The reliability of computed tomography and magnetic resonance imaging grading of lumbar facet arthropathy in total disc replacement patients.

STUDY DESIGN: Prospective inter-rater and intrarater reliability analysis.

OBJECTIVE: To compare the inter-rater and intrarater reliability of magnetic resonance imaging (MRI) and computed tomography (CT) for grading of facet arthropathy as well as determining whether there is a contraindication to total disc replacement (TDR).

SUMMARY OF BACKGROUND DATA: Several classifications attempted to evaluate lumbar facet joints and their degree of arthropathy. The Fujiwara-MRI and Pathrea-CT classifications remain the most commonly used.

METHODS: A total of 10 fellowship-trained orthopedic spine surgeons and 3 orthopedic spine fellows evaluated 50 levels from L3-L4 through L5-S1 on parallel axial MRI (T1 and T2) and CT images. The degree of osteoarthritis was graded on a 4-point scale (Fujiwara-MRI and Pathrea-CT). Surgeons evaluated whether the degree of facet disease represented a contraindication to TDR. Grading was performed during 2 sessions. Weighted kappa statistics were used to describe inter- and intraobserver agreement.

RESULTS: The inter-rater reliability for MRI was 0.21 and 0.07 (fair to slight) among attendings and fellows, respectively. inter-rater reliability for CT was 0.33 and 0.27 (fair), respectively. The mean intrarater reliability for MRI was fair, 0.36 (attendings) and 0.26 (fellows). The mean intrarater reliability for CT was moderate, 0.52 (attendings) and 0.51 (fellows). For possible TDR contraindication, the inter-rater reliability for MRI was 0.22 and 0.01 (fair to slight) among attendings and fellows, respectively. Inter-rater reliability for CT was 0.33 and 0.45 (fair), respectively. The mean intrarater reliability for MRI was fair, 0.36 (attendings) and 0.26 (fellows). The mean intrarater reliability for CT was moderate, 0.52 (attendings) and 0.51 (fellows).

CONCLUSION: The current grading system for facet arthropathy has only fair agreement. CT is slightly more reliable for grading. Intrarater reliability was only fair for MRI and moderate for CT. Only limited agreement existed between surgeons as to the extent of facet disease that would pose as a contraindication for TDR.