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:. 0°HD (Horizontal),. 7°HD, or. 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

Aims

Appropriate acetabular component placement has been proposed for prevention of postoperative dislocation in total hip arthroplasty (THA). Manual placements often cause outliers in spite of attempts to insert the component within the intended safe zone; therefore, some surgeons routinely evaluate intraoperative pelvic radiographs to exclude excessive acetabular component malposition. However, their evaluation is often ambiguous in case of the tilted or rotated pelvic position. The purpose of this study was to develop the computational analysis to digitalize the acetabular component orientation regardless of the pelvic tilt or rotation.

Introduction. Radiological inclination (RI) is determined in part by operative inclination (OI), which is defined as the angle between the cup axis or handle and the sagittal plane. In lateral decubitus the theatre floor becomes a surrogate for the pelvic sagittal plane. Critically at the time of cup insertion if the pelvic sagittal plane is not parallel to the floor either because the upper hemi pelvis is internally rotated or adducted, RI can be much greater than expected. We have developed a simple Pelvic Orientation Device (POD) to help achieve a horizontal pelvic sagittal plane. The POD is a 3-sided square with flat footplates that are placed against the patient's posterior superior iliac spines following initial positioning (figure 1). A digital inclinometer is then placed parallel and perpendicular to the patient to give readings of internal rotation and adduction, which can then be corrected. Methods. A model representing the posterior aspect of the pelvis was created. This permitted known movement in two planes to simulate internal rotation and adduction of the upper hemi pelvis, with 15 known pre-set positions. 20 participants tested the POD in 5 random, blinded position combinations, providing 200 readings. The accuracy was measured by subtracting each reading from the known value. Results. 2 statistical outliers were identified and removed from analysis. The mean adduction error was 0.73°. For internal rotation, the mean error was −0.03°. Accuracy within 2.0° was achieved in 176 of 190 (93%) of readings (Table 1). The maximum error was 3.6° for internal rotation and 3.1° for adduction. Conclusion. In a model pelvis the POD provided an accurate and reproducible method of achieving a horizontal sagittal plane. Applied clinically, this simple tool has the potential to reduce the high values of RI sometimes seen following THA in lateral decubitus. For any figures and tables, please contact the authors directly

Aims

This study aimed to evaluate the accuracy of implant placement with robotic-arm assisted total hip arthroplasty (THA) in patients with developmental dysplasia of the hip (DDH).