Variation in functional pelvic tilt in patients undergoing total hip arthroplasty

Bone Joint J. 2017 Feb;99-B(2):184-191. doi: 10.1302/0301-620X.99B2.BJJ-2016-0098.R1.


Aims: The pelvis rotates in the sagittal plane during daily activities. These rotations have a direct effect on the functional orientation of the acetabulum. The aim of this study was to quantify changes in pelvic tilt between different functional positions.

Patients and methods: Pre-operatively, pelvic tilt was measured in 1517 patients undergoing total hip arthroplasty (THA) in three functional positions - supine, standing and flexed seated (the moment when patients initiate rising from a seated position). Supine pelvic tilt was measured from CT scans, standing and flexed seated pelvic tilts were measured from standardised lateral radiographs. Anterior pelvic tilt was assigned a positive value.

Results: The mean pelvic tilt was 4.2° (-20.5° to 24.5°), -1.3° (-30.2° to 27.9°) and 0.6° (-42.0° to 41.3°) in the three positions, respectively. The mean sagittal pelvic rotation from supine to standing was -5.5° (-21.8° to 8.4°), from supine to flexed seated was -3.7° (-48.3° to 38.6°) and from standing to flexed seated was 1.8° (-51.8° to 39.5°). In 259 patients (17%), the extent of sagittal pelvic rotation could lead to functional malorientation of the acetabular component. Factoring in an intra-operative delivery error of ± 5° extends this risk to 51% of patients.

Conclusion: Planning and measurement of the intended position of the acetabular component in the supine position may fail to predict clinically significant changes in its orientation during functional activities, as a consequence of individual pelvic kinematics. Optimal orientation is patient-specific and requires an evaluation of functional pelvic tilt pre-operatively. Cite this article: Bone Joint J 2017;99-B:184-91.

Keywords: Component orientation; Dislocation; Implant positioning; Pelvic tilt.

Publication types

  • Observational Study

MeSH terms

  • Acetabulum / diagnostic imaging
  • Acetabulum / physiopathology*
  • Adult
  • Aged
  • Aged, 80 and over
  • Arthroplasty, Replacement, Hip*
  • Biomechanical Phenomena
  • Female
  • Humans
  • Male
  • Middle Aged
  • Osteoarthritis, Hip / physiopathology*
  • Osteoarthritis, Hip / surgery
  • Pelvic Bones / diagnostic imaging*
  • Pelvic Bones / physiopathology
  • Posture / physiology*
  • Range of Motion, Articular
  • Retrospective Studies
  • Tomography, X-Ray Computed
  • Young Adult