Objective The objective of this study was to define, in unilateral hip
osteoarthritis (OA), factors predicting the outcome of the other hip.
Materials and Methods We examined the anteroposterior radiographs of the
pelvis of 95 white patients with unilateral idiopathic (56 patients) or
secondary to congenital hip diseases (39 patients) OA. The other hip was
free from symptoms (pain or limping) at the initial examination and
without radiographic evidence of OA; it was what we call a “normal”
hip. Two parameters were evaluated: (1) the type of osteoarthritis of
the involved hip and (2) the range of four radiographic indices of the
contralateral hip: the sourcil inclination “”(weight-bearing
surface), the acetabular angle, the Wiberg’s center-edge angle, and the
neck-shaft angle.
Follow-up radiographs for the hips that remained OA-free were available
for 10 to 35 years and for those that developed OA, at the time of
initial symptoms, range 2 to 31 years.
Results Logistic regression analysis showed that the presence of
idiopathic OA in one hip had a statistically significant effect on the
development of OA on the other hip (p < 0.001). Minor deviations of
radiographic indices of the contralateral hip is not a predictive factor
for its outcome. When the radiographic indices are examined together
with the pathology of the involved hip, only WBS was shown to have a
significant effect to the development of OA and its type (p < 0.001).
Conclusions The following conclusions can be drawn from this study: 1.
Patient with idiopathic OA of one hip is at increased risk of developing
OA in the other hip. 2. The outcome of the other hip cannot be predicted
only on the basis of the evaluation of its radiographic indices. 3.
Among the different indices, WBS seems to have a strong influence toward
the development of OA