[Computer-assisted total knee replacement (TKR) using Orthopilot navigation system].

OBJECTIVE: Reproducible, precise implantation of a bicondylar knee prosthesis considering size of implant, axial conditions in coronal and sagittal planes, rotation, and ligament tension in extension and flexion. INDICATIONS: Progressive painful gonarthrosis, when conservative treatment is no longer an option. Revision of unicondylar prosthesis. CONTRAINDICATIONS: General contraindications to bicondylar knee replacement. Revision after bicondylar replacement. Severe limitation of hip joint mobility, e.g., after arthrodesis of the hip joint or ipsilateral hip joint ankylosis. Morbid obesity. SURGICAL TECHNIQUE: Approach to the knee joint for alloarthroplasty. Placement of the screws and fixation of the infrared reflectors at femur and tibia. After adjustment of the double camera, collection of kinematic data via standardized motion patterns and identification of predetermined anatomic landmarks at the knee and ankle joint. By means of this data, controlled resection of the tibia, determination of the ligament tension in extension and flexion, planning of the femoral osteotomies, controlled distal resection of the femur. Following intraoperative verification of the distal femur resection, navigation of the position of the femur to complete femoral resection. Placement of the trial components, determination of the tibial onlay thickness, adjustment of the rotation of the tibial component, and final preparation of the tibial shaft. Preparation of the patella by resection of osteophytes, denervation, and possibly onlay patellar resection using a saw. Finally, implantation of the tibial component (cemented or noncemented), the tibial onlay, the femoral component (cemented or noncemented), and possibly cementation of the patellar onlay. After hardening, control of knee movement in straight position and wound closure in layers. POSTOPERATIVE MANAGEMENT: Early functional treatment using continuous passive motion device. Pain-adapted increase of weight bearing. Low-molecular-weight heparin for 5-6 weeks.
RESULTS: Meanwhile, several studies have demonstrated that computer navigation helps to provide more accuracy in implant positioning, compared with conventional techniques in total knee replacement. Long-term survival of the implants promises to be superior after physiological leg axis restoration. Own results: 100 consecutive implantations: average duration of surgery 80 min, blood loss 360 ml, one deep infection (healed after early revision), one arthrofibrosis requiring revision surgery, average range of motion on the day of discharge 110 degrees in flexion (90-120 degrees) and full extension, after 3 months average 125 degrees in flexion (90-140 degrees). No clinical signs of instability. Postoperative radiologic evaluation with standard radiographs of the knee joint in coronal and sagittal planes took place right after surgery and again after 3 months.