Slipped capital femoral epiphysis (SCFE) is a hip disorder that involves failure of the physis and displacement of the femoral head relative to the neck. Pediatricians must have a high index of suspicion because a delayed diagnosis results in poor outcomes.1
The incidence of SCFE among children in the United States in 2011 was 0.33 to 24.58 per 100,000.2 The incidence since then has almost tripled according to a recent study done in New Mexico,3 and a similar trend has been found in several European countries, including Scotland in the United Kingdom.2 The exact cause of this increase is still unknown but may be associated with a parallel rise in the prevalence of overweight and obesity in adolescents,4 as obesity is the most significant risk factor for SCFE.5
SCFE occurs most commonly among black and Hispanic children, with a relative incidence of 3.94 and 2.53 times higher, respectively, compared to white children.2 The male-to-female ratio is 1.6:1, and it usually presents near the time of peak linear growth, usually between ages 10 and 16 years, with an average age of 12 years in girls and 13.5 years in boys.6 SCFE can be bilateral in 20% to 80% of cases, and most cases of SCFE on the contralateral hip occur during the first year after the first slip.7
Etiology and Pathogenesis
SCFE is a hip disorder characterized by a displacement of the femoral head through the physis.2 Certain morphologic changes of the proximal femur are associated with SCFE, such as reduced femoral anteversion and absolute femoral retroversion.7 Although most of the cases are idiopathic, risk factors to develop SCFE include renal disease, hypothyroidism, and growth hormone deficiency.8,9
Traditionally, SCFE was classified as acute, chronic, and acute-on-chronic based on radiographic and clinical parameters. An acute case of SCFE usually presents with symptoms less than 3 weeks in duration with an abrupt displacement of the femoral head. However, the most common type of presentation is chronic SCFE, in which symptoms persist for 3 weeks or longer. Acute-on-chronic refers to the worsening of hip pain in the setting of longstanding symptoms.
A newer classification determines prognosis based on stability and is currently the most commonly used classification. Hips are classified as either stable or unstable.10 A patient with a stable SCFE can bear weight on the affected side with or without crutches. A patient with an unstable SCFE cannot bear weight even with crutches due to severe pain.
Radiographic changes also identify the severity of SCFE. One radiographic classification is based on the degree of epiphyseal displacement when compared to the total physeal diameter. Using this fraction, SCFE can be classified as mild (<33%), moderate (33%–50%), or severe (>50%).10 The Southwick grading can also be used, although the femoral rotation can be inconsistent depending on the radiographic technique. In this system, the epiphyseal-shaft angle, subtended by the femoral shaft and the proximal femoral physis, is compared between both hips.10
Pain and limping in any child or adolescent is always a red flag, and the differential diagnosis should include infectious, inflammatory, or rheumatologic causes and trauma. SCFE should be suspected, especially when the patient is overweight or obese. The pain is usually dull, located in the groin, thigh, or knee, not preceded by any trauma, and can get worse with physical activity. Several questions should be asked to rule out other comorbid conditions (eg, hypothyroidism, panhypopituitarism). Examination findings are dependent on degree of slip present. Initial presentation may be remarkable for minimal loss of internal rotation of hip and pain exacerbated by extremes in range of motion. As the slip progresses in severity, range of motion gradually decreases with loss of internal rotation, associated abduction, and flexion of hip increase. One may notice that the patient will sit on the examination table with the affected hip externally rotated. Gait becomes progressively more antalgic with exaggeration of the Trendelenburg gait with associated muscle atrophy, and eventually leg-length discrepancies will become more apparent without correction. The examination of the knee is usually normal, although pain may be elicited during active or passive movement of the affected hip.
SCFE is often misdiagnosed by pediatricians, especially when the symptoms are mild and not specific, which is usually the case in patients with a stable SCFE. A study in Denmark reported that the diagnosis was delayed in 67% of patients, especially when the patients were initially seen by primary care providers and residents.11 In a study from the US, diagnosis was made by a non-orthopedic provider in 19% of the patients during the first week of the disease. Patients who present with knee pain instead of hip pain are at higher risk of having a delayed diagnosis.12
The current standard diagnostic tool is a bilateral hip radiograph, as most cases of SCFE are detected with plain radiographs of the hips. Radiographic views should be dependent on classification of SCFE, as positioning of the patient for the “frog leg” view may aggravate the displacement.6 If stable SCFE is suspected, anteroposterior and frog leg lateral views should be performed; however, if there is suspicion of unstable SCFE then anteroposterior and cross-table lateral views are indicated. Imaging should always be bilateral to allow for the comparison of the uninvolved side with affected side and to help identify asymptomatic slips.
Depending on the severity of slip, one can identify various changes on radiographic imaging. In the early or “pre-slip” phase, there is growth plate widening or lucency and obscuring of physeal edges. During the acute slip phase, frog leg lateral views are particularly useful in identifying minimal posterior slippage. On anteroposterior view, Klein's line (a line drawn along the superior border of the femoral neck) may be used to identify a possible SCFE if this line fails to intersect the lateral part of the femoral head (Figure 1). Magnetic resonance imaging (MRI) of the hip can be essential in early stages when X-rays are negative but there is strong clinical suspicion. MRI can also reveal the presence of avascular necrosis postoperatively, especially in high-risk patients.13 Computed tomography and ultrasound of the hip have little role in the routine evaluation of patients with SCFE. All patients younger than age 10 years with thin body habitus or presenting with systemic symptoms should have appropriate laboratory tests to rule out renal and endocrine disorders.
Anteroposterior radiographic image of slipped capital femoral epiphysis. (A) Klein's line identifies failure to intersect with femoral head. (B) Appearance of early slip with Klein's line barely touching femoral head, also called a positive Trethowan's sign.
Immediate referral to an orthopedic surgeon is a warranted once a diagnosis is made. The patient should not bear any weight and should use a wheelchair or crutches. Surgery is required to stabilize the epiphysis and prevent slip progression and long-term sequelae. In situ screw fixation is the most common treatment regardless of the severity.14 Prophylactic pinning of a normal contralateral hip can be considered in certain cases such as patients with an atypical SCFE, or in those patients with obesity in whom the surgeon suspects a delay would result in the presentation of a contralateral SCFE.10
Physical therapy should be provided soon after surgery. Gentle range-of-motion exercises may be started as early as the day after surgery. Recovery and weight-bearing strategies vary depending on the degree of the slip. If a stable slip was present, patients usually use crutches for approximately 2 to 3 weeks until motion is painless. For unstable slip repair, patients should not fully bear weight without crutches for at least 6 to 8 weeks.15,16 A study from 2013 revealed that patients with obesity have a greater chance of developing a contralateral SCFE.17 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.
Complications and Outcome
Despite the fact that the goal of treatment is to prevent and minimize complications, the overall rate of complications is still high. Avascular necrosis is more common in the patient with an unstable hip and can be a complication present in about 20% of cases.18,19 Less commonly, chondrolysis can be seen in 7% of patients and should be suspected when there is motion restriction, which is associated with a joint space reduction on a radiograph.20 Another complication with clinical relevance for pediatricians is growth arrest. The average age of most patients at the time of presentation is 12 years, and after surgery the expectation is that 3 mm per year of limb growth from the proximal femoral physis will be lost.20
SCFE is a common hip disorder seen during adolescence, especially in patients who are obese. The most common symptom is hip pain, although patients can also present with isolated knee or thigh pain. Prompt referral to a specialist is imperative in equivocal cases to avoid a delayed diagnosis. The treatment is always surgical and should be done promptly to prevent progression of the slip. Obesity should be addressed aggressively after surgery to avoid involvement of the contralateral hip.
- Kocher MS, Bishop JA, Weed B, et al. Delay in diagnosis of slipped capital femoral epiphysis. Pediatrics. 2004;113:e322–e325. doi:10.1542/peds.113.4.e322 [CrossRef]
- Loder RT, Skopelja EN. The epidemiology and demographics of slipped capital femoral epiphysis. ISRN Orthop. 2011;2011:486512. doi:. doi:10.5402/2011/486512 [CrossRef]
- Benson EC, Miller M, Bosch P, Szalay EA. A new look at the incidence of slipped capital femoral epiphysis in New Mexico. J Pediatr Orthop. 2008;28(5):529–533. doi:. doi:10.1097/BPO.0b013e31817e240d [CrossRef]
- Murray AW, Wilson NI. Changing incidence of slipped capital femoral epiphysis: a relationship with obesity?J Bone Joint Surg Br. 2008;90:92–94. doi:. doi:10.1302/0301-620X.90B1.19502 [CrossRef]
- Manoff EM, Banffy MB, Winell JJ. Relationship between body mass index and slipped capital femoral epiphysis. J Pediatr Orthop. 2005;25:744–746. doi:10.1097/01.bpo.0000184651.34475.8e [CrossRef]
- Novais EN, Millis MB. Slipped capital femoral epiphysis: prevalence, pathogenesis, and natural history. Clin Orthop Relat Res. 2012;470:3432–3438. doi:. doi:10.1007/s11999-012-2452-y [CrossRef]
- Lehmann CL, Arons RR, Loder RT, Vitale MG. The epidemiology of slipped capital femoral epiphysis: an update. J Pediatr Orthop.2006;26(3):286–290. doi:. doi:10.1097/01.bpo.0000217718.10728.70 [CrossRef]
- Burrow SR, Alman B, Wright JG. Short stature as a screening test for endocrinopathy in slipped capital femoral epiphysis. J Bone Joint Surg Br. 2001;83(2):263–268. doi:10.1302/0301-620X.83B2.10554 [CrossRef]
- Weiner D. Pathogenesis of slipped capital femoral epiphysis: current concepts. J Pediatr Orthop B. 1996;5(2):67–73. doi:10.1097/01202412-199605020-00002 [CrossRef]
- Georgiadis AG, Zaltz I. Slipped capital femoral epiphysis: how to evaluate with a review and update of treatment. Pediatr Clin North Am. 2014;61(6):1119–1135. doi:. doi:10.1016/j.pcl.2014.08.001 [CrossRef]
- Pihl M, Sonne-Holm S, Christoffersen JK, Wong C. Doctor's delay in diagnosis of slipped capital femoral epiphysis. Dan Med J. 2014;61(9):A4905.
- Hosseinzadeh P, Iwinski HJ, Salava J, Oeffinger D. Delay in the diagnosis of stable slipped capital femoral epiphysis. J Pediatr Orthop. 2017;37(1):e19–e22. doi:. doi:10.1097/BPO.0000000000000665 [CrossRef]
- Restrepo R, Reed MH. Impact of obesity in the diagnosis of SCFE and knee problems in obese children. Pediatr Radiol. 2009;39(suppl 2):S220–S225. doi:. doi:10.1007/s00247-008-1123-3 [CrossRef]
- Loder RT, Dietz FR. What is the best evidence for the treatment of slipped capital femoral epiphysis?J Pediatr Orthop. 2012;32(suppl 2):S158–S165. doi:. doi:10.1097/BPO.0b013e318259f2d1 [CrossRef]
- Hansen PA, Henrie AM, Deimel GW, Willick SE. Musculoskeletal disorders of the lower limb. In: Cifu D, ed. Braddom's Physical Medicine and Rehabilitation. 5th ed. Philadelphia, PA: Saunders Elsevier; 2016:795.
- Sawyer J, Spence D. Fractures and dislocations in children. In: Azar F, Beaty J, Canale T, eds. Campbell's Operative Orthopaedics. 13th ed. Philadelphia, PA: Saunders Elsevier; 2017:1423–1569.
- Nasreddine AY, Heyworth BE, Zurakowski D, Kocher MS. A reduction in body mass index lowers risk for bilateral slipped capital femoral epiphysis. Clin Orthop Relat Res. 2013;471(7):2137–2144. doi:. doi:10.1007/s11999-013-2811-3 [CrossRef]
- Loder RT. What is the cause of avascular necrosis in unstable slipped capital femoral epiphysis and what can be done to lower the rate?J Pediatr Orthop. 2013;33(suppl 1):S88–S91. doi:. doi:10.1097/BPO.0b013e318277172e [CrossRef]
- Zaltz I, Baca G, Clohisy JC. Unstable SCFE: review of treatment modalities and prevalence of osteonecrosis. Clin Orthop Relat Res. 2013;471:2192–2198. doi:. doi:10.1007/s11999-012-2765-x [CrossRef]
- Roaten J, Spence DD. Complications related to the treatment of slipped capital femoral epiphysis. Orthop Clin North Am. 2016;47(2):405–413. doi:. doi:10.1016/j.ocl.2015.09.013 [CrossRef]