SUFE

Slipped Upper Femoral Epiphysis (SUFE)

Epidemiology

  • Predominantly affects boys more than girls (60:40 ratio) due to delayed physeal closure caused by testosterone.
  • Observed racial variation with higher incidence in Polynesians and Black populations.
  • Mean age of onset: 12 years for girls, 13 years for boys, typically within a range of 6-15 years.
  • Strong association with obesity, with most affected individuals above the 95th percentile for weight.
  • Occurs more frequently on the left side than the right.
  • Approximately 80% of cases are unilateral, with 20% bilateral; however, 20% of unilateral cases may progress to bilateral involvement.

Aetiology

  • Characterized by anterior displacement of the femoral neck on the femoral head, occurring through the hypertrophic zone of the growth plate.
  • Caused by mechanical forces acting on a susceptible growth plate, increasing physeal shear stress.

Mechanical Factors - Obesity - Femoral retroversion - Vertically oriented physis - Enlarged hypertrophic zone

Chemical Factors - Endocrinopathy is likely present to some degree, influencing growth plate susceptibility: - Growth hormone: Increases hypertrophic zone size - Hypothyroidism, hypoparathyroidism, hypogonadism, renal failure, and prior radiotherapy

Classification

Stability - Stable: Weight-bearing possible - Unstable: Unable to bear weight; unstable cases have a 50% risk of avascular necrosis (AVN)

Chronicity - Acute (<3 weeks) - Acute on chronic - Chronic (>3 weeks), typically after physeal closure

Severity (based on Southwick angle) - Mild: <30 degrees - Moderate: 30-50 degrees - Severe: >50 degrees

XR Features

  • Epiphysis is displaced posteriorly and inferiorly with the femoral shaft in varus alignment.
  • Early indicators include a widened, hazy physis, while other classic signs include:
    • KLEIN’s Line (AP view): Trethowan’s sign
    • STEEL’s Blanch sign: Overlap of epiphysis and metaphysis on AP view
    • Widened inferior joint space
    • Apparent size reduction of epiphysis, due to it being situated behind the neck
    • Remodeling, sclerosis, and inferior callus observed in chronic cases

Management Goals

  • Prevent progression of the slip and avoid complications associated with SUFE and its treatments.

Initial Treatment - Non-weight bearing until surgery is performed. - Endocrine screen (U&E, TFT, GH) if: - Young age, valgus SUFE, thin body habitus, relevant medical history, or bilateral involvement is noted.

Stable SUFE

  • Generally, 96% have a favorable outcome with in situ pinning, regardless of severity. Deformity may be corrected later if necessary with osteotomy.
  • Avoiding reduction reduces AVN risk significantly.
  • Preferred method: Single, partially or fully threaded cannulated screw. A single screw is almost as effective as two screws and reduces complications. Aim for the screw to pass perpendicularly across the physis, centering within the femoral head, without penetrating it.

Unstable SUFE

  • High risk of AVN (~50%) and poor outcome in half of cases.
  • Urgent fixation is recommended, ideally within 24 hours.
  • In situ pinning is the preferred approach, though gentle reduction and decompression may be recommended (no consensus).

Prophylactic Pinning

  • Consider for at-risk patients:
    • Younger than 10 years old
    • Endocrinopathy
    • Unstable SUFE
  • PSA above 14 degrees may also indicate a need for prophylactic pinning.

Osteotomy

  • Recommended after skeletal maturity, primarily for symptomatic cases to reduce impingement and enhance range of motion.
    • Intertrochanteric osteotomy preferred due to a lower AVN risk; intracapsular osteotomy is technically easier.
  • Not advisable acutely due to high risks.

Complications

  1. Chondrolysis: Risk increases with screw/wire penetration.
  2. Fracture: Increased risk with multiple wire passes or low screw entry.
  3. AVN: Associated with aggressive reduction and unstable SUFE.

Morbidity from SUFE Deformity

  1. CAM impingement
  2. Early-onset osteoarthritis (OA)

Aftercare

  • Partial weight-bearing for 6–12 weeks, continuing until physeal arrest.
  • Follow-up until skeletal maturity to monitor for contralateral SUFE.
  • AVN occurrence risk reduces significantly after 1 year.
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