Effects of joint contracture on the contralateral unoperated limb in a rabbit knee contracture model: A biomechanical and genetic study

In most animal models, unoperated contralateral limbs are used as controls. However, in some experimental circumstances, the contralateral limb may represent a skewed control. The main purpose of this study was to determine if the unoperated contralateral limb could be used as a control, or if a different unoperated animal's limb should be used instead. Seventeen rabbits were divided into two groups. Group 1 rabbits (n?=?12) underwent surgery on their right limbs to induce a contracture. Group 2 rabbits (n?=?5) underwent no surgery. The left non-operated limbs of rabbits in group 1 were biomechanically and genetically compared to the limbs of unoperated rabbits in group 2 with the use of a validated joint measuring device and custom microarray, respectively. After 8 weeks of immobilization, there was a statistically greater flexion contracture in the unoperated contralateral limbs compared to the limbs of animals that received no surgery(8.4?+/-?8.9 degrees vs. 0?+/-?0 degrees; p-value?=?0.03). When animals were remobilized for an additional 16 weeks, the significance between groups was lost (11.9?+/-?21.4 degrees vs. 8.9?+/-?9.5 degrees; p?=?0.38). Similarly, there was a statistically significant increase in nine genes at 8 weeks (p?