[Opening-wedge osteotomy of the proximal tibia].

PURPOSE OF THE STUDY: The aim of this study was to evaluate the accuracy of correction and short-term outcomes of treatment by opening-wedge tibial osteotomy with the use of allograft and a modified Puddu plate fixation.

MATERIAL: Between February 2001 and March 2003, 33 operations on 30 patients, at an average age of 54 years, with gonarthrosis and varus deformity were evaluated. Grade III arthritis was diagnosed in 24 knees (73 %) and grade II in nine knees (27 %).

METHODS: The preoperative planning as well as intraoperative correction were based on the limb mechanical axis, as shown on an X-ray image of the whole lower extemity. Tibial osteotomy was performed from the medial approach and the position was fixed, in contrast to the original method, with an allograft and a T-plate. The corrrection was planned so that the mechanical limb axis should intersect the articular space at 62 % of its length laterally. The limb was postoperatively immobilized for 4 weeks in a knee brace allowing walking. Limited weight bearing was recommended from the third week. The outcome of treatment was evaluated at 11 months of follow-up by the Lysholm scoring system.

RESULTS: Correction of the limb mechanical axis involved the axis intersecting the plane of the joint space on average at 60.2 % of its length, as against the planned 62 %; the average deviation from the planned correction was 2.1 degrees. Lysholm scores improved on average by 23 points. Improvement by 20 points was regarded as a good outcome and was achieved in 31 joints (94 %). Two joints (6 %) showed poor outcomes due to associated complications. The complications included a fissure of the lateral tibial plateau in one knee, failed stabilization with subsequent loss of correction and pseudoarthrosis development in one joint, prolonged healing with a partial loss of correction (5 degrees) in one patient, and superficial infection in one patient.

DISCUSSION: In patients with knee arthritis and varus deformity, the achievement of optimal correction of the mechanical limb axis is the prerequisite for a long-term good outcome. Optimal correction, as characterized by Puddu, is attained when the mechanical axis intersects the joint space at 62 % of its length laterally. Hernigou et al. define the hip-knee-ankle angle in the range of 183 degrees -186 degrees as an optimal postoperation correction. In our experience, osteotomy combined with our modification of fixation is an exact method for correcting the axis; in addition, it is simple and is associated with a low occurrence of postoperative complications. In view of a possible total knee arthroplasty, there is less disturbance in the tibial plateau-diaphysis alignment and the tibial tuberosity level is preserved.

CONCLUSIONS: Opening-wedge tibial osteotomy with the use of a Puddu plate and allograft in our modification is an effective, exact and simple method of correcting the lower extremity axis, and is associated with few complications. We do not recommend this method for interventions planned to achive corrections of more than 16 degrees, because these have a higher occurrence of complications. The use of allograft seems to have good prospects; another option for achieving large correction includes application of an LCP plate.