Slipped Capital Femoral Epiphysis (SCFE)

Proximal Femoral Physis

The physis is the weak point: The slip occurs through the hypertrophic zone of the physis (zone of provisional calcification is weakest).

Direction of slip: The epiphysis stays in the acetabulum. The metaphysis (and shaft) slips anteriorly and externally rotates. This creates the classic clinical finding of external rotation contracture.

Periosteal sleeve: The posterior periosteum remains attached to the epiphysis, containing the retinacular vessels.

Blood Supply to Femoral Head

Main supply: MFCA (Medial Femoral Circumflex Artery). Branches become retinacular vessels that run along the posterior-superior neck to enter the epiphysis.

At Risk: Any forceful reduction stretches the posterior retinacular vessels. In unstable SCFE, these may already be compromised, contributing to high AVN rate.

Surgical implication: In situ fixation protects the retinacular vessels. Open reduction and realignment procedures risk AVN.

Loder Classification (Stability) - MOST IMPORTANT

Most important classification for prognosis. The stability (ability to weight-bear) is the single best predictor of AVN.

Southwick Angle (Severity)

Measured on frog-lateral radiograph: Angle between a line perpendicular to the capital femoral epiphysis and the femoral shaft axis.

Compare to contralateral hip (subtract normal side angle). Severe slips may develop FAI and require future intervention.

Temporal Classification

Acute: Symptoms less than 3 weeks. Chronic: Symptoms greater than 3 weeks. Acute-on-chronic: Chronic symptoms with acute exacerbation.

Less clinically useful than Loder classification. Stability is more predictive of outcome than duration.

Radiological Investigations

Klein's line: On AP, a line along the superior border of the femoral neck should intersect the lateral portion of the epiphysis. If it does not, the epiphysis has slipped.

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MRI Role

Pre-slip SCFE: MRI may detect physeal widening and edema before radiographic slip visible.

Unstable SCFE: Some surgeons obtain MRI to assess epiphyseal perfusion (predicting AVN), but this should not delay surgery.

Generally not needed for diagnosis in classic cases with positive X-rays.

Stable SCFE Management

Timing: Semi-urgent (within days). Patient should be non-weight-bearing until surgery.

Treatment: In situ single screw fixation.

Technique: Single partially threaded (6.5mm or 7.0mm) cannulated screw. Enter from anterolateral femur. Aim for center of epiphysis on both views. Screw should be perpendicular to physis and engage center of epiphysis.

Post-op: Weight-bear as tolerated. Physis will close over 6-12 months.

Unstable SCFE Management

Timing: Emergency (within 24 hours). Patient should remain on bed rest.

Treatment: In situ pinning with gentle positioning only (NOT active reduction).

Technique: Same single screw technique. Position the leg gently. If some reduction occurs with positioning, accept it - but do NOT manipulate. No traction.

Prognosis: Even with optimal treatment, 47% AVN rate. Counsel family.

Contralateral Prophylactic Pinning

Risk of bilaterality: 20-40% overall.

Consider prophylactic pinning if:

• Younger patient (more growth remaining)
• Endocrine disorder (hypothyroid, GH deficiency)
• Renal osteodystrophy
• Compliance or follow-up concerns
• Contralateral physeal widening on X-ray

Discuss with family: Balance risk of slip vs risk of surgery.

In Situ Single Screw Fixation

Position: Supine on fracture table with fluoroscopy.

Entry point: Anterolateral femur, below vastus lateralis ridge. Entry should BE in line with center of epiphysis on lateral view.

Screw trajectory: Aim for center of epiphysis on both AP and lateral. Screw should be perpendicular to physis (parallel to the slip direction correction if it were to occur). At least 5 threads should cross the physis into epiphysis.

Critical: Check no joint penetration on frog lateral (hip flexed and externally rotated). Screw tip should be greater than 5mm from articular surface.

Severe Slip Deformity Correction

For severe slips (greater than 50-60°) with significant FAI:

Option 1: Accept and address later. In situ pin, let physis close. Perform subcapital realignment or trochanteric osteotomy later if needed.

Option 2: Modified Dunn procedure. Open surgical dislocation with acute realignment of epiphysis. High AVN risk - only at specialized centers.

Option 3: Imhauser osteotomy. Intertrochanteric flexion and rotation osteotomy to correct mechanical axis without touching the physis.

Management of Severe SCFE

Severe slips (greater than 50-60°) create significant deformity leading to FAI and early OA.

Options: In situ pinning remains safest. Address residual deformity later with:

• Femoral neck or subcapital osteotomy (high AVN risk)
• Intertrochanteric osteotomy (Imhauser - safer)
• Cam osteoplasty (arthroscopic or open)

Most surgeons prefer in situ pin and later osteoplasty rather than acute realignment.

Endocrine-Related SCFE

Suspect if: Bilateral, younger than typical age, short stature, delayed puberty, or atypical body habitus.

Screen for: Hypothyroidism, growth hormone deficiency, hypogonadism, renal osteodystrophy.

Higher bilaterality risk: Consider prophylactic contralateral pinning more strongly.

Missed or Late SCFE

Chronic SCFE may present with hip OA symptoms years later due to FAI.

Old healed SCFE with deformity: Consider osteotomy for mechanical correction or cam osteoplasty for impingement.

Avoid osteotomy through the old slip site - high AVN risk even years later.