4 Surgical Decision-Making in the Aging Population
The number of older adults who require spine surgery has increased significantly in the past decade. Along with this increase in patient population, there is also a corresponding increase in the accompanying comorbidities and deterioration of anatomical integrity of the spine, which in turn necessitate unique considerations in surgical approach, possible complications, and preoperative screening. This chapter provides a comprehensive review of the important effects of aging on surgery, necessary components of the preoperative screening that needs to be implemented for this population, and a discussion on how to tailor spine surgery to the older adult in the context of their overall health and preoperative risk factors. Specifically, the timing and selection of specific surgeries for older adults will be discussed for surgeries of both the cervical and lumbar spine. Risk factors, suboptimal patient responses, and postoperative complications, along with possible changes in surgery to minimize these complications will also be discussed. While a preoperative workup is performed for all patients undergoing spine surgery, older adults require a more comprehensive evaluation that corresponds to their unique constellation of potential complications and comorbidities. In this chapter, we discuss the important preoperative considerations, such as patient frailty, mental status, and social support and advocate for the implementation of a standardized evaluation for these factors before major spine surgery. Ultimately, this chapter seeks to provide a better understanding of the risks and complications that accompany spine surgery in aging patients as well as to suggest possible alterations in surgical approach and preoperative workup to minimize these complications and optimize patient outcome.
Older adults undergoing major spine surgery present a unique constellation of risk factors, comorbidities, and potential complications that must be considered.
Aging patients manifest rapid deterioration following cervical spondylotic myelopathy (CSM), thereby necessitating prompt surgical intervention for optimal results. Withholding spine surgery from this population of patients may increase morbidity due to rapid disease progression.
Dysphagia is a major complication of anterior cervical spine surgery in the older adult.
Minimally invasive spine surgery (MIS) may be a safer alternative for aging populations undergoing surgery of the lumbar spine.
Preoperative workup in older adults should include a thorough evaluation of the patient’s cardiovascular, renal, and pulmonary function, in addition to a comprehensive assessment of the patient’s frailty, nutritional status, social support, and mental status.
4.1 Introduction: The Changing Landscape of Spine Surgery
The population of spine surgery patients has changed significantly during the past two decades; as the proportion of the U.S. population over the age of 62 increases (by 21.1% from 2000 to 2010), the prevalence of spinal conditions is also on the rise. 1 As such, the demand for surgical interventions of the spine to treat disorders ranging from degenerative spinal stenosis to spinal deformities has increased in the aging population throughout the last few decades. 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 Older adults accounted for the fastest growth in the population of patients undergoing surgeries of the lumbar spine during the past few decades. 2 , 4 A similar trend is also seen in patients undergoing cervical spine surgeries. For instance, the adjusted rate for older adults undergoing cervical spine fusions rose by 206% from 1992 to 2005. 2 , 9 , 10
This increased demand for spine surgery in the aging population necessitates an understanding of age-related changes in the spine, their effects on patients’ responses to surgery, and their impact on surgical decision-making. To this end, we will explore the complications associated with surgeries of both the cervical and lumbar spine in the elderly as well as the preoperative workup recommendations for this patient population. Lastly, we will examine bone mineral density (BMD) workup for spinal fusions and explore the best management strategies prior to elective surgeries. As we progress through this chapter, it will hopefully become evident that the aging patient may go through several important changes and could respond differently to surgical operations than a younger individual, thus necessitating careful consideration of surgical decisions in spine surgeries of the older adult.
4.2 Surgical Complications and Aging
Aging patients, which will henceforth refer to those over 65 years of age, often have both worse outcomes and increased incidence of complications following spine surgery when compared with younger cohorts. 11 As such, it is not surprising that the aging population also has the highest risk of mortality associated with surgeries of the spine. 1 However, this picture is complicated by the increased incidence of comorbidities in older adults, which can confound the impact of age on postoperative surgical complications. 12 , 13 Furthermore, reports have indicated that withholding surgery from an older adult can actually result in increased morbidity. 9 , 12 As such, the relative risks and benefits of surgical intervention must be comprehensively assessed for each patient before proceeding. Thus, it is imperative that we explore the relationship between age and postoperative complications associated with surgeries of the cervical and lumbar spine.
4.2.1 Cervical Spine
One disorder that exhibits increasing prevalence with age is cervical spondylosis, which can lead to cervical myelopathy, characterized by symptoms such as difficulty in gait and numbness and/or weakness of the hands. 14 , 15 , 16 Untreated cervical spondylotic myelopathy (CSM) has a poor natural history and severely impairs both ambulatory functions and quality of life. 1 , 14 , 15 , 16 Although surgical decompression has been shown to improve patient symptoms, several studies have suggested a higher complication rate in patients of advanced age, generally over the age of 65. 1 A 2008 study comparing the surgical outcomes of elderly patients undergoing decompressive surgery for cervical spondylotic myelopathy with those of younger cohorts showed that the older population had a 38% complication rate, compared to a 6% complication rate in the younger group. 8 Similarly, a recent study, which analyzed 5,154 elderly patients and 30,808 nonelderly patients found that elderly age significantly increased the risk of complications following anterior cervical discectomy and fusion (ACDF) and posterior fusion procedures for the treatment of CSM. 14 The elderly group had a 22.26% complication rate after ACDF surgery (compared with a 14.66% complication rate in the nonelderly group, p-value < .001) and a 32.34% complication rate after posterior decompression (compared with a 27.85% complication rate in the nonelderly group, p-value = .0084). 14 Common complications include dysphagia, nerve injury, postoperative pain from paraspinal muscle injury, epidural hematoma, and pulmonary distress. 1 , 2 , 3 , 4 , 5 , 7 , 8 Some severe complications reported for older adults undergoing surgery for CSM include delirium, dementia, and nerve injury. 1 , 2 , 3 , 4 , 5 , 7 , 8 However, it is worth noting that age is not the only factor that increases risks for complications. Medical comorbidities such as diabetes and obesity also increase the risk of adverse outcomes. 1 , 2 , 3 , 4 , 5 , 7 , 8 , 11 , 17 Since older patients tend to have a greater number of comorbidities than younger cohorts, it’s possible that the comorbidities themselves may account for the increased complication rates, thus serving as a confounder in the relationship between age and postoperative complications.
The literature on this topic, while conflicted, seems to support a role for surgical intervention for CSM in older adults, with several groups reporting no effect of age on postoperative complications for surgical treatment of CSM after adjusting for baseline Japanese Orthopedic Association (JOA) scores. 2 , 3 , 4 , 5 , 8 , 9 , 10 A meta-analysis comprised of 2,868 patients reported no significant difference in the incidence of complications following surgery for CSM between the elderly and nonelderly groups. 9 Similar results have also been reported by other groups, one of which showed that octogenarians had similar rates of postoperative complications as a younger cohort following decompression surgery. 12 However, it was noted that the elderly age group exhibited a rapid deterioration following CSM onset, necessitating prompt surgical intervention for optimal results. 12 Thus, withholding surgery from older adults from fear of possible complications may actually increase morbidity due to the rapid disease progression in this age cohort. 13 While the relative risks and complications of any surgery must be weighed before proceeding, there is clearly a role for surgical intervention for the alleviation of CSM symptoms and improvement in quality of life in the aging population. However, it is important to be cognizant of the possible complications and take measures perioperative to minimize their risks, as will be discussed in a future section.
4.3 Dysphagia in Older Adults and Effect on Cervical Surgery
Another possible complication of cervical surgery is dysphagia, especially in older adults. Older adults are inherently more vulnerable to dysphagia due to the increased comorbidities, such as gastroesophageal reflux disease (GERD). 18 , 19 , 20 Of note, the prevalence of dysphagia in persons above the age of 50 in nursing homes is estimated to be anywhere from 40 to 60% in the Midwestern United States. 18 In addition to GERD, other comorbidities that may predispose an individual to developing dysphagia include cerebrovascular accidents, Parkinson’s Disease, and Amyotrophic Lateral Sclerosis (ALS), all of which are more prevalent in the aging population. 18 , 19 , 20 Since functional dysphagia requires integrity of the oropharynx, anything that compromises that integrity or associated nervous innervation of the oropharynx can lead to dysphagia. 18 As such, dysphagia is a well-established complication of anterior cervical spine surgery. In particular, a recent report demonstrated certain risk factors, such as female gender, the utilization of anterior cervical plates, multiple surgical levels, surgery at C3/4, and using human bone protein rhBMP-2, are associated with an increased risk for developing dysphagia after cervical surgery. 19 , 20 While more studies are required to establish more comprehensive risk factors in cervical surgery associated with postoperative dysphagia, it is well established that cervical anterior spine surgery is an important contributor to the development of dysphagia. Thus, it is important that a set of guidelines concerning the risk factors for developing dysphagia be developed to guide the instrumentation and approach of cervical spine surgery for older adults.
4.3.1 Lumbar Spine
Lumbar spinal stenosis is the most common degenerative condition of the aged spine, often presenting with symptoms of neurogenic claudication. 1 , 21 , 22 Surgical interventions involving lumbar decompression, instrumented lumbar fusion, and minimally invasive methods have been shown to significantly improve patients’ quality of life. 1 , 21 , 22 , 23 However, as with decompressive surgeries of the cervical spine, lumbar decompression in older adults is complicated by dissenting opinions concerning associated complications. 1 , 21 , 22 Specifically, there is disagreement in the literature concerning whether increased age is significantly correlated with increased complications and worse outcomes. 1 , 21 , 22 While some studies have reported increased complications following surgery for degenerative lumbar spinal stenosis (DLSS), the vast majority of literature suggests that confounding factors such as operative time and blood loss were actually more influential than age in predicting surgical outcomes. 1 , 12 , 21 , 22 Indeed, both of these factors were found to be predictive of systemic and wound complications in a retrospective review of 88 elderly patients who underwent DLSS surgery.14 This result was corroborated by the results from a large European spine registry, which comprised 1,764 elderly patients undergoing DLSS surgery. In this case, aspirin use and blood loss were predictive of the incidence of postoperative complications. 1 Of note, a multicenter cohort study in Switzerland in 2010 indicated that patients who are 80 years or older can expect a clinically meaningful outcome from decompressive surgery for DLSS, with notable improvement in quality of life, as measured by EuroQol-5 Dimension (EQ-5D) quality of life questionnaires. 21 Furthermore, no statistically significant difference in complications were reported between the older and younger cohorts.14 Even patients aged 90 years and older showed no correlation between DLSS outcomes/complication rates and age.18 Rather, the odds ratio for comorbidity in this cohort was 9.20 (p = 0.040). A strong correlation with postoperative complications were associated with blood loss, operation time, and days spent in the intensive care unit.18 Similar results have been reported abundantly, indicating that advanced age in itself is not linked to major complications in DLSS surgeries. 1 , 12 , 21 , 22 , 24
Given the clear impact of operation time and blood loss on surgical outcomes and complication rates in older patients, literature suggests that minimally invasive surgery (MIS) may be ideal for patients of advanced age. 11 , 24 The decreased blood loss, minimal disruption of the anatomy, and reduced pain associated with these procedures render them a viable alternative to conventional decompression surgery for the aging population. 11 , 24 Recent studies attest to the efficacy of minimally invasive surgeries in DLSS treatment; a study performed on 57 patients over the age of 75 undergoing DLSS MIS showed significant improvement in patient function and quality of life, as measured by Oswestry Disability Index scores and 36-item Short Form Survey scores. 1 , 24 Furthermore, no major complications were noted in the study. As these results suggest, MIS is a safe and effective alternative to conventional, open decompressive surgeries for the treatment of DLSS in older adults. 1 , 24
4.4 Recommendations for Preoperative Workup in Older Adults
Preoperative workup for spine surgery in older adults must include a comprehensive review of systems as well as identification of any condition that may increase the risk of perioperative complications. We will explore here the major elements of the cardiovascular, pulmonary, and renal system workups in the geriatric population. In addition, we will also explore the impact of BMD on the outcomes of spinal fusion procedures. While meticulous preoperative workup is necessary for all patients undergoing major spine surgery, special considerations are necessary for older adults. Specifically, important factors that may affect patient outcome in this population include frailty, nutrition, social support, and mental status.
Given that over 50% of patients above 70 years of age have cardiovascular disease upon autopsy, cardiovascular complications and measures to reduce their risk should be considered before any surgery. 11 As such, a preoperative workup in older adults should always include a thorough medical history, surgical history, cardiac physical examination, and baseline electrocardiogram assessments to evaluate the status of the patient’s cardiovascular health and to detect possible cardiovascular risk factors. 12 Specifically, patient reports of dyspnea or syncope should alert the surgeon to possible previous undiagnosed myocardial infarctions or arrhythmias and should be investigated before proceeding with surgery. 11
To determine a patient’s risk for perioperative cardiovascular complications, surgeons can use the Revised Cardiac Risk Index, which was published in 1999 from a study comprised of 2,893 patients and validated in 1,422 patients who underwent major noncardiac surgery. 12 , 25 Specifically, six risk factors were identified which had significant correlation with postoperative cardiovascular complications, namely, histories of ischemic heart disease, congestive heart failure, cerebrovascular disease, diabetic insulin therapy, chronic kidney disease (as defined by a preoperative creatinine level of 2mg/dL or higher), and high-risk surgeries. 12 , 25 The predictive power of these risk factors can be appreciated by examining the risk for major cardiovascular complications in the context of the number of predictors present. 13 A patient with zero of the six risk factors only has a 0.4% risk of having a significant cardiovascular complication, where as a patient with three or more risk factors has over an 11% risk of having a major cardiovascular complication. 12
4.4.2 Pulmonary System
Aging is often accompanied by a decline in respiratory function and reserve capacity, which can often give way to chronic obstructive diseases. 12 Indeed, airway obstruction has been noted to complicate spine surgery in the older adult patient. In a case series of 100 patients aged over 70 years, almost 40% exhibited abnormal pulmonary function. 13 Thus, as part of preoperative workup for older adults, pulmonary function tests such as the one-second forced expiratory volume (FEV1) should be performed. 12 Furthermore, arterial blood gas concentrations should also be determined to detect possible loss of pulmonary reserve capacity. 12 A preoperative PCO2 concentration of greater than 45 mm Hg has been associated with an increased occurrence of postoperative pulmonary complications. 12 This is especially important if a ventral surgical approach is being considered or if the patient manifests symptoms of pulmonary compromise, such as dyspnea, orthopnea, or poor exercise tolerance. 12 If clear pulmonary impairment is present, however, operations that require thoracotomy should be avoided. 12 While there is no clearly defined guidelines of ideal pulmonary function prior to spine surgery, it is widely agreed that optimal preoperative respiratory function is associated with better patient outcomes and reduced rates of postoperative complications. 12