Between 2012 and 2050, the United States will experience considerable growth in its older population. By 2050, the population aged ≥65 years is projected to be 83.7 million, nearly double the 43.1 million estimated for 2012.1 In 2012, the total US expenditure for Medicare was $572 billion; growth by 2023 is estimated to be >$1.1 trillion.2 As part of that overall surge in cost, orthopaedic surgeons will be faced with unique challenges in caring for this aging patient population; this is particularly true for spine surgeons who are treating growing numbers of patients with traumatic or insufficiency spine fractures at the same time that we deal with degenerative deformities and instabilities. Although many of these challenges presently lack robust evidence to guide optimal treatment, common issues facing spine surgeons who care for the aged will need to be addressed. These include perioperative bone health, spinal fixation strategies in the osteoporotic spine, odontoid fractures in the elderly, the role of cement augmentation in elderly osteoporotic compression fractures, and planning principles in the elderly patient with spine deformity.
To a large extent, the perioperative medical treatment of the aging spine patient is a matter of optimizing medical comorbidities: cardiac, pulmonary, renal, and endocrine. Most of these developments will be managed by the patient’s primary team and consultants, but the spine surgeon would do well to provide special attention to the patient’s bone health, given the prevalence of bone disease in the aging population.
Evaluation of Bone Health
Women aged >65 years and men aged >70 years benefit from a dual-energy x-ray absorptiometry (DEXA) scan before major surgery, such as a spine fusion or joint arthroplasty. The age that triggers the need for a scan is reduced by 5 years for each comorbidity (eg, family history, smoker, early hysterectomy, history of fragility fracture). The orthopaedic surgeon treating a fragility spine fracture or contemplating spine fusion should order the DEXA scan. Studies have shown that, when the orthopaedic surgeon initiates diagnosis and risk stratification, the likelihood that the patient will receive proper treatment increases dramatically.3
Routine preoperative evaluation for serum calcium level, 25-hydroxyvitamin D, intact parathyroid hormone level, and, for males, testosterone level, should be done. Target serum 25-hydroxyvitamin D levels should be >30 ng/ml.4 Normal testosterone levels vary for men, decreasing with age in adults. It is unlikely that the orthopaedic surgeon is best qualified to make treatment decisions on testosterone supplementation, but based on results of these evaluations, the patient may be referred for treatment by a metabolic bone expert.
Vitamin D is essential to bone health. Increasingly, it is being considered a hormone rather than a vitamin because its receptor has been found on the surfaces of many different cell types. For spine patients, the impact of vitamin D on the immune system may be just as important as it is for their bones.5 Kroner et al6 state that “the facts that (i) immune cell functions are critically regulated by bioactive 1,25D; and (ii) immune cells metabolically participate in the generation of 1,25D from serum 25D, clearly document importance of vitamin D in shaping immune responses.”
Routinely recommending vitamin D supplementation for all spine fusion patients (especially those aged >65 years) may be the most efficient way to ensure that a patient will have a sufficient level at the time of surgery.7 Vitamin D supplementation will increase the likelihood of bone healing and may reduce surgical site infection risk.8 Supplementation with 800 IU/d of cholecalciferol (D3) achieved vitamin D sufficiency in a cohort of nursing home residents.9 As a fat-soluble vitamin in an increasingly obese elderly population, 1,000 to 2,000 IU/d of vitamin D3 (available over the counter) is recommended routinely to address deficiency.10 An alternative treatment algorithm for severe deficiencies (<20 ng/ml) has been to prescribe 50,000 IU/week of ergocalciferol (D2) for 12 weeks, then recheck a vitamin D serum level. Even with moderate sun exposure, 10,000 IU/d of D3 can be used without the risk of toxicity.11,12
Ensuring adequate calcium stores is also important to help prevent orthopaedic surgical complications. The typical choices for oral supplementation are calcium citrate and calcium carbonate. Calcium carbonate typically contains a higher percentage of elemental calcium and tends to be less expensive, but it is associated with more frequent gastrointestinal side effects and is not absorbed without an acidic environment in the stomach. Patients taking proton pump inhibitors, those requiring iron or zinc supplementation, those with inflammatory bowel disease, and others who cannot take a calcium supplement with meals should be prescribed calcium citrate.10 Approximately 1,000 mg/d of calcium in divided doses is required for most adults. The US Preventive Services Task Force reviewed the available literature and stated that, although low-dose vitamin D and calcium supplementation has not been shown to reduce fracture risk, they have been shown to decrease risk of fall in the population aged ≥65 years. Authors reporting for the task force also found insufficient evidence to recommend routine supplementation of ≥800 IU of vitamin D and ≥1200 mg of elemental calcium in the elderly.13 Clearly this is an area requiring further study. Recommendations from the Institute of Medicine are described in Table 1.13
Diphosphonates are reported to have a deleterious effect on fracture healing in some animal models.14 This same negative effect has not been shown definitively to occur in humans.15,16 Given these differences, it is difficult to make a strong recommendation regarding the timing of resuming diphosphonate treatment in patients with known osteoporosis and spine fusion or fracture. Denosumab, a receptor activator of nuclear factor-κ B ligand inhibitor, is reported to have a neutral impact on bone healing although it does promote increased bone density and reduction in future fractures.17
Teriparatide (ie, recombinant parathyroid hormone) is the only anabolic bone agent currently available; it requires daily subcutaneous injection. Teriparatide can be used for severe osteoporosis or glucocorticoid-induced osteoporosis. It also is the drug of choice for fragility fractures that occur in patients already being treated with diphosphonates. In a randomized, blinded trial, teriparatide use was associated with quicker return of function and fracture healing in pubic ramus fractures.18 A pair of prospective studies evaluated teriparatide, diphosphonates, and control groups for pedicle fixation in a population with degenerative spondylolisthesis; the risk of pedicle screw loosening was dramatically lower in the parathyroid hormone group, and the fusion rate was higher.19,20
Osteoporosis Treatment After Fragility Fracture
No published data exist on spine surgeon compliance with treatment guidelines, but a recent study reported that only 19% of patients with surgically managed hip fractures received treatment within 1 year of fracture.21 Over the past 15 years, there have been reports on a decline in the rates of osteoporosis treatment following fragility fracture by as much as half.22-24 There certainly may be an opportunity for improvement in this area.
Fixation in the Osteoporotic Spine
The increasing numbers of aged patients with osteopenia and osteoporosis who generally have a greater demand for an active lifestyle can be vexing for the spine surgeon contemplating treatment of spinal instability or deformity in this population. Fixation is prone to failure at the bone-implant interface.25,26 This has led some authors to recommend no surgical options for these older patients. Complications such as proximal junctional failure, pseudarthrosis with rod fracture, screw loosening, and prominent thoracolumbar fixation are well documented in this cohort.27 To address these challenges, some surgeons have recommended using more points of fixation or protecting the construct with postoperative bracing, although the evidence for these strategies is weak. There is evidence that larger diameter pedicle screws improve fixation in osteoporotic vertebrae,28 as can the addition of laminar hooks.29
A growing body of literature indicates that pedicle screw augmentation with cement is an effective strategy to improve vertebral fixation in the face of osteoporosis.30,31 This effect appears to be maintained whether polymethyl methacrylate or various bioactive cements are used.32 The augmentation effect also appears to remain significant whether the cement is placed first and followed by a solid-core screw or whether the cement is injected through a cannulated pedicle screw33 (Figure 1). It is also probable that pretapping pedicle screw pilot holes further enhances the augmentation effect when cement is used.34 Although these screw-augmentation techniques are increasing in popularity, particularly in Europe, there are inherent risks of cement extravasation into the venous system, spinal canal, or disk spaces.35 Because these risks have been reported only sporadically to date, optimal strategies to mitigate them are not well defined.
Geriatric Odontoid Fractures
Odontoid fractures are the most common cervical spine fracture in adults aged >70 years and are increasing in prevalence.36,37 At a point of maximal load during falls from standing height, the presence of weak cortical and scant cancellous bone commonly lead to fractures at the base of the odontoid (ie, type II fractures), which affects treatment decision making. The first decision is to choose between nonsurgical and surgical treatment, followed by the selection of an orthosis or a surgical approach. In addition to fracture morphology, fracture location, angle of fracture, degree of comminution, and amount of displacement, patient factors should be taken into account. These include the degree of osteoporosis, presence of dysphagia preinjury, and severity of cardiac and pulmonary comorbidities. The patient’s social situation and levels of activity and mentation may play a significant role in decision making. For example, a patient who has dementia and is minimally ambulatory may have such limited rehabilitation potential and/or life expectancy that the risk of surgery is unwarranted.
Nonsurgical treatment of the geriatric odontoid fracture is common but not well studied. The halo vest, a traditional nonsurgical treatment of odontoid fractures, works relatively well, but there is a documented nonunion rate in young and older patients treated with the vest. A greater problem with halo vest treatment in the elderly is a significantly increased rate of morbidity and mortality.38,39 Tashjian et al38 reviewed 78 patients (average age, 81 years) and noted that the risk of major complications in patients who wore a halo vest was double that of those who did not wear the vest (66% vs 36%, respectively), and the risk of mortality in patients with halo vests was double that of patients without the vests (42% vs 20%, respectively), both statistically significant. Of greatest concern is aspiration leading to pneumonia. Halo treatment should generally be avoided in the elderly population.
A hard cervical collar does not provide as much stability as a halo vest, but it may cause less morbidity.40 The nonunion rate is high; however, if a stable pseudarthrosis is obtained, it may be adequate in the sedentary elderly patient.41 Still, odontoid fracture in the elderly should be considered a sentinel event with a fairly high mortality rate, no matter the treatment. In a review of 322 patients, Chapman et al42 noted a 30-day mortality rate of 14%, which was markedly higher in the nonsurgically treated population. In a large prospective study of 159 patients, Fehlings et al43 noted an 18% mortality rate, again greater in the nonsurgically treated population. The case series that have reported nonunion rates for halo treatment (range, 10% to 50%) and hard collar (up to 77%) have been too small and heterogeneous from which to draw firm conclusions regarding comparative effectiveness; however, the use of the halo vest may often lead to union at the cost of higher risk of morbidity and mortality.40
Surgical treatment is divided into two categories: anterior surgery by means of odontoid screw fixation and posterior surgery with a C1-C2 posterior fusion and instrumentation. In the presence of good bone stock and minimal or no comminution at the fracture site, odontoid fixation can be a successful treatment option. Increased failure rates in osteoporotic bone have led some authors to use a two-screw fixation technique44 (Figure 2). Bone or tight fibrous union rates are as high as 90%. Dysphagia is a significant concern in elderly patients after anterior odontoid screw fixation, occurring in as many as 35% of patients postoperatively.44
Posterior C1-C2 fusion and instrumentation has become the most common treatment option for geriatric odontoid fractures.40 In retrospective and prospective cohort studies, the complication and mortality rates are lower than those associated with nonsurgical treatment.42,43 Fixation can be accomplished with C1-C2 transarticular facet screws when there is adequate space above the vertebral artery notch or with separate C1 lateral mass and C2 pars or pedicle screws (Figure 3). Each is usually combined with a structural graft between the posterior ring of C1 and the lamina and spinous process of C2. Recent studies suggest improved patient-reported outcomes in the active elderly patient treated in this fashion.45
Nonsurgical Versus Surgical Treatment
Geriatric odontoid fractures are increasingly common and present significant dilemmas in treatment decision making. Fracture morphology and patient factors and comorbidities must be taken into account when deciding how to treat the patient. Nonsurgical treatment is preferred in the sedentary, low-demand elderly patient or when significant comorbidities preclude surgery. A cervical collar results in less morbidity and mortality than does halo vest treatment. Surgical stabilization with two odontoid screws may be considered in the somewhat younger geriatric patient with a type II fracture pattern that will be perpendicular to the screw trajectory, good bone quality, and minimal comminution. These are most commonly treated, however, by posterior C1-C2 fusion with instrumentation, leading to very good functional outcomes in the mid- and high-functioning geriatric patient.
Vertebral Compression Fractures
The primary goals of this procedure are to provide pain relief and improve function by conveying immediate stability to the fracture fragments via cement interdigitation. Early studies were nonrandomized case series, mostly retrospective with a few prospective cohort studies published. Diamond et al46 compared a nonrandomized trial of nonsurgical treatment with vertebroplasty and reported that patients treated with vertebroplasty had more rapid pain relief, more rapid rehabilitation, and a lower complication rate compared with those who underwent nonsurgical treatment. However, the authors reported the benefits to be short term only, and by 6 weeks postoperative, both groups reported similar pain scores.
Hulme et al47 undertook a systematic review of publications related to vertebroplasty and kyphoplasty. They reported that approximately 90% of patients gained some pain relief with either kyphoplasty or vertebroplasty. Most studies showed very little change in vertebral height restoration. Complications included leakage of cement occurring in 9% of those treated with kyphoplasty and 41% of those treated with vertebroplasty, most of these being asymptomatic. A more disconcerting fact was the observation of new fractures at adjacent vertebrae, seen in many of the included studies. Similar findings were presented in studies by Taylor et al,48 Eck et al,49 and Liu et al,50 which showed no substantial difference between the two procedures regarding pain relief, vertebral alignment correction, and functional improvement. Liu et al50 recommended vertebroplasty based on the higher costs of the kyphoplasty. Early studies concluded that pain relief is similar with both procedures, that functional improvement was tied to pain relief, and that cement leakage was more frequent with vertebroplasty but might be clinically irrelevant.
In 2011, the American Academy of Orthopaedic Surgeons (AAOS) published its guidelines on the treatment of insufficiency fractures.51 The recommendations regarding cement augmentation were based on two level I prospective randomized studies (concurrently published) that met inclusion criteria, both of which found vertebroplasty to be no more effective than sham surgery.52,53 Kallmes et al52 did show a trend toward improvement following vertebroplasty, but again, no statistical difference was noted during the time the patients were studied. A third study considered by the guidelines panel correlated kyphoplasty with early improvement in pain and improved function but showed no long-term benefit.54
The AAOS guidelines give a strong recommendation for the use of calcitonin in the first 4 weeks after compression fracture. They recommend against using vertebroplasty and gave a weak recommendation for kyphoplasty because of its correlation with early pain improvement. At the time the guidelines were published, there were no convincing data that the use of cement augmentation in treating insufficiency fractures provided any better long-term benefits than did nonsurgical management.
One of the consistent critiques of the studies by Kallmes et al52 and Buchbinder et al53 was that they did not adequately assess the acuity of the compression fractures in their study cohorts. It seems possible that some of their patients had remote, possibly healed fractures but presented with back pain. Inclusion of such cases might spuriously indicate no treatment effect for vertebroplasty. Since publication of the AAOS guidelines, several high-quality studies have been published that do show promising results for improved pain relief and improvement of quality of life with use of vertebroplasty or kyphoplasty.55-57 Klazen et al55 prospectively randomized acute (<6 weeks old) thoracolumbar compression fractures and showed a marked advantage as measured by visual analog pain scale for vertebroplasty over nonsurgical care that was maintained at 1 year. There is also evidence of a decreased mortality risk in patients with vertebral body fractures treated with cement augmentation. Edidin et al58 reviewed the US Medicare dataset over 4 years, including more than 800,000 patients with compression fractures. They found a 61% adjusted survival rate for those treated with vertebroplasty or kyphoplasty as opposed to a 50% survival rate for those treated nonsurgically. Patients with lymphoma and myeloma appear to be particularly good candidates for this procedure, as Erdem et al59 showed in terms of visual analog pain scale improvement, reduction in narcotic usage, and increased activity levels in their patients at 1 month postoperatively.
There has been compelling evidence since the AAOS guidelines were published that both vertebroplasty and kyphoplasty procedures can result in improvement of pain and quality of life, but additional definitive studies with larger numbers are needed. Patients who benefit from vertebral augmentation appear to be those treated within 3 months of fracture. Most surgical candidates should prove refractory to a nonsurgical trial.
Management of Thoracolumbar Deformity in the Elderly
There are an increasing number of patients aged >65 years with spinal stenosis and associated spinal deformity. This has led to a significant increase in surgical complexity for those patients with stenosis.60 Although nonsurgical management, including therapeutic exercises, anti-inflammatory medications, and activity modifications, remains the initial and frequently the only treatment required, failure of these modalities forces a decision about next steps. This may necessitate choosing between surgical options, each with its own potential risks and complications.
Generally, outcomes of spinal deformity surgery in the elderly are equivalent to those of younger patients and closely correlate with preoperative expectations.61 However, complication rates range from 37% to >50% in some studies.62 One of the key comorbidities affecting outcomes, especially when fixation is required, is osteoporosis. Although bone density changes do not appear to affect fusion rates, screw fixation and initial spinal stability (the key to deformity correction) are altered.
In addition to strategies for improving fixation in the osteoporotic spine, less curve correction—while maintaining sagittal and coronal balance—should be the primary focus, and fusion and rigid implants should not end at a kyphotic segment. Vertebroplasty placed at the upper instrumented vertebrae (UIV) and UIV+1 may provide some resistance to proximal junctional failure.63
Surgical Options for Spinal Stenosis With Deformity
Initial decision making should seek the minimum level of intervention to accomplish the most functional improvement possible with the least risk of complication. Patients with primary symptoms of spinal stenosis who have a mild deformity (eg, scoliosis <20° without lateral listhesis, minimal stable grade 1 spondylolisthesis) may be treated successfully with decompression alone, with lower risk of failure and revision than when fusion is added. In a review of Medicare data for patients with lumbar stenosis, Deyo et al64 showed that interspinous spacer procedures pose a trade-off: fewer complications at the index procedure but higher rates of revision. They also showed that decompression alone was the least costly intervention versus interspinous spacers or fusion procedures for these patients. However, loss of lumbar lordosis, higher L3 obliquity, or significant listhesis portends a worse prognosis, and the addition of fusion should be considered. The extent of fusion and magnitude of the overall surgery must be weighed against comorbidities and associated risks. Anterior- or lateral-only surgery is fairly new, and although some authors have reported success in case report series and prospective series, these approaches are somewhat controversial.65,66 Posterior fusion, or anterior and posterior fusion, remain the most common techniques to manage severe listhesis and sagittal and coronal imbalance. Fusion to the sacrum now is often accompanied by fixation to the ilium.67 Recommendations about how high to go remain elusive.68 Treatment should be customized to each patient’s particular deformity.
A discussion of deformity treatment in the adult should include an understanding of the elements of sagittal balance and how to measure and manage imbalance. Restoration of sagittal imbalance is critical to good outcomes.69 The C7 plumb line or sagittal vertical axis (SVA) is the most common way to measure balance; an SVA >4 cm is the definition of imbalance. This does not indicate that an SVA of >4 cm requires correction; most deformity surgeons aim to bring patients with significant imbalance (>10 cm) closer to but not necessarily all the way to an SVA of 5 cm. This effort is made more complex by adding pelvic tilt and pelvic incidence into the decision.70 Patients with high pelvic incidence are at higher risk of sagittal imbalance, even when the lumbar spine is fixed at “normal” lordosis. Preoperative understanding of the amount of lordosis required (based on pelvic incidence) is key. Pelvic tilt informs the decision by identifying the extent to which the patient is standing (for the radiograph) in a compensated fashion (ie, pelvic tilt >20° to 25°)71 (Figure 4).
With significant sagittal imbalance, high pelvic tilt, and high pelvic incidence, the surgical plan may require the inclusion of an osteotomy. Smith-Petersen or Ponte osteotomies, with removal of posterior elements and compression of the posterior column (potentially leading to distraction of the anterior column), are somewhat easier to accomplish when performed over several levels. These osteotomies can assist in gaining up to 15° or 20°. When a greater change is required, a pedicle subtraction osteotomy can be performed and allows for 25° to 35° of correction70 (Figure 5). These procedures can be combined at different levels for additive correction. Risks are significant, including high levels of blood loss and neurologic injury.
Whether to end an adult deformity construct at L5 or S1 is a topic frequently discussed. If the L5-S1 segment appears normal, with no degenerative changes, no listhesis, and no stenosis, and if it is not involved in the deformity, then it may be reasonable to exclude the segment from the fusion. The advantages are retained lumbosacral motion, which may allow for more normal gait and less risk of sacroiliac joint degeneration, and lower surgical times and complications, including pseudarthrosis, which is a particularly vexing problem at L5-S1. However, there is a substantial risk of progressive disk degeneration at this level, and in patients with sagittal imbalance, also a risk for recurrence of the imbalance.72 Many authors have therefore recommended including the sacrum in a long fusion for deformity in the adult. Techniques for minimizing the pseudarthrosis rate include the addition of an interbody fusion, the addition of bone morphogenetic protein, and/or fixation to the ilium with iliac bolts or S2-alar-iliac screws. This added fixation increases the fusion rate by three times, relieves strain on the S1 screws, and protects against screw pullout.73
Where to stop at the upper end of the construct is also a matter of controversy. Although initial studies suggested that crossing the thoracolumbar junction and stopping the construct at T9 or T10 would lead to fewer proximal problems, more recent reports have suggested that this is not so. Kim et al74 noted a proximal junctional kyphosis rate of 36% to 55% and a revision rate of 25%, whether the construct stopped at L1/L2, T11/T12, or T9/T10. Proximal junctional failure—no matter which specific level is chosen as the upper instrumented vertebra—remains a significant concern. To date, no clear strategy has emerged as optimal to prevent this complication.
Spinal deformity surgery in the elderly is increasingly common, with concern for management of sagittal and coronal imbalance as well as the frequently accompanying spinal stenosis. High complication rates remain a challenge and should be given careful consideration before embarking on surgery. Nonsurgical measures are often successful at controlling symptoms. When proceeding with surgery, osteoporosis and the parameters that affect sagittal imbalance should be identified. Treatment may require an osteotomy, and the levels to include in the fusion should be given careful consideration.
References printed in bold type are those published within the past 5 years.
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