Open Access Open Badges Research article

Radiographic signs for detection of femoroacetabular impingement and hip dysplasia should be carefully used in patients with osteoarthritis of the hip

Ingmar Ipach12*, Ina-Christine Rondak3, Saskia Sachsenmaier1, Elisabeth Buck1, Roland Syha4 and Falk Mittag1

Author Affiliations

1 Department of Orthopaedic Surgery, University Hospital of Tuebingen, Hoppe-Seyler-Straße 3, 72074 Tuebingen, Germany

2 Department of Orthopedic Surgery, Hospital of Ingolstadt, Krumenauerstraße 25, 85021 Ingolstadt, Germany

3 Department of Medical Statistics and Epidemiology, Technische Universität München, Ismaninger Str. 22, Munich 81675, Germany

4 Department of Radiology, University Hospital of Tuebingen, Hoppe-Seyler-Straße 3, 72074 Tuebingen, Germany

For all author emails, please log on.

BMC Musculoskeletal Disorders 2014, 15:150  doi:10.1186/1471-2474-15-150

Published: 8 May 2014



During the last years, terms like acetabular retroversion, excessive overcoverage, and abnormal head-neck-junction with the so called “pistol-grip-deformity” has been added to the classical description of hip dysplasia. These anatomical changes could lead to a femoroacetabular impingement (FAI). Both kinds of FAI has been indentified as a main reason for hip pain and progressive degenerative changes leading to early osteoarthritis of the hip. A lot of radiographic criteria on pelvic views have been established to detect classical dysplasia and FAI. The present study was initiated to assess the hypothesis that age and severity of osteoarthritis affect measurements of different radiographic parameters.


The pelvic radiographs of 1614 patients were measured for head-ratio, CE-angle, roof obliquity, extrusion-index, depth-to-width ratio, CCD-angle, sharp’s angle. To evaluate the severity of osteoarthritis of the hip the classification by Kellgren and Lawrence was used. Associations between age and radiographic parameters or severity of osteoarthritis were assessed by Spearman’s (ρ) or Kendall’s (r) rank correlation coefficient, respectively.


366 (22.7%) patients presented no sign of osteoarthritis, 367 (22.7%) patients presented I° osteoarthritis, 460 (28.5%) patients presented II° osteoarthritis, 307 (19%) III° osteoarthritis and 114 (7.1%) IV° osteoarthritis of the hip. The mean head-ratio of all patients was 1.13 ± 0.26 (0.76 – 2.40), the mean CE-angle 40.05° ± 10.13° (0° - 70°), the mean roof obliquity was 35.27°± 4.96° (10° – 55°), the mean extrusion-index was 12.99 ± 9.21 (6.20 – 95.2), the mean depth-to-width ratio was 59.30 ± 8.90 (6.30 – 100), the mean CCD-angle was 127.68° ± 7.22° (123° – 162°) and the mean sharp’s angle was 9.75° ± 5.40° (1° - 34°) There was a weak association between age and the severity of osteoarthritis of the hips (left: r = 0.291; right: r = 0.275; both P < 0.001) with higher osteoarthritis levels observable for elderly patients).


Severity of osteoarthritis has a negative impact on measurements of different radiographic parameters. Therefore - in our opinion - epidemiological studies on prearthrotic deformities should only be performed in healthy adults with no signs of osteoarthritic changes.

Radiographic Signs; Impingement; Hip; Dysplasia; Osteoarthritis