Stability of midface fracture repair using absorbable plate and screw system pilot holes drilled and pin placement at angles other than 90°.

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.