Medial Location Shifting of the Gutter on the Open Side in Expansive Open-Door Laminoplasty Might Minimize the Incidence of C5 Palsy

Study Design Retrospective cohort study. Objectives To investigate whether shifting the medial location of the gutter on the open side during posterior cervical expansive open-door laminoplasty affects postoperative C5 palsy (C5P) incidence. Methods Patients were divided into two groups based on the opening-side location: the conventional laminar transitional zone (conventional group, dural sac decompression) and a position 1 mm medial to the laminar transitional zone (modified group, spinal cord decompression). The incidence of C5P, radiological parameters, and neurological outcomes were compared. Results A total of 258 consecutive patients with degenerative cervical myelopathy (DCM) who underwent laminoplasty in the spine surgery unit of our institution between May 2024 and October 2024 were included. C5P occurred in 5/128 (3.9%) in the conventional group and 0/130 in the modified group ( P = 0.029). At the final follow-up, the mean JOA improvement rates were 55.8% ± 18.9% and 54.6% ± 16.9% in the conventional and modified groups, respectively ( P = 0.599). The modified group showed a significantly smaller width between the bilateral gutters (median, 18.7 vs 20.3 mm; P < 0.001) and less posterior spinal cord shift (median, 2.0 vs 3.0 mm; P < 0.001) than the conventional group, with a significant correlation between the two parameters. Conclusions Positioning the gutter on the open side 1 mm medial to the junction of the laminae and facet joints during cervical expansive open-door laminoplasty may reduce the incidence of C5P without affecting neurological recovery, potentially by limiting posterior spinal cord shift.