Background: Protrusio acetabuli is known to occur in patients with
Marfan syndrome, but its prevalence, its effects on hip function, and its
possible association with the subsequent development of degenerative hip
disease have not been studied in a large population. Nevertheless, some
clinicians have recommended prophylactic hip surgery for preadolescents with
Marfan syndrome and protrusio acetabuli.
Methods: We performed a cross-sectional study of 173 patients (346
hips) with Marfan syndrome who were interviewed and examined for calculation
of the Iowa hip score. Anteroposterior radiographs of the pelvis were made,
and two radiographic indices of acetabular depth were measured: (1) the
center-edge angle of Wiberg and (2) the acetabular-ilioischial distance. The
presence of protrusio was defined with use of two extant definitions: (1) a
center-edge angle of >50° or (2) an acetabular-ilioischial distance of
=3 mm in male patients or =6 mm in female patients. Linear regression
analyses were performed between these radiographic indices of acetabular depth
and patient age, Iowa hip scores, the magnitude of the radiographic joint
space, and range of motion.
Results: The prevalence of protrusio acetabuli was 27% according to
the center-edge angle criterion and 16% according to the
acetabular-ilioischial distance criterion. The prevalence of protrusio
increased until the age of twenty years and remained stable after the age of
twenty years. Slight but significant negative correlations were detected
between the two radiographic indices of acetabular depth and both the Iowa hip
score and the summed range of motion (p < 0.02 for all). No significant
relationship was found between the two radiographic indices and pain scores.
In patients with Marfan syndrome who were more than forty years old, the Iowa
hip scores for hips with protrusio were not significantly lower than those for
hips without protrusio.
Conclusions: In patients with Marfan syndrome, the prevalence of
protrusio acetabuli increases during the first two decades of life and then
plateaus in terms of both population-wide prevalence and radiographic
severity. In this population, protrusio generally is not associated with
severely problematic hip function but it is associated with slightly decreased
range of motion of the hip. We concluded that prophylactic surgical
intervention is not indicated for most patients with Marfan syndrome who have
a radiographic diagnosis of protrusio.