P32. Morphological analysis of OPLL progression in cervical spinal cord injury cases treated with posterior fusion

Abstract

Background Context

The patients with cervical ossification of the posterior longitudinal ligament (OPLL) have a high frequency in Asian, with a reported incidence of 6.3% in Japan. The presence of OPLL is a risk factor for cervical spinal cord injury, with some cases resulting from minor trauma such as falls. In previous studies, the characteristics of OPLL after surgery were mentioned, however, there is no consensus on cervical spinal cord injury with OPLL after fusion surgery.

Purpose

To investigate the natural progress of ossification in cervical spinal cord injury cases with OPLL treated by posterior fusion surgery.

Study Design/Setting

Study design is retrospective study.

Patient Sample

The subjects included 42 cases of cervical spinal cord injuries with OPLL that underwent posterior fusion surgery between 2017 and 2021 and were amenable to follow-up with CT for more than 6 months.

Outcome Measures

N/A.

Methods

We investigated the presence or absence of union of the OPLL at the level of the spinal cord injury on postoperative CT and the presence or absence of ossification of the anterior longitudinal ligament (OALL) on CT at the time of injury. We measured the thickness of OPLL at the level of injury by CT at the time of injury and 6 months after surgery and calculated the difference in the thickness of OPLL. We divided the subjects into two groups: one with the union of OPLL after surgery and one without union. We performed comparative analyses between the two groups and binary logistic regression analyses on the differences in thickness of OPLL, DM, and OALL. In addition, we assessed the rates of union for OPLL and OALL longitudinally at intervals of 3 months, 6 months, 1 year, and 2 years postoperatively.

Results

The mean age at the time of injury was 69.0 (44-87) years, the mean observation period was 15.9 (6-63) months, including 38 males and 4 females, the mean BMI was 25.0 (19.0-34.6) kg/m², and 14 cases had DM. At the final observation, 30 cases (71.4%) got the union of OPLL at the level of the injury, and the mean time from injury to the union of OPLL was 8.4 (2-28) months. Thirty patients had OALL on CT at the time of injury. The mean difference in the thickness of the OPLL between the time of injury and 6 months after surgery was -0.07 (-1.2-0.6) mm, with no diameter enlargement. There were no significant differences between the 2 groups in age, gender, BMI, presence of DM, and the difference in the thickness of OPLL. In the group with the union of OPLL, they had OALL at the time of injury significantly by Pearson's chi-square test (p=.007). We found OALL as an independent factor in the binary logistic regression analysis. the rate of transformation into continuous type both OPLL and OALL at intervals of 3 months, 6 months, 1 year, and 2 years were as follows: OPLL was 12%, 37%, 57%, 73%, and OALL was 30%, 42%, 52%, 55%.

Conclusions

This study suggested that spinal fusion surgery has some effect of transforming OPLL into the continuous type and preventing the increase in thickness of their ossification. Cervical OPLL showed transformation into continuous type in approximately 70% at the level of posterior fusion surgery and the rate of transformation into continuous type in both OPLL and OALL showed a progressive escalation over the specified period. Given the significantly higher incidence of OALL at the time of injury in the OPLL contentious transforming group, there may be subgroups within cervical OPLL that possess factors of the union of OPLL. The patients after posterior fusion surgery for cervical spinal cord injuries with OPLL had no increase in the thickness of OPLL and no deterioration of paralysis.

FDA Device/Drug Status

This abstract does not discuss or include any applicable devices or drugs.