Estimation of the chondrocyte number in the articular cartilage by combined distraction osteosynthesis of the tibia (Ilizarov apparatus and plating)

Introduction The number of chondrocytes in the articular cartilage of the femoral condyles and talus junction surface in the conditions of distraction osteosynthesis of the tibia with the Ilizarov apparatus combined with plating was estimated. Material and methods Seven dogs underwent tibial lengthening at a daily rate of 1 mm for 4 steps and to 14-16 % of the initial length of the segment with the use of the Ilizarov apparatus and plating. Stages of the study were days 30 and 90 in the fixation phase when only plating was left. Histomorphometry of semi-thin sections of the articular cartilage was carried out with the help of an Opton photomicroscope (Germany), DiaMorf software complex (Russia) and VideoTest-Master morphology program. The proportion of chondrocytes (Nch, %), the proportion of empty lacunae (NNem.lac, %), and isogenic groups (NNis.gr, %) were determined in the total sample volume of 200 lacunae. A control group was articular cartilage of five intact dogs. Results The articular cartilage of both articular surfaces retained the zonal structure. Disorder in the homogeneity of the superficial part of the surface zone and destruction of a part of chondrocytes were noted. In the articular cartilage of the femoral condyles, the Nch value was lower than in the control animals by 5.74 %. NNem.lac was increased 2.3 times while NNis.gr values decreased to 2.06 % in the femoral condyle articular cartilage after 30 days of fixation period with the plate. After 90 days of fixation, the Nch values were lower with respect to the controls by 3.73 %. Low values of NNis.gr (4.3 %) and high values of NNem.lac (27.54 %) were maintained. In the articular cartilage of the talus, Nch was lower than in the control group by 1.98 %; NNem.lac increased 1.5 times and NNis.gr decreased to 4.7 % relative to controls after 30 days of fixation. After 90 days, the value of NNem.lac remained at the same level as in the previous experiment stage. The values of NNis.gr were comparable with the control group. Conclusion The technique of distraction osteosynthesis of the tibia in combination with plating is of low traumatic effect on the adjacent joints. A comparative analysis of quantitative parameters of the articular cartilage revealed that the most vulnerable site was the articular cartilage of the femoral condyles.