Parents often have anxiety regarding their toddler’s bowed legs and
they search for solutions through the pediatric orthopedist. Reasons for this
presentation can be a natural physiological bowing that will resolve
spontaneously by about the age of 3 years without intervention.
Infantile tibia vara, otherwise known as Blount’s Disease, is
another cause for bowed legs. Blount’s, however, usually does not correct
on its own, but can be treated orthotically and/or surgically. Until the
toddler reaches around 2 years of age, using X-rays to differentiate between
the aforementioned can be difficult due to immature bone, resulting in missed
opportunities for timely treatment. This article will address the
identification of Blount’s and appropriate orthotic treatment practiced
within our facility.
 |
| Anterior view of the KAFO with suggested trim lines encourages three point corrective forces to unload the tibia. |
| Images: Janet G. Marshall, CPO, LPO |
Background
Physiologic bowing can involve curvature of both the femur and the tibia
as seen clinically and in X-rays. Blount’s is isolated to the tibia and is
most evident by the appearance of beaking of the medial tibial metaphysis on
X-ray, where the top slopes down to the inside. Mechanically, this slope
creates an angle at the articulation of the femur and the tibia resulting in
genu varum or bowing. Because this area of the bone has irregularity in
formation, it is susceptible to progressing into a more severe deformity.
Clinically, a common trait is to have ligamentous laxity that presents with a
lateral thrust of the lower leg in ambulation. Additionally girls, children
with a 90th percentile or greater in weight, and children of black or Hispanic
ethnicity have higher risk factors.
Controversy
Orthotic treatment of Blount’s Disease has historically been a
controversial subject. In attempts to add statistical data to the arena, a
study was performed at our facility, Shriners Hospital Tampa, headed by Ellen
Raney, MD. Thirty-eight patients with 60 cases of genu varum were followed
abiding by set criteria to reduce potential inclusion of physiologic bowing.
Each participant was aged between 18 months and 3 years and presented an MD
angle (slope of the beak) of 16·or greater or MD angle of 9· to
16· with presence of lateral thrust secondary to ligamentous laxity or
weight greater than the 90th percentile. These patients were treated
orthotically with an overall success rate of 90%.
Further investigation
In review of the data, some interesting statistics surfaced to support
the efficacy of orthotic treatment of Blount’s disease. Those requiring
surgery (10%) had initial bracing at an average age of 3 years, were evenly
divided with full-time and nighttime bracing, and wore them for an average of
1.2 years. Those resolved with orthotic treatment (90%) initiated bracing at an
average age of 2.18 years, wore them for an average of 1.3 years and were
fairly evenly divided with full-time and nighttime wear. This information
warrants further investigation on the usage of full-time versus nighttime
orthotics and the validity of early intervention.
Compliance
Compliance of wear for bracing for Blount’s is one of the toughest
sells for an orthotist. You have on one side the parents who want their child
to have straight legs, and are willing to try anything to achieve this goal. On
the other side is a toddler who can not be reasoned with, is extremely
proficient at throwing tantrums, can wiggle out of most bracing if allowed, and
can walk and run perfectly without the braces.
 |
| Posterior view of the KAFO with trim lines allows dynamic pull to the tibia. |
Questions of a negative psychological impact for the child wearing
braces arise and facing the challenge of maintaining normal activities pursues.
For these reasons the findings that nighttime bracing produced almost equal
success rates as full-time wear merit consideration for prescription criteria.
Bracing design
Although the etiology of Blount’s remains idiopathic, the
biomechanical forces are felt to be contributing factors of the pathological
cycle. Theoretically, medial pressure on the posteromedial articular surface
inhibits growth and disturbs the ossification process resulting in the
described deformity. In theory, reversing this stress would load pressure on
the lateral surface to inhibit growth and, in conjunction, place a pull tension
on the medial aspect to encourage growth; then correction should ensue.
The current design of the Blount’s brace evolved secondary to the
study. The objectives were to incorporate a KAFO design that would maintain
full extension, place an isolated valgus force on the proximal medial tibia and
control the lateral shift. A full thigh cuff and an ankle hinge that allows
dorsiflexion but limits plantar flexion to 90· were used to accomplish
full extension but not allow hyperextension of the knee. The drop lock at the
knee is present to release the knee for sitting. A lateral sidebar provides
stability for the lateral shift and maintains coronal alignment. To place a
valgus force on the tibia, a flexible calf cuff that extends from the lateral
malleolus proximal to the head of the fibula and wraps slightly anterior is
used. A strap is riveted on this lateral cuff posteriorly then wraps medially
across the anterior tibia to a loop that is placed on the medial sidebar. Full
tension of this strap, as tolerated by the patient, is necessary to complete
the unloading of the tibia.
Nighttime bracing design
This same design can be used for nighttime only by eliminating the knee
hinge. An alternate nighttime brace can be simplified by using a lined ethylene
KAFO night gutter splint that was molded with corrective forces on the tibia.
In the modification process, space is added medially along the tibia. An
elastic pull strap is then riveted inside along the lateral aspect of the tibia
for a dynamic force to unload the proximal medial tibia then attaching it to
the outside medial wall of the KAFO.
Compliance for the nighttime brace obviously is an easier route to take
and has met with proven success. Even if nighttime only bracing is prescribed,
it is still a real challenge for the family to comply. Surgery is an option if
the results are not sufficient to correct the bowing. Unfortunately, if
correction is not attainable for whatever reason, the child may eventually have
painful knees along with the disfigurement. As the orthotist, our job is to
take a good corrective cast and make an orthosis that can provide dynamic
forces to potentially have long-term results. Our role can be strengthened by
the knowledge of past success so we can enlighten the parents and encourage
them in their challenge.
For more information:
- Raney EM, Topoleski TA, Yaghoubian R, Guidera KJ, Marshall JG.
Orthotic treatment of infantile tibia vara. Journal of Pediatric
Orthopaedics. 1998;18(5):670-674.
|
