Boersma, A. (Anton) (2014) Optimalisatie van de directe vertebrale derotatie techniek, een in vitro studie. thesis, Medicine.
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Abstract
Background: Scoliosis is a three-dimensional deformity of the spine, which may observed in 3-5% of the adolescent population. Generally, the lateral deviation of the vertebral column is frequently associated with an axial rotation of the vertebrae. In most cases (85%), aetiopathogenesis of scoliosis is unknown, adolescent idiopathic scoliosis (AIS). The most important problem related to AIS is the progression of the curve. It has been shown that during periods of high skeletal growth velocity, AIS is often progressive. Based on the current literature, it seems that the best correction can be achieved with the direct vertebral derotation technique (DVR), which entails that vertebrae will be separately derotated. The DVR technique requires pedicle screw(s) placement, which will be rotated counter directionally of the transverse plane of the deformity. A significant problem using this technique is failure/dislodgement of the pedicle screw during derotation, which results in loss or inability of correction. However, it has not been established which DVR construction most effectively transfers the yield torque to the vertebra. The aim of the study was to test the maximal transfer of the yield torque in an angular stable linked construction, that may result in a lower risk of pedicle screw failure. The purpose of this study is to investigate by which DVR construction the most yield torque can be transmitted to the vertebra. Methods: In this preclinical translational in vitro study were the biomechanics of three different DVR constructions compared. A total of 24 analyses took place at the Sprint Research Laboratory of the University of Groningen. The following DVR constructions have been compared: derotation by using 1) a solitary pedicle screw (SP), 2) two pedicle screws linked with a high, not angular, stable connection (DP) and 3) two pedicle screws linked with a low angular stable connection(DPAS). These constructions have been tested in solid polyurethane foam blocks (0.080 ± 0.008 g/cm3). Results: The analyses showed the maximum force until pedicle screw failure, was significantly higher (p<0.001) in the DP-group (31.1 ± 3.8 N), compared to the SP-group (17.3 ± 4.2 N). Furthermore the maximum force until breaching, was significantly higher (p<0.001) in the DPAS-group (50.3 ± 2.9 N), compared to the DP-group. The elastic modulus of the DPAS-group (8.0 ± 1.0 N) was significant higher (p<0.001), compared to the other two groups (SP 2.1 ± 0.2 N; DP 3.3 ± 1.1 N). The windshield wiper effect is an undesirable technical effect using the DVR technique. This effect occurred in the SP- and DP-group, however it was partially seen in the DPAS-group. Conclusion: This study showed that DVR by using an angular stable linked construction with two pedicle screws can transmit more yield torque to the vertebra, compared with the other two constructions. The angular stable characteristic results in a different mode of failure and reduces the appearance of the windshield wiper effect. The use of an angle stable linked construction will be theoretically more safe and might provide better axial rotational correction.
| Item Type: | Thesis (Thesis) |
|---|---|
| Supervisor name: | Faber, Dr. C. |
| Faculty: | Medical Sciences |
| Date Deposited: | 25 Jun 2020 10:41 |
| Last Modified: | 25 Jun 2020 10:41 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/290 |
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