markedly different anatomy to an adult pelvis given the amount of cartilage creating a lot more elasticity at the joints
injuries of the pelvic ring are rare and require a significant mechanism
common injuries specific to the pediatric population include the
slipped upper femoral epiphysis
various apophyseal avulsion fractures around the pelvis
slipped upper femoral epiphysis has a typical patient demographic
high BMI (this can be obese or just a larger built patient)
boys presenting later (10-17 years) than girls (8-15 years)
Slipped upper femoral epiphysis
Illustration credit: Andrew Murphy
Slipped upper femoral epiphysis (SUFE), also known as a slipped capital femoral epiphysis (SCFE), (plural: epiphyses) is a relatively common condition affecting the physis of the proximal femur in adolescents. It is one of the commonest hip abnormalities in adolescence and is bilateral in 20-40% of cases 10.
Epidemiology
Slipped upper femoral epiphysis is more common in boys than girls and more common in African Caribbean patients than Caucasian patients. The age of presentation is somewhat dependent on gender with boys presenting later (10-17 years) than girls (8-15 years) 2.
Patients may present in different ways depending on the epiphysis stability and the duration of the onset of the symptoms.
Patients with an unstable slip present similarly to those with an acute femoral fracture and are unable to bear weight on the affected limb. A patient with a stable slip can tolerate weight bearing. It's important to understand that this refers to clinical presentation, but even if the patient initially able to bear weight is at risk of evolving to an acute displacement if bed rest is not established 10.
Regarding the onset of symptoms, SCFE is usually classified into three groups 10:
acute: severe hip pain and inability to bear weight, usually after a minor trauma, with prodromal symptoms such as vague groin or thigh pain for up to 3 weeks before the acute presentation
chronic: represents the most common presentation. Vague groin and thigh pain for more than 3 weeks, may progress to a limp
acute-on-chronic: the prodromal symptoms have been present for more than 3 weeks, but there is a sudden worsening of the symptoms, including becoming unable to bear weight when previously able to
Pathology
Slipped upper femoral epiphysis is a type I Salter-Harris growth plate injury due to repeated trauma on a background of mechanical and probably hormonal predisposing factors.
During growth, there is a widening of the physeal plate which is particularly pronounced during a growth spurt. Also, the axis of the physis alters during growth and moves from being horizontal to being oblique. As the physis becomes more oblique, shear forces across the growth plate increase and result in an increased risk of fracture and resultant slippage.
Radiographic features
In all situations, especially when imaging children, the fewest number of radiographs, with the smallest exposed area is performed.
Plain radiograph
The radiographic series used to investigate varies depending on institution:
AP and frog-leg: two view assessment is common, often done bilateral as high number of these injuries are bilateral (as well as the added benefit of comparing to a normal side) 11
In the pre-slip phase, there is a widening of the growth plate with irregularity and blurring of the physeal edges and demineralization of the metaphysis. This is followed by the acute slip, which is posteromedial. In a chronic slip, the physis becomes sclerotic and the metaphysis widens (coxa magna).
The slip that occurs is posteriorand, to a lesser extent, medial. It is therefore is more easily seen on the frog-leg lateral view rather than the AP hip view. Because the epiphysis moves posteriorly, it appears smaller because of projectional factors.
On the AP, a line drawn up the lateral edge of the femoral neck (line of Klein) fails to intersect the epiphysis during the acute phase (Trethowan sign).
The metaphysis is displaced laterally and therefore may not overlap the posterior lip of the acetabulum as it should normally (loss of triangular sign of Capener) 5.
The metaphyseal blanch sign, a sign seen on AP views, involves increases in the density of the proximal metaphysis. It represents the superposition of the femoral neck and the posteriorly displaced capital epiphysis.
Alignment of the epiphysis with respect to the femoral metaphysis can be used to grade the degree of slippage: see SUFE grading.
Ultrasound
Ultrasound may be performed in the assessment of hip pain. However, it should not be used as a replacement for a pelvic radiograph. Findings are nonspecific and may include hip joint effusion. In some cases, malalignment of the femoral epiphysis and metaphysis may be seen.
On an AP radiograph a line along the superior margin of the femoral neck (line of Klein) should intersect the lateral corner of the epiphysis.
Slip is graded based on the displacement of the epiphysis in relation to the metaphysis 3:
mild: lateral edge of the epiphysis is within the lateral third of the metaphysis
moderate: lateral edge between the lateral 1/3 and halfway point of the metaphysis
severe: medial third (over the halfway point of the metaphysis)
On a true lateral radiograph, the angle (slip angle) which the epiphysis makes with the metaphysis may also be employed (sometimes known as the Southwick head shaft angle) 2.
Findings: Slipped upper femoral epiphysis ranging from normal to severe. The green line on the normal represents the line of Klein drawn on the superior edge of the femoral neck intersecting the lateral aspect of the superior femoral epiphysis. The severity of a SCFE is based on the position of the femoral head about the metaphysics. Pre-slip is a widening of the growth plate, mild is within the first third, moderate within the second third, and severe within the final third and beyond.
Findings: Slipped upper femoral epiphysis ranging from grade I to III based on the Southwick angle and lateral projection between the head and neck. Pre-slip is a widening of the growth plate, mild is within the first third, moderate within the second third and severe within the final third and beyond.
Findings: On the AP view a small effusion can be seen inferior medial of the right neck of femur. The line of Klein intersects the epiphysis and the femoral heads are symmetrical. On the frog-leg view, there is a clear abnormality on the right with the slip of the upper femoral epiphysis (SUFE).
Findings: The asymmetric thickening of the soft tissue lateral to the left femoral neck compared to the right suggests a joint effusion. Left femoral epiphysis presents a widening of the growth plate with irregularity and blurring of the physeal edges, slight sclerosis of the metaphysis, and mild posteromedial slip. Slipped upper femoral epiphysis
Case credit: Hemilianna Hadassa Silva Matozinho, rID: 81469
Findings: Hips are well formed with no dysplasia. Asymmetry in the lines of Klein, which appears misaligned on the left particularly on the lateral projection. Femoral capital epiphyses are symmetrical in size and appearance.
Findings: The right femoral proximal epiphysis demonstrates a failure of the epiphysis to intersect Klein's line with the metaphysis displaced laterally indicating a Salter-Harris 1 fracture. This is in keeping with moderate-grade slipped upper femoral epiphysis (SUFE). Nice example of acute slip in one hip and previously treated SUFE of the contralateral hip.
secondary ossification centers are the weakest point in the muscular–tendinous-osseous chain and hence the failure point during forceful contraction
normally present after feeling a cracking sensation in the pelvis after a quick change in direction
injuries can be subtle and knowing the common avulsion points is a useful checklist approach to the acute pediatric pelvis
the key is assessing for symmetry and correlating with the patient's symptoms
Transient synovitis of the hip
Transient synovitis of the hip refers to a self-limiting acute inflammatory condition affecting the synovial lining of the hip. It is considered one of the most common causes of hip pain and limping in young children. Over 90% of hip joint effusions in children tend to be due to transient synovitis 10.
Epidemiology
It typically affects young children (3-8 years of age). There is a recognized increased male predilection.
Clinical presentation
Patients typically present with hip pain for one to three days, associated with limping or the refusal to bear weight.
Pathology
Their exact pathogenesis is not well known. Several theories have been proposed. In some situations, it may follow an upper respiratory tract infection. Some have suggested a viral etiology; potentially related to Parvovirus B19 and/or herpes simplex virus 6 infections. Others have proposed a post-traumatic etiology with subsequent development of chemical synovitis.
Radiographic features
Plain radiograph
Features are nonspecific although in some cases there may be an increase in medial joint space in the affected hip 5. Hip radiography within 6 months (classically after 4 weeks) to exclude Legg-Calvé-Perthes (LCP) disease is recommended 12.
Ultrasound
Ultrasound is useful for demonstrating a joint effusion which is often seen in the anterior recess. Herniation of the synovial membrane through a joint capsular defect (pseudodiverticulum) between the iliopsoas muscle and the anterior border of the joint capsule may be seen in a very small proportion of patients (~2%) 1.
Findings: There is mild anechoic effusion in the anterior recess of the affected right hip joint. There is no erosion of the cortex. Femoral vessels were patent. Anterior thigh muscles showed a normal echo pattern.
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