Eser Sanverdi MD, Abstract Co-Author: Nothing to Disclose

Mehmet Ali Gurses MD, Abstract Co-Author: Nothing to Disclose

Seray Akcalar Yildirim MD, Abstract Co-Author: Nothing to Disclose

Asim Kayaalp MD, Abstract Co-Author: Nothing to Disclose

Reha Tandogan MD, Abstract Co-Author: Nothing to Disclose

Sedat Alibek MD, Abstract Co-Author: Speakers Bureau, General Electric Company

Nalan Yildirim-Eryilmaz MD, Presenter: Nothing to Disclose

The purpose of this study was to define the normal values of subspine interval (SI), and the angle of anterior inferior iliac spine (AIIS) - acetabulum (AAA) in normal individuals.

We reviewed abdomen computed tomography scans of 157 patients who had been examined for reasons other than subspine impingement. For the measurements, sagittal-oblique reformatted images that parallel to midaxis line of AIIS were obtained. The SI was accepted as the distance between the most anterior-inferior edge of the AIIS and the acetabular rim. The AAA was defined as the angle between the line traversing through the long axis of AIIS and the line that connecting the points of conjunction of acetabular roof and deepest medial cortex of AISS in the axial images. Normal values and ranges of both SI and AAA were assessed. Age and gender differences were analyzed.

312 measurements of SI were made in 157 patients. 77 female(49%) and 80 male(51%) patients were included by the study. Mean age was 34.44 years with a range of 20-50 years. Overall, mean SI was found as 15.77±3.73 mm. SI was found to be significantly lower in females than that of males (17.22±3.34 mm in males, 13.61±2.85 mm in females, P=0.02). The mean AAA was calculated as 110.8˚(with a range of 90˚-129˚). Patients with severe degeneration and developmental dysplasia of hip joint were not included by the study.

Subspine impingement is a recently described subtype of femoro-acetabular impingement. Its clinical diagnosis might be challenging and there are no objective radiological measurements to adequately describe this pathology. To the best of our knowledge, normal values of SI in asymptomatic individuals have not been reported in the English language literature. The range of normal values of SI might be helpful in the diagnosis of subspine impingement. Moreover, smaller values of AAA might indicate narrowing of the potential subspine space, causing pathological contact of the AIIS and femoral head during hip flexion. Further clinical studies are needed to investigate the relevance of our radiological findings.

Subspine impingement has been reported to be a potential cause of femoroacetabular impingement. CT measurement of the subspine interval and the curve of AIIS may be helpful in diagnosis.Definition of normal values will form the base of further studies to describe pathological cut-off values.

Sanverdi, E, Gurses, M, Akcalar Yildirim, S, Kayaalp, A, Tandogan, R, Alibek, S, Yildirim-Eryilmaz, N, Normal Values of the Subspinal Interval and the Angle of AIIS - Acetabulum: A Multicentric CT Study.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14016475.html