Rethinking Proper Patient Selection For Limb Salvage Interventions

   Reducing the number of lower extremity amputations is a goal for all clinicians caring for patients with diabetes. In spite of this, the numbers of limb-threatening infections and subsequent amputations continue to rise each year. While medical and surgical interventions are frequently successful in facilitating limb salvage in patients facing amputation, failures in limb salvage attempts do occur. These failures result in multiple trips to the operating room, significant potential morbidity and prolonged disability.    In order to more accurately predict which patients are more likely to benefit from limb salvage attempts, we need to modify our patient selection criteria. Enhanced criteria may also help identify which patients would be better served by a single definitive procedure at a level likely to heal with a subsequent, timely initiation of rehabilitation. The following cases illustrate the point.

What Two Case Studies Reveal

   A 58-year-old patient presents with a 20-year history of type 2 diabetes. His control has been mediocre with hemoglobin A1c levels around 8.5 percent. He has been treated for hypertension and is being monitored by cardiologists. The patient has a history of chest pain but no events of myocardial infarction or cerebrovascular accidents (CVA). He developed a pressure ulceration of his fifth toe that led to osteomyelitis. Preoperative indices for healing were borderline.    Surgeons amputated the toe but it failed to heal. Peripheral vascular surgeons performed an angioplasty and the patient’s foot perfusion improved. He did require an amputation of the adjacent fourth toe due to progressive necrosis of the wound edges from the previous amputation. This wound also dehisced but improved slowly over time, probably due to the vascular intervention. In the meantime, his chest pain became worse and he required a coronary angioplasty.    The patient also required prolonged local foot wound care to achieve healing. After two foot procedures, a vascular intervention, cardiac complications, lengthy wound care and a disability that lasted over a year, the foot finally healed and the patient returned to work in his previous occupation. He wears accommodative shoes and sees his podiatrist for regular follow-up visits. This case illustrates a difficult protracted course of limb salvage but nevertheless, the patient successfully returned to productive community activity.    In contrast, a 62-year-old patient had a similar diabetes history but more vascular problems and evidence of the early stages of renal failure. He had a history of myocardial infarction and coronary artery angioplasty before a minor injury to his second toe resulted in distal cyanosis and ischemic pain. The toe was cool, there was no break in the skin and there were no pulses in the foot.    Surgeons performed peripheral vascular stenting and the patient’s ankle brachial artery indices improved. However, the aforementioned toe remained cool and painful. Despite a second toe amputation, the wound still failed to heal. The vascular service performed yet another angioplasty as well as extensive debridement of bone and soft tissue, yet little improvement in the wound occurred. Amputation to the Syme’s level was recommended but the patient was adamant about making more efforts to try to save more of the foot. He proceeded to undergo a transmetatarsal amputation. The amputation site presented a non-viable wound that clinicians treated for over a week before the patient demonstrated signs of progressive necrosis and sepsis. Finally, the patient underwent a transtibial amputation.    Six weeks later, surgeons fitted the patient with a prosthesis and he began rehabilitation. Although he took early retirement, the patient has returned to independent community ambulation. Had the surgeons performed the transtibial amputation after the failed toe amputation, three operations would have been eliminated from this patient’s five-stage below-knee amputation. His case illustrates the fact that in spite of our best efforts, all limbs with diabetic complications are not salvageable.    Both patients had low normal levels of serum albumin at approximately 3.0 gm/dl. Their total lymphocyte counts were both above 1,700. Their ankle brachial indices were about 0.3 before their vascular procedures and 0.45 afterward. They both had heart disease but who had more severe heart disease? The 58-year-old patient had worse control but the 62-year-old patient had early renal disease. If one measured the degree of control, nutritional status, renal function and cardiac function, would a significant difference between the two in any of these parameters be predictive of their eventual outcome? Right now, we do not know but the fact that many limb salvage attempts fail suggests we should find out.

Why There Is A Need For Enhanced Limb Salvage Criteria

   A recent study performed at the University of Texas Health Science Center in San Antonio reviewed 277 diabetic patients who underwent a first amputation between 1993 and 1997. This study included patients who had partial foot amputations and those who had major lower extremity amputations. Researchers found that patients in their series were at greater risk for further amputation on the same side as the first procedure than they were for contralateral amputation. They concluded that this finding should influence clinicians to implement preventive efforts in patients undergoing a first amputation.1 While it is hard to disagree, one might also argue that the data suggests that patient selection criteria for distal procedures may need refinement in order to avoid multi-staged higher amputations.    In an earlier, thought-provoking study, Duggan reviewed 38 patients who underwent bypass procedures for critical limb ischemia and reported an 80 percent limb salvage rate, and a 58 percent three-year survival rate. However, only 25 percent of the patients were ambulating after these interventions.2 This study raises the question that even if limb salvage is successful, do all of these patients truly benefit, given the postoperative risks and potential morbidity associated with these efforts?    These studies and the two case histories demonstrate that while limb salvage remains an important goal for patients who suffer lower extremity complications of diabetes, aggressive limb salvage efforts may not benefit everyone. To date, we have relied on limited criteria to choose candidates for partial foot procedures as opposed to amputations at higher levels. Such criteria include Doppler studies, measurement of trancutaneous oxygen, evaluation of serum albumin and measurement of total lymphocyte counts. If we are going to avoid putting our sickest patients through multiple futile attempts at limb salvage, we need to expand and redefine this criteria.    Anecdotally, a closer look at patients in our facilities who fail limb salvage interventions suggests that diffuse vascular disease, uncontrollable infection, inadequate offloading and numerous medical conditions appear to be associated with failure of foot wound debridement and partial amputations. These medical conditions include chronic poor control of diabetes, hypoalbuminemia, renal disease and cardiac disease. Unfortunately, many patients who suffer lower extremity complications of diabetes also present with these comorbidities.    In making decisions about proceeding with heroic measures to save a limb, one needs to consider the severity of these conditions. When it comes to patients with the greatest number of metabolic factors working against them, one may need to consider high amputation at a level likely to heal as opposed to exposing them to all the risk and potential comorbidity associated with partial foot procedures, vascular interventions and prolonged antibiotic therapy. Taking these other factors into account may help tilt the decision-making process in one direction or another in borderline cases rather than relying only on the limited criteria now in common use.    Common criteria for predicting successful limb salvage include the ankle brachial artery index, transcutaneous p02, the evaluation of serum albumin and the total lymphocyte count. Although we may attempt limb salvage with some success in borderline cases, our experience indicates that breaching these criteria frequently leads to failure. One should rigorously apply both the established criteria and new criteria. There is a need now to take a scientific look at the measurements associated with poor control, renal failure and heart disease. Indeed, one should examine the patient’s hemoglobin A1c, pre-albumin, blood urea nitrogen, serum creatinine, creatinine clearance and cardiac ejection fraction. If we can establish correlations of these values with the success or failure of distal wound healing, it will improve our ability to predict the patients who are most likely to benefit from limb salvage interventions.

In Conclusion

   Clinicians need to know the difference between the interventions they can attempt and those they should attempt in treating limb-threatening infections in seriously ill patients with diabetes. It is no favor to put a patient through multiple, sometimes risky procedures on the road to an inevitable below-knee amputation. Transtibial and higher amputations are frequently viewed as clinical failures. However, one can argue that multi-staged transtibial or higher amputations are even worse failures. A good surgeon knows both how and when to perform the procedures in his or her armamentarium.    A refined limb salvage criteria that includes parameters beyond what we have used to date should reduce the number of failed procedures leading to transtibial and higher amputations. Patients who might be subjected to multiple procedures with a limited chance of success could proceed directly to a definitive procedure and focus on rehabilitation after suffering a serious lower extremity complication of diabetes. In such cases, a one-stage transtibial amputation may be a greater clinical success than putting a patient through multiple surgeries and spending months or even years trying to save a non-functional extremity. Dr. Sage is a Professor and Chief of the Section of Podiatry at the Department of Orthopaedic Surgery and Rehabilitation at the Loyola University Stritch School of Medicine. He is also a Staff Podiatrist at Edward Hines Jr. Veterans Affairs Hospital. Dr. Steinberg (shown) is an Assistant Professor in the Department of Surgery at the Georgetown University School of Medicine in Washington, D.C. He is a Fellow of the American College of Foot and Ankle Surgeons. For selected articles, see “A Guide To Transmetatarsal Amputations In Patients With Diabetes” in the July 2006 issue of Podiatry Today. Also check out the archves at www.podiatrytoday.com.
 

References:

1. Izumi Y, Satterfield K, Lee S, Harkless LB. Risk of reamputation in diabetic patients stratified by limb and level of amputation. Diabetes Care 29 (3) 566-570, March 2006.
2. Duggan MM, Woodson J, Thayer, et al. Functional outcomes in limb salvage vascular surgery. Am J Surg 168(2), 188-191, August 1994.
3. Pinzur MS, Stuck RM, Sage R, Hunt N, Rabinovich Z. Syme ankle disarticulation in patients with diabetes. JBJS 85-A, 1667-1672, September 2003.