Painful Hips In Children

Hip pain in children is always a potentially serious and needs urgent assessment. Acute hip pain is usually referred to the surgeons, and the main concern is to distinguish infection of the hip joint or pelvic bones from irritable hip.
If examination shows a restriction of hip movement or there are x-ray abnormalities, many will have a serious disorder requiring long-term management.

• At any age:
  • Transient synovitis = Irritable hip (commonest cause of hip pain in a well child)
  • Trauma
  • Septic arthritis of the hip - Always consider this - particularly in a younger, febrile or unwell child
    (can destroy a hip joint within hours and is therefore a surgical emergency).
  • Acute osteomyelitis of the proximal femur
  • Tuberculous arthritis
  • Juvenile spondyloarthritis/rheumatoid arthritis and chronic arthritis
  • Bone malignancy
• Age under 5 years:
  • Developmental dysplasia of the hip (formerly called congenital dislocation of hip)
  • Infantile coxa vera
  • Acute infective epiphysitis
• Age 5-10 years:
  • Perthes' disease
• Age 10-15 years
  • Slipped upper femoral epiphysis (also called slipped capital femoral epiphysis)

These depend on the likely differential diagnosis:

• Plain X-ray hips (always do both for comparison - and include AP and lateral "frog leg" view).
• Ultrasound - best method of showing hip joint effusion, and may guide the needle if aspiration is appropriate.
• MRI - not often used in clinical practice, but may help if diagnosis unclear or surgery contemplated.

1. Transient synovitis
   • Summary:
     • Usually has acute onset.¹
     • Self limiting condition thought to be due to viral infection or an autoimmune process.
     • Often preceded by a viral upper respiratory tract infection.
     • Twice as common in boys.
   • Presentation:
     • Pain usually not severe but may prevent weight-bearing on the affected leg.
     • Usually no pain at rest and passive movements are only painful at the extreme range of movement.
     • Child is usually well and the ESR is either normal or slightly raised.
   • Treatment
     • Includes rest and analgesia, with mobilisation once pain has settled.
     • Symptoms usually resolve within 2 weeks but may recur.
     • There is no evidence of any long term complications.
2. Developmental dysplasia of the hip
   • Summary:
     • Up to 60% of apparently abnormal hips will become normal without treatment after 1 month, leaving the true incidence as 1-2 per 1,000.
   • Risk factors:
     • Female
     • Breech position
     • Caesarean section
     • First born child
     • Prematurity
     • Oligohydramnios
     • Family history
     • DDH is associated with club feet, spina bifida and infantile scoliosis
   • Presentation
     • Barlow's test, Ortalani's test
     • Asymmetrical skin creases in the thigh or buttock
     • Unequal leg length
     • Reduced hip abduction in flexion (normal is 90 degrees)
     • Reduced distance between greater trochanter and anterior superior iliac spine
   • Management
     • Splinting with a Pavlik harness for between six and twelve weeks - can lead to a normal hip in 95% of cases.
     • The later the condition is diagnosed and treated, the more likely surgery is required and the poorer the prognosis.
3. Septic arthritis
   • Summary:
     • Most often affects hip, knee, ankle, shoulder or elbow.
     • Most often affects children under 2 years.
     • Staphylococcal infection is the most common cause. Haemophilus influenzae arthritis may be associated with concomitant meningitis.
     • Tuberculous infection is increasing, especially in those with contacts in Africa and South Asia.
   • Presentation
     • Early features are often non-specific.
     • Child often very unwell.
     • Pain often present at rest and there is resistance to attempted movement of the hip.
     • Older children are usually reluctant to weight bear and may be more aware of referred pain in the knee.
     • Hip is kept flexed, abducted and externally rotated.
   • Investigations
     • Full blood count, ESR, CRP
     • X-rays, ultrasound
     • MRI and isotope scans are occasionally required
     • Joint aspiration under ultrasound control may be tried. Aspiration of pus warrants immediate surgery.
   • Management
     • Surgical emergency.
     • Antibiotics must not be started in the community (may interfere with culture results).
     • Surgical drainage of pus and irrigation.
     • Antibiotics, depending on culture results:
       • Initial recommended treatment is flucloxacillin plus fusidic acid, or clindamycin alone if penicillin-allergic.²
       • Treatment is usually for 6 weeks (longer if complicated infection).²
       • If child under 5 and not immunised against Haemophilus influenzae, use cefotaxime plus flucloxacillin.²
4. Perthes' disease
   • Summary:
     • Self-limiting condition with occlusion of blood supply to femoral head causing avascular necrosis.
     • Re-vascularisation and remodelling occur but the femoral head may remain an abnormal shape.
     • Most often affects boys (80%) and those aged 5-10 years.
     • Increased risk with low birth weight, short stature, low socio-economic class and passive smoking.
     • Unilateral in 85% of cases. Other diagnoses should be considered in bilateral cases, e.g. hypothyroidism, epiphyseal dysplasia, Gaucher's disease.
   • Presentation
     • Gradual onset of pain (may be referred to the knee), limp and restriction of hip movements.
     • More advanced cases may cause leg shortening and proximal muscle wasting.
     • X-rays are initially normal but later show flattening of the superolateral epiphysis and fragmentation.
   • Treatment
     • Rest and physiotherapy (to maintain a good range of movements) may be sufficient.
     • Further conservative treatment includes casting to hold the thigh in abduction. Casting may be required for 12-18 months.
     • Surgical intervention may be required for severe cases, delayed diagnosis and older children.
     • Prognosis is overall good with normal hip with just a slight restriction of movement. But many develop osteoarthritis of the hip in later life.
     • Prognosis is worse in girls and older age of presentation.
5. Slipped upper femoral epiphysis
   • Summary
     • Usually occurs at the onset of puberty and most often in children who are either very tall and thin, or short and obese.
     • Other risk factors include Afro-Caribbean, boys, family history.
     • One quarter of cases are bilateral.
   • Presentation
     • Hip, thigh and knee pain. Often initially a several week history of vague groin or thigh discomfort.
     • May be able to weight bear, but is painful.
     • Flexion of hip often also causes external rotation.
     • May be leg shortening.
   • Management
     • Most slips are less than 50% and treated by surgical pinning.
     • Slips greater than 50% require osteotomy and pinning, with a higher risk of avascular necrosis.
     • Complications include limb length discrepancy, abnormal gait, chondrolysis and also osteoarthritis of the hip (hip replacement may be required in early adult life).