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. 2021 Oct 8:11:222-228.
doi: 10.1016/j.artd.2021.08.016. eCollection 2021 Oct.

Mechanical and Anatomical Alignment Guide Techniques Are Superior to Freehand in Achieving Target Orientation of an Acetabular Component

Robert Bruce-Brand  1 , Paul Magill  1 , Christopher O'Neill  1 , Paul Karayiannis  1 , Janet Hill  1 , David Beverland  1
Affiliations

Mechanical and Anatomical Alignment Guide Techniques Are Superior to Freehand in Achieving Target Orientation of an Acetabular Component

Robert Bruce-Brand et al. Arthroplast Today. .

Abstract

Background: Achieving accurate and consistent acetabular component orientation remains a major challenge in total hip arthroplasty.

Methods: We used a pelvic model to compare freehand techniques vs mechanical and anatomical alignment guides in achieving a target operative inclination (OI) and operative anteversion (OA). Thirty subjects comprising consultant orthopedic surgeons, orthopedic trainees, and nonsurgical staff positioned an acetabular component in a pelvic model using 3 different methods for guiding inclination and another 3 for guiding version.

Results: Using either a standard mechanical alignment guide (MAG) or a spirit level MAG technique eliminated outliers from target OI, while the freehand method resulted in 46.7% of measurements outside the OI target range. The spirit level MAG technique significantly outperformed the standard MAG technique in median unsigned deviation from target OI (0.8° vs 2.1°, P < .001). Either method of referencing the transverse acetabular ligament for version yielded lower deviations from target OA than the freehand method and fewer outliers from the ±5° target range. Surgical experience was not a significant factor for accurately achieving target OI and OA.

Conclusions: Even in an idealized in vitro model, a wide range of OI and OA is seen with the freehand technique of cup placement by subjects of all levels of surgical experience. Using either a standard MAG or a spirit level MAG reduces deviations in target OI, with the spirit level MAG method yielding the best accuracy. Using the transverse acetabular ligament to guide cup anteversion yields more accurate OA.

Keywords: Acetabular component positioning; Anteversion; Hip arthroplasty; Inclination.

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Figures

Figure 1
Figure 1
Schematic showing operative inclination—defined as the angle between the acetabular axis and the sagittal plane of the pelvis.
Figure 2
Figure 2
Experimental setup. Photographs show the pelvic model mounted with the sagittal plane parallel to the floor, the transverse acetabular ligament (TAL) in situ, and a cup held in the acetabulum with a mechanical alignment guide (MAG) attached to the cup handle. (a) The standard mechanical MAG with its horizontal limb which was to be placed parallel to the floor. (b) The modified MAG with a spirit level which was to be leveled in 2 orthogonal planes.
Figure 3
Figure 3
Schematic showing operative anteversion—defined as the angle between the long axis of the patient and the acetabular axis as projected onto the sagittal plane.
Figure 4
Figure 4
Measuring cup inclination. A digital inclinometer was placed on the long axis of the cup handle to measure cup inclination.
Figure 5
Figure 5
Digital image processing—determining the anteversion angle using a digital image processing software software.
Figure 6
Figure 6
Calibration of the photographic system. A custom device was attached to the mechanical alignment guide to calibrate the photographic system for version measurements.
See this image and copyright information in PMC

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