Relationships between in vivo dynamic knee joint loading, static alignment and tibial subchondral bone...

To study, in end-stage knee osteoarthritis (OA) patients, relationships between indices of in vivo dynamic knee joint loads obtained pre-operatively using gait analysis, static knee alignment, and the subchondral trabecular bone (STB) microarchitecture of their excised tibial plateau quantified with 3D micro-CT.

Twenty-five knee OA patients scheduled for total knee arthroplasty underwent pre-operative gait analysis. Mechanical axis deviation (MAD) was determined radiographically. Following surgery, excised tibial plateaus were micro-CT-scanned and STB microarchitecture analysed in four subregions (anteromedial, posteromedial, anterolateral, posterolateral). Regional differences in STB microarchitecture and relationships between joint loading and microarchitecture were examined.

STB microarchitecture differed among subregions (P < 0.001), anteromedially exhibiting highest bone volume fraction (BV/TV) and lowest structure model index (SMI). Anteromedial BV/TV and SMI correlated strongest with the peak external rotation moment (ERM; r = -0.74, r = 0.67, P < 0.01), despite ERM being the lowest (by factor of 10) of the moments considered, with majority of ERM measures below accuracy thresholds; medial-to-lateral BV/TV ratios correlated with ERM, MAD, knee adduction moment (KAM) and internal rotation moment (|r|-range: 0.54-0.74). When controlling for walking speed, KAM and MAD, the ERM explained additional 11-30% of the variations in anteromedial BV/TV and medial-to-lateral BV/TV ratio (R² = 0.59, R² = 0.69, P < 0.01).

This preliminary study suggests significant associations between tibial plateau STB microarchitecture and knee joint loading indices in end-stage knee OA patients. Particularly, anteromedial BV/TV correlates strongest with ERM, whereas medial-to-lateral BV/TV ratio correlates strongest with indicators of medial-to-lateral joint loading (MAD, KAM) and rotational moments. However, associations with ERM should be interpreted with caution.