Limp

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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.

image image

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

image

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.

image 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.

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

image Computed tomography (CT) enables visualization of soft tissue as well as bone (tarsal coalition is one disorder that has been better characterized since the advent of CT).

image Magnetic resonance imaging (MRI) can distinguish living from dead bone, which is helpful in studying conditions such as Legg-Calvé-Perthes disease or avascular necrosis, and provides excellent images of the central nervous system, including spinal cord pathology. MRI also has a growing role in the evaluation of infectious processes (see Fig. 19-1).

EMedicine. Herman M: Pediatrics, limp:www.emedicine.com/emerg/topic387.htm

10 A 4-year-old girl presents with limping secondary to knee pain, fever, and a rash. Match the following rashes to the underlying disease.

1. Purpuric rash primarily on the lower extremities A. Lyme disease
2. Salmon-pink evanescent diffuse maculopapular rash B. Erythema multiforme
3. Multiple large oval papules, some with central clearing C. Henoch-Schönlein purpura
4. Symmetric papulovesicular rash with target lesions D. Systemic juvenile idiopathic arthritis

Answers:

1 C

2 D

3 A

4 B

11 What is the best test for diagnosing juvenile idiopathic arthritis (previously called juvenile rheumatoid arthritis [JIA]) in a child with chronic limp and joint pains?

No laboratory test is diagnostic of JIA. The diagnosis is made clinically on the basis of unexplained, persistent arthritis in one or more joints for more than 6 weeks in a child under the age of 16. The disease is subclassified into systemic arthritis, oligoarthritis (≤4 joints), or polyarthritis (>4 joints), enthesitis-related arthritis, and psoriatic arthritis.

12 In a limping child with lower-extremity joint pains who meets the clinical criteria for oligoarthritic JIA, which is a more useful serologic test: rheumatoid factor or antinuclear antibody?

Tests for rheumatoid factor almost never have positive results in patients with oligoarthritic JIA, and will be positive in fewer than half of patients with polyarthritic JIA. On the other hand, antinuclear antibody test results are positive in about 50% of patients with oligoarthritic disease, and it serves as an important marker for increased risk of iridocyclitis.

13 What is osteochondritis dissecans? What part of the body is most commonly involved?

In osteochondritis dissecans, a portion of articular cartilage and underlying subchondral bone gradually separates from the surrounding tissue. The cause is unknown. The knee, specifically the lateral aspect of the medial femoral condyle or the posterior aspect of the lateral femoral condyle, is the most commonly involved site. The clinical picture is one of intermittent pain that worsens with activity; clicking or locking may also be described. Radiographs may show a delineated, dense fragment of subchondral bone separated from the rest of the affected bone by a radiolucent crescent line. The tunnel view should be added to the anteroposterior/lateral films if this pathology is suspected. The talus, elbow, and rarely the patella can also be affected.

14 A 2-year-old child presents with refusal to walk after jumping off of a toy box. He is tender over the distal portion of his left tibia. Plain radiographs of the lower leg are negative. What is the most likely explanation for his pain?

The most likely reason for his pain is a nondisplaced spiral (single helix) fracture of the tibia, also known as a toddler’s fracture. This type of fracture may be seen in children from the age of walking up to 5 or 6 years. Although radiographically subtle, the fracture is usually seen on the anteroposterior (AP) view, rarely on the lateral. Additional views, particularly the internal oblique, may demonstrate the fracture if it is not apparent on the AP view. Even with normal radiographs, if clinical suspicion is high, presumptive treatment with follow-up films in 10–14 days is indicated. In the absence of trauma, if occult osteomyelitis is included in the differential diagnosis, bone scintigraphy can distinguish between the two entities.

15 An oblique view of the tibia in the previously described case reveals a subtle spiral fracture. The resident wants to consult child protective services given the spiral fracture with minimal trauma. What do you recommend?

Unlike spiral fractures of other long bones, even with a history of minor or unobserved trauma, toddler’s fractures in an ambulatory child generally do not indicate abuse, and a report is not warranted. Conversely, transverse or metaphyseal fractures of the tibia are concerning for the possibility of inflicted trauma.

KEY POINTS: LIMP

1 Look beyond the leg, laboratory values, and x-rays when evaluating the limping child.

2 SCFE is an orthopedic emergency (and may present with referred knee or thigh pain).

3 Limp may be the acute presentation of a more chronic problem, abdominal or back pathology, or even systemic illness. Open physis? Think fracture before sprain.

4 Normal laboratory studies do not exclude the possibility of septic joint or osteomyelitis.

16 What new radiologic technology may improve the accuracy of diagnosis of a toddler’s fracture?

Digital radiography. A recent study showed that the ability to manipulate images digitally increased the accuracy of both pediatric radiologists and pediatric emergency medicine physicians in the correct diagnosis of a toddler’s fracture, potentially saving the patients with the initially missed diagnosis an average of $800 each on further studies.

Fahr MJ, James LP, Beck JR, et al: Digital radiography in the diagnosis of toddler’s fracture. South Med J 96:234–239, 2003.

17 A 10-year-old girl presents with limping and pain over the lateral malleolus after twisting her ankle while playing basketball. She is able to bear weight. Plain radiographs of the ankle are negative. Which is a more appropriate management plan: elastic bandage wrap, ankle-strengthening exercises, and family doctor follow-up; or plaster splint, rest, and orthopedic follow-up?

The latter option is more appropriate in a child with open physes. The most likely site of pathology in this case is a Salter-Harris type I fracture of the distal fibula, not a sprained ligament.

18 A 14-year-old boy presents with limp after twisting his ankle. In performing a complete ankle examination, you include palpation of the lateral aspect of the foot. Why?

Because the peroneus brevis tendon inserts at the proximal end of the fifth metatarsal, a twisting mechanism may result in an avulsion fracture of this bone, known as a Jones fracture.

19 A 16-year-old female competitive long-distance runner reports insidious but progressive lower-left leg pain and limp over several weeks. After a negative plain film and persistent symptoms, MRI is performed, leading to a diagnosis of stress fracture of the tibia. Why is a detailed nutritional and gynecologic history of particular importance in evaluating this patient?

She may have a manifestation of the female athlete triad, which includes amenorrhea (or menstrual irregularity), disordered eating, and osteoporosis. Risk of stress fractures in these young female athletes is increased for multiple reasons. Concern for and treatment of this diagnosis would require a multidisciplinary approach that may not have been pursued without the appropriate history.

Brunet II M: Female athlete triad. Clin Sports Med 24:623–636, 2005.

Pepper M, Akuthota V, McCarty EC: The pathophysiology of stress fractures. Clin Sports Med 25:1–16, 2006.

20 A school-aged or young adolescent child presents with a chronically painful flat foot. Radiographs in the past have not been helpful. What condition would you suspect, and what imaging study would be most useful in detecting it?

Tarsal coalition. A coalition is a congenital fibrous band between the talus and calcaneus bones, or occasionally between the calcaneus and the navicular bone. Coronal CT images obtained through the posterior foot will show narrowing of the subtalar joint, sclerosis, or complete absence of joint space. “Beaking” of the talus on plain films is a clue to this condition.

21 A 15-year-old boy has been waking up with leg pain for two weeks. Initially his symptoms were attributed to “growing pains” and were treated very successfully with aspirin, but his mother is concerned about the duration of the symptoms. What are you concerned about?

Osteoid osteoma, the third most common benign bone tumor (after nonossifying fibroma and osteochondroma), usually presents with pain that is worse at night. The pain is dramatically relieved by salicylates, but not typically by nonsteroidal anti-inflammatory drugs. The femur or tibia is the site of 50% of these lesions, and a limp is present in more than half of those children. Classically, radiographs demonstrate a small radiolucent nidus that is smooth, regular, round or oval, and well defined, surrounded by dense sclerosis extending away from the margin with a fading edge. When the tumor is located in the proximal femur or posterior element of a vertebra, it can be particularly difficult to diagnose with plain films, in which case bone scintigraphy could support the diagnosis.

22 Match the following potential causes of limp with the location of pain.

1. Sever’s disease A. Patella
2. Sinding-Larsen-Johansson syndrome B. Calcaneus
3. Osgood-Schlatter disease C. Tibia
4. Kohler’s disease D. Metatarsal
5. Freiberg’s disease E. Navicular

These osteochondroses are a group of lesions that occur in the lower extremity in growing bones, with a clinical picture of localized pain and limp. They are presumed to be related to repetitive stress. Radiographic changes include irregularity, increase in density, or decrease in size of the affected bone.

Answers:

1 B. Sever’s disease: Insertion of the Achilles tendon on the calcaneus

2 A. Sinding-Larsen-Johansson syndrome: The attachment of the patellar tendon to the inferior patellar pole

3 C. Osgood-Schlatter disease: Insertion of the patellar tendon on the proximal tibial tuberosity

4 E. Kohler’s disease: The tarsal navicular

5 D. Freiberg’s disease: Usually the second metatarsal head, less often in the third and fourth

23 Which of the following conditions is not associated with limping: appendicitis, discitis, gingivitis, salpingitis, pharyngitis?

The etiology of limp may be linked to pathology outside of the lower extremities. Inflammation in the lower abdomen or pelvis (appendicitis, salpingitis) may result in a “shuffling” gait (walking with increased hip flexion). Discitis is a subacute inflammation of the intervertebral discs, usually of the lumbar spine, which presents with progressive limp, and eventually refusal to sit or walk over a period of a few weeks. It is most common in children under the age of 5. Pharyngitis caused by group A streptococcal infection may in rare instances lead to arthralgia or arthritis in the recovery period. Though gingivitis has been implicated in problems ranging from miscarriage to heart disease, it doesn’t cause limping.

24 A 6-year-old boy presents with a 3-day history of diarrhea and a new limp. What pathogen would you expect to find in his stool?

Salmonella enteritis and Yersinia infection may cause joint symptoms.

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