OTA 2006 Posters

Scientific Poster #64 Basic Science

A Mechanical Evaluation of Two Fixation Methods for Coronal Fractures of the Lateral Condyle of the Distal Femur (OTA Type 33B3)
Gregg J. Jarit, MD (n); Frederick J. Kummer, MD (n);
Marc J. Gibber, BA (n); Kenneth A. Egol, MD (n);
New York University­Hospital for Joint Diseases, New York, New York, USA

Purpose: Our objective was to compare the relative strength and stability of two fixation methods for displaced coronal shear fractures of the lateral femoral condyle (Hoffa fractures, OTA Type 33B3).

Design/Methods: Eight matched pairs of embalmed femurs were divided into two groups and simulated Hoffa fractures were created. In each pair, one of the fractures was fixed with two screws placed in an anteroposterior direction, and in the other, the fractures were fixed with two screws placed in a posteroanterior direction. All specimens were cyclically tested with simulated physiologic loading. Displacement of the femoral condyle was continuously measured to 105 cycles. The specimens were then loaded to failure.

Results: Fixation with posterior to anteriorly placed cancellous lag screws was significantly more stable than anterior to posteriorly placed screws at 105 cycles (P = 0.05), with 0.67 mm displacement compared to 1.36 mm, respectively. They were also more stable at 10, 100, and 1000 cycles; however, these displacements were not statistically significant. Fixation with posteriorly placed cancellous screws also had significantly higher ultimate strength (P = 0.04); 1700 N compared to 1025 N for anterior placement.

Conclusion/Significance: Lag screws placed posterior to anterior provided more stable fixation of Hoffa fractures in embalmed femurs than anteroposterior placed lag screws. This finding may apply in the clinical setting; however, this technique requires that the screw heads are recessed beneath the articular surface and the effects of the cartilage defects so created are not known. The choice of technique is also determined by concomitant fractures and the required exposure for their fixation.

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.