Neurological and Biomechanical Evaluation of 72 Patients with Degenerative Cervical Spondylotic Myelopathy at 3, 6, and 12 Months Following Anterior Cervical Corpectomy and Fusion

Introduction

Cervical spondylotic myelopathy (CSM) is a prevalent cause of spinal cord dysfunction in adults, and is characterized by degenerative changes in the cervical spine that lead to irritation or compression of the spinal cord and associated blood vessels [1–3]. As the most common cause of acquired myelopathy, its global incidence is significant, notably increasing with age: 4.04 per 100 000 person-years reported, especially affecting those over 50 years [4]. This pathological process results in sensory, motor, reflex, and bowel dysfunction of the spinal nerves, severely affecting the quality of life for patients [5,6]. Diagnosis typically combines the clinical assessment of neurological deficits with imaging results. While plain radiographs can show degenerative changes, magnetic resonance imaging (MRI) is preferred for visualizing cord compression and signal changes, and computed tomography (CT) is preferred for bony stenosis [7]. Clinical studies have shown that the progression of CSM is unpredictable, and without timely intervention, the prognosis is often poor. Therefore, although conservative management can be considered for mild cases under observation, early surgical treatment is generally recommended for moderate to severe CSM, to alleviate compression and improve outcomes [4,7,8].

Among various surgical approaches, anterior cervical corpectomy and fusion (ACCF) has emerged as an effective method for treating CSM, due to its ability to decompress the spinal cord, restore vertebral curvature, and enhance fusion rates [9]. Although ACCF demonstrates promising short-term outcomes, long-term follow-up studies have indicated that some patients experience degenerative changes in adjacent segments, potentially related to postoperative biomechanical alterations. However, the specific mechanisms underlying these biomechanical changes and how they influence the long-term outcomes of ACCF remain poorly understood. Thus, a comprehensive understanding of the biomechanical characteristics of the cervical spine after ACCF is crucial for assessing surgical efficacy, guiding postoperative rehabilitation, and preventing adjacent segment disease.

Currently, finite element analysis and fresh cadaver studies have been used to investigate the biomechanical properties of adjacent segments following ACCF [10–13]. However, these studies have limitations, such as small sample sizes, short-term follow-up, and a lack of detailed long-term analysis on cervical spine mobility. Additionally, while the range of motion of the vertebrae is commonly used to diagnose cervical spine diseases and assess treatment outcomes, its long-term changes after ACCF surgery have not been well documented in large cohorts. This knowledge gap is significant, as understanding how cervical spine mobility evolves over time can guide more effective surgical strategies and rehabilitation protocols.

Therefore, in this study, we aimed to perform a comprehensive neurological and biomechanical evaluation of 72 patients with degenerative CSM at 3, 6, and 12 months following ACCF.

Material and Methods

ETHICS STATEMENT:

This study was reviewed and approved by the medical ethics committee of our hospital (2023.A01). All patients signed informed consent forms.

GENERAL DATA:

After obtaining approval from the institutional review board, a retrospective single-center study was conducted. A total of 72 patients who underwent ACCF in our hospital from January 2020 to June 2022 were selected as the research participants, including 38 men and 34 women, aged 42 to 81 years, with an average of 52.34±6.88 years. The surgical segments were as follows: C5 vertebral body subtotal resection in 33 cases, C4 vertebral body subtotal resection in 25 cases, and C6 vertebral body subtotal resection in 14 cases.

INCLUSION AND EXCLUSION CRITERIA:

The inclusion criteria were as follows:

1) Patients with a diagnosis of CSM based on the modified Japanese Orthopaedic Association (mJOA) score ranging from 10 to 14, indicating moderate to severe spinal cord dysfunction, who had failed at least 3 months of standardized conservative treatment and had clear surgical indications were included. The mJOA score objectively reflects the severity of CSM, with a total of 17 points covering 4 dimensions: upper limb motor function (0–5 points), lower limb motor function (0–7 points), sensory function (0–3 points), and bladder function (0–2 points). 2) Cervical spine imaging, including CT and MRI, demonstrated definitive spinal canal stenosis with spinal cord compression. Imaging findings included, but were not limited to, high intramedullary signal intensity on T2-weighted MRI images, with the compression lesion primarily located posterior to the vertebral body. 3) Patients met the surgical indications for ACCF without any contraindications to surgery.

The exclusion criteria were as follows:

1) severe cardiovascular and cerebrovascular diseases, hepatic or renal insufficiency, hematologic disorders, or other systemic diseases that could significantly increase surgical risk or impair postoperative recovery; 2) primary neurological disorders, such as amyotrophic lateral sclerosis or multiple sclerosis, which could cause neurological dysfunction and confound the assessment of postoperative neurological outcomes; 3) traumatic brain injury or multiple trauma in patients whose neurological symptoms may not be related to cervical pathology; 4) history of severe cervical spine trauma or previous cervical surgery, to avoid confounding surgical outcomes due to prior conditions; 5) congenital spinal deformities, spinal tumors, spinal infections, or metabolic bone diseases, in order to exclude spinal disorders caused by non-degenerative or systemic diseases; and 6) history of inflammatory spinal diseases, such as rheumatoid arthritis.

Follow-up assessments were conducted at 3, 6, and 12 months postoperatively, with a mean follow-up duration of 14.22±5.32 months. This follow-up schedule was consistent with or exceeded that of several previously published studies evaluating the clinical and radiographic outcomes of anterior cervical procedures. For instance, Zhang et al reported a mean follow-up of 13.4±3.3 months for ACCF outcomes [14]. In a meta-analysis by Wang et al, the included study by Nguyen et al evaluated postoperative complications and reoperation rates with a follow-up of 12 months in patients undergoing surgical treatment for CSM [15,16]. Additionally, Banno et al analyzed outcomes within a 30-day postoperative window, using data from the National Surgical Quality Improvement Program, which is substantially shorter than our follow-up period [17].

While our follow-up duration provides valuable mid-term insights into the biomechanical and functional outcomes following ACCF, we acknowledge that adjacent segment degeneration is a progressive condition that typically evolves over several years. Therefore, longer-term follow-up will be essential in future studies to fully capture the biomechanical changes and degeneration that can occur at adjacent segments over time.

SURGICAL TECHNIQUE:

All surgeries were performed by the same experienced surgeons with over 10 years of specialization in orthopedic spine surgery. ACCF is a well-established surgical approach for CSM, performed to achieve spinal cord decompression and stabilization. Its application is guided by specific indications and comprehensive management considerations [18].

The surgery was performed as follows. After the induction of general anesthesia, the patient lay in a supine position with pillows on the shoulders and back to keep the head and neck in an appropriate extended position. At the same time, it was ensured that the neck remained stable, without excessive traction during the procedure, to allow adequate exposure of the anterior cervical region. Routine sterilization and draping were performed, and a transverse incision about 4 cm long was made on the right side of the front of the neck, which was exposed layer by layer to expose the front edge of the cervical vertebral body. During this process, it was essential to carefully protect the carotid artery, internal jugular vein, vagus nerve, and particularly the right recurrent laryngeal nerve, to avoid iatrogenic injury. A C-arm fluoroscopy was used to accurately identify the diseased vertebral segment, which was then marked.

The anterior fascia of the vertebral body was incised, and a rongeur was used to perform a subtotal resection of the diseased vertebral body. The intervertebral disc tissue, cartilage endplate, posterior vertebral body osteophytes, and posterior longitudinal ligament were removed and fully decompressed.

The completeness of decompression was confirmed by direct visualization of good spinal cord pulsation, restoration of the perispinal space, and full release of the nerve roots. Care was taken during decompression, to avoid injury to the vertebral artery and the dural sac.

According to the intervertebral space after decompression and the need to restore cervical physiological curvature, an appropriately sized titanium cage was trimmed and filled with autologous bone fragments or allograft bone. The cage was then carefully implanted into the decompressed intervertebral space, ensuring tight contact between the cage and the endplates of the adjacent vertebrae and a stable position.

After the position of the titanium cage was fixed and stable and the spreader was removed, a suitable steel plate was used to fix the adjacent cages. Under fluoroscopy, it was clear whether the fixed position was satisfactory. Then, bleeding was completely stopped, the incision was rinsed, a drainage tube was placed, the incision was sutured layer by layer and covered with dressing, and fixation with a cervical collar was done to complete the operation.

POSTOPERATIVE MANAGEMENT:

Postoperative antibiotic treatment and perioperative pain management were given. Rapid recovery was achieved. On the first postoperative day, once the effects of anesthesia subsided, and the vital signs stabilized, patients were encouraged to sit up gradually with the assistance of medical staff, provided there were no significant discomforts. Gentle muscle movements of the fingers, toes, and lower limbs were initiated. For the first 3 days, the patients walked without discomfort after sitting up and did exercises, including for the fingers, chest, and legs. For the next 4 days, the patients wore a neck collar and moved around carefully. The patients also did exercises for hair, elbows, shoulders, and neck to help the cervical spine recover. Sutures were removed based on the wound condition 8 days after surgery; after discharge, the patients were instructed to do exercises every 3 days and to follow up once every month.

After spine fixation, patients were immobilized using a cervical orthosis for stability and comfort and closely monitored for potential complications, such as infection, hardware mobilization, and nonunion.

OUTCOME MEASURES:

All outcomes were assessed preoperatively and at 3, 6, and 12 months postoperatively by trained physicians or technicians. The outcome measures were as follows: (1) neurological function: evaluated by the mJOA score (total 17 points; upper limb motor, lower limb motor, sensory, and bladder function); neck disability index (NDI): patient-reported measure for daily activity limitations due to neck pain (10 items, 0–50 points); and (3) visual analog scale (VAS): 0–10 scale for neck pain intensity. Assessments were performed by the same experienced examiner, to ensure consistency.

A cervical spine 3-dimensional (3D) mobility measurement [19] was performed. Before surgery and at 3, 6, and 12 months after surgery, cervical spine mobility was assessed using the Coda motion 3D motion analysis system (Charnwood Dynamics, UK) [20], which has been validated for reliability and precision in similar studies. The system was calibrated according to the manufacturer’s guidelines by a trained technician. Measurements included cervical spine flexion, extension, lateral flexion, and rotation, and were taken in triplicate to ensure consistency. The 3D mobility measurements of the cervical spine were all completed by the same physician.

Standardized anteroposterior and lateral cervical spine X-rays were performed preoperatively and at 12 months postoperatively on all patients. Images were digitized and analyzed using the hospital’s image archiving and communication system. The C2–C7 Cobb angle, C2–C7 sagittal vertical axis (SVA), and T1 slant angle (T1 S) were measured by 2 independent, blinded orthopedic radiologists with a minimum of 5 years of experience in spinal imaging. Discrepancies were resolved by consensus or by a third radiologist.

STATISTICAL ANALYSIS:

To account for potential confounders, such as age and the severity of CSM, we ensured that the baseline characteristics of patients were as homogenous as possible by setting clear inclusion criteria based on the mJOA score, which objectively reflects the severity of CSM. However, due to the relatively small sample size and consistent baseline characteristics, we did not perform multivariate regression analyses to statistically adjust for these variables.

Descriptive statistics were used to summarize general characteristics of the patients. Continuous variables were tested for normality using the Shapiro-Wilk test. Means±standard deviations (SD) were reported for continuous variables with a normal distribution, while non-normally distributed data were presented as median and range. The Mann-Whitney U test was used for non-normal data. Paired t tests were used to compare preoperative and postoperative measures at the same time point for normally distributed continuous variables. Conversely, the Wilcoxon signed-rank test was used for variables that were not normally distributed. To control for the risk of type I errors in multiple comparisons, P values were adjusted using the Bonferroni correction. SPSS (version 20.0; IBM Corp, Armonk, NY, USA) statistical software was used for data analysis.

Results

FOLLOW-UP DURATION:

The follow-up time of the enrolled patients was >12 months, and the longest follow-up time was 27 months, with an average of 14.22±5.32 months.

CERVICAL SPINE RANGE OF MOTION:

Analysis of the 3D mobility measurement results of the patients’ cervical spine was conducted before and after surgery. Three months after surgery, the cervical spine’s forward flexion, back extension, and right flexion range of motion were lower than before surgery, and the difference was statistically significant (P<0.05). For left flexion, there was no statistically significant difference in right rotational range of motion compared with preoperative levels. Six months after surgery, there was no statistically significant difference in cervical spine mobility compared with preoperative levels; cervical spine extension mobility was higher than that at 3 months after surgery, and the difference was statistically significant (P<0.05). For cervical spine forward flexion and right flexion, there was no statistically significant difference in the range of motion of left flexion, left rotation, and right rotation, compared with 3 months after surgery. Twelve months after surgery, the right flexion and left rotation range of the cervical spine were higher than those before surgery, and the difference was statistically significant (P<0.05). There was no statistically significant difference in rotational range of motion compared with that before surgery. Cervical spine extension, right flexion, left flexion, and left rotation range of motion were all higher than those 3 months and 6 months after surgery, and the difference was statistically significant (P<0.05; Table 1).

NEUROLOGICAL FUNCTION:

Comparison of neurological function scores revealed continuous improvement after surgery. At 3, 6 and 12 months after surgery, the patients’ upper limb motor function, lower limb motor function, sensory function, bladder function scores and total mJOA scores were all higher than those before surgery (P<0.05). At 6 months after surgery and 12 months after surgery, the patients’ upper limb motor function, lower limb motor function, sensory function, bladder function scores, and total scores were all higher than those 3 months after surgery, and the difference was statistically significant (P<0.05). The patients’ upper limb motor function 12 months after surgery, lower limb motor function, sensory function, and total score were all higher than those 6 months after surgery (P<0.05; Table 2).

RADIOLOGICAL PARAMETERS:

Comparison of imaging parameters of patients before and after surgery showed that, after 12 months of follow-up, the patients’ C2–C7 Cobb angle, C2–C7 SVA, and T1 S were all greater than those before surgery, and the differences were statistically significant (P<0.05; Table 3, Figure 1).

NECK DISABILITY INDEX:

At 3, 6, and 12 months after surgery, the patients’ NDI scores were lower than those after surgery. Six and 12 months after surgery, the patients’ NDI scores were lower than at 3 months after surgery, and scores at 12 months after surgery were lower than at 6 months after surgery. The differences were statistically significant (P<0.05), see Table 4.

PAIN INTENSITY:

Significant reductions in the VAS scores indicated a substantial improvement in patients’ pain levels at 3, 6, and 12 months after surgery (P<0.05). Furthermore, the decrease in the NDI scores further corroborated the effectiveness of ACCF surgery in alleviating pain and enhancing patients’ ability to perform daily activities (Table 4).

LONG-TERM CONSIDERATIONS:

While the follow-up period was 12 months, we acknowledge the need for longer-term follow-up studies to assess the durability of clinical and biomechanical improvements over time.

Discussion

LIMITATIONS:

First, this was a retrospective study, which can have selection bias, confounding factors, and other factors that affect the validity and reliability of the results. Second, there were inherent weaknesses in data collection, the sample size was relatively small, and the follow-up time was short, which may not show the difference in long-term effects between the 2 surgical methods. Additionally, we were unable to comprehensively evaluate the long-term complications following ACCF. Third, this was not a multicenter large-sample study, which could affect the statistical power and generalizability of the results. Researchers conducting future studies should consider multicenter, large-sample cohort studies with extended follow-up periods, to further clarify the long-term efficacy of ACCF. Additionally, although this study provided detailed objective measurements, it lacked assessments of quality of life and other subjective outcomes. Although we attempted to ensure baseline homogeneity by including only patients with moderate CSM based on the mJOA score, we did not perform multivariate statistical adjustments for potential confounding variables, such as age and disease severity. As a result, residual confounding cannot be entirely excluded. Future studies with larger sample sizes and appropriate multivariate modeling are needed to control for these factors more effectively. Moreover, although our study assessed overall cervical sagittal alignment and mobility, we did not perform a direct analysis of adjacent segment biomechanics, such as segment-specific range of motion or radiographic degeneration. Therefore, the biomechanical response of adjacent segments to ACCF cannot be fully characterized based on our present data. Future studies should incorporate segment-level motion analysis or longitudinal radiographic follow-up, to better evaluate adjacent segment biomechanics. Finally, we acknowledge that adjacent segment degeneration is a progressive condition that typically manifests clinically or radiographically over a period of 5 years or more [14,45]. Therefore, while our follow-up duration provides valuable mid-term insights, it may not fully reflect the long-term biomechanical changes associated with adjacent segment degeneration. Future longitudinal studies with extended follow-up periods (≥5 years) are warranted to comprehensively evaluate adjacent segment degeneration progression. In addition, this study did not incorporate patient-reported outcome measures, such as quality of life, postoperative satisfaction, or subjective functional recovery. Future studies should include standardized patient-reported outcome measures, to provide a more comprehensive evaluation from the patient’s perspective.

Conclusions

ACCF significantly improved cervical biomechanics and neurological function in patients with degenerative CSM, leading to better clinical outcomes. However, this study did not directly assess adjacent segment biomechanics or long-term degenerative changes. Further long-term studies with extended follow-up and segment-specific evaluations are needed to confirm the durability of these results and clarify the risk of adjacent segment degeneration.