Preoperative Evaluation of Ossified Configuration for Thoracic Ossification of the Ligamentum Flavum to Predict Functional Outcome After Surgery

Introduction: Postoperative neurological deterioration can occur in the treatment of patients with ossification of the ligamentum flavum (OLF). In this study, we investigated factors related to postoperative functional prognosis.

Methods: We retrospectively reviewed patients who underwent posterior surgery for thoracic OLF in our hospital From May 2010 to May 2022. Factors including age, sex, body mass index, diabetes, thoracic Japanese Orthopedic Association (JOA) score, lesion level, and ossified configuration of computed tomography (Unilateral or Bilateral/Bridged in axial view, Beak or Round in sagittal view), presence or absence of coexisting ossification of posterior longitudinal ligament, surgical procedures with or without instrumentation, operating time, blood loss, and incidental durotomy. Recovery rate was calculated from the JOA scores before and after surgery, and those with a recovery of 50% or more were defined as good recovery group, and those with less than 50% as poor recovery group. Factors with p-value ≤ 0.2 in univariate analysis were further investigated using multivariate logistic analysis.

Results: Twenty-seven consecutive cases of thoracic OLF surgery were enrolled. With a median follow-up of 25.0 (11.4–74.3) months, median thoracic JOA score significantly improved from 5.8 to 9.0 (p < 0.001) with an average recovery rate of 53.8%. Univariate analysis showed OLF configuration of unilateral type was associated with good recovery (p=0.02). Multivariate analysis, including other factors whose p-values were 0.2 or lower, confirmed that the unilateral configuration of ossification was an independent favorable factor for good recovery (Odds ratio 14.2, 95% confidence interval 1.6–322.5, p=0.01).

Conclusion : Our result indicated that morphological assessment of configuration of ossified ligament may provide useful information in predicting postoperative outcomes. Careful manipulation of ossified ligament appears important for patients with non-unilateral OLF.