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Innovations aid treatment of pediatric limb deformity
Improvements in imaging and new ways to measure the extent of limb deformity may contribute to better outcomes.
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Today’s pediatric orthopedic surgeons are better able to manage the effects of
congenital and acquired musculoskeletal deficiencies, ones that deform or
otherwise affect normal development and growth of soft tissue and bone, due to
improvements in imaging and correction methods. As a result, outcomes are
gradually improving.
“Correction of deformity can be difficult. But providing you have a clear set of principles and you have clear aims, then you’re likely to get good results,” according to Robert A. Hill, FRCS, a pediatric orthopedic surgeon at Great Ormond Street Hospital for Children NHS Trust in London.
Hill discussed the causes of limb deformities, their management and treatment when he delivered the Naughton Dunn Lecture at the recent British Orthopaedic Association Annual Congress. Among the causes of limb deformity in the pediatric population are poliomyelitis, clubfeet, Blount’s disease, osteogenesis imperfecta, osteopetrosis and various types of bone dysplasia.
Causes, types
Limb deformity has either a congenital or an acquired cause. Acquired causes include infection and inflammation or iatrogenically caused deformities, such as from over or under correcting clubfoot deformity. Deformity may occur in either bone or soft tissue. Hill cited fractures and malunions as examples for bone and muscle spasms and scar contracture for soft tissue.
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“In children, deformity and
treatment can be modified by growth of the growth plate.” |
“Soft tissue deformities are dynamic or fixed. Dynamic deformities are ones that can be passively corrected by the examiner, perhaps under anesthetic … whereas a fixed deformity is one that would not be correctable except under general anesthesia,” Hill said. Bone deformities are typically treated with an osteotomy or other reconstructive technique to straighten or lengthen the bone.
Managing deformities in children may be challenging. “A basic difference between managing deformity in an adult and a child is that in children, deformity and treatment can be modified by growth of the growth plate,” he said. Except in a few rare cases, crossing the growth plate with a device or bone cut should be avoided.
Specific aims for treating deformities that take into account the need for a functional treatment are essential, Hill said. “If you don’t have any idea of what the patient’s aims are or the patient’s goals are, you may find you’re in a position where you cannot satisfy them.”
Two recent advances have helped clinicians treat these children: center of rotation angulation (CORA) measurements of the affected limbs and newer bone transport and lengthening methods, such as the Taylor Spatial Frame fixator (Smith & Nephew). He called the color-coded frame, which can simultaneously correct different types of deformity including shortening, “a significant advance."
CORA is a system of quantifying a patient’s limb alignment, particularly in the legs, by drawing lines on long, standing radiographs taken with the patellae facing forward and the pelvis level. The surgeon draws the mechanical axis by making a line from the center of the femoral head to the center of the talus. “If that line passes outside the knee, then there’s malalignment,” Hill explained.
Determining the magnitude and site of the malalignment involves drawing an additional line across the condyles and seeing where it forms an angle with lines identifying the femoral or tibial anatomic axes. That angle's apex is the CORA. For example, if the lateral distal femoral angle is approximately 81°, then alignment is fairly anatomical and no treatment is required.
Advances in imaging have impacted this area substantially. Internatal ultrasound has helped physicians detect and diagnose congenital musculoskeletal conditions in unborn children and better prepare parents for possible treatment options.
Three-dimensional computed tomography (CT) scans can be used to analyze deformities that are difficult to assess radiographically, Hill said. In addition, models can be created from the CT data to provide surgeons with a way to practice the surgery before actually performing it.
The advent of digital radiographs and some special computer programs has aided in preoperative planning. “The effect from the mechanical axis can be assessed following bone osteotomy, on the computer screen. And, the program will even template the implant for you so you can see where you need to have the osteotomy.”
For more information:
- Hill RA. Naughton Dunn Lecture: Correction of limb deformity in children. Presented at the British Orthopaedic Association Annual Congress. Sept. 15-17, 2004. Manchester, England.