The mean functional outcomes were 2.1 points (range, 0 to 4 points) for the VAS and 65.3 points (range, 52 to 75 points) for the Low-Back Outcome Score in the non-fusion group and 2 points (range, 0 to 4 points) for the VAS and 65.8 points (range, 55 to 75 points) for the Low-Back Outcome Score in the fusion group. The functional outcomes were similar between these two groups at the time of the latest follow-up using the Low-Back Outcome Score and the VAS for back pain (Table II). Neither nonunion nor postoperative infection was observed in either group at the time of the latest follow-up. On the basis of the Frankel grading system24, the neurologic status remained unchanged at the time of the latest follow-up as compared with that at the time of the two-year follow-up20.
Power analysis showed that G*Power reached 0.99 for the parameter of regional segmental motion. However, G*Power for the other parameters was insufficient to reach a conclusion.
The goals of treatment for spinal injuries are the restoration of a pain-free state and the preservation of the dynamic and protective function of the spine. In general, a surgical approach is chosen in cases in which conservative treatment is unlikely to produce satisfactory results25. The roles of spinal instrumentation are fracture reduction, maintenance of reduction, rigid fixation, and enhancement of osseous union or fusion. Several transpedicular screw instrumentation systems have been reported to have satisfactory results in treating burst fractures of the thoracolumbar and lumbar spine with fusion12,13,15. However, satisfactory results have also been reported, using the VAS for back pain, the Low-Back Outcome Score, or the Short-Form 36 (SF-36), with the non-fusion method for posterior fixation in a number of studies2,17-19, as well as in our previous work20.
Significant progression of regional kyphosis was observed as time went on in both the non-fusion and fusion groups, but without significance between the two groups. However, significance was observed in progressive kyphosis with time (14.1°) compared with the immediate postoperative kyphotic angle (2.8°), regardless of non-fusion or fusion. The same phenomenon was also reported in loss of correction with either fusion17,26,27 or non-fusion2,17,18. Defino and Canto26 reported progressive kyphosis at the final follow-up, even when using transpedicular bone-grafting along with posterolateral fusion to prevent further progressive kyphosis. On the basis of these reports, progressive kyphosis may be inevitable in spite of fusion, and the residual deformity did not correlate with the symptoms at the time of follow-up9.
Removing implants was suggested at one year postoperatively for those patients in the non-fusion group, because of the possibility of implant failure. For those patients in the fusion group, implants were removed only when the patient requested it. In Taiwanese culture, many people believe it is not good for one’s health to have metallic implants inside the body. Therefore, nine patients in the fusion group strongly requested removal of the implants, either for cultural reasons or back soreness. In the non-fusion group, eighteen patients underwent another surgery of implant removal, and the other four patients did not want another surgery. In all, eight patients had screw breakage: three patients in the non-fusion group and five patients in the fusion group.
A small, insignificant decrease in the injured vertebral body height was found in our study. Similar results were also noted in other reports17,26,27, which used different methods to evaluate absolute height (measured in centimeters) or relative ratio to adjacent vertebrae (measured in percentages). Therefore, the decreased vertebral body height may not play an important role in progressive kyphosis.
Haschtmann et al.28 concluded that vertebral end-plate trauma induces intervertebral disc cell apoptosis and necrosis in both nucleus and anulus tissues. Burst fracture could also contribute to either superior or inferior end-plate fracture at the injured vertebrae. Therefore, either the superior or inferior disc heights at the injured vertebrae would inevitably decrease because of further disc degeneration caused by apoptosis associated with the prior injury17,26,27.
As a result of our study, we believe that the progressive loss of disc height at the injured disc plays a more important role in worsening kyphosis than the mild degree of decreased vertebral body height. Wang et al.17 also concluded that the collapse of the disc space was the major contributor to the loss of correction.
In this study with a follow-up of at least ten years, we found that regional segmental motion could be preserved with a mean motion of 4.2°, compared with 4.6° in the prior two-year follow-up. The mean motion of the injured intervertebral disc was 0° and the mean motion of the uninjured intervertebral disc was 4.0° (range, 3° to 8°). This indicated that most of the regional segmental motion may be attributed to the uninjured intervertebral disc. In the fusion group, the regional segmental motion remained similar to that measured at the two-year follow-up, because of the solid union at the posterior portion of these fused motion segments.
This study had several limitations. It was not a multicenter trial and the patient number enrolled in both groups was small, with less-than-desired power. Therefore, the comparison may not truly reflect substantive differences between these two groups. We made efforts to contact all patients to perform the latest follow-up, although there were still difficulties in conducting a thorough follow-up because of individual factors. Moreover, the G*Power in several parameters was not enough to reach a conclusion regarding those parameters, and we did not check the intraobserver and interobserver reliability, which has been reported to have approximately 5° to 7° of interobserver variability22.
In conclusion, this study found that radiographic and functional outcomes were similar between the non-fusion group and the fusion group after short-segment transpedicular screw fixation in thoracolumbar and lumbar burst fractures, and regional segmental motion in the non-fusion group was maintained compared with that at the two-year follow-up. The advantages of the non-fusion procedure reported in our previous study20 were fewer bone graft donor site complications, the saving of more motion segments, and reduced blood loss and operative time. We conclude that posterior fusion with autograft need not be a routine procedure for surgically treated thoracolumbar and lumbar burst fractures.
A figure showing the serial change of injured vertebral body heights at different follow-up times is available with the online version of this article as a data supplement at jbjs.org.
NOTE: We thank Shin-I Huang from the Biostatistics Task Force, Taipei Veterans General Hospital, for statistical assistance.
A commentary by Daisuke Togawa, MD, PhD, is linked to the online version of this article at jbjs.org.
Investigation performed at the School of Medicine, National Yang-Ming University, and the Department of Orthopedics and Traumatology, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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