Aims: The aims of this prospective study was to elucidate, how the high tibial opening wedge osteotomy (OW-HTO) corrected the varus angle of the lower extremity to the desired valgus angle in arthrotic knee joint, and what are the typical complications concerning this operation method. Methods: Twenty-one patients were operated on by using the operation technique (Puddu 1998) from September 1999 to August 2000. Results: The mean preoperative femoro-tibial varus-angle of the þrst 21 patients was 1.4. degrees, immediate postoperative valgus-angle was 7.1 degrees and at the latest follow-up, the valgus angle was 5.6 degrees, respectively.

In 16 of these 21 patients the healing was uneventful. Five patients sustained complications. Three patients had fracture of the opposite tibial lateral cortex peroperatively. Two of these fractures healed without complication. One of these patients needed total knee arthroplasty later on because of pseudoarthrosis and loss of OW-HTO correction angle at the osteotomy site. Two patients sustained peroperative þssural fracture up to the lateral tibial joint articulation surface. These fractures healed uneventfully. Conclusion: A group of young, active heavy patients sustaining varus gonarthro-sis are candidates for HTO. After promising results of these 21 OW-HTO operations, we have operated 34 more patients. Complication rate has dropped because of better operative experience. However, OW-HTO is a sensitive operation with itñs possible complications. In experienced hands it is reliable and good operation. Also we have to remember, that this operation allow patients to keep their own knee joint with itñs normal kinesiology.