Abstract: Two studies, involving a total of 147 participants with TransAtlantic Inter-Society Consensus (TASC)-II D femoropopliteal lesions, met our inclusion criteria and were included in the review. Both studies were small but otherwise of high methodological quality. However, the treatment techniques and control groups of the two studies differed, precluding the combining of study results and resulting in the evidence being less applicable. We therefore considered the quality of the evidence to be low. In one study, participants with TASC-II D lesions were randomized to receive either SIA with stenting of the superficial femoral artery or remote endarterectomy (RE) with stenting of the superficial femoral artery. Three-year follow-up results showed a Rutherford classification improvement of 64% in the SIA group compared to 80% in the RE group (risk ratio (RR) 0.79, 95% confidence interval (CI) 0.61 to 1.03; 95 participants; P = 0.079). Postexercise ankle brachial index improvements (defined as an increased value of 0.2) were reported in 70% of participants in the SIA group compared to 82% in the RE group (RR 0.86, 95% CI 0.68 to 1.08; 95 participants; P = 0.18). The study reported the technical success rate was 93% for the SIA group and 96% for the RE group (RR 0.97, 95% CI 0.88 to 1.07; 95 participants; P = 0.91). Primary patency at 12 months was 59.1% in the SIA group compared to 78.4% in the RE group (RR 0.75, 95% CI 0.57 to 1.00; 95 participants; P = 0.05). Primary patency at 24 months was 56.8% in the SIA group compared to 76.5% in the RE group (RR 0.74, 95% CI 0.55 to 1.00; 95 participants; P = 0.05) and 47.7% in the SIA group and 62.7% in the RE group at 36 months (RR 0.76, 95% CI 0.52 to 1.11; 95 participants; P = 0.15). Assisted primary patency was 52.3% in the SIA group compared to 70.6% in the RE group (P = 0.01) at 36 months. Secondary patency was better for the RE group (P = 0.03) at 36 months. Limb salvage at three years' follow-up was 95% in the SIA group and 98% in the RE group (RR 0.97, 95% CI 0.90 to 1.05; 95 participants; P = 0.4). There were no perioperative deaths, but complications occurred in two SIA participants (femoral pseudoaneurysm and pulmonary edema) and in three RE participants (seroma, femoral pseudoaneurysm, superficial femoral artery acute occlusion). In the second study, the effects of the SIA OUTBACK re-entry catheter device in people affected by TASC-II D superficial femoral artery chronic total occlusion were compared with the SIA manual re-entry technique. This study did not report clinical improvement and limb salvage. Technical success was achieved in all cases in both the OUTBACK device and manual groups. The primary 6-month patency rate was 100% in the OUTBACK group (26 of 26 participants) compared to 96.2% in the manual group (25 of 26 participants) (RR 1.04, 95% CI 0.94 to 1.15). The primary 12-month patency rate was 92.3% in the OUTBACK group (24 of 26 participants) compared to 84.6% in the manual group (22 of 26 participants) (RR 1.09, 95% CI 0.90 to 1.33). Patency rates at 24 and 36 months were not reported. The study reported that there were no complications. Using the GRADE approach, we classified the quality of the evidence presented by both studies in this review as low due to small study size and the small number of studies. In addition, the two included trials differed from each other in the techniques and control used, and we were therefore unable to combine the data. Consequently there is currently insufficient evidence to support SIA over other techniques. Evidence from more randomized controlled trials is needed to assess the role of SIA in people with chronic lower limb arterial total occlusions.

Plain-language summary: We identified two randomized controlled trials involving a total of 147 participants (current until January 2016). Due to differences in the techniques and outcomes measured, we were unable to combine the data from these studies. In one study, participants were randomized to receive either subintimal angioplasty (SIA) with stenting or remote endarterectomy (RE) (a surgical procedure to unblock the artery) with stenting. This study showed significantly better vessel patency (no obstruction) with RE compared to SIA. Three-year follow-up results showed clinical improvement measured by a Rutherford classification improvement in 64% of participants in the SIA group compared to 80% of participants in the RE group. Postexercise ankle brachial index improvements (0.2) were reported in 70% of SIA participants compared to 82% of RE participants. The technical success rate was 93% for SIA participants and 96% for RE participants. Primary patency was 56.8% in SIA compared to 76.5% in RE at 24 months, and 47.7% in SIA and 62.7% in RE at 36 months. Assisted primary patency was 52.3% in SIA compared to 70.6% in RE at 36 months. Secondary patency favored RE at 36 months. Limb salvage at three years' follow-up was 95% in the SIA group and 98% in the RE group. There were no deaths during or around the time of the procedure, but complications occurred in two SIA participants and three RE participants. The other study, which compared the SIA OUTBACK device with a manual re-entry technique, reported that technical success was achieved in all cases but did not report on clinical improvement. The primary 6-month patency rate was 100% in the OUTBACK group (26 of 26 participants) compared to 96.2% in the manual re-entry group (25 of 26 participants). The primary 12-month patency rate was 92.3% in the OUTBACK group (24 of 26 participants) compared to 84.6% in manual group (22 of 26 participants). Patency rates at 24 and 36 months were not reported. Limb salvage rates at 36 months were not reported. No complications were reported. Both studies were at an overall low risk of methodological bias, but the quality of the evidence is low due to small study size and the small number of studies. Moreover, the two included trials differed from each other in the techniques and control used, preventing the combining of trial results. Since we included only two small studies, we doubt the completeness and applicability of the evidence presented in this review. Further studies are needed to reach a definitive conclusion.