An In Vitro Biomechanical Comparison Between Prototype Tapered Shaft Cortical Bone Screws and AO Cortical Bone Screws for an Equine Metacarpal Dynamic Compression Plate Fixation of Osteotomized Equine Third Metacarpal Bones

• Published in: Veterinary surgery 2006-10, Vol.35 (7), p.634-642
• Main Authors: SOD, GARY A., HUBERT, JEREMY D., MARTIN, GEORGE S., GILL, MARJORIE S.
• Format: Article
• Language: English
• Subjects: Animals; Biochemistry; Biomechanical Phenomena; Bone Plates - standards; Bone Plates - veterinary; Bone Screws - standards; Bone Screws - veterinary; Bone surgery; Cadaver; Comparative analysis; Compressive Strength; Fracture Fixation, Internal - methods; Fracture Fixation, Internal - standards; Fracture Fixation, Internal - veterinary; Fractures, Bone - surgery; Fractures, Bone - veterinary; Horses; Internal Fixators - standards; Internal Fixators - veterinary; Metacarpal Bones - surgery; Orthopedics; Osteotomy - methods; Osteotomy - veterinary; Prototypes; Random Allocation; Stress, Mechanical; Torsion Abnormality; Veterinary services
• ISSN: 0161-3499; 1532-950X
• DOI: 10.1111/j.1532-950X.2006.00201.x

Objectives— To compare biomechanical properties of a prototype 5.5 mm tapered shaft cortical screw (TSS) and 5.5 mm AO cortical screw for an equine third metacarpal dynamic compression plate (EM‐DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. Study Design— Paired in vitro biomechanical testing of cadaveric equine MC3 with a mid‐diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. Animal Population— Adult equine cadaveric MC3 bones (n=12 pairs). Methods— Twelve pairs of equine MC3 were divided into 3 groups (4 pairs each) for (1) 4‐point bending single cycle to failure testing, (2) 4‐point bending cyclic fatigue testing, and (3) torsional single cycle to failure testing. An EM‐DCP (10‐hole, 4.5 mm) was applied to the dorsal surface of each, mid‐diaphyseal osteotomized, MC3 pair. For each MC3 bone pair, 1 was randomly chosen to have the EM‐DCP secured with four 5.5 mm TSS (2 screws proximal and distal to the osteotomy; TSS construct), two 5.5 mm AO cortical screws (most proximal and distal holes in the plate) and four 4.5 mm AO cortical screws in the remaining holes. The control construct (AO construct) had four 5.5 mm AO cortical screws to secure the EM‐DCP in the 2 holes proximal and distal to the osteotomy in the contralateral bone from each pair. The remaining holes of the EM‐DCP were filled with two 5.5 mm AO cortical screws (most proximal and distal holes in the plate) and four 4.5 mm AO cortical screws. All plates and screws were applied using standard AO/ASIF techniques. Mean test variable values for each method were compared using a paired t‐test within each group. Significance was set at P