Summary
The technique described in this article is well-suited to the Mini-ALIF procedure, allows for excellent exposure and decompression, and facilitates microscope-assisted manipulation.
Abstract
This study aims to investigate the technical aspects of microscope-assisted anterior decompression fusion and to introduce a spreader system suitable for minimally invasive anterior lumbar interbody fusion (Mini-ALIF). This article is a technical description of anterior lumbar spine surgery under a microscope. We retrospectively collected information on patients who underwent microscope-assisted Mini-ALIF surgery at our hospital between July 2020 and August 2022. A repeated-measures ANOVA was used to compare imaging indicators between periods. Forty-two patients were included in the study. The mean volume of intraoperative bleeding was 180 mL, and the mean operative time was 143 min. The mean follow-up time was 18 months. Apart from one case of peritoneal rupture, no other serious complications occurred. The postoperative foramen and disc height were both higher on average than before surgery. The spreader-assisted micro-Mini-ALIF is simple and easy to use. It can provide good intraoperative disc exposure, good discrimination of important structures, adequate spreading of the intervertebral space, and the restoration of the necessary intervertebral height, which is very helpful for less experienced surgeons.
Introduction
Anterior lumbar interbody fusion (ALIF), a fusion procedure that takes an abdominal approach to the anterior lumbar spine, was first described by O'Brien in 19831. With the advantages of less bleeding, less muscle and nerve damage, and the ability to restore lumbar lordosis and reduce the impact on adjacent segmental degeneration better than posterior lumbar interbody fusion, ALIF is now widely used to treat lumbar spondylolisthesis, spinal deformities, lumbar spine infections, and degenerative lumbar disc disease2,3. However, the procedure can also lead to complications such as vascular, nerve, and ureteral injuries; early vascular injuries are especially common, occurring in 10.4% of cases4,5,6,7,8,9.
The use of a microscope during the procedure allows for a clearer operative field, resulting in greater safety in terms of reducing tissue damage, as well as smaller surgical incisions8,10. However, minimally invasive anterior lumbar interbody fusion (Mini-ALIF) still requires a high degree of visualization and stability and requires the use of appropriate spreaders. Early framed laparoscopic spreaders, such as the Synframe system's Activ O spreader or the currently used Miaspas-ALIF spreader (Aesculap), are primarily used for conventional open ALIF surgery11, but their poor microscopic stability, complex installation requirements, and high costs have hampered the use of microscopy in anterior lumbar spine surgery.
In this study, we introduce a new spreader system for microscope-assisted Mini-ALIF that involves opening the operative field and accomplishing nerve decompression under a microscope through a block and retractors fixed to the vertebral body. This study aims to investigate the technical aspects of microscope-assisted anterior decompression fusion and to introduce a spreader system suitable for Mini-ALIF. This system can provide good intraoperative disc exposure, good discrimination of important structures, adequate spreading of the intervertebral space, and the restoration of the necessary intervertebral height, which is very helpful for less experienced surgeons.
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Protocol
This study was reviewed and approved by the Hebei Medical University Third Affiliated Hospital ethics committee, and written informed consent was obtained from all the patients. In addition, no images are identifiable to any patients.
1. Preoperative preparation
- Select appropriate cases based on the patient history, including symptoms, signs, history of previous lumbar and abdominal surgery, abdominal examination, and imaging, such as lumbar X-ray, computed tomography (CT), and magnetic resonance imaging (MRI).
- Advise the patients to undergo preoperative CT angiography of the abdominal aorta and CT angiography of the inferior vena cava to rule out vascular malformations, as well as fasting and enemas the day before surgery for gastrointestinal preparation.
2. Surgical procedures
- Figure 1 depicts the surgical procedure for Mini-ALIF. After general anesthesia, place the patient in the supine position with the hands either flat or on the chest to accommodate an intraoperative lateral X-ray.
NOTE: If the abdominal wall and psoas major muscles are too tight, padding under the thighs is added, and the patients are maneuvered into the bladder stone position. - Locate the surgical lumbar segment by abdominal palpation of the iliac crest and the location of the Kirschner needle under X-ray.
- Use a right side incision for the operation of the L5-S1 segment, and use a left approach for the rest of the segments. Use a scalpel to cut the skin and subcutaneous tissue in turn. Make a transverse incision in the lateral rectus abdominis muscle next to the lower abdomen, with a single segment length of ~5 cm. Use oblique or vertical incisions of about 8 cm in double-segment surgery.
- Identify and incise the anterior rectus abdominis sheath with the aid of a microscope (with a working distance of 535 mm). Then, separate the rectus abdominis muscle bluntly to its outer edge, and retract the outer edge of the rectus abdominis toward the midline using a pulling hook to reveal the posterior rectus abdominis sheath.
- Adjust the appropriate distance and magnification from the microscope to the operating area during the operation. Then, separate the anterolateral abdominal wall of the peritoneum with gauze balls under a microscope, and push contralaterally into the retroperitoneal space to reach the anterior aspect of the vertebral space.
- Separate the prevertebral soft tissue bluntly with gauze and vascular forceps. Explore the sacral vascular space microscopically. Use vascular forceps and nerve strippers to separate the iliac arteriovenous vein. Furthermore, ligate the median sacral artery using silk thread depending on its occlusion.
NOTE: Take care to avoid having to use electrocoagulation, which can damage the inferior ventral plexus. - Use the spreader to expose the surgical field in all directions. Fix the pulling hook to the vertebral body using a K-wires positioning tube on either side of the vertical section. Figure 2A shows the pull hook part of the spreader.
- Figure 2B, C shows the second part of the spreader, which is designed as a combination of two draw-off tabs with a puller and a push-rod. Connect the retractor on one side to the straight-grip pull-rod to provide a pulling force on the soft tissue. The other retractor piece has three attachment holes at different depths; have the assistant attach these holes with a T-pusher on the opposite side to assist the surgeon in pushing away the soft tissue.
- Then, use a 3.2 mm diameter positioning tube to secure the spreader to the two adjacent vertebral bodies of the operated segment using K-wires on either side of the retractor.
- Expose the intervertebral space, and incise the disc annulus fibrosus. Remove the diseased disc, and then decompress the spinal canal guided by a microscope.
- Scrape the endplate with an endplate rugine. Select anterior lumbar fusion apparatus of an appropriate size using a trial model. Fill autogenous bone fragments or bone mud and bone particles into the fusion apparatus and implant them into the surgical intervertebral space. Use an appropriate internal fixation according to the bone quality and diagnosis.
3. Post-surgery
- Use 1 g of cefazolin sodium per 6 h to prevent infection for 24 h after the operation, and restrict the patient from eating until intestinal exsufflation.
- After the patient gets out of bed the next day, advise them to gradually undergo rehabilitation training. Instruct the patient to wear a brace to walk and to use the waistline brace continuously for 3 months.
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Representative Results
Patients who received Mini-ALIF for lumbar degenerative disease at Hebei Medical University Third Affiliated Hospital between July 2020 and August 2022 were enrolled retrospectively, and basic information such as age and gender, as well as medical records and imaging information, were recorded. The inclusion criteria were patients receiving Mini-ALIF for lumbar spinal stenosis, discogenic low back pain, and low-grade (I or II) slippage that had failed to respond to strictly conservative treatment for more than 6 months. The exclusion criteria were as follows: 1) a follow-up time of less than 1 year; and 2) incomplete follow-up data.
This study included 42 patients, comprising 18 men and 24 women. The general information regarding enrollment is shown in Table 1. The mean age of the patients was 51.33 years. There were 5 cases of lumbar spondylolisthesis, 9 cases of discogenic back pain, and 28 cases of disc herniation. The number of patients with a history of abdominal surgery was 8. The number of patients who underwent single-segment surgery was 30, and the number who underwent double-segment surgery was 12. Of all these surgeries, 6 were L2-L3, 12 were L3-L4, 19 were L4-L5, and 17 were L5-S1 (a total of 54 segments). The mean surgical bleeding was 180 mL, the mean operative time was 143 min, the mean hospital stay was 7 days, and the mean follow-up period was 18 months. A patient with a history of C-sections had a rupture of the peritoneum during the operation, which was closed with silk sutures. No other severe complications, such as major vascular, nerve, or organ injury, occurred during the perioperative period for any patient.
Table 2 shows the heights of the intervertebral discs and the foramina of the operated segments of the patients before and after surgery. The operation showed a good indirect decompression effect, and the heights of the intervertebral discs and the foramina in each follow-up period were significantly higher than those before the operation (P < 0.05).
Figure 3 shows the changes in the MRI images before and after surgery of a patient with a lumbar disc herniation biased toward the left foramen. A herniated disc at L5-S1 biased toward the left foramen position can be seen in the MRI of the lumbar spine taken 7 days before the surgery (Figure 3A,C), while the disappearance of the herniated disc can be appreciated in the MRI taken 3 days after the surgery (Figure 3B,D).
Figure 1: Photographs of the Mini-ALIF surgery. (A) Preoperative body surface marking.(B) Exposure through the retroperitoneal space. (C) Exposure of the intervertebral space with the aid of the retractor system. Please click here to view a larger version of this figure.
Figure 2: The spreader system. (A) The pulling hook part of the spreader. (B) The components of the retractor with the pushers and pullers. (C) The combination of the retractor with the pushers and pullers. The diameter of the positioning tube is 3.2 mm, and the height of the retractor is 135 mm. Please click here to view a larger version of this figure.
Figure 3: Pre- and postoperative imaging changes in a patient with a lumbar disc herniation biased toward the left foramen. (A,C) MRI of the lumbar spine taken 7 days before the surgery showing a large herniated disc at L5-S1 that was biased toward the left foramen position. (B,D) MRI taken 3 days post-operation showing the disappearance of the herniated disc. Please click here to view a larger version of this figure.
| Characteristics | Value |
| Number of patients | 42 |
| Age, mean (range) | 51.33 (31–70) |
| BMI (mean) | 26.4 |
| Sex, male/female | 18/24 |
| History of abdominal surgery | 8 |
| Surgical bleeding, mean (mL) | 180 |
| Operative time, mean (min) | 143 |
| Hospital stay (day) | 7 |
| Diagnosis | Number of patients |
| Lumbar spondylolisthesis | 5 |
| Intervertebral disc herniation | 21 |
| Lumber formainal stenosis | 7 |
| Discogenic low back pain | 9 |
| Surgical segment | Number of segments |
| Single segment | 30 |
| Double segment | 12 |
| L2-3 | 6 |
| L3-4 | 12 |
| L4-5 | 19 |
| L5-S1 | 17 |
Table 1: Summary and surgical outcomes of the patients.
| Group | Preoperative | 3 Days Postoperatively | 3 Months Postoperatively | 12 Months Postoperatively | P |
| Intervertebral height | 7.05 ±0.24a | 10.22 ± 0.14b | 9.99 ± 0.13c | 9.81 ± 0.13d | <0.01# |
| Foraminal height | 17.33 ± 0.22a | 21.13 ± 0.14b | 20.86 ± 0.16c | 20.69 ± 0.13d | <0.01# |
Table 2: Imaging outcomes. #, repeated-measures ANOVA; at least one identical subscript letter denotes no significant difference from each other.
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Discussion
Several turns surrounding the peritoneum during Mini-ALIF surgical exposure and decompression of the spinal canal are critical steps in the surgery. Injury to the anterior peritoneum when opening the anterior rectus abdominis sheath and separating the transverse abdominal fascia can easily lead to failure with this approach5. In addition, patients with lumbar spine infections and a history of abdominal surgery can develop intraoperative complications such as adhesions of the peritoneum and soft tissues, which are difficult to separate with blunt dissection and can easily cause iliac vein tears12. Past the retroflexion of the peritoneum, the surface and inner edge of the psoas major muscle are traversed by the ureter, genitofemoral nerve, common iliac artery, rectum, and other important tissues. The incidence of venous injury in anterior lumbar surgery, which often occurs in the iliac vein system, has been reported to be 0%-18%, and tearing of the iliac vein due to traction has been reported to be the most common venous complication13,14,15,16. However, abdominal arterial injury is more dangerous than venous injury and can be fatal17,18. When stretching the vascular space to reach the anterior vertebrae, the hypertrophied anterior vertebral fascia in front of the lumbar vertebrae, and the anterior longitudinal ligament with the autonomic nerve, injury to the inferior ventral plexus may occur, which, in turn, can cause postoperative retrograde ejaculation with an incidence anywhere between 0.42% and 27.3%19,20,21.
The use of microscopy allows for easier handling of the retroperitoneal vessels (common iliac vein, segmental vessels, lumbar ascending veins), as well as the prevertebral soft tissues, thus minimizing the risk of tissue damage22. In patients with foraminal stenosis for whom previous indirect decompression alone has not achieved good results, a microscope helps to visualize the stenotic space with enhanced visualization and also provides a coaxial view to the surgical assistant, who may be required to help with blood aspiration, especially when dealing with the intervertebral space. Shin et al. visualized the complete decompression of the dorsal root ganglion at the intervertebral foraminal stenosis caused by lumbar spondylolisthesis combined with posterior bony stenosis with microscopic assistance and were able to achieve good surgical results23.
In auto-static spreaders such as the Synframe, Condor, and Thompson, the main structure is a fixation bracket fixed to the edge of the operating table that holds the pull-hooks in place and draws the surgical channel in all directions11,13,24,25. However, these types of spreaders are not as stable under a microscope and are complex and expensive to install, which greatly increases the time and cost of the procedure. In the absence of a suitable spreader, the field of view is severely obscured; additionally, an inappropriate spreader can also occupy the already inadequate surgical space when using a microscope.
Compared to the traditional ALIF procedure, the new spreader system uses Kirschner wire (K-wire) to fix the retractor piece and retractor to maintain stable spreading and achieve sufficient soft tissue contraction and intervertebral space expansion to reduce complications26. Although the wide and stable field of view under the microscope saves time in the handling of the spinal canal and reduces the risk of nerve damage as well, it takes time to set up the parameters and make adjustments. The average operation time was 143 min, which was not much different from previous studies, but there was some concern that the use of a microscope might prolong the operation and lead to complications such as thrombosis8,10. With the continuing development of microsurgery technology, 3D microscopes without eyepieces have also entered into use in the clinic, and we believe that in the future, it will be possible to perform Mini-ALIF more easily with the aid of 3D microscopes. Indeed, this would further reduce the duration of surgery and the occurrence of complications27,28. Although the microscope can help to separate the tissue, abnormal anatomy of the abdominal vessels, severe peripheral vascular disease, a solitary kidney on the operative side, and severe spondylolisthesis still limit the operation.
The new spreader system provides a method for microscope-assisted Mini-ALIF that facilitates more precise micromanipulation and reduces the surgery time for delicate procedures. Therefore, the spreader system can provide a stable, wide field that addresses the barriers to the use of microscopic techniques and that provides a clear, direct view of the spinal canal and nerves from the microscope, thus allowing for the complete removal of the free nucleus pulposus from inside the spinal canal. Microscope-assisted Mini-ALIF has good clinical efficacy and safety in the treatment of degenerative lumbar diseases10,23.
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Disclosures
The authors have no conflicts of interest in this research.
Acknowledgments
The authors have no acknowledgments.
Materials
| Name | Company | Catalog Number | Comments |
| Anterior Lumbar Cage Instrument | LDR Medical | ROI-A | |
| Cefazolin Sodium for Injection | Brilliant Pharmaceuticals | Chinese Drug Approval Number H20217016 | |
| Coagulation Forceps | Zhenjiang Hengsheng Juen Medical Instrument Co., Ltd. | BZN-Q-A-S | |
| Coated, Braided Silk | Suzhou Jiasheng Medical Treatment Products Co.,Ltd. | 2-0(4#) | |
| Endplate Rugine | LDR Medical | IGO16R | |
| Microscope | Carl Zeiss AG | S88 | |
| SPSS Statistics for Windows | IBM Corp | version 26.0 | |
| Surgical ablation electrodes | Jiangsu Yibo Leiming Medical Technology Co., Ltd. | LM-A5 |
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