A novel anchoring system for use in a non-fusion scoliosis correction device.
Spine J. 2014 Apr 30;
Authors: Wessels M, Homminga JJ, Hekman EE, Verkerke GJ
BACKGROUND CONTEXT: Insertion of a pedicle screw in the mid and high thoracic region has a serious risk of facet joint damage. Since flexible implant systems require intact facet joints, we developed an enhanced fixation that is less destructive to spinal structures. The XSFIX is a posterior fixation system that uses cables that are attached to the transverse processes of a vertebra.
PURPOSE: Purpose of this study is to determine whether a fixation to the transverse process using the XSFIX is strong enough to withstand the loads applied by the XSLATOR (a novel, highly flexible non-fusion implant system) and thus whether it is a suitable alternative for pedicle screw fixation. Study Design/Setting: The strength of a novel fixation system using transverse process cables was determined and compared to the strength of a similar fixation using polyaxial pedicle screws on different vertebral levels.
METHODS: Each of 58 vertebrae, isolated from four adult human cadavers was instrumented with either a pedicle screw anchor (PSA) system or a prototype of the XSFIX. The PSA consisted of two poly-axial pedicle screws and a 5 mm diameter rod. The XSFIX prototype consisted of two bodies that were fixed to the transverse processes, interconnected with a similar rod. Each fixation system was subjected to a lateral or an axial torque.
RESULTS: The PSA demonstrated fixation strength in lateral loading and torsion higher than required for use in the XSLATOR. The XSFIX demonstrated high enough fixation strength (in both lateral loading and torsion), only in the high and mid thoracic region (T10-T12).
CONCLUSIONS: This experiment showed that the fixation strength of XSFIX is sufficient for use with the XSLATOR only in mid and high thoracic region. For the low thoracic and lumbar region, the PSA is a more rigid fixation. Since the performance of the new fixation system appears to be favorable in the high and mid thoracic region, a clinical study is the next challenge.
PMID: 24793361 [PubMed – as supplied by publisher]