Problems of the Hip and Lower Extremity

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Transient Synovitis of the Hip

Transient synovitis of the hip (TSH), a self-limited unilateral disease of unknown etiology, is the most common disorder causing a limp in children. TSH is most common between the ages of 2 and 10 years (average 6 years) and occurs more frequently in boys. The condition often parallels or follows a viral upper respiratory infection and has been considered by some to represent a viral or perhaps "viral-immune response" disorder affecting the hip.18 The few biopsies reported for this benign, transitory disease have revealed only nonspecific inflammatory congestion and hypertrophy of the synovial membrane.

Children with TSH present with an ill-defined limp, hip or knee pain, and possibly a low-grade fever. The hip is often held flexed, abducted, and externally rotated to provide for maximum joint volume. A complete blood count may show mild leukocytosis without a left shift. The erythrocyte sedimentation rate (ESR) may be elevated, exceeding 20 mm/hour in nearly one third of patients.19 Radiographs may show capsular swelling characterized by increased distance between the medial acetabulum and the ossified part of the femoral head (Fig. 7.5). Ultrasound examination has been used increasingly as a diagnostic tool to detect hip disorders because of its high sensitivity for demonstrating effusion in the hip joint.

Hawkins Classification Talus Fracture

Fig. 7.5. Teardrop distance is the interval between the ossified part of the femoral head or neck and the acetabulum (arrowheads). The teardrop distance is a useful criterion for early diagnosis of Legg-Calve-Perthes disease and is also a good indicator of the presence of excess joint fluid caused by sepsis. In 96% of normal subjects the teardrop distance in both hips is the same or differs by only 1 mm or less.

Fig. 7.5. Teardrop distance is the interval between the ossified part of the femoral head or neck and the acetabulum (arrowheads). The teardrop distance is a useful criterion for early diagnosis of Legg-Calve-Perthes disease and is also a good indicator of the presence of excess joint fluid caused by sepsis. In 96% of normal subjects the teardrop distance in both hips is the same or differs by only 1 mm or less.

It may be difficult to differentiate TSH from early septic arthritis; and if clinical suspicion is high, the hip should be aspirated. Initial treatment is bed rest, usually at home, but occasionally hospitalization is required to perform studies needed to rule out sepsis and thus allay parental and physician concern.

Symptoms may last up to 7 to 10 days but rarely more than 2 weeks. Failure to resolve with rest should lead to a more extensive workup to exclude juvenile rheumatoid arthritis, sacroiliac joint infection, osteomyelitis of the ileum, and osteoid osteoma, each of which may mimic TSH. A few patients with TSH (1-3%) go on to develop Legg-Calve-Perthes disease within a year.20 Therefore, patients with TSH should have their hips examined once or twice during the year following acute presentation. Radiographs are unnecessary if hip motion is full.

Septic Hip

A septic hip is considered a medical emergency, as surgical drainage of pus soon after onset of symptoms prevents destruction of the femoral head and neck. Accumulating fluid and pus containing destructive enzymes rapidly elevate the intraarticular pressure and permanently injure vessels and articular cartilage. Microorganisms usually enter the hip joint by bacteremia, the result of distant infection

(skin or subcutaneous abscess, otitis media, pharyngitis, pneumonia, or umbilical infection). In neonates nosocomial infection may occur via catheters or venipuncture.

In neonates and infants, the early stages of septic hip may be mistaken for cellulitis, venous thrombosis, superficial abscess, and sciatic nerve palsy. Unilateral swelling of the thigh or leg may indicate a ruptured septic hip with extravasation of pus into the thigh fascial planes. Older children usually present as apprehensive, toxic, and experiencing constant hip pain. Typical septic arthritis of the hip in infants and children can be recognized without difficulty. The child is febrile with the thigh in a position of flexion, abduction, and external rotation. The pain is worse with any hip movement. A site of infection and portal of entry into the bloodstream such as skin abscess, otitis media, or pneumonia is usually present.

Laboratory testing may show an elevated complete blood count (CBC), ESR, and C-reactive protein. C-reactive protein rises within 6 to 8 hours, while the ESR may not rise for 24 to 48 hours. There is considerable overlap between TSH and septic arthritis. No combination of physical exam or laboratory findings is 100% sensitive or specific in diagnosing septic arthritis of the hip.19 Aspirating pus from the hip joint remains critical for diagnosis and early decompression. Blood cultures and cultures from other sites are obtained before initiating antibiotics (see Reference 51, Chapter 43). Staphylococcus and gram-negative organisms are commonly found in newborns. In children 1 to 18 months of age, Haemophilus influenzae is a frequent cause of septic hip. Salmonella can infect a hip in patients with sickle cell disease. Intravenous antibiotics should be started following needle aspiration and culture, but antibiotics alone cannot cure septic hip. Treatment must include surgical decompression.

Slipped Capital Femoral Epiphysis

Slipped capital femoral epiphysis (SCFE) is the most common serious disorder of the hip in adolescents. The peak age incidence is 11 years for girls and 14 years for boys; the incidence in the general population is approximately 2 per 100,000 with a male to female ratio of 2.5:1.0.21 SCFE is characterized by sudden or gradual medial displacement of the femoral neck from the capital femoral epiphysis. The epiphysis remains in the acetabulum, resulting in a retroversion deformity of the femoral neck. The goals of treatment for a patient with a SCFE are to stabilize the slip and prevent further displacement while avoiding the complications of avascular necrosis, chondrolysis, and early osteoarthritis.

The etiology is multifactorial and ill-defined. Classification of SCFE has been traditionally based on duration of symptoms. Slips have been divided into acute (symptoms <3 weeks), acute-on-chronic (symptoms of mild pain for >3 weeks with a recent sudden exacerbation), and chronic (symptoms >3 weeks).22 Newer classification schemes attempt to address the question of stability because unstable slips have a poorer prognosis.23,24

With an acute slip, mild symptoms are present for a short time before the displacement occurs; minimal trauma may then cause an acute separation, with pain so severe the child cannot bear weight on the affected side. Patients with the chronic form have hip pain localized to the groin, buttock, or lateral hip. Occasionally, the child has only knee pain. There is a decrease in abduction, flexion, and internal rotation, and as the hip is gently flexed it may roll into external rotation.

The clinical diagnosis of SCFE requires radiographic confirmation of femoral head displacement. Radiographic assessment must include both hips in anteroposterior (AP) and lateral views. Both hips are included because bilateral disease occurs in one third of cases.25 The earliest changes may be subtle, only showing widening or irregularity of the epiphyseal plate (Fig. 7.6). Since initial displacement occurs posteriorly, the true lateral or "frog" lateral views are most sensitive to detect early SCFE. On the AP view the Klein's line drawn along the superior femoral neck should intersect 20% of the lateral femoral head (Fig. 7.6). When the diagnosis is suspected from the clinical findings, but plain radiographs are not conclusive, magnetic resonance imaging (MRI) is the best study to demonstrate the subtle widening and irregularity of the physis and even early slippage of the femoral head.26

Surgery is the only reliable treatment for SCFE. Results are best if it is performed soon after diagnosis because outcomes depend on early stabilization. Any attempt to reduce a chronic slip produces avascular necrosis.

In children who have unilateral disease at diagnosis, nearly 20% may go on to develop bilateral disease. Most often sequential slips will occur within 18 months, although reports have documented cases that occur up to 5 years after initial diagnosis.25 Frequent follow-up examination is recommended until definite radiographic evidence of physeal closure is noted.

Developmental Dysplasia of the Hip

The term developmental dysplasia of the hip (DDH) describes a spectrum of disorders: frank dislocation, partial dislocation (subluxation),

Lower Limb Pain



Scfe Klein Line
Fig. 7.6. Left slipped capital femoral epiphysis. A line drawn along the superior aspect of the femoral neck (Klein's line) barely intersects with the femoral head compared to the normal right side, a sign of slipping of the left femoral head.

instability, and acetabular dysplasia. Because many of these findings are not present at birth, the term developmental dysplasia has replaced the older term congenital hip dislocation. The reported incidence of all forms of DDH is 2 to 6/1000 and is influenced by genetic and environmental factors. The etiology of DDH is multifactorial. The female to male ratio is 5:1. Hormonal factors play a role in joint laxity. Mechanical factors increasing the risk of DDH include oligohydram-nios, primigravida, and breech presentation. Intrauterine positioning may explain the 3:1 predominance of left hip involvement. One in five children with DDH has a positive family history.27,28

In the newborn, Barlow and Ortolani tests (Fig. 7.7) are the most reliable tests for diagnosis and should be part of every well-baby examination (see Reference 51, Chapter 17). The infant is examined relaxed and supine, with one of the examiner's hands stabilizing the pelvis. The other hand holds the hip to be examined with the thumb in the groin and the index or long finger over the greater trochanter. The hip is flexed to 90 degrees and adducted past the midline while a gentle outward force is made by the thumb. The hip may be felt to dislocate during adduction (positive Barlow sign). The hip is then abducted and gently lifted. Relocation of the dislocated femoral head may be felt (a pop is not heard), which is a positive Ortolani's

Teste Barlow
Fig. 7.7. Barlow and Ortolani tests.

reduction test. A positive test is felt as a "clunk." The high-pitched click that is often heard is normal and unrelated to DDH.

In the child over 2 to 3 months of age, muscle tightness may mask dislocation or reduction. Clinical signs are more subtle as the child approaches walking age, but the following abnormalities should always be sought during well-child examinations: an asymmetric hip abduction, one knee lower than the other (positive Galeazzi's sign), and asymmetric thigh creases. Unfortunately, these clinical examinations do not identify all neonates with DDH, in part because some cases are missed on initial examination and other children develop instability later. Standard radiographs are difficult to interpret until the femoral head begins to ossify at 3 to 6 months of age. During dynamic ultrasonography a modified Barlow maneuver is used for the hip evaluation, increasing the accuracy of diagnosing hip instability after 6 weeks of age.29,30

Neonatal hip instability or dislocation can be treated with a Pavlik-type harness (Fig. 7.8) with 85% to 90% success in infants up to 6 to 8 months of age.31,32 This harness holds the infant's hips in a flexed and abducted position, directing the femoral head into the developing acetabulum. Pavlik harness use requires close ultrasound or radiographic monitoring and frequent clinical follow-up. Most hips stabi-

Fig. 7.8. Pavlik harness on a newborn. The hips are fully flexed, then fall out passively into abduction.

Fig. 7.8. Pavlik harness on a newborn. The hips are fully flexed, then fall out passively into abduction.

lize after 2 to 3 months. Dislocated hips diagnosed at 6 to 18 months of age often require closed or open surgical reduction under anesthesia, followed by spica cast immobilization.

Legg-Calve-Perthes Disease

Legg-Calve-Perthes disease (LCPD) is avascular necrosis of the femoral head in otherwise clinically normal children. LCPD typically presents between 4 and 8 years of age, with the boy/girl ratio approximately 5:1. Bilateral involvement occurs in approximately 10%.20 Interesting parallels exist between LCPD and "constitutional delay of growth." Children with LCPD are often small for age, and thin, with bone age that is delayed by 1 to 2 years. Recent studies have proposed a link with familial thrombotic disorders, such as the factor V Leiden mutation.33 Age at onset is an important indicator of outcome; children under 6 years of age often do well without specific treatment, whereas children over 9 years have a worse prognosis.20

Catterall34 has classified LCPD according to radiographic findings of the percent of the femoral head that is avascular. The ultimate Catterall classification may not be determined for 6 to 9 months after the initial onset.35 The history and physical findings can vary markedly depending on the stage of the disease process. During the early stages, the history is most often that of a limp or increasing groin, thigh, or knee pain. The physical findings at this time are similar to those of a child with an "irritable hip"; the initial synovitis may cause a decrease in range of motion on internal and external rotation, and there may be muscle atrophy of the thigh or calf consistent with an antalgic gait. With later, more severe stages of LCPD, there may be contractures of the adductor and hip flexor musculature in addition to restricted internal and external rotation.

Techniques for diagnosing LCPD and determining its prognosis include radiography, technetium scanning, MRI, arthrography, and CT scans. They are all equally useful, and each has advantages and disadvantages. Laboratory evaluation is normal.

LCPD is a self-healing disorder and there is no evidence that any treatment speeds the return of blood flow to the femoral head.20 The main treatment objectives are to relieve muscle spasm, regain range of motion, and contain the femoral epiphysis within the acetabulum to minimize deformation of the femoral head. Orthopedic consultation is recommended. Nonsurgical treatment includes the use of a spica cast, removable orthosis, and braces. Surgical options for more severe disease include soft tissue procedures to release the adductors and bony procedures to mechanically realign the hip.36 Long-term outcomes are good for most children, although approximately 10% to 15% develop deteriorating symptoms and degenerative arthritis that may require hip arthroplasty.37 Most patients with LCPD can participate in sports.

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