Orthotic management of Blounts Disease

What is Blount's disease?

Infantile Blount's disease is sometimes known as Tibia Vara, or (less concisely) Osteochondrosis Deformans Tibiae. This is a growth disorder of the shin bone (tibia) characterised by inward turning of the lower leg causing bowing that slowly worsens over time.

Whilst it is not uncommon for young children to have bowed legs, typically the bowing will improve with age without intervention. In rare cases, treatment for the deformity is required before skeletal maturity is reached.

In the fashion of medical science where conditions are named after someone of note, Blount's disease was reported by Erlacher in 1922 as a rare, bowed leg deformity and WP Blount identified this in 1937 as a varus deformity specifically associated with the proximal tibia.

Classifying Blount's disease

As you would expect, methods of describing the severity and time-course of the deformity have been described. A grading system, the Langenskiold classification, was developed for chronologically staging the development of Blount's disease.

In 1952, Langeskiold [3] classified the condition in six stages, based on the degree of metaphyseal-epiphyseal changes seen on radiographs; the variations occurred with advancing age.

There are two types of Blount's disease (early-onset and late-onset), based on whether symptoms begin before or after four years of age.

Blount disease may occur in one or both legs and can lead to shortening of the affected leg and other changes within the bones of the legs. Bowing of the shinbone from just below the knee to the ankle is the most common symptom.

This is the result of stress placed on the growth plate at the top of the tibia, causing the bone growth to slow down or stop maturing on the inside of the leg, whilst the outside part continues to grow.

The growth plate, also known as the epiphyseal plate, is made of cartilage (which is weaker than bone) and is the area of growing tissue near the ends of the long bones in children and adolescents who haven't yet reached skeletal maturity. The uneven bone growth causes the tibia to bend outward instead of growing straight.

What's the cause of Blount's disease?

The cause of Blount disease is not known; however, a variety of hereditary and genetic factors are likely to be involved. The condition is more common among certain populations and is associated with obesity and early walking.

Does the deformity need treatment?

A child may not feel any pain at all, but by adulthood this deformity could bring problems; patients may experience discomfort on the side of the knee joint and down the inside of the leg. For children, the biggest impact of Blount's disease is through walking, as one may limp or frequently trip. Regardless of age, if not treated, this condition will lead to progressive deformity and pain.

What treatment options are available for Blount's disease?

Treatment may involve conservative approaches involving orthotic treatment and/or orthopaedic surgery.

The principle of orthotic management in tibia vara, is to alter the abnormal compressive forces created as a result of the condition so that normal growth will resume & the genu varum will be corrected.

The orthosis design needs to be a custom made KAFO (Knee Ankle Foot Orthosis) or in some cases a HKAFO (Hip Knee Ankle Foot Orthosis).

An orthotist will offer an orthosis with the intention to help redistribute the forces on the growth plate to establish normal maturity.

The brace must be worn for roughly one to two years to see changes in the shape of the shinbone. If there is no sign of improvement within the first 12 months, then surgery will be recommended.

What does surgical treatment involve?

Surgery may be suggested if orthotic treatment doesn't produce the desired results. Children with severe deformities and those who are no longer candidates for bracing due to their age, may also need surgery. Several surgeries are available to treat Blount's disease, including tibial osteotomy and hemiepiphysiodeses.

An osteotomy involves surgically cutting and realigning the bone to put it in a more normal position. This type of surgery corrects the deformity immediately but requires post-surgical rehabilitation.

A hemiepiphysiodesis, aims to correct the deformity over time. It involves placing plates or staples on one side of the growth plate to stop the growth on that side. The plate guides the growth of the bone into a straighter position whilst the nonplated side continues to grow. This approach is suggested [4] for those Blount's disease patients who have less than 15 degrees of varus deformity, two years of skeletal growth remaining and less than 1 cm of limb shortening.

Does orthotic treament always work?

It is true to say that no approach can 100% guarantee success but it makes sense to try a more conservative approach before resorting to surgery.

Nonsurgical treatment has been controversial over the years. However, recent studies have indicated success when a knee ankle foot orthosis (KAFO) was used nearly full-time to improve alignment in patients aged <4 years

The efficacy of orthoses with corrective forces and/or distraction systems is related to their ability in relieving weight-bearing stresses on the medial physeal region of the proximal tibia.

Single or double upright KAFOs that apply four or five corrective forces or a distraction system, or variations of these devices, have been described in the orthotic management of infantile Blount's disease.

Alsancak et al [1] reported that a single upright KAFO with a drop lock knee joint was effective for the treatment of tibia vara in 20 children aged up to 38 months. The treatment duration in that study extended for nearly 6 months.

Whiteside [2] (at the time the clinical director of Anatomical Concepts Inc) reported that in 2 children aged approximately 46 months, double, solid, upright KAFOs with free knee motion significantly improved tibia vara after 17 months of treatment. This development by Whiteside became our V-VAS Blount's orthosis.

Our V-VAS? Blount's Orthosis

Our Blount's orthosis is a unique KAFO custom fabricated for young patients with Blount's disease or other conditions affecting the alignment of the lower legs. The design process starts with a custom cast following a specific protocol.

The orthosis uses the dynamic V-VAS? joint system and this allows for sequential correction of the deformity and accommodates growth. Patient compliance is not an issue due to the auto-aligning, free motion and polycentric knee joint capabilities. The orthosis has the ability to isolate and control tibio-femoral alignment in 2 and 4 degree increments.

It is the only system that creates a correction force throughout the full range of knee motion.

The KAFO design is adaptable to incorporate a medial or lateral step lock or drop lock joint opposite the V-VAS? joint to simplify straightening adjustment and increase knee stability if this is needed.

All four uprights have two adjustment screws that will need to be removed to allow for an increase in the corrective force and or growth adjustment as the child’s limb straightens and grows in length respectively.

This ?gure shows removal of the medial calf screws with a Phillips head screw driver. (Note that the plastic has been cut away on the upright for better visualisation).

Correction of Tibia Vara

For isolated correction of Tibia Vara; remove the two adjustment screws from the medial calf upright and move the medial tibial section distally or away from knee center (depicted by arrow) until the desired angle of correction is achieved and re secure the two screws. The distance between each hole results in approximately a 3° angle of correction to the Tibia Vara. The end result of the adjustment is depicted by the broken line as shown in the figure

The schedule of use is best determined by the treating team members.

Some will choose full-time wear - others will feel that day or night wear is appropriate. It is all dependent on what the treating team is most comfortable with for the individual patient.

Follow up is determined by the treating team members as well. In most cases initial follow up is 4 to 6 weeks then at 6 to 12 week intervals to assure that growth and corrective adjustments are made.

Cleaning is done by wiping down the plastic and padded parts with a mild laundry soap and water solution or rubbing alcohol. Use a non abrasive cloth.

The knee joint mechanism can be lubricated as needed with silicone spray.

Conclusion

Non-surgical treatment of Blount's disease was controversial in the past. The primary problems were to do with compliance and the difficulty of maintaining a corrective force. The V-VAS design we describe here has been used successfully in both infantile and late-onset Blount's disease. Contact us for further details

Related Articles

[1] Alsancak, S., Guner, S. & Kinik, H. Orthotic variations in the management of infantile tibia vara and results of treatment. Prosthet. Orthot. Int. 37, 375-383 (2013).

[2] Whiteside, J. W. Successful outcomes using a new free motion KAFO for treatment of infantile tibia vara. JACPOC. 17, 26-29 (2011).

[3] Langenski?ld, A. Tibia vara: osteochondrosis deformans tibiae. Blount's disease. Clin. Orthop. Relat. Res.158, 77-82 (1981).

[4] Sabharwal, S. Current Concepts Review: Blount Disease. JBJS AM, 2009; 91:1758-76

About the Author

Derek Jones PhD, MBA is a Bioengineer and Director of Anatomical Concepts (UK) Ltd. The V-VAS joint and KAFO design was developed by Joe Whiteside and the team at Anatomical Concepts Inc, Ohio USA