The diagnosis of cervical degenerative disease was once referred to generically as cervical spondylosis and was also widely used by clinicians. However, the concept of cervical spondylosis is rather ambiguous and often conflates various cervical spine disorders, such as cervical disc herniation, cervical disc prolapse, and vertebral segment hypertrophy. With the improvement of CT and MRI diagnostic techniques, the understanding of cervical spondylosis has become more and more profound, and the pathological changes and clinical features of cervical spondylosis have become more profound. In recent years, it has been recognized that cervical disc herniation and cervical spinal stenosis with clinical symptoms are independent disorders. In order to better facilitate readers’ clear understanding of cervical spondylosis, I will discuss some views on the diagnosis and treatment of multisegmental crestal cervical spondylosis by combining my own clinical experience.
I. The concept of multisegmental crestal cervical spondylosis
Multi-segmental cervical spondylosis refers to the presence of degenerative lesions of the cervical spine in three or more consecutive or discontinuous segments, including vertebral osteophytes, ligamentous hypertrophy and calcification, disc degeneration and herniation, etc., which compress the crestal medulla and nerves and produce the corresponding clinical symptoms. If it is necessary to classify cremasteric cervical spondylosis by the number of segments, I think it is more appropriate to differentiate cervical spondylosis into: single segment, double segment (continuous type, jumping type) and multi-segment (≥3 segments).
Relationship between multisegmental crestal cervical spondylosis and cervical spinal stenosis
In the 2nd National Symposium on Cervical Spondylosis in China, the typology of cervical spondylosis was unified, and developmental cervical spinal stenosis and cervical disc herniation, which were originally listed as cervical spondylosis, were classified as separate diseases. According to the definition of the symposium, cervical spondylosis refers to degenerative changes in the cervical disc tissue and its secondary pathology involving the surrounding tissue structures (nerve roots, cremaster, vertebral artery, sympathetic nerve, etc.), with clinical manifestations corresponding to the imaging changes.
This definition contains four basic elements.
(1) degeneration of the cervical discs or degeneration of the intervertebral joints.
(2) Involvement of the surrounding tissues.
(3) The presence of corresponding clinical manifestations.
(4) corresponding imaging changes.
Currently, cervical spondylosis and degenerative cervical stenosis are often confused with each other in clinical practice in terms of diagnostic names. Cervical spinal stenosis in the narrow sense, so-called primary spinal stenosis, is caused by both congenital and developmental factors. Cervical spinal stenosis in the broader sense encompasses all pathological changes that cause small spinal canal diameters, including cervical spondylosis, i.e., acquired cervical spinal stenosis, and has different pathological types, including degenerative cervical spinal stenosis, metabolic abnormalities, medical factors, and trauma. Degenerative cervical spinal stenosis is the most important cause of acquired secondary cervical spinal stenosis, which is mainly caused by secondary cervical spinal stenosis based on the degeneration of the cervical spine, hyperplasia of the posterior edge of the cervical vertebral body, hypertrophy of the posterior cervical synovial joint, hypertrophy of the joint capsule, hyperplasia and hypertrophy of the posterior longitudinal ligament and the yellow ligament. In the diagnostic classification of cervical degenerative diseases of the water pool, the main part of what used to be cervical spondylosis is named degenerative cervical spinal stenosis, that is, the degenerative volume increase of the cervical spine related tissues leading to the narrowing of the spinal canal or nerve root canal and the appearance of nerve compression symptoms, which is clearer than before and overcomes the generalized concept of cervical spondylosis. However, the method of this diagnostic classification has not yet been recognized by most experts as an industry consensus, and it is necessary to organize extensive discussions to reach a consensus.
III. How to determine whether it is multi-segmental crestal myelopathy cervical spondylosis
From the definition of cervical spondylosis, the diagnosis of cervical spondylosis must include two aspects: on the one hand, the presence of cremaster neurological compression on imaging, and on the other hand, the presence of the corresponding clinical manifestations. The following three points should be noted.
(1) Clinical manifestations and signs of cervical medullary compression.
(2) The imaging examination, especially MRI, should be consistent with the clinical manifestations.
(3) Diseases such as cremasterolateral sclerosis, intradural tumor, and peripheral neuritis must be excluded, especially cremasterolateral sclerosis, which has a completely different etiology, pathogenesis, course, and prognosis from CSM. This clearly demonstrates that the presence of imaging compression alone, without causing corresponding clinical symptoms is not diagnostic of cervical spondylosis.
The following diagnostic principles must be met to establish the diagnosis of cervical spondylosis.
(1) Clinical manifestations (i.e., symptoms and signs) of cervical spondylosis are present.
(2) Imaging demonstrates degenerative changes in the cervical discs or intervertebral joints.
(3) The imaging signs can explain the clinical manifestations.
In contrast, it is very common for imaging of multisegmental disc herniation in the elderly to cause dural sac compression, and whether this causes clinical symptoms is difficult to determine with the current technology. The segment with compression with abnormal crestal medullary signal is often the responsible segment, but the absence of altered crestal medullary signal can be ruled out? The answer is no. Does the fact that cervical degeneration is mild and crestal medullary compression is not evident on imaging mean that no significant neurological symptoms will occur?
Again, it is not certain; does the presence of compression necessarily cause clinical symptoms? The fact is that not all bony bulges and degenerative herniated discs produce clinical symptoms. It is possible, but not absolute, that imaging may have an impact on the local structures of the cervical spine. Some patients have very severe imaging but mild clinical manifestations, while others have less severe cervical degeneration but early and severe symptoms. One of the main reasons for this is that the size of the actual diameter of the cervical spinal canal is one of the main factors in determining the early or late appearance of neurological symptoms. It is the presence of these aspects of difficulty that causes confusion in clinical diagnosis and the expansion of the scope of surgery.
Fourth, the concept of prophylactic decompression is undesirable to avoid the expansion of the scope of surgery
The scope of decompression should not depend solely on imaging, but should be based on clinical manifestations, i.e., the removal of pressure-causing factors that cause clinical symptoms. In the case of multisegmental degeneration, the principle of “decompression should be performed wherever there is compression” should not be followed, as not all bony and degenerated discs produce clinical symptoms. In recent years, both in the professional literature and in clinical practice, it is not uncommon to see cases with no significant compression on MRI and only disc degeneration being decompressed prophylactically, which is clearly inappropriate. Cervical degeneration is a cycle of “stability – instability – re-stability”. In some individuals, pathologic changes can stagnate or even end at a certain stage of development for a long time, and even mild clinical symptoms may resolve on their own and remain stable for a long time. Decompression of a non-responsible segment that is degenerative on imaging but not yet symptomatic, or even decompression and fusion of a normal disc, not only deprives the patient of an opportunity for self-healing, but also exposes him to the potential risk of surgical complications. Blindly expanding the scope of decompression makes the shear force of the entire cervical spine activity concentrated on the few discs in the adjacent segments that already have pathological changes such as degeneration and instability, and it is indisputable that the stress on the adjacent segments increases after surgery, accelerating their degeneration process. The longer the fused segment, the lower the fusion rate of bone graft. The possibility of non-fusion of bone graft increases with anterior multi-segmental subtotal resection. Therefore, the responsible segment should be clearly defined before surgery, and precise decompression should be performed to avoid the expansion of the operation.
V. The choice of surgical approach should be individualized
In view of the advantages and shortcomings of the anterior and posterior approaches and the highly variable conditions of patients, the selection of the approach should be individualized. The advantages of the anterolateral approach are direct decompression, better long-term results, restoration of physiological curvature and intervertebral height, and reduction of axial pain. Disadvantages include relatively high risk and a high rate of nonunion after multi-segment subtotal vertebral dissection. The posterior approach is relatively low-risk, with a low percentage of nonfusion. However, the most significant disadvantages of the procedure are its indirect decompression and poor long-term outcome; and the high number of complications (e.g., axial pain, posterior convexity deformity, C5 radiculopathy).
Recent research and clinical trends prefer anterior surgery with better anterior nerve function improvement, and when anterior surgery is chosen, surgery-related complications and the possibility of reoperation should be considered as well, because it is a multisegmental case, and decompression and fusion across multiple segments increases the difficulty of surgery and the risk of nonfusion, leading to pseudarthrosis formation, breakage or displacement of the built-in, loss of mobility and degeneration of adjacent segments Complications have led to the emergence of several improved procedures. The advent of these procedures has reduced the complications associated with them, but they still have drawbacks. It is wise to use an individualized plan for each case.
Sixth, combined anterior and posterior decompression is not necessary in most cases
Combined anterior and posterior decompression necessarily carries the potential risk of increased surgical complications. Posterior surgery is indicated for lesions of more than 4 segments, combined with severe spinal stenosis, or in cases where there is clear compression of the posterior approach such as ossification of the ligamentum flavum. Posterior spinal canal enlargement can effectively expand the volume of the spinal canal, directly relieving the posterior compression of the cremaster, and indirectly relieving the anterior compression of the cremaster because of the posterior displacement of the cremaster. However, in patients with severe anterior compression of the crestal medulla, the limited posterior displacement of the crestal medulla during posterior surgery cannot effectively relieve the anterior compression of the crestal medulla, so combined anterior decompression is particularly necessary.
For “high-risk cervical spondylosis”, simple anterior surgery is very risky and easy to damage the crestal medulla, so posterior surgery is usually performed first to posteriorly shift the crestal medulla, increase the space in front of the crestal medulla, reduce the pressure in the spinal canal, reduce venous plexus stasis, and help improve the blood flow to the crestal medulla. Theoretically, the possibility of crural injury is reduced.
In patients with cervical spondylolisthesis, except for extensive decompression by combined anterior and posterior approaches and in isolated cases, internal fixation on one side is sufficient to meet the need for fusion without simultaneous anterior and posterior fixation. If a solid bony fusion has been obtained with anterior surgery, there is no need for internal fixation when decompression is performed again with posterior surgery. The misuse of internal fixation not only increases the economic burden of patients, but also increases the incidence of degeneration of adjacent segments.
Seven, anterior surgery methods are numerous, should follow the simple not complicated
The exact cause of adjacent segment degeneration is still unknown, but it may be related to strong internal fixation, too many fixed segments and other factors. The longer the fused segment, the lower the fusion rate of bone graft. The likelihood of non-fusion of bone grafting increases with anterior multi-segmental subtotal resection for multi-segmental cervical spondylolisthesis. The incidence of implant nonunion can be reduced and postoperative stability can be improved by designing the surgical plan with segmental decompression, using one subtotal laminectomy plus one or two interbody decompressions, rather than multiple subtotal laminectomies. Accurate diagnosis, clear responsibility gap, simple but not complicated selection of operation style and reasonable design of fusion range are necessary to improve the treatment effect of multisegmental cervical spondylosis, reduce complications and improve safety.
VIII. Problems and outlook
Clinical confusion of cervical spondylosis and degenerative cervical spinal stenosis with each other in diagnostic names also exists frequently. The prevalence of multisegmental cervical degeneration in imaging of the elderly and the discrepancy between imaging and symptoms cause difficulties in determining the number of responsible segments, further leading to confusion in clinical diagnosis, expansion of the scope of surgery, and diversification of surgical methods. The determination of surgical segments should rely on a comprehensive analysis of 3 aspects: clinical, imaging and electrophysiological.
The concept of preventive decompression by imaging alone is not desirable. The choice of surgical approach for crestal cervical spondylosis, especially the anterior-posterior approach, has been the focus of controversy. The choice of surgical approach depends on a variety of factors, such as the compressor, the number of segments involved, the sagittal sequence of the cervical spine, and the patient’s own condition, and the surgeon’s proficiency and preference for each surgical technique is also an important factor in the surgical strategy. There is a lack of high-quality evidence to guide the choice of surgical approach. However, many studies have confirmed that good clinical outcomes can often be achieved by anterior or posterior surgery alone, and that combined posterior-anterior decompression necessarily carries a potential risk of increased surgical complications, which is unnecessary in most cases, so the choice of surgical approach should be individualized. It is urgent to clarify the concept of multisegmental crestal cervical spondylosis, standardize surgical treatment methods, and form a consensus knowledge, but the main drawback of the current study design is the lack of randomization, and the selection of cases is greatly influenced by human factors, which can easily produce biased results and reduce the credibility.