Cervical Cage Subsidence
Cervical cage subsidence is a term used in the field of spinal surgery and orthopedics to describe a potential complication associated with cervical interbody fusion procedures. In these procedures, a cervical cage, also known as a cervical interbody cage or fusion cage, is typically implanted between two adjacent vertebrae in the cervical spine (neck) to treat conditions such as cervical disc herniation, degenerative disc disease, or cervical spondylosis. The goal of this surgery is to stabilize the spine and relieve pain by promoting the fusion (joining together) of the adjacent vertebrae.
Cervical cage subsidence refers to the gradual sinking or settling of the implanted cage into the vertebral bodies.
Epidemiology
The epidemiology of cervical cage subsidence, or the incidence and prevalence of this condition, is an important aspect of understanding its occurrence and impact on patients. However, specific epidemiological data for cervical cage subsidence may not be as readily available as for more common spinal conditions or complications. Epidemiological information often relies on clinical studies, medical databases, and registries. Here are some key points about the epidemiology of cervical cage subsidence:
Incidence: The incidence of cervical cage subsidence can vary based on several factors, including the type of cage used, patient characteristics, and surgical techniques. Research studies have reported incidence rates ranging from less than 5% to over 20%, depending on the specific population and study design. It's important to note that cervical cage subsidence is generally considered a complication of cervical spine fusion procedures.
Risk Factors: Certain factors may increase the risk of cervical cage subsidence. These risk factors can include older age, female gender, smoking, osteoporosis or poor bone quality, and the use of smaller or improperly sized cages. The prevalence of these risk factors in a specific population can influence the overall epidemiology of cervical cage subsidence.
Imaging and Diagnosis: Cervical cage subsidence is typically diagnosed through imaging studies, such as X-rays, CT scans, or MRI scans. The epidemiology of cervical cage subsidence may be influenced by how frequently these diagnostic tests are performed postoperatively and how rigorously healthcare providers monitor patients for complications.
Surgical Techniques: The choice of surgical approach and techniques can impact the likelihood of cervical cage subsidence. Minimally invasive techniques and the use of additional fixation methods (such as plates and screws) may affect the incidence of subsidence, and this can vary between surgeons and institutions.
Long-term Follow-up: Understanding the long-term epidemiology of cervical cage subsidence requires extended follow-up of patients who have undergone cervical spine fusion. The occurrence of subsidence may become more evident as patients are monitored over several years.
Geographic and Healthcare System Variations: The epidemiology of cervical cage subsidence may vary by geographic location and healthcare system. Differences in patient populations, surgical practices, and access to healthcare can all influence the incidence and prevalence of this complication.
Research and Surveillance: Epidemiological data on cervical cage subsidence are likely to evolve as more research is conducted, and as healthcare systems establish surveillance mechanisms for monitoring surgical outcomes and complications. Long-term studies and registries may provide valuable insights into the epidemiology of this condition.
Given the relatively recent emergence of cervical cage subsidence as a recognized complication in spinal surgery and the variability in reporting and surveillance practices, more comprehensive and standardized epidemiological data may become available in the future. Healthcare providers and researchers continue to work on improving patient outcomes and reducing the risk of complications like cervical cage subsidence through evidence-based practices and ongoing research.
Classification
Mild and major cage subsidence was defined as ≤2 mm and >2 mm, respectively. The extent of cage subsidence was greater after Anterior cervical discectomy and fusion with cage alone. Cage subsidence occurred more often when the end plate was removed. Additional anterior plate fixation is recommended when the end plate is removed 1).
Subsidence in ACDF with cages occurs in 21% of patients. The risk for subsidence seems lower using PEEK or titanium cages or adding screws 2).
Zero profile anchored spacer (ROI-C) use resulted in a higher subsidence rate than conventional cage and plate construct (CPC) use in multi-segment ACDF procedures. The male sex, the use of ROI-C, operation in multiple segments, and over-distraction were the most significant factors associated with an increase in the risk of cage subsidence 3).
The greater the cage height, the greater the risk of cage subsidence in ACDF. Polyetheretherketone cages are superior to titanium cages for the maintenance of intervertebral height in cases where cage height is >5.5 mm 4)
Subsidence irrespective of the measurement technique or definition does not appear to have an impact on successful fusion and/or clinical outcomes. A validated definition and standard measurement technique for subsidence is needed to determine the actual incidence of subsidence and its impact on radiographic and clinical outcomes 5).
PEEK cages showed a high rate of secondary subsidence (32%) 6).
Titanium Wing cage-augmented ACDF was associated with comparatively good long-term results. Subsidence was present but did not cause clinical complications. Furthermore, radiological studies demonstrated that the physiological alignment of the cervical spine was preserved and a solid bone arthrodesis was present at 2 years after surgery 7).
There is evidence documenting relatively frequent complications in stand-alone cage assisted ACDF, such as cage subsidence and cervical kyphosis 8).
Subsidence irrespective of the measurement technique or definition does not appear to have an impact on successful fusion and/or clinical outcomes. A validated definition and standard measurement technique for subsidence is needed to determine the actual incidence of subsidence and its impact on radiographic and clinical outcomes 9).
Findings suggest that the value of ratio of anterior endplate more than 1.18, alignment of titanium mesh cage (TMC) and poor bone mineral density are the risk factors for subsidence. TMC subsidence does not negatively affect the clinical outcomes after operation. Avoiding over expansion of intervertebral height, optimizing placing of TMC and initiation of anti-osteoporosis treatments 6 months prior to surgery might help surgeons to reduce subsidence after ACCF 10).
Risk factors
Cervical cage subsidence is a complication associated with cervical spine fusion surgery, and several risk factors can increase the likelihood of this occurrence. Understanding these risk factors is essential for healthcare providers when evaluating patients for surgery and planning their treatment. Some of the key risk factors for cervical cage subsidence include:
Patient Age: Older patients are generally at a higher risk for cervical cage subsidence. As people age, their bone density tends to decrease, making the vertebral bodies less capable of supporting the implanted cage.
Osteoporosis or Poor Bone Quality: Patients with osteoporosis or compromised bone quality are at an increased risk of cage subsidence. Weakened bones have reduced structural integrity, making them more susceptible to sinking or collapsing around the cage.
Smoking: Smoking is known to negatively affect bone health and can contribute to reduced bone density. Smokers may have an elevated risk of cage subsidence compared to non-smokers.
Cage Size and Design: The choice of cage size and design is critical. Using a cage that is too small or has inadequate support structures can increase the risk of subsidence. Surgeons should carefully select and appropriately size the cage based on the patient's anatomy.
Inadequate Bone Preparation: Insufficient removal of the cartilage and bone at the implantation site can hinder proper cage placement and reduce the chances of successful fusion. Adequate preparation of the vertebral endplates is crucial.
Improper Surgical Technique: Surgical errors or complications during the procedure, such as excessive drilling or aggressive cage insertion, can lead to cage subsidence. Skilled surgical technique is essential for reducing the risk.
Cage Material: The type of material used in the cage can influence its subsidence risk. Cages made of materials with different biomechanical properties may interact differently with the surrounding bone.
Adjacent Level Disease: Patients with degeneration or pathology in adjacent cervical levels may be at increased risk of cage subsidence. This is because the altered biomechanics of the spine can affect load distribution and cage stability.
Postoperative Factors: Factors such as early postoperative mobilization, compliance with activity restrictions, and adherence to rehabilitation protocols can influence the risk of cage subsidence. Patients must follow postoperative instructions carefully to support proper healing and fusion.
Surgeon Experience: The experience and skill of the surgeon performing the procedure can impact the risk of complications, including cage subsidence. Surgeons with more experience in cervical spine surgery may be better equipped to minimize this risk.
It's essential for both patients and healthcare providers to thoroughly evaluate the individual risk factors for cervical cage subsidence when considering cervical spine fusion surgery. A comprehensive assessment can help in making informed decisions about surgical options and selecting the most appropriate treatment plan. Additionally, strategies to mitigate these risk factors, such as optimizing bone health before surgery or using additional fixation methods, may be considered to reduce the risk of cervical cage subsidence.
Lower cervical HU value indicates a higher risk of subsidence in patients following Zero-P fusion for single-level cervical spondylosis. HU values were better predictors of Zero-P subsidence than DXA T-scores. In addition, the measurement of HU value in the midsagittal, midcoronal, and midaxial planes of the cervical vertebral body provides an effective method for predicting Zero-P subsidence 11).
Surgeons can preoperatively assess bone quality using Dual-energy X-ray absorptiometry or computed tomography; however, this is not feasible for all patients. Recently, an MRI-based scoring system was used to evaluate the lumbar spine's vertebral bone quality.
To create a similar MRI-based scoring system for the cervical spine (C-VBQ), correlate C-VBQ scores with computed tomography-Hounsfield units (HU), and evaluate the utility of this scoring system to independently predict cage subsidence after single-level anterior cervical diskectomy and fusion (ACDF).
Demographic, procedure-related, and radiographic data were collected for patients. Pearson correlation test was used to determine the correlation between C-VBQ and HU. Cage subsidence was defined as ≥3 mm loss of fusion segmental height. A multivariate logistic regression model was built to determine the correlation between potential risk factors for subsidence.
Of 59 patients who underwent single-level ACDF, subsidence was found in 17 (28.8%). Mean C-VBQ scores were 2.22 ± 0.36 for no subsidence levels and 2.83 ± 0.38 (P < .001) for subsidence levels. On multivariate analysis, a higher C-VBQ score was significantly associated with subsidence (odds ratio = 1.85, 95% CI = 1.39-2.46, P < .001) and was the only significant independent predictor of subsidence after ACDF. There was a significant negative correlation between HU and C-VBQ (r2 = -0.49, P < .001).
Soliman et al. found that a higher C-VBQ score was significantly associated with cage subsidence after ACDF. Furthermore, there was a significant negative correlation between C-VBQ and HU. The C-VBQ score may be a valuable tool for assessing preoperative bone quality and independently predicting cage subsidence after ACDF 12).
Clinical features
Cervical cage subsidence is a complication that can occur after cervical spine fusion surgery, and it may be associated with various clinical features or symptoms. These clinical features can vary in severity and may include:
Neck Pain: One of the most common clinical features of cervical cage subsidence is neck pain. Patients may experience persistent or worsening pain in the neck region, which can be localized or radiate to the shoulders and upper back.
Dysphagia: Some patients may develop difficulty swallowing, a condition known as dysphagia. This can manifest as discomfort or a sensation of food getting stuck in the throat.
Neurological Symptoms: Depending on the extent and location of subsidence, cervical cage subsidence can compress nearby neural structures, such as nerve roots or the spinal cord. This compression can lead to neurological symptoms, which may include:
Radicular Pain: Pain radiating into the arms, shoulders, or hands due to nerve compression. Numbness and Tingling: Patients may experience numbness, tingling, or “pins and needles” sensations in the upper extremities. Weakness: Weakness in the arms, hands, or fingers can occur if nerve function is compromised. Coordination Problems: In severe cases, compression of the spinal cord may lead to coordination difficulties and gait disturbances. Loss of Range of Motion: Cervical cage subsidence can affect the flexibility and range of motion of the neck. Patients may notice limitations in their ability to turn or tilt their heads.
Worsening Symptoms Over Time: Clinical features of cervical cage subsidence may not become evident immediately after surgery. Instead, they may develop or worsen gradually over time as the cage sinks further into the vertebral bodies.
Imaging Abnormalities: Imaging studies, such as X-rays, CT scans, or MRI scans, can reveal the presence of cervical cage subsidence. Radiological findings, such as a decreased intervertebral height, cage migration or sinking, and changes in alignment, may be observed.
Difficulty Breathing (Rare): In rare cases, particularly if the subsidence is severe and causes significant compression of the spinal cord, patients may experience breathing difficulties. This is considered a medical emergency and requires immediate attention.
It's important to note that not all patients who experience cervical cage subsidence will develop noticeable symptoms or clinical features. Some cases may be asymptomatic and only detected through routine imaging. The presence and severity of clinical features can vary from patient to patient, and they are influenced by factors such as the degree of subsidence, the presence of neural compression, and individual patient characteristics.
If a patient who has undergone cervical spine fusion surgery experiences persistent or worsening neck pain, neurological symptoms, or difficulty swallowing, they should seek medical evaluation promptly. Diagnostic imaging and clinical assessment by a healthcare provider will help determine the cause of these symptoms, including the possibility of cervical cage subsidence, and guide appropriate treatment decisions.
This subsidence can lead to several problems, including:
Loss of Height: As the cage sinks into the vertebral bodies, it may lead to a reduction in the height of the intervertebral space. This loss of height can result in changes to the alignment and curvature of the spine, potentially causing neck pain and neurological symptoms.
Failed Fusion: Cervical cage subsidence can hinder the process of bone fusion between the vertebrae, which is essential for the long-term success of the surgery. When fusion fails to occur, it can result in instability and ongoing pain.
Neurological Compression: If the sinking cage puts pressure on nearby nerve roots or the spinal cord, it can cause neurological symptoms such as numbness, weakness, or pain in the arms, hands, or fingers.
Diagnosis
Diagnosing cervical cage subsidence typically involves a combination of clinical evaluation and radiological imaging studies. Here's how the diagnosis of cervical cage subsidence is typically conducted:
Clinical Evaluation: The process often begins with a thorough clinical evaluation by a healthcare provider. This may include taking a detailed medical history, discussing the patient's symptoms, and performing a physical examination. During the examination, the healthcare provider may assess the patient's neck mobility, strength, reflexes, and any signs of neurological deficits.
Symptom Assessment: The healthcare provider will inquire about the patient's symptoms, including neck pain, difficulty swallowing, radiating arm pain, numbness, tingling, weakness, and any other relevant complaints. It's essential for the patient to provide a detailed description of the symptoms and their progression.
Imaging Studies: Imaging studies play a crucial role in diagnosing cervical cage subsidence. Several types of imaging modalities may be used:
X-rays: X-rays are often the initial imaging modality used to assess the cervical spine. They can reveal changes in the alignment of vertebral bodies, a decrease in intervertebral space, and the position of the cervical cage.
CT Scan (Computed Tomography): CT scans provide detailed cross-sectional images of the spine and are useful for assessing the extent and location of cage subsidence. CT scans can also help identify any bony changes or fractures associated with subsidence.
MRI (Magnetic Resonance Imaging): An MRI may be ordered if there are concerns about neural compression or spinal cord involvement. MRI can visualize soft tissues, including the spinal cord and nerve roots, and help assess the impact of subsidence on these structures.
Comparison with Preoperative Imaging: Comparing the current imaging findings with preoperative imaging, such as preoperative X-rays or CT scans, can be valuable in confirming the presence of cage subsidence. This comparison helps differentiate between expected postoperative changes and complications like subsidence.
Consultation with Specialists: In cases where there is neurological involvement or uncertainty about the diagnosis, a neurosurgeon or spine specialist may be consulted for their expertise in interpreting imaging findings and assessing the need for surgical intervention.
Monitoring: In some cases, patients who have radiographic evidence of cage subsidence may not exhibit significant clinical symptoms. In such instances, the healthcare provider may choose to monitor the patient's condition over time to assess whether symptoms develop or worsen.
Once cervical cage subsidence is diagnosed, treatment options can be considered, which may include conservative management (e.g., physical therapy, pain management) or surgical intervention to address the subsidence and its associated symptoms. The appropriate course of action will depend on the individual patient's clinical presentation, the extent of subsidence, and other factors. Early diagnosis and intervention can help prevent further complications and improve the patient's outcome.
Treatment
The treatment of cervical cage subsidence depends on various factors, including the severity of the subsidence, the presence of symptoms, and the patient's overall health. Treatment options can range from conservative (non-surgical) approaches to surgical intervention. Here are the primary treatment options for cervical cage subsidence:
Conservative Management:
Observation: In cases where cervical cage subsidence is detected but is not causing significant symptoms or neurological deficits, the healthcare provider may choose to monitor the patient's condition over time with regular follow-up appointments and imaging studies.
Pain Management: For patients with mild to moderate neck pain, over-the-counter pain medications or prescription pain relievers may be prescribed to manage discomfort.
Physical Therapy: Physical therapy may be recommended to improve neck strength, range of motion, and posture. Therapists can also teach exercises and techniques to alleviate pain and discomfort.
Cervical Collar: A cervical collar or neck brace may be temporarily worn to immobilize the neck and provide support. This can help reduce strain on the affected area and alleviate pain.
Surgical Intervention:
Cage Revision or Replacement: In cases where cervical cage subsidence is causing significant pain or neurological symptoms, surgical revision or replacement of the cage may be necessary. During this procedure, the existing cage is removed, and a new cage of an appropriate size and design may be implanted. Additional fixation methods, such as plates and screws, may also be used to enhance stability.
Fusion Extension: In some instances, the fusion may need to be extended to adjacent levels to provide better stability and support. This involves the placement of additional cages and the fusion of adjacent vertebrae.
Decompression: If cervical cage subsidence has resulted in significant compression of the spinal cord or nerve roots, a decompressive procedure may be required. This can involve removing portions of bone or tissue that are compressing neural structures to relieve pressure.
Revision Surgery Considerations: Revision surgery can be more complex and challenging than the initial procedure. Patients and surgeons must carefully consider the risks and benefits of revision surgery and discuss the best approach based on the patient's specific circumstances.
Prevention
Several factors can contribute to cervical cage subsidence, including:
Inadequate cage sizing: Using a cage that is too small for the intervertebral space can increase the risk of subsidence.
Inadequate bone preparation: Insufficient removal of the cartilage and bone at the implantation site can hinder proper cage placement.
Insufficient bone quality: Poor bone quality, often seen in patients with osteoporosis, may make the surrounding bone less able to support the cage.
Improper surgical technique: Surgical errors or complications during the procedure can lead to cage subsidence.
To prevent cervical cage subsidence and its associated complications, surgeons take several precautions, including careful patient selection, proper sizing of the cage, meticulous surgical technique, and the use of additional fixation techniques (such as plates and screws) to enhance stability. Postoperative follow-up and rehabilitation are also crucial to monitor the fusion progress and address any issues promptly.
It's essential for patients considering cervical fusion surgery to discuss the risks and benefits of the procedure with their healthcare provider and to follow postoperative instructions closely to minimize the risk of complications like cervical cage subsidence.
A loss of global cervical lordosis and lordosis at the instrumented cervical segment is documented during follow-up in patients treated by ACDF with stand-alone cages, compared with patients treated by ACDF with cages and plates, and this could be related to a higher index of subsidence 13)
During the process of bone remodeling, settlement of the cage of less than 2 mm into the vertebral bodies until fusion is to be expected 14)
If cages subside >3 mm into the vertebral body, disc space and neural foramina heights both collapse 15) 16)
Subsidence is reported in 9.3% to 62.5% of cervical segments analyzed, it often occurs within 3 months after surgery and results in sagittal misalignment in most cases 17) with segmental loss of angulation as high as 8.7°. Clinical adjacent segment pathology may affect 9% to 25% of all patients within 10 years after an anterior cervical arthrodesis, and risk factors include pre-existing degeneration at the adjacent levels, previous cervical fusion, and sagittal cervical misalignment 18) 19) 20)
Research
A study of Lin et al. compares four cervical endplate removal procedures, validated by finite element models.
To characterize the effect of biomechanical strength and increased contact area on the maximum von Mises stress, migration, and subsidence between the cancellous bone, endplate, and implanted cage.
Anterior cervical discectomy and fusion (ACDF) has been widely used for treating patients with degenerative spondylosis. However, no direct correlations have been drawn that incorporate the impact of the contact area between the cage and the vertebra/endplate.
Model 1 (M1) was an intact C2C6 model with a 0.5 mm endplate. In model 2 (M2), a cage was implanted after removal of the C4-C5 and C5-C6 discs with preservation of the osseous endplate. In model 3 (M3), 1 mm of the osseous endplate was removed at the upper endplate. Model 4 (M4) resembles M3, except that 3 mm of the osseous endplate was removed.
The range of motion (ROM) at C2C6 in the M2-M4 models was reduced by at least 9º compared to the M1 model. The von Mises stress results in the C2C3 and C3C4 interbody discs were significantly smaller in the M1 model and slightly increased in the M2-M3 and M3-M4 models. Migration and subsidence decreased from the M2-M3 model, whereas further endplate removal increased the migration and subsidence as shown in the transition from M3 to M4.
The M3 model had the least subsidence and migration. The ROM was higher in the M3 model than the M2 and M4 models. Endplate preparation created small stress differences in the healthy intervertebral discs above the ACDF site. A 1 mm embedding depth created the best balance of mechanical strength and contact area, resulting in the most favorable stability of the construct 21).
Case series
2021
Lee et al. from Yangsan retrospectively reviewed the medical records of 40 patients who underwent stand-alone single-level ACDF using a polyetheretherketone (PEEK) cage between January 2012 and December 2018. The study population comprised 19 male and 21 female patients aged 24-70 years. The minimum follow-up period was 1 year. Twenty-seven patients had preoperative bone mineral density (BMD) data on dual-energy X-ray absorptiometry. Clinical parameters included sex, age, body mass index, smoking history, and prior medical history. Radiologic parameters included the C2-7 cobb angle, segmental angle, sagittal vertical axis, disc height, and total intervertebral height (TIH) at the preoperative and postoperative periods. Cage decrement was defined as the reduction in TIH at the 6-month follow-up compared to preoperative TIH. To evaluate the bone quality, Hounsfield unit (HU) value was calculated in the axial and sagittal images of conventional computed tomography.
Lumbar BMD values and cervical HU values were significantly correlated (r=0.733, p<0.001). They divided the patients into two groups based on cage decrement, and 47.5% of the total patients were regarded as cage decrement. There were statistically significant differences in the parameters of measuring the HU value of the vertebra and intraoperative distraction between the two groups. Using these identified factors, we performed a receiver operating characteristic (ROC) curve analysis. Based on the ROC curve, the cut-off point was 530 at the HU value of the upper cortical and cancellous vertebrae (p=0.014; area under the curve [AUC], 0.727; sensitivity, 94.7%; specificity, 42.9%) and 22.41 at intraoperative distraction (p=0.017; AUC, 0.722; sensitivity, 85.7%; specificity, 57.9%). Using this value, they converted these parameters into a bifurcated variable and assessed the multinomial regression analysis to evaluate the risk factors for cage decrement in ACDF. Intraoperative distraction and HU value of the upper vertebral body were independent factors of postoperative subsidence.
Insufficient intraoperative distraction and low Hounsfield unit (HU) value showed a strong relationship with postoperative intervertebral height reduction following single stand-alone PEEK cage ACDF 22).
2017
Mende et al. performed a retrospective analysis of ACDF patients from 2004 to 2010. Numeric analog scale (NAS) score pre-op and post-op, Oswestry Disability Index (ODI) on x-rays, endplate (EP) and cage dimensions, implant position, lordotic/kyphotic subsidence patterns (>5°), and Cervical spine alignment were recorded. Subsidence was defined as height loss >40%. Patients were grouped into single segment (SS), double segment (DS), and plated procedures. We included 214 patients. Prevalence of subsidence was 44.9% overall, 40.9% for SS, and 54.8% for DS. Subsidence presented mostly for dorsal (40.7%) and mid-endplate position (46.3%, p < 0.01); dorsal placement resulted in kyphotic (73.7%) and central placement in balanced implant migration (53.3%, p < 0.01). Larger cages (>65% EP) showed less subsidence (64.6 vs. 35.4%, p < 0.01). There was no impact of subsidence on ODI or alignment. NAS was better for subsided implants in SS (p = 0.06). Cages should be placed at the anterior endplate rim in order to reduce the risk of subsidence. Spacers should be adequately sized for the respective segment measuring at least 65% of the segment dimensions. The cage frame should not rest on the vulnerable central endplate. For multilevel surgery, ventral plating may be beneficial regarding construct stability. The reduction of micro-instability or over-distraction may explain lower NAS for subsided implants 23).
2014
a retrospective observational cohort study to test the hypothesis that radiographic subsidence of cervical cages is not associated with adverse clinical outcomes. 33 cervical segments were treated surgically by ACDF with stand-alone cage in 17 patients (11 female, 6 male), mean age 56 years (33-82 years), and re-examined after eight and twenty-six months (mean) by means of radiology and score assessment (Medical Outcomes Study Short Form (MOS-SF 36), Oswestry Neck Disability Index (ONDI), painDETECT questionnaire and the visual analogue scale (VAS)).
Results: Subsidence was observed in 50.5% of segments (18/33) and 70.6% of patients (12/17). 36.3% of cases of subsidence (12/33) were observed after eight months during mean time of follow-up 1. After 26 months during mean time of follow-up 2, full radiographic fusion was seen in 100%. MOS-SF 36, ONDI and VAS did not show any significant difference between cases with and without subsidence in the two-sample t-test. Only in one type of scoring (painDETECT questionnaire) did a statistically significant difference in t-Test emerge between the two groups (p = 0.03; α = 0.05). However, preoperative painDETECT score differ significantly between patients with subsidence (13.3 falling to 12.6) and patients without subsidence (7.8 dropped to 6.3).
Conclusions: The radiological findings indicated 100% healing after stand-alone treatment with ACDF. Subsidence occurred in 50% of the segments treated. No impact on the clinical results was detected in the medium-term study period 24).