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DIFFERENCES CAUSED BY WEARING A PROSTHESIS TO THE SOUND LEG (GRF,HIP & KNEE ANGLE)

DEPARTMENT OF BIOMEDICAL ENGINEERING. FACULTY OF ENGINEERING. UNIVERSITY OF MALAYAKUEP 3131: BIOMECHANICS OF PROSTHETICSDIFFERENCES CAUSED BY WEARING A PROSTHESIS TO THE SOUND LEG (GRF,HIP & KNEE ANGLE)LECTURERS NAME : DR NUR AZAH HAMZAID by: NURUL AINI SAHARI KED090013 WAN NOR HAPSAH WAN ZAKARIA KED 09002022 DECEMBER 2011

INTRODUCTIONWalking is the most easy and convenient way to travel short distances. The free joint movement and suitable muscle force will results in efficient walk. As the body moves forward, one limb typically provides support while the other limb is advanced in preparation for its role as the support limb [3]. The gait cycle is comprised of 2 phases, stance phase and swing phase. However, the stance phase is consisting of 5 parts which are initial contact, loading response, midstance, terminal stance and preswing. Heel strike will represent the initial contact of heel to the ground. During the heel strike, the knee is extended, hip will flexed and ankle is neutral or slightly plantar flexed. While, during loading the knee flexes 15 degrees, hip will reduced in flexed and ankle is plantar flexed in about 15 degrees which is the energy-conserving mechanism [3]. At this stage, the body is slowly transferred to the heel and will result in the peak of the vertical force (Ground Reaction Force, GRF) [2]. Furthermore, during the first phase of stance, hamstring and ankle dorsiflexors remain active, while the quadriceps and gluteal muscles act during loading and throughout early midstance to maintain hip and knee stability [3]. During midstance, the knee is extended and ankle is in neutral position again. In this stage, triceps surae acts to control tibial advancement in order to prevent the tendency for the ankle to dorsiflex due to body weight and inertia. Double support is occurring at this stage where both feet are in contact with the ground. After that, terminal stance is taking over and starts the preswing where the knee is flexed and ankle plantar flexed. In these last phases of stance, the toes in which have been neutral, dorsiflex at the metatarsophalaneal joint. All the vertical force that acted during the stance phase can be seen in graph below.

After the 60% of gait cycle complete which is the stance phase, the swing phase is occur for other 40% of gait cycle. During the leg is swing, the ankle dorsiflexes by the concentric contraction of anterior tibialis muscle and all other muscles are silent. The momentum is generated by the gastrocsoleus and hip flexors at terminal stance move the leg forward. During the initial swing phase, knee is passively flexes and then passively extends at the end of the swing phase. The sub-talar joint is nearly in neutral position and toes are dorsiflexed slightly as foot prepares for the next of gait cycle (stance phase) once the toe off of the ground.Ideally, each gait cycle will generate identical ground reaction force (GRF) when walking on the flat surface [2]. However the GRF can be altered by the deviated walking gait. There are many reasons lead to deviation of walking gait. As in our project, the walking gait is altered by the transfemoral prosthesis of transfemoral amputee who amputated due to the osteosarcoma. In other way, ground reaction force can be used to assess prosthesis. A good prosthesis is the one that can imitate function and movement of normal limb as close as possible that will enable its user to walk with least energy expenditure and look natural when walking.A prosthesis is a device that designed to replace a missing part of the body. It is prescribed to people that experienced limb loss or amputated. Amputation is inevitable when it is the only solution in cases like osteosarcoma. Osteosarcoma is a type of bone cancer where the malignant tissue starts in bone. Most osteosarcoma arises from random and unpredictable errors in the DNA of growing bone cells during times of intense bone growth. Chemotherapy will be done to reduce the size of tumor followed by surgery to remove the tumor. A radical surgery such as amputation will be needed for more extreme cases. Once amputated patient will need a prosthesis to perform the activities that they able to do prior of amputation, such as walking. The subject who participated in this study is a cancer patient, affected with osteosarcoma almost one year ago. She had undergone the amputation to remove the tumor that affected her femur. Shes now walking again by wearing prosthesis.

OBJECTIVEThe study is conducted to see the differences caused by wearing prosthesis to the sound leg. We compare the ground reaction force produced by our subject that is wearing prosthesis to the other leg that is not wearing prosthesis to see whether the prosthesis is causing the normal limb to exert more or less force at different stage of stance phase. Other than that ground reaction force can be used to find out how the prosthesis is imitating normal sound limb in terms of force exerted to the floor when walking. Other than that, we would like to find out how wearing prosthesis would affect the sound leg in terms of knee and hip flexion, extension angles. We compare the knee and hip flexion and extension angle of the leg that is wearing prosthesis to the other leg that is not wearing prosthesis. We also compared the results to a published result to see whether the gait pattern of a prosthesis user deviates from a normal, able bodied person.METHODA cancer patient who had been wearing prosthesis for few months acted as the subject for this study. She is wearing transfemoral prosthesis with mechanical knee joint. During the experiment, she walked using sport shoes. 16 markers were placed over her lower limb. The markers for absent body parts such as right knee, right leg and right ankle were placed approximately using her sound leg as guide. The markers placement and detailed procedure is included at Appendix A.For the experiment, she required to walk over the force plate for 7 times to produce 7 trials. Breaks were given on interval of each trial. She experienced tiredness and shortness of breath after 2 trials. The results from all trials were then analyzed. The graphs from joint angles are plotted against the whole gait cycle while graph for GRF was plotted against percentage of stance phase.

SUBJECTDETAILS:Gender : FemaleAge : 27 years oldMass : 49 kgProsthesis weight: 5 kgHeight : 153.5 cmRight leg (cm) (amputate side)Left leg (cm) (sound limb)

Leg length7375

Knee width9.610.9

Ankle width7.16.1

RESULTS AND DISCUSSIONS

Push OffHeel StrikeToe OffMid StanceLoading ResponseFIGURE 1 PROSTHETIC LEG AND SOUND LEG GROUND REACTION FORCE FROM EXPERIMENTAs we can see in figure 1, at the vertical force during loading response of prosthetic leg is delayed approximately 7% of gait cycle than sound leg. This is because during double support phase which is starting with heel strike, the subject slowly doing loading response by transferring weight to heel. It takes longer time from heel strike to loading response than sound leg.

BACRED sound leg BLUE prosthetic leg GREEN body weightFIGURE 2At mid stance phase, the vertical force should be below the body weight as shown in figure 1 during the midstance phase of prosthetic leg. Figure 2 show the mid stance of sound leg has three curve of vertical force. At curve A the vertical force act like normal gait in which below the body weight. However, a transient force exerted higher than body weight as shown at curve B and the vertical force reduced below the line of body weigh at curved C. The sudden transient force created is due to the sudden force produced by hip to swing the prosthetic leg and lock it in extension. As we can see in figure 1, the vertical force will peaked again during push off of early terminal stance. The force is exerted due to the persons weight is entirely on one foot [2]. After that, the vertical force decreased to 0N back as the toe off the ground (force plate). However, once again we can see the vertical force of prosthetic leg reduces slowly to 0N. This show that the slow movement of the leg to toe off which indicate that the slow progression of terminal stance. Based on the Ground Reaction Force (GRF) graph in figure 1 mid stance phase of the prosthetic leg is shorter than the sound limb. This is because of the subject feel less stable to stand on the prosthetic leg. As we know, the patient is not regular walking by wearing the transfemoral prosthesis and still not comfortable with the prosthesis.

DELAYED SWING PHASE OF SOUND LIMBFIGURE 3: KNEE FLEXION/EXTENSION GRAPH FROM EXPERIMENT.

MAXIMUM FLEXION FIGURE 4: KNEE FLEXION/EXTENSION GRAPH OF NORMAL GAIT FROM PUBLISHED JOURNAL.As we can see in figure 3, the knee of the prosthetic leg does not present knee flexion during stance phase except at the end of stance phase in which at 57% of gait cycle. The subject experienced locking of the knee joint in knee extension position during stance phase for stability. During 57% of gait cycle, the knee of prosthetic leg starting to flex in order to do push off and toe off to start swing the ipsilateral leg in swing phase. The knee flexes to 37 at 70% of gait cycle and reduces flexion in order to start heel strike for next gait cycle. The knee starts extend at 81% of gait cycle. If we compare to the normal gait graph in figure 4, the prosthetic foot flex at maximum degree and starts extension during swing phase is faster than the normal gait. This is due to the fast movement of the auto lock system. The prosthesis is imitating the normal knee joint by locking the knee joint in extension during stance phase and only allows flexion for swing phase. For sound leg, knee joint does not present any extension for the whole gait cycle (stance phase and swing phase). This is because of the subject wants to gain stability counter the leg length discrepancy (prosthetic leg shorter than sound leg) in which acquired her to flex the knee of the sound leg. This is also due to the locking of the knee joint during stance phase of the prosthetic leg. Generally, if we lock one of our leg in knee joint, the other leg will automatically walk with knee flexion position to gain the stability during stance and swing phase. As we compare to the normal gait graph, there is no present of knee flexion in stance phase except at the end of the terminal stance which knee will slowly flex to do a toe off and starts swing phase of ipsilateral leg.Besides that, compare the swing phase of sound leg happen more late or delayed when we with the normal gait in figure 4 and also swing phase of prosthetic leg in figure 3. This is due to the slow progression in the loading response and terminal stance of the prosthetic leg which is occurring synchronically with the swing phase of the sound limb.

KNEE FLEXION/EXTENSION GRAPH

ABMinimum hip flexion (push off)FIGURE 5: HIP FLEXION/EXTENSION GRAPH FROM EXPERIMENT.RED LEFT GREEN - RIGHTFIGURE 6: HIP FLEXION/EXTENSION OF NORMAL PERSON GAIT FROM PUBLISHED JOURNAL.Generally, hip angle would not present hip extension during walking for the whole gait cycle as shown in figure 6. Hip will flexes as heel strike and reduces in flexion as the foot is loading and flexed minimally during terminal stance (as the foot is in toe off position). Then, the hip starts to flex again as when the ipsilateral foot is starts to enter the swing phase. The ipsilateral hip is continuously increase in flexion as it undergo swing phase and prepare to do a next heel strike for next gait cycle.However, figure 5 shows the hip of the prosthetic leg is flexing approximately 1 during heel strike and reduced flexing as it starts loading. The hip is starting to extend at approximately 10% of gait cycle and increase in extension for the rest of the stance phase. Even during the toe off of the prosthetic leg, the hip is still in the extension which is act as the minimum flexion in the normal person gait in which it is the maximum degree of hip extension. As swing phase of the prosthetic leg stars, the hip extension is reduced and starts to present hip flexion as it swing and starts to form heel strike position of next gait cycle.Besides that we can see that the maximum hip extension (refer point of minimum hip flexion of normal person gait) is late occur if compare to the normal person gait in figure 6. This is shows that the stance phase of the prosthetic leg is longer compare to the stance phase of normal person. Same things happen to the sound legs swing phase. It starts late is due to the longer of stance phase of the prosthetic leg. This is due to the slow progression of loading and terminal stance of prosthetic leg which has been explained in figure 1 (GRF graph).For the sound limb, the hip is flexion as the heel strike happen and reduced in flexion as the ipsilateral is loading but there is slightly increase in flexion (circle A in figure 5). The sudden increase in the circle A is coinciding happen in circle B. This is due to the synchronizing of stance phase of sound leg and swing phase of prosthetic leg. At this time, the sound leg is undergoes a progressing of loading and the prosthetic leg is undergoes auto lock of the knee joint which produce extra force (inertia) due to the sudden pulling of spring lock to extend the knee joint. When the knee joint is pulled to extend with the extra force producing by the spring the hip will automatically pulled to flex due to the extra force. While the hip of the sound limb which in loading response also flexed in order to counter the sudden pulling force for the stability and prevention from falling. The flexed of the knee at that moment results the flexing of the hip. This can be seeing in figure 7.

Slow progressing of force during loading and terminal stance of prosthetic leg.DELAYED SWING PHASE OF SOUND LIMB AND HAPPEN IN SHORT..NOTE: The 100% of GRF graph = stance phase of gait cycle.FIGURE 7By comparing the graphs, we can identify where the swing phase occurs. Swing phase occurs when hip and knee flexed. For the prosthetic leg, it enters swing phase approximately at 63% of gait cycle, which is later if compared to normal people where swing phase is at 60% of gait cycle. It also shows that the swing phase of prosthetic leg is longer if compared to normal people. This is because the subject takes time to land her prosthetic leg on the ground. As for sound leg, the swing phase occurred 75% of gait cycle which later than prosthetic leg and normal person. The long stance phase is to provide stability for the patient when she is swinging her prosthetic leg. The GRF graph proves that the stance phase of prosthetic leg is longer than normal persons gait stance phase which effects the shorter swing phase of the sound limb and happens late than in normal persons gait.Other than that the GRFR also shows that the midstance of prosthetic limb is happening in short time than the sound limb. This is proves by the flexion of hip and knee flexion is increased and reduced in short of time.

CONCLUSIONWe can conclude that, the prosthesis does affect the ground reaction force (GRF) of walking gait in an amputee. This have been proves by the stance phase of prosthetic leg is more longer compare to the normal persons GRF graph. Also, the swing phase of the sound leg is shorter in time happen than the normal persons GRF graph. Other than that, the prosthesis affected the knee and hip of the sound limb in term of flexion and extension. We can see from the graph, the knee flexion of sound limb during stance phase is more than normal person and the hip extension during push off and preswing of sound limb is happen. This effect is to gain the stability during walking and prevent from falling.

REFERENCES1. Pitkin, R Mark. (2006). Biomechanics of Lower Limb Prosthetics. USA: Springer.2. Jenkins, J. & Ellis, C. (nd) Using ground reaction forces from gait analysis: Body mass as a weak biometric, 5-7. Retrieved 19 December 2011 from http://www.jamjenkins.org/ 3. Bogey, R. (2009). Gait Analysis. Retrieved 19 December 2011from http://emedicine.medscape.com/article/320160-overview

APPENDIX ASkeletal view of markers placement for Vicon Nexus.

RESEARCH PROTOCOL AND AMENDMENT

PATIENT GAIT CHARACTERIZATION AND OVERALL WORKINGS OF THE PROSTHETIC/ORTHOTIC LEGOBJECTIVES To study the variation of parameters involved in gait analysis for different lower limb prosthetics and orthotics users. PERSONNEL Certified Prosthetist and Orthotist (CPO) or Medical Officer (MO) to ensure the patient safety and give advice on the proper way to handle the patient. Maximum of 3 investigators to give instruction to the patient, to handle the system while executing the experiment and to conduct the subject calibration.EQUIPMENTS Vicon Nexus Motion Analysis System Force plate Reflective markers T-frameSTUDY DESIGN & PROCEDUREa) System Preparation and calibration1. First, empty the space within the camera view range and remove any reflective items.2. Go to System Preparation tools pane and make sure the 5 Marker Wand and T-Frame is selected from the Wand and T-frame drop-down menu.3. Place the static calibration object flat on the floor in the center of the capture volume at the desired origin position.4. In the Aim MX Cameras Calibration section, click Start to begin the MX camera aiming process. (Note: Nexus starts attempting to identify the calibration object in each camera view, and the Start button switch to its Stop setting.)5. Under Resource Pane, select the System tab and expand the MX camera node. Select all MX cameras.6. Change the view pane mode from 3D perspective to Camera.7. Remove any unwanted reflection registered in any of the camera view or mask them by clicking Start the Stop under the Create MX camera Masks.8. Then, get someone to wave the 5 Marker Dynamic Calibration frame (T-frame) throughout the capture volume as soon as you hit start under Calibrate MX Cameras. (Note: swing the T-frame from head-to-toe and right-to-left alternately, and walk around the space within the camera view range)9. Wait until the automatic stop feature enabled and the image error value displayed. (Note: ensure that the error value for all the cameras is at most 0.2%. If exceed, the please repeat step 8)10. After that, place the calibration wand at the capture volume origin. (Note: place the wand on the force plate)11. Ensure that no one is standing in the capture volume, and then click on Start under Set Volume Origin.12. Reverting back to the 3D Perspective View and zooming out, so that the cameras are in view. Ensure that Nexus has registered the correct position of all the cameras in the capture volume.

b) Subject Preparation

Measure the patients body mass, height, leg length, knee width, and ankle width. (Note: Jot down the value and do the measurement for both sides) Place the markers (16 markers) according to the recommended marker placement template for Vicon Nexus (refer to Appendix 1 and Appendix 2 focus on the lower extremity)

c) Subject Calibration and Trial Reconstruction

1. In the Subjects resources pane toolbar, click the Create a new Subject from a Template button.2. Choose PlugInGait.vst from the dropdown menu.3. Enter the name of your new subject and click OK.4. In the Resources pane, ensure Nexus is in Live mode.5. In the capture volume, have the subject stand in a stationary neutral pose (T-pose).6. Select static plug-in gait from the dropdown menu.7. In the Subject Capture section, click Start to begin capturing subject data and then stop after 1-2 seconds of data capture.8. Reconstruct the trial. 9. From data Management window, open the desired trial file containing reconstructed markers.10. On the Time Bar ruler, place the Current Time Cursor on the first frame of the trial in which the subject is standing in a stationary neutral pose to enable the Vicon system to determine the location of key markers.11. Ensure that the subject node you created from the template is the only entry enabled for capture in the Subject resources tree.12. In the Label/Edit tools pane, from the Subject list select the subject to be manually labeled.13. From the Manual Labeling section, select Auto advance selection.14. From the list in the Manual Labeling section, click on the label you wish to use.15. In the 3D Perspective view pane click on the marker you want to assign the label to.16. Repeat step 14-15 until you have assigned all of the labels to markers. (Note: The stick figure in the 3D Perspective view pane should resemble a skeleton of the subject type defined in the .vst file.17. Verify that the manual labeling was successful by checking that all markers are connected by sticks and that the sticks on the left side of the subject are red and those on the right side are green.18. Click Save button.d) Gait Assessment and Process Trial1. Before proceed with the trial, estimate a distance for the patient to stand from the force plate by projecting the way the patient walk a complete gait cycle on the force plate.2. In the Resources pane, ensure Nexus is in Live mode.3. Display a 3D Perspective view pane.4. In the Capture tools pane, under the Capture Configuration Management section select an existing capture configuration for the trial from the Trial Type list or create a new one.5. In the Next Trial Setup section, fill in the details for storing your trial data in the active session.6. In the System resources tree, select Local Vicon System and then in its Properties section under Core Processor, set Processing Level to Kinematic Fit.7. In the capture volume, have the subject with the Vicon markers attached perform the gait.8. In the Capture tools pane, under the Capture section click Start. 9. After you have acquired the data you need, click Stop.10. Repeat step 7-9 until you have obtained 5 trials to ensure a complete gait cycle is obtained on the force plate. (Note: ensure the patient get enough rest before proceed to another trial)