Biomechanical evaluation of the fixation methods for transcondylar fracture of the humerus: ONI plate versus conventional plates and screws

We biomechanically evaluated the bone fixation rigidity of an ONI plate (Group I) during fixation of experimentally created transcondylar humerus fractures in cadaveric elbows, which are the most frequently observed humeral fractures in the elderly, and compared it with the rigidity achieved by 3 conventional fixation methods: an LCP reconstruction plate 3.5 using a locking mechanism (Group II), a conventional reconstruction plate 3.5 (CRP) with a cannulated cancellous screw (Group III), and a CRP with 2 cannulated cancellous screws (CS) in a crisscross orientation (Group IV). In the axial loading test, the mean failure loads were: Group I, 98.9 ± 32.6; Group II, 108.5 ± 27.2; Group III, 50.0 ± 7.5; and Group IV, 34.5 ± 12.2 (N). Group I fixations failed at a significantly higher load than those of Groups III and IV (p < 0.05). In the extension loading test, the mean failure loads were: Group I, 34.0 ± 12.4; Group II, 51.0 ± 14.8; Group III, 19.3 ± 6.0; and Group IV, 14.7 ± 3.1 (N). Group IV fixations showed a significantly lower failure load than those of Group I (p < 0.05). The fixation rigidities against mechanical loading by the ONI plate and LCP plate were comparable. These results suggested that an ONI system might be superior to the CRP and CS method, and comparable to the LCP method in terms of fixation rigidity for distal humerus fractures.