15 Lumbar Spondylolisthesis
Symptomatic lumbar degenerative disease is a growing problem, and degenerative spondylolisthesis (DS) is one of the most common conditions for which surgery is performed. Spine surgeons are increasingly being challenged to evaluate the risk-to-benefit ratio of spine surgery carefully, but the literature specifically dedicated to the aging patient is sparse. This chapter reviews the epidemiology, clinical presentation, and biomechanical aspects of the disease. Conservative and various surgical treatment options including decompression and fusion surgeries are discussed, with special consideration of benefits, risks, and clinical outcomes in aging patients. In summary, age alone should not be considered a contraindication to surgical intervention; older adults who are optimized perioperatively can and should expect successful outcomes similar to their younger counterparts.
Conservative treatment is typically the first treatment of choice in patients with degenerative spondylolisthesis
Decompression may be a more appropriate treatment option due to shorter operative times and reduced blood loss, but there is increased risk associated with instability
Instrumented fusion may have improved fusion rates and results in better long-term clinical outcomes in properly selected patients
A comprehensive preoperative assessment, elimination of modifiable risk factors, and optimization of preventative measures and postoperative care can help to minimize or avoid complications in the aging patient population.
Degenerative spondylolisthesis (DS) is a common problem in older adults. DS is one of the most common conditions for which surgery is performed in the United States. 1 , 2 Life expectancy in Western countries has been increasing over the past several consecutive decades. 3 It is estimated that spondylolisthesis has a prevalence of about 20 to 25% among women, and 4 to 8% among men in the United States. 4 , 5 , 6 In those over the age of 65 years, the prevalence is reported to be 29% among women 4 and 31% among men. 7 He et al 8 found a prevalence of lumbar spondylolisthesis of 19.1% in Chinese men and 25.0% in Chinese women aged 65 years and older. Only a single vertebral level was involved 96% of the time, with the degree of slip ranging from 5 to 28% among those diagnosed with spondylolisthesis. Progression of existing spondylolisthesis over a 5-year period was observed in 12% of patients, with new onset of spondylolisthesis occurring among 12% without the condition at baseline. The authors found that the prevalence of spondylolisthesis did not vary by height, BMI, smoking history, diabetes, or heart disease. However, men with spondylolisthesis more often reported higher levels of physical activity or walking daily for exercise than men without spondylolisthesis. Similar results were reported by Wang et al, 9 where they found that spondylolisthesis progressed in 13.0% and 16.5% of men and women, respectively, and appeared de novo in 12.4% and 12.7% of men and women, respectively, at the 4-year follow-up on patients 65 years and older. In their epidemiologic study among older men, Denard et al 7 observed that the prevalence of back pain, back pain severity, and being bothered by back pain in the past year were not different among men with or without radiographic DS. Compared to their counterparts, however, men were more likely to report neurogenic symptoms in the last year and to have experienced recent limitations in performing activities requiring lower extremity function.
Clinical presentation of DS consists of intermitted low back pain, radiculopathy, and neurogenic claudication, 10 the latter being the most common symptom, reported by up to 82% of patients seeking surgical treatment. 11 Cauda equina syndrome is less common, but requires immediate medical attention and is reported in 3% of patients with spondylolisthesis. 12
The literature on the natural history of DS is limited. Matsunaga et al 13 published a prospective study which evaluated a total of 145 conservatively-managed patients for a minimum of 10 years. The progression of spondylolisthesis was observed in 34% of patients, but the authors noted that as the intervertebral disc space decreased, the patients reported improvement in low back pain. A total of 84 out of 110 (76%) patients remained free of neurological symptoms for the entire follow-up time. Although 29 out of 35 (83%) patients who had neurological symptoms experienced significant deterioration, this was not correlated with progression of spondylolisthesis.
15.2 Biomechanical Considerations
Spondylolisthesis is defined as a forward translation, or slip, of one vertebral body in relation to the adjacent caudal vertebral body (Fig. 15‑1a, b). Although spondylolisthesis can occur at any level in the spine, L4-L5 has been reported as the most common level. 7 , 14 According to the Wiltse 15 classification system, spondylolisthesis is often divided into one of six distinct categories defined by cause:
Type I: congenital/dysplastic: due to agenesis of the superior articulating facet
Type II: isthmic (spondylolytic): due to a pars interarticularis defect
Type III: degenerative: chronic instability secondary to articular degeneration
Type IV: traumatic: caused by a fracture or dislocation not involving the pars
Type V: pathologic: caused by a malignancy, infection, or other abnormal bone
Type VI: postsurgical (iatrogenic)
A common method of grading spondylolisthesis is by the severity of the slip, as defined by how far one vertebral body has migrated in relation to the adjacent vertebral body. The most common classification system is known as the Meyerding Grading System 16 and is defined by the severity of the slippage: Grade I: 1–25%; Grade II: 26–50%; Grade III: 51–75%; Grade IV: 76–100%; Grade V (also known as spondyloptosis): >100%, with one vertebral body completely over the adjacent vertebral body. Further, radiographic instability is defined as translational motion of one segment by more than 3 mm in the lumbar spine (5 mm at L5-S1) or angulation by more than 10° on flexion-extension radiographs. 17 Fig. 15‑2 depicts a case of mobile spondylolisthesis and facet joint degenerative changes at the segment of radiographic instability.
The exact cause of DS is still not well understood, but it is believed to be caused by disc degeneration and subsequent disc height loss, followed by degeneration of the facet joints and hypertrophy of the ligament flavum, resulting in instability and subluxation of the superior vertebra. The further degeneration processes may actually lead to secondary stabilization and auto-fusion of the spinal segment as facet arthrosis, osteophytes, and ossification of the intervertebral ligaments develop. 13 , 18 Multiple studies investigating the role of the facet joints in DS development report that it occurs more often in patients with sagittal orientation and a greater angle of the L4-L5 facet joints, 19 , 20 , 21 as the diminished anterior restraint results in anterior slippage of the vertebra. Love et al, however, argued that the sagittal orientation of the facet joints was the result of arthritic remodeling in older patients rather than the primary cause of DS. 22
Iatrogenic spondylolisthesis has been observed in patients after spinal fusion at the level above or below the fusion due to increased stress and accelerated degeneration. Iatrogenic spondylolisthesis can also be due to decompression procedures when a large extent of bone is removed, especially if a greater amount of the facet joints is removed. The study by Fox et al 23 found that preoperative anterior spondylolisthesis in patients undergoing decompression surgery for spinal stenosis was the single most important factor predicting postoperative radiological instability. Moelleken et al recommended limiting excision to one-third of each facet during decompression or adding fusion with instrumentation in patients with spondylolisthesis when a more extensive decompression is required. 24
15.3 Treatment Options
15.3.1 Nonsurgical Treatment Options
The indications for surgical treatment of DS have been reviewed by Herkowitz et al 25 and include: a) persistent or recurrent back and/or leg pain or neurogenic claudication, with significant reduction of quality of life, despite a reasonable trial of nonoperative treatment (a minimum of 3 months), b) progressive neurologic deficit, and/or c) bladder or bowel symptoms. Nonoperative interventions, however, are typically the first treatment of choice in patients with DS. Frymoyer 26 suggested the following treatment protocol: a) nonsteroidal anti-inflammatory drugs (NSAIDs); b) encouragement of aerobic conditioning; c) weight reduction, and d) management of osteoporosis. In the elderly population, however, there should be careful monitoring for gastrointestinal complaints and melena when administering NSAIDs and acetaminophen or cardiovascular complaints when prescribing COX-2 inhibitors. 27
Physical therapy (PT) is another very common conservative treatment modality for symptoms associated with DS, which helps teach patients methods of pain relief via activity modification and exercise. Other alternative treatment modalities, such as ultrasound, electrical stimulation, and dry needling can also be used. Finally, if patients fail a reasonable course of PT (4–6 weeks), then they may benefit in the short term from a course of epidural steroid injections. 10 There is little empiric evidence to support many of the common nonsurgical interventions for symptomatic elderly patients with DS; it generally is agreed, however, that nonoperative treatment should be attempted in most cases before surgical intervention is pursued. 27 , 28 Of the nonoperative options, none is known to be superior to the others, and all could have a role in the treatment of symptomatic patients. It is important to understand that for many patients, nonsurgical treatments may be used in combination or sequentially, and their use may change depending on the severity of symptoms and their change with time. 27
15.3.2 Surgical Treatment Options
Surgery is often considered when a patient fails to respond to nonoperative modalities, develops neurologic deficits, or when the patient’s symptoms are debilitating.
Surgical treatment of DS fulfills two primary objectives: decompression of the neural elements and stabilization, if indicated. The first objective is to decompress the neural structures in order to relieve spinal stenosis and neurogenic claudication symptoms. A laminectomy with or without lateral recess and foraminal decompression is one option. A laminotomy preserving the vertebral arch is another method to achieve a decompression. The second objective is internal stabilization via fusion. A fusion is performed to prevent any further slip from developing between the vertebrae as well as stabilizing the associated degenerative disc and arthritic facets, often times for improving back pain and preventing possible instability. Traditional factors favoring fusion include: improved spine stability, minimization of long-term back pain from the operated degenerative levels, and concern for recurrent leg pain from progression of the spondylolisthesis in the absence of fusion. 29 Decompression and fusion is becoming the most common surgical technique for the management of DS. 30 Fusion options for DS are variable and can include a noninstrumented or an instrumented posterolateral fusion (PLF), in addition to an interbody fusion via various approaches: anterior lumbar interbody fusion (ALIF), lateral interbody fusion (LIF), posterior lumbar interbody fusion (PLIF), and transforaminal lumbar interbody fusion (TLIF). Other surgical options for patients may include a minimally invasive decompression with or without fusion, dynamic stabilization, and interspinous spacers.
15.3.3 Benefits and Risks
The benefit of surgical intervention in patients with lumbar DS is twofold. One, the neural elements are decompressed, which can improve neurologic morbidity. Two, the spondylolisthesis can be stabilized to improve mechanical back pain or prevent progressive instability. Decompression compared with instrumented fusion may be a more appropriate treatment option in the aging patient population due to shorter operative times and reduced blood loss, but there is increased risk of developing instability. The risks and benefits of each specific surgical approach are further elucidated in an excellent summary by Eismont et al. 31 The Spine Patient Outcomes Research Trial (SPORT) demonstrated that surgery was superior to nonoperative care for the management of lumbar DS, though this study was not focused on the aging population. 1 Rihn et al 32 evaluated the effectiveness of surgery for lumbar stenosis and DS in the octogenarian population. They found that surgery offered a significant benefit over nonoperative treatment in patients at least 80 years of age (p < 0.05), with no significant increases in the complication and mortality rates compared with younger patients (p > 0.05).
Proceeding with any type of surgical intervention in the aging population involves several concerns, including an increased risk for complications such as pseudoarthrosis, hardware failure, or loosening secondary to poor bone quality, as well as an increased number and severity of comorbidities, with a resultant higher rate of perioperative morbidity. 31 In their analysis of a subset of Medicare patients treated for lumbar spinal stenosis and/or spondylolisthesis via fusion, Ong et al 33 found that older patients may require more extensive postoperative care and may be more predisposed to certain types of surgical complications. Becker et al 34 retrospectively evaluated 195 patients over the age of 70 who underwent spinal fusion with pedicle screws and rod instrumentation with or without intervertebral cages and reported a 14.7% major complication rate and 18.9% minor complication rate. Benz et al 35 reviewed 68 patients aged 70 years and older who underwent lumbar decompression with or without fusion and reported a 40% total complication rate: 12% major and 28% minor complication rates, respectively. The early mortality rate was 1.4% in their series. The authors noted that arthrodesis with or without instrumentation was significantly associated with complications. Carreon et al 36 found complications in 78 patients in their series of 98 patients over the age of 65 years undergoing posterior decompression and fusion for degenerative disease of the spine. Twenty-one patients had at least one major complication, and 69 had at least one minor complication. The most common major complication was wound infection (10%), while urinary tract infection was the most common minor complication (34%). Complication rates increased significantly with older age, increased blood loss, longer operative time, and the number of arthrodesis levels. In their series of 166 patients aged 65 years or older undergoing lumbar decompression and fusion with (n = 75) or without (n = 91) instrumentation, Cassinelli et al 37 reported a 3% major complication rate and 30.7 and 31.9% minor complication rates in patients undergoing decompression with or without fusion, respectively. The authors also noted that decompression associated with fusion of four or more segments significantly increased the occurrence of major complications. Hayashi et al 38 compared the perioperative complication rates between patients under and over the age of 80 years undergoing surgery for lumbar degenerative disease. They found major complications in 16% of patients in the ≥ 80 group and 9% of patients in the < 80 group. Medical complications occurred in 21% of patients in the ≥ 80 group and 16% of patients in the < 80 group. Likewise, surgery-specific complications occurred in 37% of patients in the ≥ 80 group and 19% of patients in the < 80 group. Although the incidence of complications was not significantly different between the two groups, patients in the ≥ 80 group had a higher tendency towards complications. Balabaud et al 21 was one of the first to evaluate the morbidity and mortality of spine surgery in patients 80 years of age or older in a large cohort. Patients underwent a posterior decompression with or without spinal instrumentation. The purpose of their study was to determine whether preoperative and perioperative factors correlated with morbidity and mortality. After a diagnosis of spinal stenosis, DS was the second most common diagnosis in 45 of their 121 patients. For DS and/or preoperative assessed instability, an instrumented fusion or dynamic stabilization was always performed. They found an average hospital stay of 11.3 ± 8.1 days (range, 7–71 days), and significantly increased average blood loss with instrumentation (538 vs. 280 ml, p < 0.0001). Average operative time was 103 ± 38 min, and, again, increased significantly with instrumentation (131.2 vs. 84 min, p = 0.003). Fusion occurred in 30 out of 37 patients (81%) after a minimum of 1 year. With regard to complications, they found major complications in 16 of 121 patients (13%), with the most common ones being from wound infection (4%), followed by epidural hematoma and neurologic deficit (3.3% each) and either new onset of cardiac arrhythmia or pneumonia and respiratory distress (2.4% each). Less than 2% of patients developed any of the following: congestive heart failure, thromboembolic disease, renal failure, pulmonary embolus, or syndrome of inappropriate antidiuretic hormone (SIADH). Minor complications occurred in 29.7% of patients, and most commonly was confusion (13%), urinary retention (8%), and urinary tract infection (5%). Other minor complications (less than 2.5% each) included ileus, hyponatremia, hypokalemia, digestive tract infection, and morphine intoxication. Although their 4% wound infection rates were similar to those reported in the literature, the authors discovered that the infecting organism appeared unique to the elderly population, which was primarily due to gram-negative bacteria: E coli (two patients) and E faecalis (two patients), with only one patient suffering from S aureus.S aureus tends to be the more causative agent for infections within a younger population. This indicates that wound infections in the elderly are more commonly caused by the urinary tract or fecal organisms.
Lieber et al 39 studied postoperative complications and compared patients > 80 years old (n = 227) with a typical age cohort 45–65 years old (n = 2248) undergoing a single-level lumbar fusion for spondylolisthesis. They found a difference in the preoperative characteristics and comorbidities between the younger and older age cohorts. The older patient cohort had more preoperative comorbidities, including a lack of independent functional health status before surgery (p < 0.001), severe chronic obstructive pulmonary disease (p < 0.020), and hypertension requiring medication (p < 0.001). They also found a significantly greater morbidity among the > 80 years old cohort regarding urinary tract infection (p = 0.008) and intraoperative and postoperative transfusions (p < 0.001). Interestingly, there was significantly greater morbidity among the younger cohort regarding cardiac arrest requiring cardiopulmonary resuscitation (p = 0.043). Oldridge et al 40 identified 80–85 years as a threshold for a dramatic increase in morbidity and mortality.
Raffo and Lauermann 41 reported on their series of 20 patients aged 80 years or older undergoing lumbar spine surgery. They reported a 35% major complication rate with no mortalities. Ragab et al 42 reviewed the outcomes of patients over the age of 70 years who underwent surgery for spinal stenosis. They found a minor and major complication rate of 8% and 2%, respectively. Takahashi et al 43 found an overall complication rate of 34.3% in patients 70 years and older undergoing TLIF procedures for spondylolisthesis. Vitaz et al 44 reported on 65 patients with lumbar stenosis at least 75 years of age who underwent lumbar decompression with and without spinal fusion and reported a 10% major complication rate and 27% minor complication rate—this in comparison to a major complication rate of 7.7% and minor complication rate of 11.5% reported by Wang et al 45 in their series of 26 patients 85 years and older undergoing lumbar spine surgery. They found that operative time of longer than 180 minutes (p=0.0134) was associated with complications.
In the study by Glassman et al 46 of 85 patients over the age of 65 years undergoing lumbar spine surgery, complications occurred in 27 patients (31.8%). Complications included seven incidental durotomies, five ileus, four wound infections, three urinary tract infections, three mental confusions, and five others. This was compared to a rate of 11 (11.8%) complications in patients aged younger than 65 years (p = 0.001). Fourteen patients (16.5%) over the age of 65 years underwent a subsequent revision, compared with 17.2% in the under 65 years group (p= 0.90). Revision procedures were a repair of nonunion in three patients, an adjacent-level fusion in 10 patients, and a repeat decompression in one patient in the older population. Sansur et al reviewed 10,242 adults with DS and isthmic spondylolisthesis (IS) from the morbidity and mortality index of the Scoliosis Research Society. 47 The rate of total complications for treatment of DS and IS was 9.2% in 7.9% of total patients studied. On univariate analysis, the complication rate was significantly higher in patients with high-grade spondylolisthesis, with a diagnosis of DS, and in older patients. The surgical approach and history of previous surgery were not significantly correlated with increased complication rates. On multivariate analysis, only the grade of spondylolisthesis was significantly associated with the occurrence of complications.
Minimally Invasive Surgery
Rosen et al 48 reviewed their outcomes of minimally invasive (MI) lumbar decompression on patients at least 75 years of age and reported a 1% major complication rate and a 30% minor complication rate. Rodgers et al 49 found complication rates, blood loss/transfusion rate, and hospital stay to be significantly (p < 0.0001) lower following MI interbody fusion compared to open PLIF in patients 80 years. Lee et al 50 reported overall clinical success in 88.9% of patients, with a low rate of complications (7.4%) at a minimum follow-up of 36 months. The authors performed MI-TLIFs in patients aged 65 years and older and found significant improvements in Visual Analog Scale (VAG) and Oswestry Disability Index (ODI) scores (p = 0.001), with a pseudoarthrosis and adjacent segment disease rate of 22.2% and 44.4%, respectively. There were no reoperations in their series, and clinical outcome measures were successful in all patients without a solid fusion.
15.4 Pitfalls, Complications, and Avoidance
Surgical treatment is effective in improving the quality of life in the aging patient population, but due to significant comorbidities and an increased risk of complications, treatment of DS requires not only careful selection of surgical approach but also careful management of potential complications and adaptation of preventative measures in order to minimize them. 51
15.4.1 Identify Instability
Care should be taken to identify patients who are unstable preoperatively or may be rendered unstable by the decompression to avoid iatrogenic progression of the spondylolisthesis leading to reoperation. Sengupta and Herkowitz 52 determined the indications for performing fusion with instrumentation based on preoperative and intraoperative factors. The authors recommended instrumented fusion in the following clinical situations: a) to prevent progression of listhesis if the preoperative disc height is > 2mm; b) when correction of deformity is performed with presence of kyphosis; c) to assure that fusion is achieved when instability is > 5 mm; d) listhesis of > 50%; e) when revision decompression is performed and requires additional facetectomy; f) listhetic or symptomatic adjacent segment degeneration is present; g) bilateral facet excision of > 50%; h) reduction of listhesis is performed and disc height is restored. Blumenthal et al 53 reported a 37.5% reoperation rate at a mean follow-up of 3.6 years for pain caused by instability at the index level following decompression only for Grade I lumbar spondylolisthesis. Similar reoperation rates (34%) were confirmed by Ghogawala et al 54 for patients undergoing decompression alone to address instability, but the authors also reported 14% revision surgery rates in the fusion group due to symptomatic adjacent-level degeneration. Appropriate selection of patients that would benefit from fusion can help avoid the need for revision surgery due to instability.