Long-term loss of intervertebral disc height after posterior cervical surgery for ossification of the posterior longitudinal ligament: a retrospective study with more than 3 years of follow-up.

BACKGROUND

Posterior decompression is a common treatment for cervical OPLL but may accelerate intervertebral disc degeneration by disrupting posterior tension-band structures. The long-term behavior of intervertebral disc height (IDH) after surgery remains poorly understood.

PURPOSE: To evaluate the prevalence and radiographic predictors of long-term IDH loss following posterior cervical surgery for OPLL.

METHODS

This single-center retrospective study included 108 patients who underwent posterior decompression for cervical OPLL between 2007 and 2020, with ≥ 3 years of follow-up. Total C3-C7 IDH was measured on midsagittal CT preoperatively and at final follow-up. Patients were grouped by IDH loss (> 1 mm vs. ≤ 1 mm). Radiographic and clinical parameters were compared. Multivariate logistic regression with AIC-based stepwise selection identified independent predictors. Model performance was assessed by AUC and F1 score.

RESULTS

At a median follow-up of 61 months, 24.1% of patients exhibited IDH loss > 1 mm. The IDH group had a larger preoperative C0-2 Cobb angle (27.4° vs. 22.9°, P = 0.008), higher C2 slope (17.9° vs. 13.2°, P = 0.014), and greater total disc height (11.8 mm vs. 10.7 mm, P = 0.040). Multivariate analysis identified preoperative OALL at C5/6 (OR = 3.02, 95% CI 1.08-8.49, P = 0.036) and larger C0-2 Cobb angle (OR = 1.10, 95% CI 1.02-1.17, P = 0.009) as independent risk factors, whereas OPLL at C6 was protective (OR = 0.26, 95% CI 0.09-0.77, P = 0.015). The final model yielded an AUC of 0.74 and F1 score of 0.52.

CONCLUSIONS

Approximately one-quarter of patients developed significant IDH loss after posterior cervical surgery for OPLL. Larger cranio-cervical extension (C0-2 Cobb), OALL at C5/6, and absence of OPLL at C6 were associated with greater risk. Preoperative sagittal alignment and ossification patterns may help identify patients at risk for postoperative disc degeneration.