Abstract
Objective
Diabetes-related foot complications could lead to amputation and death. Major amputations are known to yield higher mortality rate compared to minor amputations. In patients who already had a minor diabetic amputation, knowing the risk factors contributing to a major re-amputation is of great importance. This study aims to quantify the risk of major amputation following minor diabetic amputation and to investigate the systemic and local risk factors of the re-amputation event.
Methods
This is a retrospective comparative study among patients who had a minor amputation as a diabetic complication where one group had no subsequent amputation (Group 1) versus another group with subsequent major amputation (Group 2). The minimum follow-up period was of 24 months. The main outcomes were set as the frequency of major re-amputation and the independent systemic and the local risk factors such as wound healing complications, stump issues and the impact of using MRI-guided level for index amputation.
Results
Out of the 107 index amputations (97 patients), 70 cases (65 patients) did not present with subsequent amputations (Group 1) and 18 patients/cases (16.8 %) required a major amputation at the last follow-up (Group 2). The logistic regression analysis showed peripheral artery disease (PAD) and non MRI-guided index minor amputation as independent factors for higher subsequent major amputations (p = 0.04 and p = 0.02, respectively).
Conclusion
The risk of a major amputation following a diabetic minor amputation is not infrequent, almost 17 %. PAD was found to be the only independent systematic factor to positively correlate with the risk of major re-amputation. MRI-guided level of index amputation, at least 1 cm proximal to MRI bone infection sign, was significantly negatively correlated with re-amputation.
1
Introduction
Diabetes-related foot complications, such as neuropathy, peripheral artery disease and infection, could lead to amputation and mortality ,, . Though conservative surgery or limb-sparing surgery was shown to yield good to excellent results when indicated ,,, , amputation is sometimes necessary in severe cases of infection and/or necrosis. While it is expected that a major amputation could cause high rates of 5-year mortality, documented between 52 % and 80 % , minor amputation in similar diabetic population has been found to yield a 44 % risk of mortality at 5 years .
Re-amputation frequency and the risk factors for subsequent amputations have been infrequently investigated in the literature. Patients with peripheral artery disease (PAD) could encounter high rates of minor and/or major re-amputation . Patients with diabetes or PAD who had an index major and minor amputations showed high frequencies of ipsilateral or contralateral re-amputation, which could reach 37 % at 5 years ,, . Some authors found smoking and creatinine to be independent risk factors for re-amputation, be it minor or major .
The available data on the risk factors that could affect re-amputation is rare and information is lacking over which predisposing causes could affect a specific type of re-amputation. For instance, the subcategory of risk factors that could affect the rate of a major amputation following a minor amputation was seldom studied. Furthermore, the vast majority of published articles looked for the classic systemic risk factors that are thought to affect amputation rate in general. To this, we included and computed data related to local risk factors such as wound healing complications, stump issues during rehabilitation and the impact of using MRI-guided level for index amputation.
Hence, this study aims to look for independent systemic and local risk factors for subsequent major amputation following minor diabetic amputation.
2
Methods
2.1
Study design
This is a retrospective comparative study among patients who had a minor amputation as a diabetic complication where one group had no subsequent amputation (Group 1) versus another group with subsequent major amputation (Group 2). This was a continuous series of patients admitted and operated between January 2019 and August 2023. The minimum follow-up period was of 24 months. Approval from the Institutional Review Board was obtained prior to the study conduct. All patients had a vascular assessment with the vascular team via Echo Doppler studies. Arteriography and revascularization were conducted when needed. The study was conducted in accordance with the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) guidelines .
2.2
Inclusion and exclusion criteria
The inclusion criteria encompasses patients with a history of minor amputation due to diabetic complications. Diabetic patients with a history of minor amputation who needed revascularization prior to the index or subsequent amputation were also included. Exclusion criteria included (a) patients who had minor amputation due to PAD only, (b) incomplete electronic charts and (c) patients who had more than one minor diabetic amputation in the same limb. A period of at least 2 years of follow-up was required for inclusion.
2.3
Outcome definition and studied risk factors
Minor amputation was defined as an amputation at or below ankle level. Subsequent minor amputation includes an ipsilateral amputation at the same ray, different ray or proximal to index amputation but below the ankle. A subsequent major amputation was defined as an ipsilateral below or above knee amputation in this study. Cases where a subsequent minor amputation ended with a major amputation during the follow-up were counted in the subsequent major group.
The studied outcomes were the frequency of subsequent major amputation and the potential risk factors. Besides the classic systemic risk factors listed below, we decided to comprise some local risk factors because we hypothesized that they could be relevant to the study. The local risk factors included were: (a) wound healing delay or superficial infection, (b) stump issues during rehabilitation and (c) the use of MRI-guided level of index amputation. For the latter local risk factor, the level of index amputation was decided either based on clinical infection/necrosis and radiological signs or decided on clinical infection/necrosis and MRI signs. When MRI signs were taken into account, the bone level of amputation was at least 1 cm proximal to the intramedullary bone sign. This approach was used for all cases performed during the last 2 years of the study.
2.4
Study comparison
Group 1 included cases were no subsequent amputation was encountered following the index minor amputation. Group 2 was defined as those cases which ended with a major amputation following index surgery. The two groups were compared for baseline demographic data and systemic and local risk factors.
2.5
Data extraction and analysis
Demographic data and relevant risk factors were recorded for analysis. The recorded systemic variables were: age, sex, side, American Society of Anesthesiologists (ASA) score, hypertension (HTN), PAD, dyslipidemia, (DL=), coronary artery disease, (CAD), chronic kidney disease (CKD), smoking, hemoglobin (Hg) level, HbA1c level, and creatinine level, wound healing delay or superficial infection, stump issues during rehabilitation, and the use of MRI-guided level of index minor amputation.
2.6
Statistical analysis
Significance between means and proportions were analyzed using t-student and z-proportion tests for independent groups. Logistic regression analysis were conducted to look for correlation between systemic/local factors and the outcome of subsequent major amputation. Significance was set for p-values less than 0.05. StatsDirect was the used software to compute the statistical analyses.
3
Results
3.1
Demographic data of the sample
There were 107 index minor amputations in 97 patients (29 female, 68 men) with a mean age of 71.6 ± 11.8 years. The sample comprised 88 toe/ray amputation (82.2 %) and 19 midfoot amputations (17.8 %). Side distribution was as follows: 59 right side and 48 left side. MRI was conducted in 62 cases (58 %) to guide the level of index amputation while in remaining 45 cases the level of amputation was based on x-rays and clinical signs. The mean ASA score was 2.9 ± 0.46. The mean HbA1c was 8.2 ± 1.8. The mean Hg level was 10.8 ± 1.9 and the mean creatinine level was 1.7 ± 1.5. The mean follow-up period was 26.2 ± 6.5 months ( Table 1 ).
Table 1
Comparative demographic and risk factors of the sample.
| Characteristics | Total sample |
Group 1
(without subsequent amputation) |
Group 2
(with subsequent major amputation) |
p-value (comparing Groups 1 & 2) |
|---|---|---|---|---|
| Number of patients | 97 | 65 | 18 | – |
| Number of primary cases | 107 | 70 | 18 | – |
| Mean age | 71.6 ± 11.8 | 72.6 ± 13 | 71 ± 13 | 0.7 |
| Nb Female (%) | 27 (27.8 %) | 17 (26.1 %) | 7 (39 %) | 0.1 |
| Right Side (%) | 59 (55 %) | 33 (47 %) | 11 (61 %) | 0.2 |
| Mean ASA score | 2.9 ± 0.46 | 2.98 ± 0.45 | 3.1 ± 0.5 | 0.1 |
| Diabetes Duration | 20.2 ± 9.8 | 21.5 ± 10 | 20.6 ± 10 | 0.1 |
| HTN | 91 (85 %) | 60 (85.7 %) | 16 (89 %) | 0.5 |
| PAD | 62 (56 %) | 35 (50 %) | 14 (72.2 %) | 0.01 |
| DL | 54 (50.5 %) | 35 (50 %) | 6 (33.3 %) | 0.3 |
| CAD | 67 (62.6 %) | 45 (64.3 %) | 12 (67 %) | 0.8 |
| CKD | 39 (36.4 %) | 28 (40 %) | 8 (44.4 %) | 0.2 |
| Smoking | 42 (39 %) | 25 (35.7 %) | 6 (33.3 %) | 0.7 |
| Hemoglobin | 10.75 ± 1.9 | 10.8 ± 1.9 | 11 ± 2 | 0.3 |
| HbA1c | 8.2 ± 1.8 | 8.1 ± 0.5 | 8.25 ± 1.5 | 0.5 |
| Creatinine | 1.7 ± 1.5 | 1.6 ± 1.7 | 1.1 ± 0.6 | 0.4 |
| CRP | 15.8 ± 9 | 12 ± 8.4 | 17.2 ± 8 | 0.07 |
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