Determinants of anatomical decompression in symptomatic degenerative cervical myelopathy: A quantitative MRI analysis...

While quantitative MRI (qMRI) metrics effectively describe preoperative compression in degenerative cervical myelopathy (DCM), their use in identifying determinants of postoperative anatomical decompression remains limited, particularly in patients with suboptimal clinical trajectories.

In this retrospective cohort study, we analyzed 40 patients (78 segments) who underwent postoperative MRI due to suboptimal clinical recovery or late neurological worsening. Using Generalized Estimating Equations (GEE) to account for clustered data, we identified determinants for changes in maximum canal compromise (ΔMCC), transverse area of the cervical canal (ΔTACC), maximum spinal cord compression (ΔMSCC), transverse area of the spinal cord (ΔTASC), and compression ratio (ΔCR). Models controlled for surgical approach, demographics, and preoperative severity.

Surgical intervention significantly improved all qMRI parameters (p < 0.001). The posterior approach achieved markedly greater canal expansion (ΔTACC B = -34.86, p < 0.001) and better restoration of cord morphology (ΔCR B = -6.33, p = 0.020). However, actual spinal cord re-expansion (ΔMSCC, ΔTASC) was not significantly determined by the surgical approach (p > 0.10) but was primarily constrained by preoperative severity (B = -0.73 and B = -0.81, respectively; both p < 0.001). Notably, isolated anterior compression significantly limited axial cord area re-expansion (B = -15.39, p = 0.018). Patients with ASA III showed significantly less sagittal cord expansion compared to those with ASA II (p = 0.029), while advanced age showed a strong trend toward reduced canal expansion (p = 0.079). Longer intervals to postoperative MRI were associated with greater measured decompression (p < 0.05), suggesting morphometric stabilization after the acute postoperative phase.

In patients with suboptimal clinical recovery, a critical dissociation exists: spinal canal expansion is primarily determined by the surgical approach, whereas spinal cord re-expansion is constrained by preoperative severity and the specific compression pattern. These findings define the anatomical boundaries of surgical decompression and suggest that personalized planning must account for the "biological ceiling" of the cord. Quantitative MRI serves as an essential tool for establishing anatomical benchmarks in the postoperative assessment of DCM.