FIBULAR HEMIMELIA (aka FIBULAR DEFICIENCY)
Jill Flanagan, M.D.
Introduction: Fibular Hemimelia (FH) is a congenital (occurs at birth) condition in which the hallmark is that all or part of the fibula bone in the leg is missing. It can be associated with other physical abnormalities as described below, but it is rarely associated with other medical problems. Not only is the fibula bone missing to some extent, but the leg is also thinner and shorter. Most of the time, it affects only one leg, but it may affect both sides. There are several other differences associated with fibula hemimelia. These include partial or complete absence of the anterior cruciate ligament (ACL) in the knee, congenital short femur, ankle instability, and loss of some of the outer bones of the foot resulting in less than 5 toes. In more severe forms, there may also be a dimpling of skin and crookedness of the tibia bone.
Anatomy: The fibula is the thin bone in the outer portion of the leg. The larger, thicker bone is the tibia. With fibula deficiency, some, or all of the fibula bone is missing as depicted in the radiograph.
Etiology/Cause: The cause of FH is not known. Studies have shown that several genes can be mutated to lead to the abnormal leg formation, but these are not inherited or passed down from parents to child. It is therefore very rare that a child with FH has a mother or father with a similar condition, and the child is generally not at risk of having children with FH.
Symptoms: Many children with FH can be diagnosed at birth or soon thereafter. The deficiency does not cause pain. The difference in limb lengths is often noticeable at birth.
Physical Examination: the major physical hallmarks of FH are the following:
- Limb length difference
- Possible absence of toes
- Abnormal ankle joint
On exam, the lower leg (knee to ankle) is smaller and thinner. There is often a curve in the lower leg, and sometimes there is an associated dimple on the skin. Often, the thigh is shorter in length as well. The knee joint often has no ACL, and so it will feel “loose” on exam. The ankle joint may be stiff, and it may be pointed down and out (everted). There may be absent toes on the outer portion of the foot as well.
Imaging Studies: The orthopaedic surgeon will likely x-rays from hips to ankles. On these x-rays, the doctor can measure the difference in limb length, the crookedness of the limb, and evaluate for abnormalities in the foot and ankle. Radiographs are repeated often as the child grows. When the child is younger, it is possible that the surgeon may recommend an MRI of the ankle joint, and possibly the knee joint. There are times when bones in the foot and ankle are “stuck together” (known as a tarsal coalition), and prior to reconstructive surgery, the doctor may want a better look at this joint.
Treatment: Treatment in general depends upon the function of the hip, knee, and ankle joints, as well as the current and final projected limb length differences. Most children with FH will have projected differences at skeletal maturity > 2 inches. In fact, many children have final differences projected at 4-6 inches. The difference in leg lengths generally increases in proportion to the child’s overall growth so the final discrepancy can be predicted. This difference will often need to be treated because differences greater than ¾” may lead to painful problems in the future.
In general, the goal for children with differences in limb lengths is to have two limbs nearly equal in length and as functional and pain-free as possible by the time a child is fully grown. To achieve this goal, first the surgeon must examine the child for the function of his/her surrounding joints, and then calculate an estimated final projected difference. Based on this information, the decision then is made between the orthopaedic surgeon and the family whether a limb lengthening and reconstruction is the best option for treatment, or possibly a limb ablation (amputation) and prosthetic fitting. If limb reconstruction is chosen, your doctor will walk you through a “life plan” that discusses the surgical procedures recommended for your child and the anticipated timing of these surgeries.
The decision for limb ablation (amputation) versus reconstruction is obviously a very critical decision and should be discussed thoroughly with an orthopedic surgeon familiar at managing these limb length differences. The greater the projected difference, the more limb lengthening surgeries are needed to even out the limbs. In addition, most of the time, for the limbs that are very short initially in comparison to the other side, the joint may be more abnormal, and even if they can be “fixed” they may be painful and not as functional as a prosthesis. Again, there are many, many factors that weigh in to this decision, and consultation with a limb deformity specialist is recommended.
Nonsurgical Treatment: There is very little role for nonsurgical options for the ultimate treatment of FH, unless the ankle joint is essentially normal and the projected final difference between the limbs is less than ¾”. However, there are nonsurgical treatments needed for every child with FH.
- Physical Therapy: For every child with FH, physical therapy will be a necessity, whether it is to learn how to walk with a prosthesis or how to keep the knee and ankle limber during a limb lengthening surgery.
- Orthoses/Shoe lifts: Many children that are undergoing limb lengthening will need orthotics and shoe lifts to help “even out” the limb lengths during childhood. Internal shoe lifts can be made up to ½”. Lifts greater than ½” need to be placed outside of shoes, because the heel will not fit in the shoe otherwise. In addition, the child may need a brace such as a supramalleolar orthosis (SMO) or ankle foot orthosis (AFO). SMOs provide side to side ankle support, while AFOs provide more support to the bottom of the ankle. Your physician will prescribe the appropriate brace for your child.
- Prosthetic Fitting: If limb ablation is ultimately the decision made to treat a child with FH, then they will need long term care with a prosthetist. A pediatric prosthetist with experience working with children after amputations for FH is certainly preferable. Prosthetic technology continues to advance at a rapid rate. In addition, as the child ages, the prosthetic options also increase over time.
- Limb Ablation – If the decision is made to amputate the limb in a growing children, amputations are typically made through a joint rather than through a bone itself. The two most common types of amputations are either a Symes or a Boyd amputation through the ankle joint. Both of these preserve the heel pad to provide a good surface to interface with the prosthetic. Once the child heals from the amputation surgery, he/she is fitted for a prosthesis. The surgery can be performed as young as 10 months, right before the child is pulling up to stand. If needed, the surgery can be delayed as well, especially if a family needs more time making this decision.
- Epiphysiodesis surgery – An epiphysiodesis is a surgery performed to stop the growth on the longer leg. This procedure “shortens” the longer leg. It is typically recommended for projected limb length differences between 2-5 cm (3/4”-2”), while lengthening is preferred for differences of greater than 2”. In this procedure, the growth area (physis) is drilled surgically. The growth area is made of cartilage, and after the surgery, the cartilage hole heals itself, but fills in with bone. Once bone fills up this hole, the bone can no longer grow. Some surgeons also use metal implants as a part of this procedure. The surgeon may also recommend epiphysiodesis as part of the “life plan”. For example, if a child has a projected 12 cm limb length difference, the surgeon may recommend 2 separate 5 cm limb lengthenings, and then an epiphysiodesis of the longer (normal) side when there is 2 cm left of growth to make up the remainder of the difference.
- Limb lengthening/reconstruction
- Ankle reconstruction: The term “superankle” was first coined by Dr. Dror Paley in 1996. The surgery itself has been modified from time to time since then. Nonetheless, the superankle surgery refers to an ankle joint reconstruction performed prior to limb lengthening. Prior to any limb lengthening, whether it is for FH, femoral deficiency, etc., the joints need to be in as normal of a position as possible. Specific to FH, as mentioned above, the ankle joints are often abnormal. Many have contractures that point the foot down and out (equinus and eversion), and many times there is a tarsal coalition in which two of the foot bones (typically the calcaneus and talus bones) are stuck together. During this ankle reconstruction surgery, the gastrocnemius muscle and peroneal muscles are often lengthened, the tarsal coalition is released, and many times, the bottom portion of the ankle joint is realigned (known as a supramalleolar osteotomy). Lastly, a portion of the anlage (the cartilaginous remnant of the fibula bone) is also removed. After the surgery, the surgeon may place a child in a cast and allow the ankle to heal. Some surgeons will place an external fixator on at this time and begin the limb lengthening process. There are pluses and minuses to each method, and further details should be discussed with the surgeon.
- Limb lengthening with external fixator: please review the limb lengthening section for further details on limb lengthening with an external fixator.
- Limb lengthening with internal lengthening nail: please review the limb lengthening section for further details on limb lengthening with an internal lengthening nail.
Recovery/Rehabilitation: Recovery depends upon the surgery performed.
- Epiphysiodesis: Recovery after this surgery is relatively easy. The child can go home the same day of the surgery and can typically bear full weight immediately after the surgery. After 2-3 weeks the child can typically return to full activities. Physical therapy is rarely needed.
- Limb lengthening with external fixator: This surgery is complex and the recovery extensive. The longer the lengthening, the longer the external fixator is in place, and therefore, the longer the recovery. Please review the limb lengthening section for further details.
- Limb lengthening with internal lengthening nail: like the external fixator, lengthening with an internal lengthening nail is also an extensive process. However, for the most part, especially in older children, the nails are better accepted and less cumbersome. Please review limb lengthening for additional information.
Final Thoughts: Children who have FH live happy and fruitful lives, no matter whether they have a limb reconstruction or an ablation procedure. They can play sports, play with friends, and generally have normal intelligence and life expectancy. In order to optimize their leg function, they should be seen by an orthopaedic surgeon familiar with fibular hemimelia to discuss their treatment options.