Tibial Shaft Fractures: A Biomechanical and Clinical Approach

Among the problems associated with the use of tibial functional bracing for the management of tibial shaft fractures, are post-fracture ankle stiffness and the duration of immobilisation. This study was undertaken to investigate in detail these two problems. It involved the design and assessment of a new type of brace called the 2 in 1 functional brace. The study was designed in 3 parts. Part 1 deals with the problem of clarifying the biomechanical function of the brace. It led to the development of a method for estimating the three dimensional forces and moments carried by the limb-brace complex at the level of the fracture. For this five volunteer patients, treated with a 2 in 1 brace for tibial shaft fractures, were each tested on 3 separate occasions. This study led to the conclusion that the brace is neither an off-loading, nor an anti-buckling device, but functions with a combination of these two mechanisms. The data also highlighted the importance of the removable "foot-piece" in the design of the brace for optimum healing of tibial fractures. The information obtained allowed rationalisation of the new design. Part 2 of the study concentrated on the problem of determining the optimum duration of immobilisation in the brace. A non-invasive method of assessing healing by measurement of fracture stiffness was developed. This method gave encouraging results and it was decided to computerise the system. The efficacy of the system was assessed clinically in a trial on 10 patients. The results were encouraging and it is recommended that the system be tested in a larger controlled trial, before its routine use. Part 3 of the study tested the new design of brace in a clinical trial on 80 patients. The trial was conducted to test the efficacy of the design in a clinical environment and to assess its effect on the stiffness of the ankle and sub-talar joints following fracture healing. The brace gave good clinical results with a mean healing time of 97.5 days in the series. The ranges of lower limb joint motion were found to be near normal at a mean follow-up of 16 months, indicating the success of the design in decreasing the incidence of post-fracture ankle and sub-talar joint stiffness. The conclusions from the study suggest that a controlled trial is justified to compare the efficacy of the "2 in 1 brace" against other methods of managing tibial shaft fractures. The data from this series showed that the nature (simple or open) of the fracture, axial stability of the fracture, fracture fragment apposition, treatment modality and time of brace application did affect the outcome of fracture healing

Biomechanics

Biomechanics is a vast discipline within the field of Biomedical Engineering. It explores the underlying mechanics of how biological and physiological systems move. It encompasses important clinical applications to address questions related to medicine using engineering mechanics principles. Biomechanics includes interdisciplinary concepts from engineers, physicians, therapists, biologists, physicists, and mathematicians. Through their collaborative efforts, biomechanics research is ever changing and expanding, explaining new mechanisms and principles for dynamic human systems. Biomechanics is used to describe how the human body moves, walks, and breathes, in addition to how it responds to injury and rehabilitation. Advanced biomechanical modeling methods, such as inverse dynamics, finite element analysis, and musculoskeletal modeling are used to simulate and investigate human situations in regard to movement and injury. Biomechanical technologies are progressing to answer contemporary medical questions. The future of biomechanics is dependent on interdisciplinary research efforts and the education of tomorrow’s scientists

Use of stance control knee-ankle-foot orthoses : a review of the literature

The use of stance control orthotic knee joints are becoming increasingly popular as unlike locked knee-ankle-foot orthoses, these joints allow the limb to swing freely in swing phase while providing stance phase stability, thus aiming to promote a more physiological and energy efficient gait. It is of paramount importance that all aspects of this technology is monitored and evaluated as the demand for evidence based practice and cost effective rehabilitation increases. A robust and thorough literature review was conducted to retrieve all articles which evaluated the use of stance control orthotic knee joints. All relevant databases were searched, including The Knowledge Network, ProQuest, Web of Knowledge, RECAL Legacy, PubMed and Engineering Village. Papers were selected for review if they addressed the use and effectiveness of commercially available stance control orthotic knee joints and included participant(s) trialling the SCKAFO. A total of 11 publications were reviewed and the following questions were developed and answered according to the best available evidence: 1. The effect SCKAFO (stance control knee-ankle-foot orthoses) systems have on kinetic and kinematic gait parameters 2. The effect SCKAFO systems have on the temporal and spatial parameters of gait 3. The effect SCKAFO systems have on the cardiopulmonary and metabolic cost of walking. 4. The effect SCKAFO systems have on muscle power/generation 5. Patient’s perceptions/ compliance of SCKAFO systems Although current research is limited and lacks in methodological quality the evidence available does, on a whole, indicate a positive benefit in the use of SCKAFOs. This is with respect to increased knee flexion during swing phase resulting in sufficient ground clearance, decreased compensatory movements to facilitate swing phase clearance and improved temporal and spatial gait parameters. With the right methodological approach, the benefits of using a SCKAFO system can be evidenced and the research more effectively converted into clinical practice

The effect of prefabricated wrist-hand orthoses on performing activities of daily living

Wrist-hand orthoses (WHOs) are commonly prescribed to manage the functional deficit associated with the wrist as a result of rheumatoid changes. The common presentation of the wrist is one of flexion and radial deviation with ulnar deviation of the fingers. This wrist position Results in altered biomechanics compromising hand function during activities of daily living (ADL). A paucity of evidence exists which suggests that improvements in ADL with WHO use are very task specific. Using normal subjects, and thus in the absence of pain as a limiting factor, the impact of ten WHOs on performing five ADLs tasks was investigated. The tasks were selected to represent common grip patterns and tests were performed with and without WHOs by right-handed, females, aged 20-50 years over a ten week period. The time taken to complete each task was recorded and a wrist goniometer, elbow goniometer and a forearm torsiometer were used to measure joint motion. Results show that, although orthoses may restrict the motion required to perform a task, participants do not use the full range of motion which the orthoses permit. The altered wrist position measured may be attributable to a modified method of performing the task or to a necessary change in grip pattern, resulting in an increased time in task performance. The effect of WHO use on ADL is task specific and may initially impede function. This could have an effect on WHO compliance if there appears to be no immediate benefits. This orthotic effect may be related to restriction of wrist motion or an inability to achieve the necessary grip patterns due to the designs of the orthoses

The effect of prefabricated wrist-hand orthoses on grip strength

Prefabricated wrist-hand orthoses (WHOs) are commonly prescribed to manage the functional deficit and compromised grip strength as a result of rheumatoid changes. It is thought that an orthosis which improves wrist extension, reduces synovitis and increases the mechanical advantage of the flexor muscles will improve hand function. Previous studies report an initial reduction in grip strength with WHO use which may increase following prolonged use. Using normal subjects, and thus in the absence of pain as a limiting factor, the impact of ten WHOs on grip strength was measured using a Jamar dynamometer. Tests were performed with and without WHOs by right-handed, female subjects, aged 20-50 years over a ten week period. During each test, a wrist goniometer and a forearm torsiometer were used to measure wrist joint position when maximum grip strength was achieved. The majority of participants achieved maximum grip strength with no orthosis at 30° extension. All the orthoses reduced initial grip strength but surprisingly the restriction of wrist extension did not appear to contribute in a significant way to this. Reduction in grip must therefore also be attributable to WHO design characteristics or the quality of fit. The authors recognize the need for research into the long term effect of WHOs on grip strength. However if grip is initially adversely affected, patients may be unlikely to persevere with treatment thereby negating all therapeutic benefits. In studies investigating patient opinions on WHO use, it was a stable wrist rather than a stronger grip reported to have facilitated task performance. This may explain why orthoses that interfere with maximum grip strength can improve functional task performance. Therefore while it is important to measure grip strength, it is only one factor to be considered when evaluating the efficacy of WHOs

Tibiofemoral contact areas and contact forces in healthy and osteoarthritic subjects

Knee osteoarthritis (OA) is a common type of musculoskeletal disability, particularly among the elderly population. Excessive contact forces on the joint, or on specific parts of it (e.g. medial compartment), or shifting the contact forces to the regions that are not adapted to loading are the mechanical factors which can trigger OA. Therefore, it is crucial to understand the differences of these mechanical parameters in OA subjects with respect to the healthy ones. The aim of this study was to the compare the tibiofemoral contact point locations and the contact forces in OA and healthy subjects and examine if the contact point locations influence the contact force sharing in both groups. The tibiofemoral contact point locations in 10 healthy and 9 osteoarthritic (OA) subjects during a weight-bearing squat was measured using stand-alone biplane X-ray images. A manual multiple view 3D reconstruction/registration method was used to reconstruct the bones in different squat postures from the biplane radiographs and a weighted center of bone-to-bone proximity was applied to estimate the contact point locations. Results showed that the contact point locations of the OA subjects on the medial and lateral compartments were shifted medially compared to the healthy group. In both groups, contact points showed a posterior excursion on the medial compartment and posterior and lateral excursions on the lateral compartment, where the excursion on the lateral compartment was smaller in OA subjects. To estimate the tibiofemoral contact forces, a custom musculoskeletal model of the lower limb with the integration of personalized contact points was provided to estimate contact forces at subject-specific contact points during gait. The tibiofemoral joint model was reformulated so that the constraints of the joint were formed by the superimposition of the personalized tibial and femoral contact points. The suggested constraints are adaptable to the contact points derived from the classical joint models or those experimentally measured from the 3D imaging techniques. The estimated contact forces estimated using the personalized contact points were compared to those estimated from the classical knee joint models in 10 healthy subjects. Results showed that the impact of personalization of contact points on the contact forces is very variable among the subjects and the shifts of the contact points alone cannot predict the distribution of contact forces in the medial and lateral compartments. To evaluate the contribution of contact point locations to the contact force distribution the musculoskeletal model of the lower limb with the personalized contact point trajectories were used to estimate the medial and lateral contact forces of 10 healthy and 12 OA subjects. The contact forces in healthy subjects were slightly higher compared to the OA subjects. However, no statistically significant difference was noted in the peaks of medial, lateral or total contact forces. The regression analysis results showed that the knee adduction moment and knee flexion moment were the main contributors to the medial-to-total contact force ratio (MR) in both groups. From the components of the contact point location, the medial contact point location in medial/lateral direction had a significant contribution to the MR in OA subjects. This study showed that the mechanism of load distribution was different in OA joints where contrary to the healthy ones the contact point location was a significant contributor to MR. In addition, the knee flexion moment had a higher contribution to MR than the knee adduction moment whereas in healthy subjects the knee adduction moment was the most significant contributor to the MR

A virtual environment for the modelling, simulation and manufacturing of orthopaedic devices

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The objective of this work is to investigate whether the game physics based modelling is accurate enough to be used in modelling the motion of the human body, in particular musculoskeletal motion. Hitherto, the implementation of game physics in the medical field focused only on anatomical representation for education and training purposes. Introducing gaming platforms and physics engines into orthopaedics applications will help to overcome several difficulties encountered in the modelling of articular joints. Implementing a physics engine (PhysX), which is mainly designed for video games, handles intensive computations in optimized ways at an interactive speed. In this study, the capabilities of the physics engine (PhysX) and gaming platform for modelling and simulating articular joints are evaluated. First, a preliminary validation is carried out for mechanical systems with analytical solutions, before constructing the musculoskeletal model to evaluate the consistency of gaming platforms. The developed musculoskeletal model deals with the human joint as an unconstrained system with 6 DOF which is not available with other joint modeller. The model articulation is driven by contact surfaces and the stiffness of surrounding tissues. A number of contributions, such as contact modelling and muscle wrapping, have been made in this research to overcome some existing challenges in joint modelling. Using muscle segmentation, the proposed technique effectively handles the problem of muscle wrapping, a major concern for many; thus the shortest path and line of action are no longer problematic. Collision behaviour has also shown a stable response for colliding as well as resting objects, provided that it is based on the principles of surface properties and the conservation of linear and angular momentums. The precision of collision detection and response are within an acceptable tolerance controllable by varying the mesh density. An image based analysis system is developed in this thesis, mainly in order to validate the proposed physics based modelling solution. This minimally invasive method is based on the analysis of marker positions located at bony positions with minimal skin movement. The image based system overcomes several challenges associated with the currently existing methods, such as inaccuracy, complication, impracticability and cost. The analysis part of this research has considered the elbow joint as a case study to investigate and validate the proposed physics based model. Beside the interactive 3D simulation, the obtained results are validated by comparing them with the image based system developed within the current research to investigate joint kinematics and laxity and also with published material, MJM and results from experiments performed at the Brunel Orthopaedic Research and Learning Centre. The proposed modelling shows the advantageous speed, reliability and flexibility of the proposed model. It is shown that the gaming platform and physics engine provide a viable solution to human musculoskeletal modelling. Finally, this thesis considers an extended implementation of the proposed platform for testing and assessing the design of custom-made implants, to enhance joint performance. The developed simulation software is expected to give indicative results as well as testing different types of prosthetic implant. Design parameterization and sensitivity analysis for geometrical features are discussed. Thus, an integrated environment is proposed to link the real-time simulation software with a manufacturing environment so as to assist the production of patient specific implants by rapid manufacturing

Injury and Skeletal Biomechanics

This book covers many aspects of Injury and Skeletal Biomechanics. As the title represents, the aspects of force, motion, kinetics, kinematics, deformation, stress and strain are examined in a range of topics such as human muscles and skeleton, gait, injury and risk assessment under given situations. Topics range from image processing to articular cartilage biomechanical behavior, gait behavior under different scenarios, and training, to musculoskeletal and injury biomechanics modeling and risk assessment to motion preservation. This book, together with "Human Musculoskeletal Biomechanics", is available for free download to students and instructors who may find it suitable to develop new graduate level courses and undergraduate teaching in biomechanics