A RANDOMISED CONTROLLED STUDY INVESTIGATING THE EFFECT OF PATIENT PELVIC POSITIONING ON RADIOLOGICAL ACETABULAR INCLINATION DURING TOTAL HIP ARTHROPLASTY (THA)

Introduction

Radiological Inclination (RI) is defined as the angle formed between the acetabular axis and the longitudinal axis when projected onto the coronal plane. Higher RI angles are associated with adverse outcomes.

Methods

Primary aim: to investigate the effect of adjusting patient pelvic position in the transverse plane by using a ‘head-down’ (HD) operating table position. This was to determine, when aiming for 35° Apparent Operative Inclination (AOI), which operating table position most accurately achieved a target post-operative RI of 42°.

N=270. Patients were randomised to one of three possible operating table positions:

1. 0°HD (Horizontal),

2. 7°HD, or

3. Y°HD (Patient Specific Table Position)

Operating table position was controlled using a digital inclinometer. RI was measured using EBRA software.

Results

0° HD:Range 32.9–61.7°,Mean 47.1°,Mean deviation from target 5.8°

7° HD:Range 24.0–53.8°,Mean 41.0°,Mean deviation from target 4.2°

Y° HD:Range 30.6–54.8°,Mean 43.3°,Mean deviation from target 3.9°

ANOVA: Significant differences in mean deviation from target RI between both the 0°HD/7°HD table positions (p=0.002) and the 0°HD/Y°HD table positions (p<0.001). Though the mean deviation from target RI was lower for the patient specific HD table position (3.9°) compared to the 7° HD table position (4.2°),this did not obtain significance (p=0.562).

Discussion

When aiming for 42° RI, both the 7°HD table position and Patient Specific HD table position provided a narrower RI range, more desirable mean RI and statistically improved mean deviation from target RI when compared to the 0°HD table position.

Conclusion

When aiming for 35° AOI in order to obtain a target RI of 42°, the surgeon should avoid pelvic adduction by considering a ‘head down’ operating table tilt.