Ischiofemoral Impingement and the Utility of Full-Range-of-Motion Magnetic Resonance Imaging in Its Detection
Ischiofemoral impingement is a cause of hip pain resulting from compression on the quadratus femoris muscle between the ischium and femoral lesser trochanter. The most widely accepted diagnostic criterion is hip pain with isolated edema-like signal in the ipsilateral quadratus femoris muscle on magnetic resonance imaging (MRI). Additional criteria based on measurements of the ischiofemoral and quadratus femoris spaces have recently been suggested. However, because these measurements are positioning-dependent, we used full-range-of-motion MRI to increase the diagnostic yield. By evaluating through a range of motion, we detected a case of impingement involving the ischial tuberosity and the lesser trochanter, with probable contributing impingement between the ischial tuberosity and greater trochanter.
In this article, we briefly review the topic of ischiofemoral impingement, provide an example of how range-of-motion MRI can improve diagnostic accuracy, describe our protocol, and propose exploring the need for an expanded definition of the impingement criteria.
Discussion
While femoroacetabular impingement is a widely recognized and sometimes surgically treated syndrome, IFI may be overlooked as a cause of hip pain. Although IFI is traditionally described as mass effect on the QFM by the ischium/hamstring tendons origin and the lesser trochanter, we propose expansion of this criteria to include narrowing resulting from the greater trochanter in external rotation as a potential source of impingement. By use of FROM MRI, we adapted measurements previously described for IFI to evaluate for compression of the QFM by adjacent osseous and tendinous structures throughout the full range of internal/external hip rotation. In this case, FROM imaging provided evidence of possible anatomical narrowing caused by the greater trochanter, in addition to that caused by the lesser trochanter. Given that impingement may be caused by either the greater or lesser trochanters, it is prudent to perform FROM MRI in evaluating patients with suspected IFI. If FROM imaging is not feasible, static imaging in both maximal internal and external rotation may allow for better assessment. There have been no large studies conducted to assess the normal interval between the ischial tuberosity/hamstring origins and the greater trochanter.
The purpose of this report is to call attention to a source of impingement that may be undetected with static MRI, possibly leading to a missed diagnosis. While we believe this to be the first reported example of impingement involving the greater trochanter, larger studies should be conducted to explore this possible source of impingement. Information about the incidence of greater trochanteric impingement could lead to changes in our understanding of this syndrome and its management.
