Swelling, warmth, pain. Abscess, deep space infection of left Syme stump? The patient has undergone a Syme-like amputation through the ankle, with the associated expected postoperative changes. There is irregularity of the skin surface along the lateral aspect of the ankle suggesting ulceration. The underlying subcutaneous fat is replaced with heterogeneous signal intensity compatible with edema and scarring. There is perhaps a small, elongated thin collection of fluid within the soft tissues superficial to the fibula, but this is difficult to determine with certainty in the absence of contrast enhancement. I see no frank drainable abscess. Bone marrow signal intensity of the fibula is within normal limits, without evidence of osteomyelitis. The distal end of the stump representing the plantar "heel pad" appear slightly edematous, but largely maintains normal fat signal intensity. Between the heel pad and the distal ends of the tibia and fibula is a heterogeneous collection of tissue representing a surgically created muscular flap which shows high signal intensity on T2-weighted images that may reflect edema, although such signal can also be a normal finding in muscular flaps. This is admixed with low signal intensity that I suspect represents a combination of scar tissue, heterotopic ossification and residual tendinous structures. Increased signal intensity on T2WI deep to the musculature along the inferomedial aspect of the distal tibia may represent edema or perhaps a phlegmon, but I see no well-defined fluid collection to confirm an abscess. Multiple foci of signal void represent metallic susceptibility artifact from the surgery, as I see no gas density on the radiographs. There is mild periosteal reaction along the distal tibia that I suspect is chronic in etiology, as mild periosteal reaction is seen on ankle radiographs dating back to 2013. There is also mild edema-type signal within the medial aspect of the remaining distal tibia; although I cannot exclude osteomyelitis, the overlying cortical bone appears relatively preserved and hence this may simply represent reactive edema.
Postoperative changes of Syme amputation with soft tissue ulceration and inflammation as described above. There is an equivocal thin elongated fluid collection underlying the lateral ulcer, as well as poorly defined increased signal intensity on T2WI between the muscular flap and the distal tibia medially that could represent a phlegmon, but I see no well-developed abscess given the limitations of a nonenhanced study. Mild edema of the bone marrow of the medial aspect of the distal tibia is nonspecific and while I cannot exclude osteomyelitis this may simply represent reactive edema associated with adjacent soft tissue inflammation.