Cardiovascular System

It has been reported that at autopsy 50% of patients older than 70 years of age have significant cardiovascular disease. The cardiac risk index, a commonly used assessment tool, incorporates myocardial infarction in the past 6 months, uncompensated congestive heart failure, aortic stenosis, nonsinus rhythm greater than five premature ventricular contractions per minute, diabetes mellitus, and age older than 70 years as major risk factors for postoperative cardiac complications of noncardiac surgery⁴ (Box 131-1).

The basic cardiovascular workup in patients older than 65 years of age should include a thorough history and physical examination and a baseline electrocardiogram. Myocardial infarction, unaccompanied by recognized symptoms, occurs in as much as 10% of elderly patients.⁵ Reports of syncope or dyspnea are the most suggestive symptoms of this event. Peripheral vascular disease is often present with coronary artery disease and may complicate the diagnosis of neurogenic claudication. Absent peripheral pulses or a history of transient ischemic attacks or stroke should lead to a more comprehensive cardiac workup.

In patients with unstable angina, elective spinal surgery is clearly contraindicated. Patients with well-controlled stable angina, however, have only a slightly increased risk for perioperative cardiac complications, and may therefore be considered for surgery.⁶ Moderate to severe congestive heart failure is associated with a significant perioperative risk.^7–9 Jugular venous distention and peripheral edema are suggestive signs, whereas a history of dyspnea on exertion and orthopnea are symptoms of a more severe form of congestive heart failure.

Respiratory System

Elderly patients are at particular risk for perioperative pulmonary complications for several reasons. Decline in pulmonary function and reserve, underlying chronic obstructive disease and bronchitis, lack of mobility or bed rest associated with spinal surgery, and airway obstruction all can lead to significant morbidity or mortality for these patients.^10,11 In a series of 100 patients older than 70 years of age, approximately 40% of those without a history of lung disease had abnormal pulmonary function.¹² Pulmonary function tests (spirometry) should be obtained for patients older than 65 years of age or with a history of obstructive lung disease if a ventral approach is being considered.¹³

A forced expiratory volume in 1 second of less than 50% of the predicted value does not suggest an increased risk of postoperative mechanical ventilation, but combined with dyspnea at rest and arterial hypoxemia, it is an established risk factor.¹⁴ Room air arterial blood gas should be tested in elderly patients with lung disease, as well as those with a history of shortness of breath, poor exercise tolerance, orthopnea, or excessive smoking. Elevated partial pressure of carbon dioxide (Pco₂) reflects a loss of pulmonary reserve. A preoperative Pco₂ of greater than 45 mm Hg is associated with an increased incidence of postoperative pulmonary complications,¹⁵ and patients with a Pco₂ of greater than 50 mm Hg often require a period of postoperative mechanical ventilation.¹⁶

There is no well-defined lower limit of pulmonary function established by any criteria that strictly contraindicates surgery. Optimizing preoperative function certainly helps decrease the overall risks associated with lung disease. Equally important is an aggressive postoperative care plan, including early mobilization, incentive spirometry and coughing exercises, chest physiotherapy with postural drainage and nasotracheal suction, and use of bronchodilators and mucolytics as needed. Finally, an operative plan that avoids thoracotomy in patients with significant pulmonary compromise is well advised.

Renal System

Decline of renal function in the elderly is more consistent than that of other organ systems.¹⁷ In geriatric patients, serum creatinine levels may be artificially low because of decreased production, caused by a shrinking muscle mass. For this reason, creatinine clearance is the preferred test for patients suspected of having significant renal disease. The effect of chronic nonsteroidal anti-inflammatory drug (NSAID) use on the kidney may also contribute to the decline in renal function with advancing age. These drugs can decrease renal blood flow, adding to an already diminished glomerular filtration rate.¹⁸ This has clinical significance in the perioperative patient because water homeostasis may be difficult to achieve in elderly patients, leaving them prone to hyponatremia and volume overload. The use of isotonic fluids, restriction of free water, and careful administration of diuretics may be helpful.

Osteoporosis

Osteoporosis is a state of decreased density of mineralized bone. The biochemical makeup and structure of osteoporotic bone are normal, but the volume density of bone is below normal. Bone mass reaches its maximum in the third decade of life and then begins to decrease.²¹ At its peak, the maximum surface area of bone crystals in an adult is estimated to be 100 acres.

Bone is a biphasic material consisting of an organic component, osteoid, which is a matrix of collagen and other proteins, and an inorganic component consisting of hydroxyapatite. The mineral component of bone accounts for the majority of its mechanical strength. Bone is constantly being remodeled by the opposing actions of osteoblasts and osteoclasts. When the balance falls in the direction of osteoclastic activity, net bone resorption occurs. Factors that are predisposed to bone resorption include loss of estrogen and androgens, corticosteroid use, alcohol and tobacco use, and poor nutrition. Bone mineral loss is also associated with increasing age in both men and women. These factors cause depletion of elemental calcium at a rate up to between 30 and 40 mg/day from a peak mass of 1000 g.

Loss of bone mineral content predominantly occurs from trabecular bone because of its increased baseline metabolic activity and greater surface area compared with cortical bone. Hence, structures formed of trabecular bone are more susceptible to osteoporosis.²² In vertebral bodies, trabecular bone accounts for 90% of axial load-bearing resistance. As a result of primary osteoporosis, elderly people may sustain vertebral compression fractures with minimal trauma. Current recommendations for the medical management of osteoporosis are summarized in Box 131-2.

Bone densitometry has been shown to predict risk of osteoporosis.²³ Currently, two methods are used to evaluate bone density. Dual-energy radiography measures area density (g/cm²) of the spine. This test is simple and accurate and carries a low radiation dose. It is also well tolerated, with a procedure time of 10 to 15 minutes. Quantitative CT scanning is a measurement of true density (g/cm³) through a cross-sectional view of the vertebral body. The precision of this test is excellent, but it can be compromised by patient positioning and movement. The small increase in accuracy provided by this test over dual-energy radiography may not justify the expense, discomfort, and added radiation dose.²⁴ A bone mineral density by dual-energy radiography of 1 g/cm² carries a fracture risk over time of 32%, whereas a density of less than 0.8 g/cm² carries a risk of 50%.^25,26

Presence of osteoporosis may affect choices regarding instrumentation and fusion for patients indicated for spinal surgery. Obtaining adequate purchase in patients with significant osteoporosis may require using longer constructs to distribute forces and increase numbers of purchase points. On the other hand, some patients with osteoporosis may be more appropriately treated with uninstrumented spinal fusion or with operative approaches that avoid fusion entirely.

The effect of osteoporosis on vertebrae adjacent to areas of spinal fusion must also be considered. In elderly or osteoporotic patients in whom long fusion constructs are unavoidable, the long-term stability of adjacent vertebral segments is a significant concern. Particularly for areas of high mechanical stress, such as fusions stopping at the thoracolumbar junction, consideration should be given to prophylactic enhancement of the strength of vertebrae adjacent to long fusion constructs through procedures such as vertebroplasty²⁷ (Fig. 131-1).

FIGURE 131-1 A and B, Myelograms of a 76-year-old woman who had undergone a prior fusion from L4 to the sacrum with clinical success. Adjacent-segment disease had led to a laminectomy above her fused segment at L2 and L3, with resulting segmental instability. At the time of her appearance, she suffered from intractable leg and back pain with severe functional limitations. C and D, Patient underwent a successful ventral/dorsal reconstruction with the revision laminectomies and fusion from L2 to the sacrum. Because of the patient’s underlying osteoporosis and advanced age, adjacent vertebral levels were augmented with vertebroplasty. Note postoperative compression fracture of L1 vertebra on lateral view. This fracture did not collapse beyond the appearance shown and remained asymptomatic throughout the postoperative course.

Osteoporotic Compression Fractures

The most common type of spinal fracture in the elderly patient is the vertebral compression fracture. These fractures occur not only with higher-energy mechanisms but often with bending, lifting, or even during normal activity. Management should be directed primarily toward pain control. It should also be recognized that such low-energy fractures often are the first indication of underlying osteoporosis, and patients should be started on appropriate medical therapy (see Box 131-2).

Elderly patients with osteoporotic compression fractures who are requiring bed rest or significant narcotic analgesia, or for whom disabling pain has persisted over 4 to 6 weeks, may be candidates for percutaneous stabilization procedures, such as vertebroplasty or balloon-assisted vertebroplasty (kyphoplasty).²⁸ However, results of two randomized, controlled trials of vertebroplasty suggest limited benefit to such procedures.^29,30 This has led some insurers and academic organizations such as the American Academy of Orthopaedic Surgeons to recommend limits on the use of these procedures. At this time, evidence-based medicine guidelines for vertebroplasty must include the results of these studies, which represent the highest level of medical evidence available on this condition.

Degenerative Lumbar Spondylolisthesis

Degenerative spinal stenosis results from neurologic impingement by the disc, facet joints, and spinal ligaments. Kirkaldy-Willis et al.²⁴ proposed that biochemical and biomechanical changes associated with age cause increased mobility at a spinal segment, leading to osteophyte formation and joint hypertrophy that reduce spinal canal diameter and local stiffness. The increased joint laxity resulting from facet degeneration leads in some cases to spondylolisthesis between adjacent vertebrae.

Two prospective, randomized, controlled trials support treatment of patients with degenerative lumbar spondylolisthesis with laminectomy and dorsal fusion.^31,32 Several studies have demonstrated increased fusion rates with pedicle screw instrumentation, and further studies have shown better clinical outcomes in patients who achieve solid arthrodesis.^33–35

Despite those results, use of instrumentation has not been convincingly shown to improve clinical outcomes after fusion for patients with degenerative spondylolisthesis.^32,36,37 Avoiding instrumentation when performing fusion in elderly, osteoporotic patients with degenerative spondylolisthesis may thus be a reasonable option, particularly when facets are oriented relatively in the coronal plane and segmental instability is not present.

Degenerative Scoliosis

Degenerative scoliosis, unlike idiopathic scoliosis, is an acquired disorder of adult patients. Patients often present with symptoms similar to those of degenerative lumbar stenosis, although for some patients the deformity itself becomes an issue. Nonoperative treatment modalities include physical therapy, muscle relaxants, and NSAIDs. Surgical options include neurologic decompression through laminotomy or laminectomy. Spinal fusion may or may not be appropriate, depending on the patient’s presentation, health status, and expectations from surgery.^38–41 There are conflicting reports regarding the need for spinal stabilization after decompression for degenerative scoliosis.^38–4042 Patients without lateral listhesis between adjacent vertebrae may be appropriately treated with laminectomy without fusion.

Patients of advanced age with significant scoliotic curves may not be appropriate candidates for the large reconstructive fusion procedures required to treat their spinal deformity. Judiciously selected nerve root blocks with isolated unilateral foraminotomies may be used to good effect in such patients with limited risk of deformity progression (Fig. 131-2). Elderly patients for whom stabilization is required will benefit from efforts to limit the extent of surgery, including use of dorsal (posterior) or transforaminal lumbar interbody fusions in favor of ventral approaches (Fig. 131-3).

FIGURE 131-2 A–C, A 78-year-old woman with advanced osteoporosis reported after instrumentation and kyphoplasty with laminectomy for an osteoporotic burst fracture. She had an adjacent fracture of L2 with hardware failure at L3. D and E, After Smith-Petersen osteotomy and transforaminal lumbar interbody fusion at L3-4 and dorsal fusion from T10 to L5, the patient experienced significantly improved function and reduced pain. This result has been maintained at 4-year follow-up. Note augmentation of upper instrumented vertebra and first cranial level.

FIGURE 131-3 A, An 81-year-old man with a history of well-controlled Parkinson disease presented with rapid failure above a fusion from L2 to the sacrum. The fusion itself was healed. B, After pedicle subtraction osteotomy of L2, adequate sagittal balance is restored. Obtaining good sagittal alignment is a key element in achieving long-term success in longer fusions among older patients.

Cervical Degenerative Disease

Elderly patients with cervical degenerative disease and spinal stenosis also present a treatment problem significantly different than younger patients with similar conditions. Concerns over bone quality and physiologic ability to withstand large reconstructive surgery again play a significant role in decision making.

Ventral decompressive surgery by multilevel corpectomy may prove difficult in this patient population. Although ventral decompression may be appropriate on a neurologic basis because of kyphotic alignment of the cervical vertebrae,⁴² reduced mechanical strength of vertebral bodies increases the risk of graft subsidence or dislodgement if an isolated ventral procedure is performed. In addition, the substantial surgery required to accomplish combined ventral-dorsal cervical reconstruction may not be well tolerated by elderly patients.

Patients with central stenosis and neutral or lordotic alignment may be treated via an isolated dorsal procedure, such as laminoplasty.⁴² If ventral decompression is required, standard discectomy/corpectomy procedures with ventral plating may be performed for short segments (Fig. 131-4). Inclusion of dorsal instrumentation should be considered for patients requiring decompression over more than three disc spaces, and for those with significant kyphosis. These treatment approaches generally provide satisfactory clinical outcomes while reducing significant complications.

FIGURE 131-4 Myelograms (A and B) and MRI (C) of a 65-year-old man who developed recurrent symptoms of radiculopathy after a motor vehicle accident. He had undergone a prior two-level discectomy performed elsewhere with a solid fusion obtained at C4-5, but a nonunion had occurred at C5-6. A CT myelogram shows degenerative change and foraminal stenosis at C6-7 (B) and an MRI shows the same at the nonunion site at C5-6 (C). Note kyphosis across the C3-4 disc demonstrated on sagittal plane MRI. D and E, Anteroposterior and lateral views demonstrate solid consolidation after a corpectomy of the C6 vertebra, including resection of the C5-6 nonunion and a discectomy at the C3-4 level with structural iliac crest graft and spanning anterior cervical locking plate. Alternating levels of corpectomy and discectomy, as in this case, allow better anterior column support and segmental fixation with ventral instrumentation.

Spinal Trauma and Spinal Cord Injury

Numerous characteristics of spinal injury are unique in the elderly patient, including injury mechanisms, fracture types, incidence of neurologic deficits, and outcomes. The primary mechanism of injury in young patients is motor vehicle collisions, whereas the leading cause of spine fracture in patients older than 65 years of age is falls.^43,44 Significant neurologic deficits are also significantly more common in younger patients than in the elderly, possibly reflecting this difference in injury mechanisms.^43,45

Outcomes from traumatic spinal injuries also differ significantly between elderly and nonelderly adult patients. Elderly patients have a significantly lower survival rate than nonelderly adults, both with and without neurologic injury. Neurologic injury is especially devastating in the elderly because the 60-day mortality rate for patients older than 65 years of age with traumatic paralysis approaches 30%.⁴³

Understanding these issues may factor significantly in clinical decision making. Families of elderly patients with significant neurologic injuries should understand the high risk of poor outcomes in this age group. Given the significant risk of early mortality, as well as the likely disability resulting from profound neurologic deficits, patients and families may in some cases prefer withdrawal of support over aggressive interventional treatment.

Finally, injuries appropriately treated with surgical intervention in younger patients may be treatable with minimal intervention in the elderly population. For example, risks associated with nonunion after dens fracture appear to be limited in elderly patients, and it is not clear that surgical stabilization of established nonunions is warranted.^28,46 Treatment decisions for these injuries are best decided on a case-by-case basis and depend on patient preferences, health, and mental status, and the nature of the injury (Fig. 131-5).

FIGURE 131-5 A, Myelogram of a 97-year-old woman discovered incidentally on admission to trauma service after a motor vehicle accident to have a mobile nonunion of a prior dens fracture. She was asymptomatic from this, both with respect to neck pain and neurologic symptoms. Workup included a CT scan with reconstructions at the time of injury. B, Space available for the spinal cord is 21 mm on the extension view. She was treated with observation, with no clinical incident at 6-month follow-up.