Development of the Indirect Decompression Success Score for Predicting Outcomes in K-Line-Positive Cervical Ossification of the Posterior Longitudinal Ligament

Abstract

Cervical ossification of the posterior longitudinal ligament (OPLL) is a progressive disorder frequently causing myelopathy. For K-line-positive cases, posterior decompression provides effective indirect decompression, yet outcomes remain variable. Recent studies highlight radiological and clinical predictors of recovery, but no comprehensive integrative scoring framework exists to stratify risk. To identify clinical, radiological, and surgical predictors of outcomes in K-line-positive OPLL patients undergoing posterior laminectomy and to develop a novel prognostic tool, the Indirect Decompression Success Score (IDSS). A retrospective cohort of 182 patients with K-line-positive OPLL who underwent decompressive laminectomy (2017–2023) was analyzed. Clinical factors (age, symptom duration, baseline modified Japanese Orthopedic Association [mJOA], Nurick grade), radiological parameters (OPLL type, thickness, space available for cord [SAC], occupancy ratio [OR], T2 hyperintensity), and surgical data were evaluated. Poor outcome was defined as <50% mJOA recovery or Nurick ≥3 at 12 months. Logistic regression identified significant predictors, and weighted scores were assigned to create the IDSS. Poor outcomes occurred in 23.1% of patients. Independent predictors were as follows: age >60 ( P < 0.01), symptom duration >1 year ( P = 0.029), mJOA ≤8 ( P = 0.031), Nurick ≥3 ( P = 0.026), OPLL thickness >7 mm ( P = 0.018), SAC <6 mm ( P = 0.007), OR >60% ( P = 0.002), and T2 hyperintensity ≥2 ( P < 0.01). The IDSS (range: 0–15) stratified patients into low-, intermediate-, and high-risk groups with recovery rates of 82%, 49%, and 28%, respectively ( P < 0.001). The IDSS is a novel, evidence-based prognostic score that integrates clinical, radiological, and surgical factors to predict neurological recovery in K-line-positive OPLL. It offers a practical tool for surgical decision-making and patient counseling, with external validation warranted.