In vivo clinical CT scans of the lumbar spine were acquired using a Revolution EVO CT system (GE Medical Systems, Switzerland) to evaluate disc height changes over time. Scans were acquired preoperatively, immediately postoperatively (W0), 4 weeks postinjury (W4), W8, and after euthanasia at W12. Sheep were sedated and anesthetized before in vivo clinical CT imaging as described above (Section 2.4 ). The CT images were obtained with a slice thickness and spacing of 0.625 and 0.312 mm, respectively. Tube voltage was 120 kVp and the tube current was 300 mA. Disc height was measured by a blinded observer using Amira software (Amira 6.5, FEI SAS, Thermo Fisher Scientific) as previously described.
48 (link) Briefly, lumbar vertebrae were semi‐automatically segmented, and then the shortest distance between each point on the cranial IVD extremity and the caudal IVD extremity was measured for each IVD. The average disc height was calculated as the arithmetic mean of all points along an individual IVD, which was approximately 5000 points. Postoperative disc heights were expressed as a percentage of the preoperative disc heights. Therefore, a relative disc height of less than 100% postoperatively would represent a disc height loss when compared to preoperative values.
48 (link) Briefly, lumbar vertebrae were semi‐automatically segmented, and then the shortest distance between each point on the cranial IVD extremity and the caudal IVD extremity was measured for each IVD. The average disc height was calculated as the arithmetic mean of all points along an individual IVD, which was approximately 5000 points. Postoperative disc heights were expressed as a percentage of the preoperative disc heights. Therefore, a relative disc height of less than 100% postoperatively would represent a disc height loss when compared to preoperative values.
