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

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.

Achieving Precise Cup Positioning in Direct Anterior Total Hip Arthroplasty: A Narrative Review

“…Using an inclinometer instead of mechanical guides may be more accurate. While some studies found superior results compared to freehand positioning and traditional mechanical guides, especially regarding achieving the targeted inclination and reducing outliers, other studies found no differences [ 54 , 71 ].…”

“…Alternatively, a spirit level instead of a simple rod can be used. These methods showed superior results to freehand positioning [ 54 ].…”

Instability in Total Hip Arthroplasty

“…Additionally, inconsistencies in the size and shape of the operating room may alter the surgeon's perception of patient orientation [90]. Therefore an alignment rod attached to the insertion handle of the cup has proven to be more accurate in comparison to free hand cup placement [91]. This rod allows the surgeon to more appropriately align the guide to visualize anteversion and inclination based on the floor and longitudinal axis of the patient.…”

Determining the orientation of acetabular prosthesis in total hip arthroplasty by refering to the anatomical landmarker of acetabular notches

“…These methods are of limited guidance value in the operation. With respect to the anteversion of the acetabular cup, many scholars believed that satisfactory anteversion could be obtain when the inferior edge of the acetabular cup was placed parallel to the transverse acetabular ligament 5 – 7 . However, not all of the transverse acetabular ligament could be separated in the operation, especially Beverland grade four 8 .…”