Evaluation and management of slipped capital femoral epiphysis (SCFE)

INTRODUCTION — This topic will cover the evaluation and management of slipped capital femoral epiphysis (SCFE). Other causes of hip pain, knee pain, and limp in children and their diagnosis are discussed in greater detail separately:

●(See "Evaluation of limp in children" and "Overview of the causes of limp in children".)

●(See "Approach to chronic knee pain or injury in children or skeletally immature adolescents".)

●(See "Approach to hip pain in childhood".)

DEFINITION — SCFE, also called slipped upper femoral epiphysis (SUFE) and physiolysis of the hip, is characterized by a displacement of the capital femoral epiphysis from the femoral neck through the physeal plate. It is one of the most common hip disorders of adolescence. Hip pain is a common presenting feature. However, approximately 15 percent of patients present with isolated thigh or knee pain. Thus, physicians must have a high degree of suspicion to prevent delay in diagnosis, which can worsen prognosis [1].

EPIDEMIOLOGY — SCFE occurs in approximately 1 per 1000 to 1 per 10,000 children and young adolescents [2,3]. The epidemiology of SCFE was defined in a multinational study of more than 1600 children and a nationwide cohort study in the United Kingdom [3,4]. The typical patient is a child with obesity without any other underlying risk factors who, if female, has not yet reached menarche, and if male, has not yet reached the fourth Tanner stage. The mean age of presentation is 12 years in girls and 13.5 years in boys, near the time of peak linear growth [3]. The male-to-female ratio is approximately 1.5:1. (See "Normal puberty".)

SCFE is bilateral in 20 to 40 percent of cases at presentation [3,5]. In children who present with unilateral disease, the contralateral hip slips at a later time in an additional 30 to 60 percent, and in up to 100 percent of patients with underlying endocrine disorders [6-8]. In unilateral slips, the left hip is affected somewhat more often than the right, for unknown reasons [4].

Obesity is a significant risk factor in the development of idiopathic SCFE. In the multinational study described above, more than 60 percent of patients measured greater than or equal to the 90^th percentile weight for age and sex [4]. Furthermore, the risk of SCFE has been shown to increase with the severity of obesity in an individual child [9]. In addition, the increased prevalence of adolescent obesity has been associated with a marked increase in the frequency of SCFE in selected regional and national populations [9-11]. (See "Overview of the health consequences of obesity in children and adolescents".)

Additional risk factors include renal failure [12], history of radiation therapy [13], endocrine abnormalities (particularly hypothyroidism and growth hormone deficiency) [14-16], and various genetic disorders (eg, Down and Rubenstein-Taybi syndromes) [17,18]. When SCFE occurs in association with one of these additional risk factors, it is called atypical SCFE [19]. Children presenting with SCFE who are younger than 10 years, older than 16 years, whose weight is <50^th percentile for age, or whose height is <10^th percentile for age should be considered atypical and are likely to have one of the conditions mentioned above [14,19,20].

ETIOLOGY — The term SCFE is a misnomer. It is actually the portion of the proximal femur distal to the physis (growth plate) that is displaced anterolaterally and superiorly [21]. This displacement gives the appearance of posterior and inferior displacement of the epiphysis, which in fact remains in normal position in the acetabulum.

In rare cases, usually in tall, thin adolescents, the femoral neck is displaced downward and anteriorly in relation to the femoral head. In contrast to the typical varus angulation, the femoral head-neck shaft angle in these cases is widened (valgus angulation or coxa valga) [22].

SCFE occurs when shearing forces applied to the femoral head exceed the strength of the capital femoral physis [23]. The factors that weaken the physeal plate are not fully clarified but are thought to include [24]:

●Normal periosteal thinning and widening of the physis, which occurs during physiologic hormonal changes associated with adolescence and other periods of rapid growth acceleration [25-27]

●Trauma (particularly in acute and acute-on-chronic slips)

●Obesity, which increases mechanical strain on the physis

●Inflammatory changes

●Genetic predisposition [28-31]

●Endocrine and metabolic disorders (eg, hypothyroidism and growth hormone deficiency, which can cause abnormal growth and mineralization of cartilage) [32,33]

●Total body irradiation used in pediatric cancer patients [34]

CLINICAL MANIFESTATIONS — The two most common features of the presentation of SCFE are pain and altered gait [23]. The classic presentation is that of an adolescent with obesity with a complaint of nonradiating, dull, aching pain in the hip, groin, thigh, or knee, and no history of preceding trauma. The pain is increased by physical activity and may be acute, chronic, or intermittent. Patients with acute or acute on chronic pain with significant pain, loss of motion in the affected hip, and/or difficulty ambulating should be made nonweightbearing while establishing the diagnosis and remain nonweightbearing until definitive treatment. (See 'Acute' below and 'Acute-on-chronic' below.)

In patients with chronic or intermittent pain, the absence of pain, or pain localized to the knee or thigh instead of the hip, can lead physicians to overlook the diagnosis. Physical examination may demonstrate hip pain on palpation and limitation of hip range of motion, especially internal rotation and flexion. (See 'Chronic' below.)

CLASSIFICATION — SCFE may be classified according to its pattern of presentation, stability, or severity.

Pattern of presentation — SCFE is traditionally classified into four patterns of presentation on the basis of intensity and duration of symptoms [35]:

●Preslip

●Acute

●Acute-on-chronic

●Chronic

Preslip — Children with preslip SCFE have pain but no discernible displacement of the epiphysis [23]. Radiographs demonstrate widening of the proximal femoral physis compared with the opposite asymptomatic hip.

Acute — Children with acute SCFE have symptoms of less than three weeks' duration. Joint effusion is present, but there is no metaphyseal remodeling [36]. Acute presentation occurs in 10 to 15 percent of patients with SCFE, and often is associated with trauma [4,37,38]. Acute traumatic slips may occur following major trauma (eg, fall from height or motor vehicle accident).

Symptoms include onset of severe pain, external rotational deformity, limited range of motion of the hip, shortening, and commonly, inability to bear weight [38]. Active motion of the hip is severely limited by muscle spasm, and the patient complains of intense pain with any attempt at passive motion.

Patients with acute symptoms of SCFE are at risk of further displacement of the epiphysis. To avoid this and for pain relief, patients with an acute slip should immediately be placed on crutches, in a wheelchair or on a stretcher and remain non-weightbearing until they have received definitive treatment. (See 'Stability' below and 'Management' below.)

Acute-on-chronic — The acute-on-chronic presentation occurs when a patient with a history of symptoms and signs of chronic SCFE (eg, limp and or pain of at least three weeks’ duration) presents with an acute increase in pain and loss of motion of the affected hip [35]. Joint effusion and metaphyseal remodeling are present [39]. Patient should be made nonweightbearing as for children with acute SCFE.

Chronic — Chronic SCFE is the most common pattern of presentation. It is characterized by vague, intermittent symptoms over a protracted period, usually considered to be longer than three weeks. Metaphyseal remodeling is present, but there is no effusion [36].

The classic presentation is that of an adolescent with obesity and a complaint of nonradiating, dull, aching pain in the hip, groin, thigh, or knee and no history of preceding trauma [40]. Approximately 60 percent of patients present with hip pain [40]. By contrast, isolated thigh or knee pain occurs in a minority of patients [41]. SCFE is more likely to be missed at the initial visit in patients with knee or thigh pain but no complaint of hip pain [1,40-43]; physicians must have a high degree of suspicion to prevent delay in diagnosis and a potentially worse prognosis [1].

The pain may be chronic or intermittent; it is increased by physical activity and relieved with rest (although this may take up to an hour to achieve) [44]. Patients usually have already limited their participation in strenuous or sporting activities because of discomfort.

Patients with idiopathic SCFE usually have obesity. However, they may be tall and thin, indicating a rapid growth spurt [22]. The patient usually has an altered gait. The foot on the affected side is usually turned out more than its mate. If the SCFE is unilateral, the gait may be antalgic: the patient takes a short step on the affected side to minimize weightbearing, which is painful, during the stance phase [22]. In moderate or severe unilateral slips, there may be a Trendelenburg gait: a shift of the torso over the affected hip (picture 1). The affected leg is usually held in an externally rotated position and may be shorter than the unaffected leg. If the SCFE is bilateral, the gait is usually waddling.

Disuse atrophy of the upper thigh and gluteal muscle may be present in moderate or severe slips but may be difficult to appreciate in a patient with obesity.

The anterior hip may be tender to palpation. In contrast, despite a complaint of pain in the knee area, localized tenderness to palpation of this area is not present. The remainder of the knee examination is normal as well.

Range of motion of the hip demonstrates decreased internal rotation, abduction, and flexion but may be painful in all directions. The degree of restriction of range of motion depends upon the severity of the slip. Although the range of motion for adduction is usually normal, it should be tested in all patients to detect the rare patient with a valgus slip (ie, coxa valga, discussed below) [22]. When the hip is passively flexed from an extended position, the thigh of the affected limb abducts and externally rotates [22,35,39]. This finding is highly suggestive of SCFE.

Asking the child to stand on the affected leg (the Trendelenburg test) causes a pelvic tilt (the unaffected side is lower) in children with SCFE if the gluteal muscle is inhibited by the pain of a chronic SCFE.

●Coxa valga slips – Coxa valga is a rare type of slip in which the femoral neck is displaced downward and anteriorly in relation to the femoral head [22,45]. Similar to patients with varus slips, patients with coxa valga typically complain of anteromedial thigh or knee pain and limited hip flexion on the affected side. However, they have lengthening, rather than shortening, of the affected limb (which leads to a circumduction) and limited range of motion in adduction, rather than abduction. Lateral radiographs are necessary for diagnosis [45].

Stability — SCFE also has been classified according to biomechanical stability as "stable" or "unstable" as follows [46]:

●Stable slips – Stable slips are defined as those in which walking and weightbearing are possible with or without crutches. Nevertheless, patients with "stable" slips should be made nonweightbearing until orthopedic consultation and treatment have occurred. (See 'Management' below.)

●Unstable slips – Unstable slips are those in which the epiphysis is displaced from the metaphysis or the patient is unable to bear weight, even with crutches, regardless of duration of symptoms. Most of these patients present with severe pain similar to a fracture of the hip. However, patients with unstable slips may have forewarning symptoms. As an example, in an observational study of 82 children, 88 percent of patients had pain in their hips, thighs, or knees for an average of 42 days before sustaining unstable SCFEs [47].

Because manipulation may cause further displacement of the epiphysis, patients who have unstable slips should immediately be placed in a wheelchair or on a stretcher and remain non-weightbearing until they have received definitive treatment. Unstable slips are at much higher risk for poor outcomes. (See 'Management' below.)

Severity — A final classification system for SCFE is based upon severity of slippage, which determines prognosis [48]. (See 'Long-term outcome' below.)

The slip is graded as mild, moderate, or severe according to the following criteria (figure 1):

●A mild slip is one in which the displacement of the epiphysis is less than one-third of the diameter of the femoral neck.

●A moderate slip is one in which the displacement of the epiphysis is more than one-third but less than one-half of the diameter of the femoral neck.

●A severe slip is one in which the displacement of the epiphysis is more than one-half of the diameter of the femoral neck.

Another method of grading slip severity is according to the epiphyseal-shaft angle of Southwick, which is measured on the frog-leg lateral radiograph (figure 2).

●Mild slips have <30 degrees of displacement compared with the unaffected side.

●Moderate slips have between 30 and 50 degrees of displacement compared with the unaffected side.

●Severe slips have greater than 50 degrees of displacement compared with the unaffected side.

EVALUATION

Radiologic evaluation — Radiographic changes may be minimal before the slip occurs and may be best seen with lateral views. Ultrasonography and magnetic resonance imaging (MRI) also can demonstrate characteristic findings [36,44].

Plain radiographs — Most cases of SCFE can be diagnosed with hip radiographs [49]. The minimum radiographic examination consists of an anteroposterior (AP) view and lateral projections of both hips. The lateral projections are obtained by the frog-leg or cross-table lateral views; true lateral hip radiographs instead of frog-leg lateral should be obtained in patients with acute onset of symptoms and probable unstable SCFE because of the potential risk of further displacement of the epiphysis with frog-leg views in such patients [50].

Bilateral views or pelvis views are obtained to permit comparison, which may facilitate identification of subtle findings, and because of the high incidence of bilateral disease. For simplicity, it may be better to order an AP radiograph of the pelvis whenever evaluating a patient with a possible slip.

Correct interpretation of the radiographs is critical [49]. In as many as 25 percent of patients whose SCFEs are missed [51], radiographs were misinterpreted, or the diagnosis could not be established with the radiographs that were obtained [52,53].

Findings of SCFE on AP and lateral projections include the following:

●AP view – On the AP view, there may be mild widening, lucency, and irregularity of the physis [54]. The most reliable sign of an early slip may be blurring of the junction between the metaphysis and the growth plate (figure 3) [55]. The height of the epiphysis may be diminished because the femoral head has rotated posteriorly. With posterior slippage of the femoral head, the portion of the head that is located behind the metaphysis may be projected as a semicircular area of increased density on the proximal part of the femoral neck; this is called the "blanch sign of Steel" (figure 4) [56].

In the normal AP view, a line drawn along the superior femoral neck (Klein's line) intersects the lateral portion of the femoral head [57]. In a patient with SCFE, the line passes outside of the epiphysis or just at its superior edge (figure 5). Also, there may be a smaller portion of the femoral head above the line compared with the contralateral hip (assuming the opposite hip is normal). Although Klein's line is a useful tool for identifying SCFE on the AP view, relying solely on it will fail to identify many slips [58,59]. A modification of Klein's line involves measuring the width of the epiphysis lateral to Klein's line to improve sensitivity. Using this modified Klein's line, a clinician should consider the diagnosis of SCFE if the epiphyseal width lateral to Klein's line differs by 2 mm or more between hips [59].

●Lateral view – Lateral projections (either frog-leg views or cross-table lateral views) are necessary to make the diagnosis in many cases and should always be obtained when evaluating a patient for SCFE [55,57-59]. The posterior displacement and step-off of the epiphysis on the femoral neck are better demonstrated on the lateral view. The cross-table view is recommended in patients who have acute onset of symptoms, since the flexion and abduction of the hip that is necessary for the frog-leg view may displace the physis in these unstable slips [23]. However, in patients with extreme obesity, it is technically difficult to obtain high-quality cross-table views.

Other studies — The diagnosis of SCFE can usually be made with plain radiographs. Additional imaging may be helpful in special circumstances, as described below:

●Computed tomography (CT) – CT may be useful in standardizing the assessment of slip severity in chronic slips [60] but has not been shown to be superior to roentgenography [61].

●Magnetic resonance imaging and bone scan – Compared with plain radiographs and CT, MRI is better able to detect early, radiographically occult but symptomatic preslips [62]. In these patients, MRI demonstrates widening of the physis with surrounding edema, which is essentially diagnostic of the disease [63]. However, radiographs remain the preferred initial diagnostic screening tool for SCFE.

MRI and bone scan are useful adjuncts in the evaluation of children with SCFE who are at risk for osteonecrosis. MRI can be used to evaluate femoral head circulation and the extent and distribution of osteonecrosis if osteonecrosis is present. Early in the course of osteonecrosis, bone scan may show decreased uptake in the femoral head, but later bone scans may show increased uptake as the necrotic bone is replaced with new bone. (See 'Osteonecrosis' below.)

●Ultrasound – Ultrasonography has little role in the routine evaluation of patients with SCFE [35]. Its use has been described in the diagnosis, staging, and follow-up of SCFE, and is supported by some authors [36,64-67]. In experienced hands, ultrasonography may confirm the diagnosis of SCFE in a child whose plain radiographs are normal, but MRI is more commonly used in such situations (as described above) [35,68].

Ancillary studies

Typical SCFE — Patients with a typical presentation of SCFE (child with obesity in early adolescence) are unlikely to have an underlying cause of physeal weakness (eg, genetic disease, renal failure or endocrine disorder). Because the findings of hypothyroidism in children may be subtle, some authors recommend screening T4, TSH, and bone age for all patients newly diagnosed with SCFE [8].

However, our approach is to obtain these tests only for those patients who have height <10^th percentile or other evidence of an endocrine disorder [14,69]. In one study of 166 patients with SCFE, 13 had an associated endocrinopathy. Ninety percent of SCFE patients with an underlying endocrinopathy had height <10^th percentile; 99 percent of SCFE patients without an endocrinopathy had height ≥10^th percentile (sensitivity and negative predictive value, respectively) [14]. (See "Acquired hypothyroidism in childhood and adolescence".)

Atypical SCFE — Atypical SCFE refers to the presence of SCFE in children with an underlying risk factor that interferes with the ability of the physis to withstand shear stress, such as renal failure, endocrine disturbance (eg, hypothyroidism or growth hormone deficiency), genetic disorder (eg, Down or Rubenstein-Taybi syndromes), or radiation therapy.

The possibility of atypical SCFE is increased when SCFE occurs in children with the following characteristics [19]:

●Younger than 10 years

●Older than 16 years

●Weight less than the 50^th percentile for age and sex

In such patients, evaluation for kidney disease or endocrine disorders, especially hypothyroidism is warranted [14,19,20,22]. (See "Chronic kidney disease in children: Clinical manifestations and evaluation" and "Causes of short stature", section on 'Endocrine causes of short stature'.)

DIAGNOSIS — As described above, the diagnosis of SCFE usually is made based upon plain radiographs, which reveal an apparent posterior displacement of the femoral epiphysis, like ice cream slipping off a cone (image 1). The earliest plain radiographic changes are widening and irregularity of the physis, with thinning of the proximal epiphysis. These changes are best seen on lateral views [70]. If the radiograph is normal but suspicion for early SCFE is high, MRI can demonstrate widening of the physis with surrounding edema, essentially diagnostic of the disease [63]. (See 'Plain radiographs' above.)

DIFFERENTIAL DIAGNOSIS — Avascular necrosis of the hip (Legg-Calve-Perthes disease) (image 2) and development dysplasia of the hip with late diagnosis in older children and adolescents are additional causes of Trendelenburg gait and chronic knee or hip pain that may present in a manner similar to SCFE (table 1). Plain radiographs of the hip typically identify the specific cause. (See "Approach to hip pain in childhood", section on 'Legg-Calvé-Perthes and secondary avascular necrosis' and "Developmental dysplasia of the hip: Clinical features and diagnosis", section on 'Diagnostic imaging'.)

Other causes of hip pain, knee pain, and limp in children and their diagnosis are discussed in greater detail separately:

●(See "Evaluation of limp in children" and "Overview of the causes of limp in children".)

●(See "Approach to chronic knee pain or injury in children or skeletally immature adolescents".)

●(See "Approach to hip pain in childhood".)

MANAGEMENT

Operative stabilization — The treatment of SCFE is operative stabilization:

Preoperative management — Children with SCFE should be made non-weightbearing and should receive prompt consultation with an orthopedic surgeon with pediatric expertise. Patients with acute (unstable) slips should be admitted to the hospital for treatment at initial presentation [22]. Hospital admission and bed rest may also be necessary for patients with bilateral SCFE, whether acute or chronic.

Patients with unilateral chronic (stable) slips also require urgent evaluation because of the risk of further slippage; they may be referred to an emergency department or an orthopedic surgeon experienced in treating children's hip problems. They must avoid bearing weight until they have undergone orthopedic evaluation and operative stabilization [44]. The use of crutches or a wheelchair and bed rest is strongly recommended to prevent further slippage as demonstrated by the following image (image 3).

Operative goals — The operative goals are stabilization of the diseased physis to prevent further slippage and avoidance of complications [50]. The gold standard for stabilization of chronic/stable slips, regardless of severity, is the use of a single cannulated screw placed in the center of the epiphysis [44] although use of growing implants has been proposed [71]. Stabilization usually involves pinning in situ (ie, without attempt at reduction) because manipulation has been found to correlate with a poorer long-term prognosis [39,72]. In acute and unstable hips, use of a second screw to increase mechanical stability must be weighed against the increased risk of screw malposition and joint penetration [73,74]. Closed reduction of an acute slip before pinning is controversial. Screw fixation is the most commonly used and widely accepted treatment for SCFE. Decisions regarding timing of surgery and operative technique should be left to the discretion of the orthopedic surgeon. (See 'Complications' below.)

Prophylactic pinning of the unaffected hip — Prophylactic pinning of the opposite hip is considered an option by some surgeons [75]. Approximately 30 to 60 percent of patients with unilateral SCFE at presentation eventually have SCFE in the contralateral hip [6-8,76]. Patients with underlying endocrine disorders have an even higher risk of subsequent bilateral involvement (up to 100 percent) [8,77]. A reduction in body mass index in patients with obesity may reduce the risk of subsequent contralateral SCFE [78]. In more than 80 percent of cases of sequential slips, the second slip occurs within 18 months of diagnosis of the first slip [4]. Age at presentation of <10 years in boys and <12 years in girls has been associated with development of contralateral slip as has skeletal immaturity [79,80]. Second slips are often asymptomatic.

However, prophylactic pinning of the contralateral hip is controversial [75,81-83]. Advocates of prophylactic pinning suggest second slips often are unstable, predisposing the patient to an increased risk of osteonecrosis [84]. Advocates of observation suggest that close follow-up permits early identification and treatment of contralateral SCFE and prevents unnecessary surgery and potential complications, although major complications of prophylactic pinning (eg, need for repeat surgery, fracture, or avascular necrosis) appear to be rare [75,82]. Two decision analyses, using different underlying assumptions, reached different conclusions [85,86]. In a series of 133 children with SCFE followed for a minimum of two years, a contralateral slip occurred in 15 percent [87]. Most of these slips were mild but about one third of the patients had significant pain and one patient developed avascular necrosis and an unstable hip. Additional information is needed to more accurately predict which children with unilateral idiopathic SCFE are at increased risk for contralateral SCFE and to better quantify the risks and benefits of observation versus prophylactic pinning [83]. The modified Oxford bone age score may be useful in identifying the risk of development of contralateral SCFE [80]. Furthermore, in a meta-analysis of 20 studies (almost 1500 patients with SCFE), development of a contralateral SCFE was associated with a higher posterior sloping angle on frog leg radiograph compared with no contralateral SCFE (mean angle 16 versus 12 degrees, respectively) [88].

Postoperative care — Postoperative management usually includes a period of limited weightbearing with crutches or a walker. In bilateral cases, patients are taught to use a four-point gait (eg, the right crutch followed by the left leg, followed by the left crutch, followed by the right leg, etc). After six to eight weeks, crutches are discontinued, and regular activities are gradually resumed. Return to sports participation depends upon the residual limitation of motion, since most patients lose internal hip rotation.

To prevent delay in diagnosis of the second slip in children who do not undergo prophylactic pinning, all patients with unilateral involvement, particularly those with endocrinopathies, should be followed closely by an orthopedic surgeon. The patient should be scheduled for repeat examinations of the contralateral hip during the first one to two years after initial diagnosis [89]. Close follow-up should continue until the child has finished growing. In addition, patients and parents/primary caregivers should be instructed to seek medical attention immediately if they experience any symptoms of SCFE (eg, nonradiating, dull, aching pain in the hip, groin, thigh, or knee).

In selected cases with severe deformity, reconstructive surgery can be considered. A number of proximal femoral osteotomies have been proposed to correct excessive hip varus and extension. Because the risk of avascular necrosis is increased with more proximal femoral neck osteotomies, the most commonly performed reconstructive procedure is the intertrochanteric osteotomy of Southwick [90]. Surgical dislocation is another technique that is coming into use; initial results in experienced hands are promising [91,92].

COMPLICATIONS — The complications of SCFE include osteonecrosis of the femoral head and chondrolysis, and femoroacetabular impingement, both of which increase the risk of subsequent development of osteoarthritis [93-98]. (See 'Long-term outcome' below.)

Osteonecrosis — Osteonecrosis (also called aseptic necrosis, avascular necrosis, and ischemic necrosis) of the femoral head is the most serious complication of SCFE and has the worst prognosis. The natural history of osteonecrosis after treatment for SCFE is one of gradual degenerative changes for which reconstructive surgery is often required [99].

The rate of occurrence of osteonecrosis increases with increasing severity of the slip (table 2), occurring in 15 percent of patients with acute slips [100]. Avascular necrosis rarely occurs in untreated chronic slips since the gradual slipping process permits maintenance of blood supply to the caput through adaptation of the vasculature [101]. However, it can be a complication of operative pinning (if the lateral epiphyseal artery, which supplies the superior weightbearing portion of the femoral head, is injured during surgery) [22].

Unstable SCFE is an important predictor for the development of osteonecrosis [100,102], particularly if vascular injury occurs at the time of the slip [101]. Anterior physeal separation at the time of the slip also appears to be associated with subsequent development of osteonecrosis [103].

Osteonecrosis should be suspected when a patient with a history of SCFE complains of persistent pain and stiffness of the hip [22]. Early in the course of osteonecrosis, the bone scan may show decreased uptake in the femoral head, but later bone scans may show increased uptake as the necrotic bone is replaced with new bone. Osteonecrosis also may be apparent on plain radiographs (image 4) or MRI. SCFE patients who develop or are suspected to have osteonecrosis should be referred to an orthopedic surgeon.

Chondrolysis — Chondrolysis, or narrowing of the joint space and loss of articular cartilage, can occur with an untreated SCFE or develop postoperatively. It is present in up to 7 percent of cases even before treatment [93]. It is more common among girls than boys and is particularly common among Black girls, having occurred in 51 percent in one series [104]. It also is more common among patients with prolonged immobilization and in whom the stabilizing pins penetrate into the joint [22].

The clinical manifestations of chondrolysis include pain and flexion deformity of the hip, with restricted range of motion in all planes. Radiographs show regional osteoporosis, followed by narrowing of the articular cartilage. MRI demonstrates narrowing of the joint space and irregularity of the articular cartilage. Changes on bone scan (decreased activity in the physis) may precede changes on plain radiographs [105].

The course varies from spontaneous resolution to partial recovery to rapid destruction of the articular cartilage with fibrosis and ankylosis of the hip joint. SCFE patients who develop or are suspected of having chondrolysis should be referred to an orthopedic surgeon.

Femoroacetabular impingement (FAI) — Femoroacetabular impingement is an abnormal contact between the proximal femoral metaphysis and the acetabular rim. It is believed to be caused by residual abnormal morphology with prominence of the femoral metaphysis abutting the acetabular rim. SCFE is one of the most frequent underlying causes for FAI [106]. This may be symptomatic and leads to the premature development of osteoarthritis of the hip [96-98]. In this instance, grade of slip is not a predictive tool for the development of FAI, as even mild slips are at risk [107]. Several surgical techniques are proposed to address potential FAI by restoring the anatomy of the proximal femur or correcting healed SCFE [108-111]. However, evidence is lacking to suggest one approach over another.

LONG-TERM OUTCOME — The prognosis of SCFE is related to the severity of slip (table 2) [37,72]. Mild slips are usually well tolerated. However, patients with a history of SCFE (even mild) are at increased risk for premature development of osteoarthritis (degenerative arthritis) [112], and unrecognized SCFE is thought to be a common cause of osteoarthritis [113]. In patients without complications, osteoarthritis of the hip usually develops over a course of decades. The rate of osteoarthritis at 20- to 40-year follow-up and the incidence of osteonecrosis and chondrolysis increase with increasing severity of slip (table 2) [72]. Femoroacetabular impingement and the development of osteoarthritis are not related to severity of the slip because even mild slips are at risk [107].

Regardless of severity of slip, reconstructive arthroplasty for degenerative changes may be needed for persistent symptoms. As an example, in an observational study of 146 patients with SCFE who underwent in situ pinning and had follow-up 2 to 43 years later, reconstructive surgery was needed for persistent symptoms, primarily pain, stiffness and functional limitation, in 12 percent of patients including patients with mild, moderate, or severe slips [114]. Of patients not undergoing reconstructive surgery, approximately one-third had persistent mild pain.

SUMMARY AND RECOMMENDATIONS

●Definition – SCFE is characterized by a displacement of the capital femoral epiphysis from the femoral neck through the physeal plate. The mean age of presentation is 12 years in girls and 13.5 years in boys, near the time of peak linear growth. The male-to-female ratio is approximately 1.5:1. Obesity is a significant risk factor. (See 'Definition' above and 'Epidemiology' above.)

●Clinical manifestations – The two most common features of the presentation of SCFE are pain and altered gait. The classic presentation is that of an adolescent with obesity and a complaint of nonradiating, dull, aching pain in the hip, groin, thigh, or knee, and no history of preceding trauma. The pain is increased by physical activity and may be chronic or intermittent. The absence of pain, or pain localized to the knee or thigh instead of the hip, can lead physicians to overlook the diagnosis. Physical examination may demonstrate hip pain on palpation and limitation of hip range of motion, especially internal rotation and flexion. (See 'Clinical manifestations' above.)

●Classification – SCFE is traditionally classified into four patterns of presentation on the basis of intensity and duration of symptoms: preslip, acute, acute-on-chronic, and chronic. (See 'Pattern of presentation' above.)

●Diagnosis – The diagnosis of SCFE is usually made on plain radiographs, which reveal an apparent posterior displacement of the femoral epiphysis, like ice cream slipping off a cone (image 1 and image 3). The earliest plain radiographic changes are widening and irregularity of the physis, with thinning of the proximal epiphysis (figure 3). These changes are best seen on lateral views. If the radiograph is normal but suspicion for early SCFE is high, MRI may demonstrate widening of the physis with surrounding edema, essentially diagnostic of the disease. (See 'Diagnosis' above and 'Radiologic evaluation' above.)

●Management – The treatment of SCFE is operative. Children with SCFE, regardless of classification, should receive prompt consultation with an orthopedic surgeon with pediatric expertise; they must avoid bearing weight until they have undergone orthopedic evaluation. Patients with acute (unstable) slips should be admitted to the hospital for treatment at initial presentation. Hospital admission and bed rest may also be necessary for patients with bilateral SCFE, whether acute or chronic. (See 'Preoperative management' above and 'Operative stabilization' above.)

Approximately 30 to 60 percent of patients with unilateral SCFE at presentation eventually have SCFE in the contralateral hip. To prevent delay in diagnosis of the second slip, all patients with unilateral involvement who do not undergo prophylactic repair of the contralateral hip should be followed closely by an orthopedic surgeon until after the child has finished growing. Patients and parents/primary caregivers should be instructed to seek medical attention immediately if they experience symptoms of SCFE (eg, nonradiating, dull, aching pain in the hip, groin, thigh, or knee). (See 'Prophylactic pinning of the unaffected hip' above.)

●Complications – The complications of SCFE include osteonecrosis of the femoral head, femoroacetabular impingement, and chondrolysis. All of these conditions increase the risk of subsequent development of osteoarthritis. (See 'Complications' above.)

●Long-term outcome – The prognosis of SCFE is related to the etiology and severity of the slip (figure 1 and table 2). (See 'Long-term outcome' above.)