Summary

Slipped Upper Femoral Epiphysis (SUFE), also known as SCFE, is the most common hip disorder in adolescents (10-16 years). It involves the displacement of the femoral neck (Metaphysis) anteriorly and superiorly, while the Epiphysis (Head) remains in the acetabulum—essentially, the neck slips forward, leaving the head behind. It classically affects obese males during the pubertal growth spurt. The hallmark sign is Drehmann's Sign (Obligatory external rotation during flexion). Treatment is urgent surgical stabilization (In Situ Pinning) to prevent further slip and Avascular Necrosis (AVN). [1,2,3]

Key Facts

• The "Ice Cream" Analogy: The femoral head is the ice cream scoop, and the neck is the cone. The scoop falls off backwards.
• Knee Pain Trap: 50% of patients present with KNEE pain (Referred via the Obturator Nerve). Always examine the hip in any adolescent with knee pain.
• Stability Matters: The Loder Classification (Stable vs Unstable) dictates prognosis. If they can't walk, the risk of AVN is 50%.

Clinical Pearls

"The Obligatory Roll": When you flex the hip of a SUFE patient, the leg must externally rotate (Drehmann's Sign). This is because the femoral neck impinges on the acetabulum unless it rolls out of the way.

"Don't Force It": Never attempt to manipulate or reduce a chronic slip. You will stretch the retinacular vessels and cause AVN. Fix it where it lies (In Situ).

"Check the Thyroid": If the patient is <10 years old or thin, screen for Hypothyroidism, Renal Osteodystrophy, or Growth Hormone deficiency.

1. Gait

• Trendelenburg gait. Externally rotated foot progression angle.

2. Supine Exam

• Observe resting position: The leg lies in external rotation.
• Log Roll: Internal rotation is blocked and painful.

X-Ray (AP and Frog-Leg Lateral)

• Frog-Leg Lateral: The most sensitive view. Shows the posterior slip clearly ("Ice cream slipping off cone").
• Klein's Line (AP View):
  • Draw a line along the superior border of the femoral neck.
  • Normal: The line intersects a portion of the femoral head.
  • SUFE (Trethowan's Sign): The line passes superior to the head (does not touch it).

MRI

• Used for "Pre-Slips" (Painful hip, obese child, normal X-ray). Shows physeal edema.

                 SUFE DIAGNOSIS
                        ↓
            CAN THE PATIENT WALK?
           (Loder Classification)
           ┌────────────┴─────────────┐
          YES (Stable)            NO (Unstable)
           ↓                          ↓
    URGENT ADMISSION          EMERGENCY ADMISSION
   (Non-weight bearing)       (High AVN Risk)
           ↓                          ↓
    IN SITU PINNING            IN SITU PINNING
  (Single Cannulated Screw)  (Consider Decompression)

The Goal

• To prevent further slipping.
• We do NOT try to put the bone back (Reduction). We accept the deformity and fix it "In Situ".

Technique: Percutaneous In Situ Fixation

• Implant: Single 6.5mm or 7.3mm Cannulated Screw.
• Trajectory: From the anterior neck into the center of the epiphysis.
• "Center-Center": The screw tip should be in the center of the head on both AP and Lateral views.
• Approach to Unstable SUFE: Very controversial. Some advocate "Urgent Reduction" (Dunn procedure) to un-kink vessels, but this is high risk. Most surgeons pin in situ gently.

Prophylactic Pinning?

• Contralateral Hip: 20-40% of patients will slip the other hip within 18 months.
• Indications to pin both:
  1. Endocrine disorders.
  2. Young age (<10) with open triradiate cartilage.
  3. Unreliability for follow-up.

Long Term

• Mild slips do well.
• Severe slips (>50 degrees) almost inevitably lead to Osteoarthritis in 30s/40s due to FAI.
• Unstable slips have a high rate of AVN and poor outcome.

Loder et al (1993)

• Defined the Stable vs Unstable classification.
• Key finding: Instability is the primary predictor of AVN.

BSCOS Guidelines (UK)

• Advocate for single screw fixation.
• Prophylactic pinning should be discussed with parents (Risk of pinning a normal hip vs Risk of future slip).

What has happened?

The "growth plate" at the top of the thigh bone is soft cartilage. Because of growth hormones and mechanics, the ball of the hip has slipped off the neck, like a scoop of ice cream sliding off a cone.

Can you push it back?

No. If we try to force it back, we might snap the blood vessels feeding the bone, causing the bone to die (AVN). This is a disaster. It is safer to fix it where it is.

How do you fix it?

We put a metal screw through a tiny cut in the skin. The screw crosses the slip and holds it tight, preventing it from moving any further until it fuses solid.

What about the other hip?

There is a 1 in 3 chance the other hip will slip later. We can either pin that one now (to be safe) or watch it very closely with X-rays.

Q1: What is Klein's Line? A: A line drawn along the superior border of the femoral neck on an AP X-ray. Normally, it intersects the femoral head. In SUFE, the head is below the line (Trethowan's Sign).

Q2: Which zone of the physis fails in SUFE? A: The Zone of Hypertrophy. Compared to Salter-Harris fractures which occur through the Zone of Provisional Calcification.

Q3: Explain the surgical urgency of Unstable SUFE. A: It is an emergency. The displacement kinks the retinacular vessels. Urgent stabilization is required to prevent progressive disruption, but forceful reduction must be avoided.

Q4: What is Chondrolysis? A: Acute dissolution of the articular cartilage of the hip, causing narrowing of the joint space and stiffness. It is associated with pin penetration into the joint.

(End of Topic)