Slipped capital femoral epiphysis (SCFE) is a condition that affects the hip in teenagers between the ages of 12 and 16 most often. Cases have been reported as early as age nine years old. In this condition, the growth center of the hip (the capital femoral epiphysis) actually slips backwards on the top of the femur (the thighbone).
If untreated, serious problems can occur in the hip joint later in life. Fortunately, the condition can be treated and the complications avoided or reduced if recognized early. Surgery is done to manipulate or reduce the epiphysis. This means the surgeon puts the slipped part of the growing bone back in place. It’s held there with long pins or screws. The procedure helps stabilize the hip and prevent the situation from getting worse.
The subject of this study is the unstable SCFE. Without good placement of the capital femoral epiphysis, loss of blood supply to the area can result in osteonecrosis (death of bone). In fact, six out of 10 children with an unstable SCFE develop osteonecrosis. The long-term effects of osteonecrosis can be very severe.
Surgeons have developed a way to treat an unstable SCFE. They decompress the hip by performing an arthrotomy. Decompression takes pressure off the joint. During an arthrotomy, the surgeon cuts into the joint and may remove some or all of the joint capsule surrounding the joint. When the joint capsule is cut away or removed, it’s called a capsulotomy. Reducing pressure inside the joint with an arthrotomy and capsulotomy greatly reduces the risk of osteonecrosis.
The theory behind this approach is that high pressure in the hip joint is present with unstable SCFE. Bleeding occurs into the joint forming a hematoma (pocket of blood). Releasing the build up of pressure from this intracapsular blood by doing an arthrotomy reduces the risk of osteonecrosis.
In this study, orthopedic surgeons measured the pressure inside the hip joint of 13 children with unstable SCFE. They also measured the pressure inside the hip capsule on the uninvolved side for comparison. Both measurements were taken twice to confirm the reproducibility of the test.
When the mean arterial pressure (MAP) (inside the joint) was more than 30 mm Hg, the joint capsule was released. Intracapsular pressure was measured again after reduction of the SCFE and capsulotomy. In the case of the 13 children in this study, all but one capsulotomy reduced the capsule pressures significantly.
The authors suggest that the results of this study show how manipulation or reduction of the slipped capital epiphysis without decompression is what leads to the loss of blood supply and death of bone. In the past, it was thought that the original injury (not the treatment) was what lead to osteonecrosis.
It is important to stabilize the slipped capital femoral epiphysis but this must be done in such a way as to avoid causing a build up of fluid inside the hip joint. High intraarticular pressures block circulation resulting in osteonecrosis.
Immediate surgical treatment is needed for an unstable SCFE. The authors advise surgeons to perform the capsulotomy even before reducing and fixing the slipped epiphysis. Measurement of capsular pressure should be taken after the capsulotomy to make sure it is below the danger zone. Even with these precautionary steps, osteonecrosis can still occur. The authors advise warning parents of this (and other possible) complications before and after surgery.
Future studies are needed to continue examining this problem. The position of the hip when intraarticular measurements are taken may make a difference in outcomes. For example, in this study, the children’s uninvolved hips were in a position of internal rotation. But the hips with the unstable SCFE were measured in external rotation and slight flexion. This was the position of greatest comfort for the child.
Long-term studies must also be done before adopting this approach for all children routinely. The surgeons who performed the study did think that the short-term data would be of great interest to other surgeons treating children with this problem.