Biomechanical evaluation of DTRAX Facet System.
J Biomech Eng. 2014 Jan 1;
Authors: Leasure J, Buckley J
Objective: A majority of the middle-aged population exhibit cervical spondylosis that may require decompression and fusion of the affected level. Minimally invasive cervical fusion is an attractive option for decreasing operative time, morbidity, and mortality rates. A novel device, the DTRAX facet screw system (Providence Medical) promises minimally invasive deployment resulting in decompression of the neuroforamen and interfacet fusion. Present study investigates the effectiveness of the device in minimizing intervertebral motion to promote fusion, decompression of the nerve root during bending activity, and performance of the implant to adhere to anatomy during repeated bending loads. Methods: We observed flexion, extension, lateral bending, and axial rotation range of motion in cadaver models of c-spine treated with DTRAX as stand-alone and supplementing anterior plating. DTRAX was deployed bilaterally at single levels. Specimens were placed at the limit of range-of-motion in flexion, extension, axial bending, and lateral bending. 3-D images of the foramen were taken and post-processed to quantify changes in foraminal area. Stand-alone DTRAX specimens were subjected to 30K cycles at 2 Hz of non-simultaneous flexion-extension and lateral bending under compressive load and xray imaged at regular cycle intervals for quantitative measurements of device loosening. Results: Stand-alone DTRAX increased specimen rigidity in all directions except extension. 86% of all deployments resulted in some level of foraminal distraction. Rate of effective distraction was maintained in flexed, extended, and axially rotated postures. Two specimens demonstrated no detectable implant loosening (<0.25 mm). Three showed unilateral sub-clinical loosening (0.4 mm maximum), and one had sub-clinical loosening bilaterally (0.5 mm maximum). Conclusion: Results of our study are comparable to previous investigations into the rigidity of other stand-alone minimally invasive technologies. DTRAX system effectively increased rigidity of the affected level comparable to predicate systems. Results of this study indicates DTRAX increases foraminal area in the cervical spine, and decompression is maintained during bending activities. Clinical studies will be necessary to determine whether the magnitude of decompression observed in this cadaveric study will effectively treat cervical radiculopathy; however, results of this study, taken in context of successful decompression treatments in the lumbar spine, are promising for the continued development of this product. Results of this biomechanical study are encouraging for the continued investigation of this device in animal and clinical trials, as they suggest the device is well fixated and mechanically competent.
PMID: 24389961 [PubMed – as supplied by publisher]