The sagittal orientation of the pelvis commonly called pelvic tilt has an effect on the orientation of the cup in total hip arthroplasty (THA). Pelvic tilt is different between individuals and changes during activities of daily living. In particular the pelvic tilt in standing position should be considered during the planning of THA to adapt the target angles of the cup patient-specifically to minimise wear and the risk of dislocation. Methods to measure pelvic tilt require an additional step in the planning process, may be time consuming and require additional devices or x-ray imaging.

In this study the relationship between three functional parameters describing the sagittal pelvic orientation in standing position and seven morphological parameters of the pelvis was investigated. Correlations might be used to estimate the pelvic tilt in standing position by the morphology of the pelvis in order to avoid additional measuring techniques of pelvic tilt in the planning process of THA. For 18 subjects a semi-automatic process was established to match a 3D-reconstruction of the pelvis from CT scans to orthogonal EOS imaging in standing position and to calculate the morphological and functional parameters of the pelvis subsequently.

The two strongest correlations of the linear correlation analysis were observed between morphological pelvic incidence and functional sacral slope (r = 0.78; p = 0.0001) and between morphological pubic symphysis-posterior superior iliac spines-ratio and functional tilt of anterior pelvic plane (r = −0.59; p = 0.0098). The results of this study suggest that patient-specific adjustments to the orientation of the cup in planning of THA without additional measurement of the sagittal pelvic orientation in standing position should be based on the correlation between morphological pelvic incidence and functional sacral slope.

Introduction: Restoration of neutral alignment of the leg is an important factor affecting the long-term results of total knee arthroplasty (TKA). Recent developments in computer-assisted surgery have focused on systems for improving TKA. To verify that computer assistance improves the leg alignment and the component orientation, we present a single center study with 1000 patients.

Materials and Methods: In a prospective study two groups of 500 patients each undergoing TKA had operations using either a computer-assisted image free navigation system or a conventional technique. Alignment of the leg and the orientation of components were determined on post-operative long-leg coronal and lateral films.

Results: The mechanical axis of the leg was significantly better in the computer-assisted group (97%, within ±3° varus/valgus) compared with the conventional group (78,5%, within ±3° varus/valgus). The coronal alignment of the femoral component was also more accurate in the computer-assisted group.

Discussion: Computer-assisted TKA gives a better correction of alignment of the leg and orientation of the components compared with the conventional technique. Potential benefits in the long-term outcome and functional improvement require further investigation.

Soft tissue management is a critical factor in total knee arthroplasty especially in valgus knees. The stepwise release has been based upon surgeon’s experience until now. Computer assisted surgery gained increasing scientific interest in recent times and allows the intraoperative measurement of leg axis and gap size in extension and flexion.

We therefore aimed to analyse the effect of the sequential lateral soft tissue release and the resulting change in the a.p. limb axis on the one hand and the tibiofemoral gaps on the other hand as well in extension as in flexion in 8 cadaveric knees. Measurements were obtained using a CT-free navigation system.

In extension the highest increase compared to the previous release step was found for the first (iliotibial band, p=0.002), second (popliteus muscle, p=0.0003), third (LCL, 0.007) and the sixth (entire PCL, p=0.001) release step. In 90° flexion all differences of the lateral release steps were statistically significant (p< 0.004). Massive progression of the lateral gap in flexion was found after the second (popliteus muscle, p=0.004) and third (LCL, 0.007) release step.

Computer assisted surgery allows to measure the effect of each release step of the sequential lateral release sequence and helps the surgeon to asses the result better.

Restoration of neutral alignment of the leg is an important factor affecting the long-term results of total knee arthroplasty (TKA). Recent developments in computer-assisted surgery have focused on systems for improving TKA.

In a prospective study two groups of 80 patients undergoing TKA had operations using either a computer-assisted navigation system or a conventional technique. Alignment of the leg and the orientation of components were determined on post-operative long-leg coronal and lateral films.

The mechanical axis of the leg was significantly better in the computer-assisted group (96%, within ±3° varus/valgus) compared with the conventional group (78%, within ±3° varus/valgus). The coronal alignment of the femoral component was also more accurate in the computer-assisted group.

Computer-assisted TKA gives a better correction of alignment of the leg and orientation of the components compared with the conventional technique. Potential benefits in the long-term outcome and functional improvement require further investigation.