The Clynx® PlatformFootnote 9, developed by Clynx® Health, represents an innovative gamification tool designed to enhance the rehabilitation experience for physiotherapy patients. Specifically crafted for musculoskeletal and neurological therapy, including applications in prevention, pre- and post-surgery, and chronic diseases, the platform is poised to revolutionize physiotherapy practices.

Comprising a patient-oriented Desktop Application and a specialized Clinical Portal for healthcare practitioners, the Clynx® Platform incorporates cutting-edge technology to guide patients through their exercises. The Desktop Application employs a 3D camera to provide real-time data, facilitating an engaging and interactive rehabilitation process. Simultaneously, it meticulously records session details, such as duration and repetitions, contributing to comprehensive patient progress tracking. The Clinical Portal serves as a dedicated platform for physiotherapists, allowing them to assess the adherence to treatment plans by patients. This centralized hub facilitates efficient management of patient profiles and session assessments, streamlining the healthcare professional’s workflow.

The current version of the Clynx® Platform qualifies as a medical device software, meeting the criteria for classification as a Class I medical device under Rule 11. This classification is attributed to the platform’s primary function, which is to perform therapy, distinguishing it from tools primarily designed for diagnostic or therapeutic decision-making. Notably, the platform does not monitor physiological processes or quantitatively measure anatomical or physiological parameters, aligning with Sub-Rule 11 c) [4, 5].

Fig. 4

Quantitative measurements report after session. Image obtained from Clynx® Health from a simulated patient data

Fig. 5

Intended purpose, which will be included in the Intended Use File in the new version of the Clynx® Platform’s TD. Image obtained from Clynx® Health

Clynx® is working on an upcoming version of the platform. This evolution aims to aid healthcare professionals by enabling the tracking of patient progress through kinetic parameters. The new Clinical Portal will further support management of patient data, treatment plans, and assessments. The new iteration of the Clynx® Platform will not only retain its core features, including motion capture through a 3D camera and gamified rehabilitation exercises, but will also introduce additional functionalities to meet the evolving needs of both patients and healthcare practitioners, such as:

Real-time feedback It will detect posture errors during exercises and provides immediate warnings to patients, offering therapeutic guidance (cf. Fig. 3).

Quantitative measurements The software will gather data on exercise errors, range of motion, performance distance, and reaction time. These measurements aid healthcare professionals in therapeutic decision-making.

Clinical and motion data collection The software will compile quantitative measurements and presents graphical representations of a patient’s progress, facilitating the adaptation of treatment plans based on patient evolution (cf. Fig. 4).

3.1 Related work

Several companies are actively participating in the digital physiotherapy market, offering various solutions for neuro-musculoskeletal interventions. Within the existing landscape, Sword Health’s® solution boasts a class II medical device certification from the Food and Drug Administration, United States of America (FDA), while getUBetter® is recognized as a class I medical device software, certified by the NHS. Curovate® and Physiotec® have attained certification as medical devices, though their specific classification is not provided (although they are likely to be classified as Class I). On the other hand, there is a dearth of publicly accessible information regarding the certification status of the other solutions. Consequently, it is probable that these remaining solutions are categorized as wellness and well-being devices.

The forthcoming sections will elucidate the prospective certification process for the in-development version of the Clynx® Platform, through QMS and TD assessment.

3.2 Qualification as a medical device

The Qualification as an MD specifies the characteristics of the device which make it compliant with the MD definition on the MDR, including its intended purpose, intended user groups, and the context of use [5]. With this understanding and taking into account all the features of the new version of the Clynx® Platform, the intended purpose of the Clynx® Platform will be as presented in Fig. 5.

3.3 Classification

Considering the new Clynx® Platform’s specified functions, such as real-time feedback, quantitative measurements, and clinical data collection, it will actively engage patients and records bio-kinetic data.

The software’s purpose will include offering information to health professionals for therapeutic decisions. Importantly, decisions made by healthcare professionals with the software’s assistance will not carry the risk of causing death, health deterioration, or necessitating surgical interventions. Additionally, the software will not be intended for vital physiological parameter measurements. Consequently, the device will align with Sub-Rule 11(a), classifying it as Class IIa, as it will fall under Software intended to provide information which is used to take decisions with diagnosis or therapeutic purposes [5]. The text to be included in the new version of the Clynx® Platform’s TD is presented in Fig. 6.

Fig. 6

Classification of the medical device justification, which will be included in the Classification File in the Clynx® Platform’s TD. Image obtained from Clynx® Health

Fig. 7

Requirement 15 which will be included in the GSPR File in the Clynx® Platform’s TD. Image obtained from Clynx® Health

3.4 General and safety performance requirements

Considering the Clynx® Platform’s future role in performing quantitative measurements as part of its Intended Use, it will qualify as a measuring device [5]. Consequently, adherence to the Requirements for devices with a measuring function (Requirement 15) will be vital. This requirement underscores the necessity for diagnostic and measuring devices to be meticulously designed and manufactured to ensure accuracy, precision, and stability that align with their intended purpose. This requires the application of robust scientific and technical methodologies, with Clynx® Health clearly specifying accuracy limits [5]. The text included in Clynx® Platform’s TD will be presented in Fig. 7.

Therefore, Requirement 15 mandates evidence from tests that assess the accuracy, precision, and stability of the quantitative measurements conducted by the software [5, 12]. These clinical studies will be an integral part of the device’s Clinical Evaluation.

3.5 Risk assessment

The risk management file of Clynx Platform was produced according to the guidelines presented in ISO/TR 24971:2020 [17] and ISO 14971:2019 [16] and has the following phases:

Risk Assessment The process of assessing the risks related to the medical device by documenting reasonably foreseeable misuse, identifying hazards and hazardous situations, its causes and consequences, and estimating their risk combining the probability of occurrence of harm and possible severity of consequences.

Risk Evaluation The determination of acceptability of estimated risks is done by applying a risk matrix to every risk identified and determining if it can be reduced by applying control measures or if the benefits outweigh the risks, and it can be considered an acceptable risk.

Risk Control Application of control measures in order to reduce risks to its acceptability point by reducing the probability of occurrence or the severity of consequences.

Residual Risk Evaluation Even after reducing risks to its acceptability point and applying risk control measures, there are still residual risks remaining which need to proceed to a benefit-risk analysis and, if the benefit does not outweigh the risk, control measures need to be applied.

3.6 Clinical evaluation: clinical evidence generation

Clinical Evaluation stands as a pivotal phase in securing CE marking, playing a crucial role in both showcasing and validating the performance of a medical device. The Clinical Evaluation Plan (CEvP) serves as the blueprint for this process, demanding clear articulation of the medical device’s clinical benefits and underscoring its significance in the healthcare market [5, 12]. This article only focuses on the first step of CEv, which is clinical evidence generation.

In an endeavour to meet these rigorous standards, Clynx® Health executed a clinical study, assessing both the usability and social, economic and environmental impact of telerehabilitation facilitated by the current version of the Clynx® Platform [9]. This study serves as an integral component of the Clinical Evaluation (CEv) for the medical device.

Fig. 8

Clynx® Platform and Qualysis® camera systems set-up

Looking ahead to the future Intended Use of the Clynx® Platform, the software is poised to function as a crucial auxiliary tool for healthcare professionals. Its role will be to empower them to craft tailored physical rehabilitation treatment plans that adapt to the evolving needs of each patient. Consequently, the inclusion of a performance claim, specifically related to quantitative measurements [12], becomes imperative; as “Quantitatively measures body movement, including range of motion, reaction time, and covered distance from the start position, with a specified level of precision, accuracy, and stability, aiming for a minimum of 90% and ideally reaching 95%”. The incorporation of this quantitative measurements feature within the future Clynx® Platform software is of paramount importance, necessitating validation of its scientific robustness to ensure reliability in monitoring patient progress during physical rehabilitation and treatment plan adjustments [12]. Conforming to the specifications outlined in Requirement 15, a critical step involves the execution of technical performance validation, encompassing an evaluation of accuracy, precision, and stability of these measurements [12].

Fig. 9

Qualysis® markers set-up. Obtained from [2]

For further clarity on the implementation of an experimental protocol within a clinical study for the Clynx® Platform CEv, please refer to the following section (cf. Section 3.6.1).

Fig. 10

Quality Management System process map. Obtained from Clynx® Health

Fig. 11

Gantt chart outlining a forecast for the certification process of the Clynx® Platform. The deadlines depicted in this figure are optimistic predictions based on the feedback received from the contacted NBs. This chart serves for illustrative purposes only

3.6.1 Experimental protocol for validation of technical performance: assessing range of motion accuracy, precision and stability in upper and lower limbs exercises

Clynx® Health is working in the scope of a validation protocol (Reference: 17/CES/2022) in partnership with Escola Superior de Saúde de Santa Maria. This project aims to build an experimental protocol for performing a comparative analysis between the established gold-standard motion capture system, Qualysis®Footnote 10, and the emerging Clynx® Platform in evaluating the Range of Motion (ROM) measurements’ accuracy, precision and stability.

The study will involve healthy subjects participating in a simulated physiotherapy session at the Centro de Investigação para a Reabilitação, located at Escola Superior de Saúde do Instituto Politécnico do Porto. Crucially, every participant in the study will meet the inclusion criteria by confirming the absence of any prior history of lesions of the neurological, muscular or skeletal nature, the absence of pain during movement, and the absence of any prior musculoskeletal surgeries. The session plan will include two sets, with a rest period of 10 seconds, each consisting of seven repetitions of the following exercises: Shoulder Flexion/Extension, Shoulder Abduction/Adduction, Elbow Flexion/Extension, Shoulder Press, Hip Abduction/Adduction, Squat, March, and Seated Knee Flexion/Extension. The data collection setup is illustrated in Fig. 8.

The Clynx® Platform will employ two Astra S cameras operating at a frequency of 100 Hz. Positioned at a height of 86 cm above the floor, the subjects will stand 2.3 m away from the cameras, which will be spaced 25 cm apart and oriented towards the subjects. In the Qualisys® Motion Capture System, 3 infrared miqus M3 cameras and 8 oqus 500+ cameras will be employed, all operating at 100 Hz [10, 15]. Reflective markers will be arranged as depicted in Fig. 9.

During the session, concurrent recordings will be conducted: one capturing the ROM using the Clynx® Platform software, and another recording the 3D positions of markers through the Qualisys® system.

The subsequent data processing will involve algorithmic development. These algorithms will be utilized to convert the 3D positions obtained from the Qualisys® system into ROMs. Additionally, the algorithms will analyse the ROM data from both the Clynx® Platform and the Qualisys® system during the exercises performed by each participant.

To conduct a comparative analysis between the Clynx® Platform and Qualysis® ROM measurements (accuracy), and the Clynx® Platform data from different sets (precision) and from different cameras (stability), the agreement between the outputs of both sources will be evaluated. Two metrics are going to be employed, namely: the correlation coefficient, and the Bland-Altman test.

The correlation coefficient measures the linear association between two variables, ranging from +1 (complete positive correlation) through 0 (complete absence of correlation) to -1 (complete negative correlation). Positive correlation occurs when one variable increases as the other increases, while negative correlation is observed when one decreases as the other increases [18]. The Bland-Altman test involves studying the mean difference and constructing limits of agreement.

The Bland-Altman plot provides a simple means to assess bias in mean differences and estimate a 95% agreement interval [6, 7]. The accuracy, precision and stability values will be determined based on the relative error formula (cf. Eq. 1), where the true values are from Qualysis® and the observed ones are from the Clynx® Platform. All metrics will be implemented using Python algorithms.

$$\begin 1 - Relative Error = 1 - \frac \end$$

(1)

3.7 Quality management system

In 2022, Clynx® Health initiated the establishment of its QMS to align with EN ISO 13485. This strategic move is a crucial step towards obtaining medical device certification and securing the CE marking for the Clynx® Platform.

Clynx® Health’s QMS is organized into three categories: Management Processes, Core Processes, and Support Processes (cf. Fig. 10). These categories encompass various specific processes and associated supporting documentation, including the Quality Manual, Standard Operating Principles (SOP), and Technical Documentation. SOPs offer detailed step-by-step descriptions of each process, including their interconnections with other processes within the same category [8].

Clynx® Health proactively conducted an Internal Audit to assess its QMS in preparation for certification with NBs. This comprehensive remote audit, conducted by an independent external firm, focused on design and development, production, installation, and support services for the Clynx® Platform. The audit verified the compliance of the QMS with audit criteria and its ability to ensure compliance with regulatory requirements, contractual obligations, and expected outcomes. It also identified potential areas for improvement within the QMS.

The audit agenda covered Management Processes, Operational Processes, Resources Management Processes, Purchasing Processes, Improvements Management, and Regulatory Requirements. Some EN ISO 13485 requirements were deemed not applicable to the Clynx® Platform due to the nature of a medical software product.