What are the risks of a transmetatarsal amputation if diabetic?

Complicated. The answer to this question is complicated and is best addressed by your surgeon as part of a preoperative discussion of the risks and benefits of the surgery. Only with a detailed discussion can the potential benefits be weighed against the risks and an informed decision made.
Alteration of gait. Risk of any surgery include: pain, swelling, numbness, infection, delayed healing, no-healing and possible need for further surgical management. Following a trans-metatarsal amputation people will be able to walk however they may experience an alteration in their gait.

Related Questions

What are the risks of a below the knee amputation to a diabetic?

Complicated. The answer to this question is complicated and is best addressed by your surgeon as part of a preoperative discussion of the risks and benefits of the surgery. Only with a detailed discussion can the potential benefits be weighed against the risks and an informed decision made.
Many risks. Risk of any surgery include: pain, swelling, numbness, infection, delayed healing, no-healing and possible need for further surgical management. Following an amputation people will be able to walk with a prosthesis, however they may experience an alteration in their gait.