Fig. 1
From: Anterior cruciate ligament microfatigue damage detected by collagen autofluorescence in situ
Paired knees (A – D) and single knees (E – F) experiment scheme. A Random selection of one of the paired knees for mechanical fatigue testing; B Custom in vitro loading apparatus to deliver 100 consecutive simulated sub-maximal jump landing knee loading cycles in order to repetitively strain the ACL using a weight (W) drop to apply impulsive knee compression along with an internal tibial moment via torsional device (T) activation, and quadriceps (Q), hamstring (H) and gastrocnemius (G) muscle forces. Diagram modified from Oh et al. [24]; C Extraction of ACL with trephine drill results in a femur bone (B) – ACL (L) explant followed by cryosection; D Benchtop confocal multiphoton microscopy for AF and SHG imaging of ACL sections; E Single knee undergoes two 33 consecutive cycles and one time 34 consecutive cycles completing a total of 100 fatigue loading cycles with interruptions due to dual probe imaging; F Dual probe imaging using arthroscope (blue arrow) and CLEM (red arrow) through two ports for joint visualization and AF imaging respectively. CLEM set up includes the base unit, display monitor and the 4 mm diameter handheld probe attached to the base unit