Validation of Impaction Grafting for Single-Level Transforaminal Lumbar Interbody Fusion-Technical Pearls and MicroCT Analysis

STUDY DESIGN: Cadaveric study. BACKGROUND CONTEXT: Transforaminal lumbar interbody fusion (TLIF) represents a well-documented operative surgical technique utilized in the management of lumbar pathology requiring interbody arthrodesis. The microstructural properties of impaction grafting (IG) after TLIF has yet to be reported. PURPOSE: The current study was designed first, to quantify the degree, to which IG augmentation would increase intrabody final bone volume and bone graft surface contact area with the endplates; secondly to quantify the volumes of locally harvested bone and bone needed for maximal impaction. MATERIALS AND METHODS: Three cadaveric lumbosacral spine specimens were dissected into L1-L2, L3-L4, and L5-S1 motion segments for a total of 9 functional spinal units. Each interbody unit underwent a TLIF procedure with the implantation of an interbody spacer containing autogenous morselized bone. Microcomputed tomography scans were then performed to evaluate the final bone volume and bone surface contact area (BSCA). Subsequently, IG augmented TLIF procedure was carried and microcomputed tomography scans were repeated. RESULTS: IG augmentation of TLIF exhibited a 346% increase in final bone volume (TLIF: 0.30 ± 0.07 cm 3 ; IG-TLIF: 1.34 ± 0.42 cm 3 ; P < 0.05) and a 152% increase in BSCA (TLIF: 45.06 ± 15.47%; IG-TLIF: 68.28 ± 6.85%; P < 0.05) when compared with the nonimpacted TLIF treatment. In addition, the average amount of autogenous bone collected was 8.21±2.08 cm 3 , which sufficiently fulfilled the requirements for bone grafting (TLIF: 1.23 ± 0.40 cm 3 ; IG-TLIF 6.42 ± 1.20 cm 3 ). CONCLUSIONS: IG augmentation of TLIF significantly improved final bone volume in the disc space and BSCA with vertebral endplates in vitro. CLINICAL SIGNIFICANCE: Greater BSCA and final volume of bone graft reflect promisingly on their potential to increase fusion rates. Clinical studies will be needed to corroborate these findings.