Healed stage deformity: osteoarthritis risk Herring classification: lateral pillar involvement Salter-Thompson classification: extent of femoral head involvement The radiographic findings are those of osteonecrosis. There are separate systems for staging of Perthes disease:Ĭatterall classification: extent of femoral head involvement The investigation of atraumatic limp will often include a hip ultrasound to look for effusion, but ultrasound is unlikely to pick up osteonecrosis. In a small number of patients with Perthes, the radiograph will be normal and persistent symptoms will trigger further imaging, e.g. The best initial test for the diagnosis of Perthes is a pelvic radiograph. In approximately 15% of cases, osteonecrosis occurs bilaterally. Osteonecrosis generally occurs secondary to the abnormal or damaged blood supply to the femoral epiphysis, leading to fragmentation, bone loss, and eventual structural collapse of the femoral head. The specific cause of osteonecrosis in Perthes disease is unclear. It is important to be certain that there is no other cause of osteonecrosis (e.g. This may precipitate the presentation or the realization of symptoms that in fact had been long-standing.īlood tests are typically normal in Perthes. Some children have a coincidental history of trauma. Most children present with atraumatic hip pain or limp 3,5,6. Perthes is considered an idiopathic condition, and there are no clear predisposing factors.
Presentation is typically at a younger age than slipped upper femoral epiphysis (SUFE) with peak presentation at 5-6 years, but confidence intervals are as wide as 2-14 years 8. Perthes disease is relatively uncommon and in Western populations has an incidence approaching 5 to 15:100,000.īoys are five times more likely to be affected than girls.