This study reviewing the biomechanical effects of the orthosis on human gait pattern and a specific type of ankle foot orthosis (AFO) with rocker bottom was used for the pilot study. Walking gait cycle background theory and related terms definition is explained as the introduction. A complete review on AFO functionality and efficacy on gait correction via laboratory testing is done. The review is mainly expressed from biomechanics approach with the use of kinematics and kinetic knowledge. From the reviewed process, it is no doubt to clarify that AFO enable to prevent and correct pathological gait for better improvement. Motion analysis technique using camera based system to conduct laboratory experiment on human gait is studied too. A sequence of procedures is design for further study, which consist of subject acquirement, rocker AFO fabrication, customization, laboratory experiment testing using Vicon motion analysis system, data collection and analyse. Besides, pilot study’s results are included in result and discussion. A healthy woman was used as the subject in the pilot study who undergo 2 types of walking, which are walked barefoot and with AFO condition. As conclusion, the review provides evidence that the influence of AFO in altering human walking gait is significant and further study is necessary to be proceeded for better describe AFO functionality.
The first thank goes to Prof. Dr. Ir. Wan Abu Bakar Wan Abas, my supervisor for this graduation project. His willingness and patient in teaching and guide me either to accomplish the tasks or when I facing problems during the time, were indeed appreciated. My grateful thank goes to Dr Noor Azuan Abu Osman with his enthusiasm of sharing valuable knowledge and all kind of challenges gave by him, were definitely brought me chances to work as an professional biomedical engineer. I express much gratitude to Miss Arezoo Eshraghi too, for her guidance and assistance brought to the smoothness of my thesis study.
Nevertheless, I would like to thank for all the hard work done by my faculty, especially to the Coordinator for the Graduation Project, Dr.Belinda Murphy, assistant for the project Miss Khairunnisa Hasikin and all the stuff of Biomedical Engineering Department.
Table of Contents
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List of Tables
List of Symbols and Abbreviations
AFO Ankle Foot Orthosis
IC Initial contact
LR Loading Response
MST Mid Stance
TST Terminal Stance
TO Toe Off
ISW Initial Swing
MSW Mid Swing
TSW Terminal Swing
KF Knee Flexion
KE Knee Extension
HF Hip Flexion
HE Hip Extension
PTB Patellar Tendon Bearing
ToA Types of AFO
CGC Control Group Condition
Human locomotion defined as movement from one place to another and a numbers of ways could be done to achieve it, walking, use of a bicycle, wheelchair are examples of locomotion (Smidt, 1990). In this study, walking gait is the targeted locomotion. Walking is a cyclic movement interlaced between left and right foot with at least one foot being contact with the ground at all times in a certain periodic pattern (Ounpuu, 1995). A systemic analysis and parameter is required to evaluate walking gait effectively and biomechanics knowledge has been introduced to solve for this. It is a brand new term developed around the year of 1970s which integrating engineering mechanics knowledge into biological system.
Biomechanics is actually applied in gait analysis by the ancient scientists few centuries ago (Martin, 1999). Biomechanics study on the gait analysis has been started since the year of 1680 by Aristotle on the gait of animals and in the year of 1890, Christian Wilhelm Braune an anatomist and Otto Fischer were started investigating human gait from biomechanics aspects (Martin, 1999). Scientists’ enthusiasm toward human gait analysis never shelved, it continue evolutes until today. At present, biomechanics investigation in gait analysis is able to provide profusion information for clinical practitioner to assess patient locomotion effectively. For instances, a pathology gait pattern by patient can be visualized by measuring biomechanical parameters, step length, length, joint angles, forces and etcetera. To evaluate how well the treatment improves patient ambulatory level, biomechanics knowledge applied too.
Main interest of this study is not only focus on human walking gait, but also to investigate the manner orthotics alters its users gait pattern from biomechanics aspect. Orthosis is a medical appliance major used in orthopedics field for the purpose to support, alter, and align injured body segments involve in body movement (Edelstein & Bruckner, 2001). In this study, the ankle foot orthosis (AFO) with additional rocker sole is chose as the orthosis in this study. Figure 1.1(a) shown a solid AFO and (b) rocker bottom.
Figure 1. Solid AFO
Rocker AFO is a kind of treatment apply to diabetic patient who has plantar foot ulceration risk and with ankle joint mobility difficulty. From statistical analysis from University Malaya Medical Centre Diabetic Foot Clinics, plantar foot wound treatments on diabetic patient possess the highest number of among other kind of treatment and also footwear is the highest treatment modality among others in 2008 and 2009. This statement has support and encourages the necessity to carry out this study as number of diabetic patient is increase gradually every year.
AFO is worn on lower extremity and around foot to support and correct ankle position. Patient having diabetes, experienced bones segment fracture, cerebral palsy, spinal cord injury, tendon dysfunction and limb disorder patient who ankle failed to support their body weight while walking are commonly suggested by orthotist to use an AFO to improve gait routine and to minimise further injury risk (Edelstein & Bruckner, 2001). Besides that, rocker sole is a creature use to reduce pressure on the forefoot and use to transmit pressure from high pressure to low pressure area meanwhile off loading the pressure exerted to risky area (Albright & Woodhull-Smith, 2009). To be relative to orthosis definition, an AFO with rocker sole should not bring more burdens to patient in increase energy demand or cause any long term side effects. Consequently, investigating AFO biomechanical performance in aiding and influencing wearer locomotion therefore becomes an important study.
Three dimensional (3D) gait analysis systems are laboratory equipment involve the use of reflective markers that placed on subject’s interest body segments as the landmarks (Davis, Deluca, & Ounpuu, 2000). It has been use widely in clinical gait analysis services and research. The video camera based system employ 2 to 7 infrared cameras allocated on the measurement volume to record subject motion or markers trajectories in precise as shown in Figure 1.2 (a) & (b). The entire system applies stereophotogrammetric techniques to produce each marker’s 3D coordinates from the two dimensional (2D) images capture by each of the camera (Davis, et al., 2000). This 3D system digitized subject movement in real time into frames depending on sampling rate set. The frame to frame analysis provides better motion visualization and subsequently from the 3D images generated it makes the possibility to compute a more complete description towards the dynamic gait in terms of biomechanical parameters. Kinematic, kinetic, and temporal parameters or some other dynamic gait variables are able to be obtained from this system. During the entire study, Vicon Nexus 1.4 motion analysis system is employ to record and examine subjects walking gait pattern. Kinematic and kinetic parameters are extracting to further illustrate rocker AFO effects on its user gait pattern. Figure 1.2(c) presented a monkey hooping frame image capture using 3D motion analysis systems.
Figure 1. (a) Infrared Camera (b) Overview of Motion Analysis Laboratory (c) Frame Images Capture from Infrared Camera
Normal one complete gait cycle consists of stance phase and swing phase in a proportion of 60% and 40%, respectively. A normal adult will spent approximately 60% of total gait duration for heel strike to toe off (stance phase) and 40% for initial swing to terminal swing (swing phase). Stance phase is the event when foot touch on ground and body passes over the top of it whereas swing phase is when the same foot moves forwards in the air.
Figure 1. Stance and Swing Phase Propotion.
Stance phase is defined from initial contact, loading response, mid stance and terminal stance (toe off). Swing phase is defined from the instance toe off, initial swing, mid swing and terminal swing (Ounpuu, 1995). Figure 1.4 illustrates the phases of the gait cycle shown with the corresponding position for sagittal plane motion.
Figure 1. Gait cycle phases (Carson, M.D. 1995)
Initial contact(IC) (0% of the gait cycle), it occur when foot contact to ground.
Loading response (LR) (0-10% of the gait cycle), during this stage, shock absorption occurred with stability remain and body more forwarded. This is the first double support happened.
Mid stance (MST) (10%-30% of the gait cycle), the first single leg support instance, purpose of this phase is to advance body over the stance phase limb while stability is maintained.
Terminal stance (TST) (30%-50% of gait cycle), or sometimes called toe off(TF) single support ended when the sound limb contact with floor and in this phase, body still being advanced through the stance foot through the forward fall of the trunk.
Toe off (TO) (60% of the gait cycle), when foot’s toes are about to leave floor.
Initial Swing (ISW) (60%-73% of the gait cycle), second single support phase and begins when the foot leaves the ground until it passes opposite the stance limb.
Mid swing (MSW) (73%-87%), continue advance the swing limb while providing clearance of stance foot.
Terminal swing (TSW) (87%-100%), swing leg already in preparation for the next stance phase.
In order for a person to walk normally, the locomotor system must fulfill four requirements. Firstly, stability of foot is essential to ensure each foot capable to withstand body weight with no collapsing. Secondly, during single leg support in stance phase, balance shall sustain for that particular period. Thirdly, swinging leg must be able to move in a sequence reaching the position where it can take over the supporting leg. Lastly, locomotor system must provided substantial power to induce limb movements and to advance the body (Whittle, 1993).
Pathological gait produce abnormal walking patterns when it fails to obey any of the four requirements stated above. It can be indentified obviously by visual or using appropriate clinical gait analysis method. This abnormal gait maybe performed unintended by the subject due to the weakness, spasticity or deformity occurred onto them. Besides, sometimes the abnormal gait is also consequences of the compensatory motion by some other problem. Any abnormal gait should be corrected using an orthotics or braces in order to minimize overload harms on muscles, joints and bones.
Kinematic and kinetics of human gait
The terms kinematic and kinetics are branches of biomechanics, which are commonly employed in gait assessment. Kinematic describing a body movement without considering its causes for example forces and torque. Camera is a example of kinematic equipment which only used to observe limbs movement without but without providing information of force involved (Whittle, 1993). Meanwhile, kinetic is more in explaining the body motion with it causes like mass and forces exert onto the system. Moment, force, mass, and acceleration are the examples which usually utilize the kinetic of the systems. Example of kinematic equipment in gait analysis is force plate, which measure force exerted by foot but without the position and angle of the leg segment (Whittle, 1993).
Kinematic of human gait: Angle
Pelvis, hip, knee and ankle angle are the common kinematic parameters used in gait analysis. Each anatomical angle can be observed from sagittal, coronal and transverse plane. During normal gait, most of the motion occurred in sagittal plane meanwhile coronal and transverse plane have greater motion in pathological gait(Ounpuu, 1995). Table 1.1 is a summary on the each segment movement with respect to gait cycle’s phases.
Table 1. Summary of the Major components of gait with respect to the phase of the gait cycle.
Peak PF then DF rapidly
KF rapidly to peak
Start with peak KF and KE rapidly
PlantarFlexion(PF), DorsiFlexion(DF), Knee Flexion(KF), Knee Extension(KE), Hip Flexion(HF) and Hip Extension (HE)
Kinetics of human gait: Ground reaction forces
When a person is walking, forces will apply toward ground on each step taken. According to Newton’s Third Law, a force will generate that is equal magnitude but in the opposite direction to the force applied by the foot, and it is called ground reaction forces.
The vertical component of ground reaction forces is raise from heel strike and shot 112% of body weight during 25% of gait. At the mean time, the opposite leg propels the centre of gravity upward and thus vertical force descends to around 80% of body weight. At the instance of heel off, centre of gravity start to move downward therefore vertical forces raise again to around 115% of body weight at almost 80% of stance phase. Vertical forces descend greatly right after the peak vertical forces as the foot is propel to swing phase. Figure 1.5 shown the overview of vertical forces exert on the stance leg.
Figure 1. Ground reaction forces
Types of AFO
AFO is categorized into many types depending on its functionality, design approach and usages. AFOs are generally classified into five main branches: rigid AFOs, hinged AFOs, Patellar Tendon Bearing (PTB) AFOs, posterior leaf spring AFOs and ground reaction AFOs. Each AFO’s functionality will be discussed in detail later.
Table 2. Summary on Types of AFO and description (Edelstein & Bruckner, 2001)
Types of AFO
Solid AFOSolid ankle-foot orthosis (AFO), Plastazote-lined (Photo courtesy of Hersco Orthotic Labs.)
Trimmed anterior to malleoli surrounds ankle.
Restrict ankle motion without allows any plantarflexion.
During loading response, maintain a rigid foot and ankle alignment
Add mechanical joint around ankle to permit motion.
Degrees of motion are determined by the joint design.
Allow dorsiflexion and plantar flexion without restriction.
Cast until patella area as to transfer weight from plantar foot to patella tendon
Responsible for off loading effect.
Posterior Leaf Spring AFOhttp://www.neuromuscular-orthotics.com.au/images/PLS%20AFO.jpg
Trimmed posterior to malleoli, allow plastic to recoil
Function as a spring during swing phase off loaded, allow plantar flexion.
Ankle motion is permitted by deformation and recoil of the plastic strip.
Gait analysis method
Reliability of the result obtained from motion analysis is mainly relay on the markers placement (Ferrari, et al., 2008; A. Leardini & Benedetti, 1999). Therefore, marker positioning is depending strongly to the objective of the research or study. The inconsistency of marker placement is generally a crucial factor contribute to the data variation because each marker represent different body landmark respectively too. A full body marker set is often applying to investigate whole body posture and gait. A total of 60 markers with 22 on each leg, 5 on pelvis and 11 on trunk are consider as a complete marker set. It has been applied to evaluate treatment gait pattern correction or diseases caused pathological gait for example cerebral palsy and diabetic patient (Radtka, Skinner, & Elise Johanson, 2005; Sawacha, et al., 2009). Only lower limb markers set were use more often in gait motion analysis (Abel & Juhl, 1998; Fatone, Gard, & Malas, 2009; Alberto Leardini, et al., 2007; Yokoyama & Sashika, 2005). There also few study make their focus on gait assessment on AFO user which only applied reflective marker on lower limb as anatomic landmarks for the whole experiment (Abel & Juhl, 1998; Fatone, et al., 2009). When come across with gait analysis, researchers putting more interest on the lower limb’s kinetic and kinematic parameters rather than upper limb because the locomotion trajectories occurred mainly in leg segments.
In analyzing treatment effect for a particular illness or disease, control group or control variable present to serve a better comparison to the tested result. While evaluating the relation of orthosis treatment and gait assessment caused by it, subject under barefoot condition sometimes appeared as the control variable (Abel & Juhl, 1998; Lam, Leong, Li, Hu, & Lu, 2005; Romkes & Brunner, 2002). However, in some cases, barefoot control does not provide a comparable opportunity and it is not practical as in real life subjects usually walk with foot wear. Besides, as of experimental approach, it has shown that subjects walking with footwear is more relative to evaluate AFO efficacy with contrast to barefoot ((Radtka, et al., 2005)Churchill et al., 2003; Radtka et al., 2005). Two reviewed articles obtained result with subject walking while wore footwear alone (Bleyenheuft & Hanson, 2010; Fatone, et al., 2009). There is one of the article used able bodied subject with footwear alone to acquire control variables (Fatone et al., 2009). Either way of choosing control group is proportion to the research behavior and objectives. Therefore, appropriate consideration should be taken while designing a research methodology.
Gait analysis parameters
In general, AFO is use as prevention of foot deformity, limit joint movement, position and provide stability. The effect of AFO in serving all these functionality is been studied via various method from simple to more sophisticated gait analysis technique. Majority of the reviewed papers adopted video-camera based system to collect and record data. (Abel & Juhl, 1998; Fatone, et al., 2009; Lam, et al., 2005; Radtka, et al., 2005; Romkes & Brunner, 2002; Yokoyama & Sashika, 2005). Kinematic and temperal parameters are the two common results obtained from ambulation analysis.
Cadence, defined as number of steps taken in a given period and its unit is steps over minute. In gait analysis, cadence becomes a popular parameter to evaluate AFO efficacy. Researches which have examined subject’s gait with dynamic AFO and without dynamic AFO proved that cadence is one variable altered by the manipulation on AFO (Lam, et al., 2004; Romkes et al., 2001; Bleyenheuft et al., 2007). Lam and Romkes studies have shown a decrease of cadence while subject walked with dynamic AFO compare to walk with barefoot. However, in Bleyenheuft study, changes of cadence value are less significant compare to others. In hinged AFO, two papers reported a increase on cadence compare to barefoot ( Romkes et al., 2001; Tyson et al., 1998) and one shown decrease effect (Radtka et al., 2004). Four reviewed papers tested subjects walked with solid AFO reported decrease of cadence compare to without solid AFO (Abel et al., 1998; Radtka et al., 2004; Lam et al., 2004; Bleyenheuft et al., 2007). Cadence in a new design AFO which use oil damper resistance to restrict ankle movement also reported a decrease phenomenon on subject’s walking gait with against barefoot trials.
Dynamic AFO reported to have higher cadence compare to solid AFO in Lam, 2004 and Bleyenheuft, 2007 studies. Meanwhile, between hinged AFO and dynamic AFO, hinged type’s AFO having higher cadence value ( Romkes et al., 2001). By reviewing this, an instance conclusion can be making that hinged AFO provide a high cadence. Resultant cadence variation is likely due to the design of types of the AFO. Manipulate ankle movement degree certainly influence entire locomotion trajectories, consequently cadence are involved.
Velocity is a resultant product of stride length time cadence. Any changes of these two variables may vary walking velocity. Solid AFO, dynamic AFO, and hinged AFO were all result higher velocities and stride length compare to the condition without AFO on tested walking trials (Abel et al., 1998; Lam et al., 2004; Radtka et al., 2004; Bleyenheuft et al., 2007; Romkes et al., 2001; Fatone et al., 2009). However, a less significant increase observed while analyzes hinged AFO and solid AFO toward barefoot condition in Fatone, 2009 and Lam, 2004 researches, respectively. From these two cases, a common observation found between them is the insignificant of stride length’s alterations.
Kinematic of Gait Analysis
DF at IC (Stance Phase)
Currently, AFO are design to restrict exceed ankle PF, simultaneously improve pre-positioning of the foot during IC f gait cycle. However, DF ability of AFO is strictly relying on the design and trimming pattern of particular AFO (Yokoyama et al., 2005). All types of AFO being study in this section have shown reasonable increase of DF angle compare to barefoot or without AFO condition (Abel et al., 1998; Lam et al., 2004; Radtka et al., 2004; Bleyenheuft et al., 2007; Romkes et al., 2001; Fatone et al., 2009; Yokoyama et al., 2005). This outcome is consistent with the basic functionality and characteristic of AFOs. For hinged and dynamic types, both allows free ankle DF during stance and meanwhile limit PF (Romkes et al., 2001). From review, subjects wore dynamic AFO have noticeable better DF than solid AFO and barefoot (Lam et al., 2004; Bleyenheuft et al, 2007).
KF during IC (Stance phase)
Knee fully extends just before heel contact and this is named as stance phase flexion. Patient walked with dynamic AFO showed significant increased in KF during initial stance compare to barefoot and there was less significant compared to solid type AFO (Lam et al., 2004; Bleyenheuft et al., 2007). Nevertheless, a slightly decreased on KF during initial contact is observed too. Both dynamic and hinged AFO shown little attenuate of KF angle compare to barefoot in Romkes, 2001 studies. In Radtka, 2005 research, the abnormal KF during barefoot walking remained although subject walk with hinged and solid AFO and this is consistent with Rethlefsen, 1999 findings.
PF during TST (stance Phase)
At the instance stance foot leave ground and preparing for swinging, plantar foot is flex as to push off body forwarded. Hinged AFO have impressed decreasing of PF during terminal stance if compare to walked with barefoot ( Radtka et al., 2005; Romkes et al., 2001). In Romkes, 2001 study, it revealed that hinged AFO has better push off effect compare to dynamic AFO according to their flexing ability. Besides that, in Radtka 2005’s study, researchers concluded hinged AFO has better rocker effect as to proceed swing phase compared to solid AFO.
DF during MSW (Swing Phase)
DF is necessary to prevent foot drop as to provide toe clearance for patient to have better gait performance. In all the reviewed papers, DF were all increased during MSW (Abel et al., 1998; Lam et al., 2004; Radtka et al., 2004; Bleyenheuft et al., 2007; Romkes et al., 2001; Fatone et al., 2009; Yokoyama et al., 2005).
Table 2. Summary on Variables Comparison of Types of AFO (ToA) with respect to Control Group Condition (CGC)
Variables comparison on ToA with respect to CGC
DF at IC
KF at IC
PF at TST
Abel et al., 1998
Blenyenheuft et al., 2007
Fatone et al., 2009
Lam et al., 2004
Radtka et al., 2004
Romkes et al., 2001
Yokoyama et al., 2005
Oil damper resistance AFO
Kinetic of human gait: Ground reaction forces and Peak pressure
High peak plantar pressure (PPP) on foot is significant in contributing ulceration and callus formation on diabetic patient (Caselli, 2002; Veyes, Murray, & Buoulton, 1992). If PPP occurred on the same area for a repeated period it might associated with callus or skin break down on that particular area (Boulton AJ, 1993). Incidence of skin breakdown in the forefoot chance is higher compare to in rear foot (Mueller, Zou, & Lott, 2005). It has been prove in few studies that metatarsal head is the most frequent areas having skin injury problem rather than at heel in diabetic patient (Caselli, 2002; Sinacore, 1996).
By using rocker sole in diabetic subjects, reviewed papers shown a significant PPP reduction over the high pressure area especially over forefoot and rear foot area (Albright & Woodhull-Smith, 2009; Brown & Wertsch, 2004; Schaff & Cavanagh, 1990). Rocker sole is designed in a way that to redistribute plantar pressure from a conventional pressure distribution to a newly designed pressure map(Brown & Wertsch, 2004).
Aims and Objectives
Examine orthosis efficacy in walking gait is the foremost objective in this study. AFO is prescribing enable to make better alignment of foot on patient with pathological gait. A rocker bottom is claimed to serve better plantar pressure distribution and as treatment to avoid further foot deformity. Basic approach in this study is to investigate the effectiveness of rocker AFO in prevent and utilize better ambulation pattern on diabetic patient from abnormal walking mechanism. Joint mobility caused by rocker AFO believed serve a better gait pattern and harmless to the connected leg segment. Rocker effect on the AFO is tending to reduce ground reaction forces to AFO user foot. Biomechanics and engineering knowledge is applied for better description.
To test this hypothesis the following key objectives were undertaken:
To study and enhance better gait mechanism knowledge from engineering and medical approach.
To quantify and compare joint mobility with and without rocker AFO using lower limb component motion range analysis.
To observe the relationship between the rocker bottom to kinetic changing on patient gait.
Method to conduct this study is structured into few stages from recruiting subjects to conclude the study objectives. In order to keep align with this study objectives, each procedure taken has to be design carefully to reduce the possibility of data confusion and the occurrence of technical errors. Mostly, methodology to investigate orthosis efficacy usually being categorized into subject acquirement, subject assessment, AFO fabrication, AFO customize process, gait analysis laboratory testing, data acquisition and data analyzing ( Fatone et al., 2009).
In this study, AFO with rocker bottom is fixed to be the interest orthosis to investigate for the entire process. From literature, an AFO rocker sole mostly applied for the purpose of offloading on diabetic patient, thus the targeted subject is diabetic patient who possess potential to occur ulceration at plantar foot (Zimmy et al., 2004; Albright et al., 2009). 5 patients with diabetic peripheral neuropathy are recruiting as the subjects. Subject should be free from any other physical abnormality, surgery or injury on the lower limb extremities. To be prior to their participation, informed concern was acquired from all the subjects.
Equipment: AFO Fabrication
Only unilateral study will be carry out which means rocker AFO will be only fabricate for either leg depends on the foot condition. Each participant will be customizing a rocker AFO which is unique with their ulceration area and foot sizes. Participants are evaluated barefoot and going through anthropometrical measurement on the affected leg by the orthotists. The AFO are custom molded by polypropylene and with a suggested 4.8 mm thick (Lam eta al., 2005). Neutral position of the AFO will be 90° at foot shank ankle. Foot length of the AFO will extended distally under the toes end and trimmed along the mediolateral border of the foot. Upper part of the AFO will trimmed on posterior until about 2.5cm below fibula. Rocker sole apex has to be position according to subject pressure distribution. Usually subject affected areas are location with metatarsal and forefoot area. A consistent rocker sole design is purposed with the apex fall behind of the fifth metatarsal with an angle of 15°. Figure 3.1 shown the rocker AFO suggested:
Figure 3. Rocker AFO
After rocker AFO finishing, subject request to test the fitness of the AFO. If the custom made rocker AFO raises any comfort ability issue, adjustment being done to fix it.
Gait analysis laboratory testi