Aim: Can comparable results be obtained regarding the postoperative improvement of range of motion using ßexionosteotomy alone in comparison to the three-dimensional corrective osteotomy. Material and Methods: 16 patients after SCFE were analyzed (7 female, 9 male). A computer program for simulation of movement and osteotomy developed by the authors, served for study execution. According to 3D-reconstruction of the computer tomography data the physiological range was determined by ßexion, abduction and internal rotation. The three-dimensional osteotomy was compared with the onedimensional ßexionosteotomy. Both inter-trochanteric osteotomy techniques were simulated and the improvements of the movement range were assessed and compared. Results: The average slipping and thus correction angles measured inferior 25.5¡ (range: 7.5¡–51.0¡) and posterior 52.0¡ (range: 29.0¡– 78.5¡). After the simulation of osteotomy by Southwick the angle of ßexion was 61.3¡ (improvement: 41.4¡), of abduction 60.3¡ (improvement: 42.9¡) and interior rotation of 70.1¡ (improvement: 52.6¡). The ßexionsosteotomy after Grifþth achieved a ßexion of 66.7¡ (improvement: 46.8¡), an abduction of 41.1¡ (improvement: 23.7¡) and an internal rotation of 57.4¡ (improvement: 40.0¡). Conclusion: The improvement of the free movement range after ßexion osteotomy is comparable, with three-dimensional osteotomy after Southwick with the exception of the abduction angle.

The most common reason for possible complications after total hip replacement (THR) surgery is improper positioning of the implant components within the hip joint. Systems for computer assisted planning and navigation during THR have been developed. However, these established modules focus on the acetabular implant component only; disrespecting the fact that proper implant functioning relies upon correct placement of both components relative to each other. Therefore, we developed an extension to the existing CT-based SurgiGATE-Prosthetics system (Medivision, Oberdorf, Switzerland) for planning and placing of the acetabular component to give the surgeon a tool, which can help him/her to also plan and insert the femoral implant.

Preoperatively, the appropriate size and position as well as the orientation of both implants components were planned. Following navigated cup placement a dynamic reference base (DRB) was fixed to the thighbone and the registration procedure was executed. For the preparation of the femoral cavity a modular PPF rasp system (Biomet-Merck, Darmstadt, Germany) was developed. All surgical action was visualised graphically within the patient’s image data. In addition, the surgeon was provided with real-time information about the depth of tool insertion, antetorsion angle, varus/valgus deviation, and the postoperative change in leg length and lateralisation of the hip joint.

After extensive validation and accuracy analyses performed on plastic models the presented system was used during one operation. An extended clinical study is currently being started.

We expect that the developed application will help the surgeon to better plan the appropriate size and position of the both parts of a hip endoprosthesis and will supply intraoperative feedback of the position of the surgical instruments relative to the patients’ anatomy and to the preoperative plan. Safer and more accurate placement of the implants components during free-hand THR surgery may be expected from this technology.