Point-Counterpoint: Is An Initial TMA Better Than A Partial Ray Amputation in Patients With Diabetic Neuropathy?

Author(s): 
Valerie L. Schade, DPM, AACFAS, and Suhad Hadi, DPM, FACFAS

A Closer Look At Adjunctive Surgical Options

Cunha and coworkers discussed the role of tendo-Achilles lengthening procedures to further reduce forefoot pressures and prevent re-ulceration or proximal amputation in eight of 12 patients.7 They identified four patients who needed further debridement or progression to a TMA. However, their findings further validate the importance of preoperatively recognizing and addressing deformities that may ultimately compromise the successful outcome of a partial first ray amputation.

   Miller and colleagues further discuss the potential role of panmetatarsal head resection procedures in reducing forefoot pressures in an effort to prevent forefoot ulcerations and the potential risk of TMA.5

Recognizing The Benefit Of Post-Op Prosthetic Modifications

The recognition of progressive deformity pre- and post-amputation will allow for a more comprehensive prosthetic prescription that will more effectively sustain the foot at the level of a partial first ray amputation. It would behoove the surgeon to gain thorough knowledge as to the role of prosthetic modifications, individual and in combination, in an effort to achieve the best outcome for the patient.

   Amputation filler additions to full-contact accommodative insoles can compensate to various degrees for the loss of the hallux. Modifying shoes to include a carbon plate or rocker-type forefoot will further aid in offloading the forefoot.

   It is also crucial to note that the majority of patients who have associated comorbidities such as coronary artery disease, chronic obstructive pulmonary disease or advanced systemic disease will often require the use of assistive devices in gait, such as canes, walkers, etc. This can further facilitate modifications in walking speed to increase overall function in the prescription shoegear. One may also consider the addition of a dynamic ankle foot orthotic (AFO) device similar to that for patients with a transmetatarsal amputation in an effort to reduce some of the forces during gait that may increase forefoot and lateral weightbearing distributions.

   Ultimately, clinicians must be thorough in regard to post-procedure prosthetic prescriptions and work closely with prosthetists in an effort to sustain an acceptable functional outcome post partial first ray amputation.

Do Patients With First Ray Amputations Have Greater Function And Mobility Than Those Who Have Had TMAs?

In regard to biomechanical function, it has been widely accepted that a TMA provides a more stable base, a re-established metatarsal parabola and decreased energy expenditure in comparison to partial first ray amputations. However, more recent studies have further questioned these claims.

   Dillon and Fatone explain that once the amputation is beyond the metatarsal heads collectively, via transmetatarsal or tarsal level amputations, the respective foot length no longer contributes to power generation at the ankle.1 They also note that the outcome is equivalent to the loss of ankle power that occurs with a transtibial amputation, resulting in further compensation at the hip. Other similarities include walking speeds, which the study found to be comparable in patients with partial foot level amputations and transtibial amputations. This study further questions the increased function or mobility of patients who have had midfoot amputation when taking less than moderate walking speeds into account.

   Ultimately, these questions raise the need for further research and open the door to question the superiority in function, mobility and healing rates of a midfoot amputation in comparison to a partial first ray amputation.

How Psychosocial Factors Come Into Play With Amputation

Aside from the goals to attempt to achieve function, mobility and minimal deformity in amputation planning, one must also take into account patient factors such as quality of life and psychosocial considerations. Amputation resulting from prolonged ulcer or wound healing has already taxed the patient and his or her social network. Progression to amputation has the potential to further compromise quality of life.

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