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Med Eng Phys. 2019 Feb;64:7-14. doi: 10.1016/j.medengphy.2018.12.006. Epub 2019 Jan 9.

Operative and radiographic acetabular component orientation in total hip replacement: Influence of pelvic orientation and surgical positioning technique.

Author information

1
School of Mechanical and Aerospace Engineering, Queen's University of Belfast, Belfast, UK.
2
Department of Mechanical Engineering, University of Bath, Bath, UK.
3
Primary Joint Unit, Musgrave Park Hospital, Belfast, UK.
4
School of Mechanical and Manufacturing Engineering, Dublin City University, Stokes Building, Collins Avenue, Dublin 9, Ireland; Centre for Medical Engineering Research, School of Mechanical and Manufacturing Engineering, Dublin City University, Stokes Building, Collins Avenue, Dublin 9, Ireland; School of Pharmacy, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK; Trinity Centre for Bioengineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland; Department of Mechanical and Manufacturing Engineering, School of Engineering, Trinity College Dublin, Dublin 2, Ireland. Electronic address: nicholas.dunne@dcu.ie.

Abstract

Orthopaedic surgeons often experience a mismatch between perceived intra-operative and radiographic acetabular cup orientation. This research aimed to assess the impact of pelvic orientation and surgical positioning technique on operative and radiographic cup orientation. Radiographic orientations for two surgical approaches were computationally simulated: a mechanical alignment guide and a transverse acetabular ligament approach, both in combination with different pelvic orientations. Positional errors were defined as the difference between the target radiographic orientation and that achieved. The transverse acetabular ligament method demonstrated smaller positional errors for radiographic version; 4.0° ± 2.9° as compared to 9.4° ± 7.3° for the mechanical alignment guide method. However, both methods resulted in similar errors in radiographic inclination. Multiple regression analysis showed that intraoperative pelvic rotation about the anterior-posterior axis was a strong predictor for these errors (BTAL = -0.893, BMAG = -0.951, p < 0.01). Application of the transverse acetabular ligament method can reduce errors in radiographic version. However, if the orthopaedic surgeon is referencing off the theatre floor to control inclination when operating in lateral decubitus, this is only reliable if the pelvic sagittal plane is horizontal. There is currently no readily available method for ensuring that this is the case during total hip replacement surgery.

KEYWORDS:

Acetabular component inclination; Mechanical alignment guide; Pelvic orientation; Transverse acetabular ligament

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