TomoFix Medial Distal Femur (MDF)

The goal of distal femur varus osteotomy is to shift the mechanical leg axis from the lateral to the medial compartment. There are various possibilities for surgical correction of valgus malalignment. The AO Knee Expert Group (KNEG) favors closing wedge osteotomy of the distal femur for valgus correction, because open wedge osteotomy on the lateral side causes significant morbidity due to tensioning of the iliotibial tract, and friction over the implant. The KNEG also found that distal femur opening wedge osteotomy did not show the same healing capacity as on the tibia and that bone grafting was necessary to avoid pseudarthrosis. Biomechanical testing confirmed superior stability of medial closing wedge techniques as compared to lateral open wedge techniques and favorable axial and torsional loading characteristics of an angular stable internal fixator, the TomoFix medial distal femur (MDF).
The TomoFix MDF features anatomically preshaped plates with a bending angle of 20°. If needed during the operation, this angle can be further bent by using the bending press. The plate profile is 4 mm. The TomoFix MDF is available in a left and right version. The head of the plate offers four isolated LCP holes for 5.0 mm locking head screws. The screw axes of these four LCP holes are converged by 2°. Through this alignment a cut-out of the screws can be prevented and the distance to the cruciate ligament is improved. The bolt angulation of 15° in the frontal plane enables use of longer screws and thus a more stable fixation. Bolt placement is easy and safe due to the anatomically adapted shape. The plate shaft features four standard 4.5/5.0 LCP combination holes which are shifted throughout the longitudinal axis. The end of the plate has a bullet nose for use of a MIO technique. Specific guiding blocks for the left and right plates help to insert the drill socket in the correct axis onto the plate.
The plate is inserted distally under the vastus medial muscle after screwing the threaded LCP drill guides into the four distal plate holes using the guiding block. The distal drill holes are oriented in a 20° angle inclination on the frontal plane to avoid a posterior perforation of locking head screws in the distal femur.
Biomechanical studies demonstrate that interfragmentary compression has a positive effect on bone healing. For this reason a lag screw is positioned in the dynamic compression unit directly above the osteotomy for compression of the osteotomy site.
The Patient can be mobilised as early as day one after surgery. Partial weight bearing is recommended for 6 weeks, active movement of the knee is encouraged. X-ray control after 6 weeks should demonstrate bony healing. Full weight bearing can be allowed in many cases after this time period, if the osteotomy site is still painful and bone healing is incomplete, weight bearing should be delayed for further 3–4 weeks.