Abstract: BACKGROUND: Induced resorption of herniated nucleus pulpous is a minimally invasive, non-invasive and innovative method for the treatment of cervical/lumbar intervertebral disc herniation. After induced resorption of herniated nucleus pulpous, the research about whether cervical/lumbar intervertebral disc can maintain the original biomechanical strength has not been reported.
OBJECTIVE: To measure the height of adjacent vertebral centroid of cervical/lumbar intervertebral disc before and after induced resorption of herniated nucleus pulpous operation to analyze the changes of the biomechanical strength of the intervertebral disc after reclining and to provide a new basis for induced resorption of herniated nucleus pulpous treatment of cervical and lumbar intervertebral disc herniation.    
METHODS: A retrospective analysis was performed on 140 patients with cervical/lumbar intervertebral disc herniation who received induced resorption of herniated nucleus pulpous surgery in the First Affiliated Hospital of Zhengzhou University from January 2013 to January 2023. Related software was used to measure the height of adjacent vertebral centroid of cervical/lumbar intervertebral disc of patients at each follow-up time point before and after induced resorption of herniated nucleus pulpous surgery in Magnetic Resonance Imaging image data under Artificial Intelligence-assisted calibration. Unoperated T1/T2 and T12/L1 segments were taken respectively as controls. Those with preoperative height of adjacent vertebral centroid less than 8% of the corresponding T1/T2 or T12/L1 control segment were in the “height reduction group” (hereafter referred to as group A) and the rest were in the “height unchanged group” (hereafter referred to as group B). The difference of height of adjacent vertebral centroid before and after operation between the group A and the group B was statistically analyzed. Simultaneously, the correlation between the volume of cervical and lumbar herniated discs and the changes of height of adjacent vertebral centroid was analyzed according to the result measured by artificial intelligence. 
RESULTS AND CONCLUSION: (1) The study maintained a total of 140 patients, including 60 cases of cervical disc herniation and 80 cases of lumbar disc herniation. The postoperative follow-up period was 7 days to 12 months. (2) A total of 281 discs were measured in the cervical vertebra group, including 60 intervertebral discs in the control group. The mean value of height of adjacent vertebral centroid before and at the last postoperative follow-up was about 20.46 mm and 20.17 mm, respectively, with no statistical difference (P > 0.05). There were 162 cervical discs in group A. The average height of adjacent vertebral centroid before and after operation was 16.65 mm and 15.92 mm, respectively, with no statistically significant difference (P > 0.05). The mean cervical disc herniation volume before and after surgery was 510.28 mm³ and 364.76 mm³, respectively, which was not significantly correlated with height of adjacent vertebral centroid change (P > 0.05). There were 64 discs in the group B, with average of 20.15 mm before operation and 19.09 mm at the last follow-up, and there was no significant difference (P > 0.05). The mean volume of cervical disc herniation before and after surgery was 515.32 mm³ and 361.98 mm³, respectively, and there was no significant correlation with the change of height of adjacent vertebral centroid (P > 0.05). (3) A total of 258 discs were measured in the lumbar spine group, of which 80 intervertebral discs in the control group, the average height of adjacent vertebral centroid was 33.03 mm before operation and 32.40 mm at the last follow-up, and there was no significant difference. There were 59 discs in the group A, and the average height of adjacent vertebral centroid before and after operation was 30.08 mm and 31.67 mm, respectively, with no statistically significant difference. The mean volume of lumbar disc herniation before and after operation was 690.51 mm³ and 496.58 mm³, respectively, and there was no significant correlation with the change of height of adjacent vertebral centroid (P > 0.05). There were 119 discs in the group B, with an average height of adjacent vertebral centroid of 35.91 mm before surgery and 34.12 mm at the last follow-up. The mean volume of lumbar disc herniation before and after operation was 698.70 mm³ and 535.99 mm³, respectively, and there was no significant correlation with the change of height of adjacent vertebral centroid. (4) It is concluded that patients with cervical/lumbar intervertebral disc herniation can maintain the same intervertebral height level after induced resorption of herniated nucleus pulpous regardless of whether the intervertebral height has decreased before operation. It can be inferred that the resorption of the herniated disc does not affect its biomechanical strength. It suggests that induced resorption of herniated nucleus pulpous surgery should be performed before the intervertebral height of the degenerate segment has decreased. The induced resorption of herniated nucleus pulpous is more valuable to maintain the biomechanical strength of the resorptive disc.

Key words:

intervertebral disc, lumbar disc herniation, cervical disc herniation, centroid, magnetic resonance image, artificial intelligence, biomechanics