OTA 2006 Posters

Scientific Poster #71 Basic Science

A Comparison of Percutaneous Locked versus Traditional Open Plate Fixation in a Subtrochanteric Fracture Gap Model
Brett D. Crist, MD1 (a-Synthes); Mark A. Lee, MD2 (a-Synthes);
Afshin K. Khalafi, MD2 (a-Synthes); Scott J. Hazelwood, PhD2 (a-Synthes);
1University of Missouri, Department of Orthopaedic Surgery, Columbia, Missouri, USA;
2University of California Davis Medical Center, Sacramento, California, USA

Purpose: The angled blade plate is the gold standard in extramedullary subtrochanteric femoral fracture fixation, but it requires an extensile lateral exposure. While minimally invasive techniques exist utilizing traditional implants, little formal evaluation exists for specifically designed percutaneous extramedullary implants. The purpose of this study was to compare 3 percutaneous locked plating constructs to the standard 95 degree angled blade plate.


Methods: Forty composite adult femurs were divided into 4 equal groups. Group 1 consisted of femurs plated with the 95 degree angled blade plate; group 2, a modified broad 4.5-mm combination locking plate; group 3, a precontoured proximal femoral locking plate including an oblique, "kickstand" screw; and group 4, the proximal femoral locking plate without the kickstand screw. After plate application, a 30 degree wedge osteotomy was created at the level of the lesser trochanter to create a subtrochanteric gap model. Each specimen underwent axial and torsional stiffness testing along with cyclic axial loading to failure to determine irreversible deformation. A Fisher's Exact Test was used to determine statistical significance between the groups.

Results: Axial stiffness testing revealed that the proximal femoral locking plates with the kickstand screw were significantly stiffer than all other constructs. The blade plate constructs were significantly stiffer in torsion. With cyclic axial loading to failure, the blade plates had significantly less irreversible deformation than the proximal locking plates without the kickstand screw. The proximal locking plate with the kickstand screw had significantly less irreversible deformation than the broad plates and proximal locking plates without the kickstand screw. No significant difference was detected between the blade plates and the proximal locking plates with the kickstand screw.

Conclusion/Significance: As the trend toward biological plating continues, a percutaneous plating solution for subtrochanteric femur fractures is attractive. Although minimally invasive techniques using traditional extramedullary implants exist, we evaluated specifically designed implants for the proximal femur that offer the benefits of locking plate technology and anatomic contour. Our data reveal that the proximal femoral locking plate with the kickstand screw provides more axial stiffness, less torsional stiffness, and equivalent irreversible deformation to cyclic loading when compared to the blade plate. These biomechanical data provide surgeons with the knowledge that this construct is essentially equivalent to the angled blade plate, but it allows for percutaneous insertion that avoids the potential morbidity of an extensile approach.

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.
· The FDA has not cleared this drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an "off label" use). · · FDA information not available at time of printing.