Minimally invasive fracture stabilization of distal femoral fractures with the LISS: a prospective multicenter study. Results of a clinical study with special emphasis on difficult cases.

The LISS-DF (Less invasive stabilization system-distal femur) is a new type of implant system for the treatment of distal femoral fractures according to the principles of "Minimally Invasive Surgery". A plate, pre-contoured to the anatomy, is inserted through a minimally invasive incision into the epiperiosteal space by means of an aiming device after indirect, closed fracture reduction. The implant is stabilized by insertion of screws which lock into the plate holes and prevent tilting. This is performed with the aid of an aiming device and through stab incisions. It is not necessary for a large area to be exposed at the fracture site. As part of an AO prospective multicenter study, the new system was applied to 112 patients with 116 fractures. The time to follow-up was on average 13.7 months (minimum 7 months, maximum 33 months). Fractures treated were distal femoral shaft and supracondylar femoral fractures. Eight patients died during the study of causes unrelated to the implant. Of the remaining 104 patients with 107 fractures, 96 patients with 99 fractures were available for complete follow-up (93% follow-up rate). In 90% of all cases treated and followed up, the fracture had consolidated during the period of observation. Twenty-three revision operations were necessary in 21 patients. In two cases, implant failure occurred as the result of a pseudarthrosis. The complications can be attributed in nearly all cases to the severity of the trauma and/or a lack of experience when applying the new style implant to a wider range of indications. The results of the study show that with a sound knowledge of the operative technique and careful preoperative planning this system represents an excellent, safe procedure for the treatment of almost all distal femoral fracture types including periprosthetic fractures of the distal femur. There is generally no need for primary cancellous bone grafting.