Background In-vivo as well as in-vitro studies on osteoarthritis have their advantages and disadvantages. A novel ex-vivo/in-vitro whole stifle joint bio-mechano-reactor allowing individual modulation of biochemical and biomechanical conditions is being developed, with the advantage of studying the joint as a whole able to modulate and monitor all different aspects.
Objectives As main objective, reproduction of joint-specific biomechanics is aimed for. Passive femoral-tibial kinematics and contact surface are analyzed and incorporated in an inverse dynamics model, beeing subject of this study.
Methods Four right hind limbs without muscle tissues but with intact bone-cartilage interface, including ligaments of Mongrel dogs (±22kg, ±1.5yrs) were analyzed and used in a model of the bioreactor setup. A micro-CT scanner (quantum-FX, Perkin-Elmer) was used for modeling of the whole stifle joints in multiple flexion angles in normal range of motion (30-70degrees). As reference, six stainless steel markers were placed. Slicer3D (v4.3.1) and Meshlab (v1.3.2) were used for post-processing. Kinematics were derived with a MATLAB (vR2013B) algorithm, and implemented in an OpenSim inverse-dynamics-model.
Preliminary contact area analysis was performed with a contrast enhanced micro-CT scan 30min after injection with 9mL Hexabrix (38%)-PBS (62%) to one stifle joint.
Results Joint-specific passive femoral-tibial kinematics (fig.1A) were derived and could be implemented in an inverse dynamics model for application in the bio-mechano-reactor. Intervals between measured flexion angles were interpolated for generating continuous motion patterns. Contact surface was distinguishable after injection of contrast agent (fig.1B).
Conclusions Despite the challenges in implementation of joint-specific biomechanics in a whole-joint-bio-mechano-reactor, micro-CT images can provide an accurate method for determining passive stifle joint kinematics. The developed kinematic model provides input for an inverse-dynamics model, enabling joint-specific load pattern simulation and application. Results have been implemented in the active bio-mechano-reactor providing a potential new tool for ex-vivo cartilage research.
Y. Fu, B. T. Torres, and S. C. Budsberg, Evaluation of a three-dimensional kinematic model for canine gait analysis, American journal of veterinary research, vol. 71, no. 10, pp. 1118–1122, 2010.
B. H. Nelson, D. D. Anderson, R. a Brand, and T. D. Brown, Effect of osteochondral defects on articular cartilage. Contact pressures studied in dog knees, Acta orthopaedica Scandinavica, vol. 59, no. 5, pp. 574–9, Oct. 1988.
T. T. Dao, P. Pouletaut, J.-C. Goebel, a. Pinzano, P. Gillet, and M. C. Ho Ba Tho, In vivo characterization of morphological properties and contact areas of the rat cartilage derived from high-resolution MRI, Irbm, vol. 32, no. 3, pp. 204–213, Jun. 2011.
Disclosure of Interest None declared