Design, development and validation of adjustable knee brace using experimental and computational methods

在前十字韧带(ACL)重建手术后，膝关节支撑经常被用来稳定膝关节。目前还不存在允许在康复期间逐渐加载膝关节结构从而使组织能够适当愈合的膝关节支架。我们建议使用体内/体外相结合的方法来验证用于测试膝关节支架设计的人膝关节的详细有限元模型。验证后的有限元模型将用于设计具有渐进加载/卸载膝关节结构的能力的新膝关节支架。运动捕捉将在进行正常活动(如行走和蹲下)的现场男性受试者身上进行。运动捕捉数据将被输入到刚体生物力学模型中，以计算在这些活动期间腿部肌肉的力量分布。将获得10个新鲜冰冻的身体膝盖。膝盖将被解剖，肌肉将被与僵硬肌肉的弹性模数相匹配的泡沫所取代。然后，动态膝关节模拟器系统将生理肌力和膝关节运动学(通过生物力学模型计算)应用于带和不带支架的身体膝盖。将使用植入的传感器测量前交叉韧带应变。然后提取膝关节韧带和半月板组织并进行拉伸测试，以获得这些组织的力学性能。组织的材料属性将被分配给高级膝关节有限元模型，该模型将受到与动态膝关节模拟器中相同的载荷。将得到的前交叉韧带和半月板应变与实验结果进行比较，以验证模型的有效性。然后将开发一种新的膝盖支撑设计。该大括号将支持自定义ACL加载。新设计将使用经过验证的有限元模型进行优化。新的可调式膝关节支架的不同配置与由此产生的前交叉韧带应变之间的关系将被推导出来。新的设计可以减少ACL重建的失败，从而降低相关的医疗成本。

Knee braces are often used to stabilize the knee joint following anterior cruciate ligament (ACL) reconstructive surgery. There currently exists no knee brace that allows gradual loading of the knee structures over the rehabilitation period thereby enabling proper healing of the tissue. We propose to use a combined in-vivo/in-vitro methodology to validate a detailed finite element model of human knee for testing knee brace designs. The validate finite element model would then be used design a new knee brace with the capability to progressively load/unload knee structures. Motion capture will be performed on live male subject performing normal activities such as walking and squatting. The motion capture data will be input into a rigid body biomechanical model to calculate muscle force profiles in the lower extremity during those activities. Ten fresh frozen cadaver knees will be obtained. The knees will be dissected the muscles will be substituted by foam that matches the modulus of elasticity of the stiff muscles. A dynamic knee simulator system then applies physiological muscle forces and knee kinematics (as calculated through the biomechanical model) on the cadaver knees, with and without braces. ACL strain will be measured using implanted transducers. The knee ligament and meniscal tissues will then be extracted and tested in tension to obtain the mechanical properties of these tissues. The material properties of the tissues will be assigned to an advanced FE model of the knee which will be subjected to same loading as subjected to in the dynamic knee simulator. The resulting ACL and meniscal strains will be compared with experimental results to validate the model. A new knee brace design will then be developed. The brace would enable the customization of ACL loading. The new design will be optimized using the validated FE model. Relationship between various configurations of the new adjustable knee brace and resulting ACL strain will be derived. The new design could result in lesser failed ACL reconstruction thereby decreasing the associated healthcare costs.