Less invasive surgical treatment of traumatic thoracolumbar fractures

Abstract

Less invasive surgical treatment of traumatic thoracolumbar fractures.

In this thesis various strategies were employed to evaluate the posibilities of reducing the invasiveness of the surgical treatment of traumatic thoracolumbar fractures. A systematic review of the literature suggested that adequate immobilization (as opposed to rigid fixation) of the fractured spine will, in the end lead, to good functional results regardless of the technique used. Previous work demonstrated that insufficient anterior column support can lead to (late onset) kyphosis, mechanical instability, pain and neurological deficit. In a human cadaveric thoracolumbar burst fracture study we demonstrated the feasibility and relative safety of adding balloon vertebroplasty with calcium phosphate cement as a means of reinforcing the anterior column, to the regular treatment of pedicle screw instrumentation. By using a new imaging modality (3D rotational X-ray imaging) we were also able to demonstrate the usefulness and safety of balloon vertebroplasty in fractures where damage to the longitudinal ligaments can be expected. Furthermore, we were able to validate this imaging technique by quantitatively comparing reconstructed (3D) images with corresponding anatomical sections. A high accuracy in displaying the spinal anatomy was found with low interobserver and intraobserver differences. The histological and thermal effects of injecting polymethyl methacrylate and calcium phosphate cement, in artificially created defects in the vertebral body of the goat spine, were investigated. No signs of degeneration to the surrounding tissues could be detected six weeks and six months after surgery and the temperature elevation caused by polymerization of the polymethyl methacrylate cement was not found to reach critical levels. A clinical trial was performed in which twenty patients with traumatic thoracolumbar (burst) fractures but without neurological deficit were included. Balloon vertebroplasty with calcium phosphate cement was performed after internal reduction and fixation with pedicle screw instrumentation. It was found that a significant reduction of the endplate fracture could be achieved after the experimental procedure. Leakage of cement was observed in some patients but did not lead to clinically relevant conditions. The follow-up of the patients was too short to draw solid conclusions yet but the feasibility of the experimental procedure was demonstrated. A randomized controlled clinical trial is currently under consideration. In another human cadaveric study, we demonstrated the feasibility of percutaneous treatment of traumatic fractures by combining balloon vertebroplasty with reduction and fixation using the AO external spine fixator. The external fixator was removed after curing of the cement (typically within 24 hours) and biomechanical tests were performed. It was found that a significant reduction of the fractured endplate could be achieved and at least 60% of the reduced height remained after loading the treated fractures with the maximum values that are sustained during in vivo conditions. This percutaneous treatment could be performed using six small stabwounds instead of a midline incision with the associated soft tissue damage. In the last chapter a device that can be inserted percutaneously, is proposed that could be used as standalone reduction/fixation device for the treatment of traumatic thoracolumbar fractures. This device is currently in the prototype stage and has already undergone some human cadaveric testing.