• Michael J Gardner, Robert H Brophy, Deirdre Campbell, Amit Mahajan, Timothy M Wright, David L Helfet, and Dean G Lorich.
• Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA. gardnerm@hss.edu
• J Orthop Trauma. 2005 Oct 1;19(9):597-603.

ObjectiveThe purpose of this cadaveric study was to compare the mechanical behavior of a locked compression plate, which uses threaded screw heads to create a fixed angle construct, with a dynamic compression plate construct in a cadaver radius model.DesignMechanical study with cyclic testing and high-speed optical motion analysis.SettingBiomechanics laboratory at an academic institution.Patients/ParticipantsEighteen pairs of fresh-frozen human cadaver radii were divided into 3 groups of 6 to be tested as a group in each of the following force applications: anteroposterior (AP) bending, mediolateral bending, or torsion.InterventionEach bone was osteotomized leaving a 5-mm fracture gap and then fixed with a plate. For each pair, 1 radius received a standard plate (limited-contact dynamic compression plates; LC-DCP), the contralateral radius was fixed with a locking compression plate (LCP), and specimens underwent cyclic loading. Normalized stiffness, average energy absorbed, and Newton-cycles to failure were calculated. In addition, a 3-dimensional, high-speed, infrared motion analysis system was used to evaluate motion at the fracture site.Main Outcome MeasurementsConstruct stiffness, fracture site motion, cycles to failure, and energy absorption. Repeated measures ANOVA were used to detect differences between groups with time.ResultsIn the torsion group, LCP specimens failed at 60% greater Newton-cycles than the LC-DCP (1473 vs. 918; P < 0.05). In the AP group, the LC-DCP absorbed significantly greater energy during 10,000 cycles compared with the LCP group (P < 0.05). The 2 constructs demonstrated different biomechanical behavior with time. As cycling progressed in the LC-DCP specimens under torsion testing, stiffness (measured at the actuator at the bone ends) did not change significantly; however, fracture motion (measured at the fracture surfaces) decreased significantly (P = 0.04). The LCP specimens did not display similar behavior.ConclusionsOur findings indicated that LCP constructs may demonstrate subtle mechanical superiority compared with the LC-DCP. The LCP specimens had less energy absorption in the AP group and survived longer in the torsion group. Discordance of motion between measurement regions was observed only in the LC-DCP torsion group, and may have been caused by plate-bone slippage or bone-screw subcatastrophic failure. However, many other compared parameters were found to be similar, and the clinical significance of the few differences found between constructs mandates further investigation.

16 keywords...

hide…