L. Jones

Objective functional assessment of total hip arthroplasty following two common surgical approaches: the posterior and direct lateral approaches.

Abstract Despite the high number of total hip arthroplasty (THA) procedures performed each year, there is no common consensus on the best surgical approach. Gait is known to improve following THA although it does not return to what is typically quantified as normal, and surgical approach is believed to be a contributing factor. The current study evaluates post-operative hip function and provides an objective assessment following two common surgical approaches: the McFarland—Osborne direct lateral and the southern posterior. Faced with the common problem of providing an objective comparison from the wealth of data collected using motion analysis techniques, the current study investigates the application of an objective classification tool to provide information on the effectiveness of each surgery and to differentiate between the characteristics of hip function following the two approaches. Seven inputs for the classifier were determined through statistical analysis of the biomechanical data. The posterior approach group exhibited greater characteristics of non-pathological gait and displayed a greater range of functional ability as compared with the lateral approach cohort. The classification tool has proved to be successful in characterizing non-pathological and THA function but was insufficient in distinguishing between the two surgical cohorts.

Classification of osteoarthritic and normal knee function using three-dimensional motion analysis and the Dempster-Shafer theory of evidence

In this paper, a novel object classification method is introduced and developed within a biomechanical study of human knee function in which subjects are classified to one of two groups: subjects with osteoarthritic (OA) and normal (NL) knee function. Knee-function characteristics are collected using a three-dimensional motion-analysis technique. The classification method transforms these characteristics into sets of three belief values: a level of belief that a subject has OA knee function, a level of belief that a subject has NL knee function, and an associated level of uncertainty. The evidence from each characteristic is then combined into a final set of belief values, which is used to classify subjects. The final belief values are subsequently represented on a simplex plot, which enables the classification of a subject to be represented visually. The control parameters, which are intrinsic to the classification method, can be chosen by an expert or by an optimization approach. Using a leave-one-out cross-validation approach, the classification accuracy of the proposed method is shown to compare favorably with that of a well-established classifier-linear discriminant analysis. Overall, this study introduces a visual tool that can be used to support orthopaedic surgeons when making clinical decisions.

Reduction, classification and ranking of motion analysis data: an application to osteoarthritic and normal knee function data

There are certain major obstac les to using motion analysis as an aid to clinical decision making. These include: the difficulty in comprehending large amounts of both corroborating and conflicting information; the subjectivity of data interpretation; the need for visualization; and the quantitative comparison of temporal waveform data. This paper seeks to overcome these obstacles by applying a hybrid approach to the analysis of motion analysis data using principal component analysis (PCA), the Dempster–Shafer (DS) theory of evidence and simplex plots. Specifically, the approach is used to characterise the differences between osteoarthritic (OA) and normal (NL) knee function data and to produce a hierarchy of those variables that are most discriminatory in the classification process. Comparisons of the results obtained with the hybrid approach are made with results from artificial neural network analyses.

An objective tool for assessing the outcome of total knee replacement surgery

The need for an objective tool to assess the outcome of total knee replacement (TKR) surgery is widely recognized. This study investigates the potential of an objective diagnostic tool for assessing the outcome of TKR surgery based on motion analysis techniques. The diagnostic tool has two main elements: collection of data using motion analysis, and the assessment of knee function using a classifier that is based around the Dempster—Shafer theory of evidence. The tool was used to analyse the knee function of nine TKR subjects pre-operatively and at three stages post-operatively. Using important measurable characteristics of the knee, the tool was able to establish the level of benefit achieved by surgery and to enable a comparison of subjects. No subject recovered normal knee function following TKR surgery. This has important implications for knee implant designs.

Investigating the effect of surgical approach on the outcome of total hip arthroplasty

Hip replacement is a common procedure known to improve quality of life and gait. However postoperatively, gait does not return to normal and it is thought that differing surgical methods may contribute to the extent to which normal gait is achieved. The two main surgical approaches involve either posterior or lateral incisions; affecting different muscular structures surrounding the hip joint. These two approaches have been compared to investigate their effects on postoperative gait. A Dempster-Shafer (DS) classifier was developed to identity the important kinetic and kinematic variables and classify the two groups of patients. 3D motion analysis was performed postoperatively for walking and Trendelenburg tests using QTM Software, Proreflex cameras (Qualisys, Sweden), and Bertec force platforms (Bertec Corporation). Motion data was analysed using a Visual3D 3.34 (C-Motion Inc) biomechanical model of the lower limbs. Joint rotations were defined using a Cardan/Euler sequence and inverse dynamic analysis was used to calculate internal joint moments. This model was subsequently used for 3D kinematic and kinetic analysis. Paired and independent-sample t-tests (SPSS 12.0.2) were applied to the results obtained for 10 subjects to compare: (i) the two approaches and (ii) the operated and non operated leg. This preliminary analysis highlighted several salient parameters including frontal moments, pelvic obliquity and range of motion of the hip joint and pelvis. The gait data from 35 subjects was then analysed using a modified DS based classifier, developed previously to characterise normal and osteoarthritic knee function [Jones 2006]. The value of this generic classifier was explored in terms of providing an objective and visual indicator of postoperative THA recovery and surgical efficacy following lateral and posterior approaches.