An External Fixator (or Ex-Fix as it is also known as in the Perthes Disease world) is part of a treatment type known as Distraction or Arthodiatasis. The Ex-Fix works by attaching a mechanical brace to the child’s hip by 6m pins which is inserted through the skin into the pelvis and femur during surgery. This surgery is usually applied during the fragmentation stage.
The brace holds the femur in a specific position allowing some limited natural movement while restricting others in an effort to remove the pressure off the femur head and allowing it to regrow in a circular shape faster.
The Ex-Fix Process:
Children wear the Ex-Fix for approximately 6-7 months in total. The first 6-8 weeks is to make sure the right amount of distraction has occurred for the best possible results. The distraction works by the turning of a special screw daily during this period. The final 4-5 months wearing the Ex-Fix are to allow the femur head to regrow back as much as possible. Children under 13 years are more likely to have the Ex-Fix removed at 4 months while children over 13 years will be closer to 5 months. Physiotherapy is applied daily during this process to retain as much movement as possible in the hip.
The Ex-Fix is then removed under general anesthetic after which another brace must be worn day and night for 6 weeks to allow the bone to strengthen as much as possible with continued physiotherapy. After those 6 weeks the brace is worn only at night for several months until the child has fully recovered all natural movement in their hip.
Sometimes children require a second surgery later known as Femoral Head Reshaping Osteotomy to reshape the regrown femur head from a oblong shape to a more circle shape. The oblong shape while considered a successful recovery from Perthes Disease can still lead the need for hip replacement surgery later as an adult so this new surgery is hoped to prevent that need later. It is also hoped to delay the onset of arthritis even later than the current age of 50 years that the current oblong shape generally presents itself. It is applied for more than just the Ex-Fix treatment but for all Perthes Disease recovery in general.
The Pros of Ex-Fix Treatment:
The idea between the Ex-Fix treatment is to try and short-circuit the healing process which can take several years to under a year and works best for children between the ages of 6 and 15 years. It is considered the treatment of choice for children over the age of 10 because age is not a real factor in the healing process as it is for other treatments. It is a surgery which isn’t as invasive to the hip as other surgeries can be.
The Cons of Ex-Fix Treatment:
The pin sites can be painful and prone to infections. Infections are easily treated with oral antibiotics and good hygiene. The turning of the special screw during the distraction process stage can also be painful. Sometimes Ex-Fix patients require a wheelchair or crutches to ease some of the strain that the ex-fix brace has to carry to prevent pressure occurring on the healing femur head.