278. Allograft reconstructed iliac bone graft donor site remodels to viable bone and its preliminary clinical effectiveness in revision fusion

Abstract

BACKGROUND CONTEXT Bone autograft options may be limited for revision spinal fusion, particularly in long deformity cases where iliac fixation or prior IBG harvest are present. Contralateral IBG may not be available or was previously harvested. Alternatives such as bone morphogenic protein, BMP, at some facilities is not available for off-label use or due to expense. Nonviable alternatives have inconsistent ability to obtain arthrodesis in revision cases. Allograft reconstructed iliac bone graft donor site has been used to decrease donor site pain; it may also be a source of bone graft in patients with multiple prior fusions who need another fusion. PURPOSE The purpose of this study was to assess the viability of bone graft donor sites reconstructed with bone allograft. A secondary purpose of this prospective cohort study was to ascertain whether the reconstructed iliac bone graft, RIBG, sites could be reharvested for successful arthrodesis in revision fusion. STUDY DESIGN/SETTING Histologic and two cohort clinical prospective study. PATIENT SAMPLE Consecutive patients who had secondary thoracolumbar spinal fusion (pseudarthrosis repair or fusion extension) using RIBG. All these patients had their initial fusion with IBG and reconstruction of the bone graft donor site with cancellous allograft. OUTCOME MEASURES Histology of RIBG biopsies (lacunae and marrow) vs controls; clinical VAS, ODI outcomes. METHODS Revision spinal fusion patients, n=16, who had their iliac bone graft donor site backfilled with allograft bone at their initial fusion and subsequently had secondary fusion surgery for a pseudarthrosis repair or fusion extension had biopsies obtained at the time of secondary fusion. Histology analyzed the RIBG biopsies for viability and was compared to controls. One-year postop CT scans and 2+ yr outcomes measures (LBP VAS & ODI) evaluated the clinical success of the secondary fusion surgery using RIBG and compared to revision fusion controls using contralateral IBG. RESULTS Histology found filled lacunae average 83%, SD 14%, and the bone marrow was hypocellular in 2/3 of cases. Control patients had average 87%, SD; 8% and no hypocellularity. CT scans of the lumbar fusions utilizing RIBG, often combined with bone growth stimulator or bone morphogenic protein (BMP), demonstrated solid fusions in 15 of 16 patients. CT scan fusion rates of the IBG or BMP control cohorts were approximately 80%. Clinical improvement was significant (3.8 VAS decrease, p CONCLUSIONS RIBG using cancellous bone allograft remodels into viable bone autograft. This study is the first to report the histological viability of RIBG site and assess the feasibility of its use in revision fusion. RIBG may be useful in secondary fusion procedures if IBG or BMP are of limited availability. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.