Graft remodeling during growth following anterior cruciate ligament reconstruction in skeletally immature sheep
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Ruptures of the anterior cruciate ligament are being diagnosed with increasing frequency in skeletally immature individuals. It was our aim to investigate the graft remodelling process following an autologous, transphyseal reconstruction of the anterior cruciate ligament (ACL) in skeletally immature sheep. We hypothesized that the ligamentisation process in immature sheep is quicker and more complete when compared to adult sheep.
Materials and methods
Skeletally immature sheep with an age of 4 months underwent a fully transphyseal ACL reconstruction using an autologous tendon. The animals were subsequently sacrificed at 3, 6, 12 and 24 weeks following surgery. Each group was characterised histomorphometrically, by immunostaining (VEGF, SMA), by transmission electron microscopy (TEM) and biomechanically (UFS Roboter).
The histomorphometric analysis and presence of VEGF and SMA positive cells demonstrated a rapid return to a ligament like structure. The biomechanical analysis revealed an anteroposterior translation that was still increased even 6 months following surgery.
As in adult sheep models, the remodeling of a soft tissue graft used for ACL reconstruction results in a biomechanically inferior substitute. However, the immature tissue seems to remodel faster and more complete when compared to adults.
KeywordsAnterior cruciate ligament ACL Knee Biomechanics Sheep Graft remodeling Histomorphology Immunohistochemistry Electron microscopy Skeletally immature
The funding source of the present study was a research grant of the Research Commission of Hannover Medical School, Hannover, Germany. We gratefully acknowledge the help of Sabine Thoben and Alexandra Neddermann. The authors would like to thank Prof. Klaus Otto and Karl Napierski for their excellent animal care.
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