Effect of Facet Tropism on Postoperative Cervical Range of Motion After Single-Level Cervical Disc Arthroplasty

Does Baseline Facet Arthropathy Influence Early Clinical and Radiographic Outcomes After Cervical Disc Replacement?

BACKGROUND AND OBJECTIVES

Severe facet arthropathy is generally a contraindication to undergoing cervical disc replacement (CDR) due to associated instability and potentially limited improvement in neck pain caused by arthropathy. This study evaluates the influence of facet arthropathy on radiographic/early clinical outcomes after CDR.

METHODS

One/two-level CDR patients from a single surgeon's prospectively maintained database created 2 cohorts based on facet arthropathy: grade 0-1 or 2-3 (milder/moderate arthropathy). Patient-reported outcome measures for neck disability, neck/arm pain, depressive burden, mental/physical health/function were obtained preoperatively and through final follow-up (average follow-up: 8.5 ± 6.5 months). Preoperative/postoperative radiographs measured segmental lordosis and C2-C7/segmental range of motion (ROM) and determined facet grade for each operative level. Demographic differences, perioperative variables, baseline patient-reported outcomes, and intercohort differences/changes for postoperative patient-reported/radiographic outcomes were determined.

RESULTS

Of 161 patients, 100 were in the milder arthropathy group. There were no differences in baseline patient-reported outcomes. Patients with moderate arthropathy reported superior 6-week 12-Item Veterans Rand Mental/Physical Composite Scores (P ≤ .047, all). By final follow-up, moderate patients reported better 12-Item Veterans Rand Mental/Physical Composite Scores/Patient-Reported Outcome Measurement Information System-Physical Function/Patient-Health Questionnaire-9 (P ≤ .049, all). Cohorts reported similar improvements in all patient-reported outcomes by 6 weeks/final follow-up. Those with more severe facet arthropathy had significantly shorter preoperative disc heights (P < .001). Accounting for baseline disc height differences, by final follow-up, moderate patients had lower segmental ROM (P = .036). There were no significant differences in radiographic measurement changes (P ≥ .264, all).

CONCLUSION

Postoperatively, patients with moderate facet arthropathy reported lower depressive burden, better mental health/physical function, and lower segmental ROM. However, this did not translate to inferior short-term clinical outcomes. Further study should be conducted on the relationship between clinical/radiographic outcomes in CDR patients with facet arthropathy.

Tropism of Sub-Axial Cervical Facet Joints Is Not Related to Segmental Movement during Active Movement or Therapist-Perceived Symptomatic Locations

Tropism, or asymmetry, of facet joints in the cervical spine has been found to be related to degenerative changes of the joints and discs. Clinicians often assume that differences in segmental mobility are related to tropism. The aims of this study were to determine the relationship between asymmetry of facet joints in the sub-axial cervical spine and (1) segmental mobility and (2) spinal levels perceived by therapists to have limited mobility. Eighteen participants with idiopathic neck pain had MRIs of their cervical spine in neutral and at the end of active rotation. Angular movement and translational movement of each motion segment was calculated from 3D segmentations of the vertebrae. A plane was fitted to the facet on each side. Tropism was considered to be the difference in the orientation of the facet planes and ranged from 1 to 30° with a median of 7.7°. No relationships were found between the extent of tropism and either segmental movement or locations deemed to be symptomatic. Tropism in the sub-axial cervical spine does not appear to be related to segmental mobility in rotation or to levels deemed to be symptomatic.