Comparison of Hinged and Rigid AnkleFootOrthoses on CP Diplegic Ambulation Using Gait Analysis

1
Comparison 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.
2
Introduction
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

3
Methods

• 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

4
Methods

• 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).

5
Methods

• 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

6
RESULTS

• 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

7
RESULTS

• 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).
8
RESULTS

• 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

9
RESULTS

• 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

10
CONCLUSIONS

• 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.