Carpal hyperextension is a common injury in dogs and usually is a consequence of a second- or third-degree sprain of the palmar carpal ligaments and fibro-cartilage.1 During situations in which overloading occurs in a limb, compressive forces can cause fractures of the carpal and metacarpal bones, and tensile forces or hyperextension can cause damage in the ligamentous structures.2 Most of these injuries involve falls from a height, overuse injuries in working dogs, or road traffic accidents, all of which can cause carpal hyperextension with irreversible damage to the palmar ligaments and fibrocartilaginous support. Other injuries include carpal fractures, intra-articular fractures, traumatic or congenital luxations, nonunions, or severe arthritis.3
Repair of these injuries generally requires pancarpal arthrodesis, which is commonly performed with straight compression plates or HDCPs. These plates are secured to a metacarpal bone (usually the third metacarpal bone) distally and, as such, generally require the use of an additional cast or splint to mechanically support the bone in the early recovery period.4 In contrast, CLPs, which are a newer concept, distribute the load at the third and fourth metacarpal bones and are presumed to not require additional cast or splint support.5 This castless concept with the CLP has the potential to simplify early postoperative recovery and thus avoid potential bandage-related problems.
The purpose of the study reported here was to investigate how these 2 plate designs would affect the load transfer to the applied bones, in addition to the implant stresses sustained when the bone-plate constructs were loaded (via calculations of the load during trotting). To do so, the aim was to develop a computational model with directed input from mechanical tests of these 2 constructs. Our hypothesis was that an FE model could be developed to assess the peri-implant strain distribution around each pancarpal plate, which could then be used to compare their respective failure likelihoods (high strain areas) with commonly reported clinical failure modes of the respective implants.
Castless pancarpal arthrodesis plate
Hybrid dynamic compression plate
Aquilion 19, Toshiba America Medical Systems Inc, Tustin, Calif.
Jorgensen Laboratories Inc, Loveland, Colo.
Orthomed, Halifax, West Yorkshire, England.
N2A-06-T001N350, Vishay Micro-Measurements, Raleigh, NC.
MTS Bionix 858, MTS Systems Corp, Eden Prairie, Minn.
Huppert 6, Huppert GmbH, Herrenberg, Germany.
MGCplus AB22A/AB32, Hottinger Baldwin Messtechnik, Darmstadt, Germany.
AMIRA Visage Imaging GmbH, Berlin, Germany.
Geomagic, Geomagic Inc, Merrimack, NH.
Matlab, version 6.5.1, The MathWorks Inc, Natick, Mass.
ABAQUS, Dassault Systemes Simulia Corp, Providence, RI.
Image Tool, version 3.0, University of Texas, San Antonio, Tex.
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