summary Slipped Capital Femoral Epiphysis, is a common condition of the proximal femoral physis that leads to slippage of the metaphysis relative to the epiphysis, and is most commonly seen in adolescent obese males. Diagnosis can be confirmed with radiographs of the hip. Treatment is usually percutaneous pin fixation. Contralateral pinning is indicated for patients at high risk, such as those with an initial slip at age < 10, obese males, and those with endocrine disorders. Epidemiology Incidence most common disorder affecting adolescent hips 10 per 100,000 Demographics more common in obese children males male to female ratio is 2:1.4 specific ethnicities including African Americans, Pacific islanders, Latinos periods of rapid growth 10-16 years of age average age range is 12-13.4 for boys 11.2-12.2 for girls occurs when going through puberty Anatomic location left hip is a more common location can be bilateral in 17% to 50% (average of 25%) Risk factors obesity single greatest risk factor recent data shows a trend towards younger age and increased frequency of bilateral presentation may be related to increased rates of childhood obesity acetabular retroversion and femoral retroversion secondary to increased mechanical shearing forces at the physis history of previous radiation therapy to the femoral head region elevated leptin levels 4.9x increased in the odds of developing a SCFE in patients with elevated leptin, even when controlling for obesity status, sex and race Etiology Pathophysiology mechanism occurs due to axial and rotational mechanical forces which act on a susceptible physis direction of slip/angulation metaphysis translates anterior and externally rotates epiphysis remains in the acetabulum and lies posterior/inferior to the translated metaphysis pathoanatomy slippage occurs though the hypertrophic zone of the physis histology sections reveal granulation tissue between the columns in the hypertrophic zone cartilage in the hypertrophic zone acts as a weak spot increased risk in adolescence because: the perichondrial ring thins and weakens undulating mammillary processes in physis unlocks, further destabilizing the physis physis is still vertical in this age group (160° at birth to 125° at skeletal maturity), which results in increased shearing forces the epiphyseal tubercle can provide a rotational pivot point this represents an anatomic structure in the posterior superior epiphysis that shrinks with skeletal maturity similar to Salter-Harris type I fracture, but may differ based on antecedent epiphysiolysis slower displacement periosteum remains intact (chronic SCFE) in acute SCFE, periosteum can be partially torn anteriorly over the prominent metaphysis Associated conditions endocrine disorders associated conditions hypothyroidism most common etiology of nonidiopathic SCFE labs: elevated TSH renal osteodystrophy labs: elevated BUN and creatinine growth hormone deficiency panhypopituitarism endocrine workup indicated if child is < 10 years old weight is < 50th percentile Down syndrome ANATOMY Osteology normal proximal femur neck shaft-angle is 130 +/- 7° normal proximal femur anteversion is 10 +/- 7° proximal femur consists of tensile and compressive trabecular groups proximal femoral physis is where pathology occurs with slip of epiphysis and metaphysis Ligaments iliofemoral, ischiofemoral and pubofemoral ligaments attach to outer hip capsule and help to prevent excessive hip motion Blood supply a confluence of arteries which forms an extracapsular arterial ring that divides into the ascending cervical arteries which supply the femoral neck and head via perforators main blood supply in adolescents and adults is the medial femoral circumflex artery which is derived from the lateral epiphyseal artery lateral femoral circumflex contributes to anterior arterial ring superior and inferior gluteal arteries also give small contributions to arterial ring artery of ligamentum teres comes from obturator or medial femoral circumflex plays a relatively insignificant role in blood supply initial slip as well as iatrogenic causes are thought to increase the risk of damage to blood supply unstable SCFE at greater risk for blood supply injury Biomechanics in double-leg stance, the force vector through hip is vertical and in single-leg stance it is parallel to the neck and head axial/rotational forces through physis place stress on weak hypertrophic zone in population at risk Classification Loder classification Loder Classification Based on ability to bear weight Stable Able to bear weight with or without crutches Minimal risk of osteonecrosis (<10%) Unstable Unable to ambulate (not even with crutches) High risk of osteonecrosis (24-47%) Temporal classification Temporal Classification Based on duration of symptoms; rarely used; no prognostic information Acute Symptoms that persist for less than 3 weeks Chronic Symptoms that persist for more than 3 weeks Acute on Chronic Acute exacerbation of long-standing symptoms Southwick Slip Angle Classification epiphyseal-diaphyseal angle can be measured on both AP and frog lateral pelvis radiographs slip angle classification is based on the degree of difference between the affected and unaffected hip if bilateral hips are involved, use 145° as "unaffected" hip reference for AP and 10° as "unaffected" hip reference for lateral Southwick Slip Angle Classification Based on femoral epiphyseal-diaphyseal angle difference Mild < 30° Moderate 30-50° Severe > 50° Grading system Grading System Based on percentage of slippage Grade I 0-33% of slippage Grade II 34-50% of slippage Grade III >50% of slippage Presentation History most commonly atraumatic, although some present after an injury pain has often been present for several months Symptoms pain in hip (52%), groin (14%) and thigh (35%) pain is most common presenting symptom knee pain 15-50% present with knee pain due to pain activation of the medial obturator nerve can lead to missed diagnosis patients prefer to sit in a chair with affected leg crossed over the other duration symptoms are usually present for weeks to several months before diagnosis is made 88% of patients that presented with an unstable SCFE had unappreciated antecedent symptoms for ~42 days prior to diagnosis Physical exam inspection abnormal gait / limp antalgic, waddling, externally rotated gait or Trendelenburg gait abnormal leg alignment externally rotated foot progression angle motion obligatory external rotation during passive flexion of hip (Drehmann sign) due to a combination of synovitis and impingement of the displaced anterior-lateral femoral metaphysis on the acetabular rim loss of hip internal rotation, abduction, and flexion neurovascular weakness and thigh atrophy no true neurovascular compromise usually seen Imaging Radiographs recommended views AP & frog-leg lateral of both hips lateral radiograph is best way to identify a subtle slip if slip is unstable, cross-table lateral should be performed instead of frog-leg findings Klein's line line drawn along superior border femoral neck on AP pelvis will intersect less of the femoral head or not at all in a child with SCFE intersects lateral femoral head in a normal hip due to natural lateral overhang of the epiphysis evaluate for asymmetry between sides "S" sign line drawn along inferior cortical outline of femur in frog-leg lateral view normally extends from proximal femur head/neck junction to the proximal femoral physis but in SCFE there will be a sharp turn or break in continuity of this line epiphysiolysis (growth plate widening or lucency) an early radiographic finding blurring of proximal femoral metaphysis known as the metaphyseal blanch sign of Steel seen on AP due to overlapping of the metaphysis and posteriorly displaced epiphysis MRI indications may help diagnose a preslip condition when radiographs are negative findings growth plate widening edema in metaphysis decreased signal on T1, increased signal on T2 STUDIES Labs if patient is <10 years old, pre-pubertal or has short stature or weight below 50th percentile for age. consist of: TSH free T4 BUN serum creatinine DIFFERENTIAL Septic arthritis/transient synovitis Osteomyelitis Legg-Calve-Perthes disease Developmental dysplasia of hip (DDH) Traumatic injuries adductor strain, AIIS avulsion, pelvic/femur fractures Treatment Operative percutaneous in situ fixation indications both stable and unstable slips technique one vs. two cannulated screws is controversial 2 screw constructs have greater biomechanically stability than the single screw constructs capsulotomy is also controversial goal is to decrease intra-capsular pressure in the setting of unstable SCFE intracapsular pressure in unstable SCFE is double that of control hips, while pressure in stable SCFE is roughly equal to control hips may mitigate intracapsular tamponade, with lower-quality evidence suggesting decreased rates of AVN following unstable SCFE if ICP monitor is introduced into the epiphysis and a monophasic waveform is observed, the next best step is decompression of the hip joint, followed by capsulotomy if decompression does not improve bloodflow outcomes good or excellent outcomes in >90% of cases important to understand that fixation does not treat deformity at head/neck junction has led to popularization of other techniques that correct deformity to mitigate long-term risk of chondral damage contralateral hip prophylactic fixation indications controversial current indications are patients at high risk of contralateral slip initial slip at young age (< 10 years-old) those with open triradiate cartilage obese males endocrine disorders (e.g. hypothyroidism) open epiphyseal reduction and fixation indications (controversial) unstable and severe slips technique capital realignment via the Modified Dunn procedure thought to allow acute deformity correction while maintaining blood supply outcomes there is a steep learning curve AVN rates of ~26% (compared to 24% for unstable SCFE treated by in situ screw fixation) overall complication rate is 37% Operative management of symptoms after initial in situ fixation osteochondroplasty indications symptomatic femoroacetabular impingement (FAI) of cam lesion from metaphyseal bump mild to moderate SCFE deformity (slip angle < 30°) techniques arthroscopy limited anterior arthrotomy surgical hip dislocation outcomes no long term data, but appears to show improvements in pain/function low rates of osteonecrosis poor outcomes in cases with pre-existing cartilage damage proximal femoral osteotomy indications painful or function-limiting proximal femoral deformity severe SCFE deformity (slip angle >30- 45°) absence of severe hip osteoarthritis and osteonecrosis technique femoral neck cuneiform osteotomy can provide greatest correction of deformity use is controversial due to high rates of AVN (37%) and osteoarthritis (37%) intertrochanteric (Imhauser) osteotomy most commonly used subtrochanteric (Southwick) osteotomy outcomes good to excellent functional results 2-7% risk of AVN Useful in preventing hip arthrosis long-term Techniques Percutaneous in situ fixation goal to stabilize the epiphysis from further slippage approach percutaneous wire insertion to anterior/lateral thigh using radiographic localization technique reduction a forceful reduction is not indicated and increases risk of osteonecrosis "serendipitous reduction" may be obtained with positioning on OR table number of screws a single cannulated screw typically sufficient and decreases risk of osteonecrosis (compared to multiple screws) some surgeons may add second screw for unstable SCFE screw insertion perpendicular to physis screw starts on the anterior surface of the proximal femur in order to cross perpendicular to the physis and enter into the central portion of the femoral head on both the AP and lateral views starting point should not be medial to intertrochanteric line - will result in impingement between the head of the screw and acetabulum with hip flexion oblique to physis in severe slips, a relatively oblique insertion starting at the intertrochanteric region may be required, rather than perpendicular, to avoid impingement from head of the screw screw position advance until 5 threads cross physis < 5 threads engaged in epiphysis increases risk of progression of slip >10° in one study, those with <5 threads across the epiphysis progressed 41% of the time compared to 0% of those with >= 5 threads into the epiphysis screws should be ~ 5mm from subchondral bone in all views imaging confirm that pin is not penetrating the hip joint there is a higher risk with screw placement in anterior/superior quadrant of femoral head approach-withdraw technique rotate hip from maximal internal rotation or maximal external rotation under live fluoroscopy the screw tip should appear to approach the subchondral bone, then withdraw from it the moment of change from approach to withdraw is the true position of the screw and can be used to insert the screw to appropriate position appropriate position confirmed when screw does not violate articular surface in all views postoperatively stable slips are able to bear weight after fixation unstable slips are typically kept touch-down weight bearing complications osteonecrosis of femoral head residual deformity & limb length discrepancy chondrolysis higher risk if pin placed into anterosuperior femoral head as screw can penetrate the joint here Surgical hip dislocation, open capital realignment and fixation (Modified Dunn procedure) goal to correct the acute proximal femoral deformity and stabilize the epiphysis while protecting the femoral head blood supply technique surgical hip dislocation using the Ganz technique lateral decubitus position straight lateral skin incision centered over greater trochanter interval: gluteus maximus (inferior gluteal n.) / gluteus medius (superior gluteal n.) trochanteric flip osteotomy Z-shaped anterior capsulotomy visualize slip with prominent metaphysis temporarily pin epiphysis with K-wires prior to dislocation bone hook placed around femoral neck for traction ligamentum teres cut hip is dislocated develop retinacular soft tissue flaps incise periosteum along femoral neck extend incision distally to level of lesser trochanter, to reduce tension on retinacular vessels bluntly develop periosteal flaps anteriorly and posteriorly using periosteal elevator mobilize epiphysis starting anterior, use chisel to free epiphysis entirely from metaphysis epiphysis will remain attached to posterior retinacular flap (blood supply) debride metaphysis there will be prominent reactive callus along the posterior metaphysis, which needs to be removed to permit proper epiphyseal reduction and avoid kinking of retinacular vessels reduce epiphysis to metaphysis fixation 2-3 3.0mm K-wires one antegrade starting from fovea across epiphysis one to two retrograde across epiphysis 1 or 2 screws may also be used (6.5mm - 7.3mm) greater trochanter osteotomy must be re-fixed postoperatively touch-down weight bearing for 6 weeks complications osteonecrosis of femoral head theoretically higher risk of disrupting blood supply with this approach Osteochondroplasty goal to address pain and loss of motion related to hip impingement from prominent metaphyseal bump in mild to moderate chronic SCFE deformity technique arthroscopy reserved for mild SCFE deformity remove metaphyseal bump with arthroscopic burr difficult to fully resect superior and lateral portions of the bump limited anterior arthrotomy useful when metaphyseal bump cannot be fully removed arthroscopically performed using modified Smith-Peterson approach surgical hip dislocation moderate SCFE deformity trochanteric flip osteotomy performed hip is dislocated anteriorly curved osteotome used to remove bump burr is used to recreate normal contour of head-neck junction Flexion intertrochanteric (Imhauser) femoral osteotomy goal to correct symptomatic proximal femoral deformity in moderate to severe chronic SCFE deformity technique lateral approach supine position straight lateral skin incision from greater trochanter distal down the femoral shaft reflect vastus lateralis to expose lateral femur transverse osteotomy just proximal to lesser trochanter correction flexion through the osteotomy internal rotation of distal shaft mild valgus correction postoperative touch-down weight bearing for 3 months complications osteonecrosis arthritis Complications Osteonecrosis of femoral head incidence low in stable slips, 24-47% in unstable slips unstable slip is greatest predictor risk factors initial trauma operative complication (4-6%) hardware placement in posterosuperior femoral neck has the greatest risk of disrupting the vascular supply treatment symptomatic management, core decompression, arthroplasty Contralateral hip SCFE incidence 20-80% after unilateral hip fixation most common complication after unilateral surgical fixation risk factors male, obesity, young age of initial slip (< 10 years old, open triradiate cartilage), endocrine disorders treatment/prevention surgical fixation of contralateral hip as needed weight loss programs decreased BMI reduces rates of subsequent contralateral SCFE Chondrolysis incidence 0-2% seen with narrowed joint space, pain, and decreased motion risk factors unrecognized implant penetration of the articular surface occurring in 0-2% of cases pin placement into the anterosuperior quadrant of the femoral head has the highest rate of joint penetration intra-articular hardware penetration best assessed by CT scan decreased prevalence with the use of modern fluoroscopy spica cast immobilization Residual proximal femoral deformity & limb length discrepancy risk factors increased α-angle associated with symptomatic impingement caused by failure of proximal femur to remodel can lead to a pistol-grip deformity treatment intertrochanteric osteotomy (Imhauser) produces flexion, internal rotation and valgus subtrochanteric osteotomy (Southwick) femoral neck cuneiform osteotomy (controversial due to high rate of osteonecrosis and arthritis) Slip progression incidence 1-2% of cases following single screw fixation Delayed diagnosis risk factors increased slip severity knee/thigh pain vs. hip pain stable slips Medicaid insurance Infection incidence 0-2% Chronic pain incidence 5-10% Degenerative arthritis Labral tearing and degeneration risk factors seen with high anterior and medial 2nd screw in-situ fixation if screw lies medial to intertrochanteric line on AP radiograph, has increased risk of impingement on acetabulum and labrum with hip flexion