Background

We analyzed preoperative CT scans of hips with slipped capital femoral epiphysis (SCFE) for characteristics that could be predictive of intraoperative epiphyseal stability and developed a set of imaging criteria for stable and unstable SCFE. We then compared this grading system with the Loder classification.

Methods

We reviewed preoperative CT imaging to develop a SCFE stability classification system. Three orthopaedic surgeons used the classification system to grade stability on a series of SCFE hips. Kappa was used to evaluate intra- and interobserver reliability among the observers. A series of SCFE hips treated with open procedures in which intraoperative stability was determined under direct visualization was evaluated. Intraoperative stability was compared with stability ratings as determined by the CT classification system and the Loder classification system.

Results

Interobserver reliability among our three observers was κ = 0.823 (95% confidence interval (CI) 0.414 to 1.0; p < 0.001). Intraobserver reliability was κ = 0.901 (95% CI 0.492 to 1.31; p < 0.001). In all, 27 hips were used in the comparison of intraoperative stability with the Loder and CT classification systems. CT-predicted stability exhibited 78% concordance with intraoperative stability. The sensitivity and specificity of CT-predicted stability was 75% and 82%, respectively, versus Loder sensitivity of 69% and specificity of 91%.

Conclusion

The CT evaluation method provided is easy to use and can help to improve the accuracy in determining preoperative epiphyseal stability, which may lead to improved treatment outcomes for this population.

Level of evidence

III.