Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Hip Pain in the Child

Basics
Description
  • Hip pain is a term used to describe discomfort in the groin, which receives sensory innervation provided by the obturator and femoral nerves.
  • This pain can be produced by a lesion anywhere in the region of the hip joint, such as:
    • Capsule and synovial lining
    • Bone of the pelvis or proximal femur
    • Muscles, nerves, and vascular structures in the region of hip, buttock, groin, or pelvis
  • Regardless of cause, hip pain usually is localized to the region of the anterior groin, the greater trochanter, or the anterolateral thigh down to the knee.
  • Because many of the causes of hip pain need urgent treatment or carry a poor prognosis if left untreated, hip pain must be evaluated thoroughly.
Epidemiology
  • Transient synovitis is reported to be the most common cause of hip pain in children.
  • Male predominance:
    • Septic arthritis, slight; transient synovitis, 2:1; SCFE, 2.5:1; osteomyelitis, 4:1; Legg-Calve-Perthes disease, 6:1.
Incidence
  • Transient synovitis of the hip: 3% risk for a child to have at least 1 episode.
  • Legg-Calve-Perthes disease:
    • Peak incidence at 6 years of age
    • ~1 per 1,500
  • SCFE:
    • Almost always occurs during preadolescence or adolescence
    • 1 per 10,000
Risk Factors
  • Juvenile rheumatoid arthritis
  • Closed trauma
  • Impaired host immune defense
  • Obesity, trauma, and age (all shown to be related to the development of SCFE)
Genetics
A genetic association is not clearly shown, except in conditions such as SCFE, in which ~4% of patients have a family history.
Etiology
  • The 2 most common causes are transient synovitis and septic arthritis.
    • Transient synovitis:
      • Average age of onset of symptoms is 6 years, with most cases occurring in children 3-8 years old.
      • Associated with current or recent illness, trauma, or allergic reaction
    • Septic arthritis:
      • ~2/3 of all cases occur in children <3 years old.
      • Mechanism of onset: Direct extension of osteomyelitis from the proximal metaphysis of the femur into the hip joint or hematogenous dissemination of organisms through the blood supply of the synovial membrane
      • During a child’s first 12-18 months, little resistance exists to the extension of infection across the physis in the proximal femur because of vascular channels in the growth plate, so osteomyelitis and septic arthritis are more common in this group than in others.
      • In newborns, most commonly caused by Staphylococcus, Streptococcus, or Haemophilus influenzae type B
      • In those >6 months old, predominantly caused by Staphylococcus aureus
      • In adolescents, possibly caused by Neisseria gonorrhoeae
    • Legg-Calve-Perthes disease: Cause unknown, although trauma, hypercoagulability, and thrombosis have been postulated
    • SCFE:
      • Physeal weakness during adolescent growth spurt and trauma probably are related.
      • ~80% of patients are obese; hormonal factors most likely are involved.
  • Other types of hip pain:
    • Infectious
    • Traumatic
    • Neoplastic
    • Idiopathic
Associated Conditions
Current or recent illness, trauma, and allergic reactions are associated with transient synovitis.
Diagnosis
Signs and Symptoms
  • Pain referred to the groin, trochanter, anterolateral thigh, or knee
  • Involuntary guarding or spasm of muscles around the hip joint
  • Limitation of active and passive hip motion (i.e., loss of internal rotation and abduction in Legg-Calve-Perthes disease or hip dysplasia; external rotation of the hip with attempted flexion pathognomonic for SCFE)
  • Refusal to walk or bear weight on the affected extremity
  • Limp, possibly antalgic or painless
  • Atrophy of the thigh or buttock muscles
  • Fever in septic arthritis, osteomyelitis
Physical Exam
  • Inspect and palpate the tissues around the hip, buttock, lower back, and thigh to detect warmth, erythema, swelling, bruising, or specific areas of point tenderness (e.g., bursae).
  • Note the lower extremity’s general position.
  • Measure and document passive and active ROM of the hip and knee joints, especially internal and external rotation.
  • Document a complete neurovascular extremity examination, noting any weakness or numbness.
  • If possible, examine the gait, including toe- and heel-walking.
  • If septic arthritis is a distinct possibility, perform a hip aspiration, usually under fluoroscopic or sonographic guidance; if no fluid is obtained, an arthrogram should be performed to confirm needle placement.
Tests
Lab
  • In transient synovitis, Legg-Calve-Perthes disease, SCFE, and hip dysplasia, results of routine tests usually are nonspecific and within normal limits but, to rule out infection, it is important to order these tests.
  • In septic arthritis:
    • The cell count of the aspirated joint fluid is the most sensitive test, with >50,000 cells/mm3.
    • The serum leukocyte count is elevated, and a left shift may occur.
  • Blood cultures:
    • Positive in 40% of children with osteomyelitis or septic arthritis
    • Should always be obtained during the initial stages of the workup
Imaging
  • Plain radiographs in septic arthritis may show obliteration of fat planes and soft-tissue swelling.
  • With early osteomyelitis, one may see mottling of bone density; later, sclerosis (new bone formation) and lytic lesions (additional bony destruction) are more prevalent, with destruction of the femoral head being the end result.
  • In transient synovitis, plain films of the hip (AP and lateral views) are nonspecific, but they may help rule out other diagnoses.
  • In Legg-Calve-Perthes disease, plain film findings include:
    • Early: Failure of epiphyseal growth and loss of bone density
    • Later: Crescent-shaped subchondral fracture in the femoral head, shortening of the femoral neck, and flattening or (ultimately) enlargement of the femoral head
  • Widening of the growth plate, mild osteopenia of the proximal femur, or displacement of the epiphysis is seen in SCFE.
Pathological Findings
  • In septic arthritis, synovial hypertrophy initially; later, cartilage destruction
  • In SCFE, posterior and inferior displacement of the femoral head on the metaphysis
  • In Perthes disease, flattened and extruded femoral head
Differential Diagnosis
  • Transient synovitis (although the most common cause of hip pain) should be a diagnosis of exclusion only.
  • Infections of the hip joint, proximal femur, pelvis, intervertebral discs, SI joint
  • Legg-Calve-Perthes disease (AVN of the femoral head)
  • SCFE
  • Juvenile rheumatoid arthritis, early osteoarthritis
  • Tumors of the pelvis, spine, or proximal femur
  • Bursitis of psoas or trochanter
  • Sickle cell crisis
  • Nonarticular processes
  • SI joint septic arthritis
  • Pyomyositis around the hip
  • Psoas septic bursitis
  • Leukemia or lymphoma
Treatment
General Measures
  • Transient synovitis:
    • Rapidly resolve underlying inflammation with rest and anti-inflammatory agents.
    • Prescribe bed rest and no weightbearing on the involved joint until pain resolves and full motion returns.
    • Spontaneous resolution is the natural course: This condition usually is self-limiting.
  • Septic arthritis:
    • Perform immediate surgical drainage and administer antibiotic therapy.
    • Antibiotics:
      • Give broad-spectrum antibiotic coverage until culture results are available.
      • Oral antibiotics, if appropriate, usually are given for 3 weeks, until the clinical examination and/or ESR has returned to normal.
      • Splint hips in abduction if capsular distention has occurred.
      • After infection is controlled and drainage has ceased, begin ROM exercises.
  • Legg-Calve-Perthes disease:
    • Prevent subluxation.
    • Preserve the sphericity of the femoral head.
    • Order bed rest, if needed, and traction to reduce spasms and synovitis.
    • Surgical reconstruction sometimes is necessary to maintain the femoral head within the acetabulum.
  • SCFE:
    • Prevent additional slipping while minimizing the risk of AVN or chondrolysis.
    • Provide the necessary immobilization for acute slips with prompt in situ pin fixation with threaded screws.
Special Therapy
Physical Therapy
Not usually required
 
Medication
First Line
  • Appropriate antibiotics are essential for the treatment of septic arthritis and osteomyelitis.
  • NSAIDs are appropriate for transient synovitis.
Surgery
  • An anterior or posterior approach to the hip may be used, with irrigation, debridement, and insertion of drain.
  • For osteomyelitis:
    • A small window is cut in the bone for curettage of material for culture and open drainage.
    • Chronic osteomyelitis, although rare, often requires surgical debridement.
  • Legg-Calve-Perthes disease may require surgical reconstruction of the femur or acetabulum for severe cases.
  • In situ percutaneous pinning is required for SCFE to prevent additional slips and the associated complications.
Follow-up
Prognosis
  • Septic arthritis and osteomyelitis:
    • Early detection, may have good prognosis
    • Chronic osteomyelitis often results in residual deformity.
  • Legg-Calve-Perthes disease:
    • The smaller the amount of avascular bone and the younger the child at the onset of disease, the better the prognosis, although some residual deformity always is seen on radiographs.
    • Other good prognostic signs include lack of lateralization or extrusion and adequate ROM.
  • SCFE:
    • Long-term prognosis depends on the amount of displacement.
    • Patients with more severe slips have a greater likelihood of developing degenerative arthritis later in life.
Complications
  • Untreated septic arthritis and osteomyelitis can be devastating for a growing child and can result in limb shortening, joint-surface irregularities, stiffness, and early degenerative changes. (Cartilage destruction begins as early as 8 hours after the onset of infection.)
  • SFCE:
    • Either the slip itself or reduction attempts may result in AVN or chondrolysis, a condition in which the cartilage of the femoral head degenerates and produces joint narrowing, stiffness, contracture, pain, and limping.
    • Patients with SCFE have a higher-than-normal risk of developing degenerative arthritis.
Patient Monitoring
  • ESR or C-reactive protein value:
    • Shown to be a reliable marker to guide the length of antibiotic therapy after surgical management for septic arthritis and osteomyelitis
    • Should return to within normal limits before antibiotics are discontinued.
  • Observation only is appropriate for all patients with transient synovitis and for patients with Legg-Calve-Perthes disease with minimal involvement of the femoral head (<50%).
Miscellaneous
Codes
ICD9-CM
  • 711.0 Septic arthritis
  • 719.45 Hip pain, not otherwise specified
  • 732.1 Perthes disease
  • 732.2 SCFE
Patient Teaching
  • The parents of a patient who is presumed to have synovitis of the hip should be able to observe the child and ensure that improvement continues.
  • They should maintain regular follow-up and should contact the physician if the child’s status worsens.
FAQ
Q: What is transient synovitis of the hip?
A: It is an idiopathic inflammation of the hip that resolves spontaneously.
 
Q: What is chondrolysis?
A: It is loss of joint cartilage; it may occur from infection, inflammation, abrasion, or unknown causes.

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