Summary
We present a methodology for using an ultrasonic osteotome combined with a conventional osteotome for laminectomy in thoracic ossification of the ligamentum flavum. This is a relatively safe and easy-to-learn method that avoids the perioperative complications associated with the conventional method.
Abstract
Thoracic ossification of the ligamentum flavum (TOLF) is a common cause of progressive thoracic myelopathy. TOLF is typically treated with surgical decompression. A variety of surgical techniques, including laminoplasty, laminectomy, and lamina fenestration, are used for the effective treatment of TOLF. However, traditional methods are associated with a substantial risk of perioperative complications, including dural laceration and/or iatrogenic spinal cord injury. Therefore, it is important to develop an efficient and secure surgical technique for TOLF. Herein, we describe a method for laminectomyperformed at the thoracic spine using an ultrasonic osteotome combined with a conventional osteotome. This technique can reduce intraoperative complications. This is a relatively safe and easy-to-learn method that should be recommended for the treatment of TOLF.
Introduction
Thoracic ossification of the ligamentum flavum (TOLF) is one of the major causes of thoracic spinal stenosis and has been established as the primary cause of thoracic myelopathy1,2,3. TOLF is characterized by the replacement of the ligamentum flavum by ectopic new bone formation. The incidence of TOLF is as high as 36% in Japan and 63.9% in China. Most patients show slow progression to symptomatic thoracic canal stenosis or thoracic myelopathy4. Decompression is the only effective treatment for TOLF once it becomes symptomatic since conservative treatment is usually ineffective5.
Laminoplasty, laminectomy, and lamina fenestration are three surgical techniques that have been demonstrated to be effective for TOLF6,7,8. However, the surgical outcomes are not always satisfactory. The conventional methods can result in a high rate of perioperative complications such as dural laceration and/or iatrogenic spinal cord injury9,10. Therefore, it is important to develop a more efficient and secure surgical technique for TOLF.
Here, we describe in detail a method for laminectomy of the thoracic spine using an ultrasonic osteotome combined with a conventional osteotome to resect the lamina (Figure 1). An ultrasonic osteotome is a precision tool that uses ultrasonic oscillations in its blade to selectively cut mineralized tissue, preventing collateral tissue damage11. The technique presented herein is a relatively safe and easy-to-learn method that should be recommended for the treatment of TOLF.
An ultrasonic osteotomy system is designed to cut hard bone structures effectively while preserving soft tissues by converting the electrical input signal into vertically mechanical oscillations at an amplitude of 0-120 µm and a frequency of 39 kHz. The system consists of a power unit, a handpiece, several tips, and a footswitch. An irrigation pump is also integrated into the system, and this delivers saline to the cutting edge to reduce local thermal necrosis.
Presented here is a case of 57 year old male patient who presented with lower limb weakness with unsteady walking for 3 years. The symptoms were more pronounced on the right side. Physical examination revealed that the patient's muscle strength grade12 was 5 (barely detectable weakness) for both the lower limbs. Additionally, numbness of the skin occurred when acupuncture was applied below the left inguinal plane, hypoesthesia was observed when needling the skin in the saddle area, the deep tendon reflexes were slightly increased in both lower limbs, and the Babinski sign13 was positive. X-ray, CT, and MRI showed thoracic ossification of the ligamentum flavum at T10-11. The preoperative data are presented in Figure 2.
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Protocol
Ethical approval was obtained from the Medical Ethics Committee of the authors' hospital. Informed consent was obtained from each patient.
1. Inclusion/exclusion criteria and preoperative preparation
- Include patients with the following preoperative symptoms: unable to walk steadily, numbness of the lower limbs, atrophy of the lower limbs, leg weakness, uncontrolled movement of the lower extremities, or sphincter dysfunction, etc., as well as signs and imaging data consistent with thoracic myelopathy.
- Exclude patients based on the following criteria: the presence of cervical spinal stenosis or lumbar spinal stenosis (confirmed by MRI), thoracic disk herniation or ossification of the posterior longitudinal ligament (confirmed by CT), fracture, or an infection or tumor of the spine.
- Place the patient in a prone position under general anesthesia.
- Conduct neurophysiological monitoring involving somatosensory evoked potentials (SSEPs) and motor-evoked potentials (MEPs) throughout the surgery.
- Identify the TOLF levels with the C-arm before the operation.
2. Incision and approach
- Disinfect the surgical area using povidone-iodine (PVP-I), and drape the area with sterile surgical towels.
- Identify the involved levels of the TOLF preoperatively using the C-arm X-ray machine.
- Make a longitudinal midline incision over the spinous processes using a scalpel, extending from the spinous process above to the spinous process below the level of the TOLF.
NOTE: One segment is about 10 cm long. The incision should extend from the spinous process above to the spinous process below the level of the TOLF. - Expose the posterior bony structure, including the spinous processes, bilateral lamina, and zygapophyseal joints of the involved levels using a unipolar electrotome.
- Determine the pedicle screw entry points (the intersection between the midlines of the facet joint and transverse process). Insert pedicle marker pins to mark the pedicle screw entry points, and use these as a reference for the lateral border of the thoracic spinal cord.
- Define a rectangular decompression zone as the area between the midpoint of the facet joints bilaterally and between the inferior portions of the superior lamina (beneath the caudal edge of the pedicle, which can be located by the pedicle marker pins) and the superior portions of the inferior lamina (above the cranial edge of the pedicle) of the involved TOLF segments (Figure 3).
3. Decompression
- Remove the spinous processes, along with the supraspinous and interspinous ligaments, using a bone rongeur from the cranial to the caudal end of the decompression zone. Usually, maintain a part of the spinous process to help in removing the lamina.
- Irrigate the incision with saline to identify bleeding sites, and block any bleeding sites with sterilized medical styptic gauge on the residual supraspinous.
- Use an ultrasonic osteotome to cut the lamina horizontally on the cranial and the caudal ends of the decompression zone and longitudinally between the midpoint of the facet joints bilaterally. Perform the cutting until the surgeon feels the lamina has been cut through (The cutting can be done multiple times).
- Use a conventional osteotome to lever the lamina upward and turn it from side to side. A cracking sound of the bone indicates that the lamina has been completely cut off (Figure 4).
- After the lamina has been loosened, use one or two towel clamps to clamp the root of the spinous process, and elevate the entire lamina carefully. When there is adhesion between the ossified tissue and the dura mater, use a nerve dissector for disattachment.
- Trim the remaining articular process and the edge of the lamina on both sides with Kerrison rongeurs to ensure full decompression.
4. Internal fixation
- After thorough hemostasis with bipolar electrocoagulation and styptic cream, cover the dural surface with a gelatin sponge, or fluid gelatin, and neurosurgical sponge (e.g., Cottonoid). Then, replace the pedicle marker pins with pedicle screws.
- Connect the screws with titanium rods, and tighten the screw nuts.
- Mince the bone fragments from the vertebral lamina, and implant the fragments bilaterally between the transverse processes. Throughout the operation, achieve hemostasis using bipolar electrocoagulation and styptic cream.
5. Postoperative treatment
- Perform Jackson-Pratt drainage routinely for 24-48 h in patients without dural tears14. Administer dehydration management and neurotrophic medications after the operation.
- Administer intravenous methylprednisolone (40 mg) for 3 days.
- Instruct the patients to perform rehabilitation exercises to help functional recovery.
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Representative Results
Representative case results
On the first postoperative day, the CT scans revealed that the ossification had been fully removed, and the spinal cord had been completely decompressed (Figure 5). The patient could walk steadily. The muscle strength of both lower limbs was 5. The patient was discharged 3 days after the operation.
A total of 71 patients were enrolled in the study. All surgeries were carried out satisfactorily. The mean duration of the surgery was 126 min ± 32 min. The mean blood loss was 98 mL ± 31 mL. The length of hospitalization was 7.1 days ± 1.4 days. The average follow-up was 12.4 months ± 2.1 months (Table 1). No perioperative complications such as vascular injury, spinal cord injury, or pleural effusion formation occurred during surgery in any patient.
Five patients had dural tears during the operation, and four of them had dural ossification. All of these patients did not undergo repair, and no leakage of cerebrospinal fluid from the wound was observed after the operation. These five patients were allowed to stand up and walk after staying in a prone position for 7 days with pressure dressing. No patient complained of postoperative neurologic exacerbation, surgical site infection, delayed healing, or epidural hematoma. During the follow-up, neither cerebrospinal fluid cysts nor incision dehiscence occurred.
Figure 1: The ultrasonic and conventional osteotomes. (A,B) The ultrasonic osteotome and (C) the conventional osteotome. Please click here to view a larger version of this figure.
Figure 2: Preoperative representative case. (A,B) The preoperative AP and lateral X-ray, (C,D) T2-weighted sagittal and cross-sectional MRI, (E) and computed tomography (CT) scans showed the typical radiologic abnormalities of TOLF. Please click here to view a larger version of this figure.
Figure 3: The rectangular decompression zone. The area between the midpoints of the facet joints bilaterally, as well as the inferior portions of the superior lamina and the superior portions of the inferior lamina of the affected TOLF segments, was identified as a rectangular decompression zone (arrow: pedicle marker pin). Please click here to view a larger version of this figure.
Figure 4: Use of the conventional osteotome to lever the lamina upward. After the lamina is cut through, the conventional osteotome is used to lever the lamina upward in and turn it from side to side. Please click here to view a larger version of this figure.
Figure 5: Postoperative representative case. (A,B) The postoperative AP and lateral X-ray and (C,D,E) CT scan showed that the decompression of the TOLF and thoracic spinal cord was adequate. Please click here to view a larger version of this figure.
| The perioperative parameters | |
| Patients | 71 |
| Operation time (min) | 126±32 |
| Blood loss (ml) | 98±31 |
| Follow-up time | 12.4±2.1 |
| Hospital stay (days) | 7.1±1.4 |
Table 1: The perioperative parameters for laminectomy in thoracic ossification of the ligamentum flavum (TOLF).
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Discussion
Laminectomy is the conventional treatment method for thoracic ossified ligamentum flavum. However, the improper use of traditional bone-cutting equipment, such as high-speed drills and revolving burrs, can result in nerve thermal injury, grasping the soft tissue, tearing the dura mater, and mechanical injury15,16,17. An ultrasonic osteotome is a novel bone-cutting tool used for precise osteotomies. This device allows for bone dissection along a narrow cutting blade, which vibrates longitudinally at high frequency. Due to the precise oscillations of the ultrasonic blade, bone structures can be selectively removed without damaging the adjacent neural tissue18. The energy from the cutting edge of the ultrasonic osteotome is transmitted to the solid structure (bone) preferentially. Due to this tool's characteristic of bending, vibrating, and deforming into vibrational micromotions with minimal energy transfer, adjacent soft tissues (the ligamentum flavum, posterior longitudinal ligament, and dura mater) can be spared with this technique11,19,20,21. Many studies have shown that ultrasonic instruments can decrease the risk of damage to the surrounding soft tissues and critical structures such as the nerves and vessels, especially during osteotomy procedures22,23. Thus, due to the abovementioned benefits, ultrasonic osteotomes have been widely and consistently used to facilitate osteotomies in a diverse range of spinal procedures.
We would like to propose some recommendations for the TOLF surgery. Firstly, before decompression, a rectangular decompression zone should be determined. The cranial to the caudal end of the decompression zone should be defined as the inferior portion of the superior lamina and the superior portion of the inferior lamina of the segments involved in the TOLF. The surgeon must ensure that the ligamentum flavum is not attached to the part of the vertebral lamina that has to be resected. In This not only ensures safety but also ensures that all of the ossified ligamentum flavum is involved. Secondly, to avoid cutting the pedicle or injuring the thoracic spinal cord, pedicle marker pins should be placed before resection, which can serve as a reference for the lateral border of the thoracic spinal cord. Thirdly, after the lamina has been cut through, a conventional osteotome is used to lever the lamina upward and turn it from side to side. If a bouncing or cracking sound is heard, this indicates that the lamina has been completely cut off. If obvious resistance is felt when levering the lamina, the cutting process should be repeated, and the lamina should be levered again until the lamina appears loose during manipulation. Fourthly, after loosening the lamina, the root of the spinous process is clamped with two towel clamps, and the entire lamina is carefully lifted. Typically, a nerve dissector is required to dissect the adhesion between the ossified tissue and the dura mater. Occasionally, a scalpel is used to perform precise dissection when the adhesions are inseparable. Finally, after the lamina has been removed, bipolar electrocoagulation and styptic cream are adopted for hemostasis. If additional bleeding occurs, it can be stopped using a surgical hemostatic matrix, which has a relatively good hemostatic effect.
In this study, we have reported our experience of treating 71 patients using an ultrasonic osteotome combined with a conventional osteotome for laminectomy in TOLF. All the surgeries were carried out successfully. On the first postoperative day, the CT scans revealed that the ossification had been totally excised and that spinal cord decompression was adequate. None of the patients experienced perioperative complications during surgery.
Despite all this, the technique still has some limitations. Firstly, if the ultrasonic osteotome is not applied properly, the blade can easily break. Secondly, the learning curve is steep for young spinal surgeons in the treatment of TOLF. Thus, it is recommended that spinal surgeons with experience perform such operations. Nevertheless, we suggest that the results of the present study have clinical significance. Based on the findings of this study, the technique provided here has been shown to be a safe, effective, and viable choice for the treatment of TOLF, particularly the isolated ossification of the ligamentum flavum.
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Disclosures
The authors have nothing to disclose.
Acknowledgments
Funding was provided by the Zhejiang Medical and Health Science and Technology project (project numbers: 2021433841 and 2023564481).
Materials
| Name | Company | Catalog Number | Comments |
| C-arm X-ray machine | GE | 20192060063 | / |
| Cera styptica | Johnson&Johnson (China) Medical Equipment Co., Ltd | W810T | / |
| Conventional osteotome | Suzhou qingniu medical instrument co. | 10012.01 | / |
| Cottonoids | Piaoan Holding Group Co., Ltd | 20182640073 | / |
| Fluid gelatin | Johnson&Johnson (China) Medical Equipment Co., Ltd | 20183142459 | / |
| Gelatin sponge | B.Braun Melsungen AG | 20163642299 | / |
| Jackson–Pratt drainage | Suzhou Weikang Medical Equipment Co., Ltd | 20162140955 | / |
| Kerrison Rongeurs | Jinzhong Medical Instruments Co., Ltd | 2100888 | / |
| Nerve dissector | Jinzhong Medical Instruments Co., Ltd | p23110 | / |
| Pedicle screw | Medtronic | 76446545 | / |
| Towel clamps | KEWEIDUN | 10058468134417 | / |
| Ultrasonic Osteotomy Surgical System | SMTP Technology Co. | FD880A | / |
| Unipolar/bipolar electrotome | Shanghai Hutong Electronics Co., Ltd | 20143251899 | / |
References
- Miura, K., et al. Thoracic myelopathy caused by calcification of the ligamentum flavum. Journal of Rural Medicine. 15 (2), 65-67 (2020).
- Wang, T., Yin, C., Wang, D., Li, S., Chen, X. Surgical technique for decompression of severe thoracic myelopathy due to tuberous ossification of ligamentum flavum. Clinical Spine Surgery. 30 (1), 7-12 (2017).
- Baba, S., et al. Microendoscopic posterior decompression for the treatment of thoracic myelopathy caused by ossification of the ligamentum flavum: A technical report. European Spine Journal. 25 (6), 1912-1919 (2016).
- Ahn, D. K., et al.
- Isaacs, R. E., et al. Minimally invasive microendoscopy-assisted transforaminal lumbar interbody fusion with instrumentation. Journal of Neurosurgery. Spine. 3 (2), 98-105 (2005).
- Li, K. K., Chung, O. M., Chang, Y. P., So, Y. C. Myelopathy caused by ossification of ligamentum flavum. Spine. 27, 308-312 (2002).
- Okada, K., et al. Thoracic myelopathy caused by ossification of the ligamentum flavum. Clinicopathologic study and surgical treatment. Spine. 16 (3), 280-287 (1991).
- Ikuta, K., et al. Decompression procedure using a microendoscopic technique for thoracic myelopathy caused by ossification of the ligamentum flavum. Minimally Invasive Neurosurgery. 54 (5-6), 271-273 (2011).
- Osman, N. S., et al. Outcomes and complications following laminectomy alone for thoracic myelopathy due to ossified ligamentum flavum: A systematic review and meta-analysis. Spine. 43 (14), 842-848 (2018).
- Hou, X., et al. A systematic review of complications in thoracic spine surgery for ossification of ligamentum flavum. Spinal Cord. 56 (4), 301-307 (2018).
- Hu, X., Ohnmeiss, D. D., Lieberman, I. H. Use of an ultrasonic osteotome device in spine surgery: experience from the first 128 patients. European Spine Journal. 22 (12), 2845-2849 (2013).
- Florence, J. M., et al. Intrarater reliability of manual muscle test (Medical Research Council scale) grades in Duchenne's muscular dystrophy. Physical Therapy. 72 (2), 115 (1992).
- Kumar, S. P., Ramasubramanian, D.
- Liu, T., et al. Analysis of the surgical strategy and postoperative clinical effect of thoracic ossification of ligament flavum with dural ossification. Frontiers in Surgery. 9, 1036253 (2022).
- Li, X., et al. Surgical results and prognostic factors following percutaneous full endoscopic posterior decompression for thoracic myelopathy caused by ossification of the ligamentum flavum. Scientific Reports. 10, 1305 (2020).
- Hosono, N., et al. Potential risk of thermal damage to cervical nerve roots by a high-speed drill. The Journal of Bone and Joint Surgery. British Volume. 91 (11), 1541-1544 (2009).
- Hara, M., Takayasu, M., Takagi, T., Yoshida, J. En bloc laminoplasty performed with threadwire saw. Neurosurgery. 48 (1), 235-239 (2001).
- Vercellotti, T. Technological characteristics and clinical indications of piezoelectric bone surgery. Minerva Stomatologica. 53 (5), 207-214 (2004).
- Nickele, C., Hanna, A., Baskaya, M. K. Osteotomy for laminoplasty without soft tissue penetration, performed using a harmonic bone scalpel: Instrumentation and technique. Journal of Neurological Surgery. Part A, Central European Neurosurgery. 74 (3), 183-186 (2013).
- Sanborn, M. R., et al. Safety and efficacy of a novel ultrasonic osteotome device in an ovine model. Journal of Clinical Neuroscience. 18 (11), 1528-1533 (2011).
- Schaeren, S., et al. Assessment of nerve damage using a novel ultrasonic device for bone cutting. Journal of Oral and Maxillofacial Surgery. 66 (3), 593-596 (2008).
- Stübinger, S., Kuttenberger, J., Filippi, A., Sader, R., Zeilhofer, H. F. Intraoral piezosurgery: Preliminary results of a new technique. Journal of Oral and Maxillofacial Surgery. 63 (9), 1283-1287 (2005).
- Vercellotti, T., Pollack, A. S. A new bone surgery device: Sinus grafting and periodontal surgery. Compendium of Continuing Education in Dentistry. 27 (5), 319-325 (2006).
