Der Vergleich von verschiedenen dorsalen Stabilisierungstechniken im Bereich der Brustwirbelsäule unter Betrachtung der Stabilität - eine biomechanische Studie

The vertebral compression fracture has developed into a socio-economic disease, because of its increasing incidence in the last few years. Particularly young people can be endangered to suffer a traumatic A3- or A4-fracture (AO spine injury classification) through high-speed trauma in traffic and falls. For years there has been a debate about the various surgical treatment options for these so-called burst fractures. In addition to ventral instrumentation and combined surgery, dorsal surgical treatment is just one of the many different treatment procedures that can be used to stabilize a thoracic vertebral fracture. While many studies have examined the comparison between dorsal, ventral and combined procedures, there is still no recommendation which dorsal instrumentation procedure guarantees the best treatment. It is not clarified yet whether it is necessary to stiffen four spinal column segments or whether a bisegmental instrumentation (possibly including cement augmentation) is sufficient for adequate stabilization. The resulting question for this study was: Which dorsal stabilization method shows the greatest stability in case of a thoracic vertebral fracture and prevents most effectively a loss of height of the broken vertebral body after surgical treatment? In the context of this question, the obvious hypothesis that a stiffening over four segments ensures greater stability than a stiffening over two segments (with or without cement augmentation) had to be investigated and discussed. To answer the question and to improve the treatment of burst fractures the following was done. 15 fresh-frozen human cadaveric spines were prepared used and embedded in Technovit. A standardized burst fracture (A3 / A4 according to AO classification) was generated at the level of the vertebral body Th5 by a free-falling weight. The fractures were treated with one of three dorsal osteosynthesis methods. Pedicle screw systems over two segments with and without cement and pedicle screw systems over four segments were used. After the instrumentation the spines was loaded with a servohydraulic machine. Forces and frequency of the load were similar to the physiological load in the first six weeks after the operation. The stability of the spine was measured by the compressibility of the spine and the loss of height of the vertebral body Th5. At different times the anterior, central and posterior heights of the index vertebra were measured. The study provides the following results. Compared to the other instrumentation methods, the dorsal stiffening over four segments allows less compression. Furthermore, with multi-segment stiffening, the central height does not decrease to the level of the fracture after loading. Both results do not seem to be influencing factors for the loss of height of vertebral Th5 after load. All procedures show a significant loss of height. There is no advantage of one dorsal procedure over the others. The low number of cases, the properties of the spines and the test possibilities were limited, which allows only partially transferable results to the in vivo situation. Further biomechanical and clinical studies must be conducted to make a final decision, which dorsal surgical procedure allows the best clinical treatment for burst fractures. The questions raised in this study, whether a more complex multisegmental or cementaugmented dorsal stabilization is necessary at all, if there is a burst fracture with only little loss of height, could be the next point that needs to be studied.