Anterior cervical V-Slot decompression and fusion for long-segment cervical ossification of the posterior longitudinal ligament: a follow-up study

Abstract

Cervical ossification of the posterior longitudinal ligament (OPLL) causes spinal cord compression due to spinal canal stenosis. Traditional anterior approaches such as anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF) have limitations, including restricted decompression range, extensive vertebral resection trauma, or insufficient stability. This study aimed to evaluate the efficacy and safety of a novel surgical technique—Anterior Cervical V-Slot Decompression and Fusion (ACVDF)—for treating long-segment OPLL. A retrospective analysis was conducted on 30 patients with multilevel OPLL who underwent ACVDF between December 2021 and March 2024. A curved grinding drill was used to precisely remove portion of the vertebral body and ossified tissue (≤ 50% of the sagittal diameter) through the V-shaped distracted intervertebral space, achieving direct decompression of long-segment OPLL During surgery. Postoperative follow-up 14.70 ± 1.62 months (12–18 months). Clinical outcomes were assessed using the Japanese Orthopaedic Association (JOA) score, visual analog scale (VAS) score, and imaging methods such as CT and MRI. All 30 patients successfully completed the surgery, with a mean operative time of 143.17 ± 10.96 min and intraoperative blood loss of 177.67 ± 49.45 ml. At the final follow-up, the JOA score improved from 8.50 ± 1.96 to 14.67 ± 0.71 (P < 0.05), with an excellent and good rate of 90.00%. The VAS score decreased from 6.53 ± 1.53 to 1.30 ± 0.79 (P < 0.05). The spinal canal occupancy rate decreased from 42.13 to 10.61% (P < 0.05). The Height of the fused segments was 62.70 ± 13.58 mm at 1 week postoperatively and increased to 62.94 ± 13.99 mm at the final follow-up (P > 0.05). Cervical range of motion (ROM) decreased from 51.57 ± 8.96° preoperatively to 33.07 ± 6.18° at the final follow-up (P < 0.05). The fusion rate reached 100% at the final follow-up. No complications such as dural tears or spinal cord injuries occurred during surgery. ACVDF can achieve direct decompression of long-segment OPLL while preserving anterior column structures, maintaining cervical stability, and getting favorable clinical outcomes. This technique provides a new safe and effective treatment option for long-segment OPLL.

Introduction

OPLL is a disorder characterized by Heterotopic ossification of the posterior longitudinal ligament, leading to spinal cord compression and neurological dysfunction. The cervical spine is one of the most affected regions. OPLL can be classified into localized, continuous, segmental, and mixed types. The reported prevalence of OPLL in individuals over 30 years old is as high as 4.3% [1].

The progression of cervical OPLL is irreversible, and surgical intervention still the most effective treatment. Surgical approaches are divided into anterior and posterior methods. Posterior approaches, such as cervical laminectomy and laminoplasty [2], offer lower operative risks and fewer complications. However, their indirect decompression effect, achieved by posterior displacement of the spinal cord, is often inferior to direct decompression via anterior approaches. In contrast, anterior approaches enable more thorough spinal cord decompression by directly removing ossified lesions, resulting in better clinical outcomes despite higher surgical risks and complication rates [3–5]. Among anterior techniques, ACDF is considered the “gold standard” for cervical spondylosis due to its standardized procedure and reliable efficacy [6]. However, its limited operative field poses challenges for addressing posterior ossified lesions [7]. ACCF effectively removes posterior ossified lesions but requires extensive vertebral resection, increasing the risks of complications such as dural tears and implant subsidence [8–10]. Moreover, reduced fixation segments may lead to biomechanical deficiencies, and compromising stability as the force arm length increases [11]. Additionally, irreversible loss of normal intervertebral discs may accelerate cervical motion degeneration. This “efficacy-trauma” paradox highlights the need for a technique that retains the minimally invasive and biomechanical advantages of ACDF while overcoming its limitations in addressing posterior vertebral body lesions—a key scientific challenge in optimizing OPLL surgical strategies.

To expand the decompression range of ACDF, various modifications have been proposed. Sun et al. introduced anterior controllable ante displacement fusion (ACAF) [12], which involves partial anterior vertebral resection and anterior displacement of the posterior vertebral body and ossified posterior longitudinal ligament to enlarge the spinal canal. While ACAF extends the applicability of anterior approaches for long-segment OPLL, it remains an indirect decompression method and carries risks such as significant trauma and vascular injury [13]. Lei et al. [7] first proposed the concept of extended ACDF for severe localized OPLL, achieving broader decompression by resecting the posterior endplate and part of the vertebral body through the intervertebral space. Lee et al. [3] later applied this technique to cervical spondylosis, further validating its feasibility and efficacy.

Currently, there is no optimal surgical solution for continuous or mixed-type long-segment OPLL. Building on Lei et al.‘s work, we innovatively developed ACVDF. This technique combines extended ACDF to directly decompress long-segment OPLL while preserving most of the vertebral bone structure, providing stable fixation points for implants and ensuring postoperative cervical stability. This study details the surgical technique and reports clinical and radiological outcomes, offering a new reliable option for long-segment OPLL.

Materials and methods

General information

This retrospective study was approved by the local ethics committee (KLL-2022-551), and all patients provided informed consent.

Inclusion criteria: (1) Diagnosis of multilevel (≥ 2 segments) cervical OPLL; (2) Clinical symptoms consistent with imaging findings; (3) Progressive worsening of spinal cord compression symptoms; (4) Minimum follow-up of 12 months. Exclusion criteria: (1) Previous surgery at the target segments; (2) Concurrent intraspinal tumors, cervical infections, or intramedullary lesions; (3) Severe osteoporosis; (4) Localized OPLL; (5) Chronic underlying diseases incompatible with anesthesia. Based on these criteria, 30 patients treated between December 2021 and March 2024 were enrolled. Demographic and clinical characteristics are summarized in Table 1.

Table 1.

Demographic and clinical characteristics of patients

Parameter	Value
Age (years)	51.5 ± 8.91 (35~67)
Genders (male/female)	18/12
BMI (kg/m2)	20.49 ± 4.97(13–28)
Smoking	11
Duration of symptoms (months)	13.63 ± 3.39(6–21)
Continuous type	7
Segmental type	18
Mixed type	5
Follow-up (months)	14.70 ± 1.62(12–18)

Surgical design and technique

The patient was placed in a supine position with the neck slightly rotated to one side. General anesthesia was administered via oral or nasal intubation, and intraoperative neurophysiological monitoring was implemented. After localizing the target segment using C-arm fluoroscopy, a transverse or longitudinal incision was made in the anterior neck. The visceral and vascular sheaths were carefully separated to expose the target vertebral bodies and intervertebral spaces.

Under microscopic assistance, the anterior intervertebral disc tissue was first resected and gradually deepened. A curved high-speed burr was then used to remove the OPLL at the posterior aspect of the disc space until it was thinned into a sheet-like structure (Fig. 1a). The lateral extent of resection was confined to the ossification margins. At regions with minimal spinal cord compression (typically located on both sides of the spinal cord, as confirmed preoperatively) a small hole was carefully drilled using the curved high-speed burr to avoid drill displacement and potential spinal cord injury (Fig. 1b). Subsequently, Rongeurs were used to gradually remove the remaining thin ossified fragments at the segment until the dura mater was exposed, indicating that sufficient decompression of that intervertebral space had been achieved.

Fig. 1.

Schematic diagram of the surgical procedure. (a) A curved high-speed burr is used to thin the ossified mass into a sheet-like structure; the ossified posterior longitudinal ligament is shown in orange and indicated by the black arrow. (b) A small hole is drilled into the sheet-like ossified mass at a site without significant spinal cord compression using a curved high-speed burr, followed by resection along the hole to decompress the intervertebral space. (c) The intervertebral space is distracted into a “V” shape. (d) A curved high-speed burr is used to obliquely resect the posterior portion of the endplate and vertebral body. The ossified mass is thinned into a sheet, and the same technique is used for its removal. (e) Residual thin ossified fragments are removed using a rongeur. (f) The operated segment is stabilized with an interbody fusion cage and titanium plate

Next, the intervertebral space was distracted into a “V” shape to enlarge the anterior working space, facilitating subsequent vertebral body resection (Fig. 1c). After distraction, the curved high-speed burr was reintroduced, and its tip was positioned posteriorly at the midpoint of the inferior endplate of the cranial vertebral body. Using the angled orientation of the burr, the posterior half of the endplate and a portion of the vertebral body were obliquely resected in a cranial direction, with the burr angled at 45°−50° relative to the endplate. The sagittal length of endplate resection did not exceed 50% of the vertebral body to preserve space for fusion cage placement. The same procedure was performed at the caudal vertebral body, resecting part of the superior endplate and vertebral structure. During this process, posterior ossified structures were thinned into a sheet-like fragment to avoid direct resection and minimize the risk of dural tear (Fig. 1 d). Hemostasis was achieved as needed using bone wax throughout the procedure.

After the resection was completed, residual posterior sheet-like ossified structures were carefully removed. A small hole was drilled again at an area with minimal spinal cord compression, and Kerrison rongeurs were used to sequentially excise the remaining ossified fragments until the ossification was completely removed within the visual field and spinal cord decompression was fully achieved (Fig. 1e). If the ossified mass was not tightly adherent to the dura, a curette was used to gently separate it. If adhesion was tight, forced separation was avoided to prevent dural tears. In such cases, the residual ossification was retained; since the anterior portion of the vertebral body and most of the ossified mass had already been resected, the remaining lesion no longer caused spinal cord compression.

Upon completion of decompression, meticulous hemostasis was performed. An appropriately sized interbody fusion cage filled with autologous bone was inserted into the intervertebral space, and a titanium plate of suitable length was used for fixation (Fig. 1f). A drainage tube was placed, and the incision was closed in layers.

Postoperative management

Routine postoperative care included infection prevention. The drainage tube was removed when output was < 10 mL/day. A cervicothoracic brace was worn for 3 months, and regular follow-ups were conducted.

Outcome evaluation

Patients were followed up at 1, 3, 6, and 12 months postoperatively. Imaging evaluations included X-rays, CT, and MRI. Clinical outcomes were assessed using:

(1) VAS for pain [14]. (2) JOA score for neurological function [14]. (3) JOA improvement rate: (Postoperative JOA – Preoperative JOA)/(17 – Preoperative JOA) × 100%. Recovery rates were categorized as excellent (≥ 75%), good (50–74%), fair (25–49%), or poor (< 25%) [15]. (4) Fused segment height: Measured from the central upper endplate of the cranial vertebra to the central lower endplate of the caudal vertebra [7]. (5) Cervical ROM: Sum of Cobb angles in flexion and extension, measured using lines parallel to the C2 and C7 endplates [16]. (6) Spinal canal occupancy rate: Ratio of ossified mass to spinal canal area on axial CT [7]. (7) Fusion rate: Defined as trabecular bone bridging on CT [7].

Statistical analysis

Data was analyzed using SPSS 29.0 (IBM Corp., Armonk, NY, USA, Version 29.0). Continuous variables were expressed as mean ± standard deviation (x̄ ± s). Repeated measures ANOVA and Bonferroni post-hoc tests were used for intra-group comparisons. Categorical variables were analyzed using χ² or Fisher’s exact tests. A two-tailed P < 0.05 was considered statistically significant.

Results

Clinical outcomes

All surgeries were performed by the same surgeon. The mean operative time was 143.17 ± 10.96 min (123–165 min), and intraoperative blood loss was 177.67 ± 49.45 mL (100–300 mL). The VAS score improved from 6.53 ± 1.53 preoperatively to 1.30 ± 0.79 in the final follow-up (P < 0.05). The JOA score improved from 8.50 ± 1.96 to 14.67 ± 0.71 (P < 0.05) (Table 2). The JOA improvement rate was 70.6 ± 13.3% (33.3–88.9%), with excellent results in 16 cases, good in 12, and fair in 2 (excellent-to-good rate: 90.00%). No complications such as cerebrospinal fluid leakage, hematoma, infection, esophageal fistula, vascular injury, or neurological deterioration occurred.

Table 2.

Clinical functional outcomes at each follow-up time point after surgery (n = 30)

Time Point	Preoperative	1 Month	3 Months	6 Months	12 Months
JOA	8.50 ± 1.96	12.23 ± 1.43*	13.40 ± 0.86*∆	14.07 ± 0.91*∆◊	14.67 ± 0.71*∆◊#
VAS	6.53 ± 1.53	3.90 ± 1.40*	2.50 ± 1.11*∆	1.67 ± 0.80*∆◊	1.30 ± 0.79*∆◊#

*Compared with preoperative values, P < 0.05; ∆compared with 1-month postoperative values, P < 0.05; ◊compared with 3-month postoperative values, P < 0.05; #compared with 6-month postoperative values, P < 0.05

Radiological outcome

The Height of fused segments increased from 62.70 ± 13.58 mm preoperatively to 62.94 ± 13.99 mm at the final follow-up (P > 0.05). Cervical ROM decreased from 51.57 ± 8.96° to 33.07 ± 6.18° (P < 0.05). The spinal canal occupancy rate decreased from 42.13 ± 5.27% to 10.61 ± 4.59% (P < 0.05). The fusion rate was 67% at 3 months, 93% at 6 months, and 100% at 12 months (Table 3).

Table 3.

Radiological outcomes at each follow-up time point after surgery (n = 30)

Parameter	Preoperative	3 Months	6 Months	12 Months
Fused segment height(mm)	62.70 ± 13.58 (38.50–85.70)	62.57 ± 13.97 (35.70–87.20)	62.82 ± 14.08 (35.60–88.20)	62.94 ± 13.99 (36.90–87.20)
Cervical ROM(°)	51.57 ± 8.96 (30.00–66.00)	28.50 ± 5.24 (17.00–41.00) *	32.63 ± 5.91 (21.00–46.00) *◊	33.07 ± 6.18 (21.00–47.00) *◊
Spinal canal occupancy(%)	42.13 ± 5.27 (33.00–52.00)	9.83 ± 4.81 (0.00–18.00) *	10.27 ± 4.78 (1.00–18.00) *◊	10.61 ± 4.59 (2.00–18.00) *◊
Fusion rate(n, %)	-	20/30 (67%)	28/30 (93%)	30/30 (100%)

*Compared with preoperative values, P < 0.05；◊compared with 3-month postoperative values, P < 0.05

The fusion rate is the number and percentage of patients achieving imaging fusion at each time point

Case illustration

A 57-year-old female presented with bilateral upper limb numbness for 6 months and unsteady gait for 1 month. Neurological examination revealed elbow joint numbness, muscle strength of 4/5 in all limbs, positive pathological signs, VAS score of 6, and JOA score of 9. Preoperative CT and MRI showed spinal cord compression at C4–C6 due to OPLL (Fig. 2). ACVDF was performed under general anesthesia. Postoperative MRI confirmed decompression (Fig. 3), and symptoms improved progressively with complete fusion at follow-up.

Fig. 2.

Preoperative MRI and CT images of the patient’s cervical spine. a and b: Cervical spine MRI sagittal and cross-sectional T2 images showed obvious compression and deformation of the cervical spinal cord in the cervical segments of 4–6, and signal changes of the spinal cord were present. c and d: Cervical spine CT sagittal and cross-sectional images showed ossification of posterior longitudinal ligaments of the C5 and C6 vertebrae. The yellow arrows indicate the ossified mass

Fig. 3.

Postoperative MRI and CT images of the patient’s cervical spine. a and b are sagittal and cross-sectional T2 images of the cervical spine, which showed that the spinal cord compression had been relieved, and the morphology of the spinal cord was basically restored to normal. c and d are CT images of the cervical spine, which showed that the ossification of the posterior margin of the vertebral body had been completely removed, and the diameter of the spinal canal was significantly enlarged compared with that of the preoperative period

Discussion

Long-segment cervical OPLL poses significant surgical challenges. Traditional anterior approaches, such as ACDF, are limited by their narrow operative field, making them unsuitable for multilevel posterior ossified lesions, especially continuous or mixed-type OPLL [17]. ACCF provides broader decompression but requires extensive vertebral resection, increasing complications like dural tears and pseudoarthrosis [18, 19]. Posterior approaches, while safer, offer only indirect decompression and are less effective for ventral compression, particularly in patients with cervical kyphosis [20] or K-line negativity [21]. Thus, balancing effective direct decompression with minimal trauma and stability preservation is critical.

By integrating the respective advantages of ACDF and ACCF, this study innovatively proposes ACVDF. The greatest strength of this technique lies in its “targeted resection and precise decompression.” Compared to ACDF, ACVDF significantly expands the decompression range in the sagittal plane by obliquely resecting the posterior portion of the endplate and ossified lesions through the intervertebral space, overcoming the limited operative field inherent to ACDF [22]. Furthermore, this technique preserves most of the vertebral bony structure, avoids the extensive vertebral resection required by ACCF, reduces operative time and intraoperative blood loss, and crucially provides stable bony anchoring points for interbody fusion. The JOA score improved significantly from 8.50 ± 1.96 to 14.67 ± 0.71 (P < 0.05), indicating substantial neurological recovery. This suggests good overall functional compensation of the cervical spine, minimal impact on daily activities, and an acceptable reduction in mobility. Moreover, the exposed cancellous bone creates an optimal osteogenic microenvironment for interbody fusion [23], further reducing the risk of fusion failure. The 100% fusion rate in this study confirms its reliability. Additionally, the postoperative VAS score decreased from 6.53 to 1.30 (P < 0.05), further supporting the improvement in quality of life offered by this procedure.

In this study, the curved design of the grinding drill enables it to tilt cephalad and caudad after entering the intervertebral space, allowing resection of the posterior endplate and vertebral body to expose the posterior ossified lesions. This significantly expands the surgical field and operating space, effectively addressing the limited visualization encountered in traditional trans-intervertebral resection of ossified posterior longitudinal ligament. Furthermore, intraoperative use of distractors to create a V-shaped intervertebral space further enlarges the operative range. Through these methods, complete resection and decompression of the posterior vertebral wall can be achieved. The continuous microscopic assistance throughout the procedure also ensures precise manipulation and optimal visualization of the surgical field.

For broad-based ossified lesions, this technique employs gradual deep-layer grinding until the ossification is reduced to a thin fragment. And only then resects the attachment point of the residual ossification from the posterior wall of the vertebral body and removes the residual ossification. This approach prevents direct contact between surgical instruments and the spinal cord during initial bone removal. In cases of dural-adherent ossifications where complete resection is unachievable, that could partial resection of the posterior vertebral body combined with thinning the ossified mass into a laminar fragment enables anterior flotation of the residual lesion. This maneuver successfully expands the spinal canal diameter also can achieve satisfaction.

Preoperative CT imaging should be utilized to plan the resection range, primarily to determine the extent of resection for the endplates and the posterior vertebral margin, with the aim of minimizing damage to the osseous structures of the spine. When the ossification at the cephalad and caudal segments does not exceed half of the vertebral height, the starting point and angle of the curved grinding drill during endplate resection should be adjusted to reduce the length of endplate resection and the extent of vertebral osseous structure removal, thereby maximizing the preservation of the vertebral body’s mechanical integrity. This is critical for preventing postoperative vertebral collapse and implant subsidence. In this study, the length of the resected posterior endplate generally did not exceed 50% of the total endplate. The preserved anterior vertebral column, together with the posterior column structures, shares axial loading, thereby reducing the risk of vertebral collapse commonly observed like ACCF. The final follow-up results in this study showed no significant change in the height of the fused segments (P > 0.05), confirming the pivotal role of preserved vertebral structures in maintaining cervical stability. However, the cervical ROM decreased from 51.57 ± 8.96° preoperatively to 33.07 ± 6.18° postoperatively (P < 0.05). The reduction in cervical ROM is an expected outcome of fusion surgery, indicating enhanced stability at the fused segments.

Additionally, the following technical considerations require particular attention:

• (1) Precision in Resection Range: The grinding drill resection must be meticulously controlled, avoiding excessive lateral extension beyond the dural sac to prevent vertebral artery or lateral nerve root injury. Over-resection in the sagittal plane may compromise cage placement and lead to cervical instability. (2) Intraoperative Neuromonitoring: Continuous neurophysiological monitoring is essential to promptly detect spinal cord traction or ischemic signals, thereby minimizing the risk of spinal cord injury. (3) Management of Dural Adhesion: In cases of dural adhesion, complete ossification removal should not be pursued at the expense of safety. A thin residual ossified fragment may be left in situ to ensure adequate decompression while reducing the risk of cerebrospinal fluid leakage and spinal cord injury.

Although this study demonstrates favorable outcomes of the presented technique for long-segment OPLL, several limitations should be acknowledged. First, this was a single-center retrospective analysis with a relatively small sample size (n = 30). Second, the mean follow-up Duration was 14.70 ± 1.62 months (range: 12–18), which may be insufficient to evaluate long-term efficacy, particularly regarding adjacent segment pathology. Additionally, all procedures were performed by a single surgeon, potentially introducing operator bias. Future studies should involve multicenter randomized controlled trials with larger cohorts, extended follow-up periods, and direct comparisons with alternative surgical approaches (e.g., ACCF, ACAF) to enhance the robustness of the findings.

Conclusion

ACVDF can achieve direct decompression of long-segment OPLL while preserving anterior column structures, maintaining cervical stability, and getting favorable clinical outcomes. This technique provides a new safe and effective treatment option for long-segment OPLL.

Abbreviations

OPLL

ossification of the posterior longitudinal ligament

ACDF

anterior cervical discectomy and fusion

ACCF

anterior cervical corpectomy and fusion

ACVDF

Anterior Cervical V-Slot Decompression and Fusion

JOA

Japanese Orthopaedic Association

VAS

Visual Analog Scale

ROM

Cervical range of motion

ACAF

anterior controllable ante displacement fusion

Author contributions

DQ and XZJ designed and directed the study, YS and YJB were the executors of surgeries, collection of follow-up data and writing of the manuscript. LDL were involved in the collection of follow-up data and the analysis of the data. WFJ and JWJ assisted in the patient’s surgeries as assistants.

Funding

1. Guizhou Provincial Science and Technology Program Project, Qiankehe Achievement-LC[2023]003;

2. the Basic Research Program of Guizhou Provincial Department of Science and Technology (Qiankehe Foundation-ZK [2024] General-347);

3. the Science and Technology Plan Projects of Zunyi City, Feasibility Study on Establishing a Degenerative Cervical Spinal Stenosis Detection and Grading Model Based on Artificial Intelligence, grant number: Zunshi Kehe HZ (2024) No. 432.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

This study approved by the Ethics Committee of The Affiliated Hospital of Zunyi Medical University (KLL-2022-551) in 2022. All patients signed informed consent forms. All methods were performed in accordance with the relevant guidelines and regulations.

Consent for publication

Not Applicable.

Competing interests

The authors declare no competing interests.

Trial registration numbers

ChiCTR1900027083. Registered 31 Oct. 2019. Trial registry: Chinese Clinical Trial Registry.