Lumbar spondylolisthesis refers to the partial or complete slippage of the upper vertebrae on the surface of the lower vertebrae due to abnormal bony connections between the lumbar vertebrae. If the affected vertebra slips forward due to bilateral arch collapse, it is called true slippage. If there is no isthmus breakdown but rather a degenerative disc or synovial osteoarthropathy that causes a change in the relationship between the synapses, the slippage is called a pseudosynovia.
Spondylolisthesis is a combination of the Greek words Spondylo (vertebral body) and Listheheis (slip), indicating a forward slip of the superior vertebral body on top of the inferior vertebrae, and has been known for more than 200 years. Until the middle of the 19th century, it was thought that spinal slippage was due to obesity causing the slippage of the L5 on the sacrum. 1854 was the year when the German physician Kilian first proposed and described spinal slippage. The following year Robert found through anatomical studies of the lumbosacral region that if the posterior arch of the L5 was intact, slippage would not occur, and if the posterior arch of the L5 was severed, the L5 would slide freely. 1882 Neugebauer concluded that slippage could be congenital or acquired. The L5 can also slip forward if there is no defect in the intercommissural area but there is elongation. However, he did not suggest whether the slippage was due to fracture or local weakness of the lumbar isthmus. Yang Cao, Department of Orthopedics, Wuhan Union Medical College Hospital
I Classification
Newman and Stone first classified vertebral slippage by analyzing 319 cases over 15 years, and Wiltse classified vertebral slippage into five types according to etiology on this basis, which was recognized by the International Society for the Study of the Lumbar Spine. As shown in Table 16-1
Table 16-1 WILTSE classification of vertebral slippage
Type I:dysplastic
Type II:Isthmic. Lumbar isthmus defect
Type IIA: Lumbar isthmus stress fracture
IIB: Lumbar isthmus lengthened but still intact without fracture
Type IIC: Acute fracture of the lumbar isthmus
Type III:Degenerative slippage – persistent lower back instability due to prolonged standing
Type IV:traumatic slippage – acute fracture of the posterior structures near the lumbar isthmus
Type V:pathological slippage – destruction of posterior spinal structures due to systemic or local bone lesions
This classification is somewhat limited in that it is based on mixed etiologic and imaging criteria and does not include the increasing number of postoperative slippages.
A new classification of spinal slippage was proposed by Marchetti and Bartolozzi in 1982 and revised in 1994. This method did not place isthmus as the most important factor, but rather developmental and dysplastic spondylolisthesis as the primary factor. As shown in Table 16-2
Table 16-2 Marchetti-Bartolozzi classification of spinal slippage
A Developmental B Acquired
Highly dysplastic Traumatic
With isthmus fracture Acute fracture
With isthmus lengthening Stress fracture
Hypoplastic Post-operative
With isthmus fracture Direct surgery
With isthmus lengthening Indirect surgery
Pathological
Local lesion
Systemic disease
Degenerative
primary
Secondary
II Epidemiology
The prevalence of lumbar spondylolisthesis is generally considered to be about 5% and may vary by age, regional ethnicity, occupation, and gender. The incidence of isthmic spondylolisthesis with or without spondylolisthesis has been reported to be 4.4% at age 6 years, increasing to 6% at age 18 years. The incidence of spondylolisthesis in adults appears to be relatively stable at about 6.0% The increase in incidence after the age of 40 years (especially in patients over 40 to 50 years) is associated with degeneration. The incidence of slipped isthmus in European and American whites is 4-6%, in blacks 1-3%, and in Eskimos it can be as high as 40-50%. However, a study by Eisenstein on South African skeletons found an incidence of 3.5%, with no racial or gender differences. VITRA et al. studied 1100 Finns aged 45-64 years, and the incidence was 7.7% in men and 4.6% in women. Rosenberg found that DS was 4-6 times more common in women than in men, and 3 times more common in blacks than in whites. Our scholar Ren Yuheng found a total incidence of 20.7% in famous athletes, especially for volleyball acrobatics.
Three etiology
The cause of lumbar spondylolisthesis is still not very clear, and the views of various schools are not consistent, including the following doctrines in summary.
1 congenital theory Some people propose that when two ossification centers of one vertebral arch do not heal or when an ossification center splits into two, the vertebral arch can form a collapse, but so far there is not enough embryological and anatomical evidence. The congenital developmental malformations and local structural weaknesses of the lumbar spine are of special etiologic significance. Clinically, it has been found that when the vertebral arch develops elongated, local fractures are likely to occur. Genetic factors are thought to be an important cause of isthmic fractures. It has been demonstrated that there are racial and gender differences in the incidence of lumbar isthmic fractures. Backer reported that three father-son pairs out of 400 students and their parents had a concurrent arch fracture, and Scott suggested that hereditary spondylolisthesis is mostly an autosomal abnormality.
2 Trauma theory Currently, most scholars believe that the disease is acquired and is clearly related to trauma and strain. Many studies have shown that acquired isthmic cleft lumbar spondylolisthesis is due to fatigue fractures of the lumbar isthmus. Although the neural arch can withstand great strength, in vivo and ex vivo experiments have shown that repeated loading can lead to fractures of the lumbar isthmus. Although a single severe injury can cause an acute fracture, the usual mechanism of occurrence is repetitive stress. Therefore, athletes have a higher incidence of isthmic fractures.
3 The mixed theory of isthmus developmental disorder and trauma suggests that the local structure of the isthmus is weak and that trauma predisposes to isthmus fracture.
In summary, it is believed that the arch rupture is caused by a variety of factors, but it is generally believed to be caused by repeated stresses on the interarticular processes based on genetic dysplasia. Degeneration of the intervertebral disc leads to narrowing of the intervertebral space and further development of degenerative changes in the small joints and weakening of the soft tissue support structures, resulting in degenerative slippage.
VI Clinical symptoms and signs
Low back pain is the most common clinical manifestation of lumbar spondylolisthesis, which may be accompanied by radicular pain. In mild slippage, the lumbar column movement is slightly restricted and the gait is basically normal. When the degree of slippage increases, the paravertebral muscles spasm, the lumbar activities are restricted, and the lumbar region may appear step-like changes. In severe slippage, physical examination reveals increased lumbar lordosis, shortened trunk, anterior abdominal crease, external hip rotation, heart-shaped hips, and a characteristic waddling gait, which Thalen and Dickson attribute to deformity and N cord tension. If the sacral nerve is displaced or compressed at the top of the sacrum, the patient may experience urinary and fecal dysfunction, but this is less common. Spondylolisthesis in children is different from that in adults, and further spondylolisthesis must be noted during the patient’s growth period.
VII Imaging
Radiographs are the preferred method of diagnosing spondylolisthesis. Anteroposterior radiographs generally do not easily show slippage, but in severe slippage, they show the characteristic inverted Napoleon cap sign, which is due to heavy forward slippage of the L5 vertebral body, and the radiograph is an axial projection of the L5 vertebral body. Standing and weight-bearing radiographs can increase the degree of slippage and the manifestation of slippage, suggesting the presence of lumbar instability. Ferguson’s position can show the lumbosacral junction and the area between the sacral wing of the L5 transverse process and these structures.Meyerding divided the supra-sacral articular surface into four equal parts and classified the slippage into four degrees according to the degree of forward slippage of L5 on the sacrum. I° is 0% to 25%; II° 25% to 50%; III° 50% to 75%; and IV° >75%. If >100%, it is called spinal detachment. newman improved on this, indicating both the degree of slippage and the degree of rotation of L5. boxall used the percentage of anterior displacement on the anterior-posterior diameter of the inferior vertebral body to describe the percentage of slippage. wiltse used sacral tilt, slippage angle and sacral horizontal angle, etc. Sacral tilt refers to the relationship of the sacrum to the vertical plane, and in progressive slippage, this angle becomes smaller. Sagittal rotation refers to the angular relationship between the sacrum and L5, also known as lumbosacral posterior convexity angle, which increases with progressive slippage. The horizontal angle of sacrum refers to the angular relationship between the upper edge of the sacrum and the horizontal plane, and this angle decreases when there is progressive slippage.
MRI can observe the degree of degeneration of the lower lumbar nerve roots and the L4L5 disc, which can help to determine the extent of the fused segment. If there is degeneration of the L4L5 disc, the segment should be fused together. ct scan has little diagnostic significance, and CMT can provide more information in older patients with multiple planes of degeneration. splect has high sensitivity and specificity in patients with painful isthmic fissures and isthmic fissures.
VIII Treatment
The treatment of synostosis is controversial and there are many options. Most patients are effective with conservative treatment, while a few require surgical treatment.
(i) Non-surgical treatment
For patients with mild lumbar spondylolisthesis who exhibit acute or chronic lower back pain, non-operative treatment should be performed first. Including rest, physical therapy, traction, lumbar back muscle exercise, massage and lumbar circumference protection, etc. to reduce symptoms and prevent the progress of slippage. It has been reported that very good results have been achieved. Especially in children and adolescents with simple arch collapse. In acute isthmus fractures, if diagnosed early, most of them can heal on their own by braking. This method can be used in elderly patients.
(ii) Surgical treatment
The purpose of surgery is to relieve pain, correct spinal deformity, relieve nerve compression, and enhance lumbar stability.
Indications for surgery include:
(1) Adolescents with no or symptomatic slippage greater than 50% and in the growth phase.
(2) Those with progressive slippage.
(3) Non-surgical treatment cannot correct spinal deformity and obvious gait abnormalities.
(4) The pain cannot be relieved by non-surgical treatment.
(5) Neurological symptoms or cauda equina compression syndrome in the lower extremities.
There are many surgical methods, including laminectomy and decompression, direct repair of the isthmus with internal fixation, spinal fusion and internal fixation.
1 Laminectomy decompression: suitable for those with nerve root or cauda equina compression and combined disc herniation. The vertebral arch prevents the vertebral body from slipping forward and plays a supporting role for the spine. However, after removal of the free arch, the spine will slide further. Therefore, when the arch is removed, fusion should be performed at the same time.
2. Internal fixation with direct repair of the isthmus with bone grafting: direct repair of bone grafting at the site of isthmus defect is suitable for young adults with symptomatic vertebral arch collapse or collapse and slip within Ⅰ°. The advantage of this procedure is that it restores the normal anatomy of the lumbar spine and causes less damage to its structure and function, but it is not suitable for elderly people with significant degeneration of the lumbar spine.
3 Lumbar fusion: There are many methods of spinal fusion, which can be divided into posterior interlaminar bone grafting, direct bone grafting for isthmic discontinuity, lateral and posterior intertransverse process bone grafting fusion and anterior or posterior intervertebral body bone grafting, etc.
(1) Posterior interlaminar fusion Posterior interlaminar fusion, with a high incidence of pseudoarthrosis, is rarely used.
(2) Lateral posterior fusion The main point is intertransverse bone grafting, and in some cases it is necessary to fuse small joints at the same time. This method can achieve a high rate of fusion. Its advantages are: (1) decompression surgery can be performed at the same time; (2) the bone grafting site is closer to the flexion-extension axis of the lumbar spine, which is rich in blood flow around it and facilitates bone healing; (3) the postoperative bed rest time is relatively short. Intertransverse fusion is particularly meaningful for spondylolisthesis, and can be used to stabilize the spine after extensive posterior decompression and foraminotomy. However, a high incidence of pseudarthrosis and unstable implant fusion have been reported for this method.
(3) Interbody fusion can be done via anterior or posterior approach. Since the vertebral body and disc bear most of the load of the lumbar spine, interbody fusion will provide higher stability of the lumbar spine, and the larger contact surface between the vertebral bodies also provides a more ideal bone graft bed. Anterior interbody fusion is divided into two approaches: transabdominal and extraperitoneal. Anterior interbody fusion is commonly used in cases of L5 disintegration or mild slippage without neurogenic symptoms and in cases where the posterior approach has been extensively resected and it is difficult to do posterior fusion. Anterior interbody fusion can restore the height of the intervertebral space and enlarge the intervertebral foramen, thereby decompressing the nerve roots, especially in patients in whom posterior surgery has failed. However, anterior surgery is difficult and can cause complications such as hemorrhage, lower extremity venous thrombosis, abdominal organ damage, intestinal obstruction, and sexual dysfunction. Posterior interbody fusion is a posterior laminectomy and discectomy with bone grafting between the vertebral bodies to maintain or increase the spacing between the vertebral spaces, and can be performed simultaneously with nerve root exploration and decompression. Because it meets the biomechanical requirements and has a high fusion rate, posterior interbody fusion is currently considered the most reasonable method.
4 For severe slippage, some scholars advocate the combined application of interbody fusion and lateral and posterior transverse process tip implants. The need for internal fixation for spinal slippage is controversial; Wiltse believes that a slippage of less than 25% does not need to be repositioned, and most slippages of less than 50% do not need to be repositioned; Dick believes that a slippage of less than 50% without neurological symptoms should be fused in situ, and an internal fixator can be added to the posterior fusion to shorten the recovery time and improve the fusion rate. Matthiass et al. suggested that fusion should be performed in cases with more than 30% slippage, a tendency to progressive slippage, and neurological deficits. Resetting can restore the normal sequence of the spine, the morphology and volume of the spinal canal, improve the appearance, facilitate nerve root decompression and restore the normal biomechanical function of the lumbosacral region.
5 In recent years, the application of transpedicular internal fixation has made the reset possible and the fixation effective. For example, RF, DRFS, CD, Steffee, Socon and other instruments are used for repositioning and fixation. Any single-segment or short-segment pedicle screw system with posterior lift tension can be applied with similar principles. For slippage, L5 slip laminectomy with L4 repositioning internal fixation on the sacrum is used for fusion (Gaines procedure). The internal fixator not only resets the slip, but also plays a key role in maintaining spinal stability and preventing reslip for some time after surgery, and ensures and promotes firm fusion of the implant, thus significantly increasing the fusion rate.
The TFC is a 70% perforated metal tube with threads to provide reliable fixation and minimize the possibility of intervertebral space collapse and intracanal bone grafting. This allows for intervertebral fusion. It has been widely used clinically in combination with internal fixators with significant results. However, this method requires high technical requirements, and should be used with caution.
7 leeds-Keio ligament The use of the pedicle screw fixation technique allows complete repositioning of the lumbar spondylolisthesis to achieve strong fixation, but its postoperative complications are increasing. mochida pioneered the use of leeds-Keio ligament surgery to treat a group of patients with elective lumbar spondylolisthesis and obtained excellent clinical results equivalent to the pedicle screw fixation technique. The surgery primarily addressed intervertebral stability or enhanced fusion of the posterior lumbar column, and it is believed that the pedicle screw fixation type is more appropriate for addressing lumbar slippage compared to the lumbar spine. Especially for those who have a mild degree of slippage.
(III) Evaluation of surgical efficacy
There are various methods to evaluate the efficacy of postoperative lumbar spine slippage, including: clinical assessment of lower back pain and lower extremity pain, such as LBOS; imaging evaluation available if fusion is performed, such as slip angle, slip rate fusion rate; comparison of preoperative and postoperative work and recreational function; and patient self-evaluation of treatment outcome. In addition, perioperative complications need to be considered.
1 Indications for surgery for lumbar spondylolisthesis The prevalence of lumbar spondylolisthesis in the population is approximately 5%. Of these, with isthmic cleft and degenerative slippage accounting for the vast majority of existing patients, correct, reasonable, and systematic conservative treatment can result in symptomatic relief or stabilization in some patients without the need for surgical treatment. In our group, there were 121 cases with active conservative treatment for a period of time, but the symptoms were still obvious or aggravated. To explore the reasons for this: (1) patients’ awareness of conservative treatment is insufficient; (2) complete conservative is difficult to carry out because of the current fierce social competition; (3) the factors of spinal instability have existed for a long time in patients, and the lumbosacral region is under a large load, which makes it difficult for conservative treatment to ensure long-term relief of symptoms at this time. In this group, preoperative imaging and CT examination were performed. The spinal stenosis and the spinal cord compression of nerve roots and dural traction caused by slippage, especially the reactive hyperplasia and hypertrophy of the synovial joint caused by long-term instability, which made the nerve root canal narrower with spinal slippage, were the symptomatic basis for the difficulty in relieving the main symptoms of the patients.
The root cause of lumbar spondylolisthesis is the compression of the cauda equina and nerve roots, so the key to relieving symptoms is adequate decompression of the compressed nerve roots and cauda equina. The traditional concept of decompression focuses on laminectomy decompression, and early Gill had some success in patients with mild lumbar spondylolisthesis, while Suk believes that when treating spondylolisthesis, the damaged nerve roots must be decompressed to reduce the strain on the nerve roots during repositioning; on the other hand, this facilitates the ideal repositioning of the slipped vertebrae, and simple laminectomy decompression is not enough. The lumbar 5 and sacral nerves are often damaged in patients with slipped vertebrae, the latter being mainly stretched on the posterior superior border of the sacral nerve, and repositioning is the ideal measure to relieve the strain, while the lumbar 5 nerve is mainly the result of hyperplasia of the fibrocartilage in the isthmus in addition to the straining effect of slipping, and the combined effect of mechanical and chemical inflammatory substances. In some cases, it is accompanied by disc herniation, spinal stenosis or compression by abnormal activity of the spinal plate, especially in those with a large degree of slippage. Zou Dewei believes that the pathological changes of this slippage are centered on the upper and lower tuberosities towards the spinal canal and towards the neural canal, and in fact this group has obtained better results by complete decompression of the tuberosities. The subjective satisfaction of complete nerve root relaxation was above 90%. Therefore, it is believed that decompression should go beyond the traditional concept of only performing simple decompression of the vertebral plate and should be centered on the small articular eminence to completely decompress the spinal canal in the slip plane, especially the nerve root canal, especially in patients with nerve root symptoms.
Wiltse is an advocate of in situ fusion, while other scholars believe that in situ fusion is effective and that repositioning is not necessary, but rather that repositioning can lead to many complications. More scholars believe that in situ fusion has inevitable drawbacks and hold a more supportive view of repositioning. kim’s study showed that despite strong in situ fusion, lumbar spondylolisthesis progressed. From a biomechanical point of view, the fundamental aim of surgical treatment is to restore the line of force of the spinal sequence, to restore the shear stress to normal levels, and to reconstruct spinal stability, especially the normal angle of inclination of the sacrum should be considered. Seitsalo et al. concluded that severe lumbosacral retroversion has a greater impact on spinal stability than translation itself, increasing the shear load on the intervertebral disc and sacroiliac joint and aggravating their degeneration. In situ fusion obviously does not meet the requirements of normal spine biomechanics and is not the best way to treat lumbar spondylolisthesis. Intraoperatively, we found that “step”-like changes in the spinal canal and “s”-like deformation of the dura mater occurred after lumbar spondylolisthesis, and the more severe the spondylolisthesis, the more obvious these pathological changes were, and when the spondylolisthesis was corrected, improvement was obtained with satisfactory results. This suggests that vertebral slippage is the cause of the pathological changes in the disease. Moreover, if the deformity remains, it will increase the tension of the internal fixation device or bone graft, which will affect the outcome of the surgery. Therefore, we suggest that the treatment of lumbar spondylolisthesis should be based on adequate decompression for maximum repositioning. Anatomical repositioning should be considered as a routine goal in the treatment of lumbar spondylolisthesis.
4 Selection of appropriate internal fixation is one of the important factors for the success of surgery In recent years, some authors have used different internal fixation devices to carry out the treatment of lumbar spondylolisthesis, and the efficacy has been evaluated differently. In this paper, we review the use of Harrington, Steffee, Socon, RF, and DRFS internal fixation systems in our hospital since 1991 to treat patients of different periods, respectively. From them, the efficacy of various surgical methods can be summarized, and it is found that the disadvantages of Harrington system fixation are unreliable fixation and uncertain repositioning effect, and the final repositioning rate of our group is only 4.7%, and there is no obvious change to the slip angle. The final restoration rate in this group was only 4.7%, and there was no significant change in the slip angle. Due to the fusion of the whole lumbar spine, the anterior convexity becomes smaller and the sagittal plane balance is lost. Steffee plate fixation is stable and fixes the fractured slipped vertebrae and the upper and lower vertebrae, and the slipped vertebrae can be repaired by the lifting effect of the pedicle screws, but its longitudinal bracing rate is poor, and the intervertebral space height and intervertebral foramen height do not change much. It is not easy to correct the rotation in the sagittal plane, and it is often necessary to use a straight plate to reposition the vertebral body first, then remove the plate and bend it for a second time to correct the anterior convexity of the vertebral body, and six pedicle nails are needed, which increases the difficulty of the operation and low reset rate of the slipped vertebral body. Socon is a new system of internal fixation for lumbar slipped vertebrae that has been used in domestic vertebral column surgery in recent years. It is characterized by a set of repositioners in addition to its own pedicle screw connection to the vertebral body. However, the longitudinal bracing effect is still not strong, and like Steffee, it cannot improve the rotation in the sagittal plane of the lumbar spine. the threaded rod structure of the RF device has the bracing effect, and the angled nail makes the first rotation of the sacrum in the sagittal plane occur when resetting, restoring the normal tilt of the sacrum, thus improving the retroconvex deformity in the sagittal plane, and the posterior pulling effect of the lifting nail on the slipped vertebral body makes its resetting effective. The final repositioning rate of this group was 87.3%. However, the correction stress is overly concentrated, so that the angle nail into the angle easy to cause broken nail. DRFS device has RF three-dimensional space of the correction force, the steel plate strength, high hardness, coupled with the screw thick, wide pitch, resulting in a larger holding force, the reset effect is good. The final repositioning rate of this group was 92.9%. Therefore, in the treatment of lumbar spondylolisthesis, we believe that the RF and DRFS systems have better efficacy.
5 Osseointegration is a necessary step to stabilize the spine and improve the efficiency of surgery. All implants are temporary, but only osseointegration is the long-term solution. Fusion of slipped vertebrae is the ultimate goal of surgical treatment. Any implant is foreign to the human bone, and there is incompatibility between the bone and the implant, and the implant has a certain degree of fatigue, especially under the effect of stress, the implant will cause degenerative changes in the connecting bone, making the implant loose and dislodge from the bone connection, i.e. the bone and the implant do not match each other. Therefore, only strong bone graft fusion can maintain the stability of the spine. Although the use of allogeneic bone graft is widely used with the development of biotechnology and processing, there are still many reports of allogeneic rejection. In contrast, autologous bone graft is histocompatible to human body, and there is no rejection problem. Schlegel and Evans analyzed from the biomechanical point of view that the gravitational line of the body passes through the anterior part of the vertebral body, the muscle tension passes to the posterior part, and 80% passes through the intervertebral disc, so the intervertebral fusion is most consistent with the biomechanical requirements. steffee pointed out that the successful intervertebral bone graft is the best result among all the bone grafting methods. In our group, posterior intervertebral body implant fusion was routinely performed using autologous iliac bone, and the fusion rate was as high as 92.4%.
6 Long-term outcome assessment The clinical outcomes of lumbosacral fusion surgery reported in the literature vary greatly, which we believe is related to the fact that the fusion indications, fusion methods, follow-up time and evaluation criteria are not identical. In order to make the efficacy of lumbosacral surgery comparable, it is necessary to establish uniform evaluation criteria. Applying the objective criteria recommended by Greenough et al. as the efficacy evaluation, the subjective satisfaction rate was 94.3% and the objective satisfaction rate was 81.6% in our group of 158 cases. This is similar to the satisfaction rates reported by Greenough et al. and Howe et al. The reasons for this are, first of all, that different individuals have different pain tolerance and expectations of surgery, while postoperative nutrition, functional rehabilitation methods and social pressure are not entirely consistent and cannot be ignored. This deficiency can be remedied if the Dahiel criteria are combined with a categorical assessment of different patients. Secondly, although LBOS is comprehensive, it still needs to be revised, for example, exercise, swimming and sexual life are difficult to be assessed accurately for most patients in China. If the assessment criteria could be combined with other assessment aspects and some items could be improved and adapted to the physical condition of our people, this could be a more accurate assessment of the efficacy of lumbosacral surgery.