Does the number of engaged screw threads affect the stability of slipped capital femoral epiphysis in the in situ fixation?

WOS: 000418200000006Objective: The management of slipped capital femoral epiphysis (SCFE) frequently seen in obese adolescents is fixation with cannulated screw. In this study, it was aimed to evaluate the relationship between the stability of the physis and the number of screw threads passing across the physeal line in the treatment of slipped capital femoral epiphysis (SCFE) with single screw fixation. Methods: Thirty-three hips of 25 SCFE patients who had undergone in situ fixation with cannulated screw were included in the study. The mean age and follow up were 12.33 years (range, 7-16) and 42.24 +/- 16.65 months, respectively. The hips were grouped regarding to chronicity; acute, acute on chronic and chronic slips. The patients were also regrouped regarding the stability of the slip. Pre- and postoperatively both antero-posterior and frog leg pelvis radiographies were evaluated to measure Southwick slip angles and the number of screw threads. Results: Metabolic or endocrinologic pathologies were observed in 13 patients. During the follow up four hips were reoperated due to the insufficiency of the screw threads passing across the physeal line. The mean number of the screw threads was 1,85 (range, 0-3) for the revised hips and 3.87 (range, 2-5) for the rest. The mean slip angle was 37.88 degrees +/- 15.2 degrees preoperatively. Postoperatively, the angle was reduced to 29.00 degrees +/- 16.41 degrees (p=0.0001). Postoperative slip angles were significantly different between chronicity groups (p=0.019). In the acute slip group, mean slip angle was 21.00 degrees +/- 11.08 degrees whereas in the chronic group it was 42.22 degrees +/- 17.98 degrees (p=0.009). Conclusion: It was concluded that in the surgical treatment of SCFE with a single screw, the number of screw threads passing across the epiphyseal line should be at least four; otherwise fixation would not be stable enough