Journal of orthopaedic trauma
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Review Comparative Study
Flexible fixation and fracture healing: do locked plating 'internal fixators' resemble external fixators?
External and internal fixators use bone screws that are locked to a plate or bar to prevent periosteal compression and associated impairment of blood supply. Both osteosynthesis techniques rely on secondary bone healing with callus formation with the exception of compression plating of simple, noncomminuted fractures. External fixation uses external bars for stabilization, whereas internal fixation is realized by subcutaneous placement of locking plates. ⋯ Biomechanically, they can be far stiffer than external fixators, because subcutaneous plates are located much closer to the bone surface than external fixator bars. External fixators have the advantage of being less expensive, highly flexible, and technically less demanding. They remain an integral part of orthopaedic surgery for emergent stabilization, for pediatric fractures, for definitive osteosynthesis in certain indications such as distal radius fractures, and for callus distraction.
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The development of far cortical locking (FCL) was motivated by a conundrum: locked plating constructs provide inherently rigid stabilization, yet they should facilitate biologic fixation and secondary bone healing that relies on flexible fixation to stimulate callus formation. Recent studies have confirmed that the high stiffness of standard locked plating constructs can suppress interfragmentary motion to a level that is insufficient to reliably promote secondary fracture healing by callus formation. Furthermore, rigid locking screws cause an uneven stress distribution that may lead to stress fracture at the end screw and stress shielding under the plate. ⋯ Finally, parallel interfragmentary motion by the S-shaped flexion of FCL screws promotes symmetric callus formation. In combination, these features of FCL constructs have been shown to induce more callus and to yield significantly stronger and more consistent healing compared with standard locked plating constructs. As such, FCL constructs function as true internal fixators by replicating the biomechanical behavior and biologic healing response of external fixators.
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Comparative Study
Surgical treatment of extra-articular or simple intra-articular distal tibial fractures: external fixation versus intramedullary nailing.
To compare intramedullary nailing (IMN) with external fixation (EF) in the treatment of tibial shaft fractures located within 5 cm of the ankle. ⋯ Distal extra-articular or simple intra-articular fractures can be treated with modern IMNs or nonbridging EF. Although functional results are similar, EF carries a significant greater risk of secondary interventions; based on these data, IMN is recommended.
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The high stiffness of periarticular locked plating constructs can suppress callus formation and fracture healing. Replacing standard locking screws with far cortical locking (FCL) screws can decrease construct stiffness and can improve fracture healing in diaphyseal plating constructs. However, FCL function has not been tested in conjunction with periarticular plating constructs in which FCL screws are confined to the diaphyseal segment. ⋯ The residual strength of surviving constructs was 4.9 ± 1.6 kN (LP group) and 5.3 ± 1.1 kN (FCL group, P = 0.73). In summary, FCL screws reduce stiffness, generate parallel interfragmentary motion, and retain the strength of a periarticular locked plating construct. Therefore, FCL fixation may be advisable for stiffness reduction of periarticular plating constructs to promote fracture healing by callus formation.