A neuropathic ulcer was defined as a full-thickness skin defect produced, in the absence of ischemia, as the consequence of loss of protective sensation or of a deformity due to a motor neuropathy, sometimes aggravated by autonomic alterations. Callus is observed covering the lesion or at its margins, and these ulcers usually bleed easily. Neuropathic ulcers often appear at points of sustained low pressure or shear over a bony prominence.

A neuroischemic ulcer is a full-thickness skin wound whose underlying cause is both peripheral neuropathy and peripheral arterial disease. Despite ischemia, symptoms may be absent. The wound base is ulcerous, sphacelated, or necrotic. Bleeding is absent or only slight. Neuroischemic ulcers often appear in the dorsal and lateral zones of the foot as the consequence of a small traumatic injury or shear.

Neuropathy was diagnosed by examining 10 sites on the foot using a Semmes-Weinstein monofilament 5.07 10 g (Sensifil-Novalab Ibérica, Madrid, Spain) and a Horwell 997 neurotensiometer (Sensifil-Novalab Ibérica). Vascular involvement was defined as an ankle-arm index <0.8, transcutaneous oxygen tension (TcPo2) (using a TCM4 transcutaneous monitor; Radiometer Medical, Brønshøj, Denmark) <30 mmHg, and lack of a dorsal pedal and posterior tibial pulse. Wound infection was clinically defined according to the criteria of the International Working Group on the Diabetic Foot (IWGDF) as the presence of two or more signs and symptoms of local inflammation or systemic signs of infection of no other apparent cause, along with a purulent exudate. In addition, we also looked for specific signs such as necrosis, delayed wound healing, foul odor, and bone exposure. Soft tissue specimens for culture were obtained after brief cleaning of the ulcer surface with saline and sterile gauze. Samples of exudate were obtained by rubbing the surface with a sterile cotton swab, and deep tissue samples were obtained using a no. 10 or 15 scalpel blade (CE 0086; Swann-Morton, Sheffield, U.K.). Specimens were transferred to a sterile vessel containing transport medium (CE 0344; Copan Innovation, Brescia, Italy) and submitted to the microbiology laboratory for culture. We assessed the ulcers according to the classification schemes of Wagner and Texas to record the extension and depth of all soft tissue lesions and detect any evidence of bone infection. In addition, a PTB test was performed in all patients using a blunt, sterile, metal surgical instrument to gently explore the ulcer. The test result was scored positive when a hard substance assumed to be bone was palpated accompanied or not by deep sinus tracts. The PTB was always conducted by the same experienced podiatrist.