The assessment of the dynamics of changes in torques of redressing and derotating forces acting on the spine during active kyphosis-deepening exercises in the Dynamic Individual Stimulation and Control For Spine device (DISC4SPINE, D4S)

The measurements are taken during 6 successive therapeutic visits of each patient, each containing 5 repetition sets. A repetition set contained applying pressure on the heads 20 times for 8 seconds. For each patient the resistance head is in the RT – right top setting, individually adjusted for their needs. The study is carried out using the D4S system of interactive spine and posture rehabilitation in the aspect of dynamic, personalised stimulation (Dynamic Individual Stimulation and Control For Spine and Posture Interactive Rehabilitation, Disc4Spine). The basic function of the D4S system is diagnosing and constant monitoring of the therapy, correcting defective posture in the sagittal plane, functional correction during everyday activities, stabilisation of corrected body posture, and patient education. The D4S system allows for a quick and precise diagnosis of a postural defect, determining its degree, and then adjusting the therapy for the patient’s needs and constant monitoring of changes. It is made of four modules: (1) physiotherapy module, (2) actuator module, (3) gamification module, and (4) diagnostic and monitoring module. In this study modules 1, 2 and 4 were used. The physiotherapy module is a station for advanced exercises based on the Pressio concept, performed in a four-point kneeling position. It allows for conservative treatment and prevention of scoliosis using active involvement of the patient’s own force. The arches of deformed curvature are acted on in three planes at the same time. The crucial concept here is the priority of derotation of vertebrae before posture correction, i.e. taking into consideration the fact that a change in the position of vertebral bodies in the transverse plane results in the change of the chest shape, leading to deeper deformation. The second principle applied in the PRESSIO method refers to the manner and direction of the derotating and redressing forces which must be opposite to the direction of the inducing forces. The patient’s position in the cage for exercises in four-point kneeling is stabilised by special brackets for the shoulder girdle and for pelvis. The physiotherapist who is responsible for the course of the whole therapeutic process sets the resistance elements on the apexes of spine curvatures. Depending on the type of deforming curvature the heads are set in different configurations. Then, after appropriate securing of the patient in the D4S module, the patient is asked to perform an exercise known as a cat’s back stretch. At this time the resistance elements correct the deformation in three planes (leading to derotation and correction). The next module in the Disc4Spine system, the actuator module, is equipped with two resistance elements (heads) which primarily work vertically down, causing derotation of vertebral bodies and then, in the phase of the greatest derotation, make a slide to the side putting the spine in the hypercorrective position. Each of the heads which is a part of the module, is equipped with sensors for constant measurement of forces generated by the patient while performing the exercises. For the purpose of this study the MediLogic system was used with a set of sensors recording the signal of force during the therapy placed on each of the two resistance elements. The third component used in the presented study is a diagnostic and monitoring module which enables observation of patient’s physiological functions during the therapeutic exercises. To this end, for the purpose of this study, a medically certified wristband Empatica E4 device was proposed and used. It is worn by the participant on the wrist of the non-dominant hand according to the manufacturers recommendations. The wristband is wearing only during therapeutic sessions. The device makes it possible to record photoplethysmographic signal, body temperature and electrodermal skin activity which allows for a comprehensive evaluation of the patient’s condition during the rehabilitation. Additionally, E4 is equipped in three-axis accelerometer which monitors the movement of the studied person. The pressure force of the head on the torso will be assessed; the sensor is located on the head. The heads are placed at the top of the arc of curvature, approximately 2 cm from the spinous process. The patient is properly positioned and secured in a supported kneeling position with the shoulder girdle and pelvis immobilized by locks and the actuator modules are correctly set. Performs the "cat's back" exercise by pressing the resistance heads with maximum strength. After an appropriate warm-up, the patient was asked to perform a 4-minute session of the so-called "cat's backs", pressing the resisting elements of the heads with maximum own force for 8 seconds each. Each session was separated by a 4-second break. The moments of force released during the exercise are initially directed vertically down and after exceeding the individually selected and regulated load, they glide sideways. The patient presses the heads with his torso with maximum own force until side sliding occurs. The transition of the head to side slide is individually adapted to the patient's capabilities through the selected resistance of the head, set at the beginning of the session. The intervention is assessed with the SWAT strategy through constant contact with the patient (interview with the patient assessing well-being, information on the methods and course of measurement, information on the possibility of interrupting the session by the patient at any time during its duration, information on how to monitor the patient during the session, observation of the patient, monitoring the value of generated forces), monitoring the range of forces, the spine line and the patient's behavior. The therapeutic visit includes a consent signed by the parent or legal guardian, a standard warm-up, and a therapeutic session in the Disc$Spine device. There will be 2 visits a week, 20 minutes each. The PRESSIO method is based on the theory of Robert Roaf emphasizing the importance of the rotational component of spine deformations and on propositions of Cotrel taking into account three-planar EDF action (elongation, derotation, flexion). In the PRESSIO method, the elongation component was replaced by pressing (pressio) on the structures of the apex of the deformation curvature, i.e. PDF (pressure, derotation, flexion) is proposed instead of EDF. The manner of pressing with pressure heads allows for a transfer of unfavorable loads from articular processes of the concave side of the curvature to vertebral bodies, which opens the possibility of restoring physiological spine curvatures in the period of biological plasticity of the bone system. In order to allow the exertion of force from a third point, two other points are stabilized by using a shoulder and hip block. Exercising using the Pressio method offers a possibility of three-planar action on two arches of deformation curvature at the same time by self-dosed and self-controlled: • correction in the frontal plane, • derotation in the transverse plane • kyphotisation (kyphosis deepening) in the sagittal plane. The therapy is used on an outpatient basis or as home treatment based on recommendations and follow-up visits. A patient stabilized in a kneeling position taking into account elongation, kyphotization and derotation, applies pressure to the therapeutic heads placed on the apex or apexes of the deformation curvatures. The pressure is applied by the patient's own strength which is a safety feature, preventing any damage to the soft tissue structures and bones. Maximum values of forces released by patients vary between individuals. The frequency and the number of repetitions is determined by the physiotherapist. For this study, the Medilogic® system (T&T Medilogic Medizintechnik GmbH, Germany) was used to measure patient response, with sensors that record the force signal during ongoing therapy placed in each of the two resistance elements independently. This system provides wireless data transmission. The actuator module was equipped with special MediLogic measurement sensors, recording the force in real-time at 32 Hz. After the recording, the sensor data was exported to .csv format files each time, independently for the right and left resistance elements.