There is currently no established index for evaluating the adequacy of the surgical area during laminoplasty. This study aims to propose a novel concept of the drifting angle of the spinal cord (DA-SC) at the cephalic and caudal junction of surgical and nonsurgical laminae during laminoplasty, and to assess its clinical relevance.

A retrospective review of clinical and radiological data was conducted on 296 patients who underwent laminoplasty. Patients were classified into four groups based on preoperative DA-SC of cephalic and caudal junction of surgical and nonsurgical laminae: Group DA-SC SS (both cephalic and caudal DA-SC were small); DA-SC LL (both cephalic and caudal DA-SC were large); DA-SC LS (cephalic DA-SC was large whereas caudal DA-SC was small); and DA-SC SL (cephalic DA-SC was small whereas caudal DA-SC was large). Clinical outcomes were recorded and analyzed before surgery, 2 months postoperatively, and at the last follow-up.

Both cephalic and caudal DA-SC increased significantly following laminoplasty, patients in group DA-SC SS demonstrated superior clinical recovery rate than that of other three groups, indicating that small DA-SC is positively related with great clinical outcomes.

The concept of DA-SC is valuable in assisting making decisions regarding the extent of laminoplasty in patients with cervical ossification of the posterior longitudinal ligament. Reducing the DA-SC by extending the surgical area is necessary when DA-SC is large.

Drifting angle

Laminoplasty

Ossification of the posterior longitudinal ligament

Spinal cord

Cervical ossification of the posterior longitudinal ligament

Both cephalic and caudal DA-SC were large

Cephalic DA-SC was large whereas caudal DA-SC was small

Cephalic DA-SC was small whereas caudal DA-SC was large

Both cephalic and caudal DA-SC were small

Drifting angle of the spinal cord

Japanese Orthopaedic Association

Magnetic resonance imaging

Ossification of the posterior longitudinal ligament

Posterior compression score

© 2025 The Author(s). Published by Elsevier Inc.