Cervical articular process joint versus ventral cervical stabilization in horses: A biomechanical study

OBJECTIVE: To determine the biomechanical properties and modes of failure of a single level equine cervical spine immobilized with unilateral or bilateral articular process joint (APJ) stabilization, ventral cervical stabilization (VCS) and non-stabilized controls. STUDY DESIGN: Ex vivo experimental study. SAMPLE POPULATION: A total of 24 equine cadaver cervical spines. METHODS: Cervical spinal units (C4-C5) were randomly assigned to four groups (n = 6/group): unilateral APJ stabilization, bilateral APJ stabilization, VCS using pedicle screws and rod constructs, or non-stabilized. Non-destructive testing assessed kinematic range of motion (ROM), neutral zone, and stiffness in flexion-extension, axial rotation, and lateral bending. Specimens underwent four-point bending to failure (0.1 mm/s). Radiographs and visual inspection characterized failure mode. Groups were compared using one-way ANOVA or Kruskal-Wallis tests. Significance was p < .05. RESULTS: Non-destructive testing showed unilateral and bilateral APJ constructs were stiffer in flexion-extension, axial rotation and lateral bending than non-stabilized (p < .05). In destructive testing, bilateral APJ stabilization was 2.5× stiffer than VCS, with similar failure moments. Construct stiffness was higher with bilateral APJ stabilization (27.89 ± 5.11 Nm/°) versus non-stabilized (6.92 ± 3.90 Nm/°, p = .0037), unilateral APJ (14.06 ± 2.94 Nm/°, p < .0001) and VCS (11.28 ± 3.01 Nm/°, p < .0001) groups. Failure typically occurred as cranial articular process fracture in both bilateral and unilateral APJ constructs. CONCLUSION: Bilateral APJ stabilization demonstrated greater stiffness than VCS with comparable failure moments. CLINICAL SIGNIFICANCE: Bilateral APJ stabilization, with its higher stiffness than VCS, may be an alternative strategy to achieve spinal fusion in horses while avoiding a ventral surgical approach. Future investigations and development of this technique in vivo are warranted before implementation in clinical cases.