Discussion
The objective of this study was to identify any predictive factors of limb salvage success for patients with diabetic foot complications. Many studies have focused on the risk factors of diabetic foot ulceration and independent causation of multiple potential etiologic agents. However, no published studies have examined the risk factors for major amputation after limb-salvage surgery. Risk factors are important in predicting the prognosis of ulceration, yet many patients already have intractable ulceration prior to hospital admission. As a result, these studies are less helpful for the prognosis of patients in need of surgery for complicated diabetic foot. This study differs from previous studies in that it suggests the clinical predictors of limb salvage surgery failure. In this study, Hb, WBC, and CRP were risk factors of limb salvage surgery, but HbA1c was not. This is not surprising, given that Hb, WBC, and CRP are risk factors for diabetic foot complication, and hence a reflection of the patient's general condition and the degree of wound inflammation. On the other hand, unlike our findings showing no significant relationship between HbA1c and limb salvage surgery outcomes, previous studies have reported that HbA1c is a risk factor for diabetic foot complications. Chronic renal failure is also an important risk factor for proximal osteotomy. In our study, 11 of 22 patients with chronic renal failure experienced limb salvage surgery failure. In previous reports, among chronic renal failure patients on dialysis who underwent limb salvage surgery, about 50% experienced failure and went to amputation. It has been reported that the risk of lower limb amputation is greater in diabetic foot patients with kidney disease. However, in this study, creatinine was not a significant risk factor. Why creatinine was not found to be a risk factor for salvage failure in our study, although it has been identified as a risk factor for major limb amputation in previous studies, cannot be explained satisfactorily. The authors supposed that the reason was that creatinine levels could be controlled directly depending on the treatment for renal failure, such as dialysis.
To reflect the uniqueness of the patients with diabetic foot complications, a simple analysis method, the ambulation state, was used in this study. This can be relatively easily measured through a simple conversation with the patient. We found that the higher the ambulation state prior to surgery, the more successful the limb salvage operation. In other words, the postoperative walking ability was proportional to one's walking ability before the surgery. CT angiogram was used to identify the status of the blood vessels prior to surgery and has been proven effective in prior studies. Nevertheless, no studies have examined the failure of limb salvage surgery using the results of CT angiography until now. In the results of this study, the greater the number of damaged vessels as shown on CT angiogram, the greater was the difference of the odds ratio between the two groups. When comparing each blood vessel, a reduced vascular patency was found to be associated with failure. The number of normal blood vessels and the condition of each of the blood vessels had an effect on the results. In addition, it is worth considering that the diameter of the blood vessels of the lower limb is associated with the clinical outcomes of limb salvage surgery. The vessel diameter and odds ratio are largest in the anterior tibial artery, followed by the posterior tibial artery, and last, the peroneal artery.
Stone et al. reported the 1-, 3- and 5-year survival rates of diabetic foot patients undergoing transmetatarsal amputation to be 73%, 68%, and 62%, respectively. In our study, the 5-year survival rate of the limb salvage group was 81.6%. This may be higher because we included a high proportion of patients with toe amputation. We also found that in our success and failure groups, the 6-month survival rates showed no statistically significant difference, but the 5-year survival rate of the limb salvage surgery success group was significantly higher, meaning that the patient's age and life expectancy may help guide further surgical treatment.