Non-operative management of stable thoracolumbar spinal fractures has been advocated even in the presence of kyphotic collapse (Chow et al. 1996; Shen et al. 2001; Cantor et al. 1993). Our results show that correction of these fractures offers significant benefit to patients in terms of ODI scores, return to work, time spent in hospital and secondary complications. If the spine is left with a deformity after fracture, then this has significant effects on spinal balance and the vertebral levels above and below (Xiang-Wang et al. 2008; Shen and Shen 1999). The older the patient, the less able the spine will be to compensate, and even in younger patients one would expect the spine to decompensate in later years with consequent disability. We believe that fractured spines should be treated like any other bony injury – i.e. to reduce, hold and rehabilitate, and that an unreduced deformed fracture is likely to cause disability.
Traditional open operations on the spine do lead to a legacy of soft tissue damage, particularly from stripping the posterior paraspinal muscles away from the spine (MacNab et al. 1977). A fusion adds an additional mechanical insult by creating a permanent stiff segment with stress transfer to other levels. If no fusion is carried out, then damage to those paraspinal muscles results in functional loss as those muscle groups are required to support and move those segments (MacNab et al. 1977; Choll 2010). Many surgeons try to limit the soft tissue damage caused by restricting the number of segments spanned by any construct to one level above and below the fractured vertebra. Short segment fixations such as these from the posterior aspect alone have a significant incidence of loss of correction and metalwork failure (Xiang-Wang et al. 2008; Alanay et al. 2001; Tezeren and Kuru 2005). Anterior procedures provide greater structural support to short segment posterior constructs such as these, but carry a significant complication risk and morbidity (Kim et al. 2009). Anterior procedures for thoracolumbar fractures also means taking down the diaphragm and violating the chest, which is best avoided if possible, particularly if patients have concomitant chest trauma. Stabilising the spine in these patients however has marked benefits for the recovery from associated trauma to other organs (Bellabarba et al. 2010).
MIS offers the benefits of longer segment posterior correction and fixation without the damage to soft tissues and paraspinal muscles that traditional open surgery involves (Choll 2010; Hatta et al. 2009; Smith et al. 2010). The fractured segment is stable once healed (Lindsey et al. 1993; Wang et al. 2006) and allows secondary removal of metalwork to remobilise those segments spanned (Kim et al. 2011). MIS techniques allow this without further soft tissue trauma. MIS techniques must satisfy certain criteria if they are to show benefit. There must be no compromise when using these techniques, and the surgeon must be able to achieve everything that would be attained with open surgery. Implants must be able to be placed as reliably and accurately as with open techniques. Fractures and deformity must be able to be reduced as well and reliably as with open techniques. The desired outcome should be achieved as well as with open techniques. Our study demonstrates that our techniques achieve this, and that our techniques are safe, reliable and reproducible.
Another issue is equipment and its availability. There are now a number of different systems available on the market for MIS techniques, but virtually all rely on tubes attached to the pedicle screws to guide and seat the rods allowing reduction into the pedicle screw. These systems all have a disadvantage, because they can only be used with polyaxial screws to allow for pedicle screw angle variation. This is because a tube attached to the screw head magnifies this variation, and polyaxiality is therefore required to align the screws/tubes to allow passage of the rod. This means that with these systems, the pedicle screw itself cannot be used as a vehicle to reduce a fracture or deformity. Our techniques do not have this disadvantage, because we have adapted a system designed for open surgery directly for MIS techniques. The reduction is carried out directly into the screw head on the surface of the bone, which means that we can use monoaxial or solid screws. When the reduction clamps are applied, this allows the unit to behave like a Schanz pin/screw, thereby permitting strong reliable active correction of the fracture and deformity with the pedicle screw.
Our conservative methods of treatment were standard and part of an agreed departmental protocol. Patients were assessed for brace tolerance, pressure areas and compliance (although all patients assured us they were complying), psychological factors (especially with bed rest) and problems with immobility (DVT/PE, pressure areas, bowel & bladder habit, chest problems). We have an aggressive physiotherapy protocol with regular rolling, in bed exercises & chest protocols. These protocols are comprehensive and regularly reviewed to ensure best practice.
There was a clear difference in return to work between open and conservative groups in our paper in contrast to the paper by Wood et al. In their paper, they found no difference in return to work between surgical and conservative methods (Wood et al. 2003). All of our patients who underwent MIS returned to work. This may be related to our young patient cohort. The mean ages of our patients has been stated whereas solely an age range of 18–66 years was mentioned in the paper of Wood et al.
Additionally, the paper by Wood et al. does not have the degree of kyphosis that our patients did. In their paper, the average degree of kyphosis pre-op was 10° and 5° post- surgery (Wood et al. 2003). Most surgeons would accept a pre-op kyphosis post injury of 10° but this is patient dependent. This also may indicate less violence in their patients, more stable fractures, and that the degree of kyphosis plays more of a part than their paper might perhaps gives credit to.
One would expect that for their cohort of patients with such a low degree of deformity that operative treatment would not be expected to confer an advantage. The patients in our study, by contrast, represent an entirely different group. In relation to this, the ODI scores in their paper was 20.75 at final follow up in the operative group, and 10.7 for the conservative group (Wood et al. 2003). Our ODI scores are much lower for our MIS group at 4 points, and higher for our conservative group at 32 points, which may reflect the greater degree of violence involved and the effects of a greater degree of post-traumatic kyphosis. Our MCID scores were smaller than previous studies for the ODI due to narrow standard deviations (Copay et al. 2008; Ostelo et al. 2008; Hagg et al. 2003).
We accept that the limitations of our study include the lack of variability in patients within the cohort. We have adopted strict inclusion criteria to try and make patient groups as comparable as possible. Patients were not randomised to treatment but were given the option after full discussion of the risks and benefits with the senior author of treatment options of surgery and conservative treatment. Additionally this is a study of short term follow up and longer term outcome data is required to assess the long term sequelae of such injuries.