Distribution of anterior inferior iliac spine morphology in patients with and without hip impingement

Subspinous impingement of the anterior inferior iliac spine against the head-neck junction of the femur is an increasingly recognised cause of impingement in the hip. A classification system has previously been proposed for the morphology of the anterior inferior iliac spine, which correlates with a reduced range of movement of the joint and may predispose patients to subspine impingement of the hip.
The aim of the present study was to examine the morphological distribution of the types of anterior inferior iliac spine in patients with and without a diagnosis of hip impingement, and to correlate this morphology with the intraoperative findings during surgery.
Three-dimensional image reconstruction from computed tomography of the pelvis was carried out in a sample of 449 hips in patients with no history of hip pain or hip impingement, and in 59 hips with a diagnosis of hip impingement. Three blinded reviewers classified the anterior inferior iliac spine type for each hip twice. The morphological distribution between symptomatic and asymptomatic patients was compared and correlated with age, sex and the affected side. Within the symptomatic cohort, the morphology of the anterior inferior iliac spine was compared with the intraoperative assessment of a low-lying anterior inferior iliac spine.
The morphological distribution between symptomatic and asymptomatic patients was similar, with 75% of the patients in the asymptomatic group and 80% of those in the symptomatic group having a type 2 or 3 anterior inferior iliac spine. No significant differences were observed in the assessed type classification between the groups. In the symptomatic group there was no significant correlation between the surgeon’s assessment of a low-lying anterior inferior iliac spine and a type 2 or 3 radiographic classification.
These findings suggest that a high proportion of patients with an anterior inferior iliac spine morphology associated with subspine impingement are in fact asymptomatic. The existing radiographic classification should not therefore be used on its own for clinical decision-making.
Source: “American Journal of Sports Medicine”, December 2016