Influence of mechanical unloading on histological changes of the patellar tendon insertion in rabbits

• Published in: The knee 2015-12, Vol.22 (6), p.469-474
• Main Authors: Mutsuzaki, Hirotaka, Nakajima, Hiromi, Wadano, Yasuyoshi, Takahashi, Hikaru, Sakane, Masataka
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Biomechanical Phenomena; Cell Proliferation; Chondrocyte apoptosis; Chondrocyte proliferation; Chondrocytes - pathology; Disease Models, Animal; Glycosaminoglycan; Injuries; Insertion; Knee; Laboratory animals; Ligaments; Male; Mechanical unloading; Orthopedics; Patellar Ligament - injuries; Patellar Ligament - pathology; Patellar Ligament - physiopathology; Rabbits; Rodents; Stress concentration; Stress, Mechanical; Studies; Tendon Injuries - pathology; Tendon Injuries - physiopathology
• ISSN: 0968-0160; 1873-5800
• DOI: 10.1016/j.knee.2015.03.004

Abstract Background The purpose of this study was to clarify the influence of mechanical unloading on histological changes of the patellar tendon (PT) insertion in rabbits. Materials and methods The PT was completely released from stress by drawing the patella toward the tibial tubercle with a stainless steel wire installed between the patella and tibial tubercle (mechanical unloading group, n = 28). The animals of the sham group underwent the same surgical procedure; however, the wire was not tightened (n = 28). The average thickness of the Safranin O-stained glycosaminoglycan (GAG) area, chondrocyte apoptosis rate and chondrocyte proliferation rate of the cartilage layer at the insertion were measured at one, two, four, and six weeks. Results The chondrocyte apoptosis rate in the mechanical unloading group was significantly higher than that in the sham group at one and four weeks ( p < 0.05). The chondrocyte proliferation rate in the mechanical unloading group was significantly lower than that in the sham group at four and six weeks ( p < 0.05). The average thickness of the GAG-stained area in the mechanical unloading group was significantly lower than that in the sham group at six weeks ( p < 0.05). Conclusion Mechanical unloading significantly affected the increase in the chondrocyte apoptosis rate, decrease in the chondrocyte proliferation rate, and decrease in the GAG layer thickness at the PT insertion for up to six weeks in rabbits. Clinical relevance We suggest that more than 6 weeks of mechanical unloading should be avoided to prevent degeneration at the PT insertion.