How do surgeons position the pelvis and how much does it move during hip arthroplasty?

George Grammatopoulos, Hemant Pandit, R da Assuncao, A. Calistri, P. McLardy-Smith, K. A. De Smet, H.S. Gill, D. W. Murray

Research output: Contribution to conferencePaperpeer-review


INTRODUCTION: Although cup orientation is important for outcome, a great amount of variability is seen, especially in non navigated hip arthroplasties. Pelvic positioning at set-up and movement of the pelvis during surgery are critical parts of hip arthroplasty. Pelvic orientation at the time of cup implantation influences the resultant cup orientation, as the later is measured relative to the pelvic coordinate frame. Surgeons aim for the pelvis to be ‘square’ (i.e. neutral) relative to the operating table at set-up and for the pelvis to move as little as possible during surgery. A neutral orientation would equate to 0° of pelvic tilt, obliquity and rotation relative to the operating table.
OBJECTIVES: This in vivo study aims to identify how surgeons orientate the pelvis at set-up, how much the pelvis moves during surgery and what factors influence this movement.
METHODS: 67 patients were prospectively included in this study, employing the principles of stereo-photogrammetry (SPG) and a validated SPG technique of 2mm accuracy. Non-navigated, arthroplasties were performed by 3 surgeons, using the same support over the sacrum and 3 different types of support anteriorly (pubis only, one ASIS only, both ASIS) as per routine practice. Following positioning, surgeons identified the locations of bony landmarks used for positioning (ASISs/Pubis/Lumbro-Sacral Junction), allowing calculation of pelvic orientation at set-up. In order to determine the amount of pelvic movement, the 3-D movement of a k-wire inserted at the iliac wing, prior to initial incision, was measured at various time-points during surgery. Majority of patients were female (65%), mean BMI was 33 and all were operated in the lateral decubitus position. Most underwent a THA (n=52), whilst the remaining underwent a hip resurfacing. The majority were operated via a posterior approach (n=51) and the remaining via a lateral approach.
RESULTS: Pelvic orientation at set-up varied widely (Mean/SD; tilt:-8°/16°, obliquity:-1°/7°, rotation:2°/ 9°). Surgeons positioned the pelvis with significant differences in pelvic tilt (p<0.001), but no differences in obliquity or rotation (p=0.7). The surgeon that used the pubic-only support has the smallest tilt deviation from neutral (5°, SD: 9°). The mean angular arc of wire movement was 9° (SD:6°, range:0.5-28°). No patient-dependent factor (gender, BMI, cup size) influenced movement. Factors influencing movement included surgeon, approach (posterior>lateral), procedure (resurfacing>THA) (p<0.001) and supports (pubis only>2xASIS) (p=0.02).
CONCLUSION: Although on average pelvic orientation was close to neutral, the variability as evident by the SDs was great, especially for pelvic tilt. Similarly, the variability in pelvic movement between set-up and impaction was large. These two variables would lead to a great variability in the orientation of the pelvis at impaction and hence, at least inpart, account for the huge variability in final cup orientation detected in all series. In order to minimise this variability surgeons should routinely check for pelvic-tilt. In addition, they should consider factors that increase pelvic movement during the procedure (support, procedure, approach). Such measures would increase reliability of obtaining a target cup orientation.
Original languageEnglish
Publication statusPublished - Jun 2013
Event14th EFORT Congress 2013 - Istanbul, Turkey
Duration: 5 Jun 20138 Jun 2013


Conference14th EFORT Congress 2013


Dive into the research topics of 'How do surgeons position the pelvis and how much does it move during hip arthroplasty?'. Together they form a unique fingerprint.

Cite this