Help Patients Manage Equinus Deformity
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Help Patients Manage Equinus DeformityUse orthoses to teach children to optimize body weight carriage on the feet.
By Cusick Beverly, PT, MS, COF
A paradigm shift is underway, whereby ankle equinus deformity in children is managed with three important factors in mind: 1)
as a component of a sensory deficit associated with problems of postural control; 2) as a biomechanical element in
single-limb stance whereby the rate of tibial inclination is more significant than the ankle angle; and 3) in acknowledgement of
the necessity to protect foot joint alignment from deforming strains imposed by weight-loaded tension from a calf muscle
contracture.
The components of the new paradigm concept for AFOs includes a foot
orthosis insert to protect alignment.
Images: Beverly Cusick
Within the new paradigm, ankle foot orthoses (AFOs) are made to align the foot joints for optimum weight loading first, and toaccommodate a gastrocnemius muscle contracture while limiting early or excessive ankle dorsiflexion (DF), as is seen in
crouch posture. Premature tibial inclination has gained attention, as opposed to l imiting ankle plantarflexion (PF). The new
paradigm is exemplified in the principles and methods employed in the specialized design of below-knee serial casts used for
postural and gait training and in the tuning of solid AFOs and foot wear combinations.
Maintain verticality
All living beings are driven to achieve and maintain the upright position, beginning in early infancy. The most basic
mechanism for maintaining verticality is a righting reaction which involves the recruitment of the muscles on the side opposite
a body sway. The somatosensory receptors proprioceptors, mechanoreceptors and pressure receptors in muscles,
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connective tissue, joints, and skin have direct links to the muscles along the spine as well as to the cerebellum and the
sensorimotor cortex. Despite having an abundance of ankle DF range of motion (ROM), typically developing infants, while
standing and walking, load the whole foot, but because they have not mastered the use of the antigravity flexors on the front
of the body for balance they tend to carry more body weight on the midfoot and forefoot than the heel. In this way, they can
rely on the more primitive and usually better developed extensor muscles on the dorsal trunk and limbs to remain upright. The
weight-loading pattern matures, moving rapidly toward the heel, within 6 months of walking. By age 4 to 5 years, developing
children with well-aligned feet can be expected to distribute 60% of body onto the heels and 35% onto the metatarsal heads.
This load distribution remains into adulthood.
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Master control
Research on motor learning shows the magnitude of practice involved in the process of learning to manage body weight over
the feet subconsciously while engaged in play. The somatosensory receptors in the feet and ankles deliver vital information to
the cerebellum and sensorimotor cortex that is used in the process.
A typically developing infant who is not yet walking unsupported can practice shifting body weight onto and off of each foot
more than 1,000 times per waking hour, for hundreds of hours, before attempting to take his or her first steps. The infant
begins to master control of his or her body center of mass (COM) both in space, and in relation to his or her feet while
gaining muscle strength to carry body weight on one foot at a time and then while in motion. This fundamental skill can take
as long as 10 years to master fully.
In children with diplegic cerebral palsy (CP), the equinus gait pathology often begins with a poverty of movement strategies
and weight shifting practice in early infancy. The length of gestation also plays a role in childrens foot development: children
born before developing full ankle DFROM tend toward PF, while children born ful l-term are better able to load their heels in
supported standing. Children with CP commonly retain and build their postural control and movement skills upon the
immature pattern of body weight distribution over the forefeet, with little or no loading on the heels. This anterior weight
displacement delivers input to the pressure and mechanoreceptors in the medial forefeet that signal the somatosensory
system to activate the antigravity righting reaction. This happens in the form of muscle recruitment of muscles on the dorsal
side of the limbs and trunk, and on the lateral sides of the feet. As long as body weight is anterior on the feet, the calf
musculature remains switched on by the need to maintain balance rather than to decelerate the tibia in midstance and
contribute to propulsion. As long as the foot is aligned in pronation, the body COM is drawn forward and medially on the feet
by virtue of the pronatory motions of the calcaneus and talus. Soft tissue stiffness and contractures of the posterior andlateral leg compartment musculature emerge over time via physiologic adaptation to the prolonged, tonic, use history.
Comparative analysis
In a landmark gait study by Sisson et al in 1994, gait analysis and EMG were used to record the activation of the medial
gastrocnemius (MG) muscle belly in two 10-year-old boys one with diplegia and one without diplegia. Each child walked
with his body COM displaced anteriorly, and again aligned more optimally. Both participants showed a tonic MG activation
while walking with weight line forward such that the nondisabled boy might be deemed spastic by the look of his EMG
record and both showed a significant normalization of the activation pattern when walking with weight line more posterior.
The boy with diplegia showed evidence of continued tonic though diminished recruitment of the MG with weight line back,
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Proper intervention for equinus deformity
involves aligning the foot joints for optimum
weight loading.
but he also showed evidence of an emerging propulsion power burst.
A major objective of revising the design of an AFO according to the new
paradigm is to retrain the child to move his or her body weight back to a
more normal and efficient orientation over the feet, and in so doing, to:
deliver more normal and appropriate somatosensory input to the
heels and load-bearing limb joints;
relieve the triceps surae, toe flexors, and other dorsal muscles of
antigravity righting and balancing work; and
allow the posterior compartment muscles to relax and lengthen via
physiologic adaptation to the new history of use that featuresthe
presence of a more efficient postural al ignment.
In an effort to determine the optimum candidates for effective tuning of
AFOs and footwear, in 2007 Penelope Butler et al, undertook a
retrospective review using video records of 21 independently walking
children with CP. Using real-time force vector and other forms of
computerized gait analysis, all 21 chi ldren showed a ground reaction force
vector (GRV) in front of the knee during midstance when barefoot they
hyperextended the s tance knee.
The effectiveness of AFO tuning was judged by optimization of the GRV atthe knee, and showed that there were two groups of prospective candidates
based on knee kinematics. Those who optimized the GRV showed knee
flexion less than or equal to 20 in the first third of stance combined with
movement towards knee extension in the second third of stance that
brought the knee to less than or equal to 10 degrees flexion. So, as is
usually the case, the children with milder postural and movement problems
showed better tuning effects than those with more significant kinematic
deviations.
Improper treatment
In light of new information, equinus deformity has been mistreated for as
long as it has been treated at all. In my experience, and with few exceptions,
orthotists fill prescriptions from physicians for either solid or articulatedAFOs that block the ankle from plantarflexing past 0, presumably because
they think that ankle PF is the problem.
Children with shortened gastrocnemius muscles are usually molded for
AFOs while sitting with the knees flexed and the gastrocnemius muscle off
tension. Then, wearing the AFOs that prevent PF, the child steps onto a
battlefield. Since the gastrocnemius is a competent knee flexor, short
gastrocs impede knee extension when the ankle is held at 0. Efforts to
stand straight raise the heel in the AFO, which is built to resist just that. The
foot joints take the DF strain and usually pronate within the AFO. Foot
pronation brings and keeps - the body COM forward anatomically and
biomechanically. Boney prominences rub against the plastic at the medial midfoot and lateral forefoot. No one is happy not
the child, the caretaker, the therapist, or the orthotist. Requests to revise the AFOs to improve comfort are difficult to satisfy
with the ankle limited to 0 PF. AFOs that block ankle PF and impose foot pronation can cause additional problems because
they impede functional use of the feet and ankles, provoking therapists to remove them during treatment sessions. If they limit
optimum function or hurt, the children might refuse to wear them, or complain enough that caretakers remove them right after
school.
A more effective orthotic strategy
Children with equinus deformity must learn to carry their body weight less anteriorly. Designing an AFO to allow some degree
of PF is appropriate as long as the heels are taking more weight than the metatarsal heads in the standing position and in the
early stance phases of gait. If the ankle must be positioned in greater than 10 PF in the AFO, it is preferable to prepare the
ankle and foot first with a short course of serial casting in which the foot ankle angle, the shaft angle to the floor, and the
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Improper treatment for equinus deformity
involves blocking the ankle from plantarflexing
past 0.
plantar surface of the cast are al l designed ( tuned) for optimum weight
loading through the foot. If serial casting is not possible, then the sole of the
shoe that is worn with a tuned AFO set in greater than 10 PF should be
made stiff at the toe end, and if possible, longer than normal, to resist early
anterior carriage of the body COM over a foot that has been effectively
made too short by the ankle plantarflexed position.
Setting the foot joints in stable alignment, the ankle with a shortened
gastrocnemius muscle in PF in an AFO, and filling the space under the heelwith a lift, improves the likelihood that the heel will be weight-loaded easily
and often, providing the foot with more normal proprioceptive input. Using
an AFO with the ankle set in PF will not increase equinus deformity if the
orthoses are used to support a postural retraining program designed to
reduce day-long, tonic calf muscle recruitment for balance. If body weight is
better aligned over the heels, the calf musculature no longer needed
primarily for balance against falling forward can recover a healthier length
and extensibility. The significant improvements in ankle DFROM due to
serial casting, undertaken as described above, are evidence of the potential
influence on DFROM of proper AFO and footwear tuning combined with
weight-line distribution and weightshift training.
The time has come to regroup, to review the news about the somatosensory
system, the postural control mechanisms, and the influence of standing foot
position on body weight orientation over the feet, and to forge a new and
more effective orthotic strategy one that normalizes weight loading
through the feet, particularly the heels and promotes the acquisition of
balance control as a background function that supports effective movement.
For more information:
Adolph KE, Avolio AM, Barrett T, Mathur P, Murray A. Step
counter: quantifying infants everyday walking experience.
Infant Behavior & Development. 1998. 21: 43.
Aharonson Z, Voloshin A, Steinbach TV, Brull MA, Farine I.
Normal foot--ground pressure pattern in children. Clin
Orthop Relat Res. 1980; 150: 220-223.
Bertsch C, Unger H, Winkelmann W, Rosenbaum D.
Evaluation of early walking patterns from plantar pressure
distribution measurements. First year results of 42 children.
Gait Posture. 2004;19(3): 235-242.
Butler PB, Farmer SE, Stewart C, Jones PW, Forward M.
2007. The effect of fixed ankle foot orthoses in children with
cerebral palsy. Disabil Rehabil Assist Technol. 2007;2(1): 51-58.
Cavanagh PR, Rodgers MM, Iiboshi A. Pressure distribution under symptom-free feet during barefoot
standing. Foot Ankle. 1987; 7(5): 262-276.
Cusick B. Serial Casting and Other Equinus Deformity Management Strategies for Children & Adults
with CNS Dysfunction. Telluride, CO: Progressive GaitWays, 2010. Available at: www.gaitways.com
Grant-Beuttler M, Palisano RJ, Miller DP, et al. 2009. Gastrocnemius-soleus muscle tendon unit
changes over the first 12 weeks of adjusted age in infants born preterm. Phys Ther.
2009;89(2):136-148.
Hennig EM, Rosenbaum D. Pressure distribution patterns under the feet of children in
comparison with adults. Foot Ankle. 1991;11(5):306-11.
Owen E. The importance of being earnest about shank and thigh kinematics especially when using
ankle-foot orthoses. Prosth Orthot Intl. 2010; 34(3):254-269. Available at: http://poi.sagepub.com
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/content/34/3/254.full.pdf
Owen E. The importance of being earnest about shank and thigh kinematics especially when using
ankle-foot orthoses. Prosth Orthot Intl. 2010; 34(3):254-269. Available at: http://poi.sagepub.com
/content/34/3/254.full.pdf
Sisson GA Jr, Weck M, Prihoda W, et al. The effect on gait of an anterior placement of the whole body
center of mass. Gait Posture. 1994; 2(1):56. Poster.
www.bracemasters.com
http://symposiet.files.wordpress.com/2010/05/bowers-presentation.pdf
Beverly Cusick, PT, MS, COF, is the president of
Progressive GaitWays and authorof several
publications, including Serial Casting and Other
Equinus Deformity Management Strategies for
Children and Adults with Central Nervous System
Dysfunction (2010). She can be reached at
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