Background/Purpose: Alterations in hip morphology, such as femoroacetabular
impingement, have been associated with incident hip OA and total hip
replacement (THR), but associations of these morphologic variations with hip symptoms
are less clear, and have not been studied in a community-based sample including
participants with and without OA.

Methods: This
preliminary analysis was performed as part of our ongoing work to determine the
prevalence of morphologic features at the hip at the baseline visit for the
Johnston County OA project, a large community-based cohort.  At the time of this analysis, 2612 hips
had been read, 120 were excluded based on excessive tilt/rotation, and 2492 hips
(from 1252 individuals) were included. 
The outcome of hip symptoms was assessed in 3 ways: 1) response to the
question “On MOST days do you have pain, aching or stiffness in your right|left hip?” (graded none, mild, moderate, or severe);
2) pain on internal rotation during clinical exam (graded none, mild, or
moderate/severe); 3) self-reported groin pain (present or absent). Validated
software (Oxmorf) was used to assess 27 aspects of
hip morphology, and differences in means among categories of the symptom
variables were assessed using GEE to account for within-person correlation (but
no adjustment for any covariates in these preliminary analyses).  P values <=0.05 for any difference
between groups were considered significant.

Results: Of
the included individuals, 37% were men, 36% were African American, with a mean
age of 63.8 ± 9.8 years and BMI 28.8 ± 5.9 kg/m².  Kellgren-Lawrence
grade was 0 or 1 in 72% of hips. Reliability for all measures was acceptable
(intra- [ICC 0.7-1.00] and inter-reader ICC 0.5-1.00).  We focused on 10 continuous measures of
hip morphology (Table).  None of
these was statistically significantly associated with hip pain, aching, or
stiffness on most days (p>0.2 for all). 
However, several of the morphologic indicators (increased acetabular depth/width ratio, AP alpha angle, extrusion
index, femoral shaft angle, and Gosvig ratio, as well
as decreased minimum joint space width [JSW] and proximal femoral angle)
were significantly associated with pain on internal rotation (Table).   All but extrusion index, femoral
shaft angle, and proximal femoral angle were also associated with groin pain.

Conclusion:
Indicators of femoral morphology, including measures of acetabular dimension,
acetabular coverage (extrusion index), femoral angles, and indicators of
cam-type lesions (AP alpha angle and Gosvig ratio),
were associated with pain on internal rotation and with groin pain, but not
with self-reported pain, aching and stiffness.  These preliminary findings are
supportive of an association between femoral morphology such as that seen in
FAI and symptoms at the hip in the general population.  Further study in a larger number of hips
will assess differences by race, gender, and other key covariates.