In vitro laxity-testers for knee joints of mice.
The knee joints of mice can be used as a model for studying the effects of interventions on knee laxity. The goal of this study was to quantify knee joint laxity in vitro. Three devices were developed: a positioning- and cementing device, an anterior-posterior (AP) laxity tester and a varus-valgus (VV) laxity tester. The positioning and cementing device was used to position the joint in a reproducible way and to attach clamping pins to the proximal femur and distal tibia using PM MA. The clamping pins were used to fix the joint to the AP- and VV-testers. In both testers the load was applied by means of a spindle-actuated spring while load and displacements were measured simultaneously. The load--displacement data were used to calculate displacement and compliance parameters. The performance of the testers was evaluated by testing 5 normal knee joints of 5 mice. Total AP-translation at + or - 0.8 N was 0.43 (+ or - 0.16 S.D.) mm with compliances of 0.14 (+ or - 0.05 S.D.) mm N(1) and 0.12 ( + or - 10.05 S.D.) mm N(-1) at 0.8 N posterior and anterior force, respectively. Total VV-rotation at + or - 4 Nmm was 17.2 (+ or - 2.6 S.D.) degrees with compliances of 0.9 degrees Nmm(-1) (+ or - 0.2 degrees Nmm(-1) S.D.) and 1.0 Nmm(-1) (+ or - 0.4 degrees Nmm(-1) S.D.) at 4 Nmm valgus and varus moment, respectively. The contributions of the deformations of the bones and the fixtures to the rotations were negligible in the VV-test. In the AP-test they account for approximately 0.07 ( + or - 0.03 S.D.)mm of the total AP-translation. This will not affect the utilization of the device for comparative analysis. It is concluded that in in vitro evaluation of AP- and VV-laxity in knees of mice is feasible with sufficient accuracy for evaluation of changes after ligament damage.
Blankevoort
L
L
Biomechanics Section, Institute of Orthopaedics, University of Nijmegen, The Netherlands.
van Osch
G J
GJ
Janssen
B
B
Hekman
E E
EE
D000818:Animals; D001843:Bone Cements; D001858:Bone Nails; D003187:Compliance; D004867:Equipment Design; D005069:Evaluation Studies as Topic; D005240:Feasibility Studies; D005269:Femur / Q000473:pathology; D006614:Hindlimb / Q000473:pathology / Q000503:physiopathology*; D007593:Joint Instability / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D007596:Joints / Q000473:pathology / Q000503:physiopathology*; D008023:Ligaments, Articular / Q000473:pathology / Q000503:physiopathology; D008768:Methylmethacrylates; D051379:Mice; D008810:Mice, Inbred C57BL; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D012399:Rotation; D013314:Stress, Mechanical; D013977:Tibia / Q000473:pathology
D001843:Bone Cements; D008768:Methylmethacrylates