Slipped Upper Femoral Epiphysis

Epidemiology

Incidence between 0.2-10/100 000
M>F 60%:40%
Mean age of diagnosis 13.5 in boys, 12 in girls
Obesity can lead to earlier age of presentation
18-50% of cases can be bilateral
- Of the unilateral cases that go on to develop contralateral SUFE, second slip usually occurs within 18 months of the first

Mechanical factors
- Obesity–> increased shear stress across the physis (obesity is associated with decreased femoral anteversion)
- Femoral Retroversion
- Increased physeal obliquity

Rapid longitudinal growth during puberty due to increased levels of growth hormone
Rapid growth associated with increased chondrocyte proliferation and increase height of zone of hypertrophy. Increased height may contribute to decreased physeal strength
Oestrogen reduces physeal height and increases physeal strength while testosterone reduces physeal strength–> May explain increased incidence in males

Traditional Classification
- Pre-slip
  - Symptoms: Presents as lower limb weakness, limping, exertional pain in hip/groin/knee
  - Examination: Decreased internal rotation and guarding of the hip
  - Investigation: AP pelvic XR and Frog leg lateral may show disuse osteopaenia in ileum and proximal femur
- Acute Slip- 10-15% of presentations
  - Symptoms: Duration <3 weeks. Pain typically too severe to allow weightbearing. Large majority of cases will have had 1-3/12 history of prodromal symptoms of knee/hip/thigh pain or limp
  - Examination: External rotational deformity with shortening and limited range of motion due to pain
- Chronic Slip- ~85% of presentations
  - Symptoms: Groin of thigh pain, walk with a limp. May have had episodes of exacerbations and remissions over several months to years
  - Examination: Antalgic gait, loss of hip internal rotation, abduction and flexion
- Acute on Chronic Slip
(Newer Classification)- Based on physeal stability and ability to weight bear
- Stable SUFE: Child can walk.weight bear with or without crutches
- Unstable SUFE: Child is unable to weight bear; pain limits any attempt to move the lower extremity
  - Up to 50% incidence of osteonecrosis compared to almost 0% in stable SUFE

Stable SUFE
- In situ fixation
  - Single Screw fixation- Most accepted treatment
    - Advantage: Percutaneous placement with minimal soft tissue trauma. High success rate, low incidence of slip progression, osteonecrosis and chondrolysis
  - Multiple screw/pin fixation
    - Higher rate of unrecognised screw penetration compared to single screw
- Bone graft Epiphysiodesis
  - Avoid complications associated with internal pin fixation inc unrecognized pin penetration and damage to lateral epiphyseal vessels, although larger scar and increased blood loss and surgical time compared to in situ fixation
- Hip Spica Cast
  - Immobilsation in bilateral hip spica avoid complications associated with surgical management. Risk of pressure sores, chondrolysis and further slip
Unstable SUFE
- Risk of osteonecrosis higher than stable SUFE
- Consider urgent hip joint haematoma aspiration, closed reduction and single screw fixation
- Followed by 6-8/52 non-weightbearing
Prophylactic fixation of contralateral side
- Risk of contralateral side becoming affected reported as 2335 times higher than the risk of the initial SUFE

Osteonecrosis; increased with unstable SUFE, over-reduction, attempted reduction of stable SUFE, pin placement in the posterosuperior quadrant and cuneiform osteotomy
Chondrolysis- usually secondary to unrecognised pin penetrations through the femoral head

Reference: Aronsson et al ‘Slipped Capital Femoral Epiphysis: Current Concepts’. J Am Acad Orthop Surg 2006; 14:666-679