Influence of Gait Cycle Loads on Stress Distribution at The Residual Limb/Socket Interface of Transfemoral Amputees: A Finite Element Analysis

Abstract

A Finite Element Analysis (FEA) was performed to evaluate the interaction between residual limb and socket when considering the dynamic loads of the gait cycle. Fourteen transfemoral amputees participated in this study, where their residual limbs (i.e., soft tissues and bone), and their sockets were reconstructed. The socket and the femur were defined as elastic materials, while the bulk soft tissues were defined as a hyperelastic material. Each model included the donning, standing, and gait cycle phase, with load and boundary conditions applied accordingly. The influence of adding the dynamic loads related to the gait cycle were compared against the modelling of the static load equivalent to the standing position resulting in changes of 23% ± 19% in the maximum values and in an increase in the size of the regions where they were located. Additionally, the possible correspondence between comfort and the location of peak loadbearing at the residual-limb/socket interface was explored. Consequently, the comfort perceived by the patient could be estimated based on the locations of the maximum stresses (i.e., if they coincide with the pressure tolerant or sensitive regions of the residual limb).In lower limb amputees, specifically for limb amputations above knee level, the prosthetic system consists mainly of a prosthetic foot, a prosthetic knee and a socket. Since the attachment between the residual limb and the prosthesis occurs through the socket, its coupling is critical for patients looking to regain their functional mobility and perceiving comfort 1,2 . Among others, the main task of the socket is to distribute the loads applied on the residual-limb/socket interface. By doing this, the stresses generated at the residual limb in sensitive areas are reduced, and gait becomes stable by allowing adequate proprioception and movement of the residual limb muscles 3-5 (all of this during a prolonged loading time 6 ). Thus, the residual-limb/socket interface is a key factor in the successful performance of the patient during his/her rehabilitation 7 .When wearing a prosthesis, both normal (i.e., perpendicular to the skin) and shear stresses (i.e., tangential to the skin) are applied to the soft tissues of the residual limb, which are not accustomed to bear such elevated loads, inducing the risk of skin problems and chronic pain 1,2,6 . Recommendations for transtibial socket design based on Pain Pressure Thresholds (PPT) have been defined by other authors since pressure beyond certain limit triggers pain 8,9 and pressure is the condition that most critically increases skin problem and chronic pain risks at the residual-limb/socket interface 10 . Moreover, the existence of algometers as reliable medical devices for measuring PPT 11,12 can lead to easier implementation of new protocols for socket design where pressure tolerant and sensitive regions at the residual limb are defined according to the PPT that patients can endure based on their perception 2,6,13,14 . These thresholds are established when critical stresses and s...

A Scoping Review of Pressure Measurements in Prosthetic Sockets of Transfemoral Amputees during Ambulation: Key Considerations for Sensor Design

“…For example, one of the aims of adjustable sockets is to reduce pressures and shear stresses at the stump-socket interface. In line with traditional socket design theory, the adjustable socket adapts to equally distribute pressure across the residual limb, or relieves pressure from sensitive regions by exerting more pressure through more tolerant regions [14,23,[27][28][29]. Furthermore, continuous socket volume adjustments have been shown to promote residual limb volume management [9].…”

Analyzing Dynamic Operational Conditions of Limb Prosthetic Sockets with a Mechatronics-Twin Framework

“…For example, the study by [22] suggested FEM can be classified as an alternative method to evaluate the pre-fabrication prosthetic device. In [23], an investigation of FEA for estimating the dynamic interactions between limb and socket was also introduced. The socket and femur were defined as elastic materials, while the bulk soft tissues were defined as a hyperelastic material.…”

Editorial: Bionics limb prostheses: Advances in clinical and prosthetic care

“…Residuum health is influenced by intrinsic determinants inherent to personal demographics (e.g., gender, age, weight, and height) and surgical amputation (e.g., length of bone, muscle reassignments, muscle strength, and adipose tissue distribution) and extrinsic determinant-associated attachment (e.g., socket design and direct skeletal attachment) and prosthetic components (e.g., choice and alignment of components, control of the prosthetic joint movements, use of walking aids, and level of activity) ( 8 ). In all cases, interactions between intrinsic and extrinsic determinants are critical as residual tissues have limited physiological capacity to withstand direct loading applied by typical socket-suspended prostheses during daily activities (e.g., chafing and rubbing) ( 5 , 9 – 12 ). In addition to general neurological residuum and phantom pain, individuals can experience a range of incapacitating neuromusculoskeletal dysfunctions compromising residuum health, such as acute and chronic skin issues, edema, neuroma, tendinitis, muscle contractures, stress fractures, osteopenia, and heterotopic bone growth, which altogether increases the risks of sound lower joints osteoarthrosis, and hyperlordosis ( 6 , 13 , 14 ).…”