Affiliations: [a] Department of Orthopaedic Surgery, University of North Texas Health Science Center, Fort Worth, TX, USA | [b] Department of Materials Science and Engineering, University of North Texas, Denton, TX, USA | [c] Department of Orthopaedic Surgery, John Peter Smith Hospital, Fort Worth, TX, USA
Correspondence:
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Corresponding author: Victor Kosmopoulos, Department of Orthopaedic Surgery, University of North Texas Health Science Center, 3400 Camp Bowie Blvd, Fort Worth, TX 76107, USA. Tel.: +1 817 735 0488; E-mail: victor.kosmopoulos@yahoo.com.
Abstract: Background:A smaller humerus in some patients makes the use of a large fragment fixation plate difficult. Dual small fragment plate constructs have been suggested as an alternative. Objective:This study compares the biomechanical performance of three single and one dual plate construct for mid-diaphyseal humeral fracture fixation. Methods:Five humeral shaft finite element models (1 intact and 4 fixation) were loaded in torsion, compression, posterior-anterior (PA) bending, and lateral-medial (LM) bending. A comminuted fracture was simulated by a 1-cm gap. Fracture fixation was modelled by: (A) 4.5-mm 9-hole large fragment plate (wide), (B) 4.5-mm 9-hole large fragment plate (narrow), (C) 3.5-mm 9-hole small fragment plate, and (D) one 3.5-mm 9-hole small fragment plate and one 3.5-mm 7-hole small fragment plate. Results:Model A showed the best outcomes in torsion and PA bending, whereas Model D outperformed the others in compression and LM bending. Stress concentrations were located near and around the unused screw holes for each of the single plate models and at the neck of the screws just below the plates for all the models studied. Other than in PA bending, Model D showed the best overall screw-to-screw load sharing characteristics. Conclusion:The results support using a dual small fragment locking plate construct as an alternative in cases where crutch weight-bearing (compression) tolerance may be important and where anatomy limits the size of the humerus bone segment available for large fragment plate fixation.
Keywords: Finite element analysis, internal fracture fixation, mechanical stress, bone plates, humerus
