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Biomechanics of gait pattern adaptation in patients after Total Knee Arthroplasty

Eytan Debbie, Alon Wolf

Arthritis is ranked third, after cancer and heart disease, as a major health concern for Americans, preceding other diseases such as stroke, high blood pressure and diabetes. Osteoarthritis (OA) is the most prevalent type of arthritis and most commonly affects the knee joint. Knee osteoarthritis (KOA) affects over 21 million people in the U.S. alone. Total knee arthroplasty (TKA) is the most common treatment for end-stage KOA. TKA surgery succeeds at significantly improving the pain, function and quality of life of KOA patients. Nevertheless, some lower extremity kinematic and kinetic abnormalities have been shown to persist and continue to limit subjects' performance and quality of life. Many of these limitations are evident in gait pattern abnormalities. Their spatiotemporal gait parameters are significantly worse than controls. They walk with a slower velocity, shorter stride length and longer stance phase. In addition, knee kinematic and kinetic gait parameters are significantly worse than controls. In addition, electromyography (EMG) studies show that there is prolonged co-contraction of antagonist muscle pairs, such as rectus femoris-hamstrings and gastrocnemius-tibialis anterior. These changes lead to a “stiff knee” and a “quadriceps avoidance gait” in which patients tend to keep the knee extended throughout the stance phase of gait. In addition to the abnormal gait patterns and functional limitations, studies also suggest that TKA patients consume excess energy. Recent data suggests that the abnormalities in spatiotemporal, kinetic and kinematic parameters seen in patients after TKA are not solely due to the surgical procedure or implant misalignment, but rather can be remnants of patients’ pathological gait patterns prior to surgery. These retained pathological gait patterns have dramatic long-term effects on TKA patients aside from immediate functional limitations post-surgery. Some believe that these are the cause of excess wear and tear of the prosthetic itself that leads to early prosthetic repair in many patients. The high contact stresses result in significant wear of the prosthesis, with approximately 22% of all TKA patients return for revision within 10 years. In light of these findings, researchers stress the need to develop effective ways of inducing more normal gait patterns through motor learning. In order to meet the requirements for motor learning, these methods must incorporate challenges for the motor system in a graded and controlled fashion, with multiple repetitions within a functional context. By educating the neuromuscular system through motor learning, researchers may be able to adapt a patient's gait to walk normally even with a knee prosthesis. Gait pattern adaptation may be achieved by influencing a person’s center of pressure (COP) during functional repetitions in therapy. Such a therpay may help improve function, muscle activation patterns, energy consumption, prosthetic lifetime and KOA in the contralateral knee. This, of course, could prove to be invaluable to patients after TKA. In this study we apply a patient-specific gait adaptation therapy to patients after TKA for the course of one year. Our objectives are split according to our hypotheses. We first hypothesize that COP manipulation during dynamic loading will be able to change the forces, torques and muscle activation patterns in the lower limb. We next hypothesize that patient-specific COP manipulation combined with perturbation over time can be used as a translational therapy to the clinical setting. The therpay will induce goal-specific motor learning, thereby improving barefoot gait and muscle activation patterns, pain, function, quality of life and energy consumption in TKA patients in comparison to conventional therapy alone. As such, the following measurements are being tested: -The changes in kinetics, kinematics and muscle activation patterns during stance phase. -The changes in pain, function and quality of life. -The changes in energy/O2 consumption.