The role of 3D digital applications in Manual Therapy Education – A scoping review


 Background: Currently, teaching methods for developing complex physical assessment and palpation skills in manual therapy is challenging for both learners and educators. 3D digital technologies such as virtual reality (VR), augmented reality (AR) and mixed reality may facilitate and/or address these challenges. However, their current usage and/or role in improving learning outcomes in manual therapy education is still largely unknown. Methods: The following electronic databases were searched from Jan 2005 to April 2021: PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Physiotherapy Evidence Database (PEDro), Science Direct and Google Scholar. Two independent reviewers reviewed the articles retrieved from the databases to assess for eligibility. Studies of any methodology (quantitative, qualitative and mixed methods) that investigated the use or application of the 3D digital applications were included in the review. Primary outcomes included any outcome related to learning based on the updated Blooms taxonomy. Narrative synthesis was used to synthesise data from the included studies.Results: A total of 4 articles were included in the final review. The main findings were classified into the following key concepts: (1) perception of tissue stiffness, (2) improved student self-efficacy in performing MT techniques, and (3) barriers and facilitators for utilizing 3D technologies. All included outcomes met understanding, applying, analysing and evaluating levels of Blooms taxonomy; however, no outcomes met the ‘creating’ level of Bloom’s taxonomy.Discussion: Our review found that there are no AR, VR or mixed applications that specifically serve the needs of MT education in relation to joint motion assessment, but applications are available that can be readily used or potentially adapted to train skills of tissue palpation. . Therefore, future studies are required to investigate the sophisticated requirements to teach/learn complex manual techniques for which palpation skills may be mandatory.


Background
3D digital applications such as virtual reality (VR), augmented reality (AR) and mixed reality technologies have been around for decades, with their use extended to several applied elds, amongst others, teaching and learning (Hamilton, McKechnie, Edgerton, & Wilson, 2020). These systems often adapt virtual 3D visualizations to make di cult ideas more comprehensible by mimicking real-life scenarios. An AR system combines or "supplements" real world objects with virtual objects or superimposed information (Brigham, 2017) while in a VR system, the user is completely immersed inside a virtual environment (VE) (Hamilton et al., 2020). Evidence indicates that AR visualization in educational settings can improve task completion times, lead to fewer errors and improve student's motivation to learn (Khan, Johnston, & Ophoff, 2019).
Students of manual therapy (MT) are required to develop complex clinical skills such as clinical reasoning, manual/physical assessments, palpation and patient management which includes skilled hands-on treatment (Michels, Evans, & Blok, 2012). The process of learning clinical manual therapy skills usually incorporates the widely accepted 'See one, do one, teach one' approach, where students learn by observing an expert clinician/tutor performing the techniques on a student, a plastic anatomical model, or a patient (Bugaj & Nikendei, 2016;Easton, Stratford-Martin, & Atherton, 2012). The underlying assumption of such an approach is that trainees can become increasingly independent after observing an expert clinician or teacher for a few times (Kotsis & Chung, 2013).
Nevertheless, the 'See one, do one, teach one' approach has been criticized as an inadequate method in maintaining required patient safety standards because of the lack of supervision, re ection on action, performance evaluation and structured feedback (Lenchus, 2010;Rodriguez-Paz et al., 2009).
Haptics refers to the sense of touch, including both tactile and kinaesthetic perceptions/feedback of an object. Various haptic devices are commercially available; e.g., the Geomagic Touch haptic device, the Phantom Omni, the Falcon (Novint, USA) or the Sigma.7 (Force Dimension, Switzerland), to name a few.
Some grounded haptic devices (e.g., Mater-Finger-2) have been designed speci cally to support ngers which can be operated using the index nger and the thumb to grasp virtual objects and can also provide 6-DOF (Degrees-of-Freedom) (Monroy, Oyarzabal, Ferre, Campos, & Barrio, 2008;Pacchierotti, Chinello, Malvezzi, Meli, & Prattichizzo, 2012). The addition of haptic feedback in VR environments creates more realistic scenarios, while providing trainees with a safe environment in which they can develop their skills (Kirkman et al., 2014). It is through palpation (diagnosis through touch) that a clinician/student examines muscles in spasm and tissue abnormality which contributes important information to clinical reasoning, diagnosis and treatment in MT (Loh et al., 2015;Tong et al., 2018). Hence, it is possible that 3D digital technologies may enhance MT education relevant to E-learning; e.g., landmark palpation and localization, active and passive physiological movement assessment, and skills relevant to joint mobilization and manipulation such as the perception of tissue compliance. However, the use of 3D digital technologies (such as AR, VR and mixed realities) in improving learning outcomes in MT education is still largely unknown.
Scoping reviews are a form of knowledge synthesis, which incorporate a range of study designs to comprehensively summarize and synthesize evidence with the aim of informing practice (Arksey & O'Malley, 2005). We considered a scoping review as the most appropriate method as little is known about the current usage of 3D digital technologies in MT education. The aims of the current scoping review were to: 1) Summarize the literature on the current usage of threedimensional (3D) digital applications (emulating virtual, augmented or mixed reality environments) in manual therapy education to improve any outcome relevant to learning of manual therapy by students, clinicians and academics; (2) Synthesise the literature on facilitators and barriers for using 3D digital applications as an educational tool for manual therapy.

Methods
The Arksey and O'Malley framework (Arksey & O'Malley, 2005) and Joanna Briggs Institute (JBI) recommendations (Peters et al., 2020) were followed to conduct this scoping review. This protocol is reported in accordance with the preferred reporting items for systematic reviews and meta-analysis extension for scoping reviews (PRISMA-ScR) checklist.

Operational de nitions
Manual examination is operationally de ned as a passive examination of joint motion which tests for displacement and tissue resistance to displacement (i.e., tissue compliance akin to stress/strain properties) (Huijbregts, 2011). Perception of tissue compliance through palpation is an integral part of this examination method.
Manual therapy treatment is operationally de ned as skilled hands-on intervention intended to improve tissue extensibility, increase range of motion of the joint complex, and mobilize or manipulate soft tissues and joints.
Digital applications are operationally de ned as software applications that are compatible with mobiles (smartphones), computers, tablets, iPads, headmounted display, websites, or similar technological devices/platforms.
Augmented reality (AR) refers to the integration of the actual world with digital information about it. Actual objects and people cast an information shadow: an aura of data which, when captured and processed intelligently, can offer extraordinary value to consumers. Augmented reality uses technology to make such a layer of information accessible to people to blend one's perception of the actual world with digital content about it generated by computer software (Brigham, 2017;Farshid, Paschen, Eriksson, & Kietzmann, 2018).
Virtual reality (VR) refers to complete, 3D virtual representations of the actual world or of objects within it. Full immersion is a unique aspect of VR (Farshid et al., 2018).
Mixed reality (MR) refers to the merging of real-world virtual constructs with computer-generated constructs that are either real or possible. MR combines aspects of the actual reality--the physical world around us--with the power of virtual reality. It also combines what's real with what's possible (Brigham, 2017;Farshid et al., 2018).
Degrees of Freedom (DOF) is operationally de ned as the number of different ways they can move or create forces. A simple haptic device has 1 DOF. Complex haptic devices that can move anywhere in space (x,y,z) and create forces in any direction have 3 DOF. In addition to 3 DOF, if a haptic device can also track rotations and create rotational forces (torques) such as roll, pitch, and yaw; then it would be considered a device with 6 DOF.

Eligibility criteria
Inclusion criteria: Studies were included if they meet the following criteria.
Interventions -education of manual therapy skills or skill components (e.g., tissue palpation) delivered through 3D digital applications emulating augmented, virtual or mixed reality environments.
Comparators -studies were included without and with a comparator group (randomized/controlled clinical trials). Comparators could be any other method of manual therapy education (computer-based education material, face-to-face teaching, laboratory-based hands-on techniques, two-dimensional pictures, audiovisual materials, printed handouts, etc.) Outcomes -primary outcomes included any outcome related to learning based on the updated the Blooms taxonomy, i.e., remembering, understanding, applying, analysing, evaluating and/or creating manual therapy skills (Ramirez, 2017). The learning outcomes could be assessed using objective structured practical examination (OSPE), objective structured clinical examination (OSCE) or observation of student performance with or without recorded videos.
Secondary outcomes included questionnaires, surveys or qualitative assessment of participant's perception, preferences, satisfaction, barriers and facilitators, and the usage of digital technologies for MT education and/or clinical practice.
Type of studies -randomized clinical trials, controlled clinical trials, quasi-experimental studies, case-series, cross-sectional, qualitative and mixed-methods studies.
Study setting -studies must have taken place in an educational, laboratory, classroom or clinical setting; studies done in any health profession that have direct and indirect implications for teaching MT assessment and treatment.

Exclusion criteria:
Studies were excluded if: (1) a 3D digital application was not used in an educational context for teaching MT skills; (2) classroom/lab-based teaching or other technologies (e.g., videos) excluding 3D digital applications, were used as the sole intervention for MT education; (3) digital applications incorporating 3D AR, VR or MR applications were used for teaching subjects/courses other than manual therapy; and (4) studies were published in any language other than English.

Electronic databases
The following electronic databases were searched from Jan 2005 to April 2021: PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Physiotherapy Evidence Database (PEDro), Science Direct and Google Scholar. The reference lists of all included studies, following screening, were also checked for any other relevant citations.
Identifying relevant studies (search strategy) A systematic search strategy was developed to locate studies relevant under three key domains: participants (manual therapy students and practitioners), interventions (digital applications), and outcomes (manual therapy knowledge/skills). A combination of keywords using the Boolean operators "OR" and "AND" within and between each of the key domains respectively was undertaken (Table 1). A pilot search was conducted independently by one reviewer and the retrieved articles were screened independently by two reviewers (KSK and AA).
Following the pilot search, eligibility criteria for the inclusion of relevant studies were reviewed and the search strategy was re ned iteratively. A re ned nal search strategy was run by one reviewer to identify relevant studies.
Articles obtained by the systematic search were exported and saved into a reference management software program (EndNote X7 Thomson Corporation).
Titles of the retrieved articles were screened for relevance after removing duplicates. Relevant abstracts were screened followed by retrieval of the full text of articles meeting the inclusion criteria. The screening procedure was conducted independently by two reviewers (KSK and AA). Disagreements were resolved by discussion; if no agreement could be reached, a third reviewer (GJ) was consulted to reach a consensus.

Data Extraction
The research team collectively decided which data/variables to extract. A data charting table/form was used to standardise this procedure. Data were extracted by one reviewer (KSK) and veri ed by another reviewer (AA). A third reviewer (GJ) was consulted in case of any disagreement.

Synthesis of results
The studies included in the review were scrutinized to understand at which level(s) they contributed to the Bloom's taxonomy. All included outcomes met understanding, applying, analysing and evaluating levels of Blooms taxonomy; however, no outcomes met the 'creating' level of Bloom's taxonomy. Further, we explored secondary outcomes such as the key barriers and facilitators for utilizing 3D technologies in MT practice and educational settings. A narrative synthesis approach was undertaken for this purpose. The main ndings were classi ed into the following key concepts: (1) perception of tissue stiffness, (2) improved student self-e cacy in performing MT techniques, and (3) barriers and facilitators for utilizing 3D technologies.

Perception of tissue stiffness
Two studies measured the effectiveness of 3D technologies in improving perception of tissue stiffness (Howell et al., 2008;Tong et al., 2018). In one study, the researchers developed a VR with magnetic levitation haptic device for augmenting tissue stiffness perception in a natural manner based on electromagnetic principles. Those authors compared the new device with a Phantom Omni device to distinguish objects of different stiffness and to detect tissue abnormality of 6 different kidney models. The ndings demonstrated that VR with magnetic levitation haptic device enhanced palpatory skills of the participants, not only to distinguish different tissue stiffness but also to correctly detect tissue abnormality in the virtual environment (Tong et al., 2018). In another study, the researchers developed a virtual haptic back (VHB) which presented to users, both haptically and geographically (by feel and sight), the simulation of the contours and the tissue textures of the human back. The tissue texture was measured as tissue compliance (the inverse of stiffness) with a PHANTOM 3.0 haptic interface (SensAble Technologies, Woburn, MA) used as a force-displacement probe. Participants' (112 rst year osteopathic students) palpatory performance were measured with the PHANTOM 3.0 device before and after 6 sessions with the VHB. Webber's fraction (compliance difference between the abnormal region and the adjacent normal region) was used to measure the detection of tissue compliance. The results showed that using VHB not only improved palpatory performance in detection of tissue compliance (Webber fraction: 28% (pre) to 14% (post)) but the average time per localization of abnormal tissue fell from 39 s to 17 s. In turn, an overall measure of performance that included both accuracy and speed of palpation were also shown to improve continuously resulting in the mastery of palpatory process (Howell et al., 2008). Increased student satisfaction and self-e cacy Three studies (Howell et al., 2008;Tong et al., 2018;Ullrich & Kuhlen, 2012) measured the overall acceptance of the simulators (VR with haptic device, VR with magnetic levitation device and VHB) using subjective questionnaires. Simulations received mostly positive ratings and an improvement in performance was accompanied with an increased self-e cacy of students. Tong et al. (2018) measured the perceived quality of experience (QoE) for tissue stiffness perception, which is related to subjective user experience with a service or an application. The QoE is based on four factors namely (1) sensory perception (how much the haptic device contributed to augmenting the stiffness perception of tissue), (2) realism (how much the virtual environment is realistic), (3) comfort (how comfortable the haptic device is to use), and (4) satisfaction (whether the user prefers to use the device). Each factor was evaluated by questions rated on a 5point scale. The mean value was calculated and QoE was computed as the sum of these 4 factors. It was found that the magnetic levitation haptic device increased the QoE, especially the 'sensory' component enabling the interaction consistent with the user's habits of the real world. Howell et al., (2008) surveyed the students who used the VHB to understand whether improved performance on the VHB translated into better palpatory diagnosis of real patients. Most participants in their study reported that the VHB was helpful and improved palpation on real patients thereby improving their con dence and self-e cacy. Ulrich and Kuhlen (2012) proposed a novel approach to enable haptic palpation interaction for virtual reality-based medical simulators. a post-test questionnaire with a 7-point Likert scale (1 = strongly agree, to 7 = strongly disagree). The items were grouped into controls and interface, visuals, simulation, haptics of the simulator, acceptance and detailed questions about the palpation pad and palpation interaction. The study found that the overall acceptance of the simulator got mostly positive ratings.

Facilitators and barriers for utilizing 3D technologies
Our review identi ed several facilitators for using 3D technologies. Often students regard these technologies as a fun and meaningful way to learn (Howell et al., 2008;Tong et al., 2018;Ullrich & Kuhlen, 2012). After the initial training, the applications were perceived to be easy to use which is an important factor in trialling new technologies (Howell et al., 2008). A key advantage of using the 3D technologies was the many opportunities for students to practice their skills (Howell et al., 2008). Through repeated practice using 3D technologies, the students were not only able to integrate physical and cognitive tasks but were able to transfer their training to real life, thereby, improving their self-e cacy in clinical use of the technology (Howell et al., 2008;Tong et al., 2018).
Our review identi ed several barriers for using 3D technologies in MT education including (1) problems with hardware devices, (2) learning time, (3) realism, and (4) resource related issues. A key barrier for using 3D technology was the di culty of using a hardware interface, which some participants perceived as being 'intimidating'. Further, head mount devices can be also intimidating to a non-technical user and could be potentially non-ergonomic for longer training sessions (Ullrich & Kuhlen, 2012). Participants across studies also reported that the time taken to learn and familiarise themselves with the software/hardware and how to control the simulators can be long and may act as a barrier to use 3D technologies (Howell et al., 2008;Tong et al., 2018;Ullrich & Kuhlen, 2012). A key aspect of a 3D technology is to feel as natural as possible, which is known as 'realism' (Tong et al., 2018). Good systems achieve realism with minimal effort by the user even without prior training (Ullrich & Kuhlen, 2012). Minimal or lack of realism was identi ed as a barrier for using 3D technologies (Tong et al., 2018;Ullrich & Kuhlen, 2012). On the other hand, solutions that can provide high tactile realism are prone to material deterioration from repeated use. This incurs much cost and questions about sustainability may deter potential users from utilizing these technologies (Ullrich & Kuhlen, 2012).

Summary
Our review found that there are no AR, VR or mixed applications that speci cally serve the needs of MT education in relation to joint motion assessment, but applications are available that can be readily used or potentially adapted to train skills of tissue palpation. Our ndings suggest that 3D technologies enhance palpation skills not only to distinguish different tissue stiffness but also to detect tissue abnormality in the virtual environment. Repeated practice and familiarity enabled the users of 3D technologies to become faster at localizing the abnormalities, thereby improving their physical assessment in a virtual and an actual clinical environment. In turn, student self-e cacy and satisfaction of using 3D technologies also increased. Nevertheless, various barriers and facilitators were identi ed for utilizing 3D technologies that may be relevant to consider while using these technologies in musculoskeletal practice.
To our knowledge, this is the rst scoping review to summarize the literature on the current usage of 3D digital technologies (emulating virtual, augmented or mixed reality environments) and to identify barriers and facilitators of utilizing such technologies that are relevant to MT. Our review found that palpatory performance improved after a few sessions with 3D technologies. These results are not surprising as improvement in performance comes with practice in any task and consistent with previous ndings (Khaled et al., 2003;Tong et al., 2018;Ullrich & Kuhlen, 2012). Additional features such as bimanual interactions that enable two tasks to be done at the same time and "sensor" hands that interact with the skin surface of the virtual patient providing rich haptic feedback (Ullrich & Kuhlen, 2012). Taken together, ndings suggest that users of 3D technologies might become faster at localizing the abnormalities, improve physical assessment skills and show increased satisfaction with 3D technologies.
In future designs of technologies for MT applications, educators could share the clinical reasoning behind a physical assessment procedure enabling the developer to integrate the software parameters that control the degree of physical tasks and challenges to meet the assessment needs. This step may be crucial as physical assessment procedures vary depending on the anatomical area of interest. For example, the physical assessment parameters required for assessing a shoulder joint will be different from that of assessing an ankle joint and so on. Whilst it is important to provide exibility for users, it is also important not to overwhelm students/users with abundant decision-making requirement or decreased ease of use, which may reduce the sense of intimidation (Glegg & Levac, 2018). Although participants across studies expressed satisfaction using 3D technologies, literature has shown that motivation of users of 3D technologies often declines over time. Hence, the technologies designed for MT education may need to consider attributes that sustain motivation and engagement of learners over a longer period (Khan et al., 2019).

Strengths and limitations
One of the strengths was that we used a comprehensive search strategy to maximize opportunity for locating all relevant studies representing the phenomena of interest. We expect minimal biases in extracting and reporting of data. Only four eligible studies (Howell et al., 2008;Khaled et al., 2004;Tong et al., 2018;Ullrich & Kuhlen, 2012) were included in narrative data synthesis which would account for an overall low certainty of current evidence in this area. The small number of studies included however may represent the lack of research done in this area. We only included English language studies and omitted gray literature which might be seen as a limitation. We have precluded methodological quality or risk of bias assessment of the included studies as it is not a mandatory requirement for a scoping review.
Our ndings suggest that 3D technologies may improve palpatory performance. However, it must be noted that only one study (Howell et al., 2008) was done purely in an MT setting. Hence, the exact role of 3D technologies in enhancing MT assessments remains unknown. Further, an objective demonstration of improvement in palpatory performance in a clinical setting would provide robust evidence for using such technologies in MT education. Further, the role of 3D technologies in the assessment of clinical reasoning and/or providing feedback of physical assessment for MT students remains unclear. Finally, it has to be made explicit that 3D technologies may augment MT education, but cannot replace face-to-face teaching completely. Nevertheless it could also be argued that such technologies could play an important role where face-to-face teaching may not be possible (e.g., COVID pandemic).

Implications for MT practice/education and research
While these technologies can provide high tactile realism, the hardware devices can be challenging to adjust to and can be prone to material deterioration from repeated use (Fitzgerald, Denning, Vaughan, Fleischmann, & Jolly, 2019). This may incur additional costs which may deter educational institutions to trial these technologies. While many of the existing technologies are not directly relevant to MT requirements, the technology is there to develop relevant applications. Our review found that VR with haptic feedback was better than normal simulators in enhancing palpatory skills and physical assessment skills in students, because of full control over the environment.
Successful palpation requires skills such as sense of texture, tissue compliance/stiffness, lateral motions and high DOF. Studies included in the review often incorporated 3 DOF movements which may be adequate However, future studies could trial devices that might allow for 6 DOF movements (Ullrich & Kuhlen, 2012). Recent advances such as hand exoskeletons that provide more DOF and mimic the hand movements of the operator may be of particular interest to students learning manual therapy as these may replicate and/or meet the sophisticated requirements to teach/learn complex manual techniques for which palpation skills may be mandatory.