Evidence Based Medicine: Preoperative Prediction of Failure to Use a Prosthesis
A recent issue of the Journal of Vascular Surgery published a large retrospective review of lower limb amputations performed in the Clemson University/Greenville [South Carolina] Hospital System; Steve Hamontree CPO was among the co-authors. [Taylor, Kalbaugh, Blackhurst, Hamontree et al, Preoperative clinical factors predicting functional outcomes after major lower limb amputation: An analysis of 553 consecutive patients. J Vasc Surg 42:2; 227-234, August 2005] The impetus for this review was the growing recognition by vascular surgeons that treatment of diseases associated with aging, such as peripheral vascular disease, has the potential to bankrupt the healthcare system due to the influx of elderly baby boomers beginning in the next decade. It is highly likely that future reimbursement will be linked to evidence-based treatment protocols.
As the authors correctly note, prior work has shown that maintaining the ability to ambulate has previously been shown to correlate with preserving independence. So, the ultimate question to be answered will be the cost of medical and prosthetic treatment versus the costs associated with a loss of independence. Identifying any strong correlations between objective preoperative measures and long term use of an artificial limb can help clinicians make more effective surgical and rehabilitation decisions.
This is a well crafted and clearly written study from a group with extensive experience in evidence-based clinical research, and the conclusions drawn have a number of implications for prosthetic practice. The principal limitation is its retrospective nature but, since we have such sparse objective evidence on predicting the outcome after amputation, this is an important contribution to our understanding.
The patient population seems typical of the individuals seen in prosthetic clinics in the United States. Of the 533 patients studied, the majority [303] had at least one revascularization attempt prior to amputation. Prosthetic use was defined as donning the artificial limb at least one hour daily. Several of the factors investigated had no significant impact on ambulation with a prosthesis, including race and the presence of diabetes or peripheral arterial disease. And, as would be expected, the relatively high mortality rate for this population was confirmed.
Factors that were related to failure to use a prosthesis in this cohort of patients were:
- Advancing age
- Higher level of amputation
- Loss of both lower limbs
- History of smoking
- End Stage Renal Disease [ESRD]
- Presence of Coronary Artery Disease [CAD]
- Dementia
- Nutritional deficiency
- Prior vascular surgery
- Preoperative functional status [ambulatory or not?]
- Preoperative living status [independent or not?]
They also looked at the each individual's ambulatory status at one year post-amputation. In addition to the three factors noted previously, neither diagnosis, history of smoking, prior vascular surgery or postoperative living status influenced whether patients continued to walk long term.
Interestingly, the factors that affected continuing to ambulate were somewhat different:
- Advancing age
- Higher level of amputation
- Loss of both lower limbs
- Gender
- End Stage Renal Disease [ESRD]
- Presence of Coronary Artery Disease [CAD]
- Dementia
- Preoperative functional status [ambulatory or not?]
The discussion section of this paper is very thought provoking and notes that substantial additional research is required before we can begin to make evidence-based decisions about these sorts of medical treatments with confidence. However, the authors do make some observations that support general clinical consensus. Perhaps most significantly from my perspective, they comment that these data clearly show that major lower limb amputation does not always mean there is a poor prognosis. For example, in this cohort, patients less than 60 years old who were ambulatory prior to amputation and had well controlled comorbidities had a collective ambulation rate of 70%, a one year survival of 80%, and an independent living status of 90%: very good odds indeed.
These authors suggest that palliative above knee amputation should be performed in the population that is highly unlikely to ambulate significantly with an artificial limb, presumably without the added cost and morbidity associated with attempting vascular salvage procedures. They define this group as individuals greater than 70 years old who are already non-ambulatory or demented or who have CAD or ESRD. [Some orthopaedic surgeons would argue that knee disarticulation is preferable for palliative amputation, but this was not discussed in this publication even though >4% of the patients studied had through-knee ablations.]
Conversely, the authors argue that these data support the notion that younger patients who are functional ambulators but have severe PVD would be best served by immediate amputation below the knee joint and aggressive early rehabilitation rather than a high risk bypass that, should it fail, will necessitate loss of the knee joint. They suggest that the large number of patients between these two groups should be studied much more intensively since intense risk factor modification or advances in prosthesis technology may improve their overall functional performance. They close the article by reiterating that transtibial amputation, in particular, should be viewed not as treatment failure but instead as a treatment option to extend the patients function and independence.
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