After a short historical review of locking bone plates since their inception more than a century ago to the success of the concept less than 15 years ago with today's plates, the authors present the main locking mechanisms in use. In the two broad categories - plates with fixed angulation and those with variable angulation - the screw head is locked in the plate with a locknut by screwing in a threaded chamber on the plate or by screwing through an adapted ring. The authors then provide a concrete explanation, based on simple mechanical models, of the fundamental differences between conventional bone plates and locking plates and why a locking screw system presents greater resistance at disassembly, detailing the role played by the position and number of screws. The advantages of epiphyseal fixation are then discussed, including in cases of mediocre-quality bone. For teaching purposes, the authors also present assembly with an apple fixed with five locking screws withstanding a 47-kg axial load with no resulting disassembly. The principles of plate placement are detailed for both the epiphysis and diaphysis, including the number and position of screws and respect of the soft tissues, with the greatest success assured by the minimally invasive and even percutaneous techniques. The authors then present the advantages of locking plates in fixation of periprosthetic fractures where conventional osteosynthesis often encounters limited success. Based on simplified theoretical cases, the economic impact in France of this type of implant is discussed, showing that on average it accounts for less than 10% of the overall cost of this pathology to society. Finally, the possible problems of material ablation are discussed as well as the means to remediate these problems.

IV; retrospective cohort study.

IV, cohort study.

No abstract

Prospective cohort study.

The traumatic floating knee in adults (FK) is a combined injury of the lower limb defined by ipsilateral fractures of the tibia and femur. The first publications emphasized the severity of injuries, the bad results after conservative treatment, the most severe functional outcome in case of articular fracture and the frequency of associated cruciate ligament injuries. The surgical management of FK has been highly modified according the improvement of the fracture fixation devices and the operative techniques. This retrospective multicentric observational study included 172 adults with a FK injury admitted in emergency in 5 different level I or II trauma centers. All the patients data were collected on an anonymized database. Results were evaluated by the overall clinical Karlström’s score at latest follow-up. Fracture union was assessed on X-rays when at least 3 out of 4 cortices were in continuity in two different radiological planes. A statistical analysis was performed by a logistic regression method. Despite some limitations, this study confirms the general and local severity of this high-energy trauma, mainly occurring in young people around the third decade. A special effort should lead to a better initial diagnosis of associated ligamentous injury: a tear of PCL can be suspected on a lateral-ray view and a testing of the knee should be systematically performed after fixation of the fracture under anesthesia. Secondary MRI assessment is sometimes difficult to interpret because of hardware artifacts. The timing of fracture fixation is discussed on a case by case basis. However, a first femoral fixation is recommended except in cases of tibia fracture with major soft tissue lesion or leg ischemia requiring the tibia fixation first. Also a tibia stabilized facilitates the reduction and fixation of a complex distal femur fracture. The dual nailing remains so far for us the best treatment in Fraser I FK. Further prospective studies are needed to validate treatment algorithms, best fixation techniques in order to decrease the rate of complication and improve the functional outcome of floating knee injuries.

IV.

Fractures of the distal femur remain a daunting challenge. Since 1970, operative treatment has been recommended. Unfortunately, it is fraught with complications, and techniques have been developed to limit incidence of non-union, infection and stiffness. A soft-tissue friendly approach is the key point, with minimally invasive surgery as the ultimate goal: its biological and anatomical advantages have been demonstrated, but clinical studies have been less convincing, being based on historical series. At present, retrograde nailing and minimally invasive percutaneous plate osteosynthesis (ideally by locking plate) are the two main techniques. Unfortunately, reports tend to compare implants rather than operative techniques, hindering solid conclusions. Lastly, the delineation of "distal femur fracture" is quite variable, sometimes situated well above the AO epiphyseal square. Meta-analyses find almost no difference between the two implants in minimally invasive procedures. The main advantage of the plate is its versatility, whereas nailing can be impossible in case of certain hip or knee prostheses, compound articular fracture or medullary canal obstruction by fixation material (nail, stem, screw, etc.). The role of arthroscopy is limited. Only a few case reports describe its use in reduction of epiphyseal fracture. In the last analysis, the surgeon's experience is more relevant to outcome than any particular implant.