In 2000, 35 million Americans, or 12.4% of the US population, were age ≥65 years, with 1.5% more than the age of 85 years, the older group demonstrating the most rapid growth in the previous 10 years. Those numbers are projected to continue to increase to 13% and 2% by 2010, and to 16.3% and 2.2% by 2020, respectively.1,2 Although this trend may be worldwide, the United States ranked third among all countries with 8% of the world's elderly population. As the size of the elderly population increases, so too does the number of elderly patients presenting with disabling degenerative lumbar conditions requiring surgery.3,4 According to a 2005 study of US trends in lumbar fusion surgery, the number of lumbar fusions increased most rapidly among patients in their 60s and older, increasing 230% between 1988 and 2001, compared with 180% among those in their 40s and 50s, and 120% among those in their 20s and 30s.5
Back and/or leg pain resulting from degenerative spinal conditions and neural compromise may cause loss of function that severely limits quality of life in elderly patients. However, the risk to benefit ratio of surgical versus nonsurgical management in a population of patients with age-related comorbid conditions is debated. The medical literature is conflicted on this topic, with some reports concluding an increased risk of complications with advancing age,4,6,7 and some concluding no such association.8–11
These reports varied with respect to surgical approach studied, most reporting the results of decompressive surgery alone,3,11–15 some with adjunctive fusion.8–10,16–18 Segmental stabilization and fusion is sometimes a necessary adjunct to decompression in cases of pre-existing or iatrogenic instability associated with degenerative conditions such as spinal stenosis, spondylolisthesis, and scoliosis. In 2001, fusion procedures represented >50% of all in-patient lumbar spine operations excluding those for disc herniations.5
The procedure most prone to complication tends to be lumbar interbody fusion because of its comparative complexity and operative duration. The traditional open posterior lumbar interbody fusion (PLIF) procedure provides wide visualization and circumferential decompression of the neural elements. Although instrumented PLIF has been shown to provide satisfactory clinical results in the general adult degenerative population, it is also associated with complications at a higher rate than decompressive surgery alone.4,18 Okuda et al found a 25% complication rate in 251 patients ranging in age from 15 to 87 years (average, 61 years). The most common intraoperative complication was dural tear (7.6%), and the most serious complications of PLIF included severe postoperative neurologic deficits.19
With the assumed increase in risk of complications in the elderly population, it is imperative that we better define indications, risk factors, and appropriate surgical interventions to effect a safe and efficacious treatment in this population. Surgical time and blood loss have been implicated in higher rates of complications, even in reports where age was not.16,17 Experience with minimally invasive techniques has taught us that equivalent clinical outcomes can be achieved with much less perioperative morbidity by using smaller portals and minimizing surrounding soft tissue damage.20,21
Lateral lumbar interbody fusion is one such procedure, allowing for anterior vertebral column access using only 2 small incisions laterally. Because the approach is lateral, it avoids many of the significant risks of either an anterior approach—including vascular and visceral injury, and those of a posterior approach—including paraspinal muscle denervation, dural tear, and neurologic injury from dural retraction. The procedure has been described previously,22–25 and encouraging outcomes have been reported.21,25,26 No prior reports, however, have highlighted its application in an elderly population.
The current study was undertaken to evaluate the outcomes of minimally invasive lateral approach spinal fusion in octogenarians, and to compare those results with outcomes of octogenarians treated by traditional open posterior approach spinal fusion, with a hypothesis that interbody fusion procedures in the elderly patients are safer if performed minimally invasively as compared with traditional open techniques.
Materials and Methods
In our minimally invasive surgery (MIS) cohort of patients, we used an extreme lateral interbody fusion approach (XLIF, NuVasive, San Diego, CA), described in more detail in previous reports.22–26 The traditional PLIF procedure has also been well described.27
Grafting material for all patients included a composite of demineralized bone matrix, cancellous allograft, local bone source, and bone marrow aspirate. Supplemental internal fixation was carried out in all patients through the use of unilateral or bilateral pedicle screws, placed through an open exposure in PLIF patients and percutaneously in MIS patients, with the exception of one MIS patient who was treated without supplemental internal fixation (stand alone).
Data from a consecutive series of all patients treated with MIS lumbar fusion at a single institution were prospectively captured to evaluate longitudinal clinical and radiographic outcomes relative to various demographic and diagnostic criteria. From this database and with Institutional Review Board approval, a total of 40 MIS patients were identified as aged ≥80 at the time of surgery with a minimum of 3 months follow-up. A retrospective chart review of PLIF patients from the same institution treated before the adoption of MIS techniques identified 20 PLIF patients of at least 80 years. In both groups, all patients with at least 3 months follow-up who met the age criteria were included.
Clinical and radiographic data were reviewed to assess demographics, comorbidities, surgical details, hospital stay, complications, reoperation rate, and postoperative mortality rate in the 2 groups. Discharge location, typically either home or to a skilled nursing facility, was determined by the collective opinion of the treatment team including nursing representatives, physical therapy, and the operating surgeon. Additionally, longitudinal results of patient-reported pain scores and radiographic (radiograph and CT) measures, independently assessed, were included to address the minimally invasive procedure's effectiveness in addition to its safety.
Multivariate logistic regression analysis was performed to test whether age, gender, body mass index, primary diagnosis, presence of preoperative comorbidities, and operative procedure were independently associated with morbidity and mortality. T tests and χ2 tests were used where appropriate to assess preoperative (demographic and diagnostic) and postoperative (outcomes) differences between study groups (PLIF and MIS). All analyses were performed with significance defined as P < 0.05.
The demographics of the 2 groups are outlined in Table 1. Average age was statistically different between the 2 groups, the MIS patients averaging 82.6 years and PLIF patients 84.2 years (P = 0.0245)—although this difference was not practically significant at only 18 months (less than 2% of total life-years). Primary diagnoses for the use of interbody fusion were similar in the 2 groups, the majority presenting with stenosis (all coupled with a secondary diagnosis of instability) (70% MIS, 65% open PLIF), spondylolisthesis (12.5% MIS, 15% open PLIF), and scoliosis (12.5% MIS, 10% open PLIF). The existence of preoperative comorbidities was also similar in the 2 groups, with only the incidence of prior neoplasia being statistically different between groups.
The perioperative and postoperative results of the 2 groups are outlined in Table 2. MIS procedures included 63 treated levels: 25 single-levels, 7 two-levels, and 8 three-levels, all spanning from L1–L5, 62.5% including the L4–L5 level. Open PLIF procedures included 52 treated levels: 4 single-level, 7 two-levels, 7 three-levels, 1 five-level, and 1 seven-level, all spanning from T10 to S1, with 80% including the L4–L5 level (Figure 1). Differences between groups in the number of levels treated are explored further in the Discussion.
Blood loss, as measured by average pre- to postoperative hemoglobin (Hgb) change, was statistically lower in the MIS group than the open PLIF group (1.4 vs. 2.7 g; P < 0.0001). There were no blood transfusions in the MIS patients, whereas 14 (70%) of the open PLIF patients had transfusions (average, 2.14 U), P < 0.0001. Three (15%) deep infections occurred in the open PLIF patients, whereas none (0%) occurred in the MIS patients, and the difference approached significance (P = 0.59).
Hospital stay was significantly less in the MIS group (P < 0.0001): these patients were discharged from the hospital in an average of 1.3 days; whereas open PLIF patients were hospitalized in an average of 5.3 days. All but 3 (92.5%) MIS patients were discharged to their homes, whereas all of the open PLIF patients were discharged to skilled nursing facilities. At 12 months postoperative, all MIS patients had at least returned to their preoperative level of dependence in living.
Complication rate was statistically significantly lower in the MIS group than the open PLIF group (P < 0.0001). Complications in the MIS group included a single implant fracture during insertion (replaced at the time of surgery without incident); a compression fracture of the vertebral body at an adjacent level 4 weeks after surgery (successfully treated with percutaneous vertebroplasty); and a single case of atrial fibrillation (no sequelae). In the open PLIF group, there were 3 deep wound infections (2 requiring reoperation), 1 superficial infection, 1 wound dehiscence, 3 pneumonias, 1 compression fracture (likewise treated with percutaneous vertebroplasty), 1 intestinal obstruction, and 2 cases of postoperative ileus.
The early term postoperative mortality rate was statistically significantly lower in the MIS group than the open PLIF group (P = 0.0018). Following MIS surgery, 1 of the 40 patients (2.5%) passed away 6 months after surgery after a myocardial infarction. Following traditional open PLIF surgery, 6 of the 20 patients (30%) passed away: 3 within 3 months of surgery (2 postinfection, 1 postpneumonia), 1 after 6 months, 1 after 12 months, and 1 after 18 months.
MIS Clinical and Radiographic Outcomes
Patient-reported clinical and independent-physician measured radiographic results were also captured as part of the institution's larger database (Table 3, Figure 2). These same measures were not captured prospectively for the open PLIF cohort and so are not included here. In the MIS group, pain scores (measured on a visual analog scale, or VAS, from 0 to 10) were significantly reduced from an average of 8.6 before surgery to 2.0 at 3 months, 0.9 at 6 months, and 1.4 at 12 months (P < 0.0001). Disc height significantly improved from 5.5 mm before surgery, to 9.5 at 3 months, 9.2 at 6 months, and 9.1 at 12 months (P = 0.0008). In those patients with spondylolisthesis, the transition significantly improved from an average of 5.5 mm before surgery, to 1.2 mm at 3 months, 0.9 mm at 6 months, and 1.5 mm at 12 months (P = 0.0009). As a whole, progression to fusion has been steady, with average modified Lenke fusion scores (1 = consolidated, 2 = partially consolidated, 3 = not yet consolidated)28 of 2.0 at 3 months, 1.4 at 6 months, and 1.1 at 12 months.
As the size of the elderly population becomes larger both quantitatively and proportionally, increasingly more of these older members of society are also requiring spine surgery to overcome the pain and disability of degenerative lumbar conditions.3,4 Indeed, it has been shown that an increasing number of elderly patients are undergoing instrumented lumbar fusions for the treatment of degenerative disorders.18 However, higher complication rates in the elderly than in the general population have been reported in both decompressive3,4,6,7,12,13,15 and fusion procedures.29,8,16–18 Benz et al found a 41% complication rate in patients with decompression or fusion who were >70 years of age.3 Smith and Hanigan reported a 33% rate of complications in patients of the same age who had undergone decompression alone.7 Deyo et al reported an 18% complication rate in patients >75 years.4 Johnsson et al went as far as to recommend nonsurgical treatment for the elderly population.6 With respect to fusion surgery, Raffo and Lauerman reported a 20% rate of major complications in patients more than 80 years, correlated with comorbidities. However, the authors concluded that, in well indicated patients, advanced age or the presence of medical comorbidities should not necessarily preclude surgical treatment with decompression and instrumented or noninstrumented arthrodesis.29
More recently, Carreon et al found a 79.6% complication rate in patients greater than 65 years of age who underwent posterior decompression and fusion16: 21.4% had major complications, and 50% had 2 or more complications. The complication rate increased with age, blood loss, operative time, and the number of levels fused. The authors concluded that “elderly patients are less able to tolerate major surgery because of their general medical condition and associated medical problems. Attention should be paid to the control of blood loss and limitation of operative time.”16 Cho et al similarly found that excessive intraoperative blood loss was the most significant risk factor for the development of early perioperative complications.17 The authors of the current study agree, and attribute the low complication rate and high clinical success rate in this study of octogenarians to the less invasive nature of the MIS procedure compared with that of the PLIF, with its smaller incisions, significantly lower blood loss, rate of transfusion, and hospital stay.
Several other authors have reported favorable results after lumbar decompression and/or fusion surgery in the elderly patient.8,10,11,14 Ragab et al, in particular, found that morbidity was not associated with advanced age in surgery for spinal stenosis (with and without fusion), nor were patient satisfaction or return to activities. Kilincer et al similarly concluded that withholding lumbar spine fusion solely on the basis of advanced age is not warranted, based on their finding that complications and perioperative events following posterior lumbar decompression and fusion in the elderly (>65 years) were comparable to those observed in younger patients.9
Not only is advanced age not definitively predictive of complications, but the effect of preexisting comorbidities on complication rates in the elderly population is also debated, with some researchers finding a direct correlation,4,7,13,30 and others finding none.3,10,16 The current study did not find a correlation between preexisting comorbidities and morbidity or mortality.
Similar to our own findings, Cassinelli et al found that advanced age, the presence of medical comorbidities, or the use of instrumentation did not increase the rate of major or minor complications in patients undergoing posterior decompression and fusion (with and without instrumentation). However, patient age was related to the need for subsequent transfer to a rehabilitation facility.8 This factor may be the most critical to this patient population. In our own hands, all of our PLIF patients required transfer to skilled nursing facilities indefinitely, whereas 92.5% of our MIS patients were able to recover quickly and return to their homes immediately after surgery. In our experience, independence and quality of life are these patients' highest priorities, and are clearly better served using MIS treatments.
With respect to postsurgical mortality rates, it is difficult to separate the consequences of surgery from those of aging. Higher rates of mortality have been noted among older patients undergoing discectomy.15 Oldridge et al reported increased mortality only in patients aged >80 years.30 Deyo et al reported a mortality rate of 0.6% in the elderly population, which was approximately 3 times greater than the rates commonly cited for lumbar discectomy in a wider population.4 Silvers et al reported a short-term (1–2 months postoperative) mortality rate of 0.8%.14 Our own open PLIF experience showed a not insignificant short-term mortality, consistent with the assumed increased risk of more invasive surgical procedures. In our practice, traditional open spinal fusion was abandoned in the extreme elderly for this reason. However, although still an interbody fusion procedure, our minimally invasive experience has been quite positive, with few complications leading to early postoperative mortality, and encouraging overall clinical outcomes. In the current study, the incidence of postoperative mortality was significantly related to incidence of infection (P < 0.0001), incidence of complications (P = 0.0025), and increase in blood loss (P = 0.0447), all of which were greater in the open PLIF group compared with the MIS cohort.
This study sought to evaluate the differences in morbidity and mortality in the early postoperative period between octogenarians undergoing either a traditional open or minimally invasive procedure. Decreased postoperative morbidity has been a claim of minimally invasive techniques and is demonstrated here, with statistically significantly lower blood loss, need for transfusions, perioperative complications, and duration of hospital stay in the MIS group compared with the traditional open PLIF group. Although this was not a randomized comparison, the cohorts were demonstrably similar. There was, however, a difference in the number of levels treated. Although it is true that the PLIF group included more levels of surgery, on average, per patient, we have found that we are able to effect the same clinical result by treating fewer levels using MIS lateral techniques. In our experience, the correction and stability achieved by placing a large intervertebral implant (much larger than can be placed from a posterior approach) is inserted across the disc space is impressive. Disc height is improved and maintained, spondylolisthesis is reduced and maintained, and the large surface area and stability lead to the ultimate goal of fusion. Moreover, patient-reported pain scales showed initial improvement that was maintained over time. This validates the notion that appropriate surgical plans were undertaken based on symptoms. (i.e., we did not treat fewer levels just for the sake of being less invasive). In the end, we believe that fewer levels need be incorporated into the fusion constructs because the greater stability afforded by the larger ventral implants decreased the need for immobilizing additional dorsal levels to achieve the same stability. We have averaged one fewer levels of treatment in MIS versus open PLIF because the technology provides improved stability with less collateral damage.
The incidence of complications in lumbar fusion surgery varies widely across the published data because of differences in definition and specificity, but it is clear that there is an assumption of increased risk with age. Compromise due to expected blood loss, wound infections, and anesthesia-related complications is what precludes many elderly patients who are suffering from receiving effective surgical treatments. It is our belief that the relatively low incidence of complications across the MIS group is derivative of the diminished trauma caused by these approaches.
Our traditional impressions of accessibility of care must be reevaluated based on improvements in technologies. Recently, large prospective, randomized multicenter studies31–35 have shown that surgery is more successful than nonoperative care in the treatment of certain spinal disorders (e.g., disc herniation, stenosis, and spondylolisthesis). We must begin to reassess our prejudices about offering care to certain subsets of the population. Our assumptions about the complications of intervention in the elderly may be derivative not only of the age of the patient population but also on the limitations of traditional procedures. Surgical intervention using modern techniques is now safe even at the extremes of life, as demonstrated by these MIS results. The risks may no longer outweigh the benefits; more importantly, it is incumbent on surgeons to offer proven techniques for reducing suffering to the elderly patients and then allow the patients to decide for themselves whether intervention is reasonable.
As the elderly population of the western world inexorably increases, physicians find themselves treating a group of people desirous of maximizing their life quality. Traditional assumptions about the expectations of the elderly must be revised in light of the opportunities to improve life afforded by newer technologies. We believe it is imperative that surgeons and patients alike understand the risks associated with spine surgery in the elderly and that effective surgical treatment options are available to them without unreasonable risk of complication. We should not deny treatment to those in need due to age, but we should instead be selective of the treatments offered.
- Results after modern less disruptive surgical approach technique appear to contradict traditionally held assumptions regarding the risks of surgery in the elderly, with demonstrated shorter surgical times (and therefore less anesthesia), minimal blood loss, fewer complications, and quicker recovery.
- Surgical treatment, which can provide elderly patients with improved quality of life through relief of pain and dysfunction, need not be withheld because of age. However, consideration should be given to the morbidity of the choice of surgical approach.
- Compared with traditional open procedures, the use of an MIS approach allows a quicker recovery, with fewer complications, resulting in the discharge of patients to home rather than to skilled nursing facilities, an important consideration for this patient population.
The authors thank Christopher Case, MD, (IRB Chairman, St. Mary's Health Center IRB, Jefferson City, MO) for his assistance with manuscript review, and Jamie Patterson (Research Coordinator, Spine Midwest, Jefferson City, MO) for her help with manuscript preparation.
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