Modeling Implantable Passive Mechanisms for Modifying the Transmission of Forces and Movements Between Muscle and Tendons

Abstract

Abstract-This paper explores the development of biomechanical models for evaluating a new class of passive mechanical implants for orthopedic surgery. The proposed implants take the form of passive engineered mechanisms, and will be used to improve the functional attachment of muscles to tendons and bone by modifying the transmission of forces and movement inside the body. Specifically, we present how two types of implantable mechanisms may be modeled in the open-source biomechanical software OpenSim. The first implant, which is proposed for hand tendon-transfer surgery, differentially distributes the forces and movement from one muscle across multiple tendons. The second implant, which is proposed for knee-replacement surgery, scales up the forces applied to the knee joint by the quadriceps muscle. This paper's key innovation is that such mechanisms have never been considered before in biomechanical simulation modeling and in surgery. When compared with joint function enabled by the current surgical practice of using sutures to make the attachment, biomechanical simulations show that the surgery with 1) the differential mechanism (tendon network) implant improves the fingers' ability to passively adapt to an object's shape significantly during grasping tasks (2.74× as measured by the extent of finger flexion) for the same muscle force, and 2) the force-scaling implant increases knee-joint torque by 84% for the same muscle force. The critical significance of this study is to provide a methodology for the design and inclusion of the implants into biomechanical models and validating the improvement in joint function they enable when compared with current surgical practice.Index Terms-Biomechanical modeling, implant design, orthopedic surgery.

OpenSim: Simulating musculoskeletal dynamics and neuromuscular control to study human and animal movement

“…Open access to human and animal models and recent improvements to the software (see Design and implementation ) have expanded the scope of studies that are performed with OpenSim. Comparative biologists are using OpenSim to study relationships between form and function in animals [ 12 , 72 – 76 ], and engineers are using OpenSim to design and analyze assistive devices [ 14 – 17 ]. Researchers are also using OpenSim to create models of reflexes and spinal circuits [ 20 , 40 , 77 , 78 ] to understand movement disorders or prevent injury.…”

“…OpenSim is being used to design implantable and exoskeletal devices. For example, Homayouni and colleagues [ 14 ] used OpenSim to prototype new passive, implantable mechanisms for hand tendon transfer surgery to improve grasp performance and restore function in patients with partial paralysis of the upper extremity. The goal of the mechanisms is to achieve a grasp that evenly distributes forces between the fingers—a key limitation of current tendon transfer procedures.…”

“… In current practice, individuals with partial paralysis of the upper limb receive tendon transfer surgeries to reconnect the tendons that facilitate finger movement to a non-paralyzed donor muscle. Homayouni and colleagues [ 14 ] are designing implantable devices to improve outcomes of traditional, suture-based tendon transfer. In one design (A), the single-suture attachment is replaced with an artificial tendon network.…”

“…The implantable devices (green and blue) achieved greater finger flexion (C) than the traditional suture-based surgery (black). Adapted from Homayouni et al [ 14 ].…”

“…Second, OpenSim can be used to simulate musculoskeletal dynamics and neuromuscular control. Simulations enable researchers to pursue studies that are difficult to perform experimentally, such as investigating how humans and animals exploit tendon elasticity to make running more efficient [ 11 – 13 ] and optimizing the design of implantable mechanisms and assistive devices [ 14 – 18 ]. Third, using solely principles of neuromuscular control and dynamic simulation, OpenSim can be used to predict novel movements and adaptations to novel conditions, without performing any experiments.…”