Ultrasonic Osteotome in Posterior Endoscopic Cervical Discectomy for Cervical Radiculopathy

Summary

Here, we present a protocol to describe the technical key points of applying the ultrasonic osteotome in posterior endoscopic cervical discectomy.

Abstract

The ultrasonic osteotome, as a novel osteotomy system, demonstrates unique advantages in posterior endoscopic cervical discectomy (PECD), though its technical implementation remains challenging. Accumulated evidence has validated the safety profile of this device in spinal surgery. Meta-analysis has revealed its superior efficacy in enhancing decompression efficiency, reducing intraoperative blood loss, and shortening operative duration compared to conventional high-speed burrs. Notably, no significant differences were observed in symptom improvement rates, hospital stay duration, or postoperative complication incidence between the two techniques. This study provides a video-documented technical protocol for ultrasonic osteotome utilization in PECD, demonstrating successful clinical implementation in a patient with cervical radiculopathy. We enrolled a 62-year-old female patient who presented with a 10-year history of left-sided cervical and upper back pain. She was admitted for surgery following a recent exacerbation that was accompanied by numbness and pain in her left upper limb. The duration of the surgical procedure was 109 minutes. The patient was mobilized with the help of a standard cervical brace on postoperative day 1. The patient demonstrated significant resolution of left-sided neck pain (preoperative visual analog scale [VAS] score 6, decreasing to 1) and left upper limb radiculopathy. Postoperative magnetic resonance imaging (MRI) confirmed adequate nerve root decompression, with significant symptom resolution and absence of device-related complications such as dural tears or neurological deficits. These findings substantiate the technical feasibility and procedural reliability of the ultrasonic osteotome in endoscopic cervical spine surgery.

Introduction

Cervical radiculopathy, a prevalent spinal disorder, affects approximately 3.3 cases per 1,000 individuals in the general population¹. Anterior cervical discectomy and fusion (ACDF) has long been recognized as one of the standard surgical treatments for cervical radiculopathy². However, hardware-related complications following ACDF, including hardware failure, pseudarthrosis, adjacent segment degeneration, and graft subsidence, present significant management challenges^3,4,5,6,7,8. In recent years, percutaneous endoscopic spine surgery has rapidly advanced due to its minimally invasive nature, rapid recovery, and favorable outcomes^9,10,11,12. Percutaneous posterior endoscopic technique may serve as a potential alternative to ACDF in the management of cervical radiculopathy, with recent studies showing comparable therapeutic outcomes that warrant further clinical investigation^{9,13,14,15,16}.

The anatomical location of cervical disc herniation is closely associated with surgical difficulty^17,18. Based on the anatomical position of the herniated material, it can be classified into three subtypes (Figure 1): Type A, Type B, and Type C. Among these, Type C (where the herniation is completely located within the intervertebral foramen) presents greater challenges for surgical decompression, with higher risks of nerve root injury and vertebral artery laceration. Compared to ACDF, posterior endoscopic cervical discectomy (PECD) offers superior decompression of the stenotic nerve root canal^17,19,20. This is particularly evident in cases where foraminal stenosis is caused by osseous compression, such as hypertrophy of the Luschka joint, osteophyte formation, or calcified intervertebral discs²¹.

The key to the PECD technique lies in achieving adequate decompression of the compressed structures while avoiding injury to critical anatomical elements such as nerve roots and vertebral arteries during the decompression process. However, when using standard surgical instruments (high-speed burr) for bone removal, capillary bleeding often obscures the endoscopic visual field in the irrigation fluid^22,23. This phenomenon not only increases surgical risks but also prolongs operative time due to the necessity of additional hemostatic procedures^24,25. The ultrasonic osteotome, as an alternative osteotomy instrument, has been recognized as an efficient and safe option and is being increasingly adopted in various spinal surgical procedures^24,25,26.

The ultrasonic osteotome generates high-frequency ultrasonic vibrations to cut bone tissue through micro-oscillations^27,28. Consequently, compared to the layer-by-layer grinding of high-speed burs, the osteotomy mode of the ultrasonic osteotome demonstrates higher efficiency when cutting large bone segments²⁵. Due to the distinct physical properties (e.g., elasticity, hardness) of soft and bone tissues, the ultrasonic osteotome exerts a relatively weaker effect on soft tissues^24,25. Thus, for specific procedural steps, the ultrasonic osteotome offers superior safety over high-speed burs. Furthermore, the ultrasonic bone scalpel offers an added advantage over the high-speed burr. During the bone removal process, the cavitation effect induced by the ultrasonic vibrations promotes the coagulation and denaturation of hemoglobin within the cutting area, thereby achieving hemostasis^23,28,29,30. Currently, research on the application of the ultrasonic bone scalpel in PECD is extremely limited. Therefore, this study aims to establish a systematic operational scheme for this technique.

Protocol

The protocol follows the guidelines of the ethics committee of the local hospital. The ethics committee approved the protocol. The patient provided written informed consent.

NOTE: A 62-year-old female patient was included in the study, admitted for treatment due to a 10-year history of left-sided cervical and back pain, which had worsened over the past 10 days and was accompanied by numbness and pain in the left upper limb. Physical examination findings were as follows: (1) restricted left lateral flexion and extension of the cervical spine; (2) positive left brachial plexus stretch test and Spurling's test; (3) muscle strength of the left triceps graded as 4/5; (4) numbness and pain in the left upper limb, primarily radiating to the middle finger of the left hand; and (5) a visual analog scale (VAS) score of 6. The MRI imaging indicates compression of the left C7 nerve root (Figure 2A) and stenosis of the left C7 intervertebral foramen (Figure 2B). The patient had previously undergone conservative outpatient treatment for 3 months with recurrent symptoms and opted for surgical intervention. The surgical instruments and equipment used in the study are listed in the materials table.

1. Pre-endoscopic decompression procedures

1. Body position
   1. Position the patient prone on the operating table with both upper limbs extended forward. This positioning ensures that the cervical nerve roots remain in a relaxed state³¹.
2. Puncture localization and anesthesia
   1. Project the percutaneous puncture point onto the outer lower edge of the left side of cervical 7, targeting the lateral edge of the cervical 6/7 interlaminar window, which is known as the V point, formed by the inferior edge of the C6 lamina, the superior edge of the C7 lamina, and the adjacent facet joint, as visualized under the X-ray image.
   2. Routinely disinfect the surgical area, drape sterile towels, and inject 10 mL of 0.5% lidocaine into the puncture site.
3. Puncture and cannulation
   1. Under real-time X-ray imaging, insert an 18 G percutaneous puncture needle along the planned trajectory, advancing from the skin entry point to the target V point (Figure 3A).
   2. Confirm the position of the puncture needle under X-ray fluoroscopy and make a 1.2 cm incision through the skin and deep fascia at the percutaneous puncture site using a surgical scalpel.
   3. Gradually insert different sizes of dilators along the puncture needle until the working cannula (outer diameter 1.2 cm, inner diameter 1 cm) smoothly enters (Figure 3B). Ensure that the bevel tip of the working cannula contacts the cervical lamina bone surface before commencing the operation under the endoscope.

2. Ultrasonic osteotome osteotomy

1. Resection of the Lamina and Facet Joint near the V-point (V-point plasty)
   1. Use tissue forceps to strip residual soft tissue from the bone surface to identify the lamina and lateral mass. Expose the V-point (Figure 4A).
   2. Set the ultrasonic osteotome to 40 kHz and 150 W.
   3. Centered on the V-point, use the ultrasonic osteotome to progressively resect a portion of the superior lamina, inferior lamina, and part of the facet joint (Figure 4B).
      NOTE: Compared to using a high-speed burr for layer-by-layer bone removal, the ultrasonic osteotome is more efficient and safer for resecting bone around the nerve root.
   4. Continue resecting the lamina and facet joint to enlarge the interlaminar window. During this procedure, the spinal canal will be opened.
2. Exposure of the axillary region of the nerve root
   1. Gently clean the ligament and epidural tissue within the field using tissue forceps (Figure 4C). Then, assess the anatomical structures within the spinal canal beneath the interlaminar window.
   2. Adjust the bone resection direction to expose the axillary region of the nerve root (Figure 4D).
3. Expansion of the nerve root canal
   1. Use the ultrasonic osteotome to resect a small portion of the medial pedicle inferior to the C7 nerve root to expand the surgical working space in the axillary region (Figure 4E).
      NOTE: Resect only a small portion of the medial pedicle to avoid damaging the vertebral artery located laterally.
   2. Remove the ventral calcified protrusion of the nerve root to achieve ventral decompression of the nerve root (Figure 4F).
   3. Resect the dorsal spur of the nerve root to achieve dorsal decompression (Figure 4G).
      NOTE: Since the vibration direction of the ultrasonic osteotome is aligned with its long axis during operation, prolonged direct contact between the side of the osteotome and the nerve root must be avoided during bone resection, as this may result in thermal injury to the nerve.
   4. Confirm successful decompression of the compressed nerve root, ensuring adequate mobility of the C7 nerve root (Figure 4H).

3. Postoperative management

1. Instruct the patient to wear a neck brace when ambulating, starting 2-3 h postoperatively, unless special circumstances indicate otherwise.
2. Administer Flurbiprofen Axetil 50 mg intravenously once daily for postoperative analgesia, continuing for 2 days.
3. Restrict neck activity postoperatively, with the patient wearing the neck brace for 1 week.

Results

The left C7 nerve root of the patient was successfully and adequately decompressed. Under endoscopic visualization, the ventral herniation compressing the nerve root was effectively removed, and partial laminectomy, facetectomy, and spur removal were achieved on the dorsal aspect of the nerve root. Ultimately, it was confirmed that the compressed nerve root had achieved sufficient space for movement. Postoperative MRI imaging demonstrated sufficient foraminal decompression at the left C7 level, in contrast to the preoper...

Discussion

Compared with ACDF, PECD achieves more effective decompression in stenotic nerve root canals, making it a viable minimally invasive alternative^17,20,32,33. The ultrasonic osteotome, as a novel osteotomy power system, serves as a reliable tool for bone removal during PECD^17,23,24. Numerous studies have ...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.5% lidocaine	Beijing Tide Pharmaceutical Co., Ltd	H37022768	Local Anesthesia
Dilatation cannula	Beijing Tianqi Medical technology Co., Ltd., Beijing	ZJ289019	Cannulation
Flurbiprofen axetil	Shandong Hualu Pharmaceutical Co., Ltd.	H20041508	For postoperative pain
Irrigation sleeves	Beijing Sumai Medical Technology Co., Ltd	OS1SPT19	Restricted operating range of the ultrasonic osteotome
Joimax Endoscopy System	Joimax	FS7347171O	TESSYS
Puncture needle	Beijing Tianqi Medical technology Co., Ltd., Beijing	ZJ289033	Puncture
Ultrasonic osteotome	Beijing Sumai Medical Technology Co., Ltd	OT1SPT19	Bone Cutting