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.
In this retrospective study, we report a series of 80 Arpe prostheses for trapeziometacarpal osteoarthritis in 63 patients. Twenty-seven prostheses (20 patients) were lost to follow-up. Twenty-one were revised, eight of them during the first year after operation. The calculated cumulated implant survival rate was 85% at 10 years but could be lower due to the lack of information on the patients lost to follow-up. The number of complications due to technical errors was high; but after we had done 30 cases, the number of early revisions decreased markedly. At follow-up, 23 of 32 thumbs were totally free of pain, and the patients were satisfied with 31 thumbs. We conclude that the implant survival declines progressively in the long run, with a survival rate of 80% after 15 years of follow-up and a further decline thereafter. We also found that this surgery was difficult to master. We advise selecting this implant for thumb trapeziometacarpal osteoarthritis with caution. Level of evidence: IV
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