Objective Preoperative assessment is critical for selecting the appropriate surgical approach for thoracic ossification of the posterior longitudinal ligament (T-OPLL). Computed tomography myelography (CTM) offers superior visualization but carries procedural risks. The objective of this study was to evaluate the clinical impact on surgical decision-making and periprocedural neurological events of preoperative CTM in patients with T-OPLL.

Methods This single-center, retrospective cohort study included 37 patients who underwent surgery for T-OPLL between April 2011 and July 2024. The inclusion criteria required a minimum of 1-year follow-up. All patients had preoperative CTM and MRI scans. The primary outcome was the detection rate of the posterior subarachnoid space (PSAS) at the most stenotic level, compared between CTM and MRI. The secondary outcome was the incidence and nature of neurological deterioration within 48 hours following the CTM procedure. Clinical outcomes were assessed using the Japanese Orthopaedic Association (JOA) score.

Results CTM identified the PSAS in 10 of 37 patients (27.0%), whereas MRI identified it in only 3 patients (8.1%). The detection rate of the PSAS was significantly higher with CTM than with MRI (p = 0.0156). Notably, in 7 patients (18.9%), the PSAS was visible only on CTM, providing crucial information for selecting anterior spinal cord decompression. Transient neurological deterioration occurred in 9 patients (24.3%) following CTM; symptoms included sensory disturbance (n=7), motor weakness (n=1), and bladder/bowel dysfunction (n=1). However, all adverse events were transient and fully reversible. Symptoms resolved spontaneously to the pre-procedural baseline within 48 hours, and no patients suffered permanent neurological deficits. The mean JOA score significantly improved from 4.8 preoperatively to 8.1 at the 1-year follow-up (p < 0.001).

Conclusions In the preoperative evaluation of T-OPLL, CTM demonstrated superior visualization capabilities compared to MRI in detecting the PSAS, providing useful information for surgical method selection. It should be noted that transient neurological deterioration can occur at a certain rate following CTM; however, in this cohort, symptoms recovered to baseline within 48 hours, and no permanent sequelae were observed. Therefore, upon careful evaluation of risks and benefits, CTM can be a useful option for preoperative planning.