Version 5.0
Instructions for Use
in accordance with
the Medical Devices Directive 93/42/EEC as amended by
EU Council Directive 2007/47/EC of 5th September 2007
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Warning
The Devices, including supporting software and biomechanical models, are not intended to replace the clinical skill of a medical practitioner or his/her independent professional judgement of individual clinical circumstances to determine a patient's treatment. The system, software and biomechanical models should only be used by those who have been appropriately trained in its operation, functions, capabilities and limitations, and in any event should not be relied upon, by itself, as the sole method of determining any treatment.
Descriptions of the meaning of symbols used to BS EN ISO 15223-1:2016 - Medical devices - Symbols to be used with medical device labels, labeling and information to be supplied - Part 1: General requirements is at Annex A.
Contents
Trade name of applicable devices
Product trade name of the devices
CLASS I Measuring Devices:
- Vicon Vantage system
- Vicon Vero system
Registered trade name of the manufacturer and the address of its registered place of business
Trade name and address of manufacturer
Vicon Motion Systems Ltd (trading as Vicon)
Unit 6, Oxford Industrial Park,
Mead Road,
Yarnton OXON OX5 1QU
United Kingdom
Registered trade name of the authorized representative and the address of its registered place of business
Trade name and address of authorized representative
GPEM srl
Via Remartello 49 / F
Loreto Aprutino
65014 Pescara
Italy
Intended purpose
Intended use/purpose
Vicon Gait Analysis Systems are intended to provide information which is used to take decisions for therapeutic purposes and to aid in the understanding of the etiology of gait abnormalities resulting from a diagnosis of cerebral palsy or Duchenne muscular dystrophy among presenting children and adolescent patients. The interpretation of resulting kinematic and optional kinetic and electro-myographic data remains in the hands of interdisciplinary teams of health care professionals and biomechanists with substantial knowledge of normal and pathologic human gait where characteristics are measured, abnormalities are identified, causes are postulated, and treatments are proposed. The same technology is routinely applied to establish the efficacy of orthoses and prostheses, and during rehabilitation among the wider population. The purpose is to improve the efficiency of patient ambulatory locomotion [1].
Target patient population
Gait analysis is appropriate for guiding decision-making on management in such disorders as cerebral palsy, stroke, traumatic brain injury and myelomeningocele, Duchenne’s muscular dystrophy patients; artificial limb fitting services.
Contraindications
None
Warnings/cautions
The devices use infrared/near infrared light to illuminate the markers. Photobiological safety calculations made and published to minimize impact.
Expected clinical benefits
Specification of the clinical benefits to be expected
Quantitative clinical gait analysis
Derived from the 2002 seminal work of Davis RB, Õunpuu S, DeLuca PA, Romness MJ, Clinical Gait Analysis and Its Role in Treatment Decision-Making [1] and of David Sutherland’s review on the evolution of clinical gait analysis with a focus on kinematics [2] and kinetics [3].
Since 1984, Vicon Motion Systems has captured and reconstructed the three-dimensional spatial and temporal location of retroreflective markers applied to palpated surface anatomy landmarks to derive and describe an estimation of the motion of underlying joints and bone segments. This is achieved with independently validated clinical gait models outside the scope of this evaluation. The company publishes within declarations of conformity of optical reconstruction performance (kinematics) and analogue to digital performance to facilitate ingestion of approved third-party ground reaction forces (kinetics) and electromyographic voltages. The company products are further tested to ensure optical and analogue data are synchronized to within one video frame.
The goal of clinical gait analysis is to assist in treatment decision-making for a patient with complex and not easily understood walking problems. Quantitative clinical gait analysis is a process whereby gait characteristics are measured, abnormalities are identified, causes are postulated, and treatments are proposed. The approach involves the placement of external markers or targets at specific points on the lower extremities and torso of the patient. These markers are then monitored by video cameras as the patient walks along a straight, level pathway. The two-dimensional camera images are analysed by a central collection computer incorporating validated photogrammetric reconstruction algorithms to quantify the movement of specific joints and body segments in three-dimensonal space. For example, by measuring the thigh and shank simultaneously, you can appreciate knee motion.
This analysis of motion can be combined with measures of muscle activity and the reaction forces between the patient's foot and the ground, to provide a comprehensive assessment of the biomechanics of locomotion.
It is important to appreciate that while quantitative gait analysis uses technology to measure gait patterns, it does not replace the human observer (ie, the observational gait analysis approach that a clinician might employ in a clinic or office setting). Rather, clinical gait analysis serves as an adjunct to aid understanding – more precisely and at times more accurately – of visual impressions of a patient's gait impairment. Through the thoughtful use of technology, quantitative gait analysis provides an opportunity to appreciate the details of complex movement patterns that may involve a number of lower (and upper) extremity joints and segments simultaneously and include movements that occur in several planes of motion concurrently, as well as to understand and correlate the associated muscle activity.
It is also important to understand that while treatment decision-making is facilitated by clinical gait analysis, these decisions are always made in the context of the clinician's experience in gait analysis and in the management of the particular disorder presented by the patient. Quantitative gait analysis does not dictate clinical treatment. Although patients seen most often for gait analysis present with complex and sometimes subtle gait deviations that suggest surgical intervention is necessary, other recommendations for management may include physiotherapy exercises, bracing (orthoses), spasmolytic medications (such as, Botulinum toxin, baclofen), or condition monitoring.
The objectives of this report are to illustrate to the reader the process of clinical gait analysis and to clarify when it might be of benefit for individuals with walking concerns. Several questions commonly asked about clinical gait analysis are addressed, including:
What is involved in a clinical gait analysis test? That is, how is it performed?
Since 1984, clinical gait analysis using Vicon Motion System products has involved the measurement of the patient's gait pattern with specialized technology. In the interim, technological improvements have enhanced the ease of use, reliability, sensitivity and specificity of the analysis, but the method has remained unchanged. The medical practitioners and health professionals at each clinic document the pertinent medical history and physical presentation, and this collection of manual and captured information provides the basis upon which treatment decisions are made.
- Initial presentation
- Physical examination
- Kinematics, kinetics and electromyographic assessment
- Vicon motion capture systems (CLASS Im)
- Ingestion of data from third-party ground reaction force plates
- Ingestion of data from third-party electromyography equipment
- Gait laboratory staff competencies
- Institutional standards
Initial presentation
Among the first examinations of the patient in the gait analysis laboratory is the careful observation by the clinician of the patient, barefoot and, perhaps, in orthoses, as she/he walks along a smooth, level pathway. Video recordings can be taken provide a qualitative documentation of how a person walks, affording an opportunity to evaluate the "smoothness" or "fluidity" of a gait pattern. The ability to obtain close-up views of a specific motion and the use of slow motion greatly enhance the observer's ability to evaluate the patient's walking pattern. For example, close-up views of the feet provide a means to evaluate hind foot position and motion.
Physical examination
The patient usually undergoes an extensive physical examination of their status at rest. The specific measurements depend somewhat on the pathology being evaluated. These measures may include the passive lower extremity joint motion, joint and muscular contracture, muscle strength and tone, bony deformity, and neurological assessment. This information may then be correlated with gait data to help determine the potential causes of the patient's gait deviations. However, the standard clinical examination used in isolation is limited in its capacity to offer diagnostic information because the effects of body position, gravity, and walking result in changes in functional demands that cannot be fully appreciated in a manual examination [4].
Kinematics, kinetics and electromyographic assessment
Central to a clinical gait analysis are the additional quantitative measurements of the patient's walking pattern provided from several different technologies.
Vicon motion capture systems (CLASS Im)
Passive retroreflective markers are placed on the surface of the patient's skin and aligned with specific bony landmarks and joint axes.
As the patient walks along a straight pathway in the laboratory, the locations of these markers are monitored with a three-dimensional motion data capture system comprising 8–12 optical cameras, all interfaced to a central controlling computer. Each of these cameras is equipped with an array of light-emitting diodes that strobe in synchrony with the camera shutters to illuminate the pathway with infrared or near infrared light. The light, which cannot be seen by the patient (and therefore does not distract the patient), is reflected by the markers back to the cameras. Computer programs allow the determination of the three-dimensional locations of the markers in space and time using photogrammetry and is analogous to the way depth is perceived in human vision with two eyes. Marker position data allow for the mathematical computation of the angular orientation of particular body segments as well as the angles between segments (ie, joint angles), collectively referred to as kinematics [2].
Ingestion of data from third-party ground reaction force plates
All Vicon motion systems support ingestion of data from approved third-party manufactured force plates to generate ground reaction force vectors. Multi-component force platforms imbedded in the walkway provide a measure of the net reactions between the foot and the ground as the patient walks along the pathway. These data may be assessed directly or used to calculate loads found in and across the joints of the lower extremity. These joint loads (referred to as kinetics [3]) are computed analytically from relationships drawn from physics that combine the simultaneously acquired kinematic information and estimates of limb mass and inertial properties [6].
Ingestion of data from third-party electromyography equipment
All Vicon motion systems support ingestion of data from approved third-party manufactured electromyography equipment (EMG). Electrodes placed on the surface of the skin or inserted as fine wires (smaller in diameter than human hair) into specific muscles allow muscle activity (expressed as action potentials) to be monitored as the patient walks along the laboratory pathway, through an approach referred to as dynamic electromyography. The EMG signal gives information concerning the "on-off" activity of a muscle. This information can be used with joint kinematic and kinetic results to better understand the patient's neuromuscular abnormalities [4, 7].
Gait laboratory staff competencies
A typical gait analysis test can take from one to two hours, depending on the particular evaluations performed and on the cooperation, behaviour, and gait complexity (ie, involvement) of the patient. Usually a clinical scientist, physiotherapist or kinesiologist works directly with the patient, and a more technically oriented person, such as an engineer or technician, manages the computer and measurement system operation during the test.
Institutional standards
It should be noted that not all clinical gait laboratories operate in this fashion. Some do not have the technology to provide three-dimensional body marker data and analytical processes that produce three-dimensional joint rotations (flexion-extension, abduction-adduction, and internal-external rotation) for interpretation. These clinical gait analysis laboratories use less sophisticated technology that collects and processes motion data based on the assumption that all of the rotations occur in the sagittal plane of the body. This assumes that all motions associated with gait can be appreciated from a side view of the patient. While this might not be unreasonable in the analysis of normal ambulatory motion (except perhaps for ankle/foot motion), it is clearly ill-advised for clinical decision-making in cases of pathological gait where three-dimensional motion is commonplace [11].
Moreover, at other facilities, a clinical gait analysis might be limited to a video recording and the measurement of certain gait stride and temporal parameters such as velocity, cadence, stride length, step length and percentage of stance/swing. While the video record is a useful tool in developing and substantiating visual impressions, it is inappropriate to "measure" joint and segment gait kinematics directly from the two-dimensional video imagery, even though some commercially available hardware and software products do this. With respect to stride and temporal parameters, these are "outcome" measures and provide an indication of the level of function when compared to normal values. They do not, however, give an indication of the cause of the gait abnormality and are, consequently, of limited value in clinical decision-making.
Similarly some laboratories capture only kinematic data so do not have access to the additional insights of kinetic information in their treatment decision making.
How are gait data interpreted?
Depending on the laboratory capabilities, the process of gait data collection, as described above, yields the following:
- Video image recordings (Vicon Bonita, Bonita 2 and Vue cameras)
- Clinical measures
- Stride and temporal gait data, such as step length, cadence, and walking speed (Vicon motion capture systems)
- Three-dimensional joint and segment motion plots (kinematics), (Vicon motion capture systems)
- Three-dimensional joint torque or moment and power (kinetics) results (Vicon motion capture systems with third-party force plates)
- Electromyographic (EMG) tracings (Vicon motion capture systems with third-party EMG)
- A measurement of metabolic energy expenditure (independent devices used by laboratory and out of scope)
These parameters are then evaluated to identify abnormalities, using a database of normal, typically developed subjects and knowledge of normal gait biomechanics as baseline. Deviations from normal are always interpreted in the context of their relative impact on gait function. These multiple sources of data provide useful redundancy, allowing corroborating information to be identified and conflicting observations to be understood.
A challenge in gait data interpretation is to identify the primary problems that perhaps need to be addressed and then to recognize secondary abnormalities, produced as result of the primary problems, and to appreciate compensatory mechanisms (ie, strategies the patient uses to overcome the impairment). For example, the primary problem of a crouched knee (as a result of the hamstring tightness and hip extensor weakness) can produce secondary "abnormalities" at the hip (reduced hip extension in stance) and pelvis (the posterior position), all of which should be resolved with hamstring intervention.
The role of the interdisciplinary team
At major clinical laboratories, gait data are interpreted by a team that consists of the orthopedic surgeon to whom the patient was referred and the clinical scientist, physiotherapist and/or kinesiologist who collected data. At times, the engineer or technician, who assisted in the data collection, or the biomechanical engineer who developed the mathematical models used to process data, is involved, if questions of data quality arise or if some previously unseen walking mechanism is encountered. Most laboratories will use multi-center, internationally validated conventional gait models for routine clinical analyses [12]. In general, it is important that the team has at least a rudimentary understanding of the gait model used to produce the results, in addition to a well-developed understanding of normal gait. This knowledge base, underpinned by experience gained from the examination of many pre- and post-treatment cases, is essential to produce a proper interpretation and treatment decision. The use of validated models facilitates the exchange of experience through multi-center collaborations and exchange using a common methodology at academic conferences.
What additional information is provided through gait analysis that augments observational analysis?
For gait analysis to be a useful tool in clinical decision-making, it must provide information that is not available through more traditional methods of evaluation. Use of clinical gait analysis systems augments visual observations by using:
- A quantitative description of complex movements that are not only multi-planar, but which also involve multiple lower extremity joints and the upper body
- An indication of the associated muscle activity
- A consideration of joint kinetic patterns
- An opportunity to learn from documented treatment outcomes
With this additional information, the clinician can be more confident about identifying gait deviations, determining their potential causes, and appreciating the treatment outcome. This entire process will ultimately lead to new treatment approaches and a reduction in the use of less effective interventions. The following examples are intended to illustrate how gait analysis can benefit the clinician in treatment decision-making.
I. Quantitative description of motion
Identifying abnormal motion in the transverse plane
Rotational abnormalities are a common problem in many neuromuscular disorders, such as cerebral palsy and myelomeningocele. Torsional bony deformities, identified during the clinical examination, may be present in the femur and/or tibia. Abnormal segment positions may be seen in gait, such as asymmetrical pelvic rotation with one side of the pelvis retracted or externally rotated and the contralateral pelvis protracted or internally rotated. Finally, there may be abnormal rotations at the hip, knee and ankle joints during gait as well.
During observational gait analysis, the focus for identifying rotational abnormalities is usually on foot progression (the orientation of the foot to the direction of progression) and the position of the knees. That is, if the knees are pointing inwards, it is assumed that there is internal hip rotation and/or femoral anteversion. Gait analysis can document segment and joint motion in the transverse plane to allow accurate identification of the location of rotational abnormalities, including pelvic motion, which can be difficult to determine visually.
A treatment approach based on a reasonably symmetrical clinical assessment of the rotational abnormalities and visual impression of symmetry in gait may result in an unexpected treatment outcome. This may help explain some of the unpredictability in surgical outcomes in the patient with cerebral palsy in which surgical decisions were made without a pre-operative gait analysis being performed. One of the most common problems observed in a patient with cerebral palsy is a drop foot in late swing. In some cases, the foot or toe may contact the ground in swing, resulting in reduced stability and possible falling. Drop foot creates a less stable position of the foot on landing, referred to as a toe initial contact. The primary cause of drop foot is generally thought to be excessive equinus in swing due to tibialis anterior muscle weakness, and/or ankle plantar flexor tightness or spasticity. In those patients, where normal or at least a neutral passive range of motion is possible, an ankle-foot orthosis is often prescribed.
During observational gait analysis, when a drop foot is suspected, all too often, the observer concentrates on the orientation of the foot in late swing and at initial contact, (the foot is pointed downward in swing resulting in a toe contact). A common error in these circumstances is to presume that this orientation is due to ankle position alone, that a plantar-flexed ankle only causes the foot to point downward. It is important in cases such as these to appreciate not only the role of the ankle, but also that of the knee in positioning the foot segment, which is readily identified when using quantitative clinical gait analysis.
II. Indications of the associated muscle activity
Although dynamic EMG has its limitations (ie, the amplitude information is limited unless directly related to a known force [15]), this technique is the only way to determine whether a particular muscle is active during gait [16]. One can usually predict that a group of muscles is active, such as the knee extensors in a patient in crouch. However, the entire muscle group may not be active. In the majority of patients with cerebral palsy, the rectus femoris is active in mid swing and during the Duncan Ely test, but the vastus medialis and lateralis are not [13]. Similarly, to determine the cause of hind foot varus, all the potential contributors need to be assessed [4]. An examination of EMG data in conjunction with the joint kinetics can also provide more information about the cause of internal joint moments.
Determining posterior tibialis activity during gait
One common problem in cerebral palsy of the spastic hemiplegia type is varus deformity of the hind foot. Intramuscular (fine-wire) EMG helps determine the possible role of the tibialis posterior muscle in producing this deformity.
Without understanding the potential causes of the deforming forces and associated abnormal motion, treatment decision-making can be, at best, an educated guess. Electromyographic data can provide information about possible contributors to the abnormal motion. These data, in combination with joint motion and kinetics, can help determine whether deforming forces are associated with the abnormal EMG.
III. Indications of the associated joint kinetics
One of the more common problems experienced in ambulatory patients with myelomeningocele at the L4 or L5 functional level, is a knee valgus thrust during the initial weight-bearing phase of the gait cycle [17]. It is believed that this motion must compromise the medial soft tissue structures of the knee over time. The most common treatment for this problem is the knee-ankle-foot orthosis (KAFO) which is meant to protect the medial knee [18].
The body's response to the valgus thrust at the knee is a net knee adductor moment. Joint kinetic data, specifically the net knee coronal plane moment in-stance, would substantiate the presence of a knee valgus thrust; that is, the net internal knee moment would be an adductor moment.
IV. An opportunity to learn from documented treatment outcome
In many laboratories, a routine part of clinical gait analysis is to re-evaluate each preoperative patient about a year after surgery. At this time, the preoperative test procedures are repeated, so that comparisons can be made. The clinician becomes more aware of the specific outcomes related to the patient and can begin to understand the complex relationships between primary, secondary and compensatory gait abnormalities. The wealth of knowledge that has accumulated over time using this systematic approach for the treatment of gait abnormalities in cerebral palsy is phenomenal (as evidenced by the body of literature cited).
This systematic approach also has other benefits. The quantitative nature of gait analysis facilitates prospective clinical research, and the development of a large database of pre- and postoperative analyses facilitates retrospective research. Routinely doing postoperative gait analyses enables the systematic evaluation of the effects of surgery on specific populations, or the outcomes of specific procedures. This has led to many beneficial changes in the approach to surgical treatment of patients with cerebral palsy. The approach allows an increased understanding of the ramifications of certain procedures, such as gastrocnemius lengthening [19] and the surgical treatment of equinovarus foot deformities [20]. Gait analysis techniques have resulted in the development of the rectus femoris transfer [21, 22, 23], an understanding of the difference in effectiveness of the rectus femoris transfer as compared with the rectus femoris release [24], and an appreciation of the significance of the location of distal rectus transfer site [25]. It has also led clinicians away from specific procedures, such as the hip adductor transfer [26]. Another benefit of routinely implementing gait analysis is that it provides a means to directly assess the effects of similar procedures, such as the medial hamstring versus medial and lateral hamstring lengthening [27] and hamstring lengthening with [22] or without a simultaneous rectus femoris procedure [28], on functional outcome.
Which patients can benefit from a clinical gait analysis?
Quantitative clinical gait analysis techniques are appropriate for any adult or child who has a gait problem that requires treatment. Because of the complexity of gait abnormalities in neuromuscular disorders, gait analysis is most commonly performed in this patient population. Gait analysis is appropriate for guiding decision-making on management in such disorders as cerebral palsy, stroke, traumatic brain injury and myelomeningocele, among others. Because of the complexity and expense of the test, gait analysis is primarily used as part of the surgical decision-making process when all conservative treatments have been exhausted and surgical intervention is being considered. However, gait analysis is not limited to this application only. Questions concerning bracing issues and medication efficacy can be addressed using gait analysis techniques. For example, is the brace performance or drug intervention (ie, Botulinum toxin, baclofen) consistent with the prescriptive objectives? Evaluation of the rate of deterioration in progressive disorders that affect gait can also aid in understanding a patient's abilities and directing countermeasures. As described above, another valuable function of gait analysis is assessing the efficacy of surgical intervention. Routine analyses of postoperative functional status provides the clinician with more objective information to evaluate the effects of treatment as well as a basis for determining the next steps in the treatment plan.
A number of factors must be considered when referring a patient for gait analysis. At many centers, the patient must be ambulatory, with or without assistive devices, for at least 10 consecutive steps. The patient must be able to follow simple directions and to behaviourally tolerate the placement of reflective markers and EMG electrodes on the skin. The level of patient cooperation influences testability, given the time required for a typical gait analysis, particularly in cases of severe cognitive impairment. If a patient has orthoses, testing with and without the devices may be required to address clinical questions concerning brace wear. Usually, testing is conducted with the patient using any necessary walking aids. A full gait analysis that includes all the above parameters takes approximately one to two hours.
Perhaps the most important consideration in using clinical gait analysis is the proper formulation of the specific questions to be addressed by the analysis. For example, what is the cause of the tripping/falling and what is the etiology of idiopathic joint pain? Such questions need to be asked to properly direct the application of the technology and the associated interpretation process. Certainly there is a temptation to believe that the technology, specifically, the computer, not only aids in the analysis, but can also direct the analysis. As illustrated throughout this article, the experience and knowledge of the professionals who collect and interpret gait data are essential to clinical gait analysis.
As previously mentioned, a referral for gait analysis is usually made when all methods of conservative treatment have been tried and surgical options are being considered. This typically occurs after the patient has reached an ambulatory plateau and/or when orthopedic concerns necessitate treatment (ie, hip subluxation or severe joint contractures). In patients with cerebral palsy, multi-level surgeries are now performed to address all dysfunction during one surgical intervention. This not only reduces a patient's exposure to anesthesia, but it also reduces the need for frequent hospitalizations and periods of rehabilitation. Gait analysis is invaluable in identifying the multiple areas of impairment that are difficult to understand by observation and clinical assessment alone. For example, when used as a preoperative tool, the child with cerebral palsy may often need only one surgical package of treatment during the growing years.
Summary
In summary, quantitative gait analysis provides the tools necessary to evaluate both normal and pathologic gait in a more objective fashion. The art of sophisticated clinical gait analysis lies in the integration of many methods of analysis to arrive at a more complete assessment of a patient's gait pattern. Proper gait data interpretation is dependent upon the care with which gait data are collected and the experience and expertise of the clinical team, which may include physicians, clinical scientists, physiotherapists, kinesiologists, engineers and technicians.
Summary of safety and clinical performance
Risks
Risk analyses compliant to ISO 14971:2019: Application of risk management to medical devices are completed for all product offerings. Copies are available upon request.
Exclusions: Not for use in an operating theatre, anesthetic gas or oxygen-rich environments. Not for use where there is a risk of compromising the general safety and performance of medical electrical equipment. Not suitable for use in high magnetic flux, ionizing radiation, sterile, or life- or safety-critical environments.
- The risks (from risk management and literature) have been addressed by the following clinical data:
None identified. There have been no Adverse Incident reports or risks identified in routine Post Market Surveillance reports in any country since the product launches in 2015 (Vantage system) and 2016 (Vero system). Supporting software has been in service since 2007. - All hazards and other clinically relevant information have been identified appropriately. They are as follows:
Misuse of software where measurement performance does not meet specification or misinterpretation of data.
Reasonably foreseeable misuse:
Use of a system in a way not intended by the manufacturer, but which can result from readily predictable human behaviour.
Readily predictable human behaviour includes the behaviour of all types of users, e.g. lay and professional users.
Reasonably foreseeable misuse can be intentional or unintentional.
The most likely risk is that the health professionals, biomechanists or medical practitioners are not anatomically competent to correctly place the markers using palpation, which may result in erroneous results that may affect therapeutic decision-making.
The second most likely risk is that the health professionals, biomechanists or medical practitioners are not clinically competent to interpret the information in therapeutic decision-making.
- The safety characteristics and intended use (purpose) of the device requires training of the end-user.
Yes - The safety characteristics and intended use (purpose) of the device requires the following precautions:
The devices use infrared/near infrared light to illuminate the markers. Photobiological safety calculations are made and published to minimize impact. This is achieved through notices in the supporting manuals and on the applicable equipment labels. - The foreseen users of the device are adequate. They are as follows.
Medical practitioners, orthopedic surgeons, clinical scientists, physiotherapists, kinesiologists, biomechanists, engineers and technicians
The equipment is not designed for use by lay persons or patients when meeting its intended purpose. - All training requirements and precautions are listed.
The devices use infrared/near infrared light to illuminate the markers. Photobiological safety calculations are made and published to minimize impact. Safe use is achieved through notices in the supporting manuals and on the applicable equipment labels.Clear guidance is provided through documentation and on-site user training prior to use. The Manufacturer provides post-installation and training, on-line and personal technical support, including review of data to minimize usage errors and incorrect interpretations of results.
Users are recommended to become members of the manufacturer agnostic ESMAC – European Society for Movement analysis in Adults and Children in Europe (esmac.org) and/or CMAS – Clinical Movement Analysis Societyof UK & Ireland (cmasuki.org) for clinical focussed training and education. Both societies offer laboratory accreditation, standards and courses.
The Software is not intended to replace the clinical skill of a medical practitioner or his/her independent professional judgement of individual clinical circumstances to determine a patient's treatment. The Software should only be used by those who have been appropriately trained in its operation, functions, capabilities and limitations, and in any event should not be relied upon, by itself, as the sole method of making any diagnosis or determining any treatment.
- There is full consistency between current knowledge/the state of the art, the available clinical data, the manufacturer's product information, and the risk management documentation for the device.
Yes - Summary of the total experience with the device, including numbers and characteristics of patients exposed to the device and duration of follow-up in:
- Other user experience: Through published literature
- Market experience: Through published literature including systematic reviews [29]
- Nature, extent/severity, probability, duration of benefits to the patients and of side effects and other risks.
No identified side effects - For each aspect of the intended use, whether the benefit/risk profile including its uncertainties is compatible with a high level of protection of health and safety, corresponding justifications.
The benefits of clinical gait analysis when drawing on quantifiable kinematic, kinetic and electromyographic data are summarized below. The independent conclusion presented is with the caveat that the effect of gait analysis on patient outcomes is less well established in the absence of a randomized controlled trial. However, multiple cohort comparisons and a case-control study strongly suggest that gait and functional outcomes are improved when treatment follows gait analysis recommendations in conjunctions with physical clinical assessments. The assessment in this report is that based on the presented peer reviewed evidence the benefits of gait analysis are positive. The review of the proposed risk controls in conjunction with post market surveillance and customer complaint and feedback evidence establishes that the overall Benefit-Risk Ratio is assessed not adversely affected by any residual risks.
Clinical gait analysis includes a physical examination, motion tracking of body segments (kinematics), recording of ground reaction forces (kinetics) between the feet and floor, and electromyography. Motions, forces, and muscle firing patterns are measured to assess the patient’s status and to develop an appropriate treatment plan. Each component of gait analysis testing can be performed separately, but the data are most useful when viewed together in a comprehensive evaluation.
Gait analysis allows for a more accurate assessment of gait deviations than visual gait assessment [30,31] to provide quantifiable information in the management of a patients with walking problems. A number of studies have demonstrated that gait analysis alters surgical decision-making and changes the treatment patients receive [32– 35]. The studies generally compare treatment plans without gait analysis to treatment plans for the same patients that do utilize gait analysis. Most studies have focused on the use of pre-operative gait analysis in surgical planning for children with cerebral palsy and other diagnoses or in patients with specific impairments like spastic equinovarus [33] One study examined post-operative treatments including bracing, physical therapy, and additional surgery [36]. In some studies, the two treatment plans being compared (with and without gait analysis) are proposed by the same clinician [32,33]. In other studies, the plan without gait analysis is proposed by a referring physician, and the plan with gait analysis is proposed by the gait laboratory team, which may or may not include the referring physician [34,35]. The findings have been consistent, regardless of the details of the study design.
The results of these studies indicate that the treatment plans with and without gait analysis differ in a high percentage of patients (52% to 89%) and procedures (40% to 51%) [32–36] In addition, in patients undergoing gait analysis there are changes between the initial treatment plan and the treatment ultimately performed. Two of these studies found that 37% to 39% of the procedures planned before gait analysis were not ultimately done, and 28% to 40% of the procedures actually done were not planned before gait analysis [34,35] The change in actual treatment is likely due, at least in part, to the addition of gait analysis since gait analysis recommendations are followed in a high percentage of patients (with 77% having an exact match between the surgeries recommended by gait analysis and the surgeries ultimately performed [37]) and specific surgical procedures (92% to 93%) [35,37].
Several studies have evaluated the effect of gait analysis on patient outcomes [38–43]. These studies generally compare outcomes between patients whose treatment followed gait analysis recommendations and patients whose treatment did not follow gait analysis recommendations. The results indicate better gait and functional outcomes when the treatment follows gait analysis recommendations. Specifically, function improves when surgery is done and is consistent with gait analysis recommendations, function is maintained when no surgery is done as recommended by gait analysis, and function deteriorates when surgery is recommended by gait analysis but not done.
The first study of this type graded outcomes as improved or not improved based on temporal and sagittal gait parameters in a small number (n=22) of children with spastic diplegic cerebral palsy [40]. Of 15 children who had surgery in accordance with gait analysis recommendations, 13 improved, and two did not improve because the outcome measures did not capture the impairment being addressed (rotational alignment). Of seven patients who did not have the recommended surgeries performed, two had surgeries similar to those recommended by gait analysis and improved, while the other five had surgeries different from the gait analysis recommendations and did not improve. This study provided the first indication that patients may have better outcomes when their treatment follows gait analysis recommendations.
Several recent studies have continued this line of investigation, comparing groups of patients with CP whose treatment followed gait analysis recommendations to different extents. Gough and Shortland [43] reported that outcome measures related to contracture and gait improved in children who had multilevel surgery as recommended by gait analysis, worsened in children who did not undergo surgery despite having surgery recommended by gait analysis, and remained stable in children who had no surgery as recommended by gait analysis. Filho et al. [39] observed improvement in gait in surgical patients whose surgery agreed, to some extent, with gait analysis recommendations. The significance of the improvement was related to the degree to which the gait analysis recommendations were followed, and no improvement was observed in patients who had surgical or non-surgical treatment that was completely different from that recommended by gait analysis. Lofterod et al. [41] reported satisfactory kinematic outcomes in pediatric gait laboratory patients who received surgical or non-surgical treatment consistent with gait analysis recommendations. These studies suggest that gait analysis is useful in defining indications for surgical and non-surgical treatment and that treatment following gait analysis recommendations is associated with better outcomes.
One study has compared outcomes during periods before and after gait analysis was added to the management protocol for children with cerebral palsy [44]. 122 two patients managed without gait analysis from 1985 to 1989 were compared against 170 patients managed with input from gait analysis from 1996 to 1997 (after the gait analysis equipment and methodology were fully established). The patients managed with gait analysis had a lower prevalence of surgery at all ages as well as a lower rate of multiple surgeries, suggesting that surgeries were delayed or avoided when gait analysis was included in the patient management protocol.
Finally, one case-control study matched 10 children with cerebral palsy who had surgery in accordance with gait analysis recommendations to 10 children who had the same surgeries recommended but no surgery done [38]. The children who were operated on as recommended by gait analysis had a significantly higher percentage of patients with positive outcomes based on surgery-specific kinematic criteria (44% vs. 26%, p<.0001), with an odds ratio for positive outcome of 3.7 (95% confidence interval: 2.0–7.0). Thus, the likelihood of a positive outcome was significantly greater when surgery was performed as recommended by gait analysis.
The impact of gait analysis on treatment decision-making is well established through multiple comparative studies and a recent randomized controlled trial. Gait analysis has two primary effects on decision-making: changing decisions when the gait analysis results disagree with the original treatment plan and reinforcing decisions when the gait analysis results agree with the original plan. Gait analysis influences both the physician’s diagnostic thinking and, ultimately, the treatment received by the patient.
The effect of gait analysis on patient outcomes is less well established in the absence of a randomized controlled trial. However, multiple cohort comparisons and a case-control study strongly suggest that gait and functional outcomes are improved when treatment follows gait analysis recommendations in conjunctions with physical clinical assessments.
The equipment is inherently safe as it does not make any contact with the patient except with hypoallergenic, latex-free wig tape and Micropore® tape to attach markers to skin. - Extent to which assessment of benefits is possible based on available data, limitations of the data, description of gaps, uncertainties, and assumptions.
Identified within systematic review [29] - Whether available data allows adequate assessment of performance, limitations of the data, gaps, and uncertainties.
Yes - Whether there is sufficient evidence for every intended performance.
Yes - Whether the data available is of sufficient amount and quality for the detection of side effects and their frequency, limitations of the data, description of gaps, uncertainties, and assumptions.
Yes - Whether the side effects are acceptable and corresponding justifications.
Yes, none identified - The benefit/risk profile according to current knowledge/the state of the art in the medical fields concerned and according to available medical alternatives is acceptable.
The intended use and corresponding risk reduction measures are adequate and the product information is suitable for the intended users and sufficiently covers all usability aspects.
Exclusions: Not for use in an operating theatre, anesthetic gas or oxygen-rich environments. Not for use where there is a risk of compromising the general safety and performance of medical electrical equipment. Not suitable for use in high magnetic flux, ionizing radiation, sterile, or life- or safety-critical environments.
Note: The overall system classification is defined by the highest risk device installed that may include the addition of approved third-party equipment such as electromyography apparatus by clients. - All claims foreseen by the manufacturer are identified and any discrepancy and gaps are fully covered by clinical data.
There is full consistency between the clinical data, the information materials supplied by the manufacturer and the risk management documentation for the device under evaluation. - Residual risks and uncertainties are sufficiently identified. The acceptability for CE-marking is sufficiently discussed and follow-up measures during PMS are addressed. (This includes uncertainties regarding medium- and long-term performance, safety under widespread use, residual risks such as side-effects and complications occurring at rates below detection possibilities of currently available clinical data, others).
Risks and uncertainties are already addressed in ongoing PMS activities (eg, in currently ongoing reviews in the literature).
Performance characteristics of the device
Performance characteristics
Measurement definitions applied
Within this instruction, accuracy is defined as to how close measurements are to a known true value, while precision refers to how close measurements are to each other. In other words, accuracy describes the difference between the measurement and actual value, while precision describes the variation observed when measures of the same marker location or parameter are repeated with a Vicon motion capture system. Precision is described by two sub-components:
- Repeatability: The variation observed when the same system measures the same location or parameter repeatedly.
- Reproducibility: The variation observed when different systems measure the same location or parameter repeatedly.
Soft tissue artifact
The engineering and physics problem of capturing and tracking 3D points in space has been solved and well understood within Vicon motion capture systems. However, clinical concerns remain over the loose association between the measurements of points on the skin surface and the underlying bone, commonly described as the soft tissue artefact [47]. Challenges also remain in reliably capturing bony landmark axial rotation, in particular, of the thigh [48].
Due to inaccuracies related to working with biological systems [49], there are limitations in the way 3D motion data are acquired. Markers attached to the skin move with respect to the underlying bones that they are intended to represent. Soft tissue artifact (STA) arises from movement or deformation of the subcutaneous tissues associated with muscular contractions, skin movement and inertial effects. The extent of STA for any movement depends upon the physical characteristics of individuals, marker locations and the nature of the movement task performed.
Many researchers and gait laboratories have proposed techniques to move away from existing predictive approaches by instead discovering joint centers and axes functionally, and fitting the data to an idealized joint model that also incorporates some form of soft tissue artifact compensation. This work continues and, like the earlier innovations, will gain wide acceptance only after it has been validated through close collaborative efforts between clinicians, scientists and engineers in laboratories, academia and industry.
To ensure where possible that spatio-temporal marker measurement artifact is not introduced into the wider problem, Vicon motion capture systems are designed to achieve performance in all variants to always be below the anticipated soft tissue artifact. The performance upper limit is defined within the published Declaration of Conformity and is common for all published CLASS Im product offerings.
Charlton et al [47] estimated that when developing human lower limb biomechanical models, marker location covariance was estimated to be 10 mm2 in all coordinate directions.
Peters et al [49] undertook a systematic review to critically evaluate the quantification of STA in lower limb human motion analysis. It has a specific focus on assessing the quality of previous studies and comparing quantitative results. A specific search strategy identified 20 published articles or abstracts that fulfilled the selection criteria. The quality of the articles was evaluated using a customized critical appraisal tool. Data extraction tools were used to identify key aspects reported in the articles. Most studies had small sample sizes of mostly young, slim participants. Eleven of the reviewed articles used physically invasive techniques to assess STA. STA was found to reach magnitudes of greater than 30 mm on the thigh segment, and up to 15 mm on the tibia. The range of soft tissue artifact reached greater than 25 mm in some cases when comparing the results of reviewed studies.
Information allowing the healthcare professional to verify if the device is suitable
Selection and verification of device suitability
Independent protocol for quantifying the accuracy of motion analysis systems
The Gait and Clinical Motion Analysis Standards Council (GCMAS) has proposed a protocol for quantifying the accuracy of a motion analysis system (ie, how accurate the system is at locating markers). This Standard Assessment of Motion System Accuracy protocol (SAMSA) is intended to test video-based systems that employ reflective markers.
SAMSA uses a simple device based on an earlier design used by Jim Richards to compare motion systems [50]. This device consists of a beam fitted with markers and rotated at 60 RPM by a motor. The protocol is designed to test the ability of a motion system to (1) track moving markers; (2) resolve markers using a subset of the cameras; and (3) resolve markers that pass close to one another during a trial. The protocol has been tested in the laboratories of seven Standards Committee members and the results have been used to formulate an accuracy standard in the form of acceptable error thresholds. This testing and the error thresholds were presented at the 2007 GCMAS Meeting in Springfield [51] and found to be between 0.21–3.50 mm Mean; 0.08–3.86 mm SD, independent of equipment supplier.
Independent static and dynamic performance evaluation of a Vicon system
Merriaux et al [52] used a very similar apparatus to study the positioning performance of an eight-camera Vicon T-Series system. Their protocol included evaluations of static and dynamic performances. Mean error, as well as positioning variabilities, were studied with calibrated ground truth setups that are not based on other motion capture modalities. They introduce a new setup that enables directly estimating the absolute positioning accuracy for dynamic experiments, contrary to state-of-the art works that rely on inter-marker distances. The system performed as expected on static experiments with a mean absolute error of 0.15 mm and a variability lower than 0.025 mm. The dynamic experiments were carried out at speeds found in real applications. The work suggests that the system error is less than 2 mm. The authors also reported that marker size and Vicon sampling rate must be carefully chosen with respect to the speed encountered in the application in order to reach optimal positioning performance that can go to 0.3 mm for the dynamic study.
ASTM Standard E304-16 Test method for evaluating the performance of optical tracking systems that measure six degrees of freedom (6DoF) pose
ASTM has recently published a standardized test method that presents metrics and procedures for measuring, analysing, and reporting the relative pose error of optical tracking systems that compute the pose (ie, position and orientation) of a rigid object while the object is moving. Following their protocol [52], experimental results using a 12-camera Vicon system confirmed that distance errors lay in most data at below ± 0.5 mm and angle errors < 0.36°, consistent with the findings of Bostelman et al [53], using a system from another supplier (Optitrak).
Degree of accuracy claimed for all generic devices
Performance characteristics independent of type and configuration
Measurement criteria
Supporting software: Nexus 2.11 or later
Motion capture reconstruction resolution
Using a minumum of four optical motion cameras, resolution of the distance between the centers of two static 14 mm spherical markers located within a volume not less than 4 m x 4 m x 1.5 m to within 1 mm mean; 1 mm Standard Deviation; sample size no less than 1,000.
This equates to one order of magnitude (1 mm3) better than reported skin movement artifact 10 mm3 [47].
Analogue digital conversion
Resolution to ± 10 mV mean and ± 10 mV (1 Standard Deviation)
Outputs from 3rd Party Kinectic and Electromyographic devices is ± 5 V to ± 10 V. Measurement artifact is assessed at 0.2–0.1% error.
Synchronization
Difference within one video frame
Clinical gait analysis is captured at 120 frames.sec-1 which equates to 8.3 m sec-1, maximum potential Motion-Analogue temporal difference.
Details of any preparatory treatment or handling of the device before it is ready for use
Device preparation
Please refer to the supplied user guides for the selected device to prepare the equipment for use. Sterilization and disinfection is not required as the device is excluded for use in these environments.
Facilities and user training
Facilities and user training
Please refer to the supplied user guides.
Clinical gait analysis systems using Vicon motion capture systems and any approved third-party devices or equipment are fixed installations.
Clear guidance is provided through documentation and on-site user training prior to use. The Manufacturer provides post-installation and training, on-line and personal technical support including review of data to minimize usage errors and incorrect interpretations of results.
Users are recommended to become members of the manufacturer-agnostic ESMAC – European Society for Movement analysis in Adults and Children in Europe (esmac.org) and/or CMAS – Clinical Movement Analysis Society of UK and Ireland (cmasuki.org) for clinical focussed training and education. Both societies offer laboratory accreditation, standards and courses.
Gait laboratory staff competencies
A typical gait analysis test can take from one to two hours, depending on the particular evaluations performed and on the cooperation, behaviour, and gait complexity (ie, involvement) of the patient. Usually, a clinical scientist, physiotherapist or kinesiologist works directly with the patient, and a more technically oriented person, such as an engineer or technician, manages the computer and measurement system operation during the test.
Institutional standards
It should be noted that not all clinical gait laboratories operate in this fashion. Some do not have the technology to provide three-dimensional body marker data and analytical processes that produce three-dimensional joint rotations (flexion-extension, abduction-adduction, and internal-external rotation) for interpretation. These clinical gait analysis laboratories use less sophisticated technology that collects and processes motion data based on the assumption that all of the rotations occur in the sagittal plane of the body. This assumes that all motions associated with gait can be appreciated from a side view of the patient. While this might not be unreasonable in the analysis of normal ambulatory motion (except perhaps for ankle/foot motion), it is clearly ill-advised for clinical decision-making in cases of pathological gait where three-dimensional motion is commonplace [54].
Moreover, at other facilities, a clinical gait analysis might be limited to a video recording and the measurement of certain gait stride and temporal parameters such as velocity, cadence, stride length, step length and percentage of stance/swing. While the video record is a useful tool in developing and substantiating visual impressions, it is inappropriate to "measure" joint and segment gait kinematics directly from the two dimensional video imagery, even though some commercially available hardware and software products do this. With respect to stride and temporal parameters, these are "outcome" measures and provide an indication of the level of function when compared to normal values. However, they do not give an indication of the cause of the gait abnormality and are, consequently, of limited value in clinical decision-making.
Similarly some laboratories capture only kinematic data so do not have access to the additional insights of kinetic information in their treatment decision-making.
Verification the device is ready to perform safely and as intended
Device verification
Please refer to the supplied user guides for the selected device for:
- Information needed to verify whether the device is properly installed and is ready to perform safely and as intended
- Information on identification of any consumable components and how to replace them
- Information on any necessary calibration to ensure that the device operates properly and safely during its intended lifetime
Use with third-party approved equipment and devices
Use with third-party equipment and devices
Please refer to the supplied user guides for the selected device for:
Information to identify such devices or equipment, in order to obtain a safe combination
Information on any known restrictions to combinations of devices and equipment.
Warnings, exclusions and precautions
Warnings, exclusions and precautions
Please refer to the supplied user guides and Declaration of Conformity for the selected device to address:
- The devices use infrared/near infrared light to illuminate the markers. Photobiological safety calculations made and published to minimize impact. This is achieved through notices in the supporting manuals and on the applicable equipment labels.
- Not for use in an operating theatre, anesthetic gas or oxygen-rich environments. Not for use where there is a risk of compromising the general safety and performance of medical electrical equipment. Not suitable for use in high magnetic flux, ionizing radiation, sterile, or life- or safety-critical environments.
- Emissions and immunity to electromagnetic interference standard compliance are listed within the applicable user guide. Full test reports are available on request.
Serious incident reporting
Serious incident reporting
A notice to the user and/or patient that any serious incident that has occurred in relation to the device should be reported to the manufacturer and the competent authority of the Member State in which the user and/or patient is established. Guidance is located within the regulatory compliance chapters in all user guides and in the Regulatory Information section of the Vicon website.
Information technology security
Information technology security
The system is connected to a dedicated local personal computing device and is managed by executable software within a third-party operating system. All information technology security of assets is at the full discretion of the user and out of scope for the manufacturer.
Date of issue of instructions for use
Instructions for use date of validity
From 8th February 2021
References
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Annex A: Description and meaning of applicable symbols
Standard/Source | Symbol | Reference | Title of Symbol | Description |
---|---|---|---|---|
BS EN ISO 15223-1:2016 | 5.1.1 | Manufacturer | Indicates the medical device manufacturer as defined in applicable medical device regulations. | |
BS EN ISO 15223-1:2016 | 5.1.2 | Authorized representative in the European Community | Indicates the authorized representative in the European Community. | |
BS EN ISO 15223-1:2016 21 CFR Part 801.18 (applies to date format) | 5.1.3 | Date of manufacture | Indicates the date when the medical device was manufactured. | |
BS EN ISO 15223-1:2016 | 5.1.6 | Catalogue Number | Indicates the manufacturer’s catalogue number so that the medical device can be identified. | |
BS EN ISO 15223-1:2016 | 5.1.7 | Serial Number | Indicates the manufacturer’s product serial number so that the unique medical device can be identified. | |
BS EN ISO 15223-1:2016 | 5.2.7 | Non-sterile | Indicates a medical device that has not been subjected to a sterilization process. | |
BS EN ISO 15223-1:2016 | 5.2.8 | Do not use if package is damaged | Indicates a medical device that must not be used if the package has been damaged or opened | |
BS EN ISO 15223-1:2016 | 5.3.3 | Protect from heat and radoioactive sources | Indicates a medical device that needs protection from heat and radioactive sources. | |
BS EN ISO 15223-1:2016 | 5.3.4 | Keep dry | Indicates a medical device that needs to be protected from moisture. | |
BS EN ISO 15223-1:2016 | 5.3.7 | Temperature Limit | Indicates the temperature limits to which the medical device can be safely exposed. | |
BS EN ISO 15223-1:2016 | 5.3.8 | Humidity | States the range of humidity to which the medical device can be safely exposed. | |
BS EN ISO 15223-1:2016 | 5.4.5 | No Latex | Indicates no latex in the medical device. | |
FDA ASTM F2503 | NA | MR Unsafe | Indicates a medical device that must not enter the MRI scanner room. | |
BS EN ISO 15223-1:2016 | 5.4.3 | Consult instructions for use | Indicates the need for the user to consult the instructions for use. |