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Surgical Correction of Blount Disease: One Fixator for All
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Posted on: 11/30/1999
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Bowlegs also known as tibia varum (singular) or tibia vara (plural) are common in toddlers and young children. The condition is called physiologic tibia varum when it's a normal variation and the child will grow out of it. Most toddlers have bowlegs from positioning in utero (in the uterus). This curvature remains until the muscles of the lower back and legs are strong enough to support them in the upright position.
In some cases abnormal growth of the bone causes the bowing to get worse instead of better over time. This condition is called Blount disease or pathologic tibia varum. Blount disease becomes obvious between the ages of two and four as the bowing gets worse. Overweight adolescents or teenagers can also develop this problem.
Blount disease is more than just a cosmetic deformity. Only the medial or inside edge of the bone is affected. In the early stages of Blount disease, this area of bone breaks down and growth stops. Pain develops along with an uneven leg length, which can lead to an altered gait (walking) pattern, tripping, falls, and injuries.
What can be done about it? Treatment depends on the age of the child and the stage of the disease. Between ages birth and two, careful observation or a trial of bracing (also called orthotics may be done. If the child doesn't receive treatment, Blount disease will gradually get worse with more and more bowlegged deformity. Surgery may be needed to correct the problem. For the obese child, weight loss is helpful but often difficult.
Surgical correction may be needed especially for the younger child with advanced stages of tibia varum or the older child who has not improved with orthotics. Surgery isn't usually done on children under the age of two because at this young age, it's still difficult to tell if the child has Blount disease or just excessive tibial bowing.
When surgery is done, an osteotomy is performed. The surgeon removes a wedge-shaped piece of bone from the medial (inside) portion of the femur (thigh bone). It's then inserted into the tibia (lower leg bone) to replace the broken down inner edge of the bone. Hardware such as pins and screws may be used to hold everything in place. If the fixation is used inside the leg, it's called internal fixation osteotomy. External fixation osteotomy describes a special circular wire frame on the outside of the leg with pins to hold the device in place.
Unfortunately, in some patients with adolescent Blount disease, the bowed leg is shorter than the normal or unaffected side. A simple surgery to correct the angle of the deformity isn't always possible. In such cases an external fixation device is used to provide traction to lengthen the leg while gradually correcting the deformity. This operation is called a distraction osteogenesis. The frame gives the patient stability and allows for weight bearing right away.
All of this information leads us to the purpose of this study: to compare the results of different types of external fixation for older children and teens with severe or recurrent Blount disease. Three types of external fixation were used: Ilizarov, Garche T-clamp fixators, and the Biomet Multi-Axial Correction (MAC) Monolateral External Fixation System.
Each of these devices has its own advantages and disadvantages. The authors were particularly interested in seeing how the MAC fared given its ease of application and use compared to the others. The MAC allows for correction of rotational, length, and angular deformities. The patient makes corrections of deformity and length by turning the screws one at a time, four times each day.
In this study, once the surgical correction was made with an osteotomy, external fixation was put in place to make gradual corrections of the leg length. Before and after X-rays were used as the main measure of results. The goal was to evaluate the correction achieved by each type of fixator. Angles and rotation were measured from the side, front/back, and top.
Most of the children had one or more unsuccessful surgical procedures before entering this study. All surgeries were done by one of two pediatric orthopedic surgeons. The numbers of patients receiving each type of fixator were broken down as follows: 20 MAC fixator, 25 Ilizarov, 12 Garche T-clamp, and one other miscellaneous type.
Before starting to use the MAC fixator, the authors reported using the Ilizarov device for children who needed a large amount of correction. They used the Garche T-clamp for less severe deformities. But after using the MAC for all degrees of deformity, they decided to do this study and see if the results with the MAC system were still as good, if not better than the other types of fixators.
The authors reported no difference in results between children with the MAC fixator and the two other main types of fixators used. Complications (both minor and major) were also equal among the different groups. The number of recurrent deformities was similar for all three fixation devices.
There was one disadvantage in using the MAC fixator device. The hardware makes it difficult to see the tibial correction when viewed from above. The authors suggest extra care must be taken to make sure correction of the tibial rotation is achieved when using the MAC system.
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References:
Sylvan E. Clarke, MD, et al. Treatment of Blount Disease. A Comparison Between the Multiaxial Correction System and Other External Fixators. In Journal of Pediatric Orthopaedics. March 2009. Vol. 29. No. 2. Pp. 103-109.
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