Objective: This is a descriptive study of the incidence of spinal injury by crash type using NASS-CDS. It provides an understanding of impacts to the underbody of the vehicle and injuries to the lumbar spine by reviewing electronic cases in NASS-CDS to determine crash circumstances for fractures of the lumbar spine with underbody impacts. Methods: 1997-2015 NASS-CDS was evaluated for serious injury (MAIS 3+F) to front-seat occupants by seatbelt use and crash type in 1994+ MY vehicles. Underbody impacts were defined by GAD1 = U without a rollover. Serious injury was defined as MAIS 3+F. Spinal injuries AIS 3+ were separated into cervical, thoracic and lumbar regions. Weighted data was determined using ratio weight. NASS-CDS electronic cases were downloaded from NHTSA with AIS 3+ lumbar spine injuries in underbody impacts. Results: There were 2,160 MAIS 3+F injured occupants in underbody impacts. This was 0.23% of all serious injury. There were 914 (42.3%) AIS 3+ spinal injuries in underbody impacts with 88.3% in the lumbar spine. The 807 lumbar spine injuries represented 4.1% of all AIS 3+ spinal injury. There were six electronic cases with AIS 3+ lumbar spine injury in underbody impacts. They involved off-road excursions at high speed with underbody impacts from changes in terrain. All involved front airbag deployments. Four of the six cases involved multiple lumbar fractures from compression of the spine. Conclusions: Serious spinal injuries are rare in underbody impacts. When they occur, they are primarily compression (burst) fractures of the lumbar spine caused by vertical loads compressing and flexing the spine.