Traumatic spinal fractures of the thoracolumbar area represent approximately 90% of all spinal fractures; these injuries can result in loss of neurological function, pain, disability, and deformity, and represent a great economic burden to society .
Although short-segment stabilization approach, one level above and one level below, has high failure rate, it become preferred approach after renovation by addition of screws into the fractured level (index level). Several studies were done to ensure biomechanical stability of this short construct, and most of studies revealed its low failure rate and high pull out resistance .
In a prospective, randomized study of 80 patients, Farrokhi et al. in 2010 found that placement of pedicle screws into the pedicles of the fractured level during short-segmental fixation for thoracolumbar fractures led to better kyphosis correction, fewer instrument failures, and comparable or better clinical outcomes .
Eno et al. in 2012 found that pedicle screw fixation at the fractured level did not achieve greater correction of the segmental kyphotic angle compared to conventional intersegmental fixation; however, pedicle screw fixation more effectively restored the height of the fractured vertebra. Recovery of height is as important as the recovery of the angle, and it is helpful for the recovery of the integrity in the adjacent segments and the whole spine .
Interestingly, the additional pedicle screw fixation (six-screw fixation) at the fractured vertebra allowed patients to ambulate approximately 10 days earlier than patients who underwent conventional four-screw intersegmental fixation . On the other hand, our study results revealed that pedicular screws into the fracture level in short-segment fixation can correct the kyphotic angle provided that kyphotic angle range from 10° to 25° with minimum correction angle 4° and maximum correction angle 14°.
Adding bilateral index level screws to short-segment fixation increased the stability of the construct by 25%. The increase in stability was significant during flexion and lateral bending .
In vitro burst fracture model with pig spines was done to compare short fixation (so-called one above–one below) with short fixation plus intermediate screws. They found that intermediate screws significantly decreased segmental flexibility in all axes of motion by an average of 26%. The reduction in flexibility was least prominent during axial rotation .
The short segment group has less pain in immediate post-operative evaluation than long segment group in whom more analgesia (opioid analgesia) was needed. Pain follow-up of all cases every 3 months over 1 year by VAS (visual analogue scale) revealed rapid pain relief among short segment group than long segment group, and the pain became minimal after fusion had occurred. Both groups had shown reduction of the ODI score with significant changes at the 1-year follow-up. Kim et al. had addressed outcomes including pain in different three groups underwent short-segment stabilization with screws in index vertebra; the first group (n = 26) was similar to our short segment group. The mean VAS scores were 7.6 before surgery and 3.0 at the last follow-up, while in our group, VAS scores were 5.59 and 1.39 respectively .
Angle of correction
We notice that there is initial less correction of kyphotic angle then the correction became more corrected in both groups till fusion occurs after about 6 months to 1 year.
Mahar et al. in 2007 concluded that an average of 15° of kyphosis correction could be obtained using limited posterior segmental fixation. This is likely better than traditional, non-segmental pedicle screw fixation. This compared to our study in which the average amount of correction for short-segment fixation was 14.2°. However, the amount of correction was slightly higher with long-segment fixation (16.9°) but no significant statistical difference was found, which is similar to the findings of Guven et al. in 2007 who found no statistically significant difference regarding the correction between long-segment fixation and short-segment fixation with pedicle screw at the fractured level. But still more than 70% of cases of long-segment fixation had more than 70% kyphosis correction. On the other hand, short-segment fixation and poor initial post-operative kyphosis correction were both significantly associated with correction loss .
In a systematic review by Verlaan et al. in 2005 where different modalities for the treatment of traumatic thoracic and lumbar spine fractures were analyzed. Their review included posterior long and short constructs, anterior-only fixation, and circumferential fixation. They concluded that regardless of the severity of injury, no technique was able to correct and maintain the fracture segment to the physiological level and kyphotic angle. This statement was reaffirmed by Wang et al., who also found no correlation between the degree of kyphosis and residual back pain .
More studies are needed to understand the effect of short fixation on adjacent levels and on the maintenance of deformity correction in the thoracolumbar spine, either as a stand-alone procedure or as an adjunct to anterior fixation.
The follow-up evaluation was limited to a 1-year period which is considered to be a short term.
Many patients with multilevel fractures have been excluded from the study. The need for assessment of multiple adjacent index levels fusion should be taken in consideration in the upcoming research.