Objective: Facilitation of reduction and retention in LISS (Less Invasive Stabilizing System) plate osteosynthesis of fractures of the distal femur by application of the large AO distractor.
Indications: Any distal femoral fracture suited to LISS plate osteosynthesis.
Contraindications: Distraction can lead to a pullout of the Schanz screws in patients with pronounced osteoporosis.
Surgical technique: Supine. Normal LISS osteosynthesis with lateral or parapatellar approaches. Insertion of one Schanz screw proximal to the end of the plate through a stab incision. Introduction of the LISS plate in the usual fashion and insertion of a second Schanz screw into plate hole "A", parallel to the joint. Assembly of the distractor onto the Schanz screws, distraction of the femur to the correct length and correction of varus/valgus alignment with the aid of the cable method, as well as correction of ante- and retrocurvature by insertion of an additional Schanz screw at the anterior aspect. At least two locking head screws should be inserted into the plate holes both proximally and distally. Removal of the AO distractor. Assembly of aiming guide and insertion of further screws into additional plate holes using the guide sleeve.
Results: Between May 1998 and September 2001, a total of 42 patients had their distal femoral fractures stabilized by LISS. The AO distractor was used from the 18th case onward. A time saving of approximately 13% was estimated, taking the learning curve of the LISS system into consideration. Three of 42 fractures showed relevant postoperative varus or valgus malalignment. No rotational malalignment was found. An effect of the LISS tractor on the incidence of malalignment could not be found with the limited number of cases examined; however, malalignment was correlated well with the rates found in literature for distal femoral fractures.