Successful Arthrodesis Using a Blended Allograft and Autograft Mixture in Lumbar Interbody Fusion: A Retrospective Case Series

Introduction Achieving successful arthrodesis after lumbar interbody fusion remains a challenge, especially for minimally invasive surgical approaches that limit the amount of local bone autograft. However, using an allograft blend as an autograft extension mixture may hold promise but requires further research. The purpose of this study is to examine the impact of an allograft blend added to autograft on the quality of arthrodesis after lumbar interbody fusion in adult patients. Methods This study is a retrospective case series of adult patients (>21 years old) who underwent lumbar interbody fusion between October 2021 and January 2022, performed by a single spine surgeon. The quality of arthrodesis was assessed via the Bridwell grade (I-IV) for up to six months. The impact of surgical technique, age, sex, or amount of allograft utilized during fusion on Bridwell grade was assessed. Results Patients (n = 18; 27 levels fused) had a mean age of 58.6 (1.9) years and a mean BMI of 32.8 (1.2) kilograms per meter squared (kg/m²). A mean of 18.0 (standard deviation = 2.4) cubic centimeters (cc) (range: 3.4-50.0 cc) of allograft was used per fused level. A Bridwell grade of I (successful arthrodesis) was achieved at three months in 11.1% (3/27) of fusions and at six months in 85.2% (23/27) of fusions. Four fusions remained at a Bridwell grade of II at six months and subsequently achieved complete arthrodesis at 12 months. No patients received a Bridwell grade of IV (lucency with collapse of graft) at three- or six-month follow-up. There was no difference in Bridwell grade when stratified by surgical technique, age, sex, or amount of allograft used. Conclusion The allograft and autograft blend utilized in this study resulted in successful arthrodesis at all fused levels after one year, irrespective of surgical technique or other patient factors. Prospective studies with larger sample sizes are needed to corroborate the findings of this small case series.