INTRODUCTION

An association between intervertebral disc degeneration (IDD) and osteoarthritis (OA) of the hip and knee has been found previously. However, studies using MRI-evaluated IDD grades with large sample sizes are lacking. Total hip and knee arthroplasty (THA and TKA) can be considered an indicator of clinically evident end-stage OA.

MATERIALS AND METHODS

The study population consisted of 1,153 postmenopausal Finnish women with clinical back problems, of whom 166 had THA and 295 had TKA during the 26-year follow-up. The study was based on the prospective OSTPRE cohort established in 1989 and Finnish Arthroplasty Register data. The IDD severity was graded from T2-weighted lumbar MRI images using the five-grade Pfirrmann classification. Five intervertebral levels (L1-L2 to L5-S1) were studied (5,765 discs). Cox regression with a time-dependent covariate was used to calculate hazard ratios (HRs) for THA and TKA to account for exposure time for severe degeneration.

RESULTS

A higher hazard for THA was observed in women with severe IDD at the L1-L2 (HR 2.66, 95% CI 1.48-4.80), L2-L3 (HR 1.97, CI 1.15-3.38), L5-S1 (HR 1.69, 95% CI 1.16-2.46) and the L1-S1 (HR 2.19, 95% CI 1.53-3.15) intervertebral levels. Adjustment with potential confounders did not alter the results. Women with severe IDD had an elevated hazard for TKA at the L1-S1 mean degeneration (HR 1.50, CI 1.11-2.02) analysis. However, in the adjusted model, the statistical significance of this association was lost (HR 1.34, 95% CI 0.98-1.84). Higher BMI increased the hazard for both THA and TKA; however, the effect was more substantial for TKA.

CONCLUSIONS

The present study supports the association between lumbar IDD and hip OA. A weak association between lumbar IDD and knee OA was observed. Further research is needed to investigate the causality of the relationship between IDD and OA.