Analysis of interobserver reliability for radiographic staging of coxarthrosis and indexes of acetabular dysplasia: a preliminary study.
BACKGROUND
We are planning a multicenter survey on coxarthrosis and acetabular dysplasia in Japan. To collect reliable data, we performed a preliminary study to elucidate the observer agreement on assessment items.


METHODS
We collected radiographs of hip joints in eight patients with various findings of coxarthrosis. Twelve registered orthopedic specialists evaluated them regarding the roentgenographic stage of coxarthrosis and five indexes of acetabular dysplasia (acetabular angle, center-edge angle, acetabular roof obliquity, acetabular head quotient, approximate acetabular quotient). To assess observer agreement, we calculated the value of the kappa statistic for stages and the coefficient of variation for the indexes. The same 12 specialists then assessed the coxarthritis stage on the same radiographs 1 month after the first evaluation based on our own descriptions of the roentgenographic stages.


RESULTS
For the first evaluation of the roentgenographic stage, the value of the kappa statistic was 0.448; and for the second evaluation it was 0.600. The results of the coefficient of variation for the indexes of acetabular dysplasia, ranked in ascending order, were as follows: acetabular angle, acetabular head quotient, acetabular roof obliquity, center-edge angle, approximate acetabular quotient.


CONCLUSIONS
For the upcoming multicenter survey, clear descriptions of the stages of coxarthrosis and selection of appropriate indexes can be helpful for collecting dependable results.
Division of Science for Joint Reconstruction, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
Yoshio
Y
Takatori
Kazuya
K
Ito
Muroto
M
Sofue
Yoshio
Y
Hirota
Moritoshi
M
Itoman
Tadami
T
Matsumoto
Yoshiki
Y
Hamada
Hiroyuki
H
Shindo
Harumoto
H
Yamada
Yuji
Y
Yasunaga
Hiroshi
H
Ito
Satoshi
S
Mori
Ichiro
I
Owan
Genji
G
Fujii
Hirotsugu
H
Ohashi
Taro
T
Mawatari
Toshiro
T
Iga
Naonobu
N
Takahira
Tanzo
T
Sugimori
Hajime
H
Sugiyama
Kunihiko
K
Okano
Tatsuro
T
Karita
Kenichi
K
Ando
Takanari
T
Hamaki
Teruhisa
T
Hirayama
Ken
K
Iwata
Masanori
M
Matsuura
Seiya
S
Jingushi
D000077:Acetabulum / Q000000981:diagnostic imaging*; D001848:Bone Diseases, Developmental / Q000000981:diagnostic imaging*; D006801:Humans; D015588:Observer Variation; D015207:Osteoarthritis, Hip / Q000145:classification / Q000000981:diagnostic imaging*; D010865:Pilot Projects; D011859:Radiography; D012720:Severity of Illness Index