The specialist, thanks to the various exams that he can perform with the pressure platform, has the possibility to study the distribution of plantar pressures, the foot load and any diseases affecting the musculoskeletal system. Moreover, it is possible to detect pathologies associated to diabetes and diseases caused by obesity, involving knees and feet.
What we mainly study is the movement of the centre of pressure, where CoP (Centre of Pressure) means the centroid of all external forces acting on the plantar surface.
The CoP trend allows measuring the neuromuscular control in a static position and during the gait to know the balance control of the subject, the functionalities of the foot and the effectiveness of the applied treatment.
The pressure platform allows performing three types of analysis:
- Static exam
- Dynamic exam
- Stabilometric exam.
The static analysis is used to assess the plantar support and to identify the major or minor load areas, through a colour scale going from red to blue, when the subject is in a static position. With this exam, we record the load percentage distributed on both feet and the anterior and posterior load. Furthermore, the feet supporting surface is provided, information needed to assess the symmetry between the two feet and the degree of clawing and flatness.
During the exam, the patient is placed in a bipodalic position on the sensitive surface of the pressure platform with the heels as much aligned as possible with each other and appearing at the bottom of the screen.
The image obtained will be the average of the data recorded during the exam.
Having components such as video cameras or webcams available, it is possible to capture a picture of the patient during the exam and to take free or guided measurements on the image itself applying some markers on the anatomical landmarks.
Therefore, with the static exam, we will study the pressures exchanged between foot and ground, the body weight and overload points distribution, the patient’s ability to hold a balance position.
With the dynamic exam, the gait and the kinematic characteristics of movement are studied.
The patient is asked to walk along the platform from an end to the other: before starting the acquisition, it is advisable to ask the patient to make a few passages, to become familiar with the platform, avoiding the outpatient phenomenon that disturbs the natural development of gait.
The main parameters studied during the dynamic analysis are:
- Step and half-step length;
- Step cycle duration;
- Duration of the support, swing and double support phases;
- Step frequency and speed.
The development of the step can be evaluated by studying, frame by frame, the Gait Line. For each phase we will have information concerning:
- the foot pressures during each step,
- the position of the body centre of gravity,
- the momentary value and the trend of the maximum pressure points,
- the surface value,
- the momentary value of the average pressure and of the load in the foot under exam.
By analysing these data, for the specialist, it will be easier to express a diagnosis, for example recognising quickly the clawing or flattening, pronation or supination of the foot.
If the subject suffers from a pathology, the Gait Line will be different as compared to normality.
With this exam, it is possible to view the different step phases, with their respective duration and load percentage:
- ICP: Initial Contact Phase (it begins with the first foot contact with the ground and ends with the first metatarsal contact).
- FFCP: ForeFoot Contact Phase (the phase after the ICP, that ends with the complete contact of the metatarsal heads with the ground).
- FFP: Foot Flat Phase (it begins at the end of the FFCP and ends with the heel lifting off the ground).
- FFPOP: ForeFoot Push-Off Phase (it begins with the heel that lifts off the ground and ends when the foot isn’t in contact with the ground anymore).
Thanks to the dynamic analysis it is possible to study the trends over time of surface, of the minimum and average pressure and of the load, both for the footprint under examination and for the various foot sections.
In the dynamic analysis too, having video cameras or webcams available, it is possible to capture videos of the patient during the exam, to make assessments and measurements, both free and guided, applying some markers on the anatomical landmarks.
Another type of analysis we can do with the pressure platform is the posturographic or stabilometric exam, by which the patient’s balance condition are assessed, studying the position and trend of the centre of pressure.
For this analysis, the subject is placed on the acquiring pressure platform, in a static position that varies according to the type of test to perform. Among the several acquisition protocols, the most used are:
- Romberg Test: a bipodalic acquisition in the upright position both with open and closed eyes, to know, through the Romberg index, if sight affects the subject’s postural control.
- Monopodalic Test: a monopodalic acquisition with open eyes and one with closed eyes are made for each foot.
- Cervical Interference: it consists of two tests, one with flexed and one with the upright head.
- Stomatognathic Interference: it consists of two tests; one with the patient wearing a bite that prevents the usual dental occlusion and the other without wearing it, to understand if the teeth position interferes with the posture.
Visually, from the posturographic exam we will obtain:
- The Status-kinesigram: representing the movement of the CoP in the XY plane and the confidence ellipse, where the 90% of the recorded points are contained.
- The Stabilogram: it represents the trend of the changes of the CoP over time, both in the antero-posterior and in the latero-lateral direction.
By analysing with an appropriate software the data recorded during the exam, it is possible to extract the parameters that characterise the centre of pressure trend over time.
- The sway length, expressed in mm, representing the global path of CoP performed during the examination;
- The ellipse surface, expressed in cm2, that contains the 90% of the sway points;
- Average X and Y coordinates, expressed in mm, representing the average values of the CoP coordinates in antero-posterior and latero-lateral direction;
- L/S Ratio: that is a correlation function between the sway length and the ellipse surface;
- The average speed, expressed in mm/s, which gives the average value of the CoP movements;
- The Fast Fourier Transform (FFT), that allows evaluating the centre of pressure oscillations in the various frequencies.
For each stabilometric exam, it is possible to carry out up to six tests, comparable with each other and with the normal values.
The footprints’ views in the different analysis types are:
- Points: dots of different dimension and colour depending on the pressure applied;
- Numerical: with numerical values from 0 to 9 depending on the pressure value;
- Levels: with the three colours, red, green and blue for the heaviest, intermediate and minor load points respectively;
- Hires: with a point high resolution;
- 3D: three-dimensional reconstruction of the support.
