Abstract
Study Design
Retrospective cohort study.
Objectives
Thoracic ossification of the posterior longitudinal ligament (OPLL) is traditionally considered progressive, raising concern that the ossified mass left after posterior decompression and instrumented fusion (PDF) may enlarge. We characterized long-term CT-based changes in focal OPLL thickness after PDF and assessed whether the residual mass continued to enlarge.
Methods
We reviewed all consecutive adult patients who underwent PDF for thoracic OPLL (2009–2023) with ≥2 years of follow-up. Maximum OPLL thickness was measured on axial CT and tracked longitudinally; a predefined 2-mm threshold, prespecified as the minimal clinically important difference, classified change. Thoracic kyphosis (TK) and modified Japanese Orthopaedic Association (mJOA) scores were also assessed.
Results
Twenty-six patients (mean age 49.5 ± 12.4 years; 15 men) were followed 5.4 ± 2.7 years (range 2–11). Mean axial OPLL thickness changed from 7.02 ± 1.58 to 6.90 ± 2.01 mm (Δ −0.12 ± 1.03 mm). By the 2-mm threshold, 92.3% were stable, 3.8% decreased, and 3.8% increased; directional decreases occurred in 69.2% and increased with longer follow-up (37.5%, 77.8%, 88.9%; p = 0.023). TK increased (+6.2°, p
Conclusions
Focal thoracic OPLL thickness remained predominantly stable after PDF, with threshold-level progression infrequent and neurological improvement maintained. Focal radiographic stability, rather than continued enlargement of the residual mass, was the predominant postoperative course after PDF.