24 December 2024: Clinical Research
Long-Term Outcomes of Nano-Hydroxyapatite/Polyamide 66 Strut in Thoracolumbar Burst Fractures
Weiyang Zhong12AE*, Yang Hu3BCDDOI: 10.12659/MSM.946091
Med Sci Monit 2024; 30:e946091
Abstract
BACKGROUND: High-energy injuries, like car accidents, can cause thoracolumbar burst fractures, leading to spinal instability and cord compression. Anterior decompression with stabilization provides strong support, kyphosis correction, and bone fusion. This study evaluated long-term outcomes of using a nano-hydroxyapatite/polyamide 66 strut in 38 thoracolumbar fracture cases.
MATERIAL AND METHODS: Between December 2005 and December 2006, 38 patients underwent the introduced surgery of anterior-oblique approach, decompression, and interbody fusion, using n-HA/PA66 struts. The patients were followed up (FU) for at least 5 years. The neurological function was assessed by American Spinal Injury Association (ASIA) grades, the pain was evaluated by Visual Analogue Scale (VAS) score, the life quality was assessed by Oswestry Disability Index (ODI), and the radiographic results were assessed by X-ray and 3-dimensional computed tomography.
RESULTS: Twenty patients reached the final FU with a mean of 12.50±1.19 years. The mean surgical bleeding, surgical time, and hospitalization time were 633.50±169.0 mL, 183.30±25.41 min, and 18.35±3.05 days, respectively. VAS and ODI of preoperation had a significant difference between 1-year FU and final FU (P<0.05). At the final FU, the patients of ASIA B, C, and D recovered to E. All patients fused with a mean of 4.10±1.21months. Cobb angle and percentage of vertebral body height loss of preoperation had a significant difference between before surgery, at 1-year FU, and at final FU (P<0.05).
CONCLUSIONS: Long-term results of clinical and radiographic assessment of the n-HA/PA66 strut in treating thoracolumbar burst fractures could achieve satisfactory solid anterior support, effective restoration of intervertebral height, and good maintenance of thoracolumbar alignment.
Keywords: Spine, Lumbar Vertebrae, Fractures, Comminuted
Introduction
Anterior spinal column of the thoracolumbar spine can be damaged because of burst fractures caused by high-energy injury such as car accidents and falls from a height, which can lead to spine cord compression and spine instability [1–6]. To reconstruct the anterior column, many methods have been developed, including anterior decompression with stabilization, which can provide strong anterior biomechanical support, significant correction of kyphosis, good stability, and a sufficient contact surface to achieve good bone fusion. Furthermore. The anterior approach can achieve adequate decompression under direct vision without interfering with the spinal canal, reducing the rate of spinal cord injury [7–11]. From 2005, our team has used the nano-hydroxyapatite/polyamide 66(n-HA/PA66) strut in reconstruction of lumbar anterior interbody fusion [12]. However, there have been few long-term clinical results on this strut using reconstruction of the thoracolumbar spine. Therefore, this study aimed to evaluate the long-term outcomes from a lumbar anterior-oblique approach and interbody fusion using the n-HA/PA66 cage in 38 patients with thoracolumbar burst fractures.
Material and Methods
ETHICS APPROVAL AND CONSENT TO PARTICIPATE:
The study was approved by the Institutional Review Board of our hospital and was conducted according to the principles listed in the Declaration of Helsinki. All patients provided written informed consent and their data were stored in our hospital database and used for study purposes.
STUDY DESIGN:
We assessed 38 patients with thoracolumbar burst fractures between December 2005 and December 2006, who underwent anteriolateral approach, decompression, and interbody fusion using the n-HA/PA66 strut. All the patients were checked by plain X-ray and computed tomography (CT) scans, and the surgeries were performed by the same team. The inclusion criteria were as follows: one-segment burst fracture of the thoracolumbar spine from T10 to L2(Magerl type A3), fractures without osteoporosis (T score >−1.0), no lesion of the posterior ligamentous complex, fractures confirmed by CT and magnetic resonance imaging (MRI) and a minimum follow-up (FU) of 5 years. The exclusion criteria were metastatic fractures, primary tumors, or osteoporosis vertebral compression fractures.
The Institute of Materials Science and Technology, Sichuan University and our team designed and improved the n-HA/PA66 strut (Figure 1), and the second-generation n-HA/PA66 strut was used in all patients in our study. The n-HA/PA66 is a biomimetic composite synthesized from nano-scale HA and the polar polymer PA66 and it was approved for clinical application in 2005 by the State Drug and Food Administration of China. The n-HA/PA66 strut is produced by Sichuan Guona Technology Co. LTD.
SURGICAL TECHNIQUES:
All patients were operated on using a left extrapleural-retroperitoneal approach in the lateral position after general anesthesia. The fractured vertebral body and the adjacent vertebral body were fully exposed. The blood vessels of vertebral segments were separated and ligated, and the upper and lower intervertebral discs were removed before decompression. The posterior 3/4 body of the injured vertebra and the fractured bone in the spinal canal were removed to achieve sufficient decompression. The ventral column was reconstructed using an n-HA/PA66 strut with the autogenous bone and the use of screws and rods for stability. The screws were locked with appropriate pressure. Drainage was placed routinely. With the help of analgesia and rehabilitation program, all patients began rehabilitation training with the support of a thoracolumbosacral brace for 6–8 weeks.
POSTOPERATIVE FOLLOW-UP AND EFFICACY EVALUATION:
Radiographic assessments included X-ray and 3-D CT (when necessary, usually at final FU), which were performed immediately, 1 year after surgery, and then annually thereafter. We used the 5-point grading system proposed by Brantigan et al based on X-rays or 3-D CT scans for assessing the bony fusion, in which grades 4 and 5 are defined as bony fusion. American Spinal Injury Association (ASIA) scores were used for evaluating neurological injury, and the visual analogue scale (VAS) and Oswestry Disability Index (ODI) were used for assessing the quality of life. Vertebral body height loss was defined as the ratio of the anterior height of the fractured vertebra to normal anterior height of the adjacent vertebra (=a/(b+c/2) (Figure 2A). Using the Cobb method, it was measured from the superior end plate of the superior vertebral body to the inferior end plate of the inferior vertebral body (Figure 2B).
STATISTICAL ANALYSIS:
Statistical Analysis System software (SAS Institute, Inc., Cary, NC, USA) was used for analyzing the data. Quantitative variables are expressed as the mean±SD. The chi-squared test was used for categorical variables.
Results
Of 38 patients, 20 reached the final FU, 5 died, and 13 were lost to follow-up. The patients were followed up for a mean of 12.50±1.19 years. Their mean age was 38.75±13.79 years. The mean amount of surgical bleeding, surgical time, and hospitalization time were 633.50±169.0 mL, 183.30±25.41 min, and 18.35±3.05 days, respectively (Table 1). The level of surgery was T10 in 3 cases, T11 in 4 cases, T12 in 9 cases, L1 in 2 cases, and L2 in 2 cases. The cause of injury was car accidents in 10 cases, fall injury in 5 cases, and heavy injury in 5 cases. The distribution of ASIA was A in 2 cases, B in 8 cases, C in 6 cases, D in 4 cases, and E in 18 cases before the surgery. None of the patients received blood transfusions after the operation.
Preoperative VAS and ODI showed a significant difference between before surgery at 1-year FU, and final FU (
All patients achieved complete fusion by a mean time of 4.10±1.21 months. There were no findings of non-union, pseudarthrosis, or implant failure at the final FU. Preoperative Cobb angle and percentage of vertebral body height loss showed significant differences among before surgery, 1-year FU, and final FU (
Discussion
To treat A3 thoracolumbar fractures, the approaches and stabilization (anteriorly, posteriorly, or combining the 2 approaches) are still controversial. Many studies have considered that direct decompression of the middle column could be performed through the posterior approach, and the surgical indication may be enlarged [1–5]. However, the neurological decompression involves more trauma through the posterior approach when treating fractures associated with neurological dysfunction, and it not only destroys the intact structure of the posterior column, but also increases the risk of nerve injury during reconstruction of the anterior-middle column. In many cases with thoracolumbar burst fractures, the anterior approaches could provide optimal direct exposure to the ventral dura during the decompression, and the fixation can directly reconstruct the load-bearing column and the fusion column [6–9]. Although the surgical technique is more surgically challenging and has more potential complications, it can provide a better chance of improvement for patients with neurological deficits than with other procedures. In our cases series, none of the patients had serious postoperative complications, but superficial incision infection occurred in a few patients and then healed later. The anterior approach was associated with fewer complications than the posterior approach [10,11].
After decompression, the structural bone grafts play the key role in restoring stability. Many interbody bone grafts could be applied, such as autogenous bone graft (iliac crest or fibula graft), which can achieve good bony fusion, with a few complications such as pain, hematoma, and unhealed incisions. Allografts can avoid donor site complications related with decreased arthrodesis rates but increase of graft subsidence rates [12–15]. Many studies have confirmed that bioinert materials implants, such as titanium mesh cages (TMCs) or polyetheretherketone (PEEK), showed good potential as implants for reliable spinal reconstruction, providing good bone fusion, adequate sagittal preservation, and a lower incidence of implant-related complications. However, TMCs still have problems of metal stress shielding and subsidence, a PEEK and TMCs sometimes have the problem of lack of osseointegration [12–16]. Compared with these bioinert struts, the n-HA/PA66 strut has been used as a bioactive material, which could promote new bone formation and provide an osteogenic scaffold. In previous animal and clinical studies, n-HA/PA66 struts showed good osteoconductivity and osseointegration in the cervical spine of goats and the radius of rabbits, and good results were obtained in cervical spine reconstruction in long-term follow-up. Due to the good bioactivity of the bone column, our team used the n-HA/PA66 struts in construction of A3 thoracolumbar fractures [4–6,17–24].
In long-term FU, our study observed satisfactory improvement in the VAS score and ODI at the final FU. Poor preoperative neurological status before surgery had improved significantly at the final FU. In the present study, the Cobb angle was 29.70±5.56 preoperatively and improved to 11.85±1.63 at the 1-year FU and 12.7±1.59 at the final FU. The fraction of the height loss was 46.40±7.92 preoperatively and improved to 10.25±2.83 at1-year FU and 10.10±3.14 at the final FU. Therefore, the good clinical outcomes in our study could be attributable to the effective improvement and maintenance of thoracolumbar alignment in treating the thoracolumbar spine.
Our study has a few limitations. First, its retrospective nature may have caused bias. Second, 47.35% of the patients lost the contact information because of the imperfect early registration system of patients and the inconvenient communication system, and this may have influenced the results. Third, during the same period, our team did not apply other interbody implants, and there may have been bias due to lack of a control group and there may be related with bias. Fourth, at present, many surgeons prefer the posterior approach in treating thoracolumbar fractures, but our study did not compare the 2 approaches, which may be associated with bias. Prospective, randomized FU studies are needed to compare the n-HA/PA66 strut with other graft implants in treating A3 thoracolumbar fractures.
Conclusions
Long-term clinical and radiographic assessments of treatment of thoracolumbar burst fractures using the n-HA/PA66 strut show satisfactory solid anterior support, effective restoration of intervertebral height, and good maintenance of thoracolumbar alignment.
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