Khập khiễng: Đánh giá và chẩn đoán potx

Vol 9, No 2, March/April 2001 89 A limp is a common reason for a child to present to the orthopaedist, often after first being seen by a primary- care physician or in an emergency department. Most parents are keen observers; they are quick to detect even subtle gait abnormalities and generally will not wait long to have a limp evaluated. The orthopaedist is expected to recognize the gait abnormality, determine the proba- ble site of origin, and then develop a good working diagnosis before ordering selective diagnostic tests. These tests should provide the data for confirming the diagnosis and developing a treatment plan while decreasing costs to the health-care system, as well as minimizing pain and anxiety for the child and parent. Pain, weakness, and mechanical factors are the primary causes of limp in children. The etiology of a limp ranges from benign, self-limited conditions that call for only a diag- nosis and reassurance (e.g., tran- sient synovitis) to conditions in which early diagnosis may be life- saving (e.g., acute leukemia). 1 The long differential diagnosis (Tables 1 and 2) may seem daunting, particu- larly when the site of origin is un- known. However, after obtaining a thorough history and performing a careful physical examination, the site of origin can often be localized and the differential diagnosis narrowed, thus permitting a well-organized approach to obtaining additional data with selective diagnostic tests. Appropriate treatment can then be instituted. Normal Gait Normal gait is a smooth, rhythmic, mechanical process that advances the center of gravity with a mini- mum expenditure of energy. Many aspects of gait change with age. 2 When children begin to walk (typi- cally between 12 and 16 months of age), they have a short stride length, a relatively fast cadence and slow velocity, and a widened base of support in double stance. Their hips, knees, and ankles move through a small arc of motion. 2 Until 30 to 36 months of age, chil- dren have neither the balance nor the abductor strength to maintain single-limb stance for very long. By 7 years of age, children exhibit a mature gait. 2 The mature gait cycle is com- posed of the stance phase (initial contact, loading response, mid- stance, terminal stance, preswing) and the swing phase, during which the limb is advanced in space to position the foot for the next heel- strike. The abductors stabilize the pelvis during stance phase, pre- venting significant side-to-side motion as the opposite limb swings Dr. Flynn is Assistant Professor of Orthopaedic Surgery, Unviersity of Pennsylvania School of Medicine, Philadelphia; and Attending Surgeon, Division of Orthopaedic Surgery, Children’s Hospital of Philadelphia. Dr. Widmann is Assistant Professor of Orthopaedic Surgery, Weill Medical College of Cornell University, New York, NY; and Assistant Attending Surgeon, Hospital for Special Surgery, New York. Reprint requests: Dr. Flynn, Division of Orthopaedic Surgery, Children’s Hospital of Philadelphia, 34th and Civic Center Blvd, Philadelphia, PA 19104-4399. Copyright 2001 by the American Academy of Orthopaedic Surgeons. Abstract A limp is a common reason for a child to present to the orthopaedist. Because of the long list of potential diagnoses, some of which demand urgent treatment, an organized approach to evaluation is required. With an understanding of normal and abnormal gait, a directed history and physical examination, and the devel- opment of a differential diagnosis based on the type of limp, the patient’s age, and the anatomic site that is most likely affected, the orthopaedist can take a selective approach to diagnostic testing. Laboratory tests are indicated when infection, inflammatory arthritis, or a malignant condition is in the differential diagnosis. The C-reactive protein assay is the most sensitive early test for mus- culoskeletal infections; an abnormal value rapidly returns to normal with effec- tive treatment. Imaging should begin with plain radiography. Ultra- sonography is particularly valuable in assessing the irritable hip and guiding aspiration, if necessary. J Am Acad Orthop Surg 2001;9:89-98 The Limping Child: Evaluation and Diagnosis John M. Flynn, MD, and Roger F. Widmann, MD through. During normal walking motion, one foot is always on the ground. The kinematics of normal gait has been studied in detail, 2,3 establishing normal ranges of joint motion during different phases of the gait cycle. The ankle dorsiflexes at heel-strike, then plantar-flexes to foot-flat, and then dorsiflexes again as the tibia moves forward. The knee is flexed at heel-strike, extends until toe-off, and then flexes during swing, allowing clearance of the foot as it positions for the next heel- strike. The hip follows a similar pattern, with slight flexion at heel- strike, extension through stance, and then flexion in swing. Abnormal Gait Normal gait can be altered by pain, a mechanical problem, or a neuro- muscular problem. A child will adopt an antalgic gait in an effort to prevent pain in the affected limb. The single-limb-support phase of stance is shortened on the painful extremity, as is the stride length of the normal opposite limb (to get back to bearing weight on the well leg as quickly as possible). A vari- ant of the classic antalgic gait is the “cautious” gait of a child with back pain. 4 For example, a child with diskitis will lose the normal rhyth- mic flexion and extension of the lumbar spine, as demonstrated when bending to pick up objects off the floor. 5 Another variant of the antalgic gait is the complete refusal to walk. This pattern is seen most often in toddlers and may indicate a condition causing pain that can- not be avoided by any of the possi- ble gait alterations. Circumduction—excessive hip abduction, pelvic rotation, and hik- ing—functionally shortens a limb, thus enhancing foot clearance dur- ing swing when there is joint stiff- ness, particularly in the ankle. 6 Children with a significant limb- length inequality may “vault” with the short leg (or toe-walk) to clear The Limping Child Journal of the American Academy of Orthopaedic Surgeons 90 Table 1 Differential Diagnosis of Antalgic Gait <4 yr 4 to 10 yr >10 yr Toddler’s fracture (tibia or foot) Fracture (especially physeal) Stress fracture (femur, tibia, foot, pars Osteomyelitis, septic arthritis, Osteomyelitis, septic arthritis, diskitis intra-articularis) diskitis Legg-Calvé-Perthes disease Osteomyelitis, septic arthritis, diskitis Arthritis (juvenile rheumatoid Transient synovitis Slipped capital femoral epiphysis arthritis, Lyme disease) Osteochondritis dissecans (knee or ankle) Osgood-Schlatter disease or Sindig- Discoid lateral meniscus Discoid lateral meniscus Larsen-Johanssen syndrome Foreign body in the foot Sever’s apophysitis Osteochondritis dissecans (knee or Benign or malignant tumor Accessory tarsal navicular ankle) Foreign body in the foot Chondromalacia patellae Arthritis (juvenile rheumatoid arthritis, Arthritis (Lyme disease, gonococcal) Lyme disease) Accessory tarsal navicular Benign or malignant tumor Tarsal coalition Benign or malignant tumor Table 2 Differential Diagnosis of a Nonantalgic Limp Circumduction Gait/ Equinus Gait (Toe-Walking) Trendelenburg Gait Vaulting Gait Steppage Gait Idiopathic tight Achilles tendon Legg-Calvé-Perthes disease Limb-length discrepancy Cerebral palsy Clubfoot (residual or untreated) Developmental dysplasia of the hip Cerebral palsy Myelodysplasia Cerebral palsy Slipped capital femoral epiphysis Any cause of ankle or Charcot-Marie-Tooth Limb-length discrepancy Muscular dystrophy knee stiffness disease Hemiplegic cerebral palsy Friedreich’s ataxia the long leg, rather than circumduct it. An equinus gait (toe-walking) occurs when ankle dorsiflexion is limited. This may result from gas- trocnemius-soleus spasticity, short- ening of the Achilles tendon, or both. Thus, stance phase will be initiated with toe-strike rather than heel-strike. Several abnormal gait patterns result from muscle weakness or a neurologic abnormality. A Trendel- enburg gait results from altered hip mechanics, particularly abduc- tor weakness. During stance on the involved side, the contralateral side of the pelvis drops. To preserve balance, the child may lean the trunk toward the affected side. A variation of the Trendelenburg gait is the waddling gait of a child with bilateral hip dislocation. A “step- page gait” develops when the ankle dorsiflexors are weak (e.g., as in Charcot-Marie-Tooth disease). To compensate for the weakness, the child increases knee flexion in the swing phase to clear the foot. The foot will slap to the ground because the ankle dorsiflexors are unable to decelerate the foot between heel- strike and foot-flat. An unsteady gait may result from conditions that affect balance, such as Friedreich’s ataxia. Careful initial analysis of the gait can enhance the specificity of the remainder of the physical examination and facilitate localiza- tion of the origin of the limp. History An accurate history may be difficult to obtain from a young child, and some or all of the history must be ob- tained from the parents or primary caregivers. A brief discussion with the child, followed by a parental description of pain complaints and changes in gait pattern, is invalu- able in guiding the subsequent physician-directed evaluation. In certain circumstances, adolescents and some children should be ques- tioned privately, as they may pro- vide important details regarding exposure to sexually transmitted diseases, such as gonococcal infec- tion, which may not be obtained in the presence of parents. 7 Once the parent and patient have had an opportunity to describe the pain and/or limp in their own terms, the physician is best prepared to com- plete the history. The history should focus on the character of the limp: the presence or absence of pain or other localiz- ing symptoms, the frequency and duration of symptoms, and the mechanism of injury, when appro- priate. A history of ceasing athletic participation or social play with friends should raise concern. 4 The absence of pain suggests either neu- romuscular or metabolic disease or a congenital or developmental ab- normality, such as hip dysplasia or limb-length discrepancy. In a tod- dler, the absence of pain complaints may not be particularly helpful, and the physical examination takes on greater importance. The pattern, onset, and duration of pain may suggest the origin. 4 Acute onset of severe pain over a few days focuses the evaluation on trauma, infection, or malignancy, whereas gradual worsening over months suggests inflammatory or mechanical symptoms. 8 It is helpful to characterize the quality of the pain as constant, intermittent, or transient. Constant pain is of partic- ular concern, suggesting an intra- medullary process, such as expand- ing tumor or infection. A history of trauma is readily established in most circumstances, with some notable exceptions: pathologic fracture and child abuse. It is important to characterize the timing of pain (e.g., morning pain, pain after activity, or pain that wakes the child from sleep). Morning pain or pain and stiffness after inactivity are more characteristic of inflamma- tory joint disorders. 8 Pain after activ- ity may suggest an overuse injury, such as a stress fracture, or an inter- nal articular derangement, such as an osteochondral lesion, a meniscal tear, or an anterior cruciate ligament tear. Night pain that wakes a child from sleep may represent benign “growing pains,” but the concern is that it may derive from osteoid oste- oma or a malignant condition. Pain relief with nonsteroidal anti- inflammatory medications may be characteristic of osteoid osteoma but is not diagnostic. Referred pain must also be considered, particularly thigh or medial knee pain referred from painful conditions of the hip (e.g., slipped capital femoral epiphysis). Buttock or lateral thigh pain may be referred from the back. Pain in multi- ple joints suggests an arthritic process. A past medical history including recent trauma or exposure to infec- tious diseases and use of antibiotics is helpful in diagnosis. Recent vari- cella infection may lower systemic immunity, rendering the child sus- ceptible to opportunistic bone or joint infections. 9 Failure to achieve appropriate developmental mile- stones or, more ominously, deterio- ration of motor ability warrants fur- ther neuromuscular or metabolic evaluation. The review of systems should seek a history of recent fever, weight loss, or malaise suggestive of infection or malignancy. A history of prior medical evaluation for the same problem should be sought, and the pertinent records should be ob- tained when possible. A complete history should include questioning about the family history of neuro- muscular disease, metabolic disease, inflammatory arthritis, or infectious disease exposure. Physical Examination The physical examination of the limping child has three essential components: the gait exam, the John M. Flynn, MD, and Roger F. Widmann, MD Vol 9, No 2, March/April 2001 91 standing/floor exam, and the table- top exam. The child should be dressed in as little clothing as is prac- tical; gym shorts and bare feet are ideal. Much can be missed watching a small child walk in an oversized gown that extends to the floor. Gait Examination The examination area should offer sufficient space to see multiple gait cycles. It is important not to be fooled by an artificial “doctor walk”; the best chance to see the true limp is by observing gait when the child does not know she is being watched, such as when the child is walking to the examination room. 10 Running may accentuate the limp or abnor- mal gait. Subtle weakness or the upper-extremity posturing of cere- bral palsy might not be seen until the child runs. Shoes may provide valuable clues to gait problems; for example, a child having trouble clearing his foot in swing phase may have excessive toe wear. It is best to adopt a systematic approach to the gait examination, working from the ground up and watching each limb segment and joint through several gait cycles. Trying to simultaneously analyze every facet of gait is difficult for even the most experienced clinician, considering that a typical toddler takes 180 steps per minute. Note how the foot strikes the floor—is there heel-strike, foot-flat, or toe- strike? A child may walk on the medial or lateral border of the foot to protect a sore bone or the site of a puncture wound or foreign body. Abnormal limb rotation may be observed. Metatarsus adductus, internal tibial torsion, or femoral anteversion will result in an internal foot-progression angle. An adoles- cent with a slipped capital femoral epiphysis or a young child with an occult fracture may walk with an external foot-progression angle. The next feature to consider is the symmetry of the stance phase. A unilateral shortened stance phase is characteristic of an antalgic gait. The range of motion of each joint should also be evaluated. Limited ankle dorsiflexion is seen in chil- dren with a short Achilles tendon or a spastic gastrocnemius-soleus. At the knee, motion should be ob- served through several gait cycles. Contracture or spasticity in the quadriceps or hamstrings or intra- articular derangement will limit knee motion. Any frontal-plane ab- normalities should be noted as well (e.g., a varus thrust of the proximal tibia in Blount’s disease). Hip mo- tion may be abnormal, exhibiting circumduction, persistent flexion, or excessive pelvic or trunk motion. Upper-extremity posturing as well as difficulty with balance and coor- dination may suggest a neurovas- cular origin of the limp. Standing/Floor Examination After the history and vital signs have been taken and the physician has thoroughly studied the child’s gait, there are several tests to con- sider before the tabletop examina- tion. The spine should be examined with the child standing, taking care to note balance in the coronal and sagittal planes, scoliosis, lumbo- sacral step-off, pelvic obliquity, and any cutaneous findings (e.g., café- au-lait spots, hairy patches, or sacral dimples). On the forward bend, the examiner should note a thoracic or lumbar prominence due to scoliosis. The Trendelenburg test is per- formed by having the child stand on the affected leg with the knee flexed and the hip extended. The child may need to rest his hands against the wall for balance. If the Trendelenburg test is performed with hip flexion, the hip flexors can elevate the pelvis and mask a mild deficiency of the gluteus medius. 4 It may take 20 seconds or more of continuous testing on the affected limb before abductor weakness causes the opposite pelvis to drop. If muscular dystrophy is a possi- bility, a Gower test is performed by having the child sit on the floor and then rise quickly, observing to see if he uses his hands to substitute for weak hip extensor muscles. Repeti- tive single-leg heel raises and toe raises can be utilized to accentuate subtle weakness in the foot plantar- flexors or dorsiflexors. Tabletop Examination With the child on the examining table, one should thoroughly in- spect for asymmetry, deformity, erythema, rashes, and swelling. Puncture wounds or foreign bodies should be sought on the plantar surface of the foot in walkers and on the anterior aspect of the knee in crawlers. The resting position of the limb should be noted; for exam- ple, a child with septic arthritis of the hip will hold the hip flexed and externally rotated. Note also any muscle hypertrophy (e.g., calf hy- pertrophy in muscular dystrophy) or atrophy (e.g., global unilateral atrophy in hemiplegia or quadri- ceps atrophy in a child with a pain- ful hip or knee). Palpation of the lower extremity to find the point of maximum ten- derness is often the most valuable part of the physical examination of a limping child. Knowing the exact site of pain dramatically limits the differential diagnosis and may elim- inate the need for a bone scan or other diagnostic test (Fig. 1). Every joint of the lower extremity should be taken through its range of mo- tion, noting pain, contractures, or muscle spasticity. The patellofemo- ral joint, a common source of pain in adolescents, should be tested for signs of apprehension or pain with patellar compression during flexion and extension. The sacroiliac joint is tested by direct percussion posteri- orly and by stressing the joint with the hip positioned in flexion, abduc- tion, and external rotation (FABER test). The rotational profile should The Limping Child Journal of the American Academy of Orthopaedic Surgeons 92 be documented in children with in- toeing or out-toeing. 11 Appropriate neurologic testing should also be performed. Limb lengths should be assessed. If an inequality is noted, the differ- ence is most accurately determined by leveling the pelvis with blocks under the short leg. Although a sig- nificant limb-length inequality may itself alter gait, it also suggests other potential causes of limping, such as hemiplegia and developmental dis- location of the hip. Radiographic Evaluation Although the various imaging modalities may each have a role in the assessment of the child with a limp, plain radiography should always be performed first, because radiographs are inexpensive, can be easily obtained at any hour, and are both sensitive and specific for a wide variety of disorders. 12 In chil- dren who can localize tenderness, initial plain radiographs should include orthogonal images of the affected limb that visualize the joint both above and below the point of maximum tenderness. A third ob- lique view is included when imag- ing the ankle or foot if an area of suspected pathologic change may be obscured by bone overlap, mini- mal displacement of fracture frag- ments, or minimal physeal widen- ing. 12 If the patient can localize pain but the initial radiographs of the long bones are negative, addi- tional oblique views may reveal more subtle osseous changes, such as a minimally displaced tibial frac- ture (toddler’s fracture) or the peri- osteal elevation of a stress fracture. In children who present with a limp or refusal to bear weight but are too young to localize pain, plain radio- graphs of the entire lower extremity should be obtained (Fig. 2). Plain radiographs are not particu- larly helpful in identifying early bone or joint infections. The early ra- diographic findings of acute hema- togenous osteomyelitis include a nor- mal osseous appearance with subtle displacement and swelling of the soft tissues. 13 Comparison views may depict subtle soft-tissue swelling, but radiographic sensitivity for the early changes of osteomyelitis is less than 50%. 14 The radiographic appearance of early soft-tissue changes due to septic arthritis is difficult to interpret and unreliable. 15 Early bone or joint changes are not typically seen radio- graphically until 10 to 12 days after the onset of bone or joint infection, 13 and the presence of these changes suggests a significant delay in diag- nosis. The triphasic technetium-99m bone scan is an excellent test for evaluating a limping child when the history and physical examina- tion fail to localize the anatomic site of pathologic changes (Fig. 3). Bone scanning has been demonstrated to be superior to the other standard screening tests for infection (tem- perature, white blood cell [WBC] count, erythrocyte sedimentation rate [ESR], and plain radiography) in the limping toddler. 14 The tech- netium accumulates at the site of in- creased blood flow and osteoblastic activity in osteomyelitis, stress frac- tures, occult fractures, neoplasm, and metastases. In suspected early bone infection, bone scans have high sensitivity (84% to 100%) and speci- ficity (70% to 96%). 12,14,16 Although the diagnosis of many long-bone infections can be made John M. Flynn, MD, and Roger F. Widmann, MD Vol 9, No 2, March/April 2001 93 A B Figure 1 A, A healthy limping toddler presented with reproducible tenderness to palpa- tion over the midportion of the tibia. Rotational stress to the tibia was also painful. Although the radiographs were read as normal, an occult fracture was suspected. B, At 4 weeks, radiographs showed periosteal elevation along the medial cortex of the tibia (arrows), confirming the clinical suspicion of a toddler’s fracture. The child’s symptoms resolved after 4 weeks in a cast. without scintigraphy, bone scans are particularly helpful in localiz- ing sepsis around the pelvis and the spine—areas that are difficult to examine and where soft-tissue changes are difficult to identify. 17 Prior bone drilling and periosteal elevation have been demonstrated experimentally to have no effect on a subsequent bone scan performed within 24 hours, 18 and prior aspira- tion has not interfered with results in clinical practice. 17 Other advan- tages of bone scanning over cross- sectional imaging modalities include decreased expense, less need for se- dation, and the ability to image the whole body. Limitations of bone scintigraphy include difficulty in distinguishing between bone infarct and osteomy- elitis in hemoglobinopathies and the occurrence of false-negative bone scans in cases of Langerhans cell his- tiocytosis and some other aggressive tumors in children. 17 Bone scanning has low sensitivity for septic arthri- tis, especially when there is adjacent osteomyelitis, and is therefore not indicated in this circumstance. Leukemia may result in increased, decreased, or no change in tech- netium uptake. 14 A “cold” scan (i.e., one showing low uptake) in the set- ting of suspected osteomyelitis is not necessarily negative; instead, it may represent bone rendered avas- cular due to a subperiosteal or end- osteal abscess. A study of cold bone scans in pediatric patients with osteomyelitis revealed that they had more severe bone infections requir- ing more aggressive medical and surgical treatment compared with control children with “hot” bone scans and osteomyelitis. 19 The Limping Child Journal of the American Academy of Orthopaedic Surgeons 94 A B Figure 2 A, Anteroposterior (AP) radiograph of the hips and pelvis of a 2-year-old girl with a 2-week history of limping, fever, malaise, and difficulty sleeping through the night. Periosteal changes (arrow) were noted in the right femur. B, A full-length AP radiograph of the femur demonstrates the extent of periosteal elevation and geographic medullary canal erosion of the lesion, which on biopsy proved to be eosinophilic granuloma. Figure 3 A, AP radiograph of an 8-year-old girl who presented with a limp and the sudden, nontraumatic onset of severe left groin and thigh pain. The film was read as normal. B, The history, physical examination, and plain radiographs did not allow precise localization of the process. A bone scan showed decreased uptake in the left femoral head, suggesting Legg-Calvé-Perthes disease. A B Ultrasonography is a valuable diagnostic tool in the evaluation of a limping child with an irritable hip (Fig. 4). Ultrasonography is nonin- vasive, requires no sedation, and is typically more accessible and less expensive than other secondary radiologic tests. 20 However, if infection is highly probable, ultra- sonography should not delay urgent operative irrigation and debride- ment. If a hip effusion is noted, the ultrasonographer can assist with a guided aspiration and can docu- ment the intra-articular positioning of the needle. If ultrasonography is not available, a possibly infected hip can be aspirated with fluoro- scopic guidance. In one series of 44 patients with a limp or hip pain and negative plain radiographs, ultrasonog- raphy was 100% accurate in pre- dicting the presence of aspiration- documented hip effusion. 21 Another larger prospective study of 111 chil- dren with irritable hips confirmed that the plain radiograph was of lit- tle value in the detection of early hip effusion; in that study, there was radiographic evidence of effu- sion in 15% of hips, compared with sonographic evidence of effusion in 71% of hips. 15 Furthermore, Zawin et al 22 showed that ultrasound- guided hip aspiration in the radiol- ogy suite decreased the subsequent operative time for septic hips by 50%. However, a large prospective study of 500 painful hips in chil- dren demonstrated that ultrasound cannot effectively differentiate among sterile, purulent, and hem- orrhagic effusions. 23 The authors of that study concluded that ultra- sonography of the hip should be reserved for select cases in which sepsis is suspected. Ultrasound evaluation of the irri- table hip is performed with the transducer oriented in an oblique sagittal plane parallel to the long axis of the femoral neck with the hip in extension. 12 An effusion causes bulging of the iliofemoral ligament, so that the joint capsule appears convex; the normal opposite capsule will be concave. 22 Ultrasonography can help con- firm the diagnosis of osteomyelitis on the basis of characteristic early and late ultrasonographic clinical features. 24 Early changes, such as deep soft-tissue swelling, are fol- lowed by periosteal thickening. Subperiosteal fluid or abscess is seen as a later finding 1 to 2 weeks after the onset of symptoms. The main value of ultrasound imaging of the extremity in cases of suspected in- fection is to rule out subperiosteal abscess. 20 Cross-sectional imaging, includ- ing computed tomography (CT) and magnetic resonance (MR) imaging, is rarely necessary as an initial study in the evaluation of a limping child. Computed tomography is in- dicated specifically for imaging of suspected localized abnormalities of cortical bone (Fig. 5). It may also confirm the presence of either a cen- tral nidus in cases of osteoid osteoma or the occurrence of a tarsal coalition. Magnetic resonance imaging has proved to be the most effective im- aging modality for bone marrow, joints, cartilage, and soft tissues (Fig. 6, C). It is extremely useful in cases of suspected tumor and stress fractures. Laboratory Testing Infection, inflammatory disease, and malignancy all demand rapid diag- nosis and treatment, and laboratory testing may assist both in making the appropriate diagnosis and in monitoring the efficacy of treatment. Laboratory testing is indicated when a child presents with an acute non- traumatic limp and signs and symp- toms of fever, malaise, night pain, or localized complaints. Appropriate tests include a complete blood cell count with differential and determi- nation of the ESR, the C-reactive protein (CRP) and antinuclear anti- body levels, and the rheumatoid fac- tor and Lyme titers. In the setting of bone or joint infection, the WBC count is neither sensitive nor specific. Although the WBC count is elevated in 25% to John M. Flynn, MD, and Roger F. Widmann, MD Vol 9, No 2, March/April 2001 95 A B Figure 4 A, A 12-year-old girl presented with an antalgic limp on the right and thigh pain. She had pain with internal rotation of the hip, suggesting an effusion. The plain radio- graph was normal. B, Sonogram of the right hip shows an effusion. Ultrasound-guided aspiration yielded purulent fluid. Drainage of the septic hip was performed immediately. Femoral head Hip capsule Effusion 31% of children with osteomyeli- tis, 25 normal values for the WBC count are seen frequently in osteo- myelitis. 26 The differential is more sensitive and may be abnormal in as many as 65% of children with osteo- myelitis and 70% with septic arthri- tis. The complete blood cell count may reveal moderate to severe ane- mia in cases of systemic juvenile rheumatoid arthritis (JRA), as well as leukocytosis with active disease. 8 Patients with systemic-onset JRA may present with WBC counts in the range of 30,000 to 50,000/mm 3 . The platelet count may rise considerably as well. The ESR is a sensitive indicator of inflammation and is most helpful in the diagnosis and follow-up of bone or joint infection. The ESR reflects changes in the concentration of fibrinogen synthesized by the liver, which increases after 24 to 48 hours and may not return to normal for 3 weeks with appropriate treat- ment. 27 In one study of previously well children with new-onset limp, an ESR elevated to over 50 mm/hr was associated with a clinically im- portant diagnosis in 77% of cases. 28 The ESR is also a sensitive indicator of infection and is elevated in 90% of patients with osteomyelitis. 16,25 However, early in the course of in- fection, the ESR may be normal. Ex- treme elevation of ESR in what ap- pears to be isolated osteomyelitis should raise the question of associ- ated septic arthritis. C-reactive protein is an acute- phase protein synthesized by the liver in response to inflammation. Unlike the ESR, the CRP level rises within 6 hours of onset of symp- toms and returns to normal within 6 to 10 days with appropriate treat- ment. The CRP level is more sensi- tive than the WBC count or the ESR in assessing the effectiveness of therapy and predicting recovery from osteomyelitis and septic arthri- tis. 27,29 The CRP value is not influ- enced by prior aspiration or drilling of the cortex, and a secondary rise suggests relapse. 29 The CRP level should be determined on the initial screening examination if musculo- skeletal infection is in the differen- tial diagnosis. Aspiration and evaluation of joint fluid should be performed when joint sepsis is considered in the dif- ferential diagnosis. Of the large joints, the hip is the most technically difficult to aspirate. Sedation and local anesthesia are helpful, and aspiration under fluoroscopic guid- ance with arthrography at the com- pletion of the procedure is recom- mended to confirm appropriate spinal needle placement within the joint. 30 Ultrasound-guided aspira- tion provides similar confirmation of needle placement. Culture and cell counts should be obtained in all cases. A WBC count greater than 80,000/mm 3 with a percentage of polymorphonuclear cells greater than 75% is highly suggestive of joint sepsis, although early sepsis may present with a much lower cell count. 30 The rheumatoid factor and anti- nuclear antibody levels are deter- mined when inflammatory arthritis is a possibility. In practice, JRA is the most frequently diagnosed pedi- atric arthritis. 31 It must be noted that the rheumatoid factor test is positive in only 15% to 20% of chil- dren with JRA, and is more fre- quently positive in older children and children in a poor functional class. 8 The finding of a positive antinuclear antibody test is impor- tant in the identification of children most at risk for the development of chronic uveitis, which may result in blindness if untreated. Testing for Lyme disease should be performed on any patient who presents with acute arthritis and who lives in or has recently traveled to an endemic area. 32 The presenta- tion of acute Lyme arthritis may have considerable overlap with that of septic arthritis, including fever, local swelling, pain with range of joint motion, and an elevated WBC count in joint aspirate. Serologic confirmation of Lyme disease is based on a two-test approach con- sisting of a preliminary enzyme- linked immunosorbent assay and a confirmatory Western immunoblot assay, which specifically examines the reactivity of antibodies. 32 The Limping Child Journal of the American Academy of Orthopaedic Surgeons 96 A B Figure 5 A, A 10-year-old soccer player presented with a limp and thigh pain of 4 weeks’ duration. AP radiograph shows a radiodense area in the medial subtrochanteric region. B, CT scan obtained to better characterize the sclerotic area shows a pattern typical of a femoral-neck stress fracture. A biopsy was avoided. The pain and limp resolved after 2 months of protected weight bearing. Making the Diagnosis When a limping child is brought for musculoskeletal evaluation, some potential diagnoses require urgent treatment to ensure the best possible outcome. Some conditions affect all age groups, but many conditions have a peak age of onset. Although there is increasing interest in prac- tice standardization with use of algorithms for many musculoskele- tal conditions, there are so many exceptions in the evaluation of the limping child that any single algo- rithm will be unreliable for all pre- sentations. Despite this complexity, there are five essential questions that the orthopaedist must answer to direct the evaluation of a limping child: (1) Is the limp due to pain? (2) Did the limp develop suddenly or gradually, or has it always been there? (3) Is the child systemically ill? (4) What type of limp does the child exhibit? (5) Can the problem be localized (specifically, is there a point of maximum tenderness)? The answers to these questions will narrow the differential diagnosis and establish the pace of evalua- tion. 33 Determining whether the gait is antalgic is the first step in developing a differential diagnosis (Tables 1 and 2). The answers to these five essen- tial questions direct the evaluation of different clinical scenarios. For example, a healthy 4-year-old pre- sents with the gradual onset of a painless Trendelenburg gait. Exami- nation shows that there is unilateral limitation of hip motion. The work- up of this limp requires only a plain radiograph to establish the diagnosis of Legg-Calvé-Perthes disease or de- velopmental dysplasia of the hip. In a very different scenario, an ill child presents with the sudden onset of an antalgic gait. Samples for screening laboratory studies should be drawn, and plain radio- graphs should be obtained for ana- tomic localization. If the site cannot be localized, a bone scan is valu- able. An MR imaging study may add important information, espe- cially if a malignant condition is suspected. If septic arthritis of the hip is a possibility, ultrasound- guided aspiration may be indicated. Unfortunately, the presentations are usually not this straightforward. The most common challenge is de- termining whether an acute limp is due to trauma. A typical case is illus- trated in Figure 6. The 11-year-old patient had ankle pain after falling. Her pain persisted after casting of a suspected fibular physeal fracture. The plain-radiographic appearance remained normal. Her limp was clearly due to pain, which was wors- ening with time. Because this was un- characteristic for trauma, laboratory tests were obtained, which revealed an ESR of 35 mm/hr. Because the process could be localized by pain and swelling around the distal fibula, a bone scan was not needed. An MR imaging study obtained to simultane- ously evaluate the soft tissues, the bone, and the ankle joint revealed osteomyelitis with a soft-tissue ab- scess. The patient was successfully treated with surgical drainage and antibiotics. John M. Flynn, MD, and Roger F. Widmann, MD Vol 9, No 2, March/April 2001 97 A B C Figure 6 An 11-year-old girl sustained a suspected distal fibular physeal fracture. AP (A) and lateral (B) plain radiographs of the ankle taken 10 days after the injury. C, Because of persistent pain and an ESR of 35 mm/hr, an MR imaging study of the distal portion of the leg was obtained. The appearance of this transverse section at the distal fibula is consistent with fibular osteomyelitis and soft-tissue swelling with an abscess, which were successfully treated with surgical drainage and antibiotic therapy. Cultures grew Staphylococcus aureus. Summary Limping children commonly present to the orthopaedic surgeon, who is expected to recognize the gait abnor- mality, determine the probable anatomic origin, and develop a good working diagnosis on which to base a cost-effective strategy for ordering diagnostic tests. Armed with the results of an appropriate history and physical examination and an under- standing of normal and abnormal gait, the orthopaedist can use the child’s age and the answers to five essential questions to develop a dif- ferential diagnosis and plan a selec- tive approach to diagnostic testing. The Limping Child Journal of the American Academy of Orthopaedic Surgeons 98 References 1. Tuten HR, Gabos PG, Kumar SJ, Harter GD: The limping child: A man- ifestation of acute leukemia. J Pediatr Orthop 1998;18:625-629. 2. Sutherland DH, Olshen R, Cooper L, Woo SLY: The development of mature gait. J Bone Joint Surg Am 1980;62: 336-353. 3. Ounpuu S, Gage JR, Davis RB: Three- dimensional lower extremity joint kinetics in normal pediatric gait. J Pediatr Orthop 1991;11:341-349. 4. Phillips WA: The child with a limp. Orthop Clin North Am 1987;18:489-501. 5. Wenger DR, Davids JR, Ring D: Disci- tis and osteomyelitis, in Weinstein SL (ed): The Pediatric Spine: Principles and Practice. New York: Raven Press, 1994, vol 1, pp 813-835. 6. Davids JR: Normal gait and assess- ment of gait disorders, in Morrissy RT, Weinstein SL (eds): Lovell and Winter's Pediatric Orthopaedics, 4th ed. Phila- delphia: Lippincott-Raven, 1996, vol 1, pp 93-116. 7. Morrissy RT: Bone and joint sepsis, in Morrissy RT, Weinstein SL (eds): Lovell & Winter's Pediatric Orthopaedics, 4th ed. Philadelphia: Lippincott-Raven, 1996, vol 1, pp 579-624. 8. Cassidy JT, Petty RE: Textbook of Pedi- atric Rheumatology, 3rd ed. Philadel- phia: WB Saunders, 1995, pp 133-223. 9. Schreck P, Schreck P, Bradley J, Cham- bers H: Musculoskeletal complica- tions of varicella. J Bone Joint Surg Am 1996;78:1713-1719. 10. MacEwen GD, Dehne R: The limping child. Pediatr Rev 1991;12:268-274. 11. Staheli LT, Corbett M, Wyss C, King H: Lower-extremity rotational problems in children: Normal values to guide management. J Bone Joint Surg Am 1985;67:39-47. 12. Myers MT, Thompson GH: Imaging the child with a limp. Pediatr Clin North Am 1997;44:637-658. 13. Capitanio MA, Kirkpatrick JA: Early roentgen observations in acute osteo- myelitis. Am J Roentgenol Radium Ther Nucl Med 1970;108:488-496. 14. Aronson J, Garvin K, Seibert J, Glasier C, Tursky EA: Efficiency of the bone scan for occult limping toddlers. J Pediatr Orthop 1992;12:38-44. 15. Bickerstaff DR, Neal LM, Booth AJ, Brennan PO, Bell MJ: Ultrasound examination of the irritable hip. J Bone Joint Surg Br 1990;72:549-553. 16. Scott RJ, Christofersen MR, Robertson WW Jr, Davidson RS, Rankin L, Drum- mond DS: Acute osteomyelitis in chil- dren: A review of 116 cases. J Pediatr Orthop 1990;10:649-652. 17. McCoy JR, Morrissy RT, Seibert J: Clin- ical experience with the technetium-99 scan in children. Clin Orthop 1981;154: 175-180. 18. Canale ST, Harkness RM, Thomas PA, Massie JD: Does aspiration of bones and joints affect results of later bone scanning? J Pediatr Orthop 1985;5:23-26. 19. Pennington WT, Mott MP, Thometz JG, Sty JR, Metz D: Photopenic bone scan osteomyelitis: A clinical perspec- tive. J Pediatr Orthop 1999;19:695-698. 20. Abernethy LJ, Lee YCP, Cole WG: Ultrasound localization of subperi- osteal abscesses in children with late- acute osteomyelitis. J Pediatr Orthop 1993;13:766-768. 21. Alexander JE, Seibert JJ, Glasier CM, et al: High-resolution hip ultrasound in the limping child. J Clin Ultrasound 1989;17:19-24. 22. Zawin JK, Hoffer FA, Rand FF, Teele RL: Joint effusion in children with an irritable hip: US diagnosis and aspira- tion. Radiology 1993;187:459-463. 23. Miralles M, Gonzalez G, Pulpeiro JR, et al: Sonography of the painful hip in children: 500 consecutive cases. AJR Am J Roentgenol 1989;152:579-582. 24. Mah ET, LeQuesne GW, Gent RJ, Paterson DC: Ultrasonic features of acute osteomyelitis in children. J Bone Joint Surg Br 1994;76:969-974. 25. Faden H, Grossi M: Acute osteomye- litis in children: Reassessment of etio- logic agents and their clinical charac- teristics. Am J Dis Child 1991;145:65-69. 26. Fink CW, Nelson JD: Septic arthritis and osteomyelitis in children. Clin Rheum Dis 1986;12:423-435. 27. Unkila-Kallio L, Kallio MJT, Peltola H: The usefulness of C-reactive protein levels in the identification of concur- rent septic arthritis in children who have acute hematogenous osteomye- litis: A comparison with the usefulness of the erythrocyte sedimentation rate and the white blood-cell count. J Bone Joint Surg Am 1994;76:848-853. 28. Huttenlocher A, Newman TB: Evalua- tion of the erythrocyte sedimentation rate in children presenting with limp, fever, or abdominal pain. Clin Pediatr (Phila) 1997;36:339-344. 29. Unkila-Kallio L, Kallio MJT, Eskola J, Peltola H: Serum C-reactive protein, erythrocyte sedimentation rate, and white blood cell count in acute hema- togenous osteomyelitis of children. Pediatrics 1994;93:59-62. 30. Morrissy RT, Shore SL: Septic arthritis in children, in Gustilo RB, Gruninger RP, Tsukayama DT (eds): Orthopaedic Infection: Diagnosis and Treatment. Philadelphia: WB Saunders, 1989, pp 261-270. 31. Cassidy JT, Nelson AM: The frequen- cy of juvenile arthritis [editorial]. J Rheumatol 1988;15:535-536. 32. Rose CD, Fawcett PT, Eppes SC, Klein JD, Gibney K, Doughty RA: Pediatric Lyme arthritis: Clinical spectrum and outcome. J Pediatr Orthop 1994;14: 238-241. 33. Choban S, Killian JT: Evaluation of acute gait abnormalities in preschool children. J Pediatr Orthop 1990;10:74-78.