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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

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 mid-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

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 vari-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 swdur-ing 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

Table 1

Differential Diagnosis of Antalgic Gait

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

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

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 dorsiplantar-flexors

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

be documented in children with

in-toeing or out-in-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 fracfrac-ture) 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 fracfrac-tures, 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

Figure 1 A, A healthy limping toddler presented with reproducible tenderness to

palpa-tion over the midporpalpa-tion of the tibia Rotapalpa-tional 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,18and 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

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.

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 al22 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

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,25normal 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/mm3 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 confirmaaspira-tion of needle placement Culture and cell counts should be obtained in all cases A WBC count greater than 80,000/mm3 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

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

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.

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

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