[The effect of slip grade and chronicity on the development of femur avascular necrosis in surgically treated slipped capital femoral epiphyses].

OBJECTIVES

We investigated the relationship between the grade and chronicity (acute-chronic) of the slip and the development of avascular necrosis (AVN) of the femoral head after surgery for slipped capital femoral epiphysis (SCFE).

METHODS

The study included 424 hips of 269 patients (174 boys, 95 girls; mean age 12 years) who underwent surgery for SCFE and had a minimum follow-up period of one year. The patients were classified according to the severity and chronicity of the slipping using the Southwick classification. The relationship of the slip severity and chronicity with the development of AVN was statistically evaluated.

RESULTS

Involvement was unilateral in 114 patients, and bilateral in 155 patients. The mean follow-up period was 32.9 months. The hips were classified as grade I to II in 267 hips (63%), 120 hips (28.3%), and 37 hips (8.7%), respectively. The symptoms were acute in 130 hips (30.7%), and chronic in 294 hips (69.3%). The incidence of AVN was 4.5% (19 hips; 13 in unilateral cases, 6 in bilateral cases). In logistic regression analysis, a strong correlation was found between the grade of the slip and the development of AVN (odds ratio 10.27; p<0.0001). The acute nature of the slip was also correlated with the development of AVN, but this relation was weaker (odds ratio 0.20, p<0.01).

CONCLUSION

A strong correlation is present between the slipping grade and the development of AVN in SCFE, requiring a closer observation of patients having a high grade slipping in terms of AVN risk. The acute nature of the symptoms represents another risk factor for AVN.