Complications in Full-Endoscopic Posterior Cervical Surgery: A Review of the Literature and Preventive Strategies

Abstract

Study Design

Narrative review

Objectives

Full-endoscopic cervical spinal surgery via a posterior approach has gained popularity for its effectiveness in treating various cervical spine pathologies. However, this technique presents its own set of complications that need to be recognized and addressed. This review aims to comprehensively analyze the complications associated with full-endoscopic posterior cervical spine surgery and provide preventive strategies to minimize these risks and ensure successful surgical outcomes.

Methods

A thorough literature search was conducted using public databases, including PubMed and SCOPUS, from January 2000 to June 2024. The review focused on analyzing complications related to full-endoscopic posterior cervical spine surgery and identifying preventive strategies using the keywords “Complication,” “Endoscopic,” “Full-endoscopic,” “Endoscopy,” “Uniportal,” “Biportal,” “Posterior,” “Cervical,” “Spine,” “Surgery,” “Foraminotomy,” “Decompression,” and “Discectomy”.

Results

The review identified a variety of complications associated with full-endoscopic posterior cervical spine surgery, including neurological, vascular, and structural issues. Despite the minimally invasive benefits of this approach, risks such as nerve root injury, dural tears, and epidural hematomas still exist. The study emphasizes preventive strategies like meticulous preoperative planning, refined surgical techniques, and cautious intraoperative management around neural structures to mitigate these risks.

Conclusions

While full-endoscopic posterior cervical spine surgery provides significant advantages, such as reduced tissue disruption and quicker recovery, it also carries specific complications that must be carefully addressed and managed. Prevention is crucial for ensuring optimal outcomes. By understanding potential risks and implementing effective prevention strategies, surgeons can significantly reduce complications and enhance patient safety.

Introduction

The anterior cervical approach, particularly anterior cervical discectomy and fusion (ACDF) was considered the gold standard for the management of cervical radiculopathy and myelopathy. However, ACDF has notable drawbacks, including the need for fusion and the risk of adjacent segment disease, which has the potential need for future surgical intervention. Additionally, ACDF is associated with surgical complications, such as dysphagia, postoperative hematoma, recurrent laryngeal nerve injury, cerebrospinal fluid (CSF) leakage, implant failure, and pseudoarthrosis.^1-3

Open posterior approaches, such as posterior cervical foraminotomy, laminoplasty, and laminectomy with fusion, are effective in treating various cervical conditions by providing direct access to the pathology and ensuring adequate decompression of neural structures. However, these techniques are less popular due to their limitations. They often involve extensive subperiosteal detachment of the extensor cervical muscles, leading to paraspinal muscle denervation and atrophy. This can result in postoperative complications, including loss of cervical lordosis, extended hospital stays, axial neck pain, and iatrogenic instability.^4-6

As minimally invasive surgery (MIS) techniques in spine surgery have evolved, significant progress has been made since the introduction of microendoscopic posterior cervical foraminotomy (PCF) by Adamson in 2001 ⁷ and full-endoscopic PCF by Ruetten et al in 2007. ⁸ These techniques effectively address many complications associated with traditional open surgeries and offer comparable outcomes to open PCF for treating cervical radiculopathy. They also provide advantages such as minimized tissue trauma, reduced blood loss, decreased analgesic use, shorter surgical times, and shorter hospital stays. ⁹ When compared to the traditional ACDF for treating cervical radiculopathy, both MIS-PCF and endoscopic PCF showed similar postoperative outcomes, with the added benefits mentioned above.^10-12 The full-endoscopic or uniportal endoscopic cervical spinal surgery via a posterior approach has recently gained popularity for its effectiveness in treating cervical radiculopathy and myelopathy while minimizing complications.^13-16 A recent comparative analysis by Kim et al evaluated the clinical outcomes of uniportal endoscopy, biportal endoscopy, and microsurgery for cervical foraminal stenosis. All techniques showed favorable clinical outcomes and sufficient foraminal decompression. The full-endoscopic approach demonstrated the highest inclination angle for undercutting the facet joint and the lowest facet resection rate while preserving the facet and anatomical structures. Theoretically, this reduces the rate of degenerative changes and enhances the clinical outcomes, with patients experiencing significantly less pain and disability than those in a microscopy group. ¹⁷ However, as the number of patients undergoing full-endoscopic cervical surgery increases, the incidence of complications associated with this approach also increases. ¹⁸ Therefore, understanding the underlying causes and implementing preventive measures are crucial to ensuring successful surgical outcomes.

Materials and Methods

A narrative review was conducted using literature from January 2000 to June 2024, sourced from public databases (PubMed and SCOPUS). Keywords used included “Complication,” “Endoscopic,” “Full-endoscopic,” “Endoscopy,” “Uniportal,” “Biportal,” “Posterior,” “Cervical,” “Spine,” “Surgery,” “Foraminotomy,” “Decompression,” and “Discectomy.” Non-English studies were excluded (see Table 1). The review aimed to analyze complications associated with full-endoscopic posterior cervical spine surgery and to explore preventive strategies for each complication. The paper selection process involved all authors, with the senior author (VK) overseeing the final selection process.

Table 1.

Search Strategy Summary.

Items	Specification
Dates of search	Narrative review search timeline: Jun 1-Jun 30, 2023
Databases and other sources searched	PubMed, SCOPUS
Search terms used	“Complication”; “endoscopic”; “full-endoscopic,” “endoscopy,” “uniportal,” “biportal,” “posterior”; “cervical”; “spine”; “surgery”; “foraminotomy”; “decompression”; “discectomy”
Timeframe	Till Jun 2024
Inclusion and exclusion criteria	Relevant literature on posterior endoscopic spinal surgery in English language
Selection process	Conducted by all authors with senior author (VK) overseeing the final selection process

Indications, Advantages, and Disadvantages of Full-Endoscopic Posterior Cervical Spine Surgery

With appropriate patient selection, full-endoscopic posterior cervical spine surgery offers several advantages over traditional anterior and posterior techniques and demonstrates outcomes that are equivalent or slightly superior to those of open cervical foraminotomy.^9,19 These benefits include reduced tissue damage, lower infection risk, faster recovery with less postoperative pain, and shorter hospital stays. The endoscopic system provides high-definition imaging for enhanced visualization and precision, and smaller incisions reduce blood loss and result in fewer noticeable scars. Additionally, the procedure preserves spinal stability by minimizing structural disruption of the posterior element.^1,13,14

Most studies agree that the primary indications for full-endoscopic posterior cervical spine surgery are persistent radicular pain or neurological deficits unresponsive to conservative treatment for at least 6 weeks, resulting from cervical disc herniation or lateral cervical pathology, such as foraminal stenosis due to facet degeneration and osseous-ligamentous hypertrophy, or even conditions, such as infection and tumors.^4,20-23 However, recent literature indicates that previous contraindications, including cervical myelopathy, multi-level ossification of the posterior longitudinal ligament, central disc herniation, and severe canal stenosis, can also be effectively treated with this approach as expanded indications.^15,24-26 However, some contraindications are still widely accepted. These include significant cervical deformity, severe cervical myelopathy, cervical instability (defined as >3 millimeters [mm] of subluxation on flexion and extension radiographs), significant cervical kyphosis exceeding 10°, and predominant axial neck pain without neurological symptoms^1,4,6,20,22

Lastly, surgical expertise should be considered before performing endoscopic cervical spine surgery. One of the main disadvantages of the technique is its steep learning curve, which requires familiarity with the anatomy under endoscopic visualization and longer operative time in the first few cases. ²⁷ Without sufficient experience, several complications, such as inadequate decompression, nerve root injury, hematoma, and infection can occur.^20,28-31 Few studies have addressed the learning curve for posterior endoscopic cervical surgery, with a suggested cut-off between 8 and 28 cases. Interestingly, these studies reported no complications during their respective learning curves, making it challenging to directly link a steep learning curve to an increased risk of complications.^32,33 This finding is different from several studies that focused on endoscopic lumbar surgeries which showed mixed results. While some studies have reported a higher rate of reoperations and surgical failures during the early phases of the learning curve,^34,35 others indicate that after achieving proficiency, typically between 20 to 40 cases, there is no significant difference in surgical outcomes or complication rates between early and late phases.^36,37

Associated Complications as Reported in the Literature and Preventative Measures

A literature review on full-endoscopic cervical spine surgery, encompassing procedures such as foraminotomy, discectomy, and decompression, reveals that surgical techniques differ among authors, which may influence the reported complication rates. Some studies reported no complications, while others noted various issues. However, when comparing the complication rates with the traditional method specifically the ACDF, no statistically significant difference in the incidence of adverse events or recurrence was observed.^38,39 Similarly, when compared to other posterior approaches, such as microendoscopic and unilateral biportal endoscopic cervical surgery, the complication rates were also not significantly different.^9,40 We classified our findings into 4 categories of complications, including neurological, vascular, structural, and other possible complications, and summarized them in Tables 2 and 3.

Table 2.

Complications Reported in the Literature.

Author	Type of Study	Patients Undergoing FPCF	Complications Reported (N = Patients)	Complication Rates (%)
Ruetten et al (2008) 38	Prospective	89	Transient hyperesthesia (3) Recurrence (3)	6.74
Yang et al (2014) 3	Retrospective	42	Neurological deterioration (1) Revision surgery (1)	4.76
Ohmori et al (2017) 23	Retrospective	59	Radicular pain (1) Lamina fracture (1)	3.38
Ye et al (2017) 42	Prospective	9	Transient hyperesthesia (1)	11.11
Komp et al (2018) 22	Prospective	100	Transient hyperesthesia (3) Neck pain (5) Recurrence (3)	11.00
Wu et al (2018) 52	Case report	2	Total spinal anesthesia (2)	-
Lee et al (2018) 48	Retrospective	106	Transient dysesthesia (3) Short-term motor deficit (2) Dural injury (2) C5 nerve palsy (1) Epidural hematoma (1) Recurrence (1)	9.34
Zheng et al (2018) 43	Retrospective	249	Revision surgery (3) Transient hyperesthesia (2) Epidural hematoma (1) Dural injury (1)	2.81
Zhang et al (2018) 45	Retrospective	42	Transient dysesthesia (2)	4.76
Yu et al (2019) 24	Retrospective	32	Arm pain (1)	3.13
Shu et al (2019) 47	Retrospective	32	Short-term motor deficit (1)	3.33
Ji-Jun et al (2020) 30	Prospective	43	Dural injury (2) Transient hyperesthesia (2)	9.30
Shen et al (2020) 13	Retrospective	68	No complication	0
Wu et al (2021) 46	Prospective with retrospective	25	Neurapraxia (2) Recurrence (1)	12.00
Liu et al (2021) 44	Retrospective	87	Transient hyperesthesia (1)	1.15
Ma et al (2022) 66	Retrospective	59	Hematoma (1) Dural injury (1)	5.08
Zhong et al (2022) 78	Retrospective	34	Arm pain (1)	2.94
Dinh et al (2022) 74	Prospective	20	No complication	0
Hou et al (2022) 76	Retrospective	24	Arm pain (1) Numbness (2)	12.5
Wang et al (2022) 41	Retrospective	610	Wound infection (2) Dural injury (6) Upper limb palsy (6)	1.31
Kang et al (2022) 65	Retrospective	32	C5 nerve palsy (1) Dural injury (1) Revision (1)	9.38
Kim et al (2022) 17	Retrospective	38	Transient nerve root palsy (1) Recurrence (1)	5.26
Shi et al (2023) 28	Retrospective	22	Hematoma (1)	4.55
Xifeng et al (2023) 25	Prospective	13	No complication	0
Wang et al (2023) 40	Retrospective	65	Dural injury (2) Upper limb pain (1)	4.62
Chen et al (2023) 12	Retrospective	19	Dysphagia (1) Root injury (3) Adjacent segment pathology (1)	26.32

FPCF, full-endoscopic posterior cervical foraminotomy.

Table 3.

Summary of Reported Complications and Preventative Measures: Categorized by Type and Frequency.

Complications of FPCF	Estimated Rate (%) a	Preventative Measures
Neurological complications
Neurological deficit (eg, upper limb palsy, TSA, transient paresis, and numbness)	1.15	1. Meticulous drilling during bony decompression helps avoid both direct and thermal injury to the neural elements 2. Avoid excessive retraction of neural structures 3. Frequently evaluate dural integrity throughout the procedure 4. Concern about the thermal injury from the RF cauterization and pressure injury from the irrigation system
Transient hyperesthesia/dysesthesia	0.88
Dural injury	0.78
Neck pain	0.21
Arm pain	0.21
Vascular complications
Postoperative epidural hematoma	0.26	1. Reverse trendelenburg position
		2. Adequate bleeding control
		3. Use surgical drainage if needed
Structural and other complications
Recurrence	0.47	1. Accurate diagnosis and appropriate surgical indication 2. Correct level of surgery 3. Prevent iatrogenic instability 4. Adequate decompression
Revision surgery	0.26
Wound infection	0.10
Lamina fracture	0.05
Dysphagia	0.05
Adjacent segment pathology	0.05

FPCF, full-endoscopic posterior cervical foraminotomy; TSA, total spinal anesthesia; RF, radiofrequency.

^aFrom previous literature in this review (total n = 1921).

Neurological Complications

Neurological Injuries

The most reported complications of posterior endoscopic cervical spine surgery are neurological issues, ranging from transient dysesthesia to upper limb palsy. ⁴¹ Ruetten et al described a novel full-endoscopic technique for cervical posterior foraminotomy ⁸ and reported that 3% of the patients had transient dermatomal-related dysesthesia. There were no serious neurological complications, such as profound weakness or spinal cord damage in the study. Transient hyperesthesia has also been reported in other studies. Suspected causes include traction or thermal injury during drilling. The recovery time for this morbidity was between 1 to 6 weeks.^22,30,42-44 Additionally, one study reported relief of symptoms following an intervertebral foramen block using an analgesic drug and steroid. ⁴⁵

Other neurological complications included transient paresis and upper limb palsy, specifically C5 palsy. Transient paresis typically resolved within 3-6 months with conservative measures, with suspected causes, including direct spinal cord injury or cord retraction during surgery.^41,46,47 Regarding C5 palsy, Wang et al indicated that nerve root disturbance, thermal injury during the operation, and exacerbation of pre-existing nerve root damage in severely compressed nerve roots were the contributing factors. Additionally, this study noted that a preoperative foraminal width of <3 mm correlated with a higher incidence of postoperative upper limb palsy. ⁴¹ Excessive nerve root retraction, mechanical injury during drilling, and thermal injury have also been suspected causes of nerve palsy in other studies.^46,48 During posterior foraminotomy and discectomy at the C4-5 level, the approach to the intervertebral disc can be challenging due to the C5 nerve root’s position, which covers the entire disc at a relatively sharp angle. Removing the extruded disc at this level often requires more extensive retraction of the C5 nerve root, which may increase the risk of motor palsy. ⁴⁹ The unique anatomy of the C5 nerve root may also be a contributing factor, in which the distance between its division from the dura mater and foramen exit is shortest at the C5 nerve root, and the C4-5 intervertebral foramen is typically narrow. This narrowing is compounded by the high incidence of the anterior prominence of the cephalad facet joint. ⁵⁰ A study by Bydon et al, ⁵¹ suggested that a posterior cord shift, likely caused by dural expansion following foraminotomy, increases tension and/or causes direct damage to the nerve roots. Wider posterior decompression at C4-5 results in greater fallback of the spinal cord, placing increased tension on the C5 nerve roots, thereby increasing the risk of C5 palsy.^41,51

The other severe complication that occurred following the posterior endoscopic cervical discectomy procedure, which was reported in a case study by Wu et al ⁵² was transient spinal anesthesia. Transient spinal anesthesia is characterized by sudden hypotension, a rapidly increasing motor block, temporal loss of breathing, loss of consciousness, and pupillary dilation. During the operation, one patient became unconscious with unstable vital signs, whereas another reported numbness in both the arms and legs. Both cases were attributed to total intraoperative spinal anesthesia. This may result from leakage of local anesthetics, such as lidocaine, which is used for local infiltration at the entry site, into the intradural space, or even the intracranial area due to perforation of the subarachnoid space around the lamina. Therefore, care should be taken when planning the use of local anesthesia to avoid this rare but devastating complication.

Preventative Measures

As previously mentioned, neurological complications can range from dysesthesia to motor weakness. The primary surgical factors contributing to these complications include excessive nerve root retraction, mechanical injury during drilling, and thermal injury. To prevent neurological injury, the following strategies are suggested:

Bone Works

Bone work during foraminotomy typically begins at the medial joint segments after identifying and visualizing the interlaminar space (the “V” point). Proper handling of the drill at this stage is crucial to avoid unintended injuries. Drilling should be performed intermittently under high magnification, ensuring the tip of the drill always remains visible. The motion should be a sideways, pendulum-like movement rather than a vertical one. The extent of cephalad, caudal, and lateral bone resection should be tailored according to preoperative imaging and pathology. ⁵³

Bone resection should not be completed solely with the drill. Instead, the lamina should be thinned to the ventral cortex, which can then be removed using a small footprint Kerrison rongeur. This technique can help prevent the risk of direct or thermal injury to the neural elements during drilling. It is also important to keep the ligamentum flavum intact during the major bone works step, as it serves as both an anatomical landmark and a protective layer. ⁵⁴

Protecting the Exiting Nerve Root

After resecting the ligamentum flavum, the lateral margin of the dural sac becomes visible, serving as an anatomical guide for locating the exiting cervical nerve root (Figure 1). A beveled working cannula can be used as a protective barrier for the exiting nerve root during disc space exploration or discectomy. The cannula should be directed medially to avoid compressing the thecal sac and should be retracted away from the nerve root without mobilizing it.^1,4,20,22

Figure 1.

Endoscopic illustrations of intraoperative findings after a posterior foraminotomy performed at the left C6-7 level.

Lysis of Adhesions Around Perineural Structures

Before performing a discectomy, significant adhesions often exist between the herniated disc and the exiting nerve root. Surgeons should carefully dissect and remove these adhesions using a small dissector and rongeur.^31,55 Meticulous technique is crucial to avoid nerve root injury and sharp instruments should be avoided during this step. ⁵³

Discectomy and Decompression Procedure

The herniated disc, typically located beneath the nerve root, should be carefully extracted under direct visual guidance. This involves maneuvering the mobile arm of a small rongeur under the exiting nerve root and spinal cord to remove the herniated segment without injuring neural elements (Figure 2). Care should be taken to avoid retraction near the spinal cord, thereby preventing neurological complications. After removing the herniated disc material, nerve root tension should be evaluated using a nerve hook to confirm sufficient decompression, and the freely mobile and pulsatile nerve roots should be clearly visualized.^1,4,20,22 An ultrasonic osteotome can be used instead of a standard endoscopic drill during partial pediculectomy and ventral osteophyte resection for adequate nerve root decompression, to reduce the risk of nerve root and spinal cord injuries in complicated cases. ⁵⁶

Figure 2.

Endoscopic illustrations of intraoperative findings during a discectomy at the left C6-7 level.

Appropriate Bleeding Control

For bleeding control around neural structures, endoscopic radiofrequency (RF) cauterization should be used with precision. The voltage should be reduced to below 90 Watts in these areas. The RF probe must be positioned carefully, with the posterior end directed away from the nerve root or dura to ensure that the RF current discharge is directed away from neural structures, thus preventing thermal injury. ⁵³ Moreover, intermittent RF is preferred over continuous cauterization for better outcomes.

Temporary increases in irrigation pressure to manage bleeding should be limited and used with caution to prevent damage to neural elements. ⁵⁷ The proposed mechanism is that increased irrigation pressure to control bleeding can increase cervical epidural pressure by compressing the dural sac. This shifts the CSF cranially towards the brain, thereby increasing intracranial pressure, which may cause posterior neck pain, and in severe cases, lead to seizures.^58,59 Additionally, if combined with an incidental durotomy, this increased pressure can result in nerve root injury. ⁶⁰

Role of Intraoperative Neurophysiological Monitoring

Intraoperative neurophysiological monitoring (IONM) can reduce the risk of nerve root or spinal cord injuries during surgery. However, clear indications for these techniques in posterior endoscopic cervical spinal surgery have not yet been established.^29,61 Although the IONM may enable intraoperative diagnosis of dorsal root ganglion injury, the interpretation of signals may not correlate well with postoperative clinical outcomes, such as neurological deficit and dysesthesia.^62,63 Additionally, the increased costs of these technologies must be considered. The authors usually use IONM in patients who present with moderate-to-severe myelopathy caused by posterior cervical pathologies, such as ossified ligamentum flavum (OLF) or facet cysts that require wide spinal cord decompression or bilateral decompression.

Incidental Durotomy

Incidental durotomy is a major concern in posterior cervical endoscopy. Previous studies on endoscopic lumbar spinal surgery have reported dural injury rates between 0-8.6%, with the highest rates occurring during synovial cyst resection. ⁶⁴ This study found that the average rate of dural injury during endoscopic cervical spine surgery was 0.79% (Table 2), with reported rates between 0-4.65%.^{30,40,41,43,48,65,66} In all cases of dural tears during endoscopic cervical spine procedures, patients were treated conservatively without requiring dura repair. This may have been due to the small size of the tear, which was approximately 2 mm on average. ⁴³ Additionally, no further complications, such as CSF leakage or meningocele, were observed, and no reoperation was performed because of the durotomy. Despite the low incidence of incidental durotomy, surgeons should use meticulous surgical techniques to avoid this complication.

Preventative Measures

The integrity of the dura should be frequently evaluated throughout the procedure until the endoscopic procedure is completed. When working around the dural sac, meticulous surgical technique is essential to avoid this complication. If an incidental durotomy occurs, the size and characteristics of the dural tear, along with the integrity of the neural elements must be carefully evaluated. Following the strategy proposed by Kim et al regarding endoscopic lumbar spinal decompression, a small dural tear of <1 centimeter (cm) can be managed with an endoscopic patch-blocking dura repair technique using collagen and fibrin patches to seal the defect and prevent adhesions. ⁶⁷ Alternatively, autologous muscle or fat grafts can be used in combination with fibrin glue or fibrin-sealed collagen sponge. ⁶⁴ However, these techniques have not been reported for use in the incidental durotomies after cervical endoscopic spine surgery (ESS).

Vascular Complications

Epidural Hematoma

Epidural hematoma is another postoperative complication that can lead to the compression of neural elements, requiring emergency evacuation.^{28,43,48,66,68} Park et al studied patients who underwent spinal surgeries and reported 1.15% rates of postoperative hematoma. The risk factors included anterior approach, lumbar spine surgery, intraoperative blood loss, prolonged surgical time, high blood pressure, use of non-steroidal anti-inflammatory drugs, and concurrent bleeding tendency. ⁶⁹ In this study, we found that the incidence of postoperative hematoma after posterior cervical ESS was approximately 0.26%. Most cases of postoperative epidural hematoma were benign and unlikely to require further intervention. ⁷⁰ However, Zheng et al reported in their study that one patient presented with a new neurologic deficit due to postoperative epidural hematoma and required emergent reoperation for decompression and evacuation of the hematoma. ⁴³

Preventative Measures Patient Positioning

The surgical table should be tilted in the reverse Trendelenburg position, with the cervical spine parallel to the floor (Figure 3). This position helps reduce epidural venous pressure and minimizes intraoperative bleeding. ²²

Figure 3.

Reverse Trendelenburg position is demonstrated. The head is stabilized in cervical flexion by using the Mayfield skull clamp system.

Bleeding Control

To prevent epidural hematoma formation during decompression, endoscopic bipolar radiofrequency cauterization should be used throughout the procedure to control bleeding from the epidural venous plexus, posterior musculature, and cancellous bone. Surgeons should coagulate any potential bleeding vessels during the procedure. If the bleeding point cannot be identified and it obscures the visualization, the surgeon can try the “touch and press technique” by touching and pressing the tip of the bipolar cautery on the suspected bleeding point. If the suspected point is visually clear after the touch-and-press maneuver, then that area is most likely the bleeding point that needs to be coagulated.

In cases of multiple bleeding points or massive bleeding that is difficult to control, the surgeon might consider pausing the operation and irrigating the operative field with saline for 5 min before resuming. The saline irrigation could help slow the bleeding and sometimes stop the bleeding. Finally, after completing the decompression and discectomy, any active bleeding should be controlled before removing the endoscope, and hemostatic agents, such as tranexamic acid and gelatin sponges, may be used if necessary. ²⁴

Surgical Drainage

In cases of bleeding concerns, a surgical drain may be placed to evacuate any remaining fluid in the epidural space to prevent the risk of postoperative epidural hematoma. ⁴

Vertebral Artery Injury

Although there are no reports in the literature of vertebral artery injury during posterior endoscopic cervical surgery, precautions should always be taken to avoid this devastating complication. Vertebral artery injury has been reported in up to 11.7% of cases during posterior exposure and 1.8% during posterior foraminotomy in cervical spine surgery. ⁷¹ It is crucial to be aware of the location of the vertebral artery, particularly during approach near the neural foramen, especially if a partial pediculectomy is planned. Additionally, care should be taken when manipulating the cervical nerve root at the C5-6 level and above, as the vertebral artery lies closer to the midline in these regions due to its proximity to the lateral recess and nerve root. ⁷² Additionally, during decompression of the neural foramen, the circumference of the intervertebral disc space must be considered to avoid extending the decompression too anteriorly, which poses a risk of vertebral artery injury. ⁵⁵

Structural and Other Possible Complications

Recurrence and Revision Surgery

Regarding recurrent symptoms and reoperation after posterior cervical spinal surgery, Bydon et al utilized the conventional posterior cervical foraminotomy and found a 6.6% reoperation rate at the same level, with an average of 2.4 years follow-up. ⁷³ The recurrence of symptoms requiring revision surgery following posterior cervical ESS has also been reported in the literature. Ruetten et al reported 3.4% recurrence rates at the index level in their uniportal approach study. ²⁶ All patients underwent reoperation using the same technique as the first operation. Wu et al. also utilized the full-endoscopic approach and reported a 4% disc recurrence rate at the same level that occurred >2 years after the index procedure. ⁴⁶ Interestingly, several recent studies that utilized the full-endoscopic approach demonstrated no recurrent symptoms.^13,25,74 This suggests potentially lower recurrence rates following the full-endoscopic technique, although it may be underreported.

Preventative Measures Accurate Diagnosis and Appropriate Indication

Before performing posterior cervical ESS, it is essential to ensure a correct diagnosis and appropriate indication for surgery. Anteroposterior (AP), lateral, and dynamic plain radiographs of the cervical spine are recommended to confirm the absence of dynamic instability or deformities. Patients with significant cervical deformities and dynamic instability should be excluded from full-endoscopic cervical spinal procedures. Additionally, magnetic resonance imaging (MRI) and computer tomography (CT) provide crucial information for surgical planning. MRI should be carefully reviewed to assess the position and size of the herniated disc and degree of foraminal stenosis and to ensure that the index level of surgery correlates with the patient’s symptoms to prevent surgical failure from incorrect diagnosis.^29,57

Prevent Iatrogenic Instability

Excessive facet violation can lead to iatrogenic instability, given the facet joint’s critical role in cervical stability. To minimize this complication, preoperative measurement of the facet joint size on axial CT images is recommended to avoid excessive resection, as removing more than 50% of the facet joint can cause instability. ⁷⁵ Using the endoscopic drill size (typically 3-5 mm) as a reference during decompression, along with palpating the medial wall of the pedicle with an instrument such as a nerve hook, can help prevent excessive facet resection. Additionally, a tailored, limited removal of bony structures along the endoscopic release (ER) pathway, guided by direct endoscopic view, is recommended to reduce the risk of instability. ⁵³

Adequate Decompression

Decompression should address all relevant pathologies in each patient, such as cervical foraminal stenosis caused by disc herniation, uncovertebral joint hypertrophy or osteophytes, and central canal stenosis caused by OLF or facet cysts. After decompression, it is important to visualize the freely mobile and pulsatile nerve root or spinal cord. For bilateral stenosis at the same spinal level, specific surgical techniques may be applied. Bilateral or over-the-top decompression techniques can be used in full-endoscopic cervical spine surgery. This approach involves performing bony resection from the base of the spinous process to the contralateral lamina before resecting the ligamentum flavum, allowing for effective decompression of the contralateral side from the same surgical approach (Figure 4).^1,4,20,22 In certain cases, such as osseous foraminal stenosis, partial pediculotomy may be considered to ensure adequate decompression.^55,76

Figure 4.

Intraoperative findings following a posterior endoscopic unilateral laminotomy with over-the-top decompression for bilateral stenosis at the C6-7 level.

Incorrect Surgical Level/Difficulty Identified Surgical Level

Wrong-level surgery or difficulty in identifying the index surgical level can happen due to the proximity of interlaminar spaces in the cervical spine. ⁷⁷ Identification of the index level especially the lower cervical levels such as C5-6 or C6-7 in short neck patients using lateral fluoroscopy can be also challenging (Figure 5). Additionally, the disc space at these levels is more inclined than the upper levels. This could lead to wrong-level surgery, mostly at an adjacent upper level to the index level, because the surgeon tends to inadvertently handle and position the endoscope perpendicular to the floor, rather than following the proper trajectory during the procedure. To avoid this, it is crucial to accurately identify the correct surgical level and trajectory before proceeding with the operation and occasionally check the working trajectory from the fluoroscope throughout the procedure. ⁴

Figure 5.

The lateral fluoroscopic image demonstrates the obscured exposure of the lower cervical spine in a short-neck patient.

Preventative Measures Patient Positioning and Visualization

The surgical table should be tilted in the reverse Trendelenburg position, with the cervical spine parallel to the floor. This position ensures optimal orientation for the surgeon because the disc spaces are usually perpendicular to the floor. The shoulders are retracted caudally within physiological limits using adhesive tape to create better visualization, while the arms should be positioned alongside the body to avoid overlap during lateral fluoroscopy.^4,22,57 Additionally, padding bony prominences is crucial for minimizing nerve compression injuries.

Fluoroscopic Confirmation

After preparation and draping of the operative field, AP and lateral fluoroscopies are performed to localize and confirm the index level of the surgery and lamina-facet junction. Notably, some surgeons may prefer to introduce an 18-gauge needle, spinal needle, or Kirschner wire to confirm the level and “V” point under fluoroscopy before making the skin incision and inserting dilators (Figure 6).^1,4,20,22,78 For levels near the cervicothoracic junction, fluoroscopic visualization can be challenging. A double-needle technique, using one needle to identify a known reference level, helps ensure accurate identification of the correct level and trajectory before making an incision and inserting the tissue dilators. It is crucial to maintain the correct trajectory and recheck with lateral fluoroscopic images to confirm proper positioning during the procedure (Figure 7). ⁵³

Figure 6.

The lateral fluoroscopic image shows an example of using 22-gauge to identify the index spinal level before making a skin incision.

Figure 7.

The lateral fluoroscopic image demonstrates the intraoperative checking of the trajectory and location of the endoscope and drilling instrument during the procedure.

Role of the intraoperative navigation system

The intraoperative navigation system such as O-arm navigation (O-arm, Medtronic, Minneapolis, MN, USA) can be highly beneficial in full-endoscopic cervical spine surgery. This technology is especially useful in the lower cervical spine, where a short neck might obstruct intraoperative lateral fluoroscopy, providing improved accuracy and visualization.^45,79

Irrigation Fluid Extravasation

Another possible complication involving the irrigation system is fluid extravasation through the intramuscular fascial plane. This can occur because of unintentional displacement of the working cannula from the working area, prolonged surgery, or use of excessive water pressure. This fluid extravasation can potentially lead to soft tissue edema in the surrounding areas and cause pressure effects on nearby vital structures (Figure 8). ⁸⁰

Figure 8.

(A, B) A case of severe neck edema in a patient resulting from fluid extravasation into the intramuscular space of the posterior triangle following a full-endoscopic posterior cervical foraminotomy. (C) Ultrasound imaging demonstrating the presence of intramuscular fluid collection (asterisk). (D, E) The patient remained intubated for an additional 12 hours after the operation, and the edema resolved within two days.

Usage of the Mayfield Clamp

Some spine surgeons prefer stabilizing the patient’s head in the cervical flexion position to increase the interlaminar space by using a Mayfield clamp (Figure 3). However, care should be taken to avoid clamp-related complications, such as vascular injury, skull fracture, and CSF leakage. To mitigate these risks, it is crucial to select appropriate pin locations to avoid the neurovascular structures and weak areas of the skull. Employing the “Soccer Ball Concept” for pin placement can help minimize these complications. ⁸¹ Alternatively, the head can be placed on a foam face support, which spares space for the eyes, nose, and mouth. With this alternative, the head and neck can be easily adjusted and obtain the cervical flexion position.

Conclusions

Posterior full-endoscopic cervical spine surgery carries the risk of various complications, and current research provides limited guidance and consensus on their management. This emerging technique necessitates careful prospective comparative studies to assess its risks and benefits comprehensively. By thoroughly understanding these potential risks and developing extensive endoscopic surgical expertise, surgeons can prevent and reduce the occurrence of complications and enhance patient outcomes. In addition, future research is required to provide more comprehensive guidance for the management of posterior cervical full-endoscopic spine surgery.

ORCID iDs

Thanadol Tangdamrongtham https://orcid.org/0000-0002-4215-8880

Teerachat Tassanasoomboon https://orcid.org/0000-0002-2448-2118

Weerasak Singhatanadgige https://orcid.org/0000-0001-7166-1381

Worawat Limthongkul https://orcid.org/0000-0002-0116-8791

Yanting Liu https://orcid.org/0000-0002-9591-3042

Jin-Sung Kim https://orcid.org/0000-0001-5086-0875