5 Tips for Diagnosing and Managing a SCFE

1. SCFE: DEFINITION, EPIDEMIOLOGY, & ETIOLOGY
  • Disruption of the proximal femoral physis
    • Anterior displacement and external rotation of the proximal femoral metaphysis with variable posterior displacement of the epiphysis, which remains in the acetabulum (1)
      • rare subtype: “valgus slip”: antero-medial neck translation & posterovalgus inclination of the femoral head (1) definition-pic-1.png
  • Most common hip disorder in adolescents (1 to 100 per 100, 000) (2)
  • Affects Boys > Girls (1.5:1) (3.4)
  • Average Age of onset:
    • Boys: 12.7 to 13.5 y.o (3,4)
    • Girls: 11.2 to 12 y.o (3,4)
  • Bilateral slip: 20 to 80%5 – usually asynchronous
  • Pathophysiology
    • Mechanical overloading of a healthy physis
      • Obesity (6)
      • Anatomic characteristics
        • Femoral or acetabular retroversion (7,8)
        • Increased obliquity of the proximal femoral physis (9,10)
    • Normal loading of a weak physis
      • Endocrine or other underlying disorders
        • Consider when age < 10 y.o or > 16 y.o or if BMI < 50th percentile
  • Other risk factors
    • Ethnicity: Black / Native American / Hispanic > White (3)
    • Seasonal variations: higher incidence in summer (11)
    • Regional: USA - higher incidence in the Northeast and West (3,11)

2. DIAGNOSING A SCFE – KEY POINTS: CLINICAL PRESENTATION
  • History
    • Age
    • Groin, thigh or knee pain – acute vs. chronic vs. “acute-on-chronic”
    • Limp – with or without pain
      • Ability to weightbear with or without crutches (Loder Classification) (12)
        • Stable: able to WB (~10% risk of AVN)
        • Unstable: unable to WB (up to 50 % risk of AVN)
        • NB: Loder clinical classification may not correlate with intra-op stability (13)
          • 29% of clinically stable slips were unstable intra-op
    • o +/- history of trauma
    • **** Diagnosis is often delayed: Average time from first physician visit to diagnosis (14)
      • 94 days (non-ortho provider) vs. 2.9 days (ortho provider)
      • Significant delay if knee pain was presenting symptom (110 days vs 59 days: presentation to dx)
  • Physical Examination
    • External foot progression angle
    • “Obligate external rotation”
      • Hip externally rotates when assessing hip flexion
    • Limited hip internal rotation
    • BMI
  • Imaging
    • Supine AP Pelvis and bilateral frog leg views
    • ID slip & Quantify severity of slip (see xray examples below)
      • Klein’s line on AP
        • Line along superior femoral neck should normally intersect the epiphysis
      • Southwick (Head-Shaft) Angle on frog leg lateral (1)
        • Angle between the femoral shaft and a line perpendicular to the epiphysis
        • This angle is then subtracted from the contralateral normal hip
        • In bilateral SCFE: subtract 10 degrees
        • Mild (0–30°), moderate (30–60°), or severe (> 60°)
      • % slip: how much the metaphysis has slipped on the epiphysis
        • Mild: neck displaced < 1/3 diameter of the epiphysis, Moderate: 1/3 to ½; Severe: > ½
      • “Pre-slip”: Widening or irregularity of physis may be the only sign (MRI may be helpful)
      • CT / MRI useful if planning a surgical hip dislocationDiagnosing-pic-1.png






















3. MANAGEMENT GOAL & OPTIONS
  • GOAL
    • STABILIZE the slip to
      • MINIMIZE THE RISK OF AVN
      • PREVENT FURTHER DEFORMITY
        • Existing and further deformity can cause femoro-acetabular impingement, intraarticular cartilage and labral injury, symptomatic degenerative osteoarthritis
      • Eliminate pain
  • OPTIONS
    • In situ pinning
      • Most common technique
      • Stabilize the slip with no attempt to correct the current deformity
      • May require future surgery for symptomatic deformity correction
    • Surgical hip dislocation with acute correction of deformity (Modified Dunn osteotomy) and stabilization of slip (15,16)
      • Option in high volume centers with experienced surgeons to minimize the moderate risk of AVN
    • Open reduction and stabilization (17): described in one center
4. TIPS TO PERFORMING AN IN-SITU PINNING OF A SCFE
in-situ-pic-1.png
  • In situ pinning
    • Might get “serendipitous” reduction
    • No attempt at closed reduction
  • Anterior start on femoral neck
    • At or lateral to the intertrochanteric line
      • To avoid impingement with ROM
  • Cannulated 6.5 / 7.3 mm screw
  • Screw placed perpendicular to physis, center of epiphysis
  • At least 4 threads across physis (in epiphysis)
  • Do not violate subchondral bone
    • “approach-withdraw” test using fluoroscopy
    • screw tip should at least 5 mm from subchondral bone on all views
5. OTHER CONSIDERATIONS
  • Post-operative care
    • Usually protected WB if unstable, WBAT if stable
    • Follow up until physeal closure
    • At follow up visits: always ask about symptoms on the side of the slip and contralateral hip / thigh / knee pain
    • On follow-up AP and bilateral frog leg xrays, look for
      • Slip progression
      • Chondrolysis (narrowing of joint space < 3 mm, usually due to screw penetration)
      • AVN
      • Screw tip position and # of threads across physis
      • Contralateral slip
      • Complications arising from the deformity – FAI
  • Prophylactic pinning of contralateral hip
    • Controversial (18,19)
    • Relative Indications
      • Age : Boys < 12, Girls < 10
      • Underlying disorder (Endocrinopathy / radiation)
      • Poor follow-up potential
      • Modified Oxford Bone Age Score 16-18 or open tri-radiate (20)
      • Posterior sloping angle > 14 ° (21)
      • Posterior epiphyseal tilt > 10 ° (22)
other-considerations-pic-1.png
  • Single vs. Multiple screws
    • Controversial
    • Consider for unstable, displaced hips: 66% stronger fixation with 2 screws (23)
    • Decreased complication rate with one screw (24)
      • 1 screw = 4.6%, 2 screws = 19.6%, 3 screws = 36%
      • Single screw fixation is 77% as stable as double screw fixation
  • Complications
    • AVN
    • Chondrolysis
    • Peri-implant fracture
    • Progression of slip
    • Residual proximal femoral deformity limiting ROM or causing FAI
    • Leg length discrepancy
    • Degenerative OA
    • Contralateral slip





REFERENCES
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