In the current era of new diagnostic and therapeutic advances for CLI, the goal of limb preservation has become even more paramount. However, it remains that a given subset of patients suffer a prolonged recovery, significant economic burden, and limited functionality despite multiple revascularization attempts, even if they do, in fact, salvage their limb. The question thus arises whether we can identify patients at the time of revascularization that may achieve better functional outcomes in the setting of subsequent clinical failure of their procedure. This study presents initial answers to that question by describing 1-year functional outcomes of patients who lost their limb after infrainguinal bypass and by comparing that outcome among amputation levels. Secondly, we analyzed variables at the time of revascularization and their impact on functional outcome in the setting of subsequent amputation, which enables physicians to risk-stratify vascular patients before they are faced with limb loss.
In this multicenter regional analysis of vascular amputees, we demonstrated that subjects who undergo an amputation after LEB have worse functional outcomes than patients who do not undergo an amputation after LEB. Patients with a major amputation were nearly 50% less likely to have a good functional outcome at 1 year when compared with patients who did not have an amputation after LEB. Furthermore, we showed that the functional status achieved by amputees is directly related to the level of amputation. We were also surprised to discover that even a minor amputation can significantly decrease functionality, as shown by the 7% lower rate of patients who were ambulatory at home after a toe or forefoot amputation compared with those who underwent LEB alone.
Many believe that, whenever possible, a more distal amputation is preferred for improved function. Physiologic studies have demonstrated that a below-knee amputation versus an above-knee amputation is associated with lower energy expended with prosthetic use and therefore results in better ambulation rates.15
A single-center series of vascular amputees reported by Nehler et al.10
had similar findings. In reviewing 5 years of records of vascular patients who underwent a major amputation at either a university or Veterans Affairs hospital in Colorado, they found that 61% of below-knee amputees were ambulatory either indoors or outdoors 10.3 months after surgery. That number was much lower for above-knee amputees, at only 24%. They did not investigate the effect of a minor amputation on subsequent functionality. Taylor et al.16
reported a larger series of vascular amputees with longer follow-up from a single institution in South Carolina. Of their patients who underwent a below-knee, through-knee, or above-knee amputation, 55% maintained ambulation with or without prosthesis, and 73% maintained independent living status at 1-year follow-up. We found our regionally obtained ambulation and living rates in amputees after LEB to be remarkably similar, with 53% of major amputees ambulating with or without assistance and 71% living independently at 1 year.
In our cohort, functional status at the time of LEB had the highest predictive impact on functionality after a subsequent amputation. In subjects that ultimately underwent amputation, those that were ambulatory before LEB were three times more likely to ambulate on hospital discharge after LEB, and those who lived at home before LEB were seven times more likely to live independently in the first year after LEB. The impact of functionality before surgery on long-term ambulation rates has been equally described through the VSGNE registry for patients who undergo lower extremity revascularization 17
and should thus be greatly considered when evaluating any patient for LEB.
Our multivariable model demonstrated that patients with a right-sided LEB had a lower likelihood of achieving an overall good functional outcome following amputation. The statistical significance of this variable may be in part due to the relatively small sample size of our cohort as reflected in the wide range of the 95% CIs (0.54–0.96), which additionally approaches one. However, this finding may reflect a physiologic occurrence. Since 90%of individuals with normal gait have right leg dominance,18,19
it is possible that our result may show the larger inherent functional loss when operating on or amputating part of the dominant lower limb as opposed to the nondominant leg. Further work at a larger sample size would obviously be necessary to confirm this finding.
Furthermore, we outlined that negative predictors of a good functional outcome, such as coronary disease, congestive heart failure, older age, or dialysis dependence can inform patients and physicians at the time of LEB on a patient’s decreased likelihood of being ambulatory and living independent if faced with an amputation. Nehler and Taylor found similar relationships. Nehler et al. showed that older age was associated with lower rates of ambulation after amputation.10
Taylor et al. described that preoperative ambulation status, older age, level of amputation, and medical comorbidities such as end-stage renal disease were similarly associated with the functional outcome of amputees.16
Our analysis expands on these findings to show that the presence of each of these patient variables has a linear additive effect on long-term outcome, such that if all are present at the time of LEB, a patient has a virtually zero chance of ambulating and living independently after a subsequent amputation.
Lastly, we were surprised to find that long-term survival is not influenced by the level of major amputation. However, it is important to note that our patient cohort is a selected population of vascular amputees that were deemed healthy enough to undergo LEB. Survival following primary amputation is not directly informed by our study and remains a topic of debate. While a study by Cruz et al.11
demonstrated that actuarial survival after major amputation is not affected by amputation level in a vascular patient cohort from an Arkansas Veterans Affairs hospital, a larger series of vascular amputees reported by Aulivola et al.9
from a university hospital in Boston, MA, shows the opposite. They found that 74.5% of below-knee amputees were alive after 1 year compared with only 50.6% of above-knee amputees. This may represent a difference in underlying medical comorbidities, as their analysis included all amputations performed for vascular disease.
In certain high-risk patients, it is often difficult to determine whether a primary amputation or several extensive attempts at revascularization will provide a better functional outcome. We believe vascular surgeons can use the information presented herein as a preoperative counseling and decision-making tool in this setting. Elderly patients with congestive heart failure, for example, may learn of their lower chance at a good functional outcome after amputation and therefore prepare accordingly preoperatively. On the contrary, younger, healthier, and functionally independent patients that lack acceptable bypass conduit, a good distal target, or other important technical features may be better candidates for primary amputation, given their slightly higher likelihood of a good functional outcome thereafter.
Our study has several limitations. First, as mentioned previously, our cohort is limited to patients who have received an amputation only after previously having undergone an infrainguinal bypass. By nature of our dataset, primary amputations are not captured, and we are thus unable to directly compare how patients with a primary amputation fare differently than those with an amputation following LEB. We have therefore put into place the collection of primary amputations in the database and plan on such a comparison in a future analysis. Second, our database tracks patients for only 1 year and therefore does not allow us to comment on more long-term results. Third, the nature of our regional demographics limits our results to patients of primarily white race. Understanding that amputation rates are higher among other racial subsets,4
our future work will focus on a more diversified representation of racial and ethnic backgrounds. Fourth, we used two measures (ambulation and living status) to determine functionality. Although these may approach the overall functionality of the vascular patient after an intervention, they are limited in their scope and generalizability. The description of functional status (after both LEB procedures and amputations) and quality of life in vascular patients has undergone a recent evolution.20,21
Traditional outcome measures for LEB (mortality, graft patency, and limb salvage22–24
) have recently been complemented by functional measures such as ambulation and living status.10,14
The VSGNE database was specifically designed to prospectively capture such functional outcomes, and thus, our main outcome metric of a “good functional outcome” combines these measures into one objective variable.
Lastly, while quality-of-life instruments, such as the short-form 36 or the VascuQol assessments, have been used on occasion in large randomized trials to examine patient functional outcomes,25,26
these instruments were not used in this study, as the cost associated with the administration of these surveys was prohibitive within our regional registry. Current assessment tools, such as the VascuQol or Nottingham Health Profile, focus on patients with claudication and may not be generalizable to patients with severe CLI. Disease-specific, validated quality-of-life instruments represent the next step in answering the question of when a primary amputation may provide an improved functional or quality outcome from the patient’s view instead of further attempt at revascularization. A better understanding of this decision will require a patient-centered measurement tool designed to evaluate patient-level quality of life, specifically in CLI patients who undergo surgery or amputation. Our future work will aim to develop these instruments.