SUMMARY: This study aims to observe the 3-D structural changes in subchondral bone and the effects of bisphosphonate intervention in the early unsteady stage of the knee joint. Sixty healthy male New Zealand white rabbits were divided into the model group (n= 24), the bisphosphonate (Bis) group (n= 24), and the control group (n= 12). The rabbits’ right knees were used to evaluate the structural changes. The Bis group received subcutaneous injections of bisphosphonate, while the model and control groups received subcutaneous injections of isotonic saline solution. After surgical preparation, the knee joint was dissected for Micro-CT examination, and the Micro-CT results were compared using ANOVA. In the fourth postoperative week, the bone volume fraction (BVF), trabecular number (Tb.N), and trabecular thickness (Tb.Th) of the model group were significantly lower than those of the control group (P<0.01). There was no significant difference between the Bis and control groups. In the twelfth postoperative week, BVF, Tb.Th, and Tb.N of the model group were significantly higher than those of the control and Bis groups (P <0.05). Similarly, bone mineral density was higher in the model group (P <0.01), while the trabecular spacing was significantly lower (P <0.05). In the early unsteady stage of the knee joint, the subchondral bone had markedly decreased, while obvious bone formation was visible in the late stage. Bisphosphonates could protect the subchondral bone structure by inhibiting bone absorption.
KEY WORDS: Osteoarthritis; Subchondral bone; 3D structure; Micro-CT.