Rabbit knee model of post‐traumatic joint contractures: The long‐term natural history of motion loss and myofibroblasts

Abstract

Our objective is to describe the natural history of motion loss with time and myofibroblast numbers in a rabbit knee model of post-traumatic joint contractures. Twenty-eight skeletally mature New Zealand White female rabbits had five-mm-squares of cortical bone removed from the medial and lateral femoral condyles of the right knee. A Kirschner wire (K-wire) was used to immobilize the knee joint in maximum flexion. A second operation was performed 8 weeks later to remove the K-wire. The rabbits were divided into four groups depending on the time of remobilization; 0, 8. 16 or 32 weeks.The average flexion contracture of the experimental knees in the 0-week and 8-week remobilization groups (38" and 33", respectively) were significantly greater when compared with the values of the unoperated contralateral knees (SO). The average flexion contractures of the experimental knees in the 16-week and 32-week remobilization groups were also greater than the Linoperated contralateral knees, although they were not statistically significant. The average flexion contractures of the 16-week and 32-week groups were 19" and 18", respectively, indicating a stabilization of the motion loss. Myofibroblast numbers in the posterior joint capsules were elevated 4-5x in the knees with contractures when compared to the contralateral knees. The initial decrease in severity followed by stabilization of motion loss and the association of motion loss with myofibroblasts mimics the human scenario of permanent post-traumatic joint contractures.

Comparison of muscular and articular factors in the progression of contractures after spinal cord injury in rats

“…Hildebrand et al 17 have studied the recovery process of post-traumatic contractures with immobilized rabbit knees for 8 weeks followed by remobilization. They have shown that contracture severity decreases with time although it does stabilize in the long term and that processes involved are somewhat altered depending on the underlying etiology of the contracture process.…”

“…Most information obtained on contracture formation over time is based on animal models with contractures produced by immobilizing joints with internal fixation (with plate or splint), 5,6,[9][10][11] external fixation (with cast, bandage, or splint), [12][13][14] pinning, 15 wiring, 16,17 or a combination of these procedures. Contractures after immobilization mainly result from stress deprivation of joints.…”

New rabbit knee model of posttraumatic joint contracture: Indirect capsular damage induces a severe contracture

“…Rabbits in group II (n ¼ 16) were operated on using an identical protocol except for the absence of capsular injury, as described by Hildebrand et al 7 Eight rabbits in each group were sacrificed 8 weeks after the procedure (subgroups IA and IIA). The remaining eight rabbits in each group had their immobilization removed and were allowed free activity in a cage for 16 weeks before being sacrificed (subgroups IB and IIB).…”

“…The 16-week remobilization time period was selected based on previous observations of a plateau in spontaneous motion gains after 16 weeks of free cage activity. 7 After prepping and draping the animals in the usual sterile fashion, inhalational general anesthesia was induced with isoflurane (1%-2%). A 15-blade scalpel was used to make a 1-cm longitudinal skin incision over the tibia.…”

“…Pharmacologic treatment strategies have been developed and are being used for the treatment of other profibrotic conditions; examples include pulmonary fibrosis, renal fibrosis, and hypertrophic scars. The use of antifibrotic pharmacologic therapies for the prevention and treatment of joint contracture is attractive, [5][6][7] but needs to be explored in animal models before its widespread application in humans. Differences in joint contracture with pharmacologic therapy will be difficult to prove using animal models resulting in small nonpermanent contractures.…”