Anterior cruciate ligament insertion after partial tear: histological changes and chondrocyte turnover
Masataka Sakane1, Hirotaka Mutsuzaki, Hiromi Nakajima
1Department of Orthopaedic Surgery, Institute of Clinical Medicine, Graduate School of Comprehensive Human Science, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, 305-8575, Japan. sakane-m@md.tsukuba.ac.jp
Purpose:
The purpose of this study was to clarify the effects of partial resection on the glycosaminoglycan (GAG) layer thicknesses and chondrocyte turnover (apoptosis and cell proliferation) between uncalcified fibrocartilage (UF) and calcified fibrocartilage (CF) layers in an anterior cruciate ligament (ACL) insertion.
Methods:
Twenty male Japanese white rabbits were evaluated. The anteromedial bundle of the ACL substance was resected in the right knee. The posterolateral bundle was left intact. Five rabbits were evaluated at 1, 2, 4, and 8 weeks after surgery, respectively.
Results:
The apoptosis rates in the UF and CF layers were significantly lower in the posterolateral area than those in the anteromedial area at 1 and 2 weeks, respectively. The cell proliferation rates in the UF and CF layers were significantly higher in the posterolateral area than those in the anteromedial area at 2 and 4 weeks, respectively. The GAG layer thicknesses in the UF and CF layers were higher in the posterolateral area than those in the anteromedial area at 1-8 and 2-8 weeks, respectively. The GAG layer thicknesses in the UF and CF layers in the posterolateral area peaked at 2 and 4 weeks, respectively. However, the thicknesses in the two layers in the posterolateral area gradually decreased until 8 weeks.
Conclusion:
The GAG layer thicknesses in the UF and CF layers in the remaining ligament area increased up to 4 weeks and gradually decreased until 8 weeks owing to an imbalance between chondrocyte apoptosis and proliferation. If the reactions in humans are similar to those observed in the rabbits, we consider that augmentation for ligament reconstruction and partial repair should be performed within at least 1 month after injury, before insertion degeneration occurs.
