Author(s): Edwardo Ramos, MD, Daniel Almodovar-Frau, MD, Ana Ortiz-Santiago, MD
Originally published: April 27, 2022 Last updated: April 27, 2022
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Disease/Disorder

Definition

Slipped Capital Femoral Epiphysis (SCFE) is a hip disorder resulting in posteroinferior displacement of the proximal femoral epiphysis (femoral head) in relation to the metaphysis (femoral neck), through a skeletally immature physeal growth plate. It is characterized by insidious onset dull hip or referred knee pain, usually without preceding trauma.1

Etiology

Etiology is multifactorial with most cases being idiopathic. Obesity is the most common risk factor with 63% of cases above the 90th weight percentile. Mechanical risk factors for SCFE include rapid growth spurts, femoral retroversion, and femoral neck shaft angle. Renal and endocrine abnormalities such as hypothyroidism, panhypopituitarism and renal osteodystrophy are also linked to the development of SCFE.1 Proper development of the physis requires thyroid hormone, vitamin D, and calcium.3

Epidemiology including risk factors and primary prevention

SCFE is the most common hip disorder in pre-adolescents, adolescents, and young adults with an overall prevalence of 10.8 cases per 100,000 children. Prevalence varies widely among race, seasonal and geographic location with higher presentations in the northern and western United States.4 African-Americans,  Pacific Islanders and the Hispanic population have greater predisposition for the development of SCFE than Caucasians.5

SCFE usually occurs during adolescence, typically during the ages of 8 through 15 and is more common in males than females (male to female ratio of 1.6:1) with an average age of 13.5 years in males and 12 years in females.1,4 Presentation outside of these age ranges should raise clinical concern for potential endocrinopathies or chronic conditions that lead to high bone turnover.6

Patho-anatomy/physiology

Pathogenesis of SCFE has many theories, however, the exact mechanism is still to be determined. It is believed to arise due to a mechanical displacement of the proximal femoral head from the femoral neck due to abnormal physiological loads through a skeletally weak and immature physeal growth plate. Insufficiency of the femoral physis can be attributed to mechanical factors, such as obesity, morphologic abnormalities of the femoroacetabular joint and other external variables that increase the axial load and shear forces applied to the growth plate which ultimately predispose it to slippage.7

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

Classification

SCFE can be classified according to stability, severity, symptom duration by using the following classification systems8

Stability
Loder Classification: classifies cases as stable or unstable based on ability to bear weight. This type of classification is predictive of prognosis and accounts for nearly 90% of all SCFE cases.9

  • Stable:  able to bear weight on the affected side with or without crutches.
  • Unstable: unable to bear weight even with the use of crutches as symptoms are more severe. May have up to a 50% incidence of hip osteonecrosis compared with nearly <10% in stable SCFE.

Severity
Southwick Slip Angle Classification: radiologic classification using a frog leg lateral hip radiograph based on the femoral epiphyseal-diaphyseal angle between the affected and unaffected hip. Difference from the opposite side is used to grade the severity of the slip.9

  • Mild: < 30°
  • Moderate:  30-50°
  • Severe: > 50°

Figure 1: Southwick head-shaft angle on a frog leg lateral view.10

  • In cases of bilateral SCFE, 145° for AP radiographs and 10° frog lateral radiographs is used as “unaffected” hip reference.
  • Severity is known to be linked with femoroacetabular impingement.

Grading System: radiographic classification based on the percentage of epiphyseal displacement.8

  • Grade I (mild): 0-33° displacement
  • Grade II (moderate):  33-50° displacement
  • Grade III (severe): >50° displacement

Figure 2: Grading of SCFE determined by the percentage of displacement based on radiographic findings.10

Duration
Temporal Classification: traditional classification based on the duration of symptoms. Rarely used as it does not yield prognostic information.5

  • Acute: symptoms present for ≤ 3 weeks
  • Chronic: symptoms present for ≥ 3 weeks; most common
  • Acute on Chronic: acute exacerbation with prior chronic SCFE

Specific secondary or associated conditions and complications

Secondary conditions and complications11

1. Femoral head osteonecrosis or loss of vascular flow occurs at a higher rate in severe, unstable SCFE and is associated with worse prognosis. Generally, the epiphysis is left in its position since the risk of avascular necrosis is high if manipulation is attempted.  It is a detrimental complication resulting in decreased hip motion, increased pain, and lower functional outcomes and activity scores.

2. Chondrolysisis a rapidly progressive loss of articular cartilage that is most commonly seen after pin penetration into the hip joint. Symptoms include decreased range of motion, hip pain, stiffness, and joint space reduction of >50% in the affected hip.

3. Femoroacetabular impingement, a condition that appears mostly in adolescence and in young adults, is associated with decreased anterior head-neck offset in the proximal femur and acetabular overcoverage.12 It is commonly seen in patients with SCFE, particularly CAM type lesions, characterized by bony overgrowth of the femur neck.

4. Premature osteoarthritis of the hip is a common long-term complication of SCFE that may arise in mild cases without slip severity correlation.

5. Growth arrest can result in leg-length discrepancies and altered gait patterns, especially in pubertal patients undergoing a growth spurt.

*To prevent delay in diagnosis of a second slip in children who do not undergo prophylactic pinning, patients with unilateral involvement, specifically those with endocrinopathies, should be followed closely by an orthopedic surgeon*

Essentials of Assessment

History

The typical presentation is an obese pre-adolescent with dull, poorly localized hip, groin, thigh, or knee pain, usually worsened with physical activity.  The hip (52%) is the most commonly reported area; however, thigh/leg (35%), knee (26%) or groin (14%) pain may also be present.13 Most patients will deny preceding trauma before symptom onset, nonetheless, presence of prior injury does not exclude the likelihood of SCFE.  SCFE can be classified clinically based on symptom intensity and duration into the following categories.6

Acute: symptoms present for < 3 weeks
Chronic: symptoms present for >3 weeks (most common; seen in 85% of cases)
Acute on chronic: acute exacerbation with prior chronic SCFE

Differential diagnosis in young patients with hip or knee pain is broad, including infectious, inflammatory, or rheumatologic causes, thus it is imperative to perform a detailed medical history and physical examination. Clinicians should have SCFE at the top of their differential diagnosis in any patient with impaired gait and inability to bear weight, recent growth spurt, pain with physical activity or any predisposing factors such as obesity or systemic disease. Patients whose initial symptoms comprise knee or thigh pain without the classic hip pain, have a greater chance of having their diagnosis missed leading to a delay in treatment and a worse prognosis.

Additional differential diagnosis in adolescents and young adults with hip pain1

  • Femoral fracture
  • Avascular necrosis of the femoral head
  • Legg-Calve-Perthes Disease
  • Osteomyelitis
  • Septic Arthritis
  • Transient synovitis
  • Adductor Muscle Strain
  • Avulsion fracture of the anterior iliac spine
  • Apophysitis of the anterior iliac spine

Physical examination

Physical examination must include a detailed evaluation of the hip. Observation for increased weight/BMI for possible hip or knee swelling. Palpation of femur looking for point tenderness or warmth should be assessed. Affected versus unaffected hip range of motion and standing posture should be assessed. Internal rotation of the symptomatic hip is usually limited due to pain and may be accompanied by a loss of ipsilateral hip flexion and abduction depending on the severity of the slip. A positive Drehman sign, characterized by obligatory external rotation and abduction of the hip during passive hip flexion to 90 degrees, is highly indicative of SCFE. In addition, abnormal gait patterns may present with antalgic, Trendelenburg or waddling gait with inability to bear weight on the affected extremity.1If any evidence of endocrine abnormalities (i.e.: small stature) further workup should be performed.

Clinical functional assessment: mobility, self-care cognition/behavior/affective state

SCFE may affect a child’s overall function, including mobility, standing and functional ambulation due to pain and range of motion restrictions.

Laboratory studies

Laboratory tests are used to evaluate other potential etiologies in patients with atypical presentations that include symptom onset before age 8 or after age 15, low weight (< 50th percentile), and short stature. Patients with underlying endocrine and renal disease may present with these unusual findings warranting further workup.

Initial laboratory tests include13

  • Thyroid stimulating hormone
  • Free T4 levels
  • Parathyroid hormone
  • Vitamin D levels
  • Adrenocorticotropic hormone
  • Blood urea nitrogen
  • Serum creatinine

Referral to appropriate subspecialists should be considered if abnormalities are found in any of the above laboratory tests.

Imaging

Hip radiographs are the preferred diagnostic screening tool for SCFE.  X-rays should include anteroposterior, frog-leg lateral (suspected stable SCFE) and cross-table lateral (suspected unstable SCFE) views of both hips. Radiography is used to classify and grade the severity of the slip, typically showing growth plate widening and degeneration of the proximal epiphysis.1 On radiographic imaging, SCFE is often described as being like a scoop of ice cream (femoral head) slipping off a cone (femoral neck).

A characteristic finding known as Trethowan’s sign, may be seen on AP hip radiographs where a line (Klein’s line) is drawn parallel to the superior femoral neck. In a healthy hip, Klein’s line intersects a small portion of the lateral epiphysis. In posterior displacement of the epiphysis, Klein’s line lies lateral to and does not intersect the epiphysis, yielding a positive Trethowan’s sign.10

Figure 3: Left hip showing Klein’s line that does not intersect the epiphysis, a finding known as Trethowan’s sign.

Supplemental assessment tools

Magnetic resonance imaging (MRI) and other imaging studies such as computed tomography, bone scan, and ultrasonography, can be helpful when there is high clinical suspicion in the absence of radiographic abnormalities and for evaluation of associated conditions or potential complications in patients with a confirmed diagnosis of SCFE.1

Early predictions of outcomes

Worse prognosis exists with higher severity of the slip as these cases are at increased risk for developing treatment complications such as premature osteoarthritis, femoroacetabular impingement, osteonecrosis and chondrolysis.

Environmental

Geographical and environmental factors may have a significant effect on the long-term outcomes of SCFE. In urban areas, for example, it is more likely to find physicians who specialize in this patient population in contrast to rural areas. Limited access to subspecialty care may lead to delay in diagnosis and treatment which is known to be associated with worse prognosis.

Social role and social support system

SCFE and its complications may lead to lifelong disability encompassing pain, gait disturbances, degenerative changes, osteonecrosis and chondrolysis. Recognizing this impairment and its impact on a patient’s function is important, as careful monitoring, adequate management and resource stratification may improve the patient’s quality of life.

Professional Issues

If undiagnosed or left untreated, SCFE may result in chronic pain which can subsequently interfere with quality of personal, social and professional life. As stated previously, untreated SCFE may lead to avascular necrosis of the hip for which prompt identification and referral to orthopedics is critical.

Rehabilitation Management and Treatments

Available or current treatment guidelines

The mainstay of treatment includes activity and lifestyle modifications, adequate pain management, and surgical interventions with postoperative rehabilitation protocols.

Surgical

The mainstay of treatment for SCFE is in situ pinning, although osteotomies, open reduction, and capsular decompression have been described, particularly for severe, unstable slips.1 The goal of treatment is to arrest progression of the slip and attain capital femoral epiphysis closure.3 Commonly, the epiphysis is left in its displaced position because the risk of AVN is high if manipulation is attempted. After successful physeal closure, the proximal femur can remodel. In stable SCFE, standard treatment is in situ fixation with a single screw. On the contrary, in unstable SCFE, the Modified Dunn procedure, a surgical hip dislocation that helps restore proximal femur alignment to decrease rate of femoroacetabular impingement, is recommended.

Rehabilitation

Following surgery, patients are made non-weight bearing on the affected extremity for 6-12 weeks with the aid of crutches or walkers to keep stress of the hip joint, the repair, and femoral head surface.3 Physical therapy with a range of motion exercises and strengthening to restore lengthening, adduction and internal rotation of the hip should start as early as the first postoperative day. Management of acute symptoms, restoring normal arthrokinematics, strength, neuromuscular and functional training are the principal objectives of the rehabilitation program. The following five-phase postoperative rehabilitation protocol is recommended to maximize postsurgical functional capacity.1

Phase 1 – emphasis on managing pain and reducing joint and soft tissue inflammation in order to restore normal range of motion. Ambulatory assistive devices such as crutches or walkers are implemented early in the rehabilitation program to avoid weight bearing of the affected hip.3
Phase 2 – focus is to achieve normal pain free unassisted ambulation as well as painless straight leg raise abduction.
Phase 3 & 4 – involve strength and cardiovascular endurance training.
Phase 5 – comprises restoring coordination, balance, agility, and functional movement patterns.

At different disease stages

  • After surgical intervention
    • limited weightbearing with crutches or walker for at least 6 weeks. In bilateral surgeries, patients are taught to use four-point gait
    • includes rehabilitation strategies that intend to stabilize or optimize function or prepare for further interventions at later disease stages
  • Secondary prevention and disease management strategies
    • includes symptom relief
    • after 6-8 weeks crutches are discontinued and regular activities gradually resume.
  • Chronic/stable
    • includes secondary prevention and disease management strategies
    • includes palliative strategies and symptom relief
    • return to sports participation depends upon the residual limitation of motion.
    • it is estimated that 45% of SCFE patients will undergo a total hip arthroplasty within 50 years of the initial insult.
  • Pre-terminal or end of life care
    • Palliative care and optimize quality of life

Coordination of care

Optimal communication within the multidisciplinary team consisting of pediatricians, physiatrists, orthopedic surgeons, and physical and occupational therapists is of utmost importance in order to provide adequate patient care. Early intervention during the disease course correlates with better prognosis. Close follow up focusing on symptom control, hip mobility and preventing complications should be emphasized at all disease stages.

Patient & family education

Education regarding the condition and instructions on strict non-weight bearing precautions in addition to the importance of optimal pain management is essential. Patients and their families should seek pediatric orthopedic evaluation in order to assess if urgent surgical management is required.

As primary care providers, it is imperative to provide extensive education about weight control and involve specialists in nutrition and obesity early in the postoperative course if needed.14

Measurement of Treatment Outcomes including those that are impairment-based, activity participation-based and environmentally based.

The Hip Disability and Osteoarthritis Outcome Score (HOOS), the Non-Arthritic Hip Score (NAHS), the Copenhagen Hip and Groin Outcome Score (HAGOS), have been validated in young adults to monitor and describe hip function rather than arthritic changes and need for hip replacement.15

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

Physicians should have SCFE within the differential diagnosis of any pre-adolescent or adolescent patient presenting with hip or knee pain. Strict non-weight bearing precautions, pain management and orthopedic surgery consultation early during the disease course is essential for improved outcomes. Delay in the diagnosis of SCFE and substandard patient care can lead to increased disability and warrant more aggressive management over time.1

Cutting Edge/Emerging and Unique Concepts and Practice

In a recent study (2018), a new radiographic parameter on frog-leg lateral views referred to as S-sign, can be used for the diagnosis of SCFE. S-sign alone has a sensitivity of 89.0% and specificity of 95.2%. Trethowans sign alone yields a sensitivity of 68.3% and a specificity of 89.0%. Evaluation using a combination of both the S-sign and Trethowans sign, results in an overall sensitivity of 96.5%. Employing these two parameters concomitantly can aid in faster diagnosis and earlier orthopedic surgery management as well as a lower rate of delayed or missed diagnosis.17

Gaps in the Evidence-Based Knowledge

Further validation of outcome measure scales and studies focusing on short and long term outcomes may aid in determining the role of different surgical approaches and strategies aimed at preserving the hip joint and decreasing risks of arthritic changes.3

Reports indicate the risk of contralateral hip slippage in patients who first present with unilateral SCFE can be 2335 times higher than the risk of an initial displacement. Some reports in the medical literature dictate the overall prevalence rates of bilateral hip slippage to be as high as 80%. Prophylactic pinning of the contralateral hip in unilateral SCFE continues to be an area of ongoing discussion, nonetheless, some physicians opt to recommend surgical prophylaxis due to the previously mentioned findings.18

The use of growing implants has been proposed to help remodel mild hip deformities and prevent secondary trochanteric overgrowth. Although not readily available everywhere, these implants seem to be non-inferior to the standard in-situ pinning which stops growth and involves premature physeal closure.19

References

  1. Peck, D. M., Voss, L. M., & Voss, T. T. (2017). Slipped capital femoral epiphysis: Diagnosis and management. American Family Physician, 95(12), 779–784.
  2. Slipped Capital Femoral Epiphysis. Boston Children’s Hospital, 2020, https://www.childrenshospital.org/conditions-and-treatments/conditions/s/slipped-capital-femoral-epiphysis. Accessed 19 Dec. 2021.
  3. Sarwark, John F., and Cynthia R. LaBella. “Ch 20: Slipped Capital Femoral Epiphysis.” Pediatric Orthopaedics and Sports Injuries: A Quick Reference Guide, 3rd ed., American Academy of Pediatrics, Elk Grove Village, 2021.
  4. Novais, E. N., & Millis, M. B. (2012). Slipped capital femoral epiphysis: prevalence, pathogenesis, and natural history. Clinical orthopaedics and related research, 470(12), 3432–3438. https://doi.org/10.1007/s11999-012-2452-y.
  5. Georgiadis, A. G., & Zaltz, I. (2014). Slipped capital femoral epiphysis: how to evaluate with a review and update of treatment. Pediatric clinics of North America, 61(6), 1119–1135. https://doi.org/10.1016/j.pcl.2014.08.001.
  6. Diab M, Staheli LT. Practice of Pediatric Orthopedics, 3rd ed. Philadelphia, PA: Wolters Kluwer, 2016
  7. Witbreuk, M., van Kemenade, F. J., van der Sluijs, J. A., Jansma, E. P., Rotteveel, J., & van Royen, B. J. (2013). Slipped capital femoral epiphysis and its association with endocrine, metabolic and chronic diseases: a systematic review of the literature. Journal of children’s orthopaedics, 7(3), 213–223. https://doi.org/10.1007/s11832-013-0493-8
  8. Johns K, Mabrouk A, Tavarez MM. Slipped Capital Femoral Epiphysis. [Updated 2021 Aug 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538302/
  9. Aronsson DD, Loder RT, Breur GJ, Weinstein SL. Slipped capital femoral epiphysis: current concepts. J Am Acad Orthop Surg. 2006;14(12):666-679. doi:10.5435/00124635-200611000-00010
  10. Lasanianos, N. G. (2016). Trauma and orthopaedic classifications. Springer London Ltd.
  11. Roaten, J., & Spence, D. D. (2016). Complications related to the treatment of slipped capital femoral epiphysis. The Orthopedic Clinics of North America, 47(2), 405–413.
  12. Martus JE. Orthopedic Knowledge Update Pediatrics 5. Rosemont, IL: American Academy of Orthopedic Surgeons; 2016
  13. Uvodich, M., Schwend, R., Stevanovic, O., Wurster, W., Leamon, J., & Hermanson, A. (2019). Patterns of Pain in Adolescents with Slipped Capital Femoral Epiphysis. The Journal of pediatrics, 206, 184–189.e1. https://doi.org/10.1016/j.jpeds.2018.10.050
  14. Wells D, King JD, Roe TF, Kaufman FR. Review of slipped capital femoral epiphysis associated with endocrine disease. J Pediatr Orthop. 1993 Sep-Oct;13(5):610-4.
  15. Castillo C, Mendez M. Slipped Capital Femoral Epiphysis: A Review for Pediatricians. Pediatr Ann. 2018 Sep 1;47(9):e377-e380. doi: 10.3928/19382359-20180730-01. PMID: 30208198.
  16. Bond, E. C., Phillips, P., Larsen, P. D., Hunt, L., & Willoughby, R. (2019). Long-term hip function in slipped capital femoral epiphysis treated with in situ pinning. Journal of orthopaedic surgery (Hong Kong), 27(1), 2309499018822234. https://doi.org/10.1177/2309499018822234
  17. Rebich EJ, Lee SS, Schlechter JA. The S Sign: A New Radiographic Tool to Aid in the Diagnosis of Slipped Capital Femoral Epiphysis. J Emerg Med. 2018;54(6):835-843. doi:10.1016/j.jemermed.2018.01.023
  18. Schultz WR, Weinstein JN, Weinstein SL, Smith BG. Prophylactic pinning of the contralateral hip in slipped capital femoral epiphysis : evaluation of long-term outcome for the contralateral hip with use of decision analysis. J Bone Joint Surg Am. 2002 Aug;84(8):1305-14. doi: 10.2106/00004623-200208000-00003. PMID: 12177258.
  19. Leblanc, E., Bellemore, J. M., Cheng, T., Little, D. G., & Birke, O. (2017). Biomechanical considerations in slipped capital femoral epiphysis and insights into prophylactic fixation. Journal of Childrens Orthopaedics, 11(2), 120-127. doi:10.1302/1863-2548-11-170012

Author Disclosure

Edwardo Ramos, MD
Nothing to Disclose

Daniel Almodovar-Frau, MD
Nothing to Disclose

Ana Ortiz-Santiago, MD
Nothing to Disclose