Reducing variability in apparent operative inclination during total hip arthroplasty: findings of a randomised controlled trial

Abstract

Aims:

To determine which of 3 methods of cup insertion most accurately achieved a target apparent operative inclination (AOI) of 35° ± 2.5°: (1) Freehand; (2) Modified Mechanical Alignment Guide (MAG); or (3) Digital Inclinometer assisted.

Methods:

Using a cementless cup via a posterior approach in lateral decubitus 270 participants were recruited, with 90 randomised to each method. The primary outcome was the unsigned deviation from target AOI. The digital inclinometer was used to measure AOI in all cases, though the surgeon remained blinded to the reading intraoperatively for both the Freehand and MAG methods.

Results:

Mean deviation from target AOI for the Freehand, Modified 35° MAG and Digital Inclinometer techniques was 2.9°, 1.8° and 1.3° respectively.

When comparing mean deviation from target AOI, statistically significant differences between the Freehand / Inclinometer groups (p < 0.001), the Freehand / Modified 35° MAG groups (p < 0.001) and the Digital Inclinometer / Modified 35° MAG groups (p < 0.023) were evident.

The Digital Inclinometer technique enabled the surgeon to achieve a target AOI of 35° ± 2.5° in 88% of cases, compared to 71% of Modified 35° MAG cases and only 51% of Freehand cases.

Discussion:

The Digital Inclinometer and the Modified 35° MAG techniques were both more accurate than the Freehand technique, with the Digital Inclinometer technique proving most accurate overall.

Radiographic inclination (RI) is also influenced by operative anteversion; however, the greatest source of error with respect to RI occurs when the pelvic sagittal plane is not horizontal at the time of acetabular component insertion.

Clinical Trial Protocol number: NCT01831401

Keywords

Acetabular component orientation apparent operative inclination digital inclinometer pelvic sagittal plane total hip arthroplasty

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References

Bhaskar

Rajpura

Board

. Current concepts in acetabular positioning in total hip arthroplasty. Indian J Orthop 2017; 51: 386–396.

Murray

. The definition and measurement of acetabular orientation. J Bone Joint Surg Br 1993; 75: 228–232.

Wan

Malik

Jaramaz

et al . Imaging and navigation measurement of acetabular component position in THA. Clin Orthop Relat Res 2009; 467: 32–42.

Archbold

Mockford

Molloy

et al . The transverse acetabular ligament: an aid to orientation of the acetabular component during primary total hip replacement: a preliminary study of 1000 cases investigating postoperative stability. J Bone Joint Surg Br 2006; 88: 883–886.

Beverland

O’Neill

Rutherford

et al . Placement of the acetabular component. Bone Joint J 2016; 98(1 Suppl A): 37–43.

Hill

Gibson

Pagoti

et al . Photographic measurement of the inclination of the acetabular component in total hip replacement using the posterior approach. J Bone Joint Surg Br 2010; 92: 1209–1214.

O’Neill

Magill

Hill

et al . Correction of pelvic adduction during total hip arthroplasty reduces variability in radiographic acetabular inclination: findings of a randomised controlled trial. Hip Int 2018; 28: 240–246.

Barrack

Krempec

Clohisy

et al . Accuracy of acetabular component position in hip arthroplasty. J Bone Joint Surg Am 2013; 95: 1760–1768.

Honl

Schwieger

Salineros

et al . Orientation of the acetabular component. A comparison of five navigation systems with conventional surgical technique. J Bone Joint Surg Br 2006; 88: 1401–1405.