Physeal fractures in dogs are commonly stabilized through the use of diverging Kirschner wires1 but are rarely managed with bone plates because of the short length of epiphyseal fragments and because bone plates limit longitudinal bone growth.2 The presence of Kirschner wires (Rush pins) may also limit longitudinal bone growth.3 Biodegradable, polymer-based bone plates are sporadically used in orthopedics and are most often used to stabilize fragments of non–weight bearing bones (eg, skull fragments) after fractures and osteotomies.4,5 Such bone plates were used successfully to stabilize radial fractures in 10 toy-breed dogs.6 Free-form orthopedic implants are implants designed for specific applications. Fracture repairs made with free-form implants may be more stable than repairs made with conventional commercial implants because free-form implants can be better contoured to the bone surface than commercial implants.7
The purpose of the study reported here was to develop free-form biodegradable bone plates and assess the mechanical properties of constructs made with these plates. We hypothesized that constructs made from free-form biodegradable plates would have mechanical properties superior to constructs made from Kirschner wires but inferior to constructs made from metal bone plates. To test these hypotheses, we designed bone models of a physeal fracture in the distal portion of the canine femur and stabilized them by use of thin or thick biodegradable bone plates, custom or commercial metal bone plates, or Kirschner wires.
Four Kirschner wires
Commercial stainless steel plate
Custom free-form titanium plate
Thick polycaprolactone biodegradable plate
Thin polycaprolactone biodegradable plate
Siemens SOMATOM Sensation 16-slice configuration, Siemens Medical Solutions Inc, Malvern, Pa.
Mimics, version 8.11, Materialize USA LLC, Ann Arbor, Mich.
ClayTools, version 1.2, SensAble Technologies Inc, Woburn, Mass.
PHANTOM Omni haptic device, SensAble Technologies Inc, Woburn, Mass.
Magics, version 12.0.1, Materialis USA LLC, Leuven, Belgium.
Dimension FDM, Stratasys Inc, Eden Prairie, Minn.
Mold Max 30, Smooth-On Inc, Easton, Pa.
BJB TC-300 foam, Burman Industries, Van Nuys, Calif.
Bone meal, Scotts Miracle-Gro Co, Marysville, Ohio.
EP5340 resin, Eager Polymers Co, Chicago, Ill.
Somos 11110 Watershed resin, DSM Somos, Elgin, Ill.
SLA-190 stereolithography machine, 3D Systems, Rock Hill, SC.
Loctite Fixmaster, Fel-Pro Chemical Products, Commerce City, Colo.
Tone Polymer P-787, Union Carbide Corp, Houston, Tex.
Arcam A2, Arcam AB, Mölndal, Sweden.
J-428U 3.5-mm distal femoral plate, Jorgensen Laboratories Inc, Loveland, Colo.
CD600, Mark V Laboratory Inc, East Granby, Conn.
Synthes Ltd, West Chester, Pa.
DSD-4 torque screwdriver, Imada Inc, Northbrook, Ill.
MTS 858 Mini Bionix II, MTS System Corp, Eden Prairie, Minn.
Excel Toolkit, PRA Center, Syracuse Research Corp, Syracuse, NY.
Excel Analysis ToolPak, Microsoft Corp, Redmond, Wash.
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