by Kathleen A. McHale, MD
Kathleen A. McHale, MD, is a Colonel in the United States Army and is chief and orthopaedic program director and director of pediatric orthopaedics, Walter Reed Army Medical Center. She is associate professor of clinical surgery and assistant clinical professor of orthopaedics at George Washington University.
Slipped capital femoral epiphysis is a classic condition of the adolescent hip which is associated with obesity and other situations where the proximal femoral physis is under stress, has increased height, or is weaker. Slipped epiphyses have occurred during or after a rapid growth spurt and are not uncommon in children with endocrinopathies or who have had irradiation, chemotherapy, or growth hormone therapy. The deformity results from shearing within the physis at its weakest area, the zone of hypertrophy.
In situ pinning for treatment of slipped capital femoral epiphysis has become the treatment of choice for the slipped epiphysis which is displaced less than 50 percent to 60 percent; more severe slips may require osteotomy. Other forms of treatment such as closed reduction with spica casting and open epiphysisodesis are less effective or have more complications. One pin fixation is sufficient as confirmed by studies of Kibiolski, et al and Belkof, et al.
In spite of good data and long-term followups of the process and the treatment, there remains the question: "Should the contralateral hip be pinned?" It is obvious that the child with a bilateral presentation needs a bilateral surgery, but it is not clear that pinning of the contralateral hip is truly prophylactic.
What are the chances of having bilateral slipped capital femoral epiphysis? The conventional knowledge was that the incidence of bilaterality was approximately 25 percent (Hansson). Other series have reported higher incidences: Bairaktevic, 20-40 percent; Loder, Aronson, and Greenfield, 37 percent; Koval, 40 percent; and Bora and Zwierzchowski, 48.7 percent. The incidence of bilateral slips in irradiated patients is about 25 percent if the roentgenograms are followed for three years. Slipped epiphysis in endocrine disorders has an extremely high incidence of bilaterality. Loder, Wittenberg, and DeSilva reported on 85 patients with a 61 percent incidence; Wells, et al found that 100 percent of cases of bilateral slipped capital femoral epiphysis in endocrinopathies were eventually bilateral.
Investigators have looked for factors that might serve as predictors for contralateral involvement. Subtle abnormalities of the endocrine nature such as thyroid function have been looked for but series are not consistent with their findings. The mechanics of shearing force at the physis has been studied. There is a natural developmental increase in the physeal slope at ages 9 to 12 when most slips occur. Pritchitt, Perdue, and Dana found an increase in the neck shaft/plate shaft angle on roentgenographs of children with slips and felt that increased body weight in this scenario could create enough shear force to cause a slip. Litchman and Duffy thought that within normal range of activity, the shear force at the physes are well below that necessary to cause a slip. Hansson's natural history study from Sweden showed an increase in bilaterality in males from the country. Perhaps these children who commonly do manual work and who are also overweight have more stress at the hip than their counterparts from the city.
A great majority of children with slipped capital femoral epiphyses are greater than the 90th percentile in weight. If the risk factors are combined, the overweight, athletic or active child, with roentgenographic verticality of the physis could be expected to have a bilateral involvement with time. Timing of symptoms seems to have a play in bilaterality as well. Loder, et al found that 82 percent of the bilateral slips in their series had a shorter duration of symptoms before the first slip if the slips were diagnosed sequentially.
The benefits of preventive surgery must outweigh the risks. The practice of prophylactically pinning the opposite side must be guided by the inconvenience to the patient, by the cost, and the morbidity of the procedure. Pinning both hips presents difficulties with weight-bearing postoperatively. Increased surgical fees can be expected with a bilateral pinning. However, as has been shown with "same anesthesia" bilateral total joint replacement, the cost actually might be less than two separate surgeries, and, certainly, the anesthetic risk is lowered. Pinning in situ is a procedure which is not without its problems although it has been made easier with modern intraoperative imaging. Positioning of even one pin may be difficult in more severe slips. The most feared complication of the technique itself is joint entry, however, windshield wiper loosening of the pin in the neck because of excess length at the entrance point; and subtrochanteric fracture through unused drill holes has been reported. Avascular necrosis and chondrolysis are well known sequelae of slipped capital femoral epiphysis with or without pin fixation, and avascular necrosis has been reported as high as 47 percent in the unstable slip.
In general, pin fixation is considered safe with good, but the long-term followup of pinned slips shows that these hips deteriorate with time and may require reconstructive surgery. Ross, Lyne, and Morawa's series showed good to excellent results up to 20-year post slips, but in 10 of 15 hips followed more than 20 years, there were only fair to poor results with the worst results in the bilateral cases. Risks of surgery may be higher if the second side becomes affected and the diagnosis is missed. Certainly it will be more challenging to pin a slip that is more displaced, and the results may not be as good. Hips with resultant avascular necrosis do poorly. In Krahn's series of 264 patients, 22 developed avascular necrosis and of these all either needed further surgery or had gradual degenerative changes.
The risks of surgery must outweigh the risk of the natural history itself should the second slip go undiscovered or untreated. Ordeberg, Hansson, and Sandstrom's series from Sweden showed that only two of 49 untreated slips needed late reconstructive surgery and only a few patients had work restrictions. Hansson, Jerre, and Sanders, however, showed that 42 percent of untreated slips had degenerative joint disease as measured by joint space narrowing at age 42. It is true that the dead cannot speak, but there is certainly truth in their remains. Cooperman, et al found nine museum skeletons with evidence of slipped epiphysis. Eight of nine had degenerative changes; the severity of those changes was directly related to the severity of the slip. Although treated slips may ultimately result in osteoarthritis, there appears to be a significant chance without surgery.
From all the data available, it can be concluded that patients with a slipped capital femoral epiphysis from an underlying endocrine disorder should have pinning of both sides. A prophylactic pinning rather than planned, staged pinnings will decrease anesthetic episodes and decrease risks in these sick patients. Although most authors have not recommended prophylactic pinning of the contralateral side, the rate of bilaterality, the epidemiology, and the roentgentographic indicators all indicate that patients with one slip should be watched vigilantly. Further experience with newer scanning techniques, such as MRI, to examine physeal changes and ultrasound to document remodeling may discover better early indicators that a contralateral slip is inevitable. As we enter the 21st century, however, cost considerations and long-term outcomes may have more of a hand in the decision-making. Will prophylactic surgery be more cost-effective and give better results than watching and waiting?