Incorrect fracture analysis in kyphoplasty - potential for severe complications
C Birkenmeier, H Trouillier, T Seidl, B Wegener, C Pellengahr Schulze, V Jansson
C Birkenmeier, H Trouillier, T Seidl, B Wegener, C Pellengahr Schulze, V Jansson. Incorrect fracture analysis in kyphoplasty - potential for severe complications. The Internet Journal of Minimally Invasive Spinal Technology. 2008 Volume 3 Number 4.
Introduction: Kyphoplasty has become a very popular therapy for the treatment of osteoporotic vertebral fractures (OVFx), based on an easy-to-learn technique and comparatively few perioperative complications. Good reimbursement and intense advertisement by the industry also play a significant role. However, there are some fundamental issues at the heart of the kyphoplasty procedure, which can cause major problems when left unconsidered. For one, the poly-methlyl-metacrylate (PMMA) bone cement does not integrate into bone and does not allow for bone-healing onto the tamp. It also is much stiffer than osteoporotic bone. Another important factor is the reduced trabecular density of severely osteoporotic vertebrae, which may lead to incorrect fracture analysis in CT-imaging.Methods: Retro- and prospective evaluation of a series of 9 cases referred to our departments from 2006 through 2008. All patients had received stand-alone kyphoplasties of the thoracolumbar junction at other institutions. After initial improvement, all patients experienced renewed pain and immobilization within weeks, several patient suffered neurological deficits. We obtained the pre- and postoperative imaging studies of these patients, wherever possible. Presented is an analysis of the radiographic features of these fractures, how these relate to the pertinent fracture classifications and what their biomechanical implications are. These findings are interpreted on the background of the mechanical properties of PMMA bone cement and the biomechanics of the aging spine.Results: In all 9 cases, gross instability and kyphotic deformity was found at the location of the PMMA tamp. In many cases, this was associated with resorption of the treated vertebra. In several cases advanced destruction of neighboring vertebrae by the PMMA tamp was observed and in 3 cases there was subtotal spinal canal obstruction. Analysis of the preoperative imaging studies gave evidence to unstable burst fractures with severely reduced load-sharing capability, mechanical dissociation of the pedicle from the vertebral body or disc-with-endplate avulsion. 8 patients required multi-segment posterior instrumentation and fusion, combined with vertebral body replacement in some cases. 1 patient died from complications of immobilization prior to the scheduled stabilization.Discussion and Conclusion: Performing stand-alone kyphoplasty in unstable OVFx at the thoracolumbar junction may cause complications that far exceed the original problem. Unstable fractures in this sense include all split and burst fractures (AO types 2 and 3) 1 as well as fractures that leave the vertebral body highly comminuted or displaced 2. The same applies for vertebrae that lack sufficient residual bone to allow for healing around the tamp. Additional contraindications are mechanical dissociation of the pedicles from the vertebral body and ruptured anterior longitudinal ligaments (ALL) 3 since this renders the posterior or anterior tension band ineffective. Disc-with-end plate avulsions also do not allow for fracture healing and they are frequently associated with ALL damage. Correct fracture analysis therefore is of paramount importance and a high-resolution, thin-slice CT scan with sagittal and coronal reconstructions is required. MRI is mainly required for the identification of fresh fractures and ALL damage, which can both be seen on T2-weighted sagittal sequences. When any of the contraindications outlined above are present, kyphoplasty should not be preserved without additional stabilization such a pedicle screw instrumentation. Despite the availability of kyphoplasty and the good reimbursement for the procedure, conservative treatment options for OVFx should not be forgotten.