Physical Therapy for Children with Achondroplasia

by Sister Celeste Weitzel, P.T.
 

Children who are dwarfs, commonly known as Little People, suffer from a genetic disorder that effects their skeletal development.  At the International Center for Skeletal Dysplasia [see Editor's Note below] in Saint Joseph Medical Center in Towson, Maryland, we see children with varying types and degrees of skeletal dysplasia.  We often receive requests from other clinicians asking what precautions or contraindications should be followed for a dwarfed patient they are treating for the first time.

Achondroplasia, one of the more common types of skeletal dysplasia, occurs in approximately one in 10,000 births.  It is recognizable at birth and can be identified in utero by means of a sonogram.  The physical characteristics which distinguish this syndrome are: a disproportionate body size with a large head, short limbs, occipital bossing (a protuberance of the occipital bone that causes neck flexion in supine), a prominent forehead with a flat or depressed area at the base of the nose and a protruding jaw.  The hands are short, fingers are stubby and there is ligamentous laxity especially noticed at the shoulders, wrists, knees and ankles.  Intelligence is generally normal.

Hypotonia is very evident from early on.  Motor development is delayed.  (See Table 1.)  Head control may not develop until seven to nine months of age because it takes longer to develop the muscular strength needed to control the overly large head.

Table 1:  SKILLS ACHIEVED BY 90% OF CHILDREN ACCORDING TO THE
DENVER DEVELOPMENTAL SCREENING TEST

When an achondroplastic infant is brought to therapy, it is usually because of hypotonia and the delay of motor milestones.  What can a therapist do to help this child and what precautions should he/she take?  One thing the therapist should check is the relationship of the head and neck when the infant is positioned supine.  Does the occipital bossing push the child into a flexed or forward head position, constantly stretching the neck extensors?  If so, advise the parents to place the child so the child's neck is neutral or even slightly extended when supine or in a reclined seat.  Using a small pad under the shoulders and upper trunk is an easy way to prevent cervical flexion.

Another important question is - Has the hypotonia increased?  It should gradually resolve as the muscles mature.  However if it worsens or there is presence of sleep apnea, there may be a compression of the cervical spine.  A common complication of achondroplasia is a narrowing of the foramen magnum, causing compression of the cervical spine.  This needs to be surgically corrected.

As the child develops head control and begins sitting, a kyphosis of the lumbar spine can occur.  This may be corrected with a small back brace (Knight brace).  The Knight brace (Figure 1) is made with and adjustable soft abdominal shield.  This soft abdominal shield allows for abdominal breathing, which is very typical in achondroplasia.

The effectiveness of the brace is due to its three point fixation:

•  It holds the pelvis.
•  It provides paravertebral pressure in an anterior and cephaled direction via a movable posterior  paraspinal pad.
•  It provides counterpressure in an anterior to posterior direction by sternal extensions.

Figure 1: Knight Brace used to control the lumbar kyphosis

The Knight Brace is most beneficial if worn between the ages of 8 to 18 months of age and should be used when the child is in the upright position.  If the kyphosis is not corrected, wedging of the vertebrae may occur leading to significant problems later in life.

Mobility for an infant with achondroplasia can be something of a challenge.  As with most infants, the first form of mobility is rolling.  This rolling may persist longer than usual.  Crawling, the next step in mobility, generally takes a different form.  Because of the heavy head and weak neck muscles, many infants with achondroplasia may choose alternate forms of crawling such as snowplowing, reverse snowplowing or spider crawling.  When snowplowing, the child uses his/her heavy head as a balancing point while the feet and legs push him/her along.  This can be done in prone (snowplowing) or in supine (reverse snowplowing).  When spider crawling, the child uses his/her hands and feet to propel him/herself, as opposed to the more common method of hands and knees.  This form of crawling requires more head control but also puts more stress on the already lax wrists and ankles.  Thus, it is not used as frequently as is reverse snowplowing.

Transitioning from sitting on the floor to standing presents another challenge.  Joint laxity at the knees and ankles make it difficult to stand by first kneeling or squatting.  Instead, the child with achondroplasia will jackknife into an upright position by fully extending the knees in sitting, then bending at the hips, flexing the body forward until the head is on the floor.  Then, once again using the head for balance, he/she will wedge up over fully extended legs, pushing with the legs and extending the trunk until fully upright.  These unusual methods of mobility and transitions should be encouraged, not discouraged.  The therapist should avoid trying to encourage a child to move in more traditional patterns, secondary to ligamentous laxity and weak muscles.  Achondroplasia does not effect the development of soft tissue.  The muscle size is actually the same size as an average child's muscle would be.  However, it is less efficient because of the shorter distance over which it is stretched.

During early childhood, there will most likely be a bowing of the legs.  This is caused by a faster growth rate of the fibula than that of the tibia.  If it is surgically corrected at an early age by removing a small section of the fibula and leaving a gap, no physical therapy is required.  If the problem is not corrected at an early age, joint deformities requiring osteotomies and rehab will be required.  Long leg bracing does not correct the problem and may indeed cause more serious problems requiring extensive surgery as the child matures.  The joint laxity of the shoulders, wrists and ankles may persist into the teen years.

Resistive exercises that might increase this laxity should be avoided.  However, the need to strengthen the musculature around the joint, first with isometric exercise and then with active exercise is very important.  In most cases, the extensor muscles are weak and lengthened, while the flexors are short and stronger.  There is often an anterior pelvic tilt that may increase with age.  This can cause compression in the lumbar spine.  Eventually, the youngster may need to stop and squat while ambulating or standing.  This is one of the indications that spinal stenosis is occurring.  It can be partially corrected with exercise.  Again, using a back brace (a modified Knight brace, see Figure 2) may help to reduce the symptoms, but surgery may be needed.  Learning to do a posterior pelvic tilt and Swiss ball exercises may also give some relief from the symptoms.

Figure 2: Modified Knight Brace with the sternal extensions removed

Another problem that is frequently seen during the teen years and into early adulthood is obesity.  A regular exercise program that is easy on the joints is highly recommended.  Sometimes a dietary consult may be required.

Addressing ADLs, especially personal hygiene, is very important.  Because of the short upper extremities and usually flexed elbows, many children with achondroplasia are unable to reach the top of their head or their perineum for toilet care.  This is more of a problem during early childhood and frequently resolves spontaneously as the child grows.

Once the child is school age, proper seating in the classroom needs to be addressed.  Because the child's femur is much shorter than average, the seat depth of most student chairs is much too long.  Thus he/she may need a cushion or some other form of back support.  Also the chair is generally too high.  The child's feet and legs dangle with resulting tingling and numbness.  A footstool of appropriate height should be kept in each class room for him/her to use.  As the child grows into a young adult and moves onto high school and college an electric scooter may be needed, depending on the size of the campus, to keep up with his/her peers and to make it to class on time.  Dorm rooms may need modifications such as extensions on light switches and lowering book shelves.  In summary then, the problems commonly seen and treated in children with achondroplasia are:

Early years:

•  Neurological symptoms from stenosis of spinal cord and foramen magnum
•  Thoraco-lumbar kyphosis
•  Delayed motor milestones

Childhood:

•  Joint laxity (subluxed humerus)
•  Bowing of the lower extremities
•  Anterior pelvic tilt

Teen years:

•   Lumbar stenosis
•   Independence in ADLs
•   Obesity

For more information on Achondroplasia see the references listed below.

References:

1. Ablon, Joan.,  Little People in America: The Social Dimensions of Dwarfism.  New York: Praeger, 1984.

2. Ablon, Joan.  Living With Difference.  New York: Praeger, 1988.

3. Campbell J, Dorren N.  It's A Whole New View: Beginner's Guide for New Parent's of a Child With Dwarfism.  Washington, D.C.: Little People of America, 1998.

4. Dwarfism: The Family and Professional Guide.  Edited by Richard Crandell, Calif. Short Stature Foundation and Information Center, Inc., 1994.

5. Fowler ES, Glinski LP, Reiser CA, Horton VK, and Pauli RM.  Biophysical Basis for Delayed and Aberrant Motor Development in Young Children with Achondroplasia. Journal of Development and Behavioral Pediatrics, 1997; 18:143-150.

6. Hall JC.  Kyphosis in achondroplasia: probably preventable. Journal of Pediatrics, 1988; 112:166-167.

7. Health Supervision for Children With Achondroplasia.  Pediatrics Journal, 1995; 95: 443-451.  Standards of Care guidelines developed by the American Academy of Pediatrics, Committee on Genetics.

8. Hecht JT, Hood OJ, Schwartz RJ, et al.  Obesity in achondroplasia.  American Journal of Medical Genetics, 1988; 31: 597-602.

9. Kopits SE.  Orthopedic Complications of Dwarfism.  Clinical Orthopaedics, 1976; 114:153-179.

10. Nicoletti, Kopits, Ascani, McKusick.  Human Achondroplasia: A Multidisciplinary Approach.  New York: Plenium Press, 1988.

11. McKusick VA.  Heritable Disorders of Connective Tissue. 4th. edition.  St. Louis: Mosby, 1972.

12. Scott CI.  Achondroplasia.  Human Growth Foundation, 1981.

13. Todorov AB, Scott CI, Wareen AE, Leeper JD.  Developmental Screening Tests in Achondroplastic Children.  American Journal of Medical Genetics, 1981; 9:19-23.

[Editor's Note: The International Center for Skeletal Dysplasia closed in 2002, upon the death of its director, Dr. Steven E. Kopits.]