Auburn Research Day 2022

Yarrow JF 1 ; Wnek RD 1 ; Conover CF 1 ; Reynolds MC 1 ; Buckley KH 1 ; Kura JR 1 ; Sutor TW 1 ; Otzel DM 1 ; Mattingly AJ 2 ; Croft S 2 ; Aguirre JI 3 ; Borst SE 1 ; Beck DT 4 ; McCullough DJ 4 1 Malcom Randall Department of Veterans Affairs Medical Center, Gainesville, FL; 2 Florida/South Georgia Veterans Health System, Gainesville, FL; 3 University of Florida College of Veterinary Medicine, Gainesville, FL; 4 Edward Via College of Osteopathic Medicine-Auburn Campus B i omed i ca l Resea rch | VCOM Facu l t y Bone Loss After Severe Spinal Cord Injury Coincides with Reduced Bone Formation and Precedes Bone Blood Flow Deficits 80

Diminished bone perfusion develops in response to disuse and has been proposed as a mechanism underlying bone loss. Bone blood flow (BF) has not been investigated within the unique context of severe contusion spinal cord injury (SCI), a condition that produces neurogenic bone loss that is precipitated by disuse and other physiological consequences of central nervous system injury. Herein, 4-mo-old male Sprague–Dawley rats received T9 laminectomy (SHAM) or laminectomy with severe contusion SCI (n = 20/group). Time course assessments of hindlimb bone microstructure and bone perfusion were performed in vivo at 1- and 2-wk post-surgery via microcomputed tomography (microCT) and intracardiac microsphere infusion, respectively, and bone turnover indices were determined via histomorphometry. Both groups exhibited cancellous bone loss beginning in the initial postsurgical week, with cancellous and cortical

bone deficits progressing only in SCI thereafter. Trabecular bone deterioration coincided with uncoupled bone turnover after SCI, as indicated by signs of ongoing osteoclast-mediated bone resorption and a near-complete absence of osteoblasts and cancellous bone formation. Bone BF was not different between groups at 1 wk, when both groups displayed bone loss. In comparison, femur and tibia perfusion was 30%–40% lower in SCI versus SHAM at 2 wk, with the most pronounced regional BF deficits occurring at the distal femur. Significant associations existed between distal femur BF and cancellous and cortical bone loss indices. Our data provide the first direct evidence indicating that bone BF deficits develop in response to SCI and temporally coincide with suppressed bone formation and with cancellous and cortical bone deterioration.

Di sc i p l i ne | Med i ca l Res i dent /Pos t Doc Proximity of Great Vessels During Dlif Procedure: An Anatomic Study 81

Douglas Pahl, MD; Gil Gomez, DO; Aaron Joiner, DO; Dave Barns, DO; Tyler Ellett, DO The Hughston Foundation

Body: Minimally invasive- direct lateral interbody fusion, DLIF, or extreme lateral interbody fusion is becoming an increasingly popular surgical technique for lumbar fusion. It allows for minimally invasive exposure, minimal blood loss, less soft tissue disruption, shorter hospital stays, reduced cost, and good fusion results. This new technique does not come without risk, which includes potential neurovascular insult, and as the method grows in popularity, the complications can be expected to increase. Little research has been done exploring vascular injury during XLIF/DLIF approach, with no known anatomic studies evaluating the distance from the lumbar vertebrae to the major vascular structures. The purpose of this study is to assess the average distance in adults during the XLIF/DLIF approach from the lumbar vertebrae to the major vessels. Methods: Ten subjects were imaged with an MRI in the right and left lateral recumbent position with a bump and supine positions to evaluate the location of the aorta, IVC, iliac vessels, kidneys, and psoas muscle. Measurements were obtained from a line drawn through the center of the disc at each intervertebral level. All MRI studies were performed using a single 1.5T magnet (GE platform). Two fellowship-trained MSK radiologists will independently evaluate imaging. Results: When positioning the patient in the left lateral decubitus (LLD), the shortest distance between the inferior vena cava and L1-2, L2-3, L3-4, L4-5 were 1.66, 1.60, 1.45, and 1.20cm, respectively. While

in the right lateral decubitus (RLD), the shortest distance between the aorta and L1-2, L2-3, L3-4, L4-5 were 2.37, 2.69, 2.47, and 2.70cm, respectively. From supine to LLD, the aorta shifted anteriorly 2.4mm at L1-2. L2-3 and L3-4 displayed limited aorta displacement posteriorly, up to 1.2mm. During the same positional change, the inferior vena cava displaced anteriorly at the levels of L1-2, L2-3, L3-4, by 11.0, 6.0, and 1.0mm, respectively. At L4-5, the inferior vena cava translated 2.2mm posteriorly. From supine to RLD, the aorta displaced anteriorly by 6.5, 3.5, and 3.7mm at L1-2, L2-3, and L3-4, respectively. During the same positional change, the inferior vena cava displaced anteriorly at L1-2 and L2-3 by 2.9 and 4.0mm, respectively. Posterior displacement of the inferior vena cava occurred at L3-4 and L4-5 by 1.8 and 1.7mm, respectively. Conclusion: Patient positioning impacts the movement of major vascular structures away from the surgical corridor. The inferior vena cava demonstrated more significant movement away from the surgical corridor when in the LLD compared to the aorta. Right-sided approaches may be safer as the aorta is the furthest away from the surgical corridor.

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