Point-Counterpoint: Is An Initial TMA Better Than A Partial Ray Amputation in Patients With Diabetic Neuropathy?
As we continue to witness a decrease in below-knee level amputations and an increase in partial foot level amputations, the questions surrounding their longevity and benefits come further into play.1 Partial foot amputations in general have been under scrutiny in regard to what we can consider a low success rate of maintained healing regardless of amputation level.
Research has shown that 30 percent of all partial foot level amputations require secondary amputation regardless of the specific levels, a percentage that includes partial first ray amputations and transmetatarsal amputations (TMAs).1 Despite the fact these rates are twice as high as transtibial amputation rates, we continue to recognize the increase in partial foot amputations and the efforts to increase their functionality and longevity.
What The Literature Reveals
There is much literature in support of midfoot level amputations (and the TMA in particular) but there is a noted paucity in regard to more recent outcomes in support of partial ray amputations, specifically those of the first ray.
Many studies have identified the associated risk of more proximal amputation in patients who undergo a partial first ray amputation.1-5 The risk of more proximal amputation ranges from 25 to 40 percent.1-5 In a retrospective review of 30 patients who had a partial first ray amputation, Kadukammakal and colleagues found that nine of these patients (30 percent) had a subsequent TMA at one-year follow-up.4 However, of those 12 patients undergoing a TMA, six had an ischemic component, which would initially be a greater indicator of the potential of more proximal amputation.
Furthermore, Borkosky and Roukis performed a systematic review of studies involving any form of partial first ray amputation in an effort to identify the incidence of re-amputation in patients with diabetic neuropathy.3 They ultimately concluded that one out of every five patients had re-amputation. However, there was no indication — in the form of ischemia, infection or both — as to why further amputation was necessary. Ultimately, this review found only a 19.8 percent re-amputation rate following partial first ray amputation, which was 5 to 20 percent lower than in previous studies.4-6 However, the authors went on to recognize and question the potential for a reduction in numbers if appropriate bracing techniques were in place.3
Being critical of the literature and the emphasis on reported re-amputation rates often leaves one failing to interpret and recognize the success rates ranging from 60 to 80 percent of patients maintaining a successful, functional and healed outcome with a partial first ray amputation.6 Ultimately, one must recognize that the trend in reviewing the outcome studies tends to demonstrate a progressive decline in re-amputation rates with partial first ray amputations. Therefore, it is premature to exclude this procedure from one’s armamentarium in regard to amputation planning.
Often with surgical planning, we consider partial first ray amputations an initial debridement in an effort to eradicate infection, regardless of parameters — such as appropriate infection control and intact vascular status — supporting overall healing at that level. There is always the fear of the lateral transfer of weightbearing forces to the residual foot and subsequent transfer lesions as a consequence of reported forefoot sequelae.2 It is the common progression for amputations at the first ray level to demonstrate lesser digital contractures at the proximal interphalangeal and metatarsophalangeal joints, anterior advancement of the plantar fat pad and subsequent potential for transfer lesions.
These factors and the implied increased risk of re-ulceration and further risk of infection or more proximal amputation often lead surgeons to contemplate a midfoot level amputation in the hopes of a more successful outcome. It is, however, the understanding of these sequelae that should instead reinforce the benefits of implementing further adjunctive surgical planning and prosthetic measures to maximize the long-term outcomes of partial first ray amputations.5,7