Table 3.
Logistic Regression Estimates of the Association between Risk Factors and Outcomes Following Index Amputation.
| Adjusted Odds Ratios (95% CI) | |||
|---|---|---|---|
| UHRA (n = 36) | Death within One Year (n = 36) | Composite (n = 74) | |
| Age | 1.01 (0.98–1.04) | 1.01 (0.98–1.04) | 0.98 (0.95–1.00) † |
| Male (Ref: Female) | 2.58 (0.93–7.17) † | 0.37 (0.15–0.89) * | 1.48 (0.73–3.01) |
| Non-white (Ref: White) | 1.48 (0.70–3.11) | 0.63 (0.28–1.44) | 0.99 (0.52–1.86) |
| Ambulatory status (Ref: Ambulatory) |
|||
| Ambulatory with assistance | 2.36 (0.86–6.51) † | 4.31 (1.20–15.49) * | 1.52 (0.72–3.21) |
| Non-ambulatory | 6.74 (1.74–26.18) ** | 4.13 (0.80–21.39) † | 1.44 (0.54–3.87) |
| Living status (Ref: Home) | |||
| Other | 0.97 (0.28–3.44) | 0.40 (0.67–2.41) | 0.80 (0.26–2.49) |
| Medical history | |||
| Stroke (Ref: No) | 0.84 (0.20–3.42) | 0.43 (0.08–2.30) | 1.24 (0.46–3.36) |
| Coronary artery disease (Ref: No) |
2.00 (0.88–4.58) | 3.93 (1.56–9.87) ** | 0.91 (0.48–1.72) |
| Myocardial infarction (Ref: No) | 0.91 (0.34–2.39) | 2.22 (0.86–5.76) | 1.50 (0.67–3.39) |
| Congestive heart failure (Ref: No) | 1.36 (0.61–3.04) | 4.90 (1.96–12.29) ** | 0.88 (0.43–1.84) |
| Hyperlipidemia (Ref: No) | 1.42 (0.64–3.15) | 0.91 (0.41–2.00) | 1.01 (0.53–1.93) |
| Atrial fibrillation (Ref: No) | 1.56 (0.68–3.59) | 2.49 (0.82–7.54) | 0.55 (0.25–1.21) |
| Chronic obstructive pulmonary disease (Ref: No) | 2.31 (0.87–6.08) † | 2.26 (0.73–6.98) | 1.17 (0.44–3.12) |
| End-stage renal disease (Ref: No) | 1.07 (0.46–2.48) | 7.54 (3.10–18.34) *** ‡ | 0.97 (0.46–2.04) |
| Diabetes mellitus (Ref: No) | 0.78 (0.32–1.94) | 1.05 (0.41–2.69) | 0.77 (0.34–1.73) |
| Malignancy (Ref: No) | 0.93 (0.35–2.51) | 1.61 (0.61–4.30) | 1.61 (0.64–4.07) |
| Smoking Status (Ref: Never) | |||
| Former | 1.10 (0.46–2.65) | 0.53 (0.22–1.28) | 1.22 (0.59–2.52) |
| Current | 0.37 (0.09–1.55) | 1.05 (0.26–4.15) | 1.18 (0.39–3.53) |
| Medications | |||
| Statin (Ref: No) | 2.39 (0.84–6.78) | 1.73 (0.65–4.61) | 1.57 (0.76–3.24) |
| Antiplatelet (Ref: No) | 2.02 (0.78–5.24) | 1.03 (0.45–2.37) | 0.74 (0.37–1.47) |
| Anticoagulation (Ref: No) | 3.33 (1.43–7.72) ** | 0.70 (0.26–1.93) | 1.43 (0.69–2.98) |
| Dual antiplatelet (Ref: No) | 1.87 (0.71–4.93) | 1.74 (0.72–4.17) | 0.94 (0.45–2.00) |
| Optimal medical therapy (Ref: No) | 1.92 (0.83–4.48) | 1.34 (0.59–3.06) | 0.88 (0.46–1.68) |
| Non-invasive vascular testing | |||
| Abnormal waveform—femoral (Ref: Multiphasic) | ----- | 1.15 (0.08–17.35) | ----- |
| Abnormal waveform—popliteal (Ref: Multiphasic) | 1.53 (0.44–7.14) | 1.79 (0.48–6.73) | 1.07 (0.40–2.88) |
| Abnormal waveform—ankle (Ref: Multiphasic) | 3.12 (1.30–7.46) * | 1.59 (0.67–3.77) | 1.53 (0.75–3.13) |
| ABI (Ref: 0.8–1.4) | |||
| 0.5–0.8 | 2.88 (0.79–10.48) | 1.82 (0.45–7.39) | 1.16 (0.41–3.32) |
| ≤0.5 | 2.76 (0.50–15.16) | 0.87 (0.17–4.44) | 0.61 (0.19–1.99) |
| Invalid | 0.97 (0.33–2.80) | 4.79 (1.44–15.29) * | 0.71 (0.30–1.65) |
| Toe pressure (Ref: ≥30 mm Hg) | |||
| <30 mm Hg | 4.89 (1.52–15.78) ** | 2.82 (0.75–10.66) | 1.18 (0.37–3.75) |
| 0 mm Hg | 1.16 (0.36–3.73) | 3.34 (0.98–11.36) † | 0.74 (0.29–1.86) |
| Angiographic findings Patent genicular arteries (Ref: 4 or 5) |
|||
| ≤3 | 1.11 (0.45–2.75) | 0.47 (0.16–1.35) | 1.43 (0.65–3.19) |
| WIfI 1-year amputation risk (Ref: Very low/low risk) | |||
| Moderate/high risk | 1.13 (0.37–3.46) | 4.55 (0.94–22.10) † | 1.89 (0.80–4.51) |
| Index amputation type (Ref: Toe) | |||
| TMA | 1.64 (0.51–5.23) | 2.39 (0.64–8.88) | 0.66 (0.19–2.23) |
| BKA | 0.22 (0.05–0.98) * | 1.00 (0.36–2.81) | 0.34 (0.15–0.74) ** |
| TKA or AKA | 0.15 (0.02–1.15) † | 1.28 (0.42–3.93) | 0.22 (0.09–0.58) ** |
| Indication (Ref: Dry gangrene) | |||
| Any infection | 0.42 (0.17–1.03) † | 0.35 (0.13–0.90) * | 1.08 (0.52–2.27) |
| Nonhealing wound or rest pain | 1.18 (0.32–4.33) | 0.73 (0.21–2.62) | 0.82 (0.33–2.09) |
| Infection (Ref: None) | 0.35 (0.15–0.78) * | 1.31 (0.48–3.52) | 0.72 (0.35–1.50) |
| Partially open or open index amputation (Ref: Closed) | 0.57 (0.25–1.29) | 1.00 (0.38–2.65) | 2.49 (1.18–5.23) * |
| Revascularization prior to or concomitant to index amputation (Ref: No) | 2.19 (0.88–5.49) † | 0.81 (0.35–1.86) | 0.89 (0.46–1.71) |
| Revascularization after index amputation (Ref: No) | 2.16 (0.89–5.24) † | 0.45 (0.12–1.65) | ----- |
| Debridement after index amputation (Ref: No) | 4.18 (1.13–15.50) * | 0.47 (0.10–2.26) | ----- |
| UHRA (Ref: No) | ----- | 2.00 (0.76–5.25) | ----- |
N = 203 index amputations. N in estimation sample may be smaller due to case-wise deletion of missing data and/or small cells. CI, confidence interval; TMA, transmetatarsal amputation; BKA, below-knee amputation; TKA, through-knee amputation; AKA, above-knee amputation; ABI, ankle-brachial index; WIfI, wound, infection, and ischemia index. †, p < 0.10; *, p < 0.05; **, p < 0.01; ***, p < 0.001. All variables measured at index amputation. Parameter estimates are from logistic regression models controlling for amputation type, sex, race, and age. All other patient characteristics were included in models for each one separately due to the small sample size. ‡, remains significant after Bonferroni correction for 37 tests (implies lowering p < 0.05 to p < 0.0014).