25  The Obturator Foramen Bypass	259

graft occlusion, false aneurysm formation and anastomotic bleeding, and for planning the revascularisationprocedure.Incertaincasesofinguinalgraftinfection,contrastsinography may be appropriate to investigate the extent of infection. Finally, when vascular graft infection is suspected despite negative diagnostic tests, surgical exploration of the graft is necessary to detect the presence of perigraft fluid or to confirm whether the graft is incorporated in tissue. It is generally accepted that firm in-growth of surrounding tissue into the vascular prosthesis excludes the presence of graft infection. Although CT scanning and MRI can be very helpful in delineating the boundaries of infection preoperatively, the final judgement concerning the extent of infection is usually made intraoperatively. [Q2: A, C, D, E, F]

If only the distal part of the graft is infected, there are several therapeutic options in addition to antibiotics. [Q3: A, B, D] If the proximal part of the graft is also infected, then it should be removed entirely. If a revascularisation procedure is warranted, then an extraanatomic bior unilateral axillofemoral bypass may be established, preferably as a firststage procedure before the entire infected graft is removed.

In the majority of cases, for example if the graft is occluded and the limb is viable, no vascular reconstruction is required.5 In cases of limited infection, with no signs of anastomotic bleeding or septicaemia, then local treatment without graft resection may be attempted: wound debridement, irrigation, the use of gentamicincontaining collagen mats, and muscle transposition may be alternative ways of treating inguinal vascular graft infections.6 [Q4: A, B, C, D]

If only the distal part of an aortofemoral prosthesis has to be removed, and revascularisation is necessary, then OFB is a very good alternative. It is not a common operation and comprises less than 0.5% of all arterial reconstructions.7 Since Shaw and Baue8 introduced this procedure, published results of OFB rarely comprise more than 10–15 patients.7, 9–14 However, vascular surgeons should be familiar with its indications and technique when addressing challenging revascularisation problems in a hostile groin.

25.3 

The Concept of the Obturator Foramen Bypass

The rationale behind this operation is based on creating an arterial conduit from the aortoiliac segment to the superficial femoral, popliteal or deep femoral artery, depending on run-off conditions, while avoiding contaminated, infected or destroyed tissues in the groin. By routing the vascular graft through the obturator foramen, dorsally to the hip joint, in a layer between the adductor magnus and longus muscles, the area of the femoral triangle is circumvented. Autologous saphenous vein has been shown to give satisfying results, reducing the danger of secondary graft infection.15 However, since the saphenous vein may be too narrow and/or too short, in most cases an externally reinforced Dacron or PTFE graft is used, especially since these conduits offer greater resistance against compression and kinking. Under special circumstances, the obturator bypass can be performed as a cross-over ilioprofunda procedure using the contralateral iliac artery as the inflow site, the graft being routed through the prevesical space of Retzius.16

260	J.J. Jørgensen et al.

The main indication for this procedure (80% of cases) is infection confined to the distal iliac and inguinal part of an aortofemoral bypass graft.1 Other indications include the need for a revascularisation procedure in cases of infected femoral aneurysm, extensive local trauma,17 tissue scarring in the groin subsequent to radical tumour surgery, and/or therapeutic radiation or burns.18–20 Over the last years an increasing number of infected pseudoaneurysms in the groin among drug addicts are observed. In need of revascularisation OFB should be considered.21 Further, as the number of endovascular procedures with percutaneous femoral access has also risen over the last decades an increasing number of groin complications may be even more common in the future.14 The obturator bypass has also been used in rare cases for revascularisation of sciatic artery aneurysm exclusion.22 [Q5: A, E]

25.4 

Obturator Foramen Bypass Technique

The patient lies in the prone position, usually with the hip and knee joints slightly flexed, abducted and externally rotated. Some surgeons prefer to have the hip joint overextended a little to facilitate the tunnelling manoeuvre through the obturator foramen. The operation is usually performed under general anaesthesia, sometimes combined with epidural anesthesia to relieve postoperative pain. In all cases, a urinary catheter should be in place, since urinary bladder injury is a potential danger of this operation. [Q7]

If the indication for surgery is an infected prosthetic vascular graft in the groin, then it is an advantage to determine in advance whether a reconstruction is necessary. Thus, the sterile part of the operation, establishing a new vascular conduit, can be done first.1 The infected groin is sealed off with occlusive drape. Through a longitudinal paramedian incision or a curved, transverse lower abdominal incision, the proximal part of the graft is approached transperitoneally or retroperitoneally, respectively. Retroperitoneal access is a good alternative if one is certain that the infection is limited to the inguinal area. The involved graft limb is dissected proximally, close to the bifurcation. Firm incorporation of the graft in the surrounding tissue and a negative Gram stain of perigraft fluid indicate that the proximal part of the graft can be preserved.23 The graft limb is then transected, and the distal part is closed by sutures and pushed down towards the inguinal ligament. The overlying peritoneum is oversewn to separate the proximal graft from the infectious area. A ringed PTFE graft of diameter 6 or 8 mm is anastomosed in an end-to-end (Fig. 25.1) or end-to-side fashion to the proximal limb of the bifurcation graft. By careful blunt and sharp dissection, and with the aid of a large-blade self-retaining retractor, the ureter and bladder are identified. The pelvic organs are pushed gently towards the midline, rendering access to the obturator foramen. The sharp edge of the opening in the obturator fascia is usually identified easily by digital palpation on the anteromedial aspect of the foramen. This opening is dilated with long, slim grasping forceps with a blunt tip, taking care not to damagetheobturatorartery,veinandnervethatcurvearoundtheposterolateraledgeofthe foramen. Alternatively, other designs of blunt tunnellers can be used. It is therefore prudent to lead the forceps through the foramen bimanually, palpating where the tip of the forceps is to meet the fascial opening. We prefer tunnelling through the obturator foramen

25  The Obturator Foramen Bypass	261

Fig. 25.1  The principle of OFB (Reprinted from Kroese AJ and Rosen L1 © 1996, with permission from Elsevier)

from below, in a plane anteriorly to the adductor magnus muscle and posteriorly to the pectineus, adductor longus and brevis muscles. Some surgeons choose to do this manoeuvre from the retroperitoneal space downwards.11 The PTFE graft may be irrigated retrogradely with heparinised saline to ensure unrestricted flow.

Through an incision in the thigh, medial to the sartorius muscle, the femoropopliteal or profunda femoral artery is exposed for the distal anastomosis, which is usually performed in an end-to-side fashion. The profunda femoral artery is situated anteriorly to the adductor magnusandbrevismuscles,coveredpartiallybytheadductorlongusmuscle.Byretracting the superficial femoral vessels and the vastus medialis muscle laterally, a dense fascia between the adductor longus and the vastus medialis is exposed. This fascia is incised, therebyseveringtheattachmentoftheadductorlongustoexposetheprofundavessels.The overlying profunda vein is often divided and ligated to simplify the approach towards the profunda artery.24, 25 Rudich et al. report a case of postoperative thigh necrosis which may illustrate that ligation of the proximal popliteal artery above the distal anastomosis should be avoided in fear of insufficient collateral circulation.26

After closing the abdominal and thigh incisions, the patient is redraped and the infected groin is exposed. Swabs are taken for bacterial culture. Necessary debridement is performed,theinfectedanastomosisisexcised,andthefemoralarteryisclosedwitharunning monofilament suture. The infected graft is removed by withdrawing it under the inguinal ligament from the retroperitoneal space. Finally, the wound is irrigated lavishly before closing it over a suction catheter.

262	J.J. Jørgensen et al.

Perioperative complications occur in approximately 7% of cases.8, 12, 27 Bleeding from obturator vessels can be prevented by adhering to sound surgical principles.

Perforation of the urinary bladder, vagina or sigmoid colon by faulty tunnelling of the graft is a serious complication that may lead ultimately to loss of limb.28, 29

Since the obturator bypass is threatened by infection, long-term postoperative antibiotic treatment is advised. Although the duration is debatable, a period of 6–12 weeks can usually be agreed upon. Graft thrombosis may lead to severe ischaemic symptoms, and may even threaten the viability of the lower limb, since important collateral vessels in the inguinal region may have been sacrificed during the previous operation. Gluteus muscle necrosis may also compound this critical situation. Therefore, thrombectomy or thrombolysis of the thrombosed OFB graft should be attempted without delay. [Q7: F]

The obturator bypass in the management of infected vascular grafts seems to be a valuable procedure.12, 30 However, long-term results with this operation in terms of patency, limb salvage and survival rates are difficult to evaluate because the studies are usually small and include cases with different indications for obturator bypass. However, the majority of patients suffer from symptomatic peripheral arterial disease. In a review of the literature, perioperative mortality rates varied between zero and 14%. Survival rates after 1 and 5 years were 81% and 61%, respectively. Secondary patency rates for PTFE prostheses at 1 and 5 years were 71% and 52%, respectively. Short-term limb salvage rates up to 76–85%1 and a 5-year salvage rate of 55% could be achieved.12Patel et al. report a graft patencyof80%andlimbsalvagerateof60%at5years.14 Theresultsdependontheindication for operation and are better in patients without atherosclerosis. In patients with atherosclerosis, graft patency depends on factors such as run-off conditions and the progression of the underlying atherosclerosis.

There are several other options for revascularisation after the removal of an infected vascular graft in the groin, including semi-closed endarterectomy (ringstripping) or balloon angioplasty of the native iliac artery, axillofemoral bypass by lateral route avoiding the infected groin,31, 32 and subscrotal bypass.33 However, the OFB gives better results than bypassthroughthesealternativeextraanatomicalroutes.Ifthegroinisnotgrosslyinfected, then an autologous bypass of saphenous34 or femoral vein35 or thrombectomised femoral or iliac artery may be placed in situ without causing major problems, although the danger of future graft rupture is always present.36 In addition, in situ revascularisation with a rifam- picin-impregnated graft may give satisfactory results.37 [Q8: A, B, C, E, F]

Although the obturator bypass procedure is not used frequently, it should be a part of the vascular surgeon’s armamentarium. It may be effective in solving a difficult revascularisation problem in the groin, if performed appropriately.

References

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