Biomedical subjects

Deirdre Campbell

Publications and source records attributed to Deirdre Campbell.

2 recordsLinked to original sources

PubMed2005

The mechanical behavior of locking compression plates compared with dynamic compression plates in a cadaver radius model.

OBJECTIVE: The 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. DESIGN: Mechanical study with cyclic testing and high-speed optical motion analysis. SETTING: Biomechanics laboratory at an academic institution. PATIENTS/PARTICIPANTS: Eighteen 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. INTERVENTION: Each 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 MEASUREMENTS: Construct stiffness, fracture site motion, cycles to failure, and energy absorption. Repeated measures ANOVA were used to detect differences between groups with time. RESULTS: In 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. CONCLUSIONS: Our 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.

Biomechanical Phenomena↗

PubMed2002

Open reduction and internal fixation of humeral nonunions : a biomechanical and clinical study.

BACKGROUND: Several studies have compared different methods for fixation of the midpart of the humeral shaft, but there are only scattered data regarding which type of plate construct provides the best fixation for humeral nonunion. The objectives of this study were (1) to obtain objective data on the performance of four different plate constructs used for fixation of humeral nonunion, and (2) to report our clinical experience with plate fixation of thirty-seven nonunions of the midpart of the humeral shaft. METHODS: In the first part of the study, four plate constructs were compared in a Sawbones model. The groups consisted of (1) a posterior limited-contact dynamic compression plate alone; (2) a posterior limited-contact dynamic compression plate and an interfragmentary screw; (3) a posterior limited-contact dynamic compression plate, a lateral 3.5-mm reconstruction plate, and an interfragmentary screw; and (4) a posterior limited-contact dynamic compression plate and a lateral 3.5-mm reconstruction plate. Tests were performed with use of an MTS Bionix machine in anterior-posterior four-point bending, medial-lateral four-point bending, and external rotation torque. In the second part of the study, the charts of thirty-seven consecutive patients in whom a nonunion of the midpart of the humeral shaft had been treated with plate fixation were reviewed retrospectively. The average age of the patients was forty-eight years (range, thirteen to seventy-eight years). Nineteen patients were treated with a single posterior plate, and eighteen were treated with a two-plate construct with the plates parallel and lying at 90 degrees to each other. All of the nonunions were treated with bone-grafting, and an interfragmentary screw was used in thirty-six of the thirty-seven patients. Radiographs and the clinical status were evaluated at an average of thirteen months postoperatively. RESULTS: The biomechanical testing showed that the two-plate constructs were significantly stiffer than the single-plate constructs in all test modes (p < 0.05). In the clinical part of the study, thirty-four (92%) of the nonunions healed without complications at an average of 4.8 months. Two nonunions treated with the two-plate construct and one treated with one plate failed to heal. CONCLUSIONS: No significant difference in the healing rate was found between the two clinical groups (p = 0.4, beta = 0.9), and the overall healing rate was 92%. However, a two-plate construct with the plates at right angles is mechanically stiffer than a single-plate construct, which might be helpful if rigid stabilization of the humerus at the midshaft level is needed.

Adolescent↗