Anterior only procedure for stable thoraco-lumbar burst fractures is controversial. Prospective collection of clinical and radiological data in stable burst fractures with neurological deficit undergoing anterior only decompression and stabilisation with 2-year follow-up. 14 consecutive patients (8 females, 6 males) with two-column thoracolumbar burst fracture and neurological deficit underwent anterior corpectomy/hemi-corpectomy and instrumentation, from February 2007 to February 2009. Radiological data included classification of fracture (AO classification), kyphus angle and degree of canal compromise. Post-operative CT scans done to assess radiological improvement. Clinical data included neurological deficit at presentation, improvement or changes in neurology, length of surgery, estimated blood loss, post-operative complications and length of stay. Commonest mechanism was fall from height. 10 patients had incomplete burst fractures amenable to hemi-corpectomy. 8 of our patients were ASIA D, 4 were ASIA C or lower. They all improved by at least one grade. 2 patients had identical ASIA grade pre and post operatively. Pre-operative spinal canal compromise averaged 52.6% and vertebral body height loss averaged 48.9%. The mean kyphotic angles improved from 19.6° to 7.9 °. There were two cases with minor injury to the diaphragm, one developing a pneumothorax. Mean length of surgery and hospital stay were 4hours and 21minutes and 11.8 days respectively. The fractures in which the top part is burst and causing canal compromise, could be dealt with by top hemi-corpectomy requiring smaller approach. One stage anterior – only stabilization can yield successful clinical results.
Back pain may be related to abnormal segmental movement and suggested treatment is segmental fusion. Recent techniques using cages can achieve fusion rates of over 90% but the clinical results are no better. We hypothesise that the cages integrate fully to adjacent vertebrae taking all the load, producing abnormal stress patterns in the vertebrae producing pain. In this study a simple FE model of a disc and its adjacent vertebral bodies was developed using ANSYS software. The dimensions of the model were based on those of a human lumbar disc. The normal disc was modelled as having nucleus with fluid properties (bulk modulus 1720 MPa). To model the degenerate disc, the material properties of the nucleus were changed to be the same as the annulus (Young’s modulus, E=5 Mpa; Poisson’s ratio, n=0.49). To model fusion of the disc, the nucleus was replaced with a simple representation of a one of three of the commonly used cages. In all the models the material properties of the cancellous bone (E = 100 MPa; n = 0.3) and the cortical bone (E=12000MPa;n=0.3) remained the same. The model was loaded axially with 1.5 kN. The vertical and horizontal stress patterns around a loaded degenerate disc showed areas of increased loading in the endplate and cancellous bone. The inclusion of cages in the model showed high concentration of tensile and compressive stresses at the point of contact with the cages and in the cancellous bone of the vertebral bodies. The stress pattern showed more similarity to that of degenerate disc, than a normal one. Fusion cages alter the pattern of stress distribution in the adjacent vertebral bodies from that of the normal disc. The excellent fusion rates of the cages are not mirrored by improvement in clinical results. It supports the concept that abnormal load transfer may be a more significant cause of back pain than abnormal movement.
