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Hip Replacement After Slipped Capital Femoral Epiphysis

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Slipped capital femoral epiphysis (SCFE) is a condition that affects the hip most often in teenagers between the ages of 12 and 16. 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).

Left untreated, this can lead to serious problems in the hip joint later in life. Severity of slipped capital femoral epiphysis (SCFE) can be rated as mild, moderate, or severe. This grading is determined by looking on X-rays at the angle of the epiphysis compared to the other side (if the other hip is normal and not also affected by SCFE).

Another way to classify severity of the condition is by assessing joint stability. Children who can put weight on the hip and walk (sometimes despite pain and/or with or without crutches) are considered to have a stable SCFE. Children with pain so severe that weight bearing and walking are impossible (even with crutches) are considered to have unstable SCFE.

Studies have shown that the more severe the slip, the worse the long-term outcomes. The earlier the diagnosis is made, the more effective the treatment. Fortunately, the condition can be treated and the complications avoided or reduced if recognized early.

Surgery is usually necessary to stabilize the hip and prevent the situation from getting worse. Even with treatment, abnormal joint shape and the resulting impingement (soft tissues structures get pinched) can lead to joint degeneration.

The question has been raised: how many children with SCFE end up with a hip replacement because of severe joint destruction? Is it from degenerative arthritis or avascular necrosis (loss of blood to the hip from the disease)? How soon is hip replacement needed? How long does the joint replacement last?

To help answer these questions, surgeons from the Mayo Clinic in Rochester, Minnesota conducted a review of their medical records from 1954 up to 2007. There were 33,000 patients who had hip replacements during that time period. Only 38 were done in hips with degenerative changes or impingement linked with slipped capital femoral epiphysis (SCFE).

A closer look at these patients showed that a severe slip with avascular necrosis was linked most often with the need for joint replacement. There were some patients with SCFE who needed a joint replacement because of impingement rather than degeneration, but the majority were for damage done by the necrosis.

Hip replacement for necrosis occurred early on (mean time was 7.6 years) compared with a delay of over 20 years for patients with joint degeneration or impingement. And the rate of implant failure requiring revision (a second) surgery was fairly high in the necrosis group as well. The reason for implant failure was usually cup loosening or femoral neck fractures. Success of implant revision was good though -- 95 per cent of the implants were still in good shape five years later.

The authors say this was the first study of its kind -- to show the actual rate of hip replacements in patients who had slipped capital femoral epiphysis (SCFE) as a child. Many of these patients received all of their care over the years at this Mayo Clinic.

What they uncovered with the study was the understanding that hip replacement following a diagnosis of SCFE occurred most often because of hip necrosis not degenerative hip arthritis. Future treatment should be focused on preventing avascular necrosis in severely slipped, unstable hips.

Efforts have already been made to find the best way to accomplish this. Some surgeons have tried cutting the joint capsule while others have performed a stabilization procedure called open reduction and internal fixation (ORIF). Only small studies have been reported so the results are still inconclusive.

The one variable that was difficult to factor into this study was the many changes that have occurred in the way slipped capital femoral ephiphysis has been treated over the years. Implant design and surgical techniques have also changed over the many years between 1954 and 2007.

A closer analysis of these changes might provide additional helpful information for consideration in future cases of slipped capital femoral epiphysis in need of hip replacement. For now, it's clear that patients with unstable slips that develop necrosis are the ones most likely to need a hip replacement (and often sooner than later).

Reference: Annalise Noelle Larson, MD, et al. Avascular Necrosis Most Common Indication for Hip Arthroplasty in Patients with Slipped Capital Femoral Epiphysis. In Journal of Pediatric Orthopaedics. December 2010. Vol. 30. No. 8. Pp. 767-773.

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