Arthrogram-assisted fixation of slipped capital femoral epiphysis: a CT and radiographic study.

BACKGROUND

Intraoperative fluoroscopy does not always provide the operating surgeon with optimal visualization of a slipped capital femoral epiphysis (SCFE). Arthrography can be used to enhance fluoroscopic images of these patients. This study retrospectively compared the screw placement between patients who received conventional versus arthrographic-assisted in situ screw fixation for SCFE.

METHODS

We reviewed the charts and radiographs of all patients diagnosed with a SCFE at our institution from 2005 to 2010. We isolated those who received postoperative computed tomography (CT) scans to confirm screw placement, and subdivided the patients into 2 groups: those who received arthrograms to facilitate screw placement and those who did not. The screw-tip-to-articular-surface distance was then measured on intraoperative fluoroscopic images and postoperative CT scans.

RESULTS

Seventy-eight patients met inclusion criteria and 24 received an intraoperative arthrogram. Screw placement determined by intraoperative fluoroscopic images did not differ between the 2 groups. When measured on postoperative CT scans the screw-tip-to-articular-surface distance was significantly smaller in the arthrogram-assisted cohort (2.8 vs. 5.2 mm), and the difference between intraoperative and postoperative measurements was significantly greater in the arthrogram-assisted cohort (4.9 vs. 1.6 mm). No cases of intra-articular screw placement were found in either cohort, nor were there any cases demonstrating loss of fixation.

CONCLUSIONS

Arthrogram-assisted fixation of SCFE is a safe and effective tool in patients whose body habitus makes diagnostic fluoroscopic images difficult to obtain. It is, however, not without technical challenges. After the dye is injected it becomes more difficult to visualize the subchondral bone on fluoroscopic images. Our screws were, on average, 4.9 mm closer to the joint space on CT scans than seen intraoperatively. The operating surgeon must be aware of this fact to avoid joint penetration.

LEVEL OF EVIDENCE: Level III.