Effectively addressing population-level variability within orthopedic analyses requires robust data sets that span the target population and can be greatly facilitated by statistical methods for incorporating such data into functional biomechanical models. Data sets continue to be disseminated that include not just anatomical information but also key mechanical data including tissue or joint stiffness, gait patterns, and other inputs relevant to analysis of joint function across a range of anatomies and physiologies. Statistical modeling can be used to establish correlations between a variety of structural and functional biometrics rooted in these data and to quantify how these correlations change from health to disease and, finally, to joint reconstruction or other clinical intervention. Principal component analysis provides a basis for effectively and efficiently integrating variability in anatomy, tissue properties, joint kinetics, and kinematics into mechanistic models of joint function. With such models, bioengineers are able to study the effects of variability on biomechanical performance, not just on a patient-specific basis but in a way that may be predictive of a larger patient population. The goal of this paper is to demonstrate the broad use of statistical modeling within orthopedics and to discuss ways to continue to leverage these techniques to improve biomechanical understanding of orthopedic systems across populations.
BackgroundA new morphometric fixed-bearing unicompartmental knee arthroplasty (UKA) system has been introduced to address the anatomical patient-specific challenges. It was our hypothesis that accurate restoration of the patient-specific anatomy would restore normal knee kinematics after UKA. Therefore, we aimed in this cadaveric study to analyze the impact of a medial morphometric UKA on (1) the varus-valgus and anterior-posterior stability of the knee, (2) the knee kinematics during standardized activities of the daily living, and (3) the patellar tracking, measured using a dedicated robotic testing protocol.MethodsEight human knee specimens underwent full-leg computed tomography CT scanning and comprehensive robotic assessments of tibiofemoral and patellofemoral kinematics. Specimens were tested in the intact state and after implantation of a fixed-bearing medial UKA. Assessments included passive flexion, laxity testing and simulations of level walking, lunge, and stair descent.ResultsMedial and lateral joint laxity after UKA closely resembled intact laxity across the full arc of flexion. Anterior-posterior envelope of motion showed a close match between the intact and UKA groups. Net rollback and average laxity were both not statistically different. Simulation of activities of daily living showed a close match in the anterior-posterior motion profile between the medial condyle and lateral condyle. Patellar tilt and medial-lateral shift during knee flexion matched closely between groups.ConclusionFunctional assessment of this UKA system shows nearly identical behavior to the intact knee. Fixed-bearing UKA with morphometric, compartment-specific geometry and precise mechanical instrumentation replicates complex knee balance and kinematics.
Introduction In knee biomechanics the concept of the envelope of motion (EOM) has proven to be a powerful method to characterize joint mechanics and the effect of surgical interventions. It is furt...
Passive knee kinematics and kinetics following total knee replacement (TKR) are dependent on the topology of the component joint surfaces as well as the properties of the passive soft tissue structures (ligaments and capsule). Recently, explicit computer models have been used for the prediction of knee joint kinematics based on experimental investigations [1]. However, most of these models replicate experimental knee simulators [2], which simulate soft tissue structures using springs or elastomeric structures. New generations of experimental setups deploy industrial robots for measuring kinematics and kinetics in six degrees of freedom as well as the contribution of soft tissue structures. Based on these experiments, accurate soft tissue properties are available for use in computer models to aid more realistic predictions of kinematics. Final evidence of the quality of the kinematic predictions from these computer models can be provided by direct validation of the models against experimental data. Therefore, the objective of this study was to use in vitro robotic test data to develop, verify, and validate specimen specific virtual models suitable for predicting laxity and kinematics of the reconstructed knee.
Introduction Partial knee arthroplasty (PKA) has demonstrated the potential to improve patient satisfaction over total knee arthroplasty. It is however perceived as a more challenging procedure tha...
IntroductionAdvancements in knee surgery require a profound understanding of knee mechanics. However, there are seemingly contradicting reports regarding certain aspects of normal knee function, su...
Introduction Total-knee-arthroplasty (TKA) is used to restore knee function and is a well-established treatment of osteoarthritis. Along with the widely used fixed bearing TKA design, some surgeons opt to use mobile bearing designs. The mobile-bearing TKA is believed to allow for more freedom in placement of the tibial plate, greater range of motion in internal-external (IE) rotation and greater constraint through the articular surface. This current study evaluates 1) the kinematics of a high constraint three condyle mobile bearing TKA, 2) the insert rotation relative to the tibia, and 3) compares them with the intact knee joint kinematics during laxity tests and activities-of-daily-living (lunge, level walking, stairs down). We hypothesize that 1) in contrast to the intact state the anterior-posterior (AP) stability of the implanted joint increases when increasing compression level while 2) maintaining the IE mobility, and that 3) the high constraint does not prevent differential femorotibial rollback du...
We experimentally study steady Marangoni-driven surfactant transport on the interface of a deep water layer. Using hydrodynamic measurements, and without using any knowledge of the surfactant physico-chemical properties, we show that sodium dodecyl sulphate and Tergitol 15-S-9 introduced in low concentrations result in a flow driven by adsorbed surfactant. At higher surfactant concentration, the flow is dominated by the dissolved surfactant. Using Camphoric acid, whose properties are {\it a priori} unknown, we demonstrate this method's efficacy by showing its spreading is adsorption dominated.
INTRODUCTIONClinical studies have shown that the knee tends to experience laterally higher AP motion (posterior directed) than medially (Asano at al., 2001; Dennis et al., 2005; Hill et al., 2000; Moro Oka et al., 2007). Traditional posterior stabilized (PS) total knee arthroplasty (TKA) designs allow deep flexion stability and femoral rollback once cam/spine engagement occurs, however mechanical stability provided by tibial bearing conformity during early to mid-flexion is highly variable. In this study a computer knee model is used to compare AP kinematics in PS TKA designs while evaluating multiple sagittal tibia bearing conformities. We hypothesized that highly conforming designs would be necessary to promote AP stability prior to cam/spine engagement.METHODA specimen specific computer model consisting of the femur, tibia and fibula, as well as the contribution of the ligaments and capsule was virtually implanted with TKA designs of the appropriate size at 5° tibia slope with the posterior cruciate li...
