Prospective Evaluation of in Situ Screw Fixation for Stable Slipped Capital Femoral Epiphysis

Abstract

Background: In situ screw fixation is the standard of care for the treatment of stable slipped capital femoral epiphysis (SCFE), however, recent studies recommend treatment of all slip-related cam deformity to prevent degenerative changes due to femoroacetabular impingement (FAI). Hypothesis/Purpose: The purpose of this study was to prospectively evaluate radiographic and patient reported outcomes after in situ screw fixation for stable SCFE with minimum 2-year follow-up. Methods: After obtaining IRB approval, we prospectively collected data on all consecutive stable SCFE patients who underwent in situ screw fixation at a single institution. Demographic information, Southwick slip angle (SSA) and alpha angle were recorded. The Hip disability and Osteoarthritis Outcome Score (HOOS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were collected. Basic descriptive statistics, the Mann-Whitney test, and correlation analysis was performed. Results: Forty-four hips in 38 patients with an average pre-op SSA of 41.1±20.0˚ were studied. Cohort characteristics can be found in Table 1. We observed no surgical complications of the index procedure and no cases of avascular necrosis (AVN). Twelve hips (27%) went on to have a secondary procedure (SSA range: 34˚ to 101˚) on average 2.6±2.4 years after the index surgery. These were performed to correct residual deformity, limited hip range of motion, or symptomatic impingement; one patient (2 hips) was referred for total hip arthroplasty due to significant degenerative osteoarthritis at 7.8 years follow-up. There were five complications of the secondary procedures (three implant failures and two mal-positioned implants). Our mean post-op HOOS and WOMAC scores were 84.2±16.8 and 87.8±13.9, respectively. Severe slips were 19.3 times more likely to undergo a secondary procedure than mild and moderate slips (p<0.001), however we found no correlation between slip severity and patient reported outcomes (p>0.6). Conclusion: With minimum 2-year follow-up, 27% of patients went on to require a secondary surgery after in situ screw fixation for stable SCFE. Patient reported outcomes did not correlate with slip severity (p>0.6) but were found to be significantly higher in SCFE patients that did not require a secondary procedure (p=0.023). Prophylactic treatment of all slip-related cam deformity was not found to be necessary in this prospective cohort. While in situ screw fixation can be used to safely treat mild to moderate stable slips, patients with moderate to severe stable slips may require secondary surgery and have a higher complication rate with worse patient reported outcomes. Level 2 [Table: see text]