Variation of three-dimensional structure of subchondral bone in early stage osteoarthritis and interventive effect of diphosphonate / 中华创伤杂志

ABSTRACT

Objective To observe the three-dimensional structure changes of subchondral bone in early stage knee joint instability and the effect of diphosphonate intervention so as to test the role of early three-dimensional structure changes of subchondral bone in pathogenesis of osteoarthritis (OA).Methods Sixty healthy male New Zealand white rabbits were assigned to model group (n =24),diphosphonate group (n=24) and control group (n =12) according to random number table.Rabbit right knee destabilization (anterior cruciate ligament transection) is used to induce OA.Rabbits in diphosphonate group received subcutaneous injection of 0.01 mg/kg diphosphonate (risedronate) per day.Instead,isotonic saline solution of the same volume was subcutaneously given to rabbits in model and control groups.One third of the animals in each group were killed at week 4,8 and 12 respectively.Surgical knee joint with preservation of each 2 cm bone above and below joint surface was dissected to perform Micro-CT.Bone volume fraction (BVF),trabecular thickness (Tb.Th),trabecular spacing (Tb.Sp),trabecular number (Tb.N),volumetric bone mineral density (vBMD) and tissue BMD (tBMD) were measured and analyzed statistically.Results At week 4 following operation,BVF,Tb.N and Tb.Th were lowered significantly in model group as compared to control group (P ＜0.01) ;BVF was lower in model group than in diphosphonate group (P ＜ 0.05) and lower in diphosphonate group than in control group (P ＜ 0.05) ; Tb.Sp was increased in model group as compared to diphosphonate group and control group (P ＜0.01) and had obvious increase in diphosphonate group as compared to control group (P ＜0.01) ; vBMD was significantly lower in model group than in diphosphonate group and control group (P ＜ 0.05),but there was no statistical difference between diphosphonate group and control group.At week 12 following operation,model group presented higher BVF,Tb.Th and Tb.N (P ＜0.05),significantly lower Tb.Sp (P ＜ 0.05) and significantly higher vBMD (P ＜ 0.01) as compared to diphosphonate group and control group.Conclusions In knee joint instability,variations of subchondral bone are mainly characterized by osteoclasia in the early stage,followed by osteogenesis in later stage.Diphosphonate may improve the bone architecture of subcondral bone via inhibition of bone resorption.