OTA 2005 Posters

Scientific Poster #73 Basic Science

A Biomechanical Comparison of Distal Femoral Fracture Fixation: The Dynamic Condylar Screw, Distal Femoral Nail, Locking Condylar Plate, and Less Invasive Stabilization System

David A. Parker, MD (n); Eugene P. Lautenschlager, PhD (n);
Michael L. Caravelli, MD (n); David C. Flanigan, MD (n);
Bradley R. Merk, MD (a-Synthes);
Northwestern University, Chicago, Illinois, USA

Purpose: This biomechanical study was performed to directly compare the coronal plane stiffness of the Dynamic Condylar Screw, locking Distal Femoral Nail, Locking Condylar Plate, and Less Invasive Stabilization System (LISS plate).

Methods: 32 moderately to severely osteoporotic synthetic femurs (average bone density 0.22 g/cm3) were divided into four equal experimental groups. Femurs in group I were instrumented with the Dynamic Condylar Screw, femurs in group II were instrumented with the Distal Femoral Nail, group III femurs were instrumented with the Locking Condylar Plate, and group IV femurs were instrumented with the LISS plate. After instrumentation, a distal femoral gap osteotomy was created in each specimen. Each femur was then loaded along its mechanical axis and displacement across the osteotomy site was measured in the coronal plane. All constructs were then loaded to failure and the ultimate load at failure was recorded. Load/deformation curves were constructed for each of the four groups and the average slopes of these curves were used to compare the relative stiffness of the different constructs. In addition, average failure loads for the four groups were compared.

Results: The locked Distal Femoral Nail, Locking Condylar Plate, and LISS plate implants all provided significantly stiffer fixation than the Dynamic Condylar Screw. No statistical differences were found among the stiffness values of the Distal Femoral Nail, Locking Condylar Plate, or the LISS plate. However, statistical analysis did reveal significantly higher ultimate loads to failure in the Distal Femoral Nail and Locking Condylar Plate.

Conclusions/Significance: Locking constructs provide greater coronal plane stability in the treatment of comminuted distal femoral fractures. Although no significant differences were found among the stiffness values of the various locking constructs tested, the Distal Femoral Nail and Locking Condylar Plate may provide greater overall coronal plane stability due to their significantly higher loads to failure.

If noted, the author indicates something of value received. The codes are identified as a-research or institutional support; b-miscellaneous funding; c-royalties; d-stock options; e-consultant or employee; n-no conflicts disclosed, and *disclosure not available at time of printing.