Biomechanics of hallux valgus and evaluation of interventions

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Biomechanics of hallux valgus and evaluation of interventions

 

Author: Wong, Wai Chi
Title: Biomechanics of hallux valgus and evaluation of interventions
Degree: Ph.D.
Year: 2014
Subject: Hallux valgus.
Hong Kong Polytechnic University -- Dissertations
Department: Interdisciplinary Division of Biomedical Engineering
Pages: xxxii, 276 pages : illustrations ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2762951
URI: http://theses.lib.polyu.edu.hk/handle/200/7750
Abstract: Hallux valgus has been reported as one of the most common foot problems and is associated with age, gender and footwear. The disease imposes heavy economic and social burden on hospital expenditure, pain-suffering and manpower lost. Additionally, Hallux valgus also imposes risk of falling on elderly patients and additional risk to patients with diabetic or neuropathic feet. Different surgical and conservative treatments have been suggested. These protocols have been modified or optimized. Some physicians and researchers suggested decision-making pathway to determine the treatment to be conveyed. However, these protocols were qualitative and empirical. Although identifying the pathogenesis of hallux valgus has long been conducted, the mechanism and initialization of the pathology have not come into clear conclusion and consensus. Pathoanatomy, pathomechanics and hypermobility studies were conducted to evaluate the features of hallux valgus. Some biomechanical studies also aimed to quantify the characteristics of hallux valgus. Hallux valgus is not well-understood and remains on the research bench. There were cases of failures, complications and recurrence of interventions. Physicians are heading for better protocols and methods to improve the interventions. The objective of this study was to construct a biomechanical platform to examine the pathomechanism of hallux valgus and evaluate its interventions. The research findings enhanced understandings of hallux valgus and thus would improve treatment outcome in the long run. This biomechanical study included 3 components involving computational simulation (finite element analysis), physical experiment (to provide input to simulation and validation), and clinical study.
Finite element foot model was constructed. This simulation platform was validated with physical experiments, including motion analysis, pedobarographic and cadaveric study. The data collected by the motion analysis system were also input into the simulation platform for finite element analysis. The simulation of hallux valgus initialization was mimicked by ligament laxity. The influence of ligament laxity on joint loading was investigated. The hypermobile foot (represented by the influence of ligament laxity) showed increase of metatarsocuneiform and metatarsophalangeal joint forces in all directions comparing with the normal foot. During the push-off phase, the joint forces of the metatarsocuneiform joint and the metatarsophalangeal joint were 27% and 10% larger than that of the normal foot. The increase could be due to the impairment of shock absorption. It could be also due to the extended obligation of the first ray to maintain stability upon ligament laxity. The abrupt change of the metatarsocuneiform joint force in mediolateral direction provided additional evidence on the relationship between hypermobile foot and metatarsus primus varus. The higher joint loading also suggested that foot with hypermobility could predispose risk of arthritis and joint incongruence. The simulation was continued on the evaluation of metatarsocuneiform arthrodesis, one of the hallux valgus interventions, which was reported with high failure rate (Coughlin & Mann, 2012). The objective of this simulation was to study the stress distribution of the bone graft used in the arthrodesis procedure, and thus evaluate rather inter-fragmentary compression could be achieved. The result of the simulation showed that compressive stress was ensured at the superior portion of the bone graft and tensile stress happened on the inferior side during stance. The magnitude of the stress increased drastically with about 20% of the graft volume exceeded 4MPa upon the initial push-off. The graft used for arthrodesis might absorb the physiological motion by sustaining bending stress that attributed to difficulty in fusion. The traditional metatarsocuneiform arthrodesis might not guarantee inter-fragmentary compression. Parametric study on the resection angle and the graft stiffness can be conducted to study possible improvement on the procedure. A modified soft tissue procedure for hallux valgus (syndesmosis procedure) was evaluated. A retrospective study on the patients pre-operatively and 2-year follow-up was conducted. The evaluation included questionnaires, radiographic and plantar pressure evaluation. The objective of this study was to evaluate the clinical satisfactoriness as well as the biomechanical outcome of this surgical procedure. The retrospective study demonstrated good clinical, radiological outcome, and improved load-bearing under the hallux and the first ray in the plantar pressure study. This study presented a comprehensive biomechanical platform starting with the research on the biomechanics of hallux valgus using a validated computational model. The computational model was then used to study the interventions of hallux valgus. Evaluation of intervention was also carried out in the clinical sector, based on clinical, radiological and biomechanical measurements.

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