Analysis Protocols. Oxford Foot Model Protocol

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1 Analysis Protocols Oxford Foot Model Protocol

3 CONTENTS INTRODUCTION OXFORD FOOT MODEL 1 Subject preparation pag 03 2 Acquisition phase pag 07 3 Elaboration phase pag 07 4 Reporting phase pag 09 5 Checking the markers location pag 10 Bibliography pag 10

4 INTRODUCTION The study of posture and movement in patients with pathologies associated with motor alterations can give very important information on the level of functional limitation resulting from their dysfunction and its evolution over time. Furthermore, this study can supply relevant data for the assessment of rehabilitation strategies aimed at the recovery of functional limitations related to specific disorders. Walk is one of the most significant gaits for investigating patients motor ability, as it is a very complex movement involving the synergy of different joints and refined interactions between muscles and joints. Gait analysis has great importance for the identification of patients walk features and degree of dysfunction. This result can be achieved with the, the clinical tool for walk functional analysis. is a powerful, modular and scalable solution based on fully integrated equipment: it is the only system providing native integration of kinematics, kinetics and surface electromyography all in one device. In addition to high-resolution, high-frequency and intelligent infrared cameras, digital 3D force plates and wireless electromyography, the system is also equipped with a set of scientifically approved clinical protocols. Each protocol allows clinicians to evaluate patients joints movement, muscle activity and energy distribution on a support surface while walking. Protocols provide a multimedia report including spatio-temporal parameters, and joints kinematics and kinetics evaluated during the different phases of gait cycle. Some of the analyzed variables are compared to normative data, in order to obtain a full understanding of possible movement compensation activities on the different anatomical planes and to identify successful follow up treatments. This booklet provides guidelines on the correct use of the Oxford Foot Model protocol. The user is guided step-by-step from patient preparation to data processing and reporting. 2

5 OXFORD FOOT MODEL Protocol overview: the Oxford Foot Model protocol is provided with the BTS SMART- Clinic software included with the system. This protocol allows the study of the foot kinematics during human locomotion, along with the electrical activity produced by the muscles involved in gait. The protocol was developed to provide physicians with quantitative and objective data needed to analyse foot and ankle pathologies. The foot model implementation was based on the work of (Stebbins et al. 2006; Carson et al. 2001) and consists of three segments: the hindfoot (including the talus and calcaneus), the forefoot (including the cuneiforms and metatarsals) and the hallux (proximal phalanx of the hallux). Required equipment: the protocol requires the use of a BTS SMART-DX system with a minimum of 8 video cameras for the kinematic analysis. The evaluation of the muscular activity requires the use of the BTS FREEEMG surface electromyogram. 1 Subject preparation Anthropometric measurements: the height of the patient [cm] needs to be measured. Markers: two versions of the protocol are available, both of which require the positioning of 32 markers on the subject s body: 6 on each shank and 10 on each foot: > Oxford Foot Model CALM : uses a marker placed on the sustentaculum tali (cal m) for the definition of the hindfoot segment (Figure 1). We suggest selecting this version of the protocol if the patient has no particular foot deformation (a correct positioning and a good visibility of the marker are allowed during gait). Figure 1: Frontal and lateral view of the Oxford Foot Model CALM marker set. The green markers must be removed before acquiring the Walking tasks (see Paragraph 2 - Acquisition phase ). 3

6 > Oxford Foot Model CPEG : uses a wand marker placed on the posterior aspect of calcaneus (cpeg) for the definition of the hindfoot segment (Figure 2). We suggest choosing this version of the protocol, if a proper identification of the sustentaculum tali cannot be achieved or if the landmark visibility is compromised during the subject s locomotion. Figure 2: Frontal and lateral view of the Oxford Foot Model CPEG marker set. The green markers must be removed before acquiring the Walking tasks (see Paragraph 2 - Acquisition phase ). The markers must be applied while the subject holds an orthostatic position. For the correct positioning of the markers, please refer to the following guidelines: > Shank: one marker on the lateral femoral condyle (r knee 1 l knee 1). To locate the femoral condyle, perform a passive flexion-extension of the subject s knee. Once the flexion-extension axis has been identified, find the point where the axis passes through the lateral part of the knee. If a dermographic pencil is available, mark the just found point, and verify that the skin displacement effect is minimal. One marker on the head of the fibula (r knee 2 l knee 2), which can be identified through palpation, another one on the most anterior aspect of the tibial tuberosity (r tub l tub), and one more placed arbitrarily along the anterior crest of the shank (r shin l shin). Finally, one marker on the lateral malleolus (r mall l mall) and one on the medial malleolus (r mall m l mall m). > Hindfoot: one marker on the lateral calcaneus (r cal l cal). This marker must be positioned at the same distance from the most posterior point of the calcaneus as the sustentaculm tali landmark. The sustentaculm tali should be palpable as a small ridge about 2.5 cm below (distal to) the tip of the medial malleolus (or about 2.5 cm posteriorly to the navicular tuberosity). Two markers on the posterior aspect of the calcaneus, specifically one on the distal end of the midline in the sagittal plane (r heel l heel) and one on the proximal end of the same line (r pcal l pcal). If the Oxford Foot Model CPEG version is selected, a marker mounted on a little bar (r cpeg l cpeg) needs to be placed midway between the two previously mentioned markers (the three markers must be collinear) (Figure 3). It is crucial that these three markers are in line with the sagittal plane of the hindfoot. 4

This plane is defined as the plane equidistant from both lateral and medial borders of the surface of the posterior calcaneus and passing by the midpoint between the sustentaculum tali and the

7 This plane is defined as the plane equidistant from both lateral and medial borders of the surface of the posterior calcaneus and passing by the midpoint between the sustentaculum tali and the lateral border of the calcaneus (Figure 4). If the Oxford Foot Model CALM version is used, one marker needs to be placed on the sustentaculum tali (r cal m l cal m). The correct placement of the lateral calcaneus and sustentaculum markers is critical for the correct quantification of the hindfoot rotations (Figure 5). Figure 3: To achieve an accurate reconstruction of the hindfoot rotations with the Oxford Foot Model CPEG protocol, the markers on the posterior calcaneus should be positioned along the midline of the posterior surface of the calcaneus (equidistant from both lateral and medial borders of the surface). Figure 4: The correct alignment of the rigid bar (r cpeg l cpeg) with the hindfoot sagittal plane (in blue) is critical to achieve an accurate reconstruction of the hindfoot rotations with the Oxford Foot Model CPEG protocol. The sagittal plane is defined as the plane equidistant from both lateral and medial borders of the surface of the posterior calcaneus and passing by the midpoint between the sustentaculum tali and the lateral border of the calcaneus. Figure 5: To obtain a correct reconstruction of the hindfoot rotations with the Oxford Foot Model CALM protocol, the marker on the lateral calcaneus must be positioned at the same distance from the most posterior point of the calcaneus as the sustentaculm tali marker. 5

> Forefoot: one marker on the head of the first metatarsal (r met 1h l met 1h) and one on the head of the fifth metatarsal (r met 5h l met 5h).

If the markers are correctly positioned, their centres will fall on the line through the first and fifth metatarsal heads.

8 > Forefoot: one marker on the head of the first metatarsal (r met 1h l met 1h) and one on the head of the fifth metatarsal (r met 5h l met 5h). These markers must be placed medially and laterally on the foot, respectively. If the markers are correctly positioned, their centres will fall on the line through the first and fifth metatarsal heads. Looking at the subject from a sagittal point of view, the markers on the distal calcaneus and on the fifth metatarsal head should be placed at the same height and should identify a line parallel to the sole of the foot (Figure 6). One marker placed laterally over the base of the fifth metatarsal (r met 5b l met 5b); another marker positioned at the base of the first metatarsal (r met 1b l met 1b), just medial to the extensor hallucis longus tendon. To palpate the tendon, ask the subject to dorsiflex the hallux. One last marker needs to be placed in the space between the heads of the second and third metatarsals (r met l met) (Figure 7). Figure 6: For a correct reconstruction of the foot dorsi-plantarflexion angle (monosegment foot), the line between the marker on the distal calcaneus and the marker on the fifth metatarsal head must be parallel to the sole of the foot. Figure 7: Top view of the positions of the foot markers according to the Oxford Foot Model CALM (left) and Oxford Foot Model CPEG marker sets (right). The green markers must be removed before acquiring the Walking tasks (see Paragraph 2 - Acquisition phase ). > Hallux: one marker on the medial side of the proximal phalanx, midway between the superior and inferior surface of the hallux (r hallux l hallux). Electrodes: in order to evaluate the muscular electrical activity, two electrodes need to be placed on each muscle of interest. Correct electrode positioning for the EMG analysis is available in specific handbooks (Cram et al. 1998, Freriks et al. 1999). During the preparation of the subject it is important to pay attention to the correspondence between the probe number and the muscle. 6

9 2 Acquisition phase The subject is asked to perform two different tasks: Standing task: the subject needs to hold a static orthostatic position for at least 3-5 seconds. Walking task: before performing this task, the markers on the head of the first metatarsal, on the posterior proximal aspect of the calcaneus (r pcal l pcal) and on the medial malleolus, must be removed. The subject needs to walk normally across the working volume defined during the calibration phase of the optoelectronic system. If a walkway is present, the subject is facilitated in following a gait direction. Otherwise, verify that the subject walks in the straightest way possible. The markers placed on the subject must be clearly within the field of view of the cameras during the whole acquisition. The protocol requires a single acquisition while the subject performs the Standing task and at least one acquisition during a Walking sequence. Recommendations: before starting any acquisition, correct calibration of the system must be verified. We suggest carrying out a calibration each day of use. Once the markers have been placed on the subject, their correct location should be verified (see Paragraph 5 - Checking the markers location ). 3 Elaboration phase The elaboration phase includes the following steps: Tracking: firstly, the markers must be tracked. Meaning that they need to be associated to their corresponding label, on the basis of each marker s real position, at every point in time. (Figure 8). Figure 8: Marker set models for the Oxford Foot Model CALM (left) and Oxford Foot Model CPEG (right) protocols. 7

10 Calculation protocol selection: the drop-down menu offers two different calculation protocols for selection choice: > Proc_OxfordFoot_Standing_CALM or Proc_OxfordFoot_Standing_CPEG : this protocol allows the evaluation of the joint angles of the subject performing the Standing task immediately after the acquisition phase (see Paragraph 5 - Checking the markers location ). > Proc_OxfordFoot_CALM or Proc_OxfordFoot_CPEG : used to compute the kinematic parameters and to elaborate the electromyographic signals. Events: as soon as the elaboration starts, the user is asked to identify the following gait events: > erhs = Right Heel Strike Right foot initial ground contact (at least two events must be defined) (Figure 9). Figure 9: Example of definition of the right foot initial contact with the floor (yellow ochre). To help with the identification, the shank-hindfoot dorsiplantarflexion angle (red) is shown. > erto = Right Toe Off Right toes are lifted off the ground (one event between each of the two previously defined strikes) (Figure 10). Figure 10: Example of definition of the time instant in which the patient lifts his/ her right toes off the ground (yellow ochre). To help with the identification, the shankhindfoot dorsi-plantarflexion angle (red) is shown. Moreover, the previously defined heel strike events can be displayed on the graph (light blue). > elhs = Left Heel Strike - Left foot initial ground contact (at least two events must be defined) (Figure 11). Figure 11: Example of definition of the left foot initial contact with the floor (yellow ochre). To help with the identification, the shankhindfoot dorsi-plantarflexion angle (red) is shown. > elto = Left Toe Off - Left toes are lifted off the ground (one event between each of the two previously defined strikes) (Figure 12). Figure 12: Example of definition of the time instant in which the patient lifts his/ her left toes off the ground (yellow ochre). To help with the identification, the shankhindfoot dorsi-plantarflexion angle (red) is shown. Moreover, the previously defined left heel strike events can be displayed on the graph (light blue). 8

11 If different Walking acquisitions are loaded, several windows will open progressively to define the events of all trials. 4 Reporting phase The results of the elaboration are ready to be visualized in the report. To create a report, the normative bands relative to the kinematics and EMG activity must be provided. Depending on the age of the subject it is possible to choose between two default normal bands: Gait-Normal-adults and Gait-Normal-children. Four report models are available (for a better understanding of the following report models description, please refer to the example PDF file of each report): Rep_OxfordFoot_Standing : see Paragraph 5 - Checking the markers location. Rep_OxfordFoot_Consistency : it must be selected before visualizing the final clinical report ( Rep_OxfordFoot ) to evaluate the consistency/repeatability of the acquisitions. Results of the kinematic analysis from each trial are shown in two distinct pages, one for the right foot, and one for the left foot. By using this visualization it is possible to scan the data and manually check for outlier trials (i.e. trials which deviate from the subject s characteristic pattern of gait). In the best case, where no outlier trials are detected, as well as in case one or more trials present inconsistent deviations, the current report should be closed. Then the Rep_OxfordFootModel must be selected, making sure that consistent trials only, are loaded. Rep_Gait_EMG : this report shows EMG signals (millivolts) filtered with a band pass filter ( Hz), with respect to time (seconds). The vertical solid lines in the graphics indicate the beginning and the end of the gait cycles defined during the elaboration phase. The vertical dotted lines represent the toe-off events. The lines related to the right cycle are green, while the ones related to the left cycle are red. All EMG records are displayed for each acquisition selected in Trials to be reported or viewed. Rep_OxfordFoot : the final clinical report is organized in the following way: > The first page contains the mean spatio-temporal parameters of all trials selected in Trials to be reported or viewed. These parameters are shown next to the normative data. The list of acquisitions used for the statistical analysis is also presented. > In the next page are reported the values of the kinematic parameters measured during the Standing acquisition. > Next, the results of the kinematic analysis are presented. The measurement unit used in the graphics is the degree (y-axis) and percentage of the gait cycle (x-axis). The mean curves for each limb (green for the right limb, and red for the left one) are visualized. The vertical dotted lines in the graphs identify the toe-off events, while the horizontal lines represent the Standing values. The above-mentioned lines are green for the right limb and red for the left limb. To qualitatively evaluate these graphs we suggest referring to the patterns presented in the work of (Stebbins et al. 2006). > Finally, EMG signals (millivolts) are presented. EMG average envelopes are shown, time-normalized for the duration of the gait cycle (% gait cycle). In addition, one page is dedicated per acquisition to the filtered EMG signals normalized on the first gait cycle for the right and left side. The vertical lines in the graphs indicate the heel strike event of the contralateral limb. The vertical dotted lines represent the toe-off events (green for the right limb, red for the left limb). The horizontal 9

12 black bars identify the EMG normal activation for the specific muscle. By default only the EMG signal corresponding to the first step identified in each acquisition is shown. The report can be customized to show EMG signals corresponding to several steps. 5 Checking the markers location As soon as the Standing task is acquired, select the Proc_OxfordFoot_Standing_CALM or Proc_OxfordFoot_Standing_CPEG calculation protocol. This protocol calculates the joint angles held during the static pose. No temporal event needs to be defined. At the end of the processing please select the Rep_OxfordFoot_Standing report in which a table containing the estimated Standing angular values is shown. These data can be examined to evaluate the presence of atypical values, which can indicate improper marker positioning. An inaccurate positioning of the cpeg marker (for the Oxford Foot Model CPEG version) or of the cal and cal m markers (for the Oxford Foot Model CALM version) could, for example, lead to major offsets (> 7-10 degrees) in the frontal and transversal plane of shank-hindfoot or hindfoot-forefoot angles. Bibliography Stebbins J., Harrington M., Thompson N., Zavatsky A., Theologis T., Repeatability of a model for measuring multi-segment foot kinematics in children. Gait Posture, Vol. 23, No. 4, pp Carson M.C., Harrington M.E., Thompson N., O Connor J.J., Theologis T.N., Kinematic analysis of a multi-segment foot model for research and clinical applications: a repeatability analysis, Journal of Biomechanics, Vol. 34, No. 10, pp Freriks B., Hermens H.J., Merletti R., SENIAM: European Recommendations for Surface Electromyography, Roessingh Research and Development Publisher, Vol. 8. Cram J.R., Kasman G.S. Holtz J., Introduction to surface electromyography, Aspen Publishers. 10

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Copyright 2004, Yoshiyuki Shiratori. All right reserved.

Copyright 2004, Yoshiyuki Shiratori. All right reserved. Ankle and Leg Evaluation 1. History Chief Complaint: A. What happened? B. Is it a sharp or dull pain? C. How long have you had the pain? D. Can you pinpoint the pain? E. Do you have any numbness or tingling?