The impact of fixed segment length on the surgical outcomes of single-segment lumbar burst fractures: shorter segments are more prone to the formation of local stable osteophytes: a retrospective observational study
Article information
Abstract
Study Design
Retrospective observational study.
Purpose
This study investigated the impact of long-segment and short-segment pedicle screw fixation on degeneration indicators, particularly stable osteophytes, in the treatment of single-segment lumbar burst fractures.
Overview of Literature
Current research mainly focuses on clinical indicators such as operation time, Visual Analog Scale (VAS) pain scores, and imaging indicators like the Cobb angle correction rate. However, there is a paucity of research on the indicators of intervertebral disc degeneration at fixed segments (such as bone spur formation, vacuum phenomenon in the disc, and Modic changes). As the health status of the intervertebral disc is closely related to spinal stability, this study provides a comprehensive evaluation of the efficacy of two surgical techniques, providing a more precise basis for clinical treatment.
Methods
This was a retrospective analysis of a cohort of 64 patients with single-segment lumbar burst fractures. Among them, 38 patients underwent posterior long-segment pedicle screw-rod fixation (long-segment group), while 26 cases received posterior short-segment pedicle screw fixation (short-segment group). Changes in degeneration indicators within the fixation area, including osteophyte formation, intervertebral disc vacuum sign, and intervertebral height, were examined.
Results
All 64 patients completed surgery and were followed up for at least 24 months. At the final follow-up at 24 months, the short-segment fixation group exhibited a higher osteophyte formation score than the long-segment fixation group. However, no significant between-group differences were observed in the incidence of intervertebral disc vacuum sign or intervertebral height loss rate.
Conclusions
After a 2-year follow-up, the short-segment fixation group demonstrated a similar intervertebral height loss rate and intervertebral disc vacuum sign incidence compared to the long-segment fixation group, but a higher rate of stable osteophyte formation.
Introduction
Lumbar burst fractures (LBFs) are often caused by high-energy trauma and can lead to pathological changes that compromise vertebral integrity, spinal stability, and potentially cause concomitant spinal cord and nerve damage [1]. Prompt surgical treatment is crucial for patients with LBFs. Lumbar pedicle screw-rod fixation surgeries can be broadly categorized into long-segment and short-segment fixation procedures, based on the number of vertebrae stabilized in the lumbar spine.
In recent years, numerous studies have compared the efficacy of long-segment and short-segment treatments for single-segment LBFs. While short-segment fixation may be associated with long-term complications, including internal fixation failure and residual kyphotic deformity, long-segment fixation entails the sacrifice of additional spinal motion segments, thereby increasing surgical trauma. A comprehensive review of existing literature suggests that both long-segment and short-segment approaches have their advantages [2–5].
However, previous studies have primarily focused on perioperative indicators such as operation time, intraoperative blood loss, length of hospital stay, Cobb angle, vertebral height, and screw loosening or breakage, with rare studies comparing degeneration indicators such as osteophyte formation at instrumented segments, loss of vertebral height, and vacuum phenomenon in intervertebral discs [6–8].
This study investigated patients with single-segment LBFs who underwent either long-segment or short-segment pedicle screw-rod system internal fixation surgery, focusing on the changes in degeneration indicators such as osteophyte formation in the lumbar fixation area, vacuum phenomenon in intervertebral discs, and intervertebral space height. The aim was to provide objective clinical evidence to inform surgical decision-making for LBFs.
Materials and Methods
General information
This retrospective cohort study was exempt from informed consent requirements. This study was approved by the Institutional Review Board (IRB) of Hunan Provincial People’s Hospital (the First Affiliated Hospital of Hunan Normal University; IRB no.,2025114). We reviewed patients with single-segment LBFs who underwent surgical treatment at the Department of Spine Surgery, Hunan Provincial People’s Hospital (the First Affiliated Hospital of Hunan Normal University), between January 2019 and December 2021. After screening, 64 patients met the inclusion criteria and were enrolled in the study. Patients were divided into two groups based on the surgical approach: the long-segment group (n=38), which received posterior long-segment pedicle screw-rod fixation, and the short-segment group (n=26), which underwent posterior short-segment pedicle screw-rod fixation.
Baseline patient characteristics
The long-segment group consisted of 28 males and 10 females, with a mean age of 44.8 years (range, 25–65 years). The distribution of fractured vertebrae in this group was as follows: L1 (19 cases), L2 (13 cases), L3 (four cases), and L4 (two cases). The short-segment group comprised 19 males and seven females, with a mean age of 43.1 years (range, 27–64 years). The distribution of fractured vertebrae in this group was as follows: L1 (18 cases), L2 (two cases), L3 (three cases), and L4 (three cases). Preoperative informed consent was obtained from all patients, and relevant examinations were completed prior to surgery.
Definitions of long-segment and short-segment fixation
Long-segment fixation involves fixing the fractured vertebra and at least two adjacent vertebrae above and below it. Short-segment fixation only involves fixing the fractured vertebra and one adjacent vertebra above and below it.
Inclusion and exclusion criteria
The inclusion criteria were as follows: (1) single-segment traumatic LBF (Thoracolumbar Injury Classification and Severity [TLICS] score >4 points, Load Sharing score 5–8 points); (2) both sides of the pedicle of the injured vertebra intact; (3) age between 18 and 65 years.
The exclusion criteria were as follows: (1) pathological fractures; (2) history of spinal surgery; (3) severe fractures or serious organ injuries in other parts; (4) osteoporosis (T score <−2.5); (5) pregnancy; (6) loss to follow-up; and (7) cases with deep incision infection.
Surgical methods, indications, and rehabilitation plan
Under general anesthesia, patients were positioned prone with the abdomen suspended. C-arm fluoroscopy was used to confirm the location of the injured vertebra, and precise markings were made on the skin. A midline posterior incision centered over the injured vertebra was then made, exposing the injured vertebra and one or two adjacent vertebrae. Pedicle screws were implanted under fluoroscopic guidance to ensure accurate placement. In the long-segment fixation, the injured vertebra and two adjacent vertebrae above and below were fixed, whereas in the short-segment fixation, only the injured vertebra and one adjacent vertebra above and below were fixed. Lateral fluoroscopic views were used to verify that the lengths and positions of the screws were satisfactory. Appropriately sized pre-bent rods were then selected, and a vertebral distractor was used to distract the two sets of pedicle screws in a parallel manner. This allowed for reduction and fixation to restore vertebral height and physiological spine curvature. After the surgery, fluoroscopy was repeated to check for any displacement of the screws and the recovery of the height of the injured vertebra. Once satisfactory reduction was achieved, a drain was placed and the incision was sutured. Prophylactic antibiotics were administered for at least 3 days. Postoperative rehabilitation instructions emphasized the importance of ambulation with the protection of an external immobilization brace, while strictly avoiding bending or twisting movements of the waist. The immobilization period was maintained for at least 3 months or longer. Notably, at the commencement of the study, none of the patients had undergone removal of their internal fixation screws. Additionally, fusion procedure was not performed during the initial surgery for any patient.
Preoperative waiting time
All surgeries were performed within 7 days post-injury to standardize the biomechanical environment.
Indications for intraoperative decompression
Intraoperative decompression was indicated in patients presenting with preoperative decline in neurological function or radiographic evidence of spinal canal compromise, where bone fragments occupied more than half of the spinal canal’s cross-sectional area. The decompression technique involved unilateral or bilateral partial laminectomy while preserving the facet joints on both sides to minimize the impact on spinal stability.
Rehabilitation plan
A standardized postoperative rehabilitation protocol was implemented, involving the application of a rigid thoracolumbosacral orthosis (TLSO) for 3 months.
Surgical indications
A total Load Sharing score between 5 and 8, indicating moderate to significant instability.
Observational indicators
Data pertaining to surgical duration (minutes), intraoperative blood loss (mL), postoperative drainage volume (mL), and length of hospital stay (days) were obtained from anesthesia records, postoperative nursing records, and the hospital’s inpatient information system.
Regular follow-ups were conducted postoperatively, including assessments at baseline, 1 week, 3 months, and 24 months post-surgery. The following parameters were evaluated: Visual Analog Scale (VAS) pain scores, Oswestry Disability Index (ODI), neurological function based on the American Spinal Injury Association (ASIA) classification, anterior edge height of the fractured vertebra, and conditions related to screw-rod loosening, fracture, and displacement. Two researchers, blinded to the research protocol and grouping, independently completed the follow-ups, with the average of their assessments used as the final study result.
VAS
A 10 cm horizontal line is drawn on paper, with one end representing 0 (no pain) and the other end representing 10 (extreme pain). The middle section represents varying degrees of pain.
ODI
This index has a maximum score of 50 points, with higher scores indicating a more severe level of low back pain experienced by the patient.
Neurological function ASIA classification
The ASIA classification system categorizes spinal injuries into five levels (A, B, C, D, E). In this study, level A was scored as 5 points, level B as 4 points, level C as 3 points, level D as 2 points, and level E as 1 point.
Computed tomography (CT) imaging data of patients at 3 months and 24 months post-surgery were obtained through the hospital’s Picture Archiving and Communication System ver. 2.7.1.0 (Antai Innovation Technology Co. Ltd., Shenzhen, China). Relevant indicators were measured using the software’s built-in tools.
Types of osteophyte formation
Complete encapsulation type, where osteophytes connect the two adjacent vertebrae above and below the fractured vertebra, completely covering both sides and the front of the vertebra, scored 3 points. The bridged osteophyte type, where osteophytes connect the two adjacent vertebrae but only cover the sides or the front of the vertebra, scored 2 points. Incomplete type osteophyte formation characterized by localized osteophyte formation without bridging, scored 1 point. Lastly, the no osteophyte type, indicating an absence of osteophyte formation, scored 0 points (Fig. 1).
Osteophyte types: complete encapsulation (A), bridged osteophyte (B), incomplete osteophyte (C), and no osteophyte (D).
Vacuum sign
The vacuum sign is a radiographic finding that occurs when the intervertebral disc undergoes degeneration, leading to shrinkage and necrosis of the nucleus pulposus. This creates gaps within the disc, resulting in negative pressure that allows gases from surrounding blood or tissue, such as nitrogen or carbon dioxide, to enter and produce low-density images visible on X-rays or CT scans. The vacuum sign is scored as follows: (1) Complete: Both adjacent intervertebral discs exhibit the vacuum sign, scoring 2 points. (2) Partial: Only one of the adjacent intervertebral discs exhibits the vacuum sign, scoring 1 point. (3) None: Neither of the adjacent intervertebral discs exhibits the vacuum sign, scoring 0 points (Fig. 2).
Types of vacuum sign: complete (A), partial (B), and none (C).
Intervertebral height measurement
The intervertebral height was measured at 1 week, 3 months, and 24 months post-surgery (Fig. 3). This measurement specifically refers to the distance between the lower endplate of the upper vertebra and the upper endplate of the lower vertebra at the fractured site. The intervertebral height loss rate was calculated using the following formula:
Measurement of intervertebral height. “a” indicates the height of the intervertebral space above the injured vertebra. “b” indicates the height below the injured vertebra.
To calculate the intervertebral space height, the following steps were taken: The four corners of the intervertebral discs above and below the injured vertebra were identified. The two points along the direction parallel to the end plates were connected, and the distances between the two consecutive midpoints were measured and denoted as (a) and (b). The intervertebral space height was then calculated using the following formula: (a+b)/2.
Statistical methods
Data analyses were conducted using IBM SPSS ver. 26.0 (IBM Corp., Armonk, NY, USA). Normally distributed continuous variables were expressed as mean±standard deviation and analyzed using the independent samples t-test. Multi-group comparisons were performed using analysis of variance. Non-normally distributed continuous variables were analyzed using the rank-sum test, while categorical variables were analyzed using the chi-square test. All p-values of less than 0.05 were considered indicative of statistical significance.
Results
A total of 64 patients from both groups underwent successful surgery and completed a minimum follow-up of 24 months. During the follow-up period, there were no occurrences of screw-rod loosening, fracture, or displacement. Two patients (one each from the long-segment group and the short-segment group) experienced postoperative superficial incision infections, which were effectively treated with thorough debridement and enhanced antibiotic treatment.
Comparison of baseline data
At baseline, there were no significant differences between the two groups with respect to sex, age, disease duration or load-sharing score (p>0.05).
Comparison of surgical-related indicators
The surgical duration, intraoperative blood loss, and postoperative drainage volume were significantly higher in the long-segment group compared to the short-segment group (p<0.05) (Fig. 4).
Comparisons between the long-segment and short-segment groups. (A) Surgical duration, (B) intraoperative blood loss, and (C) postoperative drainage volume. *p<0.05 (statistically significant differences between groups).
Comparison of postoperative functional scores
Preoperative assessment
Preoperatively, there were no significant between-group differences with respect to the VAS scores, ODI scores, and ASIA grades (p>0.05).
Postoperative assessment (1 week, 3 months, and 2 years)
Both groups showed a significant decrease in VAS and ODI scores (p<0.01), and a significant increase in ASIA scores (p<0.01) compared to their respective preoperative values. However, at 2 years, there were no significant between-group differences in these respects (p>0.05).
Comparison of postoperative degeneration indicators in the fixed area
Osteophyte score
Preoperatively, the short-segment group scored 0.27±0.06, while the long-segment group scored 0.23±0.05. At 1 week postoperative, the short-segment group scored 0.35±0.08, while the long-segment group scored 0.32±0.06 with no significant between-group difference (p>0.05). At 3 months postoperative, the short-segment group scored 1.07±0.18, and the long-segment group scored 0.71±0.16. At 24 months postoperative, osteophyte score in the short-segment group (1.69±0.21) was significantly higher than that in the long-segment group (0.89±0.16; p<0.05). As shown in the table, preoperatively, none of the patients had an osteophyte score of three. However, 2 years post-surgery, 19 patients had an osteophyte score of three. The age of these patients ranged between 27 and 65 years. Among those with a load-sharing score of 5, there were three cases; among those with a load-sharing score of 6, there were four cases; among those with a load-sharing score of 7, there were seven cases; and among those with a load-sharing score of 8, there were five cases.
Vacuum sign score
Preoperatively, the mean Vacuum sign score in the short-segment and long-segment groups were 0.18±0.04 and 0.16±0.05, respectively. At 1 week postoperative, the scores were 0.25±0.06 and 0.22±0.05, respectively, while at 3 months postoperative, the scores were 0.53±0.19 and 0.48±0.14, respectively, with no significant between-group differences. Similarly, there was no significant between-group difference in Vacuum sign score at 24 months postoperative (0.75±0.14 and 0.62±0.16, respectively; p>0.05).
Intervertebral height loss
There were no significant differences between the short-segment group and the long-segment group with respect to intervertebral height loss at any of the time points (p>0.05). The details are shown in Tables 1–3 and Fig. 5A–C.
Comparison of degeneration indicators
Long-segment group
Short-segment group
(A–C) Osteophyte formation, presence of vacuum sign, and intervertebral height loss in the long-segment and short-segment groups at 1 week, 3 months, and 24 months postoperatively. (D, E) Correlations between osteophyte score, vacuum phenomenon score, and intervertebral space height loss.
Spearman rank correlation analysis
Spearman rank correlation analysis revealed a significant negative correlation between osteophyte scores and vacuum phenomenon scores at 2 years post-surgery (r=−0.3524, p<0.01) (Fig. 5D). Additionally, there was a significant negative correlation between osteophyte scores and the percentage of intervertebral height loss (r=−0.8511, p<0.0001) at 2 years post-surgery (Fig. 5E). This suggests that the formation of osteophytes may contribute to stabilizing the spine and reducing intervertebral disc degeneration.
Typical case presentation
Fig. 6 shows CT of long-segment fixation (A–E correspond to preoperative, 1 week postoperative, 3 months postoperative, 2 years postoperative, and 2 years postoperative [three-dimensional reconstruction] images, respectively). The osteophyte score was 0 at 1 week and 3 months postoperative, and 2 at 2 years postoperative; the vacuum sign score was 0 at 3 months and 1 at 2 years; the intervertebral height loss rate was 6.73% at 3 months and 8.79% at 2 years.
Computed tomography images corresponding to different time points: preoperative (A), 1 week postoperative (B), 3 months postoperative (C), 2 years postoperative (D), and 2 years postoperative (three-dimensional reconstruction) (E).
Fig. 7 shows typical CT changes in short-segment fixation (A–E correspond to preoperative, 1 week postoperative, 3 months postoperative, 2 years postoperative, and 2 years postoperative [three-dimensional reconstruction] images, respectively). As shown in Fig. 7A, the preoperative CT image is presented. The bone spur score was 0 at 3 months and 3 at 2 years; the vacuum sign score was 0 at both 3 months and 2 years; the intervertebral height loss rate was 6.84% at 3 months and 9.29% at 2 years (Fig. 7B).
Computed tomography images at different time points: preoperative (A), 1 week postoperative (B), 3 months postoperative (C), 2 years postoperative (D), and 2 years postoperative (three-dimensional reconstruction) (E).
Discussion
The optimal surgical approach for lumbar vertebrae fractures remains a topic of debate. Posterior pedicle screw fixation is currently the most widely used surgical method, owing to its precise fixation and satisfactory outcomes [9–12]. For single-segment thoracolumbar fractures, the TLICS score and load-sharing score suggest that posterior pedicle screw-rod fixation alone is sufficient [13,14]. However, controversy persists regarding the choice between long-segment and short-segment fixation. Long-segment fixation, which involves stabilizing the fractured vertebra along with two adjacent segments above and below offers enhanced stability, facilitates early mobilization, and reduces the incidence of traumatic kyphosis and late internal fixation failure [15–17]. However, this method requires fixation of at least five segments, which may lead to loss of mobility in the thoracolumbar region [2,18]. In contrast, short-segment fixation involves securing the fractured vertebra and only one adjacent segment above and below it. Theoretically, this approach offers several advantages, including reduced operative time and treatment costs, while mitigating the mobility-related drawbacks associated with long-segment fixation, effectively preserving motion segments [2,19]. However, some studies have raised concerns that short-segment fixation may lead to inadequate reduction, postoperative kyphosis, and internal fixation failure [2,20].
This study retrospectively compared the clinical effectiveness of posterior long-segment and short-segment pedicle screw fixation in treating lumbar fractures. The investigation focused on changes in postoperative degeneration indicators such as bone spur formation, vacuum sign, and intervertebral height loss in the fixed spinal region—data that is rarely reported in existing literature.
Our study demonstrated that both long-segment and short-segment fixation approaches were effective in treating single-segment burst fractures of the lumbar spine, with favorable long-term outcomes observed over a 24-month follow-up period. There were no significant differences between the two groups in terms of pain relief, functional improvement, and neurological function.
The requirement for greater exposure in long-segment fixation surgeries inevitably results in increased surgical trauma. Our analysis of perioperative metrics revealed that the long-segment fixation group experienced longer operation times, greater intraoperative blood loss and postoperative drainage volume, and longer hospital stays.
The primary focus of our study was on the postoperative degeneration within the spinal fixation area. A comparative analysis of imaging indicators at 24 months post-operation revealed that the short-segment fixation group exhibited a higher score for bone spur formation compared to the long-segment fixation group. Additionally, no significant differences were observed between the two groups regarding the incidence of vacuum sign or intervertebral height loss.
The higher score for osteophyte formation in the short-segment fixation group may be attributed to slightly inferior postoperative stability compared to the long-segment group [21]. Reduced stability can create local micro-movements, which increases stress stimulation to the fracture site. This, in turn, prolongs the inflammatory phase, enhances local blood flow, and promotes cellular and capillary proliferation. As a result, a more pronounced periosteal callus formation occurs, filling the fracture gap with cartilaginous tissue that eventually undergoes ossification. This process significantly promotes callus growth and fracture healing [22–24], potentially explaining the increased osteophyte formation seen with short-segment fixation. Moreover, the complete bridging of adjacent vertebrae by bridge-like bone spurs can substantially enhance the stability of the fixation area, ensuring long-term efficacy.
The vacuum sign, first described by Magnusson [25] in 1937, is a radiographic manifestation of intervertebral disc degeneration. Degenerative changes in the intervertebral disc primarily manifest as annular fissures, nucleus pulposus dehydration, reduced endplate absorption, and gradually developing negative pressure areas [26–28]. Gases from the extracellular space enter through these fissures, resulting in the “vacuum phenomenon” after the development of negative pressure; instability in the spine leads to abnormal oscillation of degenerative intervertebral discs, generating negative suction that collects gas [27,29,30]. Theoretically, one would expect the short-segment fixation group to experience greater height loss and a higher incidence of vacuum sign than the long-segment group. However, in the present study, no significant differences were observed for these indicators. This discrepancy may be related to the stabilizing effect of bone spurs in the short-segment group.
Although the study has a reasonable follow-up period, the small sample size and retrospective design limit the generalizability of the findings. Larger prospective studies are required to obtain more robust results. Furthermore, exploring the biomechanical factors underlying osteophyte formation is a key research imperative.
Conclusions
This study indicates that both long-segment and short-segment pedicle screw fixation yield satisfactory clinical outcomes for single-segment burst fractures of the lumbar spine. Notably, while the short-segment fixation group exhibited comparable rates of intervertebral height loss and vacuum sign, it showed higher rates of stable osteophyte formation. This study provides clinical data to inform further optimization of surgical strategies for LBFs.
Key Points
Long-segment and short-segment pedicle screw fixation both yield satisfactory clinical outcomes for single-segment lumbar burst fractures.
Short-segment fixation shows comparable rates of vertebral height loss and vacuum sign incidence to long-segment fixation.
Short-segment fixation demonstrates higher rates of stable osteophyte formation.
Notes
Conflict of Interest
No potential conflict of interest relevant to this article was reported.
Funding
The authors received financial support for publication of this article from Hunan Provincial Natural Science Foundation (project no., 2024JJ9277) and Hunan Provincial Department of Education Project (project no., 202B0065)
Author Contributions
Conceptualization: HC, BL. Methodology: HC, BL. Investigation: HC, WP. Data curation: HC. Formal analysis: HC, BL, XL. Writing–original draft: HC, BL; visualization: HC, BL. Writing–review & editing: HC, BL, XL, WP. Project administration: HC, BL. Supervision: XL, BL. Validation: HC, BL, XL. Resources: BL. Final approval of the manuscript: all authors.