INTRODUCTION
Cervical facet dislocation is a severe form of cervical spine injury, often resulting in significant neurological deficits and spinal instability, necessitating prompt and effective reduction and stabilization. Since Walton’s seminal description of closed reduction in 1893, substantial progress has been made in the development and refinement of reduction methodologies [1]. Traditional methods for reducing cervical facet dislocations include traction, closed manipulation, and open surgical techniques, each with varying degrees of success and associated complications. Anterior approaches, involving discectomy and fusion, may prove inadequate in certain cases, leading to the need for more invasive posterior procedures. Posterior cervical reduction and fixation offer direct visualization and reduction of dislocation, as well as decompression of any offending bony fragment compressing the cord [2]. However, the complexity and potential morbidity associated with extensive open procedures have spurred the exploration of minimally invasive techniques, aiming to achieve effective reduction while minimizing tissue damage and patient recovery time.
Unilateral biportal endoscopy (UBE) is a minimally invasive surgical technique that has gained popularity for its effectiveness in treating various spinal conditions. UBE-assisted posterior reduction offers a minimally invasive alternative for managing irreducible cervical facet dislocations, combining endoscopic visualization with familiar surgical techniques. This approach aims to reduce soft tissue damage while achieving safe reduction and stabilization.
SURGICAL TECHNIQUE
A 45-year-old man with a history of road traffic accident presented after 10 days with bilateral upper limb weakness and numbness. On clinical assessment, his right upper limb showed a motor power of 2/5 in the shoulder, elbow, and intrinsic muscles, and 3/5 in the left upper limb, with no sensory deficit. Lower limb power and sensation were intact, with no bladder or bowel concerns. Imaging revealed left C4–5 facet dislocation with fracture of the C4 inferior articular process (IAP) and a right C4–5 subluxation (Figures 1 and 2). MRI scan showed no traumatic disc herniation but cord edema at C4–5 levels (Figure 3). Patient consent in written format was taken.
1. Initial Management Attempt
A trial of closed reduction was attempted with the patient awake. Skeletal tongs were applied, and traction weight was increased up to 7 kg. This attempt failed as reduction was not achieved, and the patient experienced increased pain and numbness with further weight increase (Figure 4).
2. Decision for Surgery
Due to the failure of closed reduction, the patient was scheduled for surgical intervention.
3. Patient Positioning for UBE
The patient was placed in the prone position under general anesthesia for the UBE procedure on the left side.
4. Portal Creation for UBE
Two paramedian skin incisions, each 7–10 mm long, were made 1–2 cm lateral to the midline, centered over the C4–5 level. One incision served as the viewing portal, accommodating a 4-mm arthroscope (0° or 30°). The other incision served as the working portal for standard spinal instruments. Continuous saline irrigation with pressure maintained below 30 mmHg was used to ensure a clear surgical field. Triangulation of the arthroscope and instruments provided magnified, illuminated visualization (Figure 5).
5. Posterior Reduction Procedure via UBE
The dislocated left C4–5 facet joint was identified endoscopically. An initial attempt at reduction using direct manipulation with instruments (such as a chisel or lever) into the joint space was unsuccessful. Partial resection of the C5 superior articular process was performed using a high-speed burr (e.g., 3-mm diamond tip at 70,000 rpm) and a 1-mm Kerrison punch to facilitate reduction. The obstructing fractured bony fragment of the C4 IAP was identified and removed. Reduction of the facet dislocation was then successfully achieved using a curette to gently lever the facets into place (Supplementary Video Clip 1).
6. Patient Repositioning
After successful posterior reduction, the patient was carefully turned from the prone to the supine position.
7. Anterior Stabilization
An anterior approach was used to perform a C4–5 anterior cervical discectomy and fusion (ACDF) to stabilize the reduced segment (Figure 6).
DISCUSSION
1. Technical Scope and Limitations
This technical note specifically describes UBE-assisted posterior reduction for irreducible unilateral cervical facet dislocation due to a bony block. The technique is best suited for unilateral dislocations with a discrete, accessible bony impediment. Its application to bilateral dislocations or cases with extensive comminution remains unproven and should be approached with caution until further evidence is available.
2. Biomechanical Stability and Posterior Fixation
While posterior fixation plays a crucial role in the definitive stabilization of cervical facet dislocations, particularly for enhancing construct stability and promoting arthrodesis, the UBE technique described herein primarily focuses on facilitating the reduction of irreducible dislocations by addressing bony impediments. Although UBE-assisted lateral mass screw fixation has been explored by other groups as a potential means to achieve posterior stabilization with minimal invasiveness [3,4], this specific technical note did not incorporate or evaluate such an approach. For the presented case, the UBE procedure was solely for reduction, necessitating a subsequent ACDF for definitive stabilization. This underscores its role as a reduction-facilitating step rather than a standalone stabilization procedure. Future research into the biomechanical efficacy and widespread applicability of UBE-assisted posterior fixation techniques, particularly in the context of acute trauma, is warranted.
3. Indications and Generalizability
Based on this initial experience, UBE-assisted posterior reduction appears ideally suited for select cases of irreducible cervical facet dislocation, particularly those involving unilateral dislocations where a clear, accessible bony obstruction, such as a fractured IAP fragment, is the primary impediment to reduction. Its applicability to more complex scenarios, such as bilateral dislocations or cases with extensive comminution, may be inherently limited due to the confined working space and the technical demands of managing more diffuse pathology endoscopically. Crucially, as this report constitutes a technical note detailing an initial experience with a single patient, the successful outcome and observed benefits cannot be generalized. The safety, efficacy, and broader indications for this novel technique must be established through larger case series and comparative studies against established methods.
4. Advantages
Minimally invasive: UBE reduces tissue damage, blood loss, and postoperative pain. This subsequently leads to a decrease in hospitalization duration and expedites recovery, enabling patients to resume their daily activities more swiftly compared to traditional open surgical approaches [5].
Enhanced visualization: The endoscopic approach provides a clear, magnified view of the surgical field, improving precision.
Faster recovery: patients typically experience shorter hospital stays and quicker return to daily activities.
Reduced risk of infections: Open posterior cervical procedures, particularly involving instrumentation like lateral mass fixation for trauma, carry reported surgical site infection (SSI) rates ranging from approximately 4.5% to over 16%. Minimally invasive techniques like UBE may lower this risk due to factors such as continuous saline irrigation and reduced tissue disruption, which have been associated with very low infection rates (approaching zero) in established lumbar UBE series [6-9]. It is important to note that direct comparative data specifically for cervical UBE-assisted reduction remains limited. Therefore, while these promising findings from lumbar UBE are extrapolated to suggest a potential for reduced SSI risk in cervical applications, further cervical-specific studies are needed to confirm this benefit compared to traditional open posterior approaches.
Improved cosmetic outcomes: The use of small incisions results in minimal scarring, offering a cosmetic advantage over larger incisions required for open surgery [5].
5. Limitations
Steep learning curve and technical demand: Cervical UBE surgery is technically demanding due to the confined working space and proximity to critical neurovascular structures [10,11]. Applying it to the distorted anatomy of a facet dislocation, especially irreducible cases requiring bone resection and manipulation, requires significant expertise in UBE techniques [6].
Risk of neurological injury: Instrumentation, high-speed burrs, and reduction maneuvers are performed immediately adjacent to the spinal cord and nerve roots. Despite magnified visualization, the risk of iatrogenic dural tear, nerve root injury, or spinal cord injury exists and may potentially be higher than in standard UBE decompression cases or even open reduction.
Irrigation fluid management: Maintaining adequate continuous saline irrigation is crucial for visualization but requires careful management of inflow/outflow to avoid excessive epidural pressure, which could theoretically compromise neural tissue or lead to complications like postoperative hematoma or, rarely, increased intracranial pressure if outflow is inadequate [7].
Potential for incomplete reduction or conversion: Despite endoscopic visualization and efforts to clear the facet joint, achieving anatomical reduction may not always be possible endoscopically, necessitating conversion to a traditional open posterior approach.
Limited ability for direct posterior fixation: This technique primarily facilitates reduction. If posterior instrumentation were deemed necessary in addition to the ACDF, this would typically require conversion to an open procedure or a separate minimally invasive screw placement technique, which requires advanced skill.
Requirement for secondary anterior stabilization: The UBE procedure only addresses the posterior reduction; a subsequent ACDF may be necessary for definitive stabilization. This adds a posterior procedural step compared to cases reducible via closed or anterior means [2].
Case selectivity and limited generalizability: The technique is best suited for unilateral dislocations with a clear, accessible bony block responsible for irreducibility. Its applicability to bilateral dislocations or cases with extensive comminution may be limited. As this technical note describes an initial experience (a single case), the successful outcome cannot be generalized. Larger case series or comparative studies are required to establish the broader safety, efficacy, and indications for this technique compared to established methods.
CONCLUSION
UBE-assisted posterior reduction for irreducible cervical facet dislocation is a promising technique that combines the benefits of minimally invasive surgery with effective reduction and stabilization. Further studies and clinical trials are needed to establish its long-term efficacy and safety.
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