ePoster #805 - ISHA Annual Scientific Meeting 2016

Measurement Of Acetabular Coverage In The Hip Joint

Bent Lund, MD, Horsens DENMARK
Hanna Voss, MD, Horsens DENMARK
Georgios Charamlipidis, MD, Horsens DENMARK
Jens Kristian Iversen, MD, Horsens DENMARK

Orthopedic Dept.Regional Hospital of Horsens, Horsens, DENMARK

FDA Status Not Applicable

Summary: The Sector Sourcil Angle as a new measurement in DDH

Background: Hip dysplasia and hip joint deformities in general are recognized as possible precursors of osteoarthritic development. Hip dysplasia is characterized by a steep and shallow acetabulum and insufficient acetabular coverage of the femoral head. Because of the decreased area of acetabular and femoral head contact, load forces on the joint increase and might hereby lead to early onset of osteoarthritis. Hence, early and correct identification of hip dysplasia is important in order to offer timely joint preserving treatment and the standing AP pelvic radiograph is the traditional cornerstone of initial conventional radiographic assessment of any hip deformity. On the AP pelvic radiograph, the most commonly used radiographic indices for assessment of hip dysplasia are the Center Edge angle of Wiberg and the Acetabular Index angle of Tönnis. A new measurement, the Sourcil Sector angle, has recently been presented at the International Society for Hip Arthroscopy annual meeting in Cambridge (Ref). The Sourcil Sector angle is a measurement of the upper lateral sourcil of the acetabulum and it was stated that angles < 65 degrees were highly indicative of acetabular dysplasia. Aim: The main research aims of this study were to evaluate the SSA-angle and compare it to the well-known measurements and possibly to confirm the reliability of this measurement in detecting DDH. Another aim was to study intra- and interobserver variability in the different measurement methods Methods: By each of four observers two measurements of 50 consecutive patients (100 hips) were done by angle construction. 35 patients referred to the Orthopedic Dept. with hip/groin problems, whereas the other 15 radiographs were from patients with known DDH from a previous study. The measurements consisted of the modified Center Edge angle by Wiberg, the Acetabular Index angle by Tönnis and the Sourcil Sector angle and were performed in two different settings with a minimum of 20 days in between. Results: When DDH was defined as a CE Angle <25° the SSA-Angle showed a significant difference between normal and dysplastic hips with a cut-off value of 62°. By using logistic regression analysis the Odds Ratio for a dysplastic hip was 4.09 (CI: 2.7- 6.3, p < 0.001) when the SSA-Angle was <62° compared to a SSA- Angle >62°. The cut-off value of 62° was found to have a sensitivity of 0.77 and specificity of 0.56. When DDH on the other hand was defined as an AI angle >10° we found a slight but not significant difference between normal and dysplastic hips with a cut-off value at 57°. In this case an Odds Ratio of 1.39 (CI: 0.9- 2.1, p = 0.12) was found for a dysplastic hip when the SSA-Angle is <57° compared to a SSA-Angle >57°. Conclusion: The SSA-angle can be used as a good supplement to the LCE-angle in measuring potential DDH in patients and a value < 62° is highly indicative of DDH. Reference: "The Sourcil Sector Angle (SSA)" – oral presentation. Stephanie Pun MD. ISHA 2015 Cambridge