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Orthopaedics
Published in Kelvin Yan, Surgical and Anaesthetic Instruments for OSCEs, 2021
This is a knee prosthetic implant which is used for a total knee arthroplasty (TKA) (Figure 8.2). It can be made of metal alloys plus ceramic or plastic parts. It has 3 components: the femoral part, the patella part and the tibial component with a plastic spacer. The rationale is to recreate the surfaces of the hinge joint of the knee by first removing damaged bones and/or cartilages and replacing them with metal prostheses and a plastic spacer to ensure better movement and reduce wear and tear. The femoral component has various forms including the posterior-stabilised design, the cruciate-retaining design and the bicruciate-retaining design. The posterior-stabilised design involves removing the cruciate ligaments and replacing it with a centre post-cam design in the prosthesis that substitutes the function of the posterior cruciate ligament. The Cruciate-retaining design requires the retention of the posterior cruciate ligament as it does not offer a substitution. The Bicruciate-retaining design, on the other hand, is a relatively new design that requires the retention of both the anterior and posterior cruciate ligaments with the aim to mimic the human knee as closely as possible.
Examination of Knee Joint in a Child
Published in Nirmal Raj Gopinathan, Clinical Orthopedic Examination of a Child, 2021
The knee joint is a modified type of hinge joint. Flexion and extension take place around a variable transverse axis. Flexion is leg movement in the posterior direction until the calf meets the posterior aspect of the thigh. Extension is leg movement in the anterior direction leading to straight alignment of the thigh and leg in the sagittal plane. Full extension is usually recorded as 0°. From the position of 0° extension, the flexion range is usually about 0–150° (Figure 10.7).
Hip and knee
Published in Professor Sir Norman Williams, Professor P. Ronan O’Connell, Professor Andrew W. McCaskie, Bailey & Love's Short Practice of Surgery, 2018
Professor Sir Norman Williams, Professor P. Ronan O’Connell, Professor Andrew W. McCaskie
The knee joint is a synovial hinge joint. It consists of two condyloid tibiofemoral joints and a sellar (or saddle shaped) patellofemoral joint. The shape makes the joint inherently unstable, but stability is achieved by a combination of static (ligaments) and dynamic (muscles) stabilisers acting across the joint.
Review of ankle rehabilitation devices for treatment of equinus contracture
Published in Expert Review of Medical Devices, 2022
Kamila Dostalova, Radek Tomasek, Martina Kalova, Miroslav Janura, Jiri Rosicky, Marek Schnitzer, Jiri Demel
Sawicki and Ferris [75] expanded this AAFO design to knee-ankle foot orthoses (KAFO) see Figure 3b [75]. The KAFO uses antagonistic pairs of pneumatic artificial muscles for ankle plantarflexion/dorsiflexion and for knee extension/flexion. For ankle, there is an additional DOF for eversion/inversion. The KAFO design is custom-fitted and lightweight (2.9 kg) and consists of a polypropylene foot section, a carbon fiber shank, and a carbon fiber thigh. The free movement in both the knee and the ankle is provided by the hinge joints. It is complemented by four pneumatic actuators for the thigh segment and two for the shank, attached to the orthosis via stainless steel brackets. Three healthy male subjects were fitted with this KAFO. The current orthosis design provided less mechanical assistance about the knee than about the ankle. Artificial muscles per- formed more positive mechanical work than negative mechanical work during the gait cycle. The proportional myoelectric control with flexor inhibition allowed for a more normal gait than direct proportional myoelectric control.
A multi-body model for comparative study of cervical traction simulation – development, improvement and validation
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
Lawrence K. F. Wong, Zhiwei Luo, Nobuyuki Kurusu, Keiji Fujino
In both positions, the vertex of the traction angle is set at a fixed point at the chair, near the back of the first thoracic vertebra (T1) of the subject. In the simulation model, T1 connects the base of the cervical spine to the rest of the upper body. The upper limbs and forearm are modeled as rigid bodies and are connected to the shoulder with hinge joints. The hip joint is a hinge joint that connects to the thighs. Since the subject is heavy enough that the friction at the seat prevents the subject from sliding along the seat, the thighs and the rest of the lower body are modeled as fixed structure attached to the traction devices. This design allows the subject to remain stable during traction. It also matches the observed behavior of the human subjects in our radiographic experiment.
Non-rigid deformation to include subject-specific detail in musculoskeletal models of CP children with proximal femoral deformity and its effect on muscle and contact forces during gait
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
Mariska Wesseling, Lode Bosmans, Christophe Van Dijck, Jos Vander Sloten, Roel Wirix-Speetjens, Ilse Jonkers
MRI models were defined for all subjects based on the acquired MR images using a dedicated workflow (Figure 1) (Scheys et al. 2006). Bone structures of the pelvis, femora, patellae and tibiae were segmented from the images (Mimics Innovation Suite, Materialise N.V., Leuven, Belgium). The hip joint center was determined by fitting a sphere to the femoral head using an iterative closest point algorithm (Besl and McKay 1992). The knee joint was modelled as a sliding hinge joint (Yamaguchi and Zajac 1989), where the knee axis was based on the geometry of the distal femur, by connecting the centers of two spheres fitted to the lateral and medial posterior condyles. Segmental coordinate frames were defined for the bone meshes (Wu et al. 2002) and marker coordinates, based on the radio opaque markers in the MR images, were expressed in the respective segmental coordinate frames. Next, the muscle points of all hip and knee actuating muscles were identified in the MR images (Scheys et al. 2006). The number of muscle points were defined similar to the generic model. The muscle points of all distal tibia and foot muscles as well as the ankle joint center were the same in the scaled generic and MRI models.