Nationwide epidemiologic survey of idiopathic osteonecrosis of the femoral head.
BACKGROUND
Although numerous studies describe the clinical characteristics of idiopathic osteonecrosis of the femoral head (ONFH) in specific study populations, these have not been confirmed in countrywide studies.


OBJECTIVE
We therefore determined: (1) the annual number of patients seeking medical care and number of patients newly diagnosed; and (2) the distribution of the age and gender of the patients, potential causative factors, severity of the disease, and operative procedures performed.


METHODS
We conducted a nationwide epidemiologic survey in 2005. The survey included all orthopaedic departments in Japan by stratified random sampling according to the number of beds.


RESULTS
The number of patients who sought medical care for idiopathic ONFH during 2004 was estimated to be 11,400 (95% confidence interval, 10,100-12,800). We obtained clinical information from 1502 of these patients. The peak in age distribution occurred in the 40s. Potential causative factors were systemic steroid administration (51%) and habitual alcohol use (31%). Hip replacement was the most frequently performed procedure (65%). Among patients with a history of systemic steroid administration, systemic lupus erythematosus was reported most frequently (31%) as the underlying disease. Among patients younger than 40 years, steroid use was the most prominent potential causative factor (60%), and hip replacement frequently was performed (45%). A greater proportion of patients with no history of steroid or alcohol use was observed among patients 65 years or older (41%).


CONCLUSIONS
In addition to the disease burden of idiopathic ONFH in Japan, our results confirmed the importance of developing preventive and treatment strategies, especially among the younger population.


METHODS
Level IV, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
Fukushima
Wakaba
W
Department of Public Health, Osaka City University Faculty of Medicine, 1-4-3, Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan. wakaba@med.osaka-cu.ac.jp
Fujioka
Mikihiro
M
Kubo
Toshikazu
T
Tamakoshi
Akiko
A
Nagai
Masaki
M
Hirota
Yoshio
Y
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000428:Alcohol Drinking / Q000009:adverse effects / Q000453:epidemiology; D019644:Arthroplasty, Replacement, Hip / Q000706:statistics & numerical data; D005260:Female; D005271:Femur Head Necrosis / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology / Q000601:surgery; D006306:Health Surveys; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012720:Severity of Illness Index; D017678:Sex Distribution; D013256:Steroids / Q000009:adverse effects; D011795:Surveys and Questionnaires; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
D013256:Steroids