title: Internal fixation of intertrochanteric hip fractures: a clinical and biomechanical study.
abstract: One hundred seventy-three cases of intertrochanteric fractures treated by internal fixation are reviewed: 72 treated with the Jewett nail and 101 with the Richards compression hip screw. Both devices maintained adequate reduction in the majority of cases. Treatment failure: loss of fixation, symptomatic joint penetration, aseptic necrosis, malunion and nonunion occurred in 25% of the Jewett nail cases and 6% of the Richards screw cases. In vitro biomechanical studies demonstrate that the compression screw is subjected to less bending stress by acting as a lateral "tension band" in stable reductions and by allowing sliding, thus shortening the bending movement lever arm in unstable reductions. The compression hip screw is valuable in the treatment of intertrochanteric hip fractures. In stable conditions, it acts as a tension band producing more force transmission through the medial cortex, stressing the implant more in tension and less in bending. In unstable conditions with higher shearing forces, the device will shorten the lever arm, decreasing the bending moment, as well as avoiding penetration of the femoral head.
mesh_terms: D001696:Biomechanical Phenomena; D001858:Bone Nails; D001860:Bone Plates; D001863:Bone Screws; D005593:Fracture Fixation, Internal / Q000379:methods*; D006620:Hip Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D066298:In Vitro Techniques; D011183:Postoperative Complications; D011859:Radiography; D013314:Stress, Mechanical