The effects of simulated knee arthrodesis on gait kinematics and kinetics.

Knee arthrodesis is commonly performed to treat joint pain and instability in cases of multiple failed knee replacement surgeries, bone loss, traumatic injury, infection, or loss of the quadriceps extensor mechanism, but its mechanics are poorly understood. This study quantified the changes in gait kinematics and kinetics induced by simulating knee arthrodesis. A total of 10 healthy subjects (M/F, n = 5/5; aged 18-23) with no history of gait abnormalities were recruited for this study, and knee arthrodesis was simulated for 0 through 24 h using an immobilizing knee brace. Gait analysis was conducted during level walking on a 15-m walkway using an eight-camera motion tracking system with a six-axis ground reaction force platform. Normal gait served as each subject's control, and measurements of braced gait were taken immediately following the fitting of the brace and over a 24-h acclimation period. Results showed that simulated knee arthrodesis caused statistically significant and interrelated changes to gait when compared to normal gait, including reduced ankle plantar flexion and pelvic obliquity during swing phase of the braced limb, increased abduction of the left and braced hip during stance of the braced limb, and an increase in the net joint reaction force at the contralateral hip. These changes facilitated ground clearance of the braced limb, but however did not show increases in knee flexion moment that might serve as a cyclic fatiguing factor in implants or fusions used to fixate the knee. Increased acclimation time was not found to significantly alter braced gait kinematics, supporting the use of short-term bracing as an experimental model for the longer-term immobilized knee.