Can the F-Scan in-shoe pressure system be combined with the GAITRite® temporal and spatial parameter-recording walkway as a cost-effective alternative in clinical gait analysis? A validation study

Participants

A convenience sample of twenty-six participants was recruited for the study from the population of a university in the UK. Ethical approval for the study was obtained from the School Research Ethics Panel at the host university.

To enter the study, participants were required to be over 18 years old, have a self-reported UK shoe size between the range of 5 and 10 and own a pair of training shoes with a secure fastening that they were prepared to wear during the study. This range of shoe sizes was chosen to capture the most commonly observed shoe sizes worn by men and women in the UK. Participants were unable to enter the study if they had a current injury, active foot disease, difficulties with balance, or depth perception.

Data collection

Data collection took place in a gait analysis laboratory using an F-Scan Research 7.50 × and a GAITRite® walkway. The F-Scan equipment consisted of a data logger attached to the waist of the participant and two ankle receiver units linked to the in-shoe sensor insoles Prior to testing, each participant walked for five minutes whilst wearing the F-Scan equipment to allow the participant to become familiar with the device and to establish their usual walking speed. This reduced the possibility of inaccurate pressure readings being recorded from atypical gait patterns [12]. Following research recommendations [13], new F-Scan insoles were introduced after every five uses to avoid damage to the sensors housed within the in-shoe sensor insoles. In accordance with the F-Scan manual, walk calibration was performed automatically using the participants weight whilst wearing the equipment [14].

The GAITRite® walkway measured 6 m in length, 60 cm in active width (89 cm overall) and 5 mm in thickness. The walkway was not connected to the software as this was not required for the study.

Steps taken during gait initiation and gait termination are not representative of mid-gait walking steps, whereas the third and fifth steps have been found to provide an accurate representation of ‘normal’ walking patterns [15]. Therefore, a starting line was placed 30 cm in front of the GAITRite® walkway to avoid gait initiation steps and ensure the third and fifth steps were captured on the walkway. An additional start line was placed adjacent to that described above to create an adjacent walkway on the laboratory floor (Fig. 1).

Fig. 1figure 1

The F-Scan data logger recording time was programmed at 8 s, providing sufficient time for the participants to walk the length of the walkway based upon an average cadence of 100 steps/minute [16]. This equates to approximately 13 steps being taken in the eight second recording.

The participants were asked to walk at their normal pace during the study. Participants are likely to take a different number of steps over the test distance due to varying walking speeds. Whilst research has shown that the third to fifth steps are most reflective of ‘normal’ walking in relation to pressure and force [4, 15], the selection of a single step was believed to be less representative of habitual walking than an average of steps. Therefore, an average calculation of plantar pressure recordings from the third, fifth and seventh steps was taken for each participant. For participants who had started walking with their right foot, this would equate to the second, third and fourth ground contact with the right foot. To ensure data from the same foot was collected, participants were asked to start walking with the same foot for each test condition.

Analysis was conducted at the 1st and 2nd metatarsophalangeal joints (MTPJs) for all participants as these are commonly investigated in foot pressure analysis particularly in diabetic care. According to research 33–35% of foot ulcerations in diabetic patients occur at the 1st MTPJ joint [17].

Once the 1st and 2nd MTPJs on the plantar pressure recording were located, a 2 cm object box was placed in the area. This was completed manually by the researcher, a qualified podiatrist. A second podiatrist then assessed the placement of the object box to promote reliability.

To calculate the pressure at this location, the average contact pressure was calculated over the stance phase period. Contact pressure provides an understanding of the pressure acting on an anatomical structure whereas peak pressure is often used to establish the effectiveness of cushioned interventions, such as polyurethane materials [4]. Additionally, contact pressure has been found to demonstrate high retest reliability in all areas of the foot [9].

Following the five-minute ‘equipment familiarity’ period, each participant was asked to walk from the start line across the laboratory floor to the end of the room. They were then asked to walk from the start line to the end of the room on the GAITRite® walkway. This procedure was repeated three times on each surface to account for learning and fatigue effects [18, 19].

Statistical analysis

The sample was summarised descriptively using IBM SPSS statistical software package Version 28.0.1.1. The extent and nature of any missing data was assessed. Complete case analysis was conducted following verification of low proportion of data shown to be missing completely at random. Agreement between plantar pressure recorded by the walks on the standard surface and the GAITRite® walkway was assessed using the Bland–Altman method for both joints [20], using mean values from all walks of all participants who successfully completed all required walks. The intraclass correlation coefficient (the proportion of variability between observations due to differences between walkways) and Lin’s concordance correlation coefficient [21] (a measure of the departure of the line of best fit from a 45° line through the origin) were calculated for both joints as indices of reliability.

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