Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/10/2008
Publication Date: 9/18/2008
Citation: Lo, G.H., Mcadams, E., Smith, M., Carr, K.A., Nuite, M., Dawson-Hughes, B., Palermo, N., Mcalindon, T.B. 2008. TIBIAL PLATEAU PROXIMAL AND DISTAL BONE BEHAVE SIMILARLY: BOTH ARE ASSOCIATED WITH FEATURES OF KNEE OSTEOARTHRITIS. In: Osteoarthritis Research Society International, September 18-21, 2008, Rome, Italy. Abstract No. 137.
Technical Abstract: There is a growing imperative to understand how changes in peri-articular bone relate to pathological progression of knee osteoarthritis (KOA). Peri-articular bone density can be measured using dual x-ray absorptiometry (DXA). The medial:lateral tibial BMD ratio (M:L BMD) is associated with MRI and x-ray features of KOA, and abnormal knee alignment (a factor in KOA progression). However, observations suggest that the processes differ between the subchondral bone and deeper trabecular bone. We contrasted the construct validity of M:L BMD ratios derived from different regions of interest in the peri-articular bone. This was a convenience sample of enrollees in a trial of vitamin D for KOA. All participants had PA weight-bearing knee radiographs, knee DXA scans and 1.5 Tesla MRIs of their study knee. We calculated overall M:L BMD using a region of interest (ROI) depth of 2cm. We determined proximal M:L BMD using the proximal 1cm of the aforementioned ROI and distal M:L BMD, measuring the distal 1cm. X-rays were scored for Kellgren/Lawrence grade (0-4) and anatomic alignment (ICC=0.99). To convert the anatomic alignment to mechanical axis (MA), in women 3.5 degrees were subtracted from the anatomic alignment and in men 6.4 degrees. Varus was defined as an MA < 178. Extent of full cartilage thickness loss in the tibiofemoral compartments (TF) was read on MRI using the BLOKS scoring method. We performed logistic regression with case-based tertiles of M:L BMD as predictors and moderate-severe full cartilage thickness loss in the medial TF compartment as the outcome. These tertiles of M:L BMD were also used to predict K/L 3 or 4 as well as mechanical alignment. We repeated the analyses with the proximal M:L BMD and the distal M:L BMD as predictors. We contrasted the strengths of association of the different measures with those features of KOA. Participants (N=99) had a mean age of 63.8 (+/-8.6) and BMI of 30.5 (+/-5.4); 64.7% were female. Proximal M:L BMD most strongly associated with features of KOA (Table). Distal M:L BMD showed similar associations but point estimates were smaller. Conclusion: In symptomatic KOA, increased ipsi-compartmental BMD is most marked in the proximal 1 cm of peri-articular bone but extends further. Tibial plateau proximal and distal bone behave similarly such that both are associated with features of KOA. The 3 measures of M:L BMD provide contrasting information that allow greater insight into the role of bone in KOA. The attributes of these measures should be explored in longitudinal settings.