Title: Comparison of Hinged and Rigid AnkleFootOrthoses on CP Diplegic Ambulation Using Gait Analysis
1Comparison of Hinged and Rigid Ankle-Foot-Orthoses
on CP Diplegic Ambulation Using Gait Analysis
- Sheldon R. Simon, M.D.
- Deborah L. Wilson, M.D.
- Thomas J. Santner, PhD
Chief Division of Pediatric Orthopaedics,
Beth-Israel Hospital Professor Of Clinical
Orthopaedics, Albert Einstein College of Medicine
New York, New York, U.S.A.
2Introduction
For CP patients with dynamic equinous spasticity,
a plastic ankle-foot orthosis (AFO) is commonly
prescribed to control and prevent ankle
plantarflexion
- Ankle Equinous
- Ankle in plantar flexion
- unable to dorsiflex
- alters normal gait pattern
- Walk on their toes
- use only one pivot point
- eliminates double rocker mechanism
- shortens stride length
- needs compensation by hip and knee
- AFO corrects deformity
- prevents ankle plantarflexion
- May act like an arthrodesed ankle
- functionally improves childs gait
- Walks heel toe
- allows for double rocker gait
- increases stride length and velocity
- minimizes abnormal hip and knee motions
- Previous Studies Gait improved more by using a
hinged brace than a rigid brace - increasing step and stride length more
- reducing power absorption more
- improving energy efficiency more
- positively affecting stance phase knee
hyperextension - allowing a more normal muscle recruitment
sequence - Yet both types of braces are still widely
prescribed - Does the wide variations in these childrens
walking abilities affect the degree of gait
improvement with each brace not reflected in mean
values? - do previous studies reflect that a hinged AFO is
best for every child? - are there criteria to suggest which brace could
be best for an individual child? - are the gait improvements with either brace type
reflected in the childs everyday functional
ambulation potential? - Our study addresses these questions
3Methods
- Population
- 43 consecutive CP diplegia spastic equinous
children studied - Tested within 3 months after receiving new AFO
- AFO Rx dtermined clinically by their treating
physician - Made by the childs orthotist.
- Measuring System
- 6 - camera VICON automatic motion analysis system
- 25 reflective markers
- Three-dimensional trajectories calculated using
AMASS-VAX - Cardan joint angles calculated in 3 planes for
the pelvis, hip, knee and ankle - Two AMTI) force plates
- Joint moments and powers calculated from the
force-plate and motion data for the hip, knee and
ankle - Testing procedure
- 6-10 barefoot walking trials
- 6-10 trials shoes /barefoot
- Patient walk at self-selected speed
- trials - normal gait of child
- determined by lab technician / parents
- All trials on same day to minimize variability
4Methods
- Data Analysis
- Time-distance parameters (velocity, stride
length, and cadence) - normalized on the basis of leg length to make
valid comparisons between subjects - The percent of normal value was calculated by
dividing a subjects cadence, stride length, or
speed by the equivalent value found for an
able-bodied child with a similar leg length using
the data of Sutherland - 3-D joint movement parameters for the hip, knee,
and ankle - angular motion, moment, and power data
- total dynamic range, maximum, and minimum values
- of entire gait cycle as well as single limb
stance when these values were reached - only data in the sagittal plane were utilized as
the predominant values related to the brace are
in this plane. - Only data from those subjects who did not use
assistive devices were used for the kinetic
moment and power data calculations. - All data were initially analyzed with histograms
to determine their distribution. - Comparison of the gait data from each side showed
no difference - Therefore, only data from a single side for each
subject were used - In all cases the data for each parameter were
found to be non-Gaussian distributed. - Means, medians, maximum and minimum ranges, and
standard deviations were calculated for all data.
- Two-tailed Wilcoxon Rank Sum (Mann-Whitney) and
Wilcoxon Signed Rank statistical tests were
performed using SAS? (SAS Institute, Cary, NC).
5Methods
- Data Analysis
- Each child was categorized by type of AFO into
one of the two braced groups. - Age, leg length, barefoot time-distance
(velocity, stride length and cadence) parameters,
hip, knee, and ankle sagittal joint angle gait
parameters recorded for each group were compared.
- The two-tailed Wilcoxon Rank-Sum (Mann-Whitney)
test was used to determine if significant
differences were inherently present between the
two groups - Each gait parameter then was examined and
compared within the H-AFO and R-AFO groups. - The difference in magnitude of the measured value
between walking braced and barefoot was compared
to determine if the brace used in that group
caused any statistical change. - A two-tailed Wilcoxon Signed Rank test examined
the significance of these differences. - Regression analysis was then used to build a
model relating each difference to the brace type
and other variables, i.e., age, leg length, and
barefoot gait parameters. - this model was used to determine if changes were
solely due to brace type or depended on other
parameters. - the model allowed the authors to explain the
effect of the change in each parameter
without/with brace on a childs functional
ambulatory status. - Perry et al Walking speed is the only gait
variable predicting functional ambulatory
category. - the effects of changes in cadence and stride
length on velocity differences were examined - brace alterations of peak joint motions in the
stance phase, in their magnitude and timing were
investigated as they related to velocity, stride
length, and cadence. - Ambulatory Status of each child was categorized
as household, limited community, or full - Comparing the subjective caregiver information
with that of the gait study data was by - Hoffer et al. Perry et al. criteria for
subjective data provided by his/her caregiver - Abel and Damiano criteria from the median gait
study normalized velocity
6RESULTS
- Demographics showed no differences between the
two groups - Those that wore a hinged brace had a mean
barefoot speed gt rigid braced group - Barefoot more of the the hinged group had a
higher ambulatory function - Barefoot maximum and minimum sagittal Joint
motions were similar in the two groups
7RESULTS
- Similarly in both groups as age increased
- leg length increased
- barefoot stride-length and velocity increased
- Age-related cadence remained unchanged or
decreased slightly
Scatter plots for children wearing rigid (r) and
hinged (h) braces.
Age Versus Leg Length
Barefoot Stride Length Versus Leg Length
Regression line of age on leg length (p lt
0.00005).
Regression line of barefoot stride length on leg
length (p 0.0006).
8RESULTS
- Barefoot time-distance parameters mean group
differences - Stride Length - no evidence of any differences in
bf Stride Length distribution and age, leg length
or brace type - Cadence - no evidence of any differences in bf
Cadence distribution and age, leg length or brace
type - Speed - no evidence of any differences in bf
Speed distribution and age, leg length or brace
type - Change in per cent of normal stride length- no
evidence of any differences in distribution of
per cent of normal stride length and age, leg
length or brace type - Change in per cent of normal speed- no evidence
of any differences in distribution of per cent of
normal speed and age, leg length or brace type - Change in per cent of normal cadence- no evidence
of any differences in distribution of per cent of
normal cadence and age, leg length, or brace type - The large variation of the gait parameters from
child to child within each group provided little
justification for suggesting that one orthoses
was superior to the other. - We then compared the improvement made in the
time- distance parameters to a single demographic
and barefoot gait parameter for each child - Hinged AFO group - we found strong statistical
evidence that the change in the age-leg length
related percent of normal speed or stride length
varies with the respective age-leg length related
percent of normal barefoot parameter (P lt 0.0004) - Rigid AFO group the change in the age-leg length
related percent of normal speed or stride length
is constant with the respective age-leg length
related percent of normal barefoot parameter
9RESULTS
- For rigid AFO users, the difference in
age-related velocity between barefoot and braced
walks increased about 11.8, independent of
barefoot velocity. - For hinged AFO users, the difference depended on
barefoot velocity and the gait-cycle time when
maximum knee extension and maximum dorsiflexion
occurred. - Change in vel. 9.71 - 0.494 (BF.V 50)
0.584 M.KExt - 0.351 M.DFl - decreases as BF.V increases (P-value 0.000)
- increases as M.KExt increases (P 0.003)
- decreases as M.DFl increases (P 0.014)
- the slope change is about 0.378 / BF.V
decrease - As age-related barefoot velocity increased, the
difference in velocity decreased, exceeding that
found for those with rigid braces only at low
speeds the cross-over barefoot velocity is about
63.
Difference between AFO and barefoot velocity
versus percent of normal barefoot velocity for
Children wearing rigid (r) and hinged (h) braces.
- In only a few children did wearing either brace
alter their functional ambulation status
10CONCLUSIONS
- Barefoot gait velocity, percent of gait cycle of
stance phase max. knee extension and max.
dorsiflexion can predict the improvement in
walking speed when a hinged brace is worn, while
the change made by a rigid brace is constant,
independent of such parameters. - At slower speeds adorning a hinged AFO increases
walking speed more than a rigid AFO at speeds gt
63 of age related walking speed the reverse is
true. - Prescribing brace type based on barefoot walking
function may be important only at transitional
speeds where the childs functional ambulatory
level could change. - At other speeds, the cost of each brace type and
the braces effect on other functions, seem as
important.