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

Variation in functional pelvic tilt in patients undergoing total hip arthroplasty.

Author information

1
The University of Sydney, School of Aerospace, Mechanical and Mechatronic Engineering, Building J07, Sydney NSW 2006, Australia and Optimized Ortho, 17 Bridge Street, Pymble NSW 2073, Australia.
2
Malabar Orthopaedic Clinic, 43 The Avenue, Windsor, VIC 3181, Australia.
3
Optimized Ortho, 17 Bridge Street, Pymble NSW 2073, Australia.
4
Melbourne Orthopaedic Group, 33 The Avenue, Windsor, VIC 3191, Australia.
5
Peninsula Orthopaedics, 812 Pittwater Rd, Dee Why, NSW 2099, Australia.
6
Sydney Orthopaedic Specialists, Suite 29, Prince of Wales Private Hospital, Randwick NSW 2031, Australia.
7
Monash University, 43 The Avenue, Windsor VIC 3181, Australia.
8
Monash University, 43 The Avenue, Windsor VIC 3181, Australia and Melbourne Orthopaedic Group, 33 The Avenue, Windsor, VIC 3191, Australia.

Abstract

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

[Indexed for MEDLINE]

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