Factors Affecting Slip Progression After In Situ Screw Fixation of Stable Slipped Capital Femoral Epiphysis

Abstract

Background: Slip progression after in situ fixation of slipped capital femoral epiphysis (SCFE) has been reported as occurring in up to 20% of patients. We review SCFE treated with in situ single screw fixation performed at 2 hospitals over a 15-year period to determine the factors associated with slip progression. Methods: This case-control study reviews SCFE treated with in situ single cannulated screw fixation with minimum follow up of 1 year and full closure of the affected physis. Slip progression (failure) was defined as worsening of the Southwick slip angle of 10 or more degrees or revision surgery for symptomatic slip progression. Univariate and multivariate analyses were performed comparing success and failure groups for patient characteristics, screw type and position, and radiographic measurements. Results: Ninety three patients with 108 slips met all criteria, with 15 hips (14%) classified as having slip progression (failure). All failures had 3 threads or fewer across the physis. Five hips had 2 threads across the physis, and 4 of the 5 were classified as failures. Lower modified Oxford bone scores were found in the failure group, though the difference was small (0.9, P = 0.013). Failure was also associated with partially threaded screws (P = 0.001). Failed hips were associated with lower initial Southwick angles (32.8 degrees) than successful hips (40.4 degrees) (P = 0.047). In the stepwise model for multivariate regression, 4 factors were identified as significant, with lower initial number of threads (P < 0.0001), mild initial Southwick category (P = 0.0050), male sex (P = 0.0061), and partially threaded screw type (P = 0.0116) predicting failure. Conclusion:This study is the largest to date evaluating risk factors for slip progression after SCFE fixation, and the first to consider revision surgery for symptomatic slip progression. For stable SCFE, we demonstrate that 4 threads across the physis with a fully threaded screw of 6.5 mm diameter or greater was sufficient to avoid slip progression. We provide a risk stratification for progression of slip showing that in some cases 3 threads across the physis may be sufficient. Level of Evidence: Level III-case-control study.

Socioeconomic Deprivation and its Associations With Follow-up Compliance After In Situ Pinning of Slipped Capital Femoral Epiphysis

“…28,29 In situ screw fixation may also fail in some patients (up to 14% in one series), leading to slip progression and possible revision procedures. 30 Furthermore, in cases of unilateral SCFE upon presentation, the frequency of subsequent contralateral slip is estimated to be between 14% and 40%, markedly higher than baseline SCFE incidence. 13,24 While there is a current debate in the literature regarding the indications for prophylactic treatment of contralateral SCFE, there is consensus that this increased risk must be at least considered.…”

“…This is more common following severe, unstable SCFEs, with a rate of ~24% reported in a systematic review by Zaltz et al27 Even in the absence of avascular necrosis, in situ fixation of SCFE often leaves behind a characteristic “SCFE deformity,” which can cause symptomatic FAI, inhibiting the patient range of motion and increasing the risk of long-term osteoarthritis of the joint 28,29. In situ screw fixation may also fail in some patients (up to 14% in one series), leading to slip progression and possible revision procedures 30. Furthermore, in cases of unilateral SCFE upon presentation, the frequency of subsequent contralateral slip is estimated to be between 14% and 40%, markedly higher than baseline SCFE incidence 13,24.…”

“…While there is a current debate in the literature regarding the indications for prophylactic treatment of contralateral SCFE, there is consensus that this increased risk must be at least considered 11,13,14. All SCFE complications are associated with poor functional outcomes, often leading to subsequent surgical intervention which may range from arthroscopy to total hip replacement depending on the severity of the complication 26,29,30…”

“…11,13,14 All SCFE complications are associated with poor functional outcomes, often leading to subsequent surgical intervention which may range from arthroscopy to total hip replacement depending on the severity of the complication. 26,29,30 There is consensus in the pediatric orthopaedic literature that follow-up at least to skeletal maturity is necessary following in situ pinning of SCFE to allow for monitoring of the aforementioned complications. The femoral head epiphysis fuses between 14 and 19 years of age in males and between 12 and 16 years of age in females.…”

The Etiology and Management of Slipped Capital Femoral Epiphysis

“…However, slip progression following single screw fixation is a potential risk. [45][46][47] Various studies have looked at the biomechanical advantages of single versus double screw fixation in animal models. Segal et al 48 utilized bovine models to recreate reduced and non-reduced slips and tested them against both shear and torsional stress, comparing single versus double screw fixation.…”