SLR - December 2014 - Priya Anand

Bionic Plate Design for Calcaneal Fracture Treatment. A Biomechanical Analysis and First Clinical Results

Reference: Kinner B, Kerschbaum M, Bley C, Spiegel A, Roll C. Bionic Plate Design for Calcaneal Fracture Treatment. A Biomechanical Analysis and First Clinical Results. International Orthopaedics. 2014 Oct 15. [Epub ahead of print]

Scientific Literature Review

Reviewed By: Priya Anand, DPM
Residency Program: Cambridge Health Alliance

Podiatric Relevance: The treatment of calcaneal fractures can be challenging. Many calcaneal fractures are treated with ORIF using a plate and sometimes a locking plate. The authors of this study compared the basic mechanical properties of two different plates. They compared a standard locking calcaneal plate (Synthes) to what they referred to as the “Bionic” plate (a new construct). They hypothesized that due to the design construct, the bionic plate would score higher in basic mechanical properties and have a lower risk of plate failure.

Methods: The basic mechanical properties of the Synthes locking plate and the Bionic plate were compared using calcaneal models made of glass-reinforced polyamide and a Zwick/Roell dynamic testing machine. Each calcaneal model had a Sanders Type 2b fracture with six fragments. The basic mechanical properties that were tested included load, deformation, and load to failure. They recorded the number of cycles it took to failure, mode of failure, maximum forces endured prior to failure, and displacement under cyclic loading. A video of the testing was also obtained to determine the precise cause of failure. Failure was defined as maximum axial displacement of more than 10mm, plate fracture, or screw failure. Six standard locking plates and six bionic plates were tested and results were compared.

In addition, they evaluated the plates clinically. Ten patients received the bionic plate and then were evaluated. The same surgeon performed all the procedures. The surgeon used a single extended lateral approach and patients were allowed partial weight-bearing for at least 6 weeks after surgery. No immobilization was recommended to any patients. The mean age of the patients included was 52 years (25-70); eight were males and two were females. Most sustained the fractures after a fall from a height. The fractures were all classified as either a Sanders type 2A or Sanders type 3AC. Patients were followed for a 12 month period and complications, radiographic evaluation, and plate failure were recorded.

Results: Overall they found the Bionic plate had better basic mechanical properties. On average it took 89,250 cycles before failure while the standard plate took 53,100 cycles. The mode of failure for the bionic plate was found to be by plate fracture at the upper tuber part of the frame. The standard plate was found to fail by massive deformation of the plate. When comparing the maximum force sustained before failure the bionic plate was able to sustain significantly higher load levels compared to the standard plate. Finally when comparing the displacement under cyclic loading, it was found that the bionic plate was more rigid with less displacement.

Clinically they found no major complications with the 10 patients. All healed their fractures by the end of the 12 month follow up. None had any loss of reduction, plate failure, or signs of superficial or deep wound infections. Six of the patients started showing signs of arthritis after the 12 months. The average AOFAS score for the patients was 79 at the completion of the study.

Conclusions: This study reveals a new plate construct that may be promising when treating calcaneal fractures. Comparing it to the standard locking plate used, this plate has more rigidity as well as greater basic mechanical properties. Although initial clinical findings are promising, further larger clinical studies comparing the bionic plate to other plate constructs would be beneficial. Additionally a clinical study with a longer period of follow up would be helpful to determine more long term effects.

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