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Purpose: In total hip arthroplasty (THA), the functional anatomy of the spinopelvic unit should be taken into account to provide the correct functional positioning of the implant. The relationship between the spine and the pelvis in the sagittal plane is represented by pelvic tilt (PT). The sacral slope (SS) has been proposed as a more reliable parameter than the anterior pelvic plane (APP) to express the PT. This study investigated the relationship between the APP and the SS; and the relationship between the APP and the SS, respectively, with the postoperative acetabular orientation. Methods: 45 patients undergoing primary THA were prospectively enrolled. The EOS 2D/3D system was used to perform the radiographic evaluation before and 3 months after surgery. The following parameters were measured in both standing and sitting position: SS, APP, acetabular anteversion (AA) and inclination (AI). Results: The SS values did not show any correlation with the values of the APP angle. The changes of the SS in the transition from the standing to the sitting position significantly correlated with the changes of the AA (r = −0.61; p < 0.0001). A weak correlation was found between the APP angle and the AA in standing position (r = −0.35; p = 0.02). Conclusions: The SS accurately expresses the functional orientation of the pelvis in the sagittal plane, and the functional orientation of the cup after hip replacement. Therefore, SS could be taken into account by navigation systems in order to achieve a patient-specific functional position of the acetabular cup. [ABSTRACT FROM AUTHOR]

Introduction: The pelvis rotates simultaneously around both hips along sagittal, frontal and transversal planes and its kinematics change in patients after total hip arthroplasty (THA). Consequently, it is reasonable to expect different pelvic kinematic profiles in bilateral or unilateral THA. Therefore, the aim of this study was to compare pelvic kinematics in patients with bilateral or unilateral THA. Methods: 40 patients undergoing bilateral (n = 20) or unilateral (n = 20) THA were evaluated for pelvic kinematics during standing and walking tasks using an optoelectronic system. Mean pelvic orientation was assessed during standing, whereas the Gait Variable Score (GVS), maximum and minimum peaks, range and values of pelvic tilt, obliquity and rotation during Heel-Strike and Toe-Off phases of gait cycle were calculated during walking. Data were collected the day before and at seven days after surgery. Results: At baseline, no between-group differences were found. At 7 days, GVS for pelvic tilt (p = 0.029) and rotation (p = 0.046) were closer to normative data in bilateral patients, who also revealed lower maximum peak of anterior tilt (p = 0.013) and lower range of pelvic tilt during gait (p = 0.031) with respect to unilateral cases. No between-group differences were found for pelvic orientation during standing at any time-point. Conclusions: Bilateral patients revealed more physiological pelvic kinematics than unilateral cases. These findings underline the advantage of patients undergoing 1-stage bilateral THA and may be helpful in selecting personalised rehabilitative approaches. [ABSTRACT FROM AUTHOR]