Enhancement of Low Intensity Pulsed Ultrasound on Spinal Fusion augmented with Stem cell-Bioceramic Composite

Low intensity pulsed ultrasound (LIPUS) was reported to enhance autograft implanted spinal fusion in rabbit model but none reported its effect on bioengineered stem cell-bioceramics composite as bone substitute. Bone marrow was aspirated from proximal femur of 15 week old New Zealand white rabbits. The mesenchymal stem cells (MSC) were then isolated and expanded in number with DMEM/osteogenic supplements/basic fibroblast growth factor. The MSC were impregnated on beta-tricalcium phosphate block (TCP). The bioengineered composite was implanted on L5 and L6 transverse processes of the same animal in posterior spinal fusion with decortication. LIPUS was applied for 20 min daily on the back of rabbit for 7 weeks (LIPUS group, n=6). The untreated animals acted as control group (n=6). The spinal segments were harvested at week 7 and assessed by manual palpation, microCT assessment. The volume of transverse processes was measured by peripheral quantitative computed tomography (pQCT). By manual palpation, 67% of spinal segment in LIPUS group was found to be rigid but 0% in control group. The 3D microCT image of LIUPS group also showed inter-transverse process bony fusion beneath the TCP block whereas was not observed in the control group. In the pQCT result, the volume of transverse processes in LIPUS group was 28.2% greater than the control group. Non-invasive low intensity pulsed ultrasound enhanced tissue engineered stem cell-bioceramics implanted posterior spinal fusion. It will reduce the morbidity due to autograft harvesting.