Current Considerations In Performing Transmetatarsal Amputations

Adam R. Johnson, DPM, and Lee C. Rogers, DPM

With the recognition of limb salvage as a key to decreasing mortality and increasing the quality of life in patients with chronic non-healing ulcerations, the transmetatarsal amputation (TMA) has become a common procedure.1-4 The current epidemic of diabetes mellitus affects 7.8 percent of the population in the United States. Moreover, an additional 57 million individuals have been diagnosed with “pre-diabetes.”5

   One sequela of the disease is chronic non-healing neuropathic ulcerations of the lower extremities that put these individuals at risk for lower extremity amputation. In order to help preserve the quality of life in these patients, limb salvage is an obvious goal.

   In the current literature, there is a trend showing an increased mortality rate the more proximal the level of an amputation of a diseased limb.1,2 One study has shown one-year survival rates at 34 percent after above-the-knee (AKA) amputations and 60 percent after below-the-knee amputations (BKA).1 The five-year survival rates are even more dismal for AKA (10 percent) and BKA (28 percent).1 On the contrary, minor amputations consisting of digital amputations and other foot sparing amputations have improved survival rates to 81 percent at one year and 59 percent at five years.1

   The Strong Heart study has shown comparably poor outcomes after all types of amputation with the mortality rate being 76 percent at an average of 8.7 years of follow-up.2 As with previous studies, a trend for an increased mortality rate existed with proximal amputations in comparison to that of patients with minor amputation. Patients without amputation had a mortality rate of 24.6 per 1,000 person years whereas mortality rates for those who had digital amputations and BKA procedures were 114.8 and 143.7 per 1,000 person years respectively.

   Furthermore, not only does performing a minor amputation decrease the mortality rates in patients but it can also increase the quality of life by increasing independence, mobility, and the ability to return home sooner.1,4 The metabolic demand of walking with these procedures is increased in comparison to more proximal amputations that lead to a decreased speed of gait and decreased distance that can be achieved before reaching the maximum cardiopulmonary limit.6

   When a previously ambulating patient presents with a limb-threatening condition, one should attempt to preserve as much of the limb as possible.3 While the TMA is an ideal procedure for limb salvage, successful healing rates of TMA have ranged from 39 percent to 93.3 percent.7

   In addition, many studies have shown that even when authors have reported high rates of healing, additional procedures are often required secondary to wound dehiscence and infection.3,7 Accordingly, surgeons should educate potential TMA candidates on the risks involved and emphasize careful attention to details such as smoking cessation and tight blood glucose control. Researchers have shown that these are independent risk factors with failure of the procedure.8,9

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