Predicting the location of the hip joint centres, impact of age group and sex

Clinical gait analysis incorporating three-dimensional motion analysis plays a key role in planning surgical treatments in people with gait disability. The position of the Hip Joint Centre (HJC) within the pelvis is thus critical to ensure accurate data interpretation. The position of the HJC is determined from regression equations based on anthropometric measurements derived from relatively small datasets. Current equations do not take sex or age into account, even though pelvis shape is known to differ between sex, and gait analysis is performed in populations with wide range of age. Three dimensional images of 157 deceased individuals (37 children, 120 skeletally matured) were collected with computed tomography. The location of the HJC within the pelvis was determined and regression equations to locate the HJC were developed using various anthropometrics predictors. We determined if accuracy improved when age and sex were introduced as variables. Statistical analysis did not support differentiating the equations according to sex. We found that age only modestly improved accuracy. We propose a range of new regression equations, derived from the largest dataset collected for this purpose to date

The conventional gait model - success and limitations

The Conventional Gait Model (CGM) is a generic name for a family of closely related and very widely used biomechanical models for gait analysis. After describing its history, the core attributes of the model are described followed by evaluation of its strengths and weaknesses. An analysis of the current and future requirements for practical biomechanical models for clinical and other gait analysis purposes which have been rigorously calibrated suggests that the CGM is better suited for this purpose than any other currently available model. Modifications are required, however, and a number are proposed

An open source implementation of the Conventional Gait Model in Python

The Conventional Gait Model CGM has been a standard in clinical gait analysis since the 1990s. Well-known by its commercialisation as Plug-in Gait (PiG, Vicon, Oxford, UK), it is simple and widely understood facilitating discussion between biomechanists and clinicians. Most commercial manufacturers now provide some version of the model. Despite its common use there has been little development of the model since the 1990s perhaps because open source versions have not been available. None of these replicates fully the range of options that are used by different users. The first aim of this paper is thus to present an open source version of the CGM which fully replicates those options

Calculation of joint moments following foot contact across two force plates

This study aimed to quantify the effect of combining the measurements from force plates when a subject’s foot comes in contact with more than one force plate. A 3-Dimensional Gait Analysis (3DGA) was performed on a subject walking barefoot. Ten gait trials (good both) were captured where both subject’s feet hit a single force plate. Then 20 gait trials (two force plates) were captured where either the right or left subject’s foot was in contact with two force plates at a time. Kinematics were computed with VICON1 Plugin Gait and kinetics with a BodyLanguage1 (VICON, Oxford, UK) model that allowed the combination of force plate measurements. The kinetics traces from both sets of data were compared using variance component analysis. Results suggest that effects of how the moments were calculated were at most a third of those arising from stride to stride variability. This suggests that development of automated systems for determining foot contact coupled with arrays of more and smaller force plates than are commonly used might be useful to ensure the capture of good quality kinetic data in a wide range of patients

O 111 - accuracy of the conventional gait model : preliminary results

The Conventional Gait Model (CGM), distributed as Vicon Plugin gait (Vicon PiG) became a standard in the field of 3D Clinical Gait Analysis. Its reliability is assessed thought repeatability tests. On the other hand, accuracy of the CGM in terms of underlying bone motion has never been quantified. It’s all the more important CGM outputs might orientate a patient towards bone surgery. Thanks to a consensus, data from invasive approaches are available in open-access. They can serve as basis for model validation. This communication proposes to assess the knee kinematic accuracy of the CGM with fluoroscopic data during a gait cycle

The choice of hip regression equations has small effect on kinematic and kinetic outputs of the conventional gait model

The hip joint centre (HJC) regression equations used by the Conventional Gait Model (CGM) has been shown to provide inadequate results. The location of the HJC has benefited from a large research effort in recent years, and new regression equations have been proposed. Although the accuracy of the equations has been validated against medical imaging, the effects the new equations may have on kinematic and kinetic outputs are relatively unknown

Validation of 3-D freehand ultrasound for the determination of the hip joint centre

This paper describes the calibration process for 3-D free hand ultrasound (3-DUS). The Cambridge calibration technique was determined to produce the most repeatable and accurate results when determining the location of a reference object within a water bath. This note additionally validates 3-DUS as a potential measurement tool for the determination of the hip joint centre. It shows that 3-DUS can accurately determine the inter-HJC distance to within 4 � 2 mm. This indicates potential for 3-DUS to be used as a gold standard measurement tool in the identification of the hip joint centr

Optimal markers’ placement on the thorax for clinical gait analysis

Although, several thorax models have been proposed for clinical gait analysis, none has received widespread acceptance nor been subject to any extensive validation work, especially for the marker set to use. The aim of this study was thus to determine the optimal and minimal makers’ placement on the thorax for clinical gait analysis. Ten healthy subjects have performed a series of movements (arm, head, trunk) with large amplitude during walking. Reflective markers were taped on the thorax (C7, T2, T4, T6, T8, T10, T12, sternum, clavicles and ribs) and their 3D positions were captured with an opto-electronic system. Each combination of 3 markers has been tested. The global error of each model was computed with the estimated position of the markers considering the thorax segment as a solid segment. Two families of marker sets were identified with the lowest error. The first family was composed by two anterior and one posterior marker on the thorax (incisura jugularis (IJ), xiphoid process, and T8). The second family was composed by two posterior and one anterior maker (IJ, T2 and T8 or T10). Even, if these two families of marker sets presented a similar error for marker position, the angles obtained from these marker sets showed large differences especially for the axial rotation movement of the trunk (up to 40.1°). The optimal and minimal maker set identified with a variety of large movements of the trunk, head and arms was IJ, T2 and T8 or T10