AbstractObjective Approximately 90% of spinal fractures occur at the thoracolumbar (T-L) junction and may be accompanied by neurological symptoms, in which decompression and post-fixation are generally performed. However, decompression surgery can aggravate patients’ symptoms due to adverse incidents, such as developing postoperative hematomas or iatrogenic spinal cord injury. This study compared the surgical and radiographic outcomes of patients with T-L junction burst fractures and neurological deficits who underwent direct or indirect decompression.
MethodsWe retrospectively reviewed all patients who had undergone posterior surgical treatment for T-L junction burst fractures with neurologic deficits. Patients were classified according to the procedure: indirect decompression (group 1) or spinal decompression through laminectomy and facetectomy (group 2). Clinical results and radiologic findings were compared between the two groups for 2 years.
Results Among 57 patients who met the inclusion criteria, 29 were categorized into group 1, and 28 were categorized into group 2. Group 1 had a statistically significantly lower Oswestry Disability Index score than group 2 at the final follow-up visit (p=0.03). In group 1, both the T-L junction angle and wedge angle of the injured vertebrae improved significantly, both immediately after surgery (p=0.02 and p=0.01, respectively) and at the final follow-up visit (p=0.01 and p=0.01, respectively). In group 2, the difference between the pelvic incidence and lumbar lordosis was significantly greater than in group 1 at the final follow-up visit (p=0.02).
INTRODUCTIONApproximately 90% of spinal fractures occur at the thoracolumbar (T-L) junction7,15,28), including burst fractures and T-L vertebral collapse. T-L burst fracture is defined according to the presence of fractures or comminutions in both the anterior and middle columns, with the bony fragments retracted into the spinal canal5). A T-L burst fracture with a fractured and reverse-oscillating posterior vertebral wall can cause neurological deficits when bone fragments persist in the spinal canal during or after trauma19,27). Without appropriate treatment, these complications substantially affect physical health, occupational daily activities, and overall quality of life18).
Surgery is primarily indicated to relieve spinal cord compression and restore neural function4,20,26). In patients diagnosed with fractures of the vertebral bodies and posterior elements with some degree of misalignment of the spine or those with T-L junction fractures presenting with spinal canal injuries and neurological symptoms, timely decompression and internal immobilization should be performed to restore vertebral body height and vertebral canal volume. The goal is to restore spinal stability as soon as possible in accordance with current medical guidelines14,21).
Various surgical options are available for the management of T-L burst fractures, including posterior fixation and decompression, as well as direct anterior decompression through vertebral resection6,10,12,22). Posterior decompression and fixation are the most commonly implemented methods. However, decompression can aggravate neurologic symptoms, with postoperative hematomas or spinal cord injury commonly presenting in patients who have difficulty coagulating13). In contrast, indirect decompression can decompress nerve tissue without excising the compressed tissue. This method is primarily performed through distraction between the two vertebrae, which opens the neural foramen and increases the epidural space. Therefore, this technique allows for nerve tissue decompression without excision of the compression fragment. Distraction and ligamentotaxis indirectly lead to reduced fracture fragments, resulting in restoration of corpus height, kyphosis correction, and canal widening16,30).
We ought to establish the surgical outcomes of indirect decompression in patients with T-L junction burst fractures presenting with neurological deficits. Toward this goal, we retrospectively evaluated the surgical outcomes of patients who underwent indirect decompression surgery and compared these outcomes to patients who underwent posterior fixation after laminectomy.
MATERIALS AND METHODS1. Demographic EvaluationThe institutional review board at the participating medical center approved this study. Patients who underwent surgery at our tertiary medical center between August 2013 and January 2020 for traumatic T-L junction fractures with neurological deficits were retrospectively reviewed.
We included patients who (1) underwent posterior fusion surgery for a single-level burst fracture of the T-L junction from the T11 to L2 level with traumatic spinal cord injury; (2) had no prior history of spinal surgery; (3) had received surgical treatment within 48 hr after trauma; (4) only had radiating pain without motor function impairment; and (5) had a minimum follow-up of 24 months.
We excluded patients who (1) had a follow-up period shorter than 24 months; (2) presented with multi-level spinal fractures; (3) had a history of previous posterior spinal surgery; (4) had severe comorbidities (e.g., cancer metastasis, infectious diseases) that may adversely affect bone healing; and (5) experienced neurological defects such as motor weakness or cauda equina syndrome. Indirect decompression surgery was performed in patients for whom direct decompression surgery could not be performed due to age, underlying disease, and medications. Direct decompression and post-fixation surgery were performed in all other patients.
Demographic data were collected through questionnaires administered to all patients, including data on age, sex, underlying disease, injured vertebra level, smoking history, body mass index (BMI), surgical details, a range of follow-up information, data abstracted from electronic medical records, estimated blood loss during surgery, and operative times. We did not obtain consent for participation from the enrolled patients owing to the retrospective nature of the study. Thus, the normal requirement for informed consent was waived during the ethics review process.
2. Pain and Quality of Life EvaluationPatient-reported questionnaires were administered before surgery during outpatient clinic visits. Pain levels were quantified using a visual analog scale (VAS) with respect to back and leg pain both pre- and post- operatively (immediate, 12-month, and 24-month follow-up). The effects on disability and quality of life were measured using the Oswestry Disability Index (ODI) questionnaire at the same time points. A satisfaction questionnaire evaluating the received treatment was also administered. In cases where it was difficult for patients to complete a questionnaire, results were verified by a telephonic interview conducted with a member of the study staff.
3. Operative TechniqueAll patients were placed in a prone position with a Wilson frame adjoining the thoracic and iliac spines, thus straining the anterior columns of the spine to reset the spinal curvature. A midline skin incision was made, and the paravertebral muscles were separated bilaterally from the spinous process to expose the lamina and facet joint. The pedicle of the fractured vertebral body was evaluated using C-arm fluoroscopy. Segmental screws were inserted into one or two vertebrae above and one vertebra below the level of the fracture via the freehand technique. Six to eight pedicle screws were inserted into the pedicle. Polyaxial pedicle screws were inserted into the upper and lower normal vertebrae, and axial pedicle screws were inserted into the fractured vertebrae. A screw 5 to 10 mm shorter than the vertebra was inserted into the pedicle screw of the upper and lower normal vertebrae. The connecting rod was then inserted and fixed with a cap.
In group 1 (the indirect decompression group), indirect decompression can be achieved through distraction by identifying areas with burst fractures, dura compression, and segmental kyphosis with a C-arm and performing distraction between the posterior segmental instruments above and below the area (Fig. 1).
In group 2 (the direct decompression group), we performed posterior decompression, including laminectomy and facetectomy, to widen the spinal canal when cord compression was observed following a fracture.
4. Radiographic EvaluationWe performed magnetic resonance imaging (MRI) and multi-slice computed tomography imaging of the T-L spine in all patients. Using sagittal MRI images, we calculated dural sac compression due to epidural hematoma or bone fragments. The dural compression ratio presents the ratio of compressed to supposedly normal dura at the level of the injury. This ratio was calculated using the following equation: (1 − C/[(A + B)/2]) × 100)11) (Fig. 2).
We measured the angle of the T-L junction, thus evaluating kyphosis according to the Cobb method9). The Cobb angle was measured from the upper-end plate of T10 and the lower-end plate of L2. We also measured spinal parameters. These parameters included thoracic kyphosis (TK; T5-12), lumbar lordosis (LL; L1-S1), and pelvic incidence (PI)-LL mismatch. In addition, we recorded the wedge angle (WA) of the injured vertebral body. All radiological parameters were checked preoperatively, immediately postoperatively, and at the final (24-month) follow-up visit.
5. Statistical AnalysesContinuous variables were described as the mean ± standard deviation, and categorical variables were expressed as frequencies or percentages. Additionally, Student’s t-test, χ2, and Fisher’s exact tests were used to determine statistically significant differences in radiological and clinical outcomes between the two groups. All statistical analyses were performed using SPSS Statistics for Windows, Version 17.0 (IBM Corp., Armonk, NY, USA). A p-value of less than 0.05 was considered statistically significant.
RESULTS1. Demographic AnalysisA total of 57 patients were enrolled in this study. Among these patients, 29 were categorized into group 1, and 28 were categorized into group 2. Among those in group 1, 19 were taking anticoagulants, 7 were ≥80 years old, and 3 had a hematologic disease. Serious complications, such as nerve root and spinal cord injuries, screw malposition, broken screws, and rods, hematomas pressing on the spinal cord, or wound infections, were not observed in enrolled patients. Age, sex, underlying disease, fractured vertebra level, bone marrow density, BMI, and smoking history distributions did not significantly differ between the two groups (Table 1).
2. Comparative Analysis of Surgical InformationIntraoperative bleeding volume was lower in group 1 vs. group 2; however, this difference was not statistically significant. In addition, there were no significant differences in the surgical level at which fixation was performed or the preoperative dura compression ratio. However, the indirect decompression group had a significantly shorter mean operative time than the direct decompression group (31 min, p=0.03; Table 2).
3. Clinical OutcomeWe found that the VAS and ODI scores before surgery as well as immediately after surgery were lower in group 1 than in group 2, with no significant differences between the two. However, at the final follow-up, patients in group 1 had significantly lower ODI scores compared with those in group 2 (p=0.03; Table 3).
4. Comparative Radiological ResultsNo significant between-group differences were observed for any of the pre-surgical radiologic parameters. Regarding the WA of the injured vertebral body, it was confirmed that the kyphotic angle was significantly smaller in group 1 compared to that in group 2 immediately after surgery (p=0.01) and at the last follow-up (p=0.01). In the angle of T-L junction, a statistically significantly smaller kyphotic angle was observed in group 1 immediately after surgery (p = 0.02), which was also confirmed at the final follow-up (p=0.01) (Fig. 3, Table 4). No significant differences in TK or LL were observed between the two groups. Group 2 had a larger PI-LL discrepancy than Group 1 at the final follow-up visit (p=0.02; Table 4).
DISCUSSIONThis is the first study to compare the clinical and radiological features of patients with T-L junction burst fractures presenting with neurological symptoms who underwent indirect decompression surgery with those of patients who underwent direct decompression surgery.
The T-L junction segment is located at the physiological stress concentration points of the spinal cord15). Burst fractures typically lead to various symptoms caused by spinal cord compression due to the presence of bone fragments and epidural hematomas. Decompression and post-fixation are normally performed in the presence of neurological symptoms. However, direct decompression of the spinal cord area can aggravate hematomas or spinal cord injuries and cause dural tearing29). Moreover, older age, anticoagulant use, and many risk factors during surgery have been identified as causes of postoperative spinal epidural hematoma3,8,13,25). Therefore, we performed indirect decompression surgery for these at-risk patients.
Many studies have been conducted on partial lordosis and total spinal alignment correction using indirect decompression with a posterior approach1,2,17). In our study, the indirect decompression group showed lower WA and T-L junction angles. However, no significant differences were observed with respect to TK and LL. Future studies performing surgeries involving larger numbers of patients and more levels of the spine are needed.
In terms of PI-LL mismatch, we found a significant difference in the direct decompression group immediately after surgery. Schwab et al.23) viewed PI-LL mismatch as a key parameter related to postoperative patient disability and health-related quality of life. Seo et al.24) reported that a T-L junction Cobb angle larger than 10.5° immediately after surgery was associated with unfavorable radiological outcomes, which, in turn, were associated with poor clinical outcomes. In the current study, we confirmed that ODI scores were worse in the direct vs. indirect decompression group. The T-L kyphotic angle in the direct decompression group was 10.5° or higher. Consequently, we confirmed that clinical radiological results improved in the indirect vs. direct decompression group. Furthermore, there was less improvement in kyphotic angle in the direct vs. indirect decompression group, resulting in a larger T-L junction kyphosis and whole spine malalignment, which consequently adversely affected ODI score improvements.
In addition to the substantial strengths of this study, we acknowledge several limitations. First, we enrolled a small sample size selected from a single medical center. Moreover, comparative study groups were lacking in the current study design. In particular, comparisons were not made according to various fracture shapes, e.g., pedicle fractures. Further comparative studies involving larger case series and fractures of various shapes are needed to confirm our findings in patients with T-L junction vertebral fractures. Second, the follow-up period was relatively short. Additional studies with longer follow-up periods are required to validate the neurological changes observed in this study.
CONCLUSIONIn this study, the clinical and radiological results of direct and indirect decompression were compared. We sought to confirm the usefulness of indirect decompression in patients with T-L junction tear fractures and neurological symptoms when direct decompression was difficult. Indirect decompression was associated with better clinical outcomes and improved radiographic alignment compared to direct decompression. Further studies with more patients and longer duration are needed. However, our findings will serve as a reference to guide future research and provide direct information for medical guidelines and clinical decision-making.
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