The 2011 ABJS Nicolas Andry Award: ‘Lab’-in-a-Knee: In Vivo Knee Forces, Kinematics, and Contact Analysis

Abstract

Background Tibiofemoral forces are important in the design and clinical outcomes of TKA. We developed a tibial tray with force transducers and a telemetry system to directly measure tibiofemoral compressive forces in vivo. Knee forces and kinematics traditionally have been measured under laboratory conditions. Although this approach is useful for quantitative measurements and experimental studies, the extrapolation of results to clinical conditions may not always be valid. Questions/purposes We therefore developed wearable monitoring equipment and computer algorithms for classifying and identifying unsupervised activities outside the laboratory. Methods Tibial forces were measured for activities of daily living, athletic and recreational activities, and with orthotics and braces, during 4 years postoperatively. Additional measurements included video motion analysis, EMG, fluoroscopic kinematic analysis, and ground reaction force measurement. In vivo measurements were used to evaluate computer models of the knee. Finite element models were used for contact analysis and for computing knee kinematics from measured knee forces. A thirdgeneration system was developed for continuous monitoring of knee forces and kinematics outside the laboratory using a wearable data acquisition hardware. Results By using measured knee forces and knee flexion angle, we were able to compute femorotibial AP translation (À12 to +4 mm), mediolateral translation (À1 to 1.5 mm), axial rotation (À3°to 12°), and adduction-abduction (À1°t o +1°). The neural-network-based classification system was able to identify walking, stair-climbing, sit-to-stand, and stand-to-sit activities with 100% accuracy. Conclusions Our data may be used to improve existing in vitro models and wear simulators, and enhance prosthetic designs and biomaterials.

Damage in total knee replacements from mechanical overload

“…Recent in vivo studies using instrumented total knee replacements have shown that the loading magnitude applied across the knee joint can vary considerably depending on activity (Bergmann et al, 2014; D’Lima et al, 2012; D’Lima et al, 2011). In addition, infrequent high demand loading situations such as stumbling (Bergmann et al, 2004) could potentially damage the fixation of TKRs and this might lead to eventual clinical loosening.…”

Analysis of weight distribution strategies in unilateral transtibial amputees during the stand-to-sit activity.

“…The period between Descent Deceleration and Seat-Contact can be considered to be the most challenging phase of the StTS movement as knee forces greater than 2.5 times body weight have been recorded during this period of unassisted StTS movement (Mundermann et al 2008;D'Lima et al 2011)._ENREF_11 During this period, the quadriceps muscle group is contracting eccentrically at roughly 43% maximum voluntary contraction, in an effort to control the CoM descent to the chair (Wang et al, 2005;Wang et al, 2012). The ability to maintain balance during the Seat-Contact phase is also critical M a n u s c r i p t -especially for sitting with no arm-assistance -as the body is in a flexed position, with the ankle, knee, hip and trunk at or close to their peak flexion angle during the activity ( Kralj et al, 1990;Kerr et al, 1994;Kerr et al, 1997).…”

Analysis of an Early Intervention Tibial Component for Medial Osteoarthritis

“…In this study, axial loading was shifted anteriorly and posteriorly ±7 mm from the center loading condition to analyze possible contact locations in extension and full flexion. On the medial side, a downward force of 1500 N was applied in the direction of the long axis of the tibia over an area of 40 mm" which is a representative contact area for metal on plastic components during walking [21]. The medial load was applied directly to the surface of the tibial component.…”