European Journal of Cardiovascular Medicine

The prognostic relevance of clinical limb staging in chronic limb-threatening ischemia (CLTI) has been underscored by work showing that higher stages predict worse limb salvage and amputation-free survival after first-time revascularization [1]. At the same time, durable surgical options remain necessary for complex infra-popliteal disease.  Even revascularization to isolated popliteal segments can be a viable limb-saving strategy in carefully selected patients with critical ischemia [2]. Optimizing outcomes also depends on coordinated perioperative and wound care.  Multidisciplinary programs have demonstrated superior amputation-free survival compared with fragmented care models [3].

Against this clinical backdrop, the global burden of peripheral arterial disease (PAD) continues to rise affecting hundreds of millions worldwide with the steepest growth in lower- and middle-income groups, which makes standardized triage and effective revascularization strategies a public-health priority [4]. Earlier consensus has emphasized on anatomical lesion patterning to steer therapy selection recommending bypass surgery for extensive infrainguinal disease and endovascular therapy for focal lesions [5].  To refine clinical risk stratification beyond anatomy alone, the Society for Vascular Surgery introduced the Wound, Ischemia, and foot Infection (WIfI) classification, which provides a unified language to estimate amputation risk and likely benefit of revascularization [6]. On top of that, the Global Vascular Guidelines proposed the Global Limb Anatomic Staging System (GLASS) to stage target-artery-path complexity and support procedural planning alongside clinical staging [7].

Study objective.

In this context, we evaluated outcomes of below-knee autologous vein bypass grafting for CLTI using an integrated framework consisting of preoperative SVS WIfI for clinical severity and GLASS for anatomic complexity.  We quantified progressive changes in WIfI components and total score, reported 1-year limb salvage and major amputation, and explored how anatomical severity is related to clinical recovery.

Study Design and Setting This was a retrospective single-centre observational study conducted at the Vydehi Institute of Medical Sciences and Research Centre in Bangalore, India between February 2021 and February 2024. The study was performed in accordance with the Declaration of Helsinki and approved by the Institutional Ethics Committee. All patients provided informed consent for surgical intervention and follow-up data collection. Study Population The study included 23 patients diagnosed with chronic limb-threatening ischemia (CLTI) who underwent below-knee autologous vein bypass grafting for limb salvage during the study period. Inclusion Criteria The study included patients with clinically and radiologically documented peripheral arterial disease (PAD) presenting with at least one of the following: • Ischemic rest pain • Post-toe amputation with persistent ischemic symptoms • Non-healing ulcer persisting >2 weeks • Gangrene involving any part of the lower limb or foot Exclusion Criteria Patients were excluded in case of the following: • Pure venous or neuropathic ulcers • Traumatic wounds • Acute limb ischemia (<2 weeks duration) • Non-atherosclerotic vascular disease (e.g., vasculitis, radiation-induced arteriopathy) Preoperative Assessment and Risk Stratification Each patient underwent detailed clinical evaluation, hemodynamic assessment, and imaging (duplex ultrasound, computed tomography angiography, or digital subtraction angiography). Limb severity was graded preoperatively using: 1. The Society for Vascular Surgery (SVS) WIfI classification, which comprises of Wound, Ischemia, and foot Infection components 2. The Global Limb Anatomic Staging System (GLASS), which is based on target artery path complexity and anatomical feasibility for revascularization. Surgical Technique All procedures were performed under a standardized protocol under spinal anaesthesia by the same vascular surgery team. The ipsilateral great saphenous vein was used as the preferred conduit. When it is unavailable, inadequate, or of poor quality, the contralateral great saphenous vein was used. Proximal and distal anastomoses were selected according to preoperative imaging and intraoperative vessel condition. After the arterial anastomotic sites of interest were exposed and the saphenous veins were harvested, systemic heparin (100 IU/kg intravenous) was administered prior to arterial clamping. The long saphenous vein was used in a reversed fashion and end to side anastomosis was done for the proximal and distal sites with some having a sequential side to side anastomosis. Graft patency and distal arterial flow was verified intraoperatively using a handheld Doppler ultrasound. Postoperative Management and Follow-Up Postoperatively, all patients received intravenous heparin and nicorandil infusion for 24–48 hours followed by dual antiplatelet therapy (aspirin 75 mg + clopidogrel 75 mg daily), which was continued after discharge. Patient evaluations were performed at the time of discharge, 6 months, and 1 year later, which included the following: • Wound and infection assessment • Palpable pulse examination and Doppler ultrasonography for graft patency • WIfI reclassification at each time point Outcome Measures Primary Outcomes 1. Change in WIfI component and total scores over time (baseline, discharge, 6 months, and 1 year). 2. One-year limb salvage rate and major amputation rate. Secondary Outcomes 1. Comparison of WIfI score improvement between GLASS II and GLASS III anatomical stages. 2. Correlation between baseline WIfI score and degree of improvement at 1 year. 3. Comparison of study outcomes with international benchmarks. Statistical Analysis The data was entered and analyzed using IBM SPSS Statistics version 27 (IBM Corp., Armonk, NY, USA). Prior to the analysis, the dataset was screened for completeness, outliers, and consistency. Continuous variables were summarized as median with interquartile range (IQR) owing to non-normal distribution while categorical variables were presented as frequencies and percentages. The assumption of normality was evaluated using the Shapiro–Wilk test. To assess changes in ordinal WIfI parameters (wound, ischemia, foot infection, and total score) across repeated follow-up time points—baseline, discharge, 6 months, and 1 year—the Friedman test was employed. This non-parametric test was chosen as it accommodates repeated measures of data that are not normally distributed. When the Friedman test indicated a significant overall difference, post hoc Wilcoxon signed-rank tests with Bonferroni adjustment were used to identify pairwise differences between time points. Comparisons between GLASS II and GLASS III anatomical groups were conducted using the Mann–Whitney U test, which is appropriate for small independent samples with ordinal or non-normally distributed data. Correlations between baseline WIfI severity and one-year improvement were examined using Spearman’s rank correlation coefficient (ρ). All statistical tests were two-tailed, and a p-value of < 0.05 was considered statistically significant. The strength of effect for the Friedman analysis was reported using Kendall’s W, which is interpreted as small (≤0.3), moderate (0.3–0.5), or large (>0.5).

A total of 23 patients with chronic limb-threatening ischemia (CLTI) underwent below-knee bypass surgery between February 2021 and February 2024 at Vydehi Institute of Medical Sciences and Research Centre, Bangalore.

All procedures were performed by the same vascular team following a standardized protocol.

Pre-operative assessment included SVS WIfI classification (wound, ischemia and foot infection) and GLASS anatomical staging based on imaging.  Follow-up evaluations were available at discharge, 6 months, and 1 year for every patient allowing complete longitudinal comparison of WIfI component scores, derived WIfI stages, and clinical outcomes.

The study cohort had a mean age of 51.0 ± 16.8 years with 20 (87%) males and 3 (13%) females.  Pre-operative GLASS staging identified 16 (69.6%) patients as GLASS II and 7 (30.4%) patients as GLASS III.  All 23 patients had reached 1-year follow-up, and no records were lost to follow-up.  Table 1 summarizes demographic and baseline anatomical characteristics of the cohort.

Table 1 – Baseline Characteristics of the Study Population

2. Primary Outcomes

2.1 Changes in WIfI Component Scores and Total Score Over Time

Significant and sustained clinical improvement was observed following below-knee bypass grafting. Wound, ischemia, and infection components of the Society for Vascular Surgery (SVS) WIfI classification improved consistently throughout follow-up (p < 0.001 for all). Median total WIfI scores decreased from 5 (IQR 4–6) at baseline to 2 (IQR 1–2) at 1 year representing an approximate 60% reduction in overall disease severity.

Most of the improvement occurred within the first 6 months after which the scores plateaued and remained stable through 1 year.  These findings confirm the effectiveness of surgical revascularization in promoting wound healing, improving perfusion, and achieving sustained infection control in patients with CLTI.

Friedman analysis results are summarized in Table 2, and median component scores at each time point are shown in Table 3.  The temporal improvement trend is illustrated in Figure 1 (boxplots of WIfI components and total score) and Figure 2 (median WIfI total score trajectory).

Table 2. Friedman Test Results for Change in WIfI Components and Total Score Over Time (N = 23)

Friedman test comparing repeated measures across baseline, discharge, 6 months, and 1 year.

Table 3. Median (IQR) of WIfI Components and Total Score at Each Time Point

Values expressed as median (interquartile range). All domains demonstrated significant improvement over time (Wilcoxon signed-rank test, baseline vs 1 year, p < 0.001).

Figure 1. WIfI Component and Total Scores Over Time:

Boxes represent the interquartile range (IQR), horizontal lines indicate median values, and whiskers denote minimum and maximum scores. Progressive downward shifts in medians and narrowing of IQRs reflect significant improvement over time (p < 0.001, Friedman test).

Figure2.  Median SVS WIfI Total Score Over Time Following Below-Knee Bypass

The median score declined progressively from baseline to one year with narrowing interquartile ranges indicating improved limb severity and healing outcomes (p < 0.001, Friedman test).

2.1.1 Component-wise Improvement in SVS WIfI Grades

Progressive improvement was observed across all three WIfI clinical components following below-knee bypass surgery (Table 3A).  Median wound, ischemia, and foot infection grades decreased consistently over time, which reflects improved wound healing, enhanced limb perfusion, and effective infection control. The reductions across all domains were statistically significant (p < 0.001, Friedman test).

Table 3A. Component-wise Improvement in WIfI Grades (Median [IQR]) Following Below-Knee Bypass

3. Secondary Outcomes

3.1 Comparison of Outcomes Between GLASS II and GLASS III Groups

All patients were stratified preoperatively according to the Global Limb Anatomic Staging System (GLASS) into GLASS II (n = 16, 69.6%) and GLASS III (n = 7, 30.4%) categories.  Both groups demonstrated significant improvement in all WIfI components and in the total WIfI score following below-knee bypass.

Non-parametric intergroup comparison using the Mann–Whitney U test revealed similar improvement trajectories across both anatomical stages.

At the time of discharge, GLASS III patients had slightly higher wound scores (median 2 vs 1) suggesting more severe presentation (p = 0.045).

However, at 6 months and 1 year, there were no statistically significant differences between GLASS II and GLASS III groups in wound, ischemia, infection, or total SVS WIfI scores (p > 0.05 for all).

The corresponding intergroup comparisons are summarized in Table 4.

Table 4. Comparison of WIfI Component and Total Scores Between GLASS II and GLASS III Groups

NS = not significant. Mann–Whitney U test comparing GLASS II (n=16) vs GLASS III (n=7).

Both GLASS II and GLASS III groups showed comparable clinical improvement following surgical revascularization.
The higher early wound scores in GLASS III reflect greater anatomic complexity but did not translate into poorer long-term outcomes.

After one year, SVS WIfI components and total scores had improved to similar levels in both subgroups, which indicates that bypass surgery can achieve equivalent clinical benefit across varying anatomical disease severities.

3.2 SVS WIfI Stage Progression and Clinical Downstaging

Longitudinal evaluation of SVS WIfI stage demonstrated a consistent pattern of clinical downstaging following below-knee bypass grafting.  The median SVS WIfI stage decreased from Stage 2 at baseline to Stage 1 at one year, which is a statistically significant reduction (p < 0.001, Friedman test).

Overall, 20 out of 23 patients (87%) demonstrated an improvement of at least one stage in SVS WIfI score at 1 year while 3 patients (13%) remained stable.  No one experienced worsening of SVS WIfI stage during follow-up.

On the other hand, 14 of 16 (87.5%) GLASS II patients and 6 of 7 (85.7%) GLASS III patients achieved improvement.  The degree of downstaging was comparable between the two groups.  The stage migration summary is presented in Table 5, and the temporal distribution of stages is illustrated in Figure 3.

Table 5. WIfI Stage Migration from Baseline to 1 Year

Δ Stage calculated as baseline – 1 year (negative value indicates improvement).

Figure 3. Distribution of WIfI Stages at Baseline, Discharge, 6 Months, and 1 Year

The above figure illustrates the proportion of patients in each WIfI stage at successive follow-up timepoints. A progressive decrease in the proportion of Stage 2–3 limbs and an increase in Stage 0–1 limbs were observed after revascularization, reflecting sustained improvement in wound healing, perfusion, and infection control throughout the first postoperative year (p < 0.001, Friedman test).

4. Amputation and Limb Salvage Outcomes

4.1 Major Amputation Within 1 Year

During the 12-month follow-up period, major amputation (defined as amputation above the ankle) occurred in 1 of 23 patients (4.3%) while 22 patients (95.7%) retained their limbs at one year.  No perioperative mortality or 30-day major amputation was recorded.

The single patient requiring major amputation presented with advanced tissue loss (WIfI Stage 3, GLASS III) and persistent ischemic rest pain in spite of revascularization with a technically patent graft flow on early postoperative Doppler assessment.  No patient in the GLASS II group underwent major amputation within one year.  No other perioperative deaths or early amputations were observed.  All patients who achieved WIfI downstaging to Stage 0 or 1 by 6 months had maintained limb integrity at one year.

Table 6. Major Amputation and Limb Salvage Outcomes at 1 Year

Major amputation defined as amputation above the ankle. Percentages based on group totals.

Figure 4. One-year major amputation and limb salvage outcomes following below-knee bypass.

The chart illustrates the overall limb salvage rate (95.7%) and major amputation rate (4.3%) in the study cohort. The single amputation occurred in a patient with GLASS III anatomy and persistently high WIfI scores postoperatively. No patient with GLASS II disease underwent major amputation, and no perioperative deaths were recorded.

4.2 Limb Salvage (Composite Endpoint) and Association with WIfI Improvement

A composite endpoint of limb salvage was defined as an absence of major amputation within one year and ischemia score ≤ 1 at one-year follow-up.  By this definition, 22 of 23 patients (95.7%) achieved limb salvage at one year following below-knee bypass grafting (Table 7). The single patient who failed to meet this endpoint had persistent ischemia and tissue loss (WIfI total score ≥ 6) in spite of a technically patent graft flow on postoperative Doppler evaluation.

Among patients stratified by anatomical stage, limb salvage was achieved in all GLASS II cases (100%) and in 6 of 7 GLASS III cases (85.7%).  All patients who achieved a reduction in ischemia score to ≤ 1 at one year-maintained limb integrity.

Descriptive analysis demonstrated that greater reductions in total WIfI score and downstaging to lower WIfI categories were observed in patients who achieved limb salvage.  On the other hand, a persistently high WIfI score was observed in the single amputation case.  No additional major adverse limb events were recorded during follow-up.

Table 7. Limb Salvage at One Year (Composite Endpoint)

Composite endpoint derived from patient-level amputation status and ischemia score at one year.

Table 8. Limb Salvage by GLASS Anatomical Stage

Figure 4. Limb Salvage and Major Amputation Rates by GLASS Stage

Figure 4. Clustered column chart showing limb salvage and major amputation rates at one year following below-knee bypass, stratified by GLASS anatomical stage. Limb salvage was achieved in all GLASS II patients and in 85.7% of GLASS III patients.

5. Correlation Between Baseline WIfI Severity and Improvement.

An exploratory correlation analysis was performed to assess the relationship between baseline WIfI scores and the magnitude of improvement at one year (ΔWIfI = baseline – 1-year total score). The non-parametric Spearman rank correlation coefficient (ρ) was used due to non-normal distribution of ordinal data. A weak negative correlation was observed between baseline WIfI score and magnitude of improvement (ρ = –0.32, p = 0.14). Although it is not statistically significant, this trend suggests that patients with higher baseline WIfI severity tended to experience greater relative improvement following successful revascularization.

No significant correlation was found between baseline ischemia component scores and improvement in total WIfI score (ρ = –0.18, p = 0.41).  Similarly, baseline wound and infection sub scores demonstrated insignificant relationships with total WIfI improvement at 1 year.

These findings are summarized in Table 8.

Table 8. Spearman Correlation Between Baseline WIfI Components and Change in Total WIfI Score (Baseline – 1 Year)

ρ = Spearman correlation coefficient; ΔWIfI = baseline – 1-year total score; NS = not significant.

Below-knee bypass grafting for chronic limb-threatening ischemia resulted in significant clinical improvement across all WIfI domains with corresponding reductions in total WIfI scores and overall downstaging during follow-up.  Improvement was most pronounced within the first six months and was sustained at one year.  A strong trend toward progressive WIfI downstaging was observed with 87% of patients improving by at least one stage and none worsening during follow-up.

Outcomes were comparable between GLASS II and GLASS III anatomical stages, which indicates that anatomical complexity did not adversely affect short- or mid-term clinical recovery when revascularization was achieved. 

Exploratory correlation analysis demonstrated a weak negative association between baseline WIfI severity and magnitude of improvement suggesting that patients with higher baseline limb threat still derive substantial benefit following bypass surgery.

Overall, these results demonstrate consistent clinical improvement, high limb salvage, and comparable outcomes across anatomical severities following below-knee bypass grafting for CLTI in this single-centre cohort.

Below-knee bypass surgery using autogenous vein grafts achieved substantial clinical improvement and durable limb salvage in patients with chronic limb-threatening ischemia (CLTI) in our single-centre experience. The outcomes of our study fall within the range of contemporary series of infrainguinal and below-knee bypasses for CLTI confirming the procedure’s continued efficacy when appropriate conduit and target selection are achieved.

Comparison with contemporary bypass outcomes

Recent registry and institutional data continue to support surgical bypass as a durable revascularization strategy for advanced CLTI. In a large Vascular Quality Initiative analysis, Cheng et al. (2025) reported one-year limb salvage of approximately 63% and primary patency below 35% after cryopreserved vein bypass.  This demonstrates the inferior performance of non-autogenous conduits and the importance of autologous vein use [8].  Our study using autogenous saphenous veins in all the cases had achieved a markedly higher one-year limb salvage rate of 95.7%, thereby, emphasizing the durability of autogenous conduits for tibial targets.

Similarly, Feliz et al. (2024) observed that after occlusion of an infrainguinal bypass, major amputation-free survival was 57% at 1 year, which had declined to 17% at 10 years [9]. Their findings highlight the progressive attrition of limb preservation once a graft fails reinforcing the need for early surveillance and reintervention—an aspect emphasized by our stable one-year outcomes.  Hirth-Voury et al. (2020) compared cryopreserved arterial allografts with heparin-bonded prostheses in infragenicular bypasses.  They found the 12-month patency rate to be 52–88% and amputation-free survival of 75–94% with WIfI stage 4 conferring a 13-fold higher amputation risk [10]. Our data mirrors this stage-dependent trend as an amputation occurred in a patient with a high baseline WIfI score.

Clinical correlation with WIfI staging

The pattern of WIfI score improvement observed in our series aligns closely with prior validation studies of this classification system. Robinson et al. (2017) demonstrated that increasing WIfI stage correlated directly with limb treatment intensity and inversely with one-year limb salvage (96% in stage 1 vs 78% in stage 4; P = .003) [11].  Similarly, a multicentre bypass cohort by Kohler et al. (2024) showed that WIfI stage 4 patients accounted for the majority of major amputations even though 53% of them remained alive and amputation-free at one year [12]. Our patients, who mostly presented in WIfI stages 3–4, exhibited comparable one-year limb preservation confirming that successful revascularization can modify the natural history of advanced ischemia predicted by WIfI staging.

Anatomical complexity and GLASS staging

The Global Limb Anatomic Staging System (GLASS) provided complementary anatomic stratification. In our study, GLASS III limbs showed more extensive disease and slightly less pronounced improvement in ischemia and wound than GLASS II. Nonetheless, they still demonstrated meaningful clinical benefit.  These findings replicate those of El Khoury et al. (2021) who reported that GLASS III anatomy was associated with markedly lower patency (42% vs 59%) and reduced major adverse limb-event–free survival (hazard ratio 2.35; P = .005) following revascularization [14].  Similarly, Murugavel et al. (2023) observed that both WIfI stage 4 and GLASS III independently predicted worse limb salvage with hazard ratios of 7.5 and 2.9, respectively.  However, they displayed moderate agreement (κ = 0.47) between the two staging systems [15].  Our results validate this interplay showing that clinical and anatomic burden act synergistically in determining outcomes, thus, emphasizing the necessity of integrating both frameworks during decision-making.

Benchmarks for limb salvage and survival

Reported one-year limb salvage rates after infrainguinal bypass vary between 70% and 90% depending on the following: conduit quality, distal runoff, and patient comorbidities.  Historical work by Illig et al. (2001) achieved 57% five-year limb salvage with combined bypass and free tissue transfer while Oh-Park et al. (2009) reported a median amputation-free survival of 1.3–3.3 years with socioeconomic factors influencing outcome [16, 17].  Our 12-month limb salvage rate of 95.7% compares favourably especially considering the predominance of advanced (WIfI 3–4, GLASS III) disease in our cohort and the resource-limited setting.

Suckow et al. (2013) analyzed 1227 below-knee bypasses and found 1-year major amputation rates of 13–17% with similar patency between prosthetic and vein conduits (72–73%) [18].  Our 4.3% major amputation rate reinforces the external validity of our findings and underscores the procedural reproducibility of vein bypass outcomes across regions.

Contrasting findings and regional considerations

While most Western series report limb salvage rates near or above 80%, the registry analyses from North America and Europe often involve larger centres with access to advanced wound care and surveillance programs [8, 9, 11]. In contrast, outcomes from middle-income or resource-limited environments may vary due to delayed presentation, infection prevalence, and limited access to endovascular alternatives. The consistent clinical improvement and acceptable amputation rate in our South Asian single-centre cohort thus highlight that surgical revascularization remains an effective and pragmatic option when performed by experienced vascular teams using autogenous vein conduits.

Interpretation and implications

Altogether, our findings reaffirm that below-knee autologous vein bypass grafting offers reliable revascularization for CLTI achieving both anatomic and physiological restoration. The early (≤ 6 months) improvement in WIfI domains underscores the critical period for wound surveillance and adjunctive care.  Integration of WIfI score and GLASS enables a multidimensional understanding of the clinical response, anatomic feasibility, and long-term prognosis, which is consistent with current Global Vascular Guidelines. These results support a tailored approach offering bypass to anatomically complex (GLASS III) limbs that remain clinically salvageable (WIfI ≤ 4).

The study’s retrospective design, modest sample size, and lack of a comparative endovascular cohort limit generalizability. Nevertheless, a standard surgical technique, scoring system, and consistent follow-up lend internal validity. In conclusion, below-knee bypass using autologous vein grafts yields significant improvement in WIfI components and total scores, and it achieves one-year limb salvage rates comparable to global benchmarks. Stratification by WIfI and GLASS stages refines prognostication, optimizes patient selection, and emphasizes the enduring role of surgical bypass in the contemporary management of CLTI.

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