Abstract The degenerative process of the lumbar spine usually results in stiffness, but is generally stable and in rare instances unstable. Lumbar spine slippage is the main form of lumbar degenerative instability, manifesting as horizontal displacement of a single vertebral body relative to another vertebral body, or more extensive degenerative scoliosis. All forms of lumbar instability can lead to low back pain and nerve entrapment. Most instabilities due to degeneration are self-limiting and can be treated non-surgically, although, of course, there are sometimes progressive and relatively severe symptoms that must be relieved by surgery. 1. Introduction Low back pain is very common, and more than 70% of individuals in developed countries may have experienced simple low back pain, with the most frequent age being 34-44 years. Most of this type of low back pain is self-limiting and the main goal for any spine specialist treatment is to restore the patient to a relatively comfortable condition with as few interventions as possible. In this process, all spine specialists should leave no stone unturned to find a single point of pain provocation before a successful treatment can be administered. In a series of degenerative processes, any one structure can cause low back pain, and leg pain can be affected by multiple loci. In the domino effect-like process of spinal degeneration, the first to occur in most cases is disc degeneration. The disc can act as a cushion for axial stresses and it is also an important component of the functional unit of the spine. The intervertebral discs coordinate with the synovial joints to allow for movement in both the sagittal and coronal positions. During degeneration, the loss of disc-related functions decreases the mechanical stability of the anterior spinal functional unit. After the loss of stability due to disc degeneration, hypertrophy of the ligamentous structures can occur in the diseased segment due to increased loading and new torsional stresses. The degenerated herniated disc and the hypertrophied ligaments can reduce the volume of the spinal canal and lead to spinal stenosis. As degeneration increases, the synovial joint also becomes degenerated and hypertrophied. However, while this is the typical sequence of lumbar degeneration, the fact is that different regions of the spine degenerate at different rates. One side of the same segment may degenerate more rapidly than the other. Often, this asymmetric pathology is thought to lead to two common types of lumbar degenerative instability, lumbar spondylolisthesis and scoliosis. Of course there are some complex spinal instabilities, such as the same patient having both degenerative scoliosis and slippage. These conditions often result in significant functional impairment and pain. The treatment of degenerative lumbar instability must first be done with full recognition of the patient’s chief complaint. Patients with degenerative instability of the spine typically complain of low back pain and lower extremity symptoms, but rarely focus on spinal deformities. For the spine surgeon, the patient must be directed to conservative treatment before discussing the need for surgery and the extent of surgery. The word “listhesis” is of Greek origin and originally meant “to slide”; the word “spondylolisthesis” also means “spondylo”. The word “spondylo” is also of Greek origin and has a similar meaning to “spinal”, which means “spine”. The most common direction of spondylolisthesis is forward, although other directions of vertebral slippage are possible. Table 1 provides examples of the various terms used to describe degenerative spondylolisthesis based on orientation. Table 1 Types of vertebral translation or slippage While this article focuses on the degenerative mechanisms of slippage, Wiltse classifies and describes other causes of anterior spinal slippage, such as isthmic cleft, traumatic, pathological, and dysplastic (congenital).All other types of slippage described by Wiltse are usually associated with various forms of bony damage to the vertebral arch.Macnab describes a This lesion was originally called “pseudosynovial” and is considered to be part of the degenerative process of the spine along with damage to the intervertebral discs and synovial joints. Most degenerative spondylolisthesis occurs at the L4-5 segment and is more common in women and in people over 50 years of age, based on epidemiological data [8]. and is more prevalent in African Americans than in Caucasian populations. It is still not possible to explain this demographic difference. It has been speculated that certain hormonal effects make the ligaments more lax in women. It may be for this reason that the body structure of children is more susceptible to such problems, but the exact pathophysiological mechanisms underlying this pathological process are still unknown. Other factors that may contribute to degenerative spondylolisthesis include differences in orientation of the synovial joints in different regions and differences in pelvic force lines in males and females. the synovial joints of L4-5 tend to be more sagittal, whereas L5S1 tends to be more coronal. the differences in alignment of the synovial joints of the L4-5 segment allow for bony blockage and reduced resistance to slip in the antisagittal position. In addition, osteoarthritic lesions are more common due to the high mobility of this segment. Matsunaga et al. followed 145 patients with spinal slippage, all of whom underwent at least 10 years of nonoperative treatment. Results found that 34% of patients had progression of spondylolisthesis, but the authors did not find a correlation between changes in clinical symptoms and progression of spondylolisthesis. Figure 1 shows the grading system for the severity of lumbar spondylolisthesis. As the disc degenerates and collapses, the patient’s low back pain subsides. In addition, no further increase in slippage was observed in patients with collapsed discs. Seventy-six percent of patients who initially had no neurological symptoms remained free of any neurological damage after ten years. In contrast, 85% of patients who initially had neurological damage experienced a worsening of neurological function during the follow-up period. Figure 1 The higher the degree of vertebral displacement, the higher the grade of slippage. grade 1 is <25%; grade 2 is 25%-50%; grade 3 is 50%-75%; grade 4 is 75%-100%; and grade 5 refers to >100%. Degenerative lumbar slippage usually presents as instability of a single segment, whereas degenerative scoliosis is an overall instability. Unlike idiopathic or congenital scoliosis, lumbar degenerative scoliosis is rarely accompanied by structural deformity of the vertebral body. This bending pattern results from increasing degeneration with multiple segments. Degenerative scoliosis can result from the effects of osteoporosis, degenerative disc disease, pathological changes in osteoarthritis, spinal stenosis, cartilage plate deformities, compression fractures, asymmetric orientation of the articular bony joints, and slippage (especially lateral displacement), and no direct correlation between degenerative scoliosis and any of these degenerative changes has been demonstrated. If the spine is straight on imaging in adulthood and gradually develops curvature with degeneration, this is the best point of differentiation from adult idiopathic scoliosis. In contrast to degenerative scoliosis, which is usually dominated by curvature in the lower back, untreated adult idiopathic deformities tend to have a predominantly thoracic curvature. Robin et al. looked at the prevalence of degenerative scoliosis in a long-term follow-up study in which 554 subjects, ranging in age from 50 to 100 years, were radiographically examined to determine the presence, morphology and progression of scoliosis in these older adults and to try to explore the correlation between degenerative scoliosis of the lumbar spine and osteoporosis and low back pain. These subjects were selected from a general population of 3600 subjects, all with complete imaging data, during 13 years of clinical work. It was found that 70% of the subjects had varying degrees of scoliosis, but scoliosis of more than 10° was seen in only 1/3 of the subjects, and none had a curvature of more than 20°. During follow-up, 10% of subjects with no previous deformity developed scoliosis. 46% of subjects had an increase in the degree of scoliosis of at least 4°. Some of the subjects with prior scoliosis progressed more than 10°, with a mean of 7° (3°-18°). None showed remission of scoliosis. In general, the greater the progression of scoliosis in older patients, the greater the progression. The findings showed that the presence and progression of scoliosis did not correlate directly with osteoporosis. And there is no direct correlation between scoliosis and low back pain, nor between scoliosis and degenerative changes in the spine on imaging, but there is a tendency for the more severe the pain, the more pronounced the deformity. In a similar study, Pritchett and Bortel looked at 200 patients with clinically more pronounced scoliosis, averaging 24° (14°-60°). 1/4 of the patients had significant scoliosis, exceeding 35°. In all patients, relevant findings included degenerative disc disease, intervertebral space narrowing, endplate sclerosis, and vertebral body rotation. Among the patients with curvature, vertebral rotation (Figure 2) was 21% for 1 degree; 67% for 2 degrees; and 12% for 3 degrees. 111 patients (55.5%) had degenerative spinal slippage. 1/3 of the patients had degenerative slippage of L4 and L5, and 10 had multi-segmental slippage. 78 patients had lateral displacement, mostly in the L3-4 and L4-5 segments. During the conduct of this study, 41 patients had a series of imaging data for more than 10 years, allowing the evaluation of the progression of the curvature. The majority of patients (73%) had a mean progression of 3° per year of curvature. The initial Cobb angle, the degree of rotation of the parietal spine, the lateral displacement, and the relationship of the lumbar spine to the iliac crest line all made good predictions. All curves progressed if the iliac crest line passed through the L4-5 gap, or was located below it, and the vertebrae were rotated ≥2 degrees. Other factors for progression of curvature included initial curvature, Cobb angle ≥30°, or lateral displacement ≥6 mm. In all patients with relatively stable curvature, the iliac crest line passed through the L4 vertebral body. These imaging landmarks are described later in the case, as shown in Figure 3. Figure 2 The degree of vertebral rotation can be estimated on orthogonal radiographs. The vertebral arch is first located and is 0 degrees if the location and morphology of the arch is normal; 1 degree if the arch is in a normal position but has a mild tilt; the vertebral body is trisected through the vertebral body by drawing a plumb line and marking the vertebral body midline. 2 degrees and 3 degrees when the arch passes through the first trisection and midline, respectively; 4 degrees of rotation if the vertebral body continues to rotate and the arch is gradually displaced beyond the midline to the second trisection. Figure 3 The patient was a 52-year-old female with right-sided leg pain mainly in the L3 and L4 dominant regions, accompanied by low back pain dysfunction for several years. A and B are standing radiographs. Figure B, standing orthopantomogram shows multiple risk factors for progression of low back bending, such as Cobb angle ≥30°, lateral displacement ≥6 mm, and iliac crest line through or below the L4-5 gap. Figure C and D show T2-weighted MRI images. The lateral saphenous fossa on the right side of this patient is significantly narrowed. Figures E and F show images 2 years after a strong internal fixation fusion, at which time the patient had only mild low back pain and complete relief of leg pain. 3. Clinical signs and symptoms in patients with degenerative lumbar instability Patients with symptomatic degenerative slippage, regardless of type, may have low back pain as the main complaint. Since all patients have complaints of axial low back pain, it is often difficult to determine the true point of pain provocation [20]. Since spinal instability is the result of a combination of disc degeneration and synovial joint degeneration, both of which can themselves lead to pain. It is generally accepted that if the pain originates from the disc, the symptoms are aggravated by bending forward, because this movement loads the axial load on the disc and is an elevated pressure within the disc. Pain in the synovial joint, on the other hand, is thought to be likely to increase with posterior extension and rotation of the spine and is often associated with paravertebral pressure. Patients with degenerative slippage may also have neurogenic claudication or neurogenic signs and symptoms. Both conditions occur as a direct result of nerve entrapment, a pathologic change that is the result of slippage, disc herniation, hypertrophy of the ligamentum flavum, and protrusion of osteoarthritic growths of the synovial joints into the spinal canal resulting in decreased spinal canal volume. Pain on standing or walking, cramping, and a feeling of heaviness in the lower extremities are clinical manifestations of neurogenic claudication. These symptoms are mainly located in the buttocks, proximal thighs, and lower legs and may be accompanied by numbness and weakness of the lower extremities. Patients usually notice pain relief when sitting or bending forward to lean on an object. For example, they may report relief when pushing a shopping cart forward, or when shopping at the grocery store and can walk longer distances (shopping cart sign) [9]. There is no clinical staging system to evaluate the severity of symptoms; therefore, clinicians are asking patients how far they can walk continuously to quantify their symptoms. This, of course, depends largely on the patient’s endurance while walking. The physical examination of a patient with degenerative instability of the spine should begin with observation of the patient’s gait upon entering the consultation room. The patient enters the office with a painful or decompensated gait, usually indicative of low back pain or leg pain. When performing a physical examination, the patient may present with a loss of lumbar lordosis or a direct sagittal or coronal imbalance. Usually the patient is in a bent-over position with hip flexion contracture and atrophy of the low back muscles. These features are often overlooked when performing a spinal examination, and they are the likely cause of muscle fatigue low back pain. Tests for range of motion show normal or increased anterior lumbar flexion, which is primarily due to intersegmental hypermobility and extensive ligamentous laxity. In patients with severe spondylolisthesis, the spinous processes of the affected segments may be palpable with significant steps. In patients with severe degenerative scoliosis, a pronounced hunchback deformity of the lumbar spine may be present and a rib protrusion with discomfort may be visible on the convex side of the thoracic segment. A careful neurological examination must be performed to rule out nerve root involvement. In addition, a thorough vascular examination must be performed to determine if the symptoms are due to peripheral vascular pathology [9]. 3.1 Imaging The radiographic examination of spinal instability should include a standing lumbar hyperextension-hyperflexion radiograph to determine the extent of intersegmental instability in spinal slippage. Supine Bending views are useful for idiopathic scoliosis but are of little significance for degenerative scoliosis. Standing hip and knee extension radiographs are meaningful for evaluating sagittal and coronal balance in patients with severe deformity. Sagittal balance is determined by measuring the distance between the C7 drape and the posterosuperior angle of the sacral endplate. Coronal balance is evaluated by measuring the distance between the C7 plumb line and the mid-sacral plumb line. In addition, the location of the bend, the size of the bend, the number of involved segments, the forward or lateral slippage of the involved segments, and the severity of the rotational deformity can be evaluated on radiographs. MRI is necessary in patients with neurogenic symptoms or neurogenic claudication. Patients with spinal deformities may have narrowing of the central spinal canal, lateral saphenous fossa, and intervertebral foramina in multiple segments, and these can be evaluated in detail on MRI. This allows the imaging presentation to be correlated with the patient’s symptoms and the segment responsible for the associated symptoms to be identified. In addition, MRI can provide many details, such as the degree of disc degeneration in each segment, that are helpful in surgical planning and can also help determine the extent of surgical fusion. Myelography CT sagittal and coronal reconstructions are useful in patients with severe rotational deformities. CT scans provide better details of the bony anatomy, which can help in surgical planning. For claustrophobic patients and those who cannot undergo MRI due to metal in the body (e.g., cochlear prosthesis, etc.), or aneurysm clips or metal built-ins in the spine that can cause artifacts, myelography CT may be an option for evaluation at this time. 4, conservative treatment of lumbar degenerative instability The treatment of lumbar degenerative instability should first be considered conservative methods. Non-operative treatment is very commonly used, but is largely empirical and is rarely supported by evidence in the literature from randomized studies. Non-surgical treatments are usually safe compared to surgical interventions and usually provide relief of acute episodes of low back pain or neurological symptoms. The preferred and most common method of conservative therapy is short-term rest with the application of over-the-counter NSAIDS medications. Rest should not exceed 2-3 weeks, and prolonged sitting may lead to weakness. Application of NSAIDS during this time is therapeutic for both low back pain and radiculitis. In combination with rest and NSAIDS-like medications, the physical therapist can perform modalities such as pulsed wave pain therapy, massage, hot and cold packs, and stretching and traction to abort the acute pain episode. After a period of rest, the physical therapy program should emphasize bending exercises for patients with neurogenic claudication, and all patients should strengthen low back strength training as well as aerobic exercise. In addition, exercises can also be performed on a stationary bicycle, especially in patients with neurogenic claudication, because theoretically, in the flexed position the intervertebral foramen opens wide and the compression of the dural sac is reduced, thus relieving the symptoms of neurogenic claudication. Patients should be encouraged to not only participate in this treatment program, but also to consider it as part of a long-term treatment plan, especially in the event of a reoccurrence of low back pain, radicular symptoms, and neurogenic claudication. NSAIDS are often effective in relieving symptoms caused by arthritis, but they should also be closely monitored, including some common side effects such as gastrointestinal discomfort and nephrotoxicity. Tricyclic antidepressants may be helpful for patients with significant nocturnal leg pain and as an adjunct to chronic low back pain. Similarly, gabapentin and pregabalin can help relieve pain of neurogenic origin. These medications also have some side effects such as fatigue and confusion. Clinicians should carefully consider the side effects associated with these drugs before prescribing them to older adults. The application of narcotic drugs for the treatment of low back pain is still controversial, mainly because these drugs have some addictive properties. If these medications are to be applied over a long period of time, a pain department consultation should be considered, not only because of the addictive nature, but also to make the patient aware of the potential for resistance to the medication over time and a decrease in clinical efficacy. Spinal orthoses can also be used to control low back pain. This approach is primarily used in patients with degenerative scoliosis for symptomatic relief, and it is worth noting that this device has never been shown to stop the progression of bending deformities or slippage in adults. Pain relief may be due to a balancing effect from the discomfort of wearing the brace, or it may be the result of relaxation of the trunk muscles. Patients wearing a brace should routinely train their low back muscles to prevent further muscle function degeneration. Spinal injections are another option for non-surgical treatment. Depending on the patient, clinicians can choose from a variety of injections such as epidural steroid injections, synovial joint blocks, nerve root blocks, and painful point closure. Epidural steroid injections are widely used in patients with spinal stenosis with or without spondylolisthesis. The theoretical advantage is mainly the relief of low back and nerve root pain. There are no literature reports of epidural steroid injections in patients with simple spinal slippage or degenerative scoliosis. There is also no literature evidence of clinical efficacy beyond 3 years. Everett et al [23] performed a systematic evaluation of the literature related to the non-surgical treatment of scoliosis in adults, and they found physiotherapy, bracing, and massage to be level IV evidence, while steroid injections were level III evidence. Non-surgical treatment of degenerative spinal instability, although not well supported by evidence, can help improve the functional status of patients. While undergoing conservative treatment, patients may work to lose weight, optimize their medical comorbidity status, and quit smoking if they smoke. After a period of conservative treatment, the clinician has the opportunity to have further communication with the patient to clarify the patient’s expectations for non-surgical and surgical treatment. The type, scope, risks, and possible benefits of surgery may also be discussed. Finally, if the patient does require surgery, this period of conservative treatment may make the patient more prepared for surgery, which may improve the ultimate clinical outcome. 5. Surgical treatment of degenerative lumbar instability: from single-segment spondylolisthesis to reconstruction of complex scoliosis It is important for the operator to maintain good communication with the patient. Surgery should only be considered if persistent or recurrent low back pain results in significant reduction or limitation of daily activities and if conservative treatment is ineffective. In addition, in patients with degenerative scoliosis, progression of the deformity can lead to sagittal and coronal imbalance, which is also an indication for surgery. The operator and patient should weigh the best surgical option that will provide a better quality of life for the patient. Decompression surgery is the mainstay of treatment for symptomatic spinal stenosis. Several studies have shown that laminectomy for degenerative spondylolisthesis has good clinical outcomes with excellent rates of more than 80%; however, this is a decompression procedure alone. Extensive decompression may lead to poorer clinical outcomes, especially in cases with extensive synovectomy. Patients with total synovectomy have an excellent rate of only 33%; those with preserved synapses have an excellent rate of 80%; and those with additional posterior lateral intertransverse fusion have an excellent rate of 90%. In 1991, Herkowitz and Kur conducted a prospective randomized controlled study of 50 consecutive cases of degenerative spondylolisthesis undergoing decompression alone or decompression + bilateral postero-lateral fusion, with a mean follow-up of 3 years. Patients with decompression fusion had significantly improved clinical outcomes. There were 9 cases of pseudarthrosis formation in the fusion group, and all patients with pseudarthrosis formation had excellent or good clinical outcomes at the final follow-up. This result was confirmed in a study by Ghogawala et al [28], who performed a retrospective analysis of the question of whether fusion improves functional outcomes at 1 year postoperatively. Patients were aged 50-81 years with degenerative spondylolisthesis degree I with lumbar spinal stenosis and no severe instability (intersegmental motion <3 mm). 20 patients underwent decompression surgery alone and 14 had sexual decompression and internal fixation with posterior posterolateral fusion. < p=""> Demographic data, imaging performance, functional status (Oswestry dysfunction score), and the SF-36 questionnaire for health status were similar in both groups at the baseline level. fusion rate at 1 year was 93%, and compared with the baseline status, both procedures in terms of Oswestry dysfunction score and SF-36 score (p<0.001) significantly improved the functional outcome of the patients. The authors concluded that patients with i-degree spondylolisthesis lumbar stenosis have significantly better clinical outcomes 1 year after surgery, and fusion may result in greater functional improvement. < p=""> In the recent literature, the clinical outcomes of posterolateral fusion internal fixation after decompression have been evaluated. The goal of surgical treatment is to improve clinical outcomes while also weighing the cost of internal fixation devices and complication profiles. In 1997, Fischgrund et al. published a prospective randomized study comparing the clinical outcomes of decompression fusion alone versus decompression fusion internal fixation. Sixty-seven patients were randomized to both procedures with a mean follow-up of 2 years. The results found that internal spinal fixation improved the fusion rate (82% in the internal fixation group: 45% in the non-internal fixation group). However, there was no significant difference in clinical outcomes between patients with internal fixation applied. In terms of short-term outcomes, successful fusion does not affect the clinical outcomes of patients. Long-term follow-up studies by Herkowitz and Kurz, Fischgrund et al. and Kornblum et al. showed that patients with pseudarthrosis did not have as good clinical outcomes as those with solid fusion. The authors concluded that a solid fusion facilitates a good long-term outcome and therefore should be combined with internal fixation at the time of initial surgery to increase the fusion rate. In another study, Booth et al [31] performed posterior decompression fusion internal fixation in patients with lumbar degenerative slipped spine and evaluated their complication rates, revision rates, imaging outcomes, and patient satisfaction by 5-year follow-up. During the follow-up, none of the patients experienced adverse outcomes such as neurological dysfunction, symptomatic pseudoarthrosis formation (i.e., pain, X-ray translucent bands and loosening of internal fixation), recurrent stenosis of the fused segment, or progression of the slipped grade. Atlas et al [32] provided data of longer duration in a prospective observational cohort study of a group of patients with lumbar spinal stenosis treated surgically or non-surgically, respectively, with a long-term follow-up of 8-10 years. The results found no significant differences between the two groups in terms of back pain relief, improvement in major symptoms, and satisfaction with current status, regardless of whether non-surgical or surgical treatment was initially chosen. However, patients who initially underwent surgical treatment had better relief of leg pain and functional status related to the low back. Anderson et al [33] recently reported better clinical outcomes with the application of interspinous decompression devices in patients with lumbar degenerative slipped spine compared to non-surgical treatment. Only 12% of patients in the nonsurgical treatment group had a favorable outcome at 2 years, whereas the interspinous spine bracing device achieved a significant improvement in 63.4% of patients. Longer-term data are still needed to support the routine application of this device, especially in patients with instability, such as degenerative slippage and scoliosis. However, this does, after all, offer the possibility that the problem can be solved with a much smaller procedure, especially in the elderly, who have more medical comorbidities and often have difficulty tolerating larger procedures such as decompression fusion. The same debate exists for deformities such as scoliosis due to multi-segment degenerative instability of the lumbar spine with decompression versus decompression combined with fusion. Similar to other spinal deformities, indications for surgery include severe symptoms, intractable pain such as axial low back pain, neurogenic claudication, or radiculitis. In patients with spinal deformities, it is important to focus on the progression of the deformity as much as the progressive deformity that may lead to progressive functional impairment. Symptoms should include significant limitations in activities of daily living, as deformity surgery is often complex and complications can be more frequent, especially in the elderly and in patients with poorer physical status. Decompression-only surgery for multisegmental instability and scoliosis has been studied, but they were small sample size case series and nonrandomized clinical studies that primarily evaluated patient-reported functional outcomes.Frazier et al. reported 19 cases of degenerative scoliosis, 15 of which underwent decompression-only surgery, and all had at least 15° of curvature, but most were moderate. The authors found that preoperative scoliosis did not correlate with improvement in leg pain and walking ability after decompression-only surgery, but these patients had even less postoperative relief of low back pain. Likewise, there was no correlation between clinical outcomes and postoperative progression of curvature. Decompression combined with some type of fusion has been the standard procedure for degenerative lumbar scoliosis.Nasca et al [35] reported nine patients, aged 47-74 years, who underwent internal fixation with decompression fusion.Six patients had good clinical outcomes and three had poor outcomes.Marchesi and Aebi [36] followed 27 patients with posterior fusion internal fixation, and in terms of pain relief and ambulatory function In terms of pain relief and walking function, 86% of the patients were satisfied with their results. Similarly, Simmons and Simmons observed 40 patients with degenerative lumbar scoliosis, all of whom underwent posterior fusion internal fixation, although 83% had postoperative lower extremity symptoms and 93% complained of no or only very mild lower extremity pain postoperatively. Grubb et al. reported 25 cases of degenerative scoliosis: 20 cases underwent posterior spinal fusion for internal fixation, 1 case of anterior fusion, and 4 cases of combined anterior-posterior surgery. 20 patients underwent posterior fusion to the sacrum alone, with a 40% pseudarthrosis rate. Low back pain was still present in most cases. The rate of revision surgery 4 years after surgery was 36%. The source of persistent pain was usually identifiable, so the rate of revision surgery was relatively high. The study was unable to compare clinical outcomes between subgroups because of the small sample size, and patient satisfaction at 4-year follow-up was 70%-80%. There are other surgical approaches, most of which are not supported by objective evidence. postacchini [39] proposed a hypothesis that patients with neurogenic claudication, with no or only very mild low back pain and mild curvature could be treated by decompression surgery alone. However, most patients should undergo decompression fused with bilateral internal fixation.Vaccaro and Ball concluded that decompression alone may lead to further collapse, instability, and worsening of low back pain and neuropathic pain. Therefore, decompression fusion surgery should be an option for most patients. As a guideline, all patients with neurological symptoms must undergo decompression surgery. Fusion with or without internal fixation should focus on the presence of predictive signs associated with progression of curvature, as shown in Figures 2 and 3. In particular, degenerative scoliosis with spinal stenosis can occur at the top of the bend or possibly in the compensatory bend. In turn, these symptoms may also arise from a lateral displacement >5 mm or from a forward slippage. In order to decompress such compression, extensive local decompression may be required, which can lead to further instability. If the patient does not have significant coronal or sagittal imbalance, fusion should be limited to the decompressed segment. However, there are no good guidelines to help surgeons make treatment decisions. Posterior interbody procedures, such as posterior lumbar interbody fusion or transforaminal interbody fusion, are still valuable especially for correction of short-segment deformities. These procedures provide indirect decompression of the foramina and increase the chances of fusion in areas where extensive posterior decompression has been performed. If decompression alone is performed or a short-segment fusion is performed, the operator must be aware of the potential for further progression of the patient’s scoliosis, or even the necessity for a more extensive revision surgery in the future. Extensive fusion must include all segments of the nerve decompression, as well as all areas of structural curvature. This usually requires extending the fusion to the thoracic spine. The proximal end of the fusion extent for scoliosis should end at a fixed segment, or at the top vertebrae of the coronal or sagittal spinal curvature. Usually, T10 or a segment of the upper thoracic spine should be selected based on this principle. T10 is chosen because this segment is precisely a rigid thoracic vertebra, surrounded by a rib cage for support. The distal end of the fusion range is often a difficult choice for the surgeon: L5 or the pelvis. Fusion of the long segment should not stop at the sacrum alone, as fusion to the sacrum alone has a high failure rate. The surgeon should consider an additional interbody fusion of the L5S1 segment, either via the posterior approach or the anterior approach alone, to structurally strengthen the L5S1 segment and accelerate fusion. 6. Summary The treatment of lumbar degenerative instability should be individualized according to the patient’s goals and quality of life with reference to the patient’s symptoms, physical condition, and functional deficits. There are several non-surgical and surgical options available. After completing a physical examination, non-surgical methods should be considered first, including rest, medication, and physical therapy. If a patient with lumbar spondylolisthesis decides to undergo surgery, the operator needs to determine whether to perform decompression or decompression fusion. When planning surgery for degenerative scoliosis, the need for fusion and the extent of fusion, whether it includes the sacrum, the need for anterior structural support, and the need for osteotomy to correct the deformity are all issues that need to be carefully considered.