Lower extremity deep sensory disturbance as a risk factor for postlaminoplasty kyphosis in patients with cervical ossification of the posterior longitudinal ligament.

BACKGROUND CONTEXT: Cervical laminoplasty (LMP) is a standard surgical procedure for treating ossification of the posterior longitudinal ligament (OPLL). However, postlaminoplasty kyphosis (PLK) remains an unresolved problem. Although a restricted cervical extension range of motions (ROM) and sagittal imbalance have been reported as risk factors for PLK, these factors do not fully explain its occurrence. Deep sensory disturbance (DSD) of the lower extremities has been reported as a cause of habitual neck flexion while walking or ascending stairs, as patients visually compensate for impaired proprioception; however, its association with PLK has not been clearly established.

PURPOSE: To investigate whether lower extremity DSD is associated with an increased risk of PLK in patients with cervical OPLL.

STUDY DESIGN/

SETTING

Retrospective multicenter observational study.

PATIENT SAMPLE: A total of 190 patients with radiographically and clinically diagnosed cervical OPLL who underwent cervical LMP involving more than 3 levels between 2008 and 2023 at 2 university hospitals and 5 general hospitals in Japan.

OUTCOME MEASURES: Postoperative kyphosis progression was defined as a decrease of ≥9° in the C2-7 lordotic angle on lateral radiographs. Risk factors were assessed using demographic, clinical, and radiographic variables, including cervical ROM, sagittal vertical axis (SVA), and the presence of DSD.

METHODS

Radiographic measurements and clinical data were retrospectively reviewed. Patients were classified into PLK and non-PLK groups based on changes in the C2-7 angle. Multivariate logistic regression analysis was performed to identify independent risk factors for PLK.

RESULTS

Of the 190 patients, 50 (26.3%) exhibited kyphosis progression. DSD was significantly more prevalent in the PLK group. Multivariate analysis identified DSD, decreased preoperative cervical extension ROM, and increased preoperative C2-7 SVA as independent risk factors for PLK. Patients with DSD demonstrated greater preoperative C2-7 SVA and reduced cervical extension ROM.

CONCLUSIONS

DSD in the lower extremities is a significant independent risk factor for PLK in patients with cervical OPLL, likely due to habitual downward gaze for visual compensation during walking. These findings underscore the importance of considering DSD in postoperative rehabilitation strategies aimed at preventing PLK.