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Original Investigation |

Stability of Midface Fracture Repair Using Absorbable Plate and Screw System Pilot Holes Drilled and Pin Placement at Angles Other Than 90°

Michael A. Carron, MD1; Giancarlo Zuliani, MD1; Lucio Pereira, MD1; Maher Abuhamdan, MD1; Adrianna Thibault, BS1; Nathan Dau, PhD2; Cynthia Bir, PhD2
[+] Author Affiliations
1Division of Facial Plastic and Reconstructive Surgery, Department of Otolaryngology–Head and Neck Surgery, Wayne State University School of Medicine, Detroit, Michigan
2Department of Biomedical Engineering, Wayne State University, Detroit, Michigan
JAMA Facial Plast Surg. 2014;16(1):42-48. doi:10.1001/jamafacial.2013.1404.
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Importance  Conventional plating systems use titanium plates for fixation of fractures, with benefits of strength and biocompatibility. However, titanium plates require that screws be placed at a 90° angle to the pilot holes. In the midface, this becomes extremely difficult. Today, a variety of craniomaxillofacial osteosynthesis systems are available, including resorbable plating systems. Specifically, the KLS Martin Sonic Weld system ultrasonically fuses the plate and the head of the pin when placed and will fill the pilot hole grooves completely even at less than 90° angles, which provides a tremendous advantage in midface fracture repair.

Objective  To determine if the KLS Martin Sonic Weld system provides plate-screw construct stability in human heads even when placed at acute angles at the midface buttresses.

Design, Setting, and Specimens  Twenty cadaveric head specimens with the mandible removed were prepared by creating osteotomies in the midface buttresses bilaterally. Specimens were defleshed and placed in a 2-part testing rig to hold and position the head for testing in a standard material testing system. Testing was performed at the Wayne State University Bioengineering test laboratories, Detroit, Michigan, using an Instron device and high-speed camera. Specimens were plated on one side of the midface using the KLS Martin Sonic Weld system with pilot holes and pins placed at 90° angles. On the contralateral side, the buttresses were plated with the KLS Martin Sonic Weld system at 60°, 45°, and 30° angles. Data were collected using the TDAS data acquisition system and were compared with matched pairs within each specimen.

Main Outcomes and Measures  Ultrasonically vibrated pins placed into absorbable mini-plates at less than 90° angles with the KLS Martin Sonic Weld system were compared with the same amount of stress as the system placed at a 90° angle before demonstrating plate-screw construct failure.

Results  Fifty-seven paired tests were collected, with 114 total tests. Twenty failures were due to bone breakage, and 94 fixations failed as a result of the plate-screw construct breaking. Fractures fixated with the ultrasonic absorbable plating system placed with screws at all tested angles failed at similar loads to our control plates with pins placed at 90° angles. These results lend the surgeon to successfully reduce fractures in the midface fragments in difficult-to-reach areas and possibly cut down on operative time while improving the chance of achieving a long-lasting adequate reduction.

Conclusions and Relevance  Although there is a measured difference in the laboratory, no clinical difference is observed because the maximum force is not usually encountered. Overall, the clinical scenario indicates absorbable plates to be a viable option in less accessible areas.

Level of Evidence  NA.

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Figure 1.
Midface Degloving Approach to Fracture

Elevation of the flap to expose the underlying fracture can create a hard-to-reach area in certain locations, such as the midface to place screw exactly at 90° to the plate.

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Figure 2.
KLS-Martin Sonic Weld System

KLS Martin Company created an absorbable system with pins that are ultrasonically vibrated to fill the pilot hole with the pin material. A, Photomicrograph demonstrating how the head of the Sonic Weld pin (arrow) is ultrasonically vibrated to lock with the plate. This essentially fuses the head of the pin to the plate in a type of weld. B, Demonstration of how the Sonic Weld system ultrasonically vibrates the pin to fill the predrilled grooves in the pilot hole.

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Figure 3.
Preparation of Cadaver Specimens

Weber-Ferguson and sublabial incisions were made and the soft tissue elevated off the midface to unveil the underlying bony skeleton. The nasomaxillary and zygomaticomaxillary buttresses and the zygomaticofrontal sutures were exposed. Fractures were initiated with the oscillating saw and completed with gentle tapping with an osteotome.

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Figure 4.
Testing Device

All specimens were tested in a similar manner with the Instron 8500. The testing device is able to detect and read the applied load at the plate-pin construct and record the force at which failure occurred.

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