The relationship between spinal and peripheral osteoarthritis and bone density measurements.

OBJECTIVE

To determine the influence of osteoarthritis (OA) on bone density measurements and whether OA at one site is associated with OA at other sites.

METHODS

Nonrandomized, cross sectional observational study; secondary analysis of a general population database. Sixty-four subjects derived from a longitudinal study of long distance runners and community controls had a complete peripheral radiographic evaluation for osteoarthritic changes in hands, knees, and lumbar spine. Forty-four of these were studied in 1984 with quantitative computed tomography (QCT) of L1, and 54 were studied in 1988 with 153-Gd dual photon absorptiometry (DPA) in the spine and total body. Thirty-four subjects had all measurements done.

RESULTS

Total body and lumbar spine DPA were positively correlated with radiological scores of OA in the spine and knees, with coefficients ranging between 0.467 to 0.530 (p < 0.001 in all cases). This correlation was principally associated with spinal spurs and knee sclerosis. Results of stepwise multiple linear regression modeling for QCT included age, spine sclerosis, knee sclerosis and knee spurs as the main predictors of bone mineral density (BMD). For DPA measurements, spine spur score was a useful regressor for all the models. Altogether, the percentage of variance accounted for by individual radiological OA variables was 27.4% for lumbar QCT, 27.3% for lumbar BMD, 7.3% for total spine BMD, and 45.2% for total body BMD. OA scores at different sites were not correlated, although repeated assessment at the same site showed very close correlation.

CONCLUSIONS

All methods used to determine BMD showed a highly significant positive correlation between lumbar and knee radiological OA and bone mineral content both in the spine and the total body. Thus, our results support the hypothesis that OA is negatively correlated with osteopenia. OA, as seen in this population, was not a generalized condition, but rather, was site specific.