Abstract
Introduction
Traditional Total Knee Arthpolasty (TKA) replaces all 3 compartments of the knee for patients diagnosed with OA. There might be functional benefit to replacing only damaged compartments, and retaining the normal ligamentous structures. There is a long history of performing multi-compartment arthroplasty with discrete components. Laskin reported in 1976 that good pain relief and acceptable clinical results were achieved at two years in patients with bi-unicondylar knee replacement [Laskin 1976]. Other authors also have reported on bi-unicompartmental knee arthroplasty achieving successful clinical outcomes [Stockley 1990; Confalonieri 2005]. Banks et al. reported that kinematics of bi-unicompartmental arthroplasties during gait demonstrated some of the basic features of normal knee kinematics [Banks 2005]. These reports suggest that a modular approach to resurfacing the knee can be successful and achieve satisfactory clinical and functional results.
Objective
The primary objective of this study is to compare the functional outcomes of three patient groups treated for osteoarthritis.
Methods
Subjects received either a modular, multicompartment knee arthroplasty (MKA) implanted with robotic-arm assistance(MAKO Surgical Corp., Fort Lauderdale, FL), a computer assisted TKA (TKA CAS) or a TKA implanted using traditional manual instrumentation (TKA T). Patients that were eligible to receive a TKA were randomly selected to receive computer assisted or traditional surgical technique and blinded to the type of TKA surgical technique utilized. We report post-operative functional outcomes including Range of Motion (ROM), Timed-up and go(TUG), and Quad strength at time intervals of 2 weeks, 6 weeks, 3 months and 6 months. The TUG test is a validated measure of patient mobility where a patient is asked to stand up from a chair, walk three meters turn around and sit back down [Boonstra, 2008]. The Quad strength assessment is measured with a hand held dynamometer (Lafayette Instruments, Lafayette, IN) while patient was seated with leg at 90 degrees flexion. The patient is asked to extend their knee while a physical therapist provides resistive forces to maintain static knee flexion. All tests were administered by one physical therapist.
Results
Patients that underwent MKA saw significant increase in ROM post-operatively when compared to TKA CAS patients (P<0.009) and TKA T patients (p<0.003), Figure 1. Patients that underwent MKA also saw an increase in Quad Strength, however this was only statistically significant between the MKA and TKA CAS groups, (P<0.04), Figure 2. Patients that underwent MKA saw a reduction in TUG which indicated an improved mobility post-operatively, Figure 3. The reduced TUG was only statistically significant for MKA patients compared to TKA T patients (P<0.005). There was no statistical significance seen between the two TKA groups for any functional measure.
Discussion
Initial findings do indicate a short term improvement in functional outcomes for MKA patients when compared to TKA patients. Additional data clinical and functional data is being collected and enrollment is continuing for this study.
