# Laminoplasty plate design is an independent risk factor for facet joint violation

## TL;DR

This study finds that the design of laminoplasty plates affects the risk of facet joint violation and surgical outcomes in cervical spine surgery.

## Contribution

The study identifies vertical plate orientation as an independent risk factor for facet joint violation in cervical laminoplasty.

## Key findings

- Vertical plate orientation was associated with a 60% incidence of facet joint violation compared to 32.3% for horizontal orientation.
- Vertical plates caused greater loss of cervical lordosis and increased operative time by 29.5 minutes.
- Facet joint violation did not significantly affect postoperative pain scores.

## Abstract

Cervical laminoplasty is a motion-preserving surgical technique for cervical myelopathy. Laminoplasty plates stabilize the spinal canal, often using different plate designs that define screw trajectory. Although it is recognized that screws penetrating facet joints can lead to worse postoperative pain scores and outcomes, limited research has examined the outcomes associated with the different orientations of laminoplasty plates, which may contribute to screw-related complications such as facet joint violation (FJV). This study evaluates the impact of laminoplasty plate design and screw orientation on FJV incidence, operative time, and clinical outcomes.

This is a retrospective review of 105 patients receiving unilateral open-door cervical laminoplasty for myelopathy or myeloradiculopathy. Data was collected from 2017 to 2023 at a single institution and procedures were performed by one of six fellowship-trained spine surgeons. Patients with ≥1-year radiographic and clinical follow-up were included. Radiographic parameters (C2–7 Cobb angle, T1 slope, Torg–Pavlov ratio, and C2–7 SVA) were assessed preoperatively, postoperatively, and at 1 year. Groups were separated by the plate design, with one group having horizontal oriented lateral screws and the other having vertical. FJV was defined as screw penetration ≥2 mm beyond the facet cortex.

A total of 105 patients were included (65 horizontal, 40 vertical). Groups were similar in age, BMI, sex, smoking status, diabetes, and CCI (all p > 0.05). Preoperative cervical sagittal parameters were also comparable. Postoperatively, the vertical group had significantly greater loss of C2–7 lordosis (3.22° ± 10.37) compared to the horizontal group (−1.39° ± 11.76; p = 0.03), with this difference persisting at final follow-up (1.38° ± 12.27 vs. −5.21° ± 12.07; p = 0.01). Facet joint violation occurred more frequently in the vertical group (60.0 % vs. 32.3), with multivariate analysis identifying vertical plate orientation as an independent risk factor (OR 11.7, p = 0.01). Vertical plate orientation was also independently associated with increased operative time (+29.5 min, p = 0.02).

Vertical laminoplasty plate orientation was associated with increased FJV risk and longer operative time, as well as greater loss of lordosis within a year postoperatively, though it did not affect pain scores. Further research is needed to evaluate the long-term implications of FJV on patient outcomes.