDE (mean ± std) = 1.6 ± 1.1 mm. The conventional approach required on average 8.0 ± 4.5 radiographs spent "fluoro hunting" to obtain the desired view. Positioning accuracy improved from 2.6° ± 2.3° (in α) and 4.1° ± 5.1° (in ß) in the conventional approach to 1.5° ± 1.3° and 1.8° ± 1.7°, respectively, with the virtual fluoroscopy approach. CONCLUSION: Virtual fluoroscopy could improve accuracy of C-arm positioning and save time and radiation dose in the operating room. Such a system could be valuable to training of fluoroscopy technicians as well as intraoperative use in fluoroscopically guided procedures.