Limp

Published on 24/03/2015 by admin

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CHAPTER 19 Limp

Susanne Kost, MD, Bambi Taylor, MD

1 What is the most common cause of a nontraumatic acute limp in children?

Transient synovitis, formerly known as toxic synovitis, is the most common nontraumatic cause of limp in children. Transient synovitis is believed to be a postinfectious reactive arthritis, occurring most commonly in the hip, but occasionally in the knee or ankle. It is usually preceded by a viral respiratory or gastrointestinal illness.

2 What is the typical clinical presentation of transient synovitis?

The classic patient with transient synovitis is a white boy (male–female ratio, 2:1) between 3 and 10 years old (incidence peaks at age 6) with a 1- to 2-day history of limp, reporting unilateral pain in the hip, thigh, or knee. His past medical history will include viral symptoms within the past 1–2 weeks in over half the cases. He will have little or no fever and will appear well. His examination will be remarkable for a painful hip on passive range of motion, and he will prefer to hold the hip abducted and externally rotated. Transient synovitis typically causes a lesser degree of pain and limitation of motion than septic arthritis.

3 Can laboratory tests or imaging studies distinguish transient synovitis from septic arthritis of the hip?

Not always. White blood cell (WBC) counts are normal (<15,000 cells/mL) in the majority of patients with both conditions. Erythrocyte sedimentation rate (ESR) is elevated (<20 mm/h) in most patients with septic arthritis and about half of patients with transient synovitis. Fluid in the joint space on plain radiographs and ultrasound is common in both conditions. The combination of fever, non–weight-bearing, ESR > 40 mm/h, and serum WBC count > 12,000 cells/mL has a high positive predictive value for the diagnosis of septic arthritis; however, this clinical decision rule lacks consistency across institutions. When the clinician is highly suspicious of a septic joint, the definitive test is arthrocentesis.

Kocher MS, Mandiga R, Zurakowski D, et al: Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. J Bone Joint Surg 86A:1629–1635, 2004.

Luhmann SJ, Jones A, Schootman M, et al: Differentiation between septic arthritis and transient synovitis of the hip in children with clinical prediction algorithms. J Bone Joint Surg 86A:956–962, 2004.

4 Which is a better test for diagnosis and monitoring of bone and joint infections in children: C-reactive protein (CRP) or ESR?

CRP is more likely to be elevated at the time of presentation, peaks more quickly, and returns to normal more quickly in patients with a treated infection (within 7 days as compared to 2–3 weeks for ESR). In comparison to ESR, CRP is a better independent predictor of disease. It is a better negative predictor than a positive predictor of disease. Indeed, if the CRP is <1.0 mg/dL, the probability that the patient does not have septic arthritis is 87%.

Levine MJ, McGuire KJ, McGowan KL, et al: Assessment of test characteristics of C-reactive protein for septic arthritis in children. J Pediatr Orthop 23:373, 2003.

5 Describe the common presentations of the following hip pathologies of children: developmental dysplasia of the hip, Legg-Calvé-Perthes disease, and slipped capital femoral epiphysis (SCFE).

See Figure 19-1A and B. See Table 19-1.

Figure 19-1 A. Aseptic necrosis of the femoral head (right hip) in Legg-Calvé-Perthes disease. B. Slipped capital femoral epiphysis, more prominent on the left hip (“ice cream slipping off the cone”).

TABLE 19-1 COMMON PRESENTATIONS OF HIP DISORDERS IN CHILDREN

6 What is the likelihood of the above-hip pathologies affecting both hips?

Developmental dysplasia of the hip is bilateral in about 20% of cases, Legg-Calvé-Perthes disease in about 20%, and SCFE in 25–80%.

7 Which endocrinopathy is associated with SCFE?

SCFE has been associated most commonly with hypothyroidism, and more rarely with acromegaly, excess growth hormone, hypopituitarism, and hypogonadism. Hypothyroidism is especially important to consider if the SCFE occurs in a patient under the age of 10.

8 What is the best test for distinguishing Legg-Calvé-Perthes disease (avascular necrosis of the hip) from transient synovitis?

Tincture of time. The typical duration of transient synovitis is 1–2 weeks; Legg-Calvé-Perthes disease is chronic, with a typical course of 18–24 months. Radiographs of the hips may be helpful later in the course of the disease. Changes, best seen in the frog-leg lateral position, begin with a small, dense epiphysis and widening of the medial joint space due to cartilage hypertrophy. Later, a subchondral fracture (crescent sign) or fragmentation may be seen. As the disease progresses, reossification and healing result in deformity of the proximal femur.

9 Describe the benefits of “special” medical imaging tests when compared to plain films in the evaluation of a limping child.

Bone scanning is useful in detecting early Legg-Calvé-Perthes disease, osteomyelitis, stress fractures, and osteoid osteomas. Scintigraphy is 84–100% sensitive and 70–96% specific for osteomyelitis.

Ultrasonography is helpful for diagnosing joint pathology, especially confirming the presence of an effusion and guiding aspiration.

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