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<< Limping: Evaluation, Diagnosis, and Management in the Pediatric ED

Differential Diagnosis

The differential diagnosis of limping is extensive. (See Table 1 ). There may also be some variations in the common diagnoses based on the age of the patient. (See Table 2). The following is a description of the various etiologies of limping in children.




Congenital

Hip dysplasia has previously been called “congenital hip dislocation.” The current accepted term of developmental dysplasia of the hip illustrates that the infant hip may be abnormally developed but not actually dislocated. The diagnosis is not always made in the nursery. It may not come to attention until the child becomes ambulatory, at which time a Trendelenburg gait may be noted. An ultrasound is used for diagnosis in early infancy, while plain films are more useful in the older child. Orthopedic referral is needed for further treatment.

Inflammatory/Rheumatologic

Numerous rheumatologic illnesses have arthritis as a significant symptom. Therefore, they can present with limping as the primary complaint. Initially, it may be difficult to make the diagnosis, particularly if only one joint is involved. In these cases, it may be confused with a septic arthritis. Other systemic signs and symptoms, and chronicity of the arthritis may help make the correct diagnosis. For instance, an associated rash, eye abnormalities, recurrent fever, or other joint pain in the past may lead the physician toward a diagnosis of JRA. Psoriasis and inflammatory bowel disease may have arthritis associated with their other findings. Ironically, the arthritis can precede the skin changes in psoriatic arthritis. HSP may also present with joint pain and limping before the typical purpuric rash in 15% of the cases.22 Historical and examination findings with HSP include abdominal pain, palpable purpura (usually localized to the lower extremities and buttocks), joint pain, hematuria, hematochezia, hematemesis, headaches, and peripheral edema. Approximately 40% of patients may have had a preceding illness such as an upper respiratory tract infection.23, 24

Infectious

Many infectious diseases include a component of arthritis or arthralgias either as an acute finding, or as a post-infectious or reactive arthritis. These include post-streptococcal arthritis, as well as viral illnesses such as hepatitis and Coxsackie virus.

A more serious bone and joint infection can be easily missed and result in permanent sequelae if the diagnosis is delayed. Findings include swelling, erythema, and tenderness near the area of infection. Osteomyelitis in the pediatric population is commonly spread hematogenously. Staphylococcus aureus and Streptococcus pyogenes (group A beta-hemolytic streptococcus) constitute the major pathogens. In some circumstances, other pathogens need to be considered. Neonates are susceptible to group B Streptococcus and Escherichia coli, adolescents to Neisseria gonorrhea, and sickle cell patients to Salmonella.15-17,19-21 In addition to examining the involved extremity, a complete evaluation should include the spine and pelvis to rule out a diskitis or sacroiliac disease.

Transient synovitis may present in a similar manner to septic arthritis. It is a self-limited inflammation of the synovial lining, usually resolving within 3 to 10 days of the onset of symptoms. It is the most common cause of painful limp in childhood, accounting for up to 40% of non traumatic limps.14 Although the cause is unknown, it is hypothesized that transient synovitis is due to a post-infectious phenomenon. It often presents following a viral illness or upper respiratory infection.

Lyme disease, a tick-borne infection due to Borrelia burgdorferi, also includes arthritis as a characteristic feature. Lyme arthritis can be classified according to the number of joints involved and duration. Episodic arthritis involves 1 to 4 joints for a duration of <1 week with recurrence at least 2 weeks later. Acute and chronic pauciarticular arthritis involves 1 to 4 joints with chronic form lasting >4 weeks. The disease includes the typical expanding target lesion (erythema migrans), involvement of central and peripheral nervous systems, and migratory arthritis. Bilateral Bell’s Palsy can be seen with Lyme disease.

Traumatic

When a clear history of trauma precedes the limp, the diagnosis is often much easier to make. However, toddlers can present without a history for injury, or with a trauma or fall that is thought to be insignificant. Such a scenario is often found in children who have a fracture of the tibia, known as the toddler’s fracture. (Please see Figure 1.)



The toddler’s fracture is a spiral, oblique, non displaced fracture of the distal tibia, typically seen in children <3 years of age. Sometimes the fracture is only picked up on oblique views of the tibia, followup radiographs done weeks later, or by bone scan. Halsey et al found the most common symptoms of a toddler’s fracture to be point tenderness and refusal to bear weight. The sensitivity and specificity of point tenderness (59% and 53%, respectively) and refusal to bear weight (82% and 30%, respectively) were found to be poor.25 In the same study, patients with a presumptive diagnosis of toddler’s fracture were placed in a long leg cast or splint. However, 21 of the 59 patients did not have evidence of fracture even on follow-up x-rays. The final diagnosis in these patients is not known, and the inconvenience of taking care of a toddler in a long leg cast or splint is not discussed. Also, the question of what would have happened if these children were not splinted still remains unanswered.

Lower extremity fractures in non-ambulatory children should also raise suspicion for non-accidental trauma. Look for bucket handle fractures or corner fractures that are suggestive of child abuse. While spiral fractures are traditionally thought of as being suspicious for non-accidental trauma and are more likely to be investigated, they are not pathognomonic for abuse. Scherl et al found equal numbers of transverse and spiral femur fractures among cases with positive results of investigations for abuse.26 Mellick also found that isolated spiral tibial fractures are most commonly accidental.27 The history surrounding the event and other evidence of injury or neglect help determine whether child protective services investigation is warranted.

Toxic/metabolic


Toxic/metabolic causes include drugs, rickets, scurvy, and hyperparathyroidism. Surprisingly, some drugs can cause limb pain and present as limping. Vitamin A intoxication and carbamazepine have been implicated. Corticosteroids, ergotamine, phenothiazines and thiazides may cause muscle cramps. Hypercalcemia can cause bone pain. Rickets, the most common form of which in the U.S. is vitamin D deficient rickets, may also be associated with fractures and pain. Other metabolic diseases that affect the skeletal system include the mucopolysaccharidoses. All of these disorders usually involve some type of spinal deformity, with kyphosis being the most common.

Neoplasia

Neoplastic causes of limping include benign bone tumors (unicameral and aneurysmal bone cysts), malignant bone tumors (Ewing’s sarcoma, osteosarcoma), metastatic bone disease, and leukemia or lymphoma. Several case studies are reported with children presenting with limping and bony pain in which a subsequent diagnosis of a malignancy is made.28-31 Concurrent systemic signs and symptoms of fever, weight loss, lymphadenopathy, or hepatosplenomegaly should prompt further investigation with laboratory studies, particularly a CBC to evaluate cell lines, and radiographs as indicated by the examination.

Primary malignant bony tumors such as osteosarcoma or Ewing’s sarcoma commonly involve the long bones, and thus may be seen in the lower extremity. Growing children are affected most often, with the peak incidence occurring in the pre-teen and early teen years. Spinal tumors, such as sacrococcygeal teratoma or bony tumors of the axial skeleton may also cause lower extremity weakness, back pain, and limping.

Benign bone lesions such as osteochondromas and osteoid osteomas may be found in the limping child. Osteoid osteomas are a common benign bone tumor that may occur in the lower extremity or back, causing limping and pain. It is common in early adolescence, with pain characteristically worse at night, and relieved by NSAIDs. Radiographs usually confirm the diagnosis.

Degenerative

Degenerative causes of limping include avascular necrosis of the femoral head, LCPD. LCPD is caused by osteonecrosis of the proximal epiphysis of the femoral head. LCPD is most likely the result of repeated trauma to the hip in active boys which may impair the blood supply to this area. It is most commonly seen in children ages 4 to 10 years. Patients typically present with chronic limping. While it is classically known as a “painless limp,” there may be associated hip pain and referred pain to the ipsilateral knee or groin. Swelling and tenderness on examination are rare. Patients may also keep the hip externally rotated with limited abduction and internal rotation. Avascular necrosis of the femoral head has also been reported to be increased in children with renal failure. In one study, it was noted to occur in 1 out of 15 children with renal failure, which is a significantly higher rate than the general pediatric population.32 Children who are being treated with corticosteroids may be at a higher risk, although avascular necrosis has been noted to occur in the absence of steroid use.32 Patients with sickle cell disease may also be at increased risk for developing avascular necrosis of the femoral head. Laboratory tests are generally normal, and plain radiographs of the hips make the diagnosis once significant  necrosis has occurred.

Osgood Schlatter’s disease is characterized by pain over the tibial tuberosity. This disease is felt to be a result of repeated microtrauma to the insertion of the patellar tendon, similar to Sever’s disease, which is pain in the area of the insertion of the Achilles tendon to the calcaneus. It is more common in adolescent boys, and may be bilateral 25-50% of the time.33 The diagnosis is made based on the presence of tenderness to palpation over the tibial tuberosity. In addition, pain is exacerbated with repeated activity, particularly jumping or knee extension against resistance. Resolution occurs when the secondary ossification center fuses to the proximal tibia, which occurs with maturation. Treatment consists primarily of limiting activity, immobilization, and NSAIDs.

SCFE is a medial or posterior slipping of the femoral capital epiphysis. The typical patient with SCFE is an overweight adolescent male. Manoff et al studied the association between body mass index and SCFE. They retrospectively reviewed 106 subjects with radiographically confirmed SCFE to 46 normal controls. In the SCFE group, 81.1% had a body mass index greater than the 95th percentile, compared to 41.3% in the control group (p< 0.0001).34 However, it is also seen in tall, thin adolescents who have undergone a recent growth spurt, resulting in shearing stress on the weakened epiphysis. SCFE will often present with a painful limp, hip or groin pain, or referred knee pain. Knee pain was found to be the primary presenting symptom in 15% of the patients with SCFE.35 Physical examination finds the hip externally rotated with painful range of motion, especially internal rotation, abduction, and flexion. Plain radiographs are generally the initial step in the diagnosis. Up to 60% of patients may develop bilateral SCFE, with about 23% having bilateral slips at the time of initial presentation. 36 There is also an association of SCFE with endocrine abnormalities such as hypothyroidism, panhypopituitarism, and hypogonadism. Such abnormalities should be suspected and evaluated in a younger child with SCFE, short stature, and hypogonadism. These children are also more likely to have bilateral SCFE.37 Adelay in diagnosis of SCFE results in increased slip severity and potentially higher risk of long-term complications.35 Treatment involves emergent orthopedic consultation for internal fixation.

Osteochondritis dissecans is a disease in which a small island of bone dies and is then sloughed. Typically, the child complains of poorly localized knee pain. Osteochondritis dessicans commonly presents in the preteen or early adolescent period. Pain with full flexion is usually found. If there is a piece of sloughed bone, one may find an effusion. Locking of the knee can occur while in flexion. Typically involving the distal femur, osteochondritis dessicans can be easily identified on plain AP radiographs of the femur. Treatment includes immobilization, isometric exercises to retain quadriceps tone, and pain control. Arthroscopic surgery is indicated for continued pain. (Please see the May 2006 issue of Pediatric Emergency Medicine Practice of pain management.)

Neuromuscular

Neuromuscular conditions which cause weakness in the hip girdle, lower spine, or extremities can present as limping. These include muscular dystrophies, myelitis or myositis, neuropathies, demyelinating disorders, or disorders involving the neuromuscular junction. A thorough discussion of these disorders is beyond the scope of this review article.

Pre-Hospital Care
 
The role for pre-hospital care for non traumatic limping is limited. In cases of an obvious traumatic injury, the affected extremity should be immobilized and splinted in a position of comfort until further evaluation and management can be completed in the ED.