REGIONAL DEPTH-SPECIFIC SUBCHONDRAL BONE DENSITY IN OA AND NORMAL DISTAL FEMORA: PRECISION AND PRELIMINARY COMPARISONS

INTRODUCTION

The exact role of altered subchondral bone in OA pathogenesis and pain is unclear. Clinical quantitative CT (QCT) combined with depth-specific image processing has been previously used to study subchondral bone mineral density (BMD) at the proximal tibia and patella. Limited depth-specific QCT research has been completed at the OA distal femur.

OBJECTIVES

To 1) assess the short-term precision of automated, regional, depth-specific subchondral BMD measures at the distal femur in individuals with and without OA; and 2) determine whether regional and focal BMD metrics were able to discriminate differences in subchondral bone density patterns between normal and OA distal femora.

METHODS

Fourteen participants (3M:11F; mean age: 49.9 (SD: 11.9) years) were recruited and classified as normal (n=7) or OA (n=7). Each participant was scanned three times over two days using clinical QCT. Two BMD assessments were evaluated at the distal femur: mean regional density and peak focal density. BMD measures were assessed across three depths (0-2.5, 2.5-5, 5-7.5 mm) and six sub-regions of the distal femur (medial/lateral, anterior/central/posterior), as per the MOAKS approach (Fig.1). We assessed precision using root mean square coefficients of variation (CV%_RMS). To explore potential differences between OA and normal distal femora, we performed parametric t-tests and non-parametric Mann-Whitney statistical analyses and also determined Cohen’s d effect sizes, with an absolute d > 0.8 considered clinically significant.

RESULTS

CV%_RMS ranged from 1.6% to 3.6% (average: 2.2%) for measures of regional BMD while CV%_RMS ranged from 1.6% to 6.9% (average: 2.7%) for measures of focal BMD. Statistical comparisons indicated lower BMD in OA distal femoral in the medial-anterior region at depths of 2.5-5 mm (regional: -17%; focal: -19%) and 5-7.5 mm (regional: -21%; focal: -25%) (Fig. 2). All other BMD measures were similar between normal and OA distal femora (p > 0.05). Cohen's d effect sizes ranged from -1.7 to 0.76.

CONCLUSION

This automated technique offers precise measures of subchondral BMD at the distal femur. This approach has potential to quantify and distinguish OA-related alterations in subchondral BMD at the distal femur.