Isolated forefoot gangrene in the presence of a palpable posterior tibial artery pulse can be definitively managed with a Syme amputation, which leads to a relatively high functional status in these patients. A Syme amputation includes ankle disarticulation, removal of malleoli, and anchoring heel pad to the weight bearing surface. A viable heel pad is critical for surgical success of a Syme amputation, and it receives its blood supply from branches of the posterior tibial artery. An example of this post-operatively is shown in Illustration A.
Francis et al reviewed the charts of 26 dysvascular patients with forefoot necrosis who underwent Syme amputation. They found that 85% of the patients with a palpable posterior tibial pulse had a successful amputation in contrast to one out of four who did not have a palpable pulse before surgery. They concluded that the single most important feature for success with Syme amputations is to limit the operation to those patients with a palpable posterior tibial pulse before surgery.
Laughlin et al reviewed the surgical results and functional outcome of 52 patients treated with Syme amputations for forefoot gangrene. They found that 90% of the patients who had a posterior tibial artery with either a triphasic waveform or a normal pulse achieved a healed wound suitable for prosthetic wear after undergoing a Syme amputation. This is compared to only a 57% success rate in patients with compromised posterior tibial arterial flow.
1-A transmetatarsal amputation may be used initially to clear an infection before completing a more proximal ampuation. However, this would not be appropriate as definitive management due to its proximity to the infected and necrotic tissue distally.
2,4-An above or below knee amputation in the presence of a palpable posterior tibial artery would not be appropriate as significantly better functional results result from a more distal Syme amputation.
5-Soft tissue debridement, local wound care, and antibiotic therapy would not definitively treat forefoot gangrene.
Francis H 3rd, Roberts JR, Clagett GP, Gottschalk F, Fisher DF Jr. The Syme amputation: success in elderly diabetic patients with palpable ankle pulses. J Vasc Surg. 1990 Sep;12(3):237-40.
PMID:2398581 (Link to Abstract)
Laughlin RT, Chambers RB. Syme amputation in patients with severe diabetes mellitus. Foot Ankle. 1993 Feb;14(2):65-70.
PMID:8454236 (Link to Abstract)