In a prospective randomised clinical study acetabular components were implanted either freehand (n = 30) or using CT-based (n = 30) or imageless navigation (n = 30). The position of the component was determined post-operatively on CT scans of the pelvis. Following conventional freehand placement of the acetabular component, only 14 of the 30 were within the safe zone as defined by Lewinnek et al (40 degrees inclination sd 10 degrees ; 15 degrees anteversion sd 10 degrees ). After computer-assisted navigation 25 of 30 acetabular components (CT-based) and 28 of 30 components (imageless) were positioned within this limit (overall p < 0.001). No significant differences were observed between CT-based and imageless navigation (p = 0.23); both showed a significant reduction in variation of the position of the acetabular component compared with conventional freehand arthroplasty (p < 0.001). The duration of the operation was increased by eight minutes with imageless and by 17 minutes with CT-based navigation. Imageless navigation proved as reliable as that using CT in positioning the acetabular component.

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 degrees varus/valgus) compared with the conventional group (78%, within +/- 3 degrees 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.

Restoration of the mechanical leg axis and component positioning are crucial factors affecting long-term results in total knee arthroplasty (TKA). In a prospective study, 1,000 patients were operated on either using a CT-free navigation system or the conventional jig-based technique. Leg alignment and component orientation were determined on postoperative X-rays. The mechanical leg axis was significantly better in the computer-assisted group (95%, within +/-3 degrees varus/valgus) compared to the conventional group (74%, within +/-3 degrees varus/valgus) (P < 0.001). On average, the operating time was increased by 8 min in the computer-assisted group. No significant differences were seen between senior and younger surgeons regarding postoperative leg alignment and operating time. Computer-assisted TKA leads to a more accurate restoration of leg alignment and component orientation compared to the conventional jig-based technique. Potential benefits in long-term outcome and functional improvement require further investigation.

To minimize cutting errors, techniques and instruments are needed which enable a more stable fixation of the cutting blocks or even more appropriate preparation instruments. Using a computer-assisted technique, the surgeon is aware of cutting errors occurring at each point of the operation and will therefore be able to correct these errors during surgery, while he is not aware of those errors with the conventional TKA technique.

The results of this short-term follow-up study show that sports activity after total hip resurfacing surgery is still possible. Physical activity level increased with a shift toward low-impact sports. Duration of sports participation increased. High-impact sports activities decreased. These findings can be important for the decision-making process for hip surgery and should be communicated to the patient.

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Restoration of the mechanical limb axis and accurate component orientation are two major factors affecting the long-term results after total knee replacement (TKR). Different navigation systems are available to improve the outcome. Image-based systems require pre-operative CT scans, while non-image-based systems gain all necessary information intra-operatively during a registration process. We studied 130 patients who received a TKR either using the CT-based (Knee 1.1) or the CT-free module (CT-free Knee 1.0) of the BrainLAB Vector-Vision Navigation System. Post-operative leg alignment and component orientation was determined on long-leg coronal and lateral X-rays. Sixty of 65 patients in the CT-based group and 63/65 patients in the CT-free group had a post-operative leg axis between 3 degrees varus/valgus. No significant differences were found for varus/valgus orientation of the femoral and tibial components.

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