ABCs of MHE - Continued. 

LEGS AND KNEES

 

  • Femur

  • Knees

  • Lower Leg (Tibia and Fibula)

 

The likelihood of involvement near the knee (figures 6 & 7) in at least one of the three locations is approximately 94%.

 

A clinically significant inequality of 2cm or greater has been reported with a prevalence ranging from 10-50%.  Shortening can occur in the femur and/or the tibia; the femur is affected approximately twice as commonly as the tibia.  Surgical treatment with appropriately timed epiphysiodesis has been satisfactorily employed in growing patients. In addition to limb-length discrepancies, a number of lower extremity deformities have been documented.  Since the disorder involves the most rapidly growing ends of the long bones, the distal femur is among the most commonly involved sites and 70-98% of patients with MHE have lesions.  Coxa valga has been reported in up to 25%; lesions of the proximal femur have been reported in 30-90% of patients with MHE.  Femoral anteversion and valgus have been associated with exostoses located in proximity to the lesser trochanter. 

 

Genu Valgum or Knock-knee deformities are found in 8-33% of patients with MHE. Genu valgum is defined as a mechanical malalignment of the lower limb when the knees knock against each other and the legs are pointed away from the body. Although distal femoral involvement is common, the majority of cases of angular limb deformities are due mostly to lesions of the tibia and fibula (Figures 8,9 & 10), which occur in 70-98% and 30-97% of cases, respectively.  The fibula has been found by Nawata et al. to be shortened disproportionately as compared to the tibia, and this is likely responsible for the consistent valgus direction of the deformity. Genu varum or Bowlegs may also occur in some cases. This is defined as a mechanical malalignment of the lower limb when the knees drift away from the body and the legs are bowed and close together.

                  

Diagnostic Procedures

The orthopedist will probably manually feel for exostoses along the leg, and check range of motion (“ROM”) by manipulating (moving) the leg in different directions. The orthopedist will also check measurements on each leg to see if there is a difference. X-rays or other imaging tests may be ordered.

 

Possible Treatment Options

 

  • Minor length discrepancies can sometimes be effectively treated with the use of orthotics (specially made shoes or lifts that will equalize leg length).

  • Bowing and some limb length discrepancies and be treated with a surgical procedure called “stapling,” where surgical staples are inserted into the growth plate of the leg bone growing faster than the other. This will hopefully give the slower growing bone the chance to “catch up” and the limb will straighten over time.

  • Limb Lengthening with a Fixator.   (See Section on Fixators)

  • Excision of exostoses

  • Osteotomy

 

What Parents Should Watch Out For

 

  • Any red flags in terms of sudden increase in size of swelling, pain, nerve compression, tingling, numbness, or weakness.

  • Possibility of exostoses irritating or catching on overlying tissue, such as muscles, tendons, ligaments, or compressing nerves.

  • Leg cramps, bluish color, difference in skin temperature may indicate compression of an artery (most often the popliteal artery, located behind the knee).

  • Compression of the peroneal nerve, which runs along the outside of the leg, can cause a condition known as “drop foot”, in which the foot cannot voluntarily be flexed up.  Compression can be caused by exostoses growth, or as a complication of surgery.

  • Limping, pain when walking

  • Bowing of leg(s)

  • Exostoses on inside of legs bumping into each other

  • Exostoses interfering with normal movements, either by blocking movement or by causing pain (bending, sitting, walking up or down stairs)

  • Pain and fatigue when walking

  • Gait problems (awkwardness, limping, slow movements, etc.)

 

Notes from The MHE Coalition:  A good way to track possible bowing in your child’s legs is to take a photo of your child dressed in shorts, standing straight with back to wall, legs together.  Every few months take another photo of your child in the same position, and date and keep these photos to show your child’s doctor.  You can even have your child hold a sign with the date you take the picture (written dark enough to be picked up by the camera!).

 

ANKLES

 

Valgus deformity of the ankle is also common in patients with MHE and is observed in 45-54% of patients in most series.  This valgus deformity can be attributed to multiple factors including shortening of the fibula relative to the tibia.  A resulting obliquity of the distal tibial epiphysis and medial subluxation of the talus can also be associated with this deformity, while developmental obliquity of the superior talar articular surface may provide partial compensation. 

 

Diagnostic Procedures:

The orthopaedist will probably manually feel for exostoses along the leg, and check range of motion (“ROM”) by manipulating (moving) the leg in different directions. The orthopaedist will also check measurements on each leg to see if there is a difference. X-rays or other imaging tests may be ordered.

 

Possible Treatment Options:

 

  • Minor length discrepancies can sometimes be effectively treated with the use of orthotics (specially made shoes or lifts that will equalize leg length).

  • Bowing and some limb length discrepancies and be treated with a surgical procedure called “stapling,” where surgical staples are inserted into the growth plate of the leg bone growing faster than the other. This will hopefully give the slower growing bone the chance to “catch up” and the limb will straighten over time.

  • In more advanced cases, excision of exostoses with early medial hemiepiphyseal stapling of the tibia in conjuction with exostosis excision can correct a valgus deformity at the ankle of 15° or greater associated with limited shortening of the fibula. 

  • Fibular lengthening has been used effectively for severe valgus deformity with more significant fibular shortening, (i.e. when the distal fibular physis is located proximal to the distal tibial physis). 

  • Supramalleolar osteotomy of the tibia has also been used effectively to treat severe valgus ankle deformity.

  • Growth of exostoses can also result in tibiofibular diastasis that can be treated with early excision of the lesions.

 

What Parents Should Watch Out For:

 

  • Limping, pain when walking

  • Recurrent falls and instability while walking on uneven surfaces.

 

FEET AND TOES

 

Osteochondromas may occur in the tarsal and carpal bones, however they are often less apparent. Relative shortening of the metatarsals, metacarpals, and phalanges may be noted.

 

Diagnostic Procedures

Plain radiographs are probably more useful in defining the extent of involvement of the small bones of the feet in MHE. Other imaging studies may be ordered as and when required.

 

Possible Treatment Options

 

  • Large bumps can be surgically excised when symptomatic

  • Deformities of the foot (like hallux valgus) may be corrected by stapling of the growing epiphysis in younger children or by surgical osteotomy in older patients.

 

What Parents Should Watch Out For

 

  • Compression of the peroneal nerve, which runs along the outside of the leg, can cause a condition known as “drop foot”, in which the foot cannot voluntarily be flexed up.  Compression can be caused by exostoses growth, or as a complication of surgery.

 

Note from The MHE Coalition: Parents should know that finding shoes for children affected with ankle and/or foot exostoses can be challenging.  Shoes must be found that do not cut into or press on exostoses.  In some cases, they must be made specially for the child.   In addition, some children will require lifts to help equalize a limb length discrepancy.   Children who have exostoses on the bottom of their heel can sometimes benefit from gel cushions that are sold in drug/grocery stores.  In addition, many children and teens will have difficulty tying shoes due to affected hands, shortened forearms, etc., and may need shoes with Velcro or shoes that slip on.

 

In general

 

What Parents Should Watch Out For

 

  • If your child is limping, check to see if it is due to an injury, or is something that is occurring and continuing without obvious reason.   Limping may signal a limb length discrepancy or other problem.

  • Bowing of one or both legs

  • Mobility problems.  Is your child experiencing pain when walking or running?

  • Pain.  Is your child experiencing pain from exostoses that bump each other?  Is your child experiencing pain during certain activities, or pain at night.  If so, keep a pain diary.

  • Any red flags in terms of sudden increase in size of swelling, pain, nerve compression, tingling, numbness, or weakness.

 

 

 

What Adults Should Be Aware Of:

 

  • Sudden growth in an existing exostosis and pain can be symptomatic of a malignant transformation.  It is smart to check out any changes with your orthopaedist.  However, it is important to remember that chondrosarcoma is rare.

  • Years of wear and tear on joints can result in chronic pain.  There is also the possibility of exostoses irritating or catching on overlying tissue, such as muscles, tendons, ligaments, or compressing nerves. Possible Treatment Options for these common problems, include pain medications, physical therapy (including stretching, strengthening and modalities), heat, rest, bracing (supportive orthosis acting as load sharing devices) etc.

 

 

 

 

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