The Triangle Model of Congenital Cervical Stenosis.

STUDY DESIGN Retrospective Cross-Sectional Study OBJECTIVE.: Identify the pathoanatomical features of the cervical spine associated with congenital stenosis SUMMARY OF BACKGROUND DATA.: Congenital cervical stenosis (CCS) describes a patient with a decreased spinal canal diameter at multiple levels of the cervical spine in the absence of degenerative changes. Despite recognition of CCS throughout the literature, the anatomical features that lead to this condition have not been established. Knowledge of the pathoanatomy behind CCS may lead to alterations in surgical technique for this patient population that may improve outcomes. METHODS From 1000 cervical MRIs between January 2000 and December 2014, CCS was identified in 68 patients using a strict definition of age less than 50 years with mid-sagittal canal diameters (mid-SCD) (<10  mm) at multiple sub-axial cervical levels (C3-C7). A total of 68 patients met the inclusion criteria for this group. Fourteen controls with normal SCDs (>14  mm) at all cervical levels were used for comparison. Anatomic measurements obtained at each level (C3-C7) included: coronal vertebral body, AP vertebral body, pedicle width, pedicle length, laminar length, AP lateral mass, posterior canal distance, lamina-pedicle angle, and lamina-disc angle (LDA). Statistical significance was defined as P < 0.01. RESULTS CCS patients demonstrated significantly different anatomical measurements when compared with controls. Significantly smaller lateral masses, lamina lengths, lamina-pedicle angles, and larger LDAs were identified at levels C3 to C7 in the CCS group (P < 0.01). These anatomic components form a right triangle that illustrates the cumulative narrowing effect on space for the spinal cord. CONCLUSION The pathoanatomy of CCS is associated with a decrease in the lamina-pedicle angle and an increase in the LDA ultimately leading to a smaller SCD. The global changes in CCS are best illustrated by this triangle model and are driven by the posterior elements of the cervical spine. LEVEL OF EVIDENCE 4.