INTRODUCTION: Flexion distraction injuries (FDI) of the thoracic and lumbar spine can be stabilised with a short construct spanning one motion-segment. This fracture is functionally defined by failure of the posterior and middle columns in tension and the anterior column in compression or tension. Treatment of a predominantly bony injury with minimal deformity (Chance type) is usually non-operative. Intra-abdominal pathology, and ligamentous spinal instability are relative indications for surgery. Deformity of greater than 17 degrees of kyphosis has a poor prognosis when treated conservatively, and represents true instability in vitro. Surgical treatment is mainly through a posterior approach with instrumentation. Which construct to use and the number of motion segments to include is controversial. Multi-level instrumentation techniques both in distraction and compression have been used as well as shorter constructs, particularly in the lumbar spine. We addressed the efficacy of single motion-segment fixation by evaluating the radiographic and functional results of this treatment technique. METHODS: All patients diagnosed with a FDI were prospectively identified over a 48 months period. Non-operatively treated fractures were excluded. Other spine fractures were excluded. Demographics, co-morbidity, neurological status, operative details and complications were recorded. Radiographic reviewers were blinded to the functional outcome of the patient and the time of follow-up. The Oswestry Functional Assessment Questionnaire was administered by mail. RESULTS: Twenty-one eligible patients were identified. A significant (p<
0.0001) correction of deformity was achieved, from a mean pre-operative kyphosis of 10.1 degrees to a mean post-operative lordosis of 0.9 degrees. No loss of correction occurred. The mean Oswestry score was 11.5, with 88% of patients having minimal disability. One patient died from unrelated morbidity. CONCLUSIONS: Hoshikawa et al showed in vitro how compression forces alone can create FDI. Compression without flexion causes burst fractures. With moderate flexion there is FDI with anterior body compression. With increasing flexion FDI becomes entirely distractive. As the forces are concentrated at a single point, reconstruction only requires that this location be addressed. As all FDI are created by the same mechanism, regardless of structures injured only short segment fixation is required. We have demonstrated in FDI, single level fixation is biomechanically sound. Multilevel instrumentation creates loss of adjacent level motion segments. This is not necessary. The absence of a control group precludes absolute conclusions. Nonetheless most patients reported minimal disability related to their back and had excellent radiological outcomes. This study demonstrates that posterior reduction and stabilisation of a single motion-segment for FDI can adequately stabilise the spine and lead to excellent functional outcomes.
INTRODUCTION: Numerous in-vitro studies demonstrating increased stress at levels adjacent to a lumbar fusion have raised concerns of accelerated degeneration. However, the significance of this increased stress in the in-vivo setting remains unclear, especially with long-term follow-up. The objective of this study is to assess the level of degeneration on MRI in this same cohort of patients at a minimum of twenty years follow-up. METHODS: Twenty-five patients undergoing one or two level anterior lumbar interbody fusion at the L5-S1 or L4-5 levels with a minimum of twenty-years follow-up were identified. Only patients with normal pre-operative discograms at the level adjacent to the fusion were considered in this study. MRI scans were performed and evaluated for any evidence of degeneration by an independent radiologist. Advanced degeneration was defined as either: (1) absence of T2 signal intensity in the disk, (2) disk herniation, or (3) spinal canal stenosis. RESULTS: Advanced degeneration was identified in five (20%) patients, with three (12%) being isolated to the adjacent level. Fourteen (56%) other patients had evidence of early degeneration in their lumbar spine. Overall, eight (32%) patients had some evidence of degeneration isolated to the level adjacent to the disk whereas seven (28%) patients had multilevel degeneration and four patients (16%) had degeneration in their lumbar spine but preservation of the adjacent level. DISCUSSION AND CONCLUSION: Without a control group, it is difficult to make firm conclusions on whether the changes seen on MRI represent the natural history of spinal deterioration or represent accelerated degeneration. However, after twenty years, only a handful of patients developed advanced adjacent level degeneration. Furthermore, the majority of degenerative changes seen occurred over multiple levels or at levels not adjacent to the fusion, suggesting that changes seen may be more likely related to constitutional factors inherent within the individual as opposed to the increased biomechanical stresses at the adjacent levels.
INTRODUCTION: 360 degree combined anterior and posterior fusion is an accepted surgical treatment for the management of discogenic back pain. Controversy exists to the optimal technique of posterior fixation. Proponents of translaminar screw fixation cite lower morbidity as a result of less dissection. Despite reports of high fusion rates with this technique, there are concerns over the biomechanical inferiority of this construct compared to pedicle screw fixation. Previous studies on translaminar screws have used only plain radiographs to assess fusion. The objective of this paper is to compare radiographic outcomes, using high definition CT scans, and clinical outcomes between these two methods of posterior fixation. METHODS: During 2001, 31 patients underwent combined anterior and posterior fusion by the two senior surgeons for the management of back pain. Anterior interbody fusion was performed using the Syncage in all patients. 16 patients underwent translaminar screw posterior fixation and 15 underwent pedicle screw posterior fixation. Fusion was assessed by high definition CT scan at one year post-operatively. Function was assessed with pre- and post-operative Low Back Outcome Score and visual analogue scores. RESULTS: Minimum follow-up was 12 months. The incidence of pseudarthrosis in the translaminar group was over 75% which was five times greater than that seen in the pedicle screw group (p = 0.01). There were trends towards greater improvements in the LBOS and VAS scores in the pedicle screw group and amongst those patients who achieved a successful fusion. There were two surgical complications in the translaminar screw group and one in the pedicle screw group. DISCUSSION: With the numbers that are available, there are no clinical differences between the two methods of fixation, although there were trends towards improved function and reduced pain in the pedicle screw group. Furthermore there does not appear to be any difference in regard to complications. However, translaminar screws are associated with a significantly higher rate of pseudarthrosis compared to pedicle screws.
