The Total Disc Replacement Osteolysis Grading Scale - a simple, reliable and quantifiable tool for assessing, managing and reporting osteolysis after cervical total disc replacement.

PURPOSE: Cervical Total Disc Replacement (CTDR) related periprosthetic osteolysis is inconsistently reported. The purpose of this study is to assess the previously published TDR Osteolysis Grading Scale, a quantitative classification system of CTDR-related osteolysis, and to assess its reliability and utility using Computer Tomography (CT) and X-ray imaging.

METHODS

Participants were assigned to Groups A (CT, 20 participants, 27 implants) and B (X-ray, 20 participants, 26 implants). Four blinded raters independently measured osteolytic cysts and both vertebral endplates, calculated the percentage of osteolysis and assigned osteolysis grades: Grade 0, no osteolysis; Grade 1, < 50% of 1 endplate; Grade 2, < 50% of both endplates; Grade 3, ≥ 50% of 1 endplate; Grade 4, ≥ 50% of both endplates. Inter-rater reliability and sensitivity were assessed using intraclass correlation coefficients (ICC), Fleiss' and Cohen's Kappa statistics and sensitivity testing.

RESULTS

Group A had good reliability for osteolytic cyst measurements (ICC = 0.78-0.79), poor reliability for endplate measurements (ICC = 0.41-0.45) and moderate reliability for osteolysis grades (κ-coefficient = 0.42). Group B had moderate reliability for osteolytic cyst (ICC = 0.55-0.57) and endplate measurements (ICC = 0.55-0.64) and fair reliability for osteolysis grades (κ-coefficient = 0.30). Reliability between reference grades and assigned grades was moderate for Group A (κ-coefficient = 0.46-0.60) and fair for Group B (κ-coefficient = 0.08-0.35). Sensitivity was greater for high grade osteolysis (grade 3 and 4) in Group A (0.80-1) than Group B (0.17-0.50).

CONCLUSION

The TDR Osteolysis Grading Scale demonstrated good reliability and sensitivity amongst raters with CT. Implementing this tool may aid in standardising osteolysis reporting, monitoring osteolysis progression and clinical decision-making.