I. Slipped Capital Femoral Epiphysis

1. Etiology:

   1. Most common hip disorder affecting adolescents:

      1. 1.5:1 male-to-female ratio:

         • i. Unstable slips: 1:1 male-to-female ratio.

      2. Strong association with socioeconomic level and obesity.

      3. Bilateral 20 to 80%:

         • i. Second slipped capital femoral epiphysis (SCFE) usually occurs within the first year after index slip.

      4. Racial variability:

         • i. Increased incidence in African Americans, Native Americans, Hispanics, and Polynesians.

      5. Age of onset:

         • i. Boys: 12.7 to 13.5 years.

         • ii. Girls: 11.2 to 12.1 years.

      6. Incidence:

         • i. 4.8/100,000 (0–16 years of age).

2. Pathogenesis:

   1. Multifactorial and unknown:

      1. Slippage secondary to collagen disturbance around the pubescent growth spurt: at hypertrophic zone of physis.

      2. Metabolic, endocrine, and mechanical postulates for cause of SCFE:

         • i. Metabolic:

           1. Serum leptin levels:

              1. Elevated in obese patients.

              2. According to Halverson et al, regardless of body mass index (BMI), leptin greater than 4.9 increases the odds ratio of SCFE.

         • ii. Endocrine disorders.

         • iii. Mechanical factors:

           1. Obesity:

              1. Eighty percent of SCFE patients.

              2. May be due to increased loads on physis, morphology, and endocrine disorders in obese patients.

           2. Morphology:

              1. Relative femoral retroversion.

              2. Acetabular retroversion.

              3. More vertically orientated physis.

3. Histopathology and pathomorphology:

   1. Proximal capital physiolysis.

   2. Damage occurs at the zone of provisional calcification (hypertrophic).

   3. Deformity:

      1. Anterior translation, external rotation of the femoral neck (metaphysis).

      2. Posterior, inferior displacement of femoral head (epiphysis).

      3. Variable posterior tilt of the femoral epiphysis.

      4. Varus, extension, and external rotation deformity of the femoral neck.

      5. Rare “valgus slip”:

         • i. Anterior, medial neck translation.

         • ii. Posterior, valgus inclination of the femoral head.

4. Natural history:

   1. Directly related to degree of slip and durations of treatment:

      1. According to Loder et al’s retrospective study of 328 “stable” SCFE:

         • i. Older children had more severe slip (age):

           1. Mild: 12.3 years.

           2. Moderate: 13 years.

           3. Severe: 13.8 years.

         • ii. Duration of symptoms (months):

           1. Mild: 3.5.

           2. Moderate: 7.7.

           3. Severe: 8.8.

         • iii. Regression analysis:

           1. Stable SCFE:

              1. Two times more likely for moderate or severe slip if older than 12.5 years.

              2. If duration longer than 2 months, 4.1 times more likely for moderate or severe slip.

   1. Femoroacetabular impingement (FAI) after SCFE:

      1. Remodeling occurs at head–neck junction:

         • i. Variable degrees.

         • ii. Cam morphology occurs.

         • iii. Regardless of remodeling, damage to anterior chondrolabral junction.

      2. Multiple studies report chondrolabral injury even after mild slips.

      3. Thirty-one percent painful hips in the first decade after pinning.

      4. Hundred percent decreased head–neck offset = 100% cam morphology:

         • i. Less physically demanding lifestyle after remodeling may improve symptoms.

         • ii. Recommended to closely monitor SCFE patients in adulthood for FAI syndrome.

         • iii. Leads to anterior chondrolabral injury:

           1. Severity of damage depends on:

              1. Duration of slip.

              2. Deformity severity.

              3. Activity level.

           2. Damage occurs early:

              1. Basheer et al reviewed 18 patients at mean 29-month follow-up: significant correlation between outcome scores and time to arthroscopy following SCFE; recommend early FAI treatment after painful presentation.

              2. Leunig et al found damage in 13 consecutive adolescent SCFE hips with FAI chondrolabral damage when the metaphysis extends beyond the epiphysis.

         • iv. FAI syndrome may be risk factor for osteoarthritis.

   2. Avascular necrosis of the femoral head:

      1. Devastating and can lead to osteoarthritis.

      2. Associated with physeal stability.

      3. Unstable slips are at 9.4 times greater risk.

   3. Osteoarthritis:

      • d. SCFE deformity role in osteoarthritis:

        • i. Castañeda et al:

          1. One hundred and twenty one stable slips treated with pinning at 20-year follow-up.

          2. Hundred percent had signs of osteoarthritis.

II. Classification System

1. Southwick’s classification system:

   1. Based on head (epiphyseal)–shaft (diaphyseal) angle ( Fig. 15.1 ).

   2. Preslip (widening of the physis; no displacement).

   3. Mild: less than 30 degrees, up to one-third displacement.

   4. Moderate: 30 to 60 degrees, one-third to one-half displacement.

   5. Severe: greater than 60 degrees; greater than one-half displacement.

2. Loder’s classification system: weight-bearing status:

   1. Unstable:

      1. Severe pain.

      2. Unable to bear weight with crutches:

         • i. Fourteen of 30 (47%) unstable hips developed avascular necrosis (AVN).

           

   2. Stable:

      1. Can bear weight with or without crutches:

         • i. Zero percent of stable slips developed AVN.

3. Duration:

   1. Acute: symptoms less than 3 weeks.

   2. Chronic: symptoms greater than 3 weeks.

   3. Acute-on-chronic: acute exacerbation of symptoms in the setting of a chronic slip.

4. Prognosis:

   1. Mild: good prognosis.

   2. Moderate and severe have increased chance of developing arthritis.

III. Physeal stability:

1. Standard is based on inability to bear weight:

   1. Ziebarth et al questioned this:

      1. Retrospective analysis of 82 patients:

         • i. Complete physeal disruption observed in 28/82 hips (34%) at surgery.

         • ii. Acute versus chronic classification: 82% sensitive and 44% specific.

         • iii. Stable versus unstable classification: 39% sensitive and 76% specific.

         • iv. Calls into question current SCFE classification systems and there are more unstable hips than expected based on ability to weight bear.

I. Proximal femoral Physis

1. Zone of provisional calcification (in hypertrophic zone) is damaged.

2. Proximal femur responsible for 3 mm of growth per year.

II. Blood supply:

1. Deep branch of the medial femoral circumflex artery:

   1. Most important blood supply to the femoral head/epiphysis.

   2. Lesser contributions from lateral femoral circumflex artery, artery of ligamentum teres.

I. History

1. Symptoms:

   1. Vague pain:

      1. Groin, hip, and knee pain.

      2. May be severe enough to prevent ambulation.

   2. Limp:

      1. Children presenting with knee pain have a longer diagnostic delay than those with hip pain.

2. Past medical history: evaluate for endocrinopathy:

   1. Strong association with SCFE.

3. Obesity:

   1. Increased awareness in all preadolescent patients with pain.

II. Physical Examination

1. No pathognomonic finding for SCFE.

2. Gait:

   1. Antalgic gait.

3. Seated or supine:

   1. Limited flexion and internal rotation (most frequent finding).