Diabetic foot ulcers combined with ischemia and infection can be difficult to treat. Few studies have quantified the level of blood supply and infection control required to treat such complex diabetic foot ulcers. We aimed to propose an index for ischemia and infection control in diabetic chronic limb-threatening ischemia (CLTI) with forefoot osteomyelitis. We retrospectively evaluated 30 patients with diabetic CLTI combined with forefoot osteomyelitis who were treated surgically from January 2009 to December 2016. After 44 surgeries, we compared patient background (age, sex, hemodialysis), infection status (preoperative and 1- and 2-week postoperative C-reactive protein [CRP] levels), surgical bone margin (with or without osteomyelitis), vascular supply (skin perfusion pressure), ulcer size (wound grade 0-3 using the Society for Vascular Surgery Wound, Ischemia, and foot Infection classification), and time to wound healing between patients with healing ulcers and those with nonhealing ulcers. Preoperative CRP levels and the ratio of ulcers classified as wound grade 3 were significantly lower and skin perfusion pressure was significantly higher in the healing group than in the nonhealing group (P < .05). No other significant differences were found between groups. This study demonstrates that debridement should be performed first to control infection if the preoperative CRP level is greater than 40 mg/L. Skin perfusion pressure of 55 mm Hg is strongly associated with successful treatment. We believe that this research could improve the likelihood of salvaging limbs in patients with diabetes with CLTI.