[Mini-subvastus approach for total knee replacement]

Total knee replacement in minimally invasive technique without any trauma to the extensor apparatus and with soft-tissue-referenced bone resections. Only the subvastus approach preserves the integrity of the extensor apparatus and has therefore been modified to become a minimally invasive technique with a shorter skin incision and lateralization instead of eversion of the patella. Soft-tissue balancing is done through this direct anterior approach.

Mild to moderate varus osteoarthritis of the knee up to 15 degrees of malalignment, mild and passively correctable valgus osteoarthritis of the knee up to 10 degrees of malalignment.

Severe, contract varus osteoarthritis of the knee, severe and moderate, contract valgus osteoarthritis of the knee, severe obesity, exceptionally muscular patients, decreased skin perfusion.

Central skin incision from the superior pole of the patella to the tibial tubercle. Exposure of the medial retinaculum and mobilization of the vastus medialis muscle subcutaneously. Incision of the medial retinaculum and blunt separation of the vastus medialis muscle from the intermuscular septum. Lateralization of the patella and flexion of the knee joint. Resection of the tibia perpendicular to the diaphysis. Adjustment of the anteroposterior (AP) resection block at the level of the anterior femoral cortex and of rotation by applying equal tension to the collateral ligaments. Balancing of soft-tissue tension in flexion gap by release, if necessary. After AP resection fixation of distal resection block in planned valgus angle. Balancing of soft-tissue tension in extension gap by release, if necessary. After distal femur resection facet resection, adaptation of posterior femoral condyles, and implantation of prosthesis. Check on stability and range of motion. Wound closure.

Full weight bearing from the 1st postoperative day, CPM (continuous passive motion) with up to 90 degrees flexion with peridural anesthesia as tolerated, stair climbing starting on the 7th postoperative day.

100 patients were randomized to total knee replacement via a parapatellar or subvastus approach. Radiologically, there were no differences in operative precision or leg alignment. Patients treated minimally invasively suffered less pain and achieved a higher flexion of 110 degrees versus 95 degrees 6 weeks postoperatively. However, there were two cases of delayed wound healing in this group. The surgical technique is demanding and the operating time is longer. Long-term results are still missing.