Influence of Gradual Elongation to the Patella Tendon Insertion in Rabbits

Abstract

The purpose of this study was to examine the histological changes at the patella tendon (PT) insertion site under gradual elongation in rabbits. Gradual elongation of the PT was performed using external fixation for 4 weeks, with a lengthening speed of 0.5 mm/day (elongation group; n = 24). Rabbits in the sham group underwent the same surgical procedure without gradual elongation (sham group; n = 24). Eight animals were sacrificed 1, 2 and 4 weeks after surgery in each group, respectively. Average thicknesses of stained glycosaminoglycan (GAGs) areas by Safranin-O staining in the total cartilage layer and the uncalcified fibrocartilage layer in the elongation group were significantly higher than that in the sham group at 4 weeks (p < 0.05) and that in the intact PT group (n = 6, p < 0.05). In the elongation group, the peak in the average thicknesses of the stained GAGs areas in the total cartilage layer and the uncalcified fibrocartilage layer were observed at 4 weeks. Gradual elongation of PT insertion significantly affected the increase in the average thicknesses of the stained GAGs areas in the cartilage layer especially in the uncalcified fibrocartilage layer at 4 weeks in rabbits. Clinically, insertions of tendon and ligament can extend during gradual elongation using external fixation more than 4 weeks after the operation.

Extension of knee immobilization delays recovery of histological damages in the anterior cruciate ligament insertion and articular cartilage in rabbits

“…The chondrocyte apoptosis rate and chondrocyte proliferation rate in the ACL insertion and articular cartilage recovered to the same level as the control group after 8 weeks of remobilization in rabbits that had undergone 2 weeks of immobilization. A previous study reported that the apoptosis of chondrocytes caused by unloading was decreased by reloading in rat bone 18 ) . Furthermore, administration of a drug (salubrinal) reportedly increased the chondrocyte proliferation and reduced the chondrocyte apoptosis under various compressive stresses on the temporomandibular joint in rats 19 ) .…”

Development of fibrocartilage layers in the anterior cruciate ligament insertion in rabbits

“…This laboratory-based animal study used a judgement sampling technique. Forty-eight male Japanese white rabbits were used because of their history of use for histomorphometric analyses of the ACL insertion and to eliminate the influence of female hormones on the ACL [8–11, 15]. Because the skeletal growth of rabbits is complete at 6 months [16], we set the evaluation period at 24 weeks of age.…”

“…Because this study was an evaluation of the development of fibrocartilage layers in ACL tibial insertions, it could not be considered an in vitro experiment. The animal species to be studied was determined based on previous reports [8–11]. Moreover, it is considered difficult to prepare tissue specimens using animals smaller than rabbits.…”

“…The specimens were sliced at 5-μm thickness in the center of the ACL tibial insertion site. The slices were stained with hematoxylin-eosin, and safranin O to assess the histomorphology and GAG contents [8–11]. We also used proliferating cell nuclear antigen (PCNA) staining to detect proliferating cells [8–11] (Fig.…”

“…In our previous reports, we showed that mechanical unloading and knee immobilization increased chondrocyte apoptosis, decreased chondrocyte proliferation, and decreased the GAGs in the fibrocartilage layers in the patellar tendon insertion and ACL insertion in rabbits [8, 9]. Conversely, over load via an ACL partial tear and gradual elongation using external fixation decreased chondrocyte apoptosis, increased chondrocyte proliferation, and increased the GAGs in the fibrocartilage layers in the patellar tendon insertion and ACL insertion in rabbits [10, 11]. Therefore, we consider that chondrocyte apoptosis, chondrocyte proliferation, and GAGs can effectively reflect differences in the mechanical environment at the insertion site.…”