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

[email protected].


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