Location-dependence of subchondral trabecular structure and cartilage and subchondral bone plate thickness across the tibia in human non osteoarthritic knee: A micro-CT study

Purpose: To determine whether in non osteoarthritic (OA) knees cartilage and subchondral plate volume and subchondral trabecular bone structure vary with location in the tibia plateau. Methods: Bone cores extracted in three different locations from 28 cadaveric knees were scanned with micro-CT. Cadaveric unpaired knees (left) obtained from a population of 17 (60.7%) women and 11 (38.3%) men who willed their body to science were included in the study. The mean age was 83 years ± 10 (range 58-99, median 82). For each specimen the Kellgren-Lawrence score determined from post mortem radiographs was lower than two. After dissection, 3 vertical cores (7 mm in diameter, 10 mm in length) were extracted in the posterior (S1), inner (S2) and lateral (S3) regions of the medial tibial plateau. In all specimens S3 was fully, S1 was partially and S2 was not covered by the meniscus. Each core was imaged twice with micro-CT (SkyScan 1172®, Brucker, Belgium) pixel size 10.23 μm. In the first scan, the extracted cores were imaged to measure cartilage volume (CartVol, mm3) and cartilage thickness (CartTh, mm) by the sphere method. The second scan was performed after defatting using supercritical CO2 to measure: subchondral bone plate volume (SBP_Vol, mm3) and porosity (SBP_Porosity, %) of the cortical subchondral bone as well as subchondral trabecular architecture. In the 6.8 mm beneath the subchondral bone plate: Bone Volume/Total Volume (BV/TV, %), trabecular number (Tb.N, 1/mm), trabecular thickness (Tb.Th, mm), trabecular separation (Tb.Sp, mm), and the degree of anisotropy (DA,unitless) were measured. One-way analysis of variance (ANOVA, Kruskal-Wallis), followed by post-hoc analysis for multiple range test (Tukey-Kramer) were used to investigate group differences in cartilage, subchondral bone plate and trabecular bone structure. Pearson correlation coefficients (r) were used to investigate the relationship between cartilage, SBP and subchondral trabecular bone. Results: Table 1 shows mean ± SD values for the analyzed parameters and also indicates whether there were significant differences among the three locations. There is no correlation between trabecular bone parameters with subchondral plate and cartilage. There is significant correlation coefficients between the SBP_Vol and the CartTh and CartVol r= 0.60 (p<0.001) and 0.65 (p<0.0003), respectively in location (S1). Conclusions: In non OA knees, the relationships between CartVol, SBP_Vol and SBP_Porosity with subchondral trabecular bone volume are location dependent. In an inner position (S2), which is never covered by the meniscus, CartVol, CartTh, SBP_Vol and the trabecular bone parameters BV/TV and Tb.Th were higher and DA was lower compared to the lateral (S3) locations, which are usually covered by the meniscus. Parameters from the (S1) location partially covered by the meniscus provide intermediate results between (S2) not covered with (S3) always covered except for Tb.N and Tb.Sp. We conclude that the location in the tibial medial plateau and the presence of the meniscus play an important role on the surrounding structures such as cartilage, subchondral plate and trabecular subchondral bone.Table 1S1 groupS2 groupS3 groupANOVAPost-HocBV/TV, %20.3±7.824.4±9.619.0±7.30.032/3Tb.Th, mm0.156±0.030.171±0.040.143±0.020.012/3Tb.Sp. mm0.602±0.080.614=0.150.606±0.1ns-Tb.N, mm1.25±0.251.39±0.321.29±0.29ns-DA1.76±0.341.65±0.252.15±0.420.000023/2-1Cart Th, mm1.85.0.442.33±0.411.74±0.29<10-43/2/1Cart Vol, mm381.3±25.6104.7±25.366.7±11.9<10-43/2/1SBP_Vol, mm314.4±6.517.8±5.810.4±3.1<10-42/3-1SBP_Porosit, %28.1±20.512.7±6.017.6±7.4<10-42/3-1 Open table in a new tab