Michael Dillon
Supervisor: Dr. T. M. Bach
La Trobe University, Melbourne, Australia
A biomechanical analysis of the gait patterns of four normal and ten partial foot amputees including one Chopart, five transmetatarsal (TMA), and four metatarsophalangeal (MTP) amputees was undertaken in order to obtain basic kinetic and kinematic data. The Chopart amputee was fitted with a PTB clamshell prosthesis while the others were fitted with AFOs or EVA insoles.
Testing involved documentation of a medical history, physical examination and gait analysis using a VICON 3D motion analysis system and Kistler force platform. Affected limb kinetic and kinematic data were collected and analysed for the sagittal plane only. Kinematic and kinetic patterns were averaged within each group.
The results showed a significant positive correlation between residual foot length and centre of pressure excursion (r=.898) across the MTP and TMA amputees indicating that the EVA insoles and AFOs did not substantially restore function. A significant relationship was found between residual foot length and peak plantarflexor power generation (r=.814). It appeared that once the metatarsal heads had been compromised, further decreases in power generation were negligible. The Chopart and TMA amputees showed substantial alterations in the normal kinetic patterns seen at the hip and the knee. The patterns observed were consistent with an attempt to compensate for a lack of power generation at the ankle. No significant alterations were observed in passive ROM between groups (F=1.56, df=12;p=.2572). The variability observed within groups would make socket prescription based on ankle ROM inappropriate. The successful utilization of the available ankle motion, measured by power generation at the ankle, would appear to be a better prescription principle.
The gait patterns observed may have been confounded by the type of prosthetic fitting. Further research should assess the biomechanical effects of prosthetic fitting.
Stefania Fatone
Supervisors: Dr. T. M Bach1, Prof. H. K. Graham2 and Mr. I. Torode2
1La Trobe University, Melbourne, Australia
2Royal Children's Hospital, Melbourne, Australia
The gait of six limb deficient children was analysed in the Hugh Williamson Gait Laboratory at the Royal Children's Hospital, Melbourne. The procedure for testing included a physical examination, gait analysis and energy expenditure test. During the physical examination static range of motion and muscle strength were evaluated and relevant anthropometric measurements taken. A VICON 3D motion analysis system was used to track retro-reflective markers placed on the pelvis and lower limbs of the subjects as they walked along a 10 m walkway in which two AMTI force plates were concealed. Bilateral kinematic and kinetic data were generated for the pelvis, hip, knee and ankle across three planes (sagittal, coronal and transverse). An OXYLOG portable oxygen consumption metre was used to measure oxygen consumption of the subjects as they walked around a 23.5 m course. Descriptive analysis of the results was undertaken and compared to normal child data.
Results showed that for the PFFD subjects pelvic motion was excessive and abnormal in all three planes, sound limb hip flexion was greater than normal, hip rotation on the affected side was abnormal, and sound ankle plantarflexion less than normal. The Tibial Rotationplasty subjects exhibited knee flexion during stance that was consistent with that described by other authors. Pattern and magnitudes of external rotation of the sound hip was unique to these subjects. Sound side knee extensor moments during stance similar to trans-tibial amputees were found. Oxygen cost was normal or less than normal for the four subjects measured. Walking velocities during the OXYLOG test were lower than those during the VICON test, indicating the effects of encumbrance of the OXYLOG apparatus. A paired t-test showed that these differences were significant (p<0.04). Further research is needed to explore the implications of excess pelvic motion on long term back problems and the relationship between hip instability and pseud oarthrosis and the pelvis. Because of the rarity of this condition, national and international databases should be established in order that a substantial data pool can be accessed by investigators.
Kaisha Danielle Smith
Supervisors: Dr. T. M. Bach and Dr. D. K. Rogers
La Trobe University, Melbourne, Australia
The purpose of this study was to examine the effects of Tone-reducing Ankle Foot Orthoses (TRAFOs). The neurophysiological rationale of pressure over muscle insertions was evaluated utilising quantitative electrophysiological and biomechanical means.
Four subjects with clinically defined mild or moderate spasticity completed three sessions: (1) assessment and casting, (2) fitting of the tone-reducing modification and (3) experimental. The pressure was applied medially and laterally to the Achilles tendon using bivalved tubing positioned in an articulated Ankle Foot Orthosis (AFO). Data were collected with the subject wearing the AFO and the TRAFO (AFO with tubing added). Each subject completed three phases with each of the orthosis conditions. The phases varied by differences in the exercise period preceding the testing period or the type of exercise during the testing period. The exercise period was completed passively or actively and the testing period with passive dorsi- and plantarflexion or passive dorsiflexion and active plantarflexion. Force and EMG values at the end of a passive ramp stretch of the plantarflexor musculature were recorded for each of the six conditions.
Two and one-way repeated measures ANOVAs showed no significant differences between the orthosis conditions and/or the exercise/test conditions. Several factors could have influenced the results and a major limitation was the small number of subjects. Previously published studies have suggested that the application of pressure either side of the Achilles tendon does not result in decreased spasticity and the results of this study tend to confirm this. There are however, several other rationales behind TRAFOs and the results of this study should not be used to dismiss these devices as a modality of spasticity reduction. Further research evaluating the other principles is indicated. The experimental approach utilised in this study could be a model for further empirical research in this area.
Cecilia Su Tan,
Supervisors: Dr. T. M. Bach and A. M. Keenan
La Trobe University, Melbourne, Australia
This study compared biomechanical effects of two different approaches to design of foot orthoses. The orthoses investigated were a semi-rigid orthosis commonly manufactured by orthotists and a 25 degree inverted device commonly manufactured by podiatrists. Eleven subjects who exhibited excessive pronation were studied while running on a treadmill. Two dimensional high speed motion picture analysis was used to examine rearfoot mechanics and oxygen consumption was used to examine running economy. The study consisted of two measurement sessions after a three week accommodation period for each pair of orthoses. The rearfoot variables included: maximum calcaneus angle, pronation angle at touchdown, maximum pronation angle, pronation range of motion and maximum pronation velocity.
No difference between conditions was observed in any of the rearfoot variables or in oxygen consumption between the two orthoses. Based on these results, it was concluded that there were no differences in rearfoot mechanics or in running economy between the two types of orthoses. Despite this failure to detect differences, all subjects reported a subjective improvement in running with orthosis use.
The exact mechanisms by which foot orthoses affect the body are unclear. Additional research is necessary to identify the effects responsible for the clinical success of foot orthoses and to evaluate differences in designs.