OTA 2006 Posters

Scientific Poster #72 Basic Science

A Biomechanical Comparison of Locked and Unlocked Plating
in a Cadaveric Short-Segment Comminuted Proximal Radius
Fracture Model
Scott G. Kaar, MD (a-AO Foundation);
Aaron S. Weaver, MS (a-AO Foundation);
Madhav A. Karunakar, MD (a-AO Foundation);
Steven A. Goldstein, PhD (a-AO Foundation);
Elizabeth P. Frankenburg, MS (a-AO Foundation);
Orthopaedic Research Laboratory, Department of Orthopaedic Surgery,
The University of Michigan, Ann Arbor, Michigan, USA

Objectives: This study was conducted to determine if locked plating is mechanically superior to conventional plating when only 4 cortices of fixation are available.

Methods: A comminuted short-segment proximal radius fracture model was created in six matched pairs of embalmed cadaveric radii by creating a 5-mm gap osteotomy in the proximal third of the bone. A 6-hole locked compression plate was utilized, leaving the proximal third hole unfilled over the gap osteotomy. This allowed for two screws proximal to the fracture and three screws distal to the fracture. The remaining 5 screw holes were filled with either locked or conventional unlocked screws. Specimens were cyclically tested with axial compression and bending for 5,000 cycles sequentially at 90 N, 120 N, and 150 N, and then cycled to failure at 180 N. Displacement and cycles to failure were recorded.

Results: All specimens survived the first 15,000 cycles. Average displacements for the unlocked group at 90 N, 120 N, and 150 N were 4.26 mm, 5.98 mm, and 8.12 mm, respectively. Average displacements for the locked group were 4.24 mm, 6.25 mm, and 8.53 mm, respectively (P >0.05 for each). Change in displacement for the unlocked group over 5,000 cycles at 90 N, 120 N, and 150 N were -0.23 mm, 0.04 mm, and 0.11 mm, respectively. Change in displacement for the locked group were 0.07 mm, 0.08 mm, and 0.16 mm, respectively (P <0.05 at 90 N and P >0.05 at 120 N and 150 N). At 180 N, specimens survived an average of 6,859 cycles (unlocked) and 6,693 cycles (locked) (P >0.05). Four specimens in each group failed through plate fracture. One specimen in each group failed by
fracturing through a screw hole. One specimen in each group failed with the plate pulling off the bone.

Conclusions: Locked plating provided no advantage over unlocked plating in combined axial compression and bending when only 4 cortices of fixation were available in a proximal radius fracture model.

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.