Perthes disease is a condition that affects the hip in children between the ages of four and eight. The condition is also referred to as Legg-Calvé-Perthes disease in honor of the three physicians who each separately described the disease. In this condition, the blood supply to the growth center of the hip (the capital femoral epiphysis) is disturbed, causing the bone in this area to die. The blood supply eventually returns, and the bone heals.
The primary goal of treatment for Perthes disease is to help the femoral head recover and grow to a normal shape. The closer to normal the femoral head is when growth stops, the better the hip will function in later life. The way that surgeons achieve this goal is using a concept called containment.
Surgery may be needed in some children to realign the hip and achieve containment. Sometimes it is necessary to surgically dislocate the hip during the procedure. Doing so gives the surgeon a better idea of the full extent of hip deformity and the knowledge needed to realign the bones. The question raised in this study was related to the blood supply to the hip after healing took place.
The authors used MRIs of the children’s hips to determine the location and number of blood vessels to the head of the femur (thigh bone). The MRIs were high-resolution contrast-enhanced to show the path of the main artery and artery branches to the femoral neck and head. They compared the results to MRIs of an equal number of very similar children (matched by age and sex) who had developmental hip dysplasia (shallow hip socket causing hip dislocation).
By using MRIs with three-dimensional (3-D) computer reformatting, the surgeons were able to map the blood supply exactly as the blood vessels inserted on the femoral neck. The blood supply to this area of the hip is called the vascular safe zone. Knowing where this vascular safe zone is located allows the surgeon to avoid disrupting it when surgically dislocating the child’s hip.
They found that children with Perthes disease who had surgery to correct the problem had fewer blood vessels compared with children who had a similar surgical procedure for developmental hip dysplasia. Most of the blood vessels in the children with Perthes disease inserted into the femoral neck through a very narrow pathway.
There is a reason this information about number, location, and pathway of blood supply is important in the treatment of children with Legg-Calvé-Perthes disease. The disease is caused by a loss of blood to the weight-bearing portion of the femoral head via the medial femoral circumflex artery and its branches.
How well these children recover depends on the surgeon’s ability to restore the interrupted blood supply to the hip. Operating within the vascular safe zone (and avoiding further disrupting the arteries bringing blood to the femoral head) when performing a surgical dislocation to correct the hip problem is important in preventing additional problems. In conclusion, careful planning is required for this type of reconstructive surgery, including knowing where the vascular safe zone is located.