Beneficial effect of nerve growth factor-7S on peripheral nerve regeneration through inside-out vein grafts: an experimental study

This study investigated the effect of local administration of nerve growth factor-7S (NGF-7S) on the axonal regrowth of mixed peripheral nerves through inside-out vein grafts. Sixty male Wistar rats were randomized into two groups (n = 30). A defect 12 mm long in the right sciatic nerve was created and repaired with an inside-out vein graft from the right jugular vein. NGF-7S (group A) or phosphate-buffered saline (group B; control) was locally administered daily during the first 3 weeks. Walking-track analysis and electrophysiological and histological-morphometric studies were carried out 4, 6, 8, 10, and 12 weeks postoperatively (subgroups a, b, c, d, and e, respectively, n = 6 each). Data analysis showed that 1) the recovery of motor function, as measured by walk pattern analysis and evoked muscle action potential, and 2) the orientation, number, myelin thickness, and diameter of myelinated fibers were better in the NGF-7S than in the control group. These findings present strong evidence of the beneficial effect of NGF-7S on peripheral nerve regeneration through inside-out vein grafts.     

Interpostion vein graft in living donor liver transplantation

In adult-to-adult living donor liver transplantation (LDLT), right lobe grafts without a middle hepatic vein can cause hepatic congestion and disturbance of venous drainage. To solve this problem, various types of interposition vein graft have been used. OBJECTIVES: We used various types of interposition vein grafts for drainage of the paramedian portion of the right lobe in living donor liver transplantation. METHODS: From June 1996 to June 2003, 37 of 176 patients (128 adults, 48 pediatric) who underwent LDLT received vein grafts for drainage of segments V, VIII, or the inferior portion of the right lobe. RESULTS: In 36 adult cases the reconstruction included the inferior mesenteric vein of the donor (n = 14); cadaveric iliac vein stored at cold (4 degrees C) temperature (n = 5); cryopreserved (-180 degrees C) cadaveric iliac vein (n = 10); cryopreserved cadaveric iliac artery (n = 1 case); donor ovarian vein (n = 1); recipient umbilical vein (n = 3); recipient saphenous vein (n = 1); recipient left portal vein (n = 1); recipient left hepatic vein (n = 1). In a pediatric case with malignant hemangioendothelioma that encased and compressed the inferior vena cava, we used an interposition vein graft to replace the inferior vena cava. CONCLUSION: Various types of interposition vein grafts can be used in living donor liver transplantation. Cryopreserved cadaveric iliac vein and artery are useful to solve these drainage problems.     

The value of duplex surveillance after open and endovascular popliteal aneurysm repair

OBJECTIVE: The objective of this study was to determine the clinical value of vascular laboratory surveillance after open or endovascular repair of popliteal aneurysm by analysis of the frequency and nature of secondary interventions performed. METHODS: Over an 8-year period, 55 popliteal artery aneurysms were repaired in 46 men (mean age, 72 years) by aneurysm ligation and bypass grafting (vein, 37; prosthetic, 7), endoaneurysmorrhaphy and interposition grafting (prosthetic, 3; vein, 1), or endograft exclusion (n = 7). Indications for intervention included aneurysm thrombosis with critical limb ischemia (n = 8), symptomatic (n = 10) or asymptomatic (n = 37), >1.75 cm popliteal aneurysm with mural thrombus. Catheter-directed thrombolysis was used in three limbs to restore aneurysm and tibial artery patency before open repair. Duplex ultrasound surveillance was performed after repair to identify residual and acquired lesions. Life-table analysis was used to estimate repair site intervention-free (primary) and assisted-primary patency. RESULTS: During a mean 20-month follow-up interval, 20 secondary procedures were performed in 18 (31%) limbs to repair duplex-detected graft stenosis (n = 10), repair site thrombosis (n = 5), vein graft aneurysm (n = 3), graft entrapment (n = 1), or type 1 endoleak (n = 1). Primary patency was 76% and 68% at 1 and 3 years, and was uninfluenced by tibial artery runoff status or type of bypass conduit. Open (n = 12) or endovascular (n = 8) secondary procedures were performed on 15 (12 vein, 3 prosthetic) bypass grafts, 2 endografts, and 1 interposition graft. Mean time to repair graft stenosis (11 months) was shorter than to repair of vein graft aneurysm (37 months). Assisted-primary patency was 93% and 88% at 1 and 3 years; redo bypass grafting was required and successful in five limbs. Limb salvage was 100%. CONCLUSIONS: One third of popliteal artery aneurysms repaired by open or endovascular procedures required a secondary intervention within 2 years of repair. Repair-site surveillance using duplex ultrasound was able to identify lesions that threaten patency, which resulted in excellent assisted patency and limb preservation rates when corrected.     

Autogenous standard versus inside-out vein graft to repair facial nerve in rabbits

Objective： To evaluate autogenous vein grafts and inside-out vein grafts as conduits for the defects repair in the rabbit facial nerves. Methods： The 10 nun segments of buccal division of facial nerve were transected for 48 rabbits in this study. Then the gaps were immediately repaired by autogenous vein grafts or inside-out vein grafts in different groups. All the animals underwent the whisker movement test and electrophysiologic test during the following 16 weeks at different time points postoperatively. Subsequently, the histological examination was performed to observe the facial nerve regeneration morphologically. Results： At 8 weeks after operation, the facial nerve regeneration has significant difference between the experimental group and the control group in electrophysiologic test and histological observation. However, at the end of this study, 16 weeks after operation, there was no signifi- cant difference between inside-out vein grafts and standard vein grafts in enhancing peripheral nerve regeneration. Conclusion： This study suggest that both kinds of vein grafts play positive roles in facial nerve regeneration after being repaired immediately, but the autogenous inside-out vein grafts might accelerate and facilitate axonal regeneration as compared with control.     

Immunological unresponsiveness in chimeric miniature swine following MHC-mismatched spleen transplantation

BACKGROUND: In rodents, spleen allotransplantation (SpTx) induces tolerance. We investigated the induction of chimerism and donor-specific unresponsiveness following pig SpTx. METHODS: Thirteen pigs underwent splenectomy (day 0); all received a blood transfusion. In 11/13 pigs, SpTx was performed across a MHC class I (n=1) or full (n=10) barrier; two control pigs received no SpTx. All pigs were monitored for chimerism, and anti-donor immune responses, including suppressor assays. Four pigs (two asplenic controls and two with SpTx) underwent delayed donor-matched kidney transplantation without immunosuppression. RESULTS: Six of the 11 spleen grafts were lost from rejection (n=5) or splenic vein thrombosis (n=1), and five remained viable. All 11 SpTx recipients developed multilineage chimerism, but chimerism was rapidly lost if the graft failed. Two control pigs showed <6% blood chimerism for 4 and 11 days only. Pigs with functioning spleen grafts had multilineage chimerism in blood, thymus and bone marrow for at least 2-6 months, without graft-versus-host disease. These pigs developed in vitro donor-specific hyporesponsiveness and suppression. In 2 pigs tolerant to the spleen graft, donor MHC-matched kidney grafts survived for >4 and >7 months in the absence of exogenous immunosuppression; in two asplenic pigs, kidney grafts were rejected on days 4 and 15. CONCLUSIONS: Successful SpTx can result in hematopoietic cell engraftment and in vitro donor-specific unresponsiveness, enabling prolonged survival of subsequent donor-matched kidney grafts without immunosuppression.     

Optimizing infrainguinal arm vein bypass patency with duplex ultrasound surveillance and endovascular therapy

OBJECTIVE: Infrainguinal bypass grafting with arm vein is associated with lower patency rates compared with saphenous vein conduits. In this study the effect of a duplex ultrasound surveillance program to enable identification and treat graft lesions with open or endovascular repair on patency was analyzed. METHODS: Over 9 years 89 infrainguinal arm vein (26% spliced vein) bypasses were performed to treat critical lower limb ischemia in 89 patients without adequate saphenous vein conduits. Seventy-six (85%) of the bypasses were repeat procedures. Grafts were assessed at operation with duplex ultrasound scanning, then enrolled in a surveillance program. Graft stenoses with peak systolic velocity greater than 300 cm/s and velocity ratio greater than 3.5, detected at duplex ultrasound scanning, were repaired with percutaneous transluminal balloon angioplasty (PTA) if specific criteria were met, including greater than 3 months since primary procedure, lesion length less than 2 cm, and graft diameter greater than 3.5 mm, or with open surgical repair for early appearing or extensive graft lesions. RESULTS: During a mean 26-month follow-up, duplex surveillance resulted in a 48% (43 bypasses) intervention rate. Primary patency rate was 43% at 3 years. Twenty-six (43%) of 61 lesions identified and repaired met criteria for PTA; the remaining 35 graft lesions (stenosis, n = 30; vein graft aneurysm, n = 5) were surgically corrected with vein patch angioplasty (n = 15), interposition grafting (n = 13), jump graft bypass (n = 6), or open repair (n = 1). At 3 years the assisted primary patency rate was 91% (7 graft failures). Multiple interventions were performed in 18 (42%) revised grafts because of metachronous (n = 6) or repair site stenosis (n = 12). In 18 graft interventions (PTA, n = 9; surgery, n = 9) recurrent stenosis developed, and endovascular therapy was used in one third (n = 6). At 3 years the stenosis-free patency rate for PTA (48%) and surgically repaired (53%) graft lesions was similar. CONCLUSIONS: Arm veins used in lower limb bypass procedures are prone to development of stenosis and aneurysm, lesions easily detected with a life-long duplex ultrasound surveillance program. Excellent long-term patency (91%) was achieved despite graft intervention being performed in nearly half of all bypasses and one third of revised grafts. Endovascular treatment was possible in half of all graft stenosis, with outcomes similar to those with surgical repair.     

The natural history of intermediate and critical vein graft stenosis: recommendations for continued surveillance or repair

OBJECTIVE: Duplex ultrasound surveillance (DUS) after autogenous lower extremity bypass grafting is controversial. Specific criteria mandating graft revision are not uniform. It has been suggested that grafts harboring critical stenoses undergo revision, whereas those with intermediate stenoses undergo arteriography with selective repair. We sought to define the natural history and determine the risk of graft occlusion associated with unrepaired vein graft stenoses. METHODS: We analyzed serial vascular laboratory and clinical data of 156 autogenous infrainguinal vein grafts in 142 patients. Grafts were categorized into three groups according to the first DUS-detected (index) lesion: (1) normal (peak systolic velocity [PSV] < 200 cm/s, velocity ratio [V(r)] < 2); (2) intermediate stenosis (200 cm/s < PSV < 300 cm/s, 2 < V(r) < 4); and (3) critical (PSV > 300 cm/s, V(r) > 4). Our policy was to repair grafts with critical lesions and monitor all others. The risks of stenosis progression, graft revision, and graft thrombosis for each group were compared. RESULTS: Serial DUS was normal in 100 (64%) grafts. The incidence of graft thrombosis in the normal group was 3% per year (mean follow-up, 27.5 months). Intermediate lesions developed in 32 grafts (20%) and were followed. Among these 32 grafts with intermediate stenoses, 63% progressed to critical and were revised, and 32% resolved or stabilized (mean follow-up, 26 months). Only one graft occlusion occurred in grafts with intermediate lesions subjected to serial DUS monitoring (incidence 1.5% per year, P = not significant). In the third group, 16 of 25 grafts with critical lesions were successfully revised and remain patent. In nine cases, critical lesions were not repaired, resulting in seven (78%) occlusions, all within 4 months of DUS detection. CONCLUSIONS: Serial surveillance is safe and effective for grafts with intermediate stenoses. The graft occlusion rate for such grafts with careful monitoring is no different from grafts without stenosis, and therefore, arteriography is not indicated in the absence of progression to critical stenosis. The short-term risk of graft occlusion in the presence of an unrevised critical stenosis is nearly 80%. These data have important clinical implications concerning the natural history of vein graft lesions.     

A successful neurotization of two different muscles using a single intact motor nerve: experimental study on rats

The development of microsurgical techniques and better understanding of nerve biology has resulted in significant improvement in the results of nerve repair. Some problems are still present. What would be the method of choice if 2 transected nerves were to be coapted and only one neighboring intact nerve was available? We performed neurotization of 2 different muscles by a single intact nerve, using only one nerve graft by reverse end-to-side coaptation that has already been introduced into the literature. We assessed the results histomorphologically and functionally. Twenty-four adult rats were used in the present study and equally divided into 4 groups. Group 1 (n = 6): Control group; Group 2 (n = 6): Unrepaired nerve damage group; Group 3 (n = 6): End-to-end repair group. The peroneal branch of the sciatic nerve was excised to obtain an approximate size of 2 cm-graft, which was subsequently divided into 2 equal pieces to obtain 2 pieces of grafts each 1 cm long. Then, the tibial branch of the sciatic nerve was also cut to produce a nerve defect. End-to-end coaptation was obtained. A “V” shape was obtained. Group 4 (n = 6): Reverse end-to-side repair group. The peroneal branch of the sciatic nerve was excised as a graft approximately 2-cm in length. Subsequently a defect was produced by cutting the tibial branch of the sciatic nerve. Coaptation was performed by suturing the dissected proximal end of the tibial nerve by reverse end-to-side coaptation. A “U” shape resembling a horse shoe was obtained. The success of Group 4 was demonstrated when both peek-to-peek and latency timing of extensor digitorum and gastrocnemius muscles, determined as the target organ, were evaluated. Besides, an equal distribution was observed in Group 4 when number of myelinated (P = 0.596) and unmyelinated (P = 0.936) axons in both legs of grafts were compared with each other. However, myelinated axons were not equally distributed between the legs of the nerve graft in Group 3 (P = 0.027). In conclusion, reverse end-to-side coaptation is a useful technique for 2 different muscle neurotization via a single nerve graft and a single nerve coaptation with a donor nerve.     

Morphometric study of regeneration through vascularized nerve graft in a rabbit sciatic nerve model

Adequate vascularization is essential for a successful nerve graft. Theoretically, immediate vascularization will minimize fibroblast infiltration and support axonal regeneration. In this study, histomorphologic and morphometric studies were carried out to determine whether vascularized grafts are beneficial, in terms of axonal regeneration. In a rabbit model, 4-cm segments of sciatic nerve were obtained and placed as a nonvascularized graft on one side, and as a pedicled vascularized graft fed by the inferior gluteal vessel on the contralateral side. Histomorphologically, the distribution of myelinated nerve fibers and Schwann cells was evaluated after toluidine blue staining, at 2-, 3-, and 4-month intervals. The following results were obtained. 1) Myelinated nerve fibers were more abundant in the proximal, middle, and distal segments of the vascularized nerve group at 2 and 3 months. 2) The average nerve-fiber diameter was greater in the vascularized nerve graft group at 2, 3, and 4 months (2 to 10 microm). 3) Schwann cells were more abundant in the proximal, middle, and distal segments of the vascularized nerve graft group at all time points. Based on the above findings, the immediate restoration of circulation in the vascularized nerve graft can be accountable for the increased number of surviving Schwann cells, the rapid clearing of axons, and myelin-sheath changes that occur during Wallerian degeneration, thus enabling "morphologically" optimal regeneration.     

Prospective randomized multicenter comparison of in situ and reversed vein infrapopliteal bypasses

We have performed a prospective, randomized, multicenter study to compare in situ and reversed vein grafts for long limb salvage bypasses from the proximal thigh to an infrapopliteal artery. Three hundred eighty-four patients required an infrapopliteal bypass for critical lower extremity ischemia. Of these, 259 were excluded because a short vein bypass was performed or because the vein was considered inadequate. The remaining 125 patients had a randomized vein bypass, 63 reversed, 62 in situ. The two groups were similar with regard to risk factors, indications, graft dimensions, and outflow. Secondary patency at 30 months was similar for both techniques: reversed 67% +/- 9% (+/- SE); in situ 69% +/- 8%. For veins less than or equal to 3.0 mm in minimum distended diameter 24-month patency rates were 61% +/- 22% for 12 in situ veins and 37% +/- 29% for 10 reversed veins (p greater than 0.05). Angiographic evaluation of failing grafts revealed lesions similar in type and frequency in both types of grafts. These included focal (in situ, n = 4; reversed, n = 7) and diffuse vein hyperplasia (in situ, n = 2; reversed, n = 1), and inflow and outflow stenoses (in situ, n = 4; reversed, n = 3). The incidence of wound complications and the mortality rate were similar for the two groups. These data show no significant difference in overall patency rates for the two types of vein grafts at 2 1/2 years.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of vein graft use on postoperative 1-year results after off-pump coronary artery bypass surgery.

OBJECTIVE: We studied the postoperative 1-year results after off-pump coronary artery bypass surgery (OPCAB) with one or more saphenous vein grafts. METHODS: We compared the clinical and angiographic results of 833 patients who underwent OPCAB between 1998 and 2004. Group 1 patients (n=135) received one or more vein grafts. Group 2 patients (n=698) received total arterial grafts. Coronary angiographies were performed early postoperatively (n=804, 1.6+/-1.5 days), and 1 year postoperatively (n=671, 12.1+/-4.2 months). RESULTS: There were no significant differences in patient characteristics, operative mortalities, and morbidities between the two groups (p=ns). Both the early postoperative and 1-year angiographies demonstrated significantly lower overall graft patency rates in group 1 than in group 2 (early: 90.9% vs 99.1%, p<0.001; 1 year: 78.8% vs 95.1%, p<0.001), which might be affected by the lower vein graft patency rates in group 1 (early: 86.4%; 1 year: 67.9%). There was no difference in the 1-year patency of internal thoracic arteries between the two groups (94.3% vs 95.6%, p=0.402). Multivariate analysis demonstrated the use of vein graft (Odds ratio=5.204, p<0.001) as an independent predictor of graft failure during the first postoperative year. Target vessel revascularization rate during the postoperative 1 year was significantly higher in group 1 than in group 2 (7.4% vs 2.0%, p=0.002). CONCLUSIONS: Our study revealed that saphenous vein graft use in OPCAB independently predicted the graft failure while increasing the target vessel revascularization rate during the first postoperative year. Exclusive arterial revascularization would be a preferable strategy in OPCAB.     

The use of vein grafts in upper extremity nerve surgery

Vein grafts have been used to cope with several problems in peripheral nerve surgery, including vein wrapping of scarred nerves involved in chronic pain syndromes, vein caps for recurrent end-stump neuromas, vein conduits for nerve gaps after resection of neuromas-in-continuity, and following trauma. From 1993–1997, 30 vein grafts were performed in 28 patients. Five chronic peripheral nerve pain syndromes were treated by vein wrapping for two ulnar, two median and one radial sensory nerve, with significant pain resolution in all cases. Two recurrent digital neuromas were treated with vein caps, with pain resolution in each case. Nine patients with neuromas-in-continuity underwent neuroma resection and nerve repair with vein conduits. Twelve patients (14 nerves) underwent primary or delayed repair with vein conduits for nerve gaps following trauma. Sensory return measured by two point discrimination after repair of nerve gaps, following either neuroma-in-continuity resections or trauma, was 5–10 mm in 17 digital or common digital nerve injuries, and greater than 10 mm in three radial sensory nerve injuries. Received: 15 July 1998 / Accepted: 8 December 1998     

Monocyte adhesion to human vein grafts: a marker for occult intraoperative injury?

OBJECTIVE: Monocyte adhesion to the vessel wall is believed to be an important initiating event in atherosclerosis and intimal hyperplasia. We hypothesized that occult intraoperative vein injury induces an immediate increase in monocyte adhesion that may be critical to the development of vein graft disease. METHODS: Vein segments were obtained from patients (n = 23) undergoing lower extremity bypass. The initial segment (V1, n = 17) was excised immediately at the time of conduit harvest. A second segment (V2, n = 23) was obtained from the distal conduit just before performing the distal anastomosis. Segments were incubated with radiolabeled THP-1 cells (monocytoid cell line) for 1 hour at 37 degrees C, then rinsed and solubilized for determination of bound radioactivity. In a subset of grafts (n = 4), THP-1 cells were preincubated with monoclonal antibody (mAB) 7E3 (which binds to the monocyte integrin Mac-1 at its fibrinogen [Fg]-binding site) or control (mAB 14E11). Fg deposition and endothelial coverage were evaluated by immunohistochemistry (n = 10). Statistical analysis was performed using the paired t test and analysis of variance. Follow-up graft patency data were obtained and correlated with adhesion values using an exact test (StatXact, Cytel Software, Cambridge, Mass). RESULTS: Monocyte adhesion was significantly increased after surgical manipulation (V1, 2400 +/- 770 versus V2, 7343 +/- 1555 cells/cm(2); P <.02). Fg deposition was abundant in V2 sections and not seen in V1. Monocyte adhesion to V2 segments was significantly reduced (58% of control, P <.01) by 7E3 treatment. Graft follow-up was complete with a mean interval of 11 months. Higher V2 adhesion values were associated with occluded grafts (P =.07). The median value for the six occluded grafts was 6234 cells/cm(2) versus 3892 cells/cm(2) for the 17 patent grafts. CONCLUSIONS: Monocyte adhesion to the vein wall is immediately increased after surgical manipulation and is inhibited by mAB 7E3. Early monocyte adhesion to vein grafts is likely to involve interactions between Mac-1 and Fg. Heightened levels of monocyte adhesion at implantation may be a marker for subsequent vein graft failure.     

Effect of glucose toxicity on intraportal tilapia islet xenotransplantation in nude mice

BACKGROUND: Discordant xenogeneic islets transplanted intraportally into athymic nude rats experience primary non-function and are rapidly destroyed. Recently, it has been reported that adult porcine islets transplanted intraportally into nude mice are also rapidly destroyed and that this constitutes a new model for instant blood-mediated inflammatory reaction (IBMIR). METHODS: Tilapia (fish) islets were harvested, mechanically broken into mammalian islet-sized fragments, cultured for 48 h, and transplanted via the portal vein into athymic or euthymic mice. RESULTS: There were several groups of recipient mice. Streptozotocin-diabetic nude mice received 400 islets via the portal vein (n = 12). Recipients were killed when hyperglycemic (>200 mg/dl); livers and native pancreases were examined histologically. Mean graft survival time, based on function, was 5.4 +/- 1.2 days; at autopsy, histology showed occasional viable islets. We also performed a group of transplants in non-diabetic nude mice (n = 6) and then killed the recipients 2 or 4 weeks later; all had abundant viable, well-granulated islet grafts based on histology. Therefore, the intraportal environs in nude mice are not incompatible with discordant fish islets; rather, it appears as if hyperglycemia adversely affects the intraportal islet grafts (i.e. 'glucose toxicity'). To test this hypothesis, transplants were performed into non-diabetic nude mice and allowed to engraft for either 3 days (n = 6) or 10 days (n = 8) prior to injection of streptozotocin (200 to 220 mg/kg i.v.) to destroy the beta-cells in the recipients' native islets (n.b. tilapia islets are exceedingly resistant to streptozotocin); these recipients were followed for 28 days post-transplantation (or until hyperglycemic) and then killed for histology. Mean graft function exceeded 25 days for both groups and viable well-granulated, tilapia islets grafts were readily identified in all recipients; in all but one, the native pancreases were markedly beta-cell depleted -- confirming that normoglycemia was due to functional fish islet xenografts. CONCLUSIONS: Our results suggest that 'glucose toxicity' plays a role in the immediate demise of intraportal tilapia islet xenografts.     

Natural history of infrainguinal vein graft stenosis relative to bypass grafting technique

Purpose: To determine whether the incidence of vein graft stenosis is related to bypass grafting technique and thus modification of postoperative surveillance protocols may be required.Methods: From 1991 to 1996, 338 infrainguinal vein bypasses constructed using in situ (n = 131), reversed (n = 120), nonreversed translocated (n = 48), or spliced/upper extremity vein (n = 39) grafting techniques were evaluated by intraoperative duplex scanning to optimize bypass construction and serially thereafter to detect developing vein graft stenoses. Bypass procedures were performed in 322 patients for critical limb ischemia (83%), claudication (13%), or popliteal aneurysm (4%). Using life-table analysis, graft patency and revision/failure rates were compared relative to grafting technique, need for operative revision, and intraoperative duplex scan results.Results: Three-year primary and secondary graft patency rates were higher (p < 0.001) for in situ bypass grafts (85%/97%) compared with reversed (57%/83%), nonreversed translocated (62%/78%), or alternative (51%/76%) vein bypass grafts. During a mean follow-up interval of 19 months, the incidence of graft revision was higher for reversed saphenous (23%) and alternative (28%) vein bypass grafts compared with in situ (10%) or nonreversed (16%) saphenous vein bypass grafts. Despite a normal intraoperative graft duplex scan, the revision/failure rate of reversed vein grafts was 2.5 times greater than in situ/nonreversed translocated vein conduits (primary patency rate at 3 years, 60% vs 87%, p = 0.009). Bypass grafts modified at operation on the basis of duplex scanning were two times more likely to require postoperative revision than grafts with normal intraoperative scans.Conclusions: The incidence of postoperative graft stenosis and need for revision varies with bypass grafting technique. Reversed vein bypasses and grafts modified at operation may be more prone than in situ vein bypass grafts to develop stenosis and thus require intensive surveillance. Infrainguinal vein graft failure and the need for revision may be reduced by the adoption of bypass grafting techniques that include valve lysis and intraoperative duplex scan assessment. (J Vasc Surg 1997;25:211-25.)     

自体骨膜延迟游离移植修复成年后关节软骨缺损的实验研究

目的：研究年龄对自体骨膜游离移植修复关节软骨缺损的影响,探讨延迟游离移植能否提高成年后骨膜修复软骨能力。方法：选中国白兔,成年兔20只,幼兔10只,分3组。A组：成年兔左膝骨膜直接游离移植组;B组：成年兔右膝骨膜延迟游离移植组;C组：幼兔骨膜直接游离移植组,取骨膜或骨膜新生组织、行光镜、电镜组织学观察比较。结果：移植前B、C组骨膜厚度、细胞计数及细胞活跃程度均优于A组（均为P＜0．01）,移植后12周3组关节软骨缺损获得不同程度修复,C组优于A组（P＜0．01）及B组（P＜0．05）,B组优于A组（P＜0．01）。结论：自体骨膜局部剥离、原位激活,体内培养、延迟游离移植可提高成年骨膜成软骨能力,更好地修复成年后关节软骨缺损。     

Increasing incidence of midterm and long-term complications after endovascular graft repair of abdominal aortic aneurysms: a note of caution based on a 9-year experience

OBJECTIVE: To analyze the late complications after endovascular graft repair of elective abdominal aortic aneurysms (AAAs) at the authors' institution since November 1992. SUMMARY BACKGROUND DATA: Recently, the use of endovascular grafts for the treatment of AAAs has increased dramatically. However, there is little midterm or long-term proof of their efficacy. METHODS: During the past 9 years, 239 endovascular graft repairs were performed for nonruptured AAAs, many (86%) in high-risk patients or in those with complex anatomy. The grafts used were Montefiore (n = 97), Ancure/EVT (n = 14), Vanguard (n = 16), Talent (n = 47), Excluder (n = 20), AneuRx (n = 29), and Zenith (n = 16). All but the AneuRx and Ancure repairs were performed as part of a U.S. phase 1 or phase 2 clinical trial under a Food and Drug Administration investigational device exemption. Procedural outcomes and follow-up results were prospectively recorded. RESULTS: The major complication and death rates within 30 days of endovascular graft repair were 17.6% and 8.5%, respectively. The technical success rate with complete AAA exclusion was 88.7%. During follow-up to 75 months (mean +/- standard deviation, 15.7 +/- 6.3 months), 53 patients (22%) died of unrelated causes. Two AAAs treated with endovascular grafts ruptured and were surgically repaired, with one death. Other late complications included type 1 endoleak (n = 7), aortoduodenal fistula (n = 2), graft thrombosis/stenosis (n = 7), limb separation or fabric tear with a subsequent type 3 endoleak (n = 1), and a persistent type 2 endoleak (n = 13). Secondary intervention or surgery was required in 23 patients (10%). These included deployment of a second graft (n = 4), open AAA repair (n = 5), coil embolization (n = 6), extraanatomic bypass (n = 4), and stent placement (n = 3). CONCLUSION: With longer follow-up, complications occurred with increasing frequency. Although most could be managed with some form of endovascular reintervention, some complications resulted in a high death rate. Although endovascular graft repair is less invasive and sometimes effective in the long term, it is often not a definitive procedure. These findings mandate long-term surveillance and prospective studies to prove the effectiveness of endovascular graft repair.     

Acute and chronic open conversion after endovascular aortic aneurysm repair: a 14-year review

OBJECTIVE: This study reviewed outcomes of patients requiring surgical conversion after endovascular abdominal aortic aneurysm (AAA) repair. METHODS: Records for all patients undergoing open conversion after endovascular AAA repair were reviewed. RESULTS: From 1993 to 2006, 574 patients underwent endovascular repair for AAA. Seventeen patients, including three patients who underwent prior endovascular repair at other centers, required surgical conversion with complete (n = 9) or partial graft removal (n = 8). Five patients required immediate conversion (acute), and 12 underwent delayed conversion 4 to 72 months after endovascular repair. Indications for acute conversion were large type I endoleak (n = 3, 60%), including one patient with graft migration, and retroperitoneal bleeding (n = 2, 40%). Indications for chronic conversion were endoleak with increasing aneurysm size (n = 9, 75%), stent fracture without endoleak (n = 1, 8%), delayed retroperitoneal bleeding (n = 1, 8%), and infection (n = 1, 8%). Suprarenal aortic cross-clamping was required in two patients (12%), and endograft components were retained in eight (47%). An aortic occlusion balloon placed through the body of the existing endograft facilitated proximal control in three patients. There were two perioperative deaths in the acute conversion group (2/5; 40%) and none in the delayed conversion group (P = .04). Five-year actuarial survival was 71.9%. Mean follow-up was 41.6 +/- 32.2 months. Retained endovascular components in patients with partial graft removal remained stable during follow-up. CONCLUSIONS: Surgical conversion after endovascular AAA repair can be performed without suprarenal clamping in most patients. Endovascular aortic control with a balloon avoids suprarenal exposure. Partial endograft removal in selected patients facilitates open conversion and appears durable. Acute conversion is associated with increased mortality.     

End-to-end versus peripheral nerve graft repair of the oculomotor nerve in rats: A comparative histological and morphometric study

A comparative study was undertaken to evaluate end-to-end versus peripheral nerve graft repair in cranial nerve reconstruction. In 14 rats, the oculomotor nerve was sharply transected in the cavernous sinus and repaired either by end-to-end coaptation (n = 7) or by interposition of a peripheral nerve graft (n = 7). The results were evaluated 16 weeks after surgery by light and transmission electron microsurgery and by morphometric analysis. The degree of neuroma formation, fibrosis, and axonal disorganisation at the repair site was the same for both groups. Histologically, both end-to-end and graft repair groups revealed various degrees of axonal regeneration with myelinated nerve fibres in the distal nerve segments. In both groups, the number of nerve fibres distal to the repair site was increased compared to proximal to the repair (P < 0.001) but myelinated axon diameter was significantly less than that of control nerves (P < 0.001). No difference existed between the two repair groups in terms of mean myelinated axonal diameter. However, the number and density of myelinated axons was statistically greater in the graft group (P < 0.05). In conclusion, despite the disadvantage of two repair sites, peripheral nerve grafting results in equal or slightly superior axonal regeneration compared to an end-to-end repair in the rodent model of intracranial oculomotor nerve reconstruction. We speculate that this may be due to the structure of the peripheral nerve graft.     

Peripheral vascular reconstruction using deep vein graft for critically ill patients

The great saphenous veins are gaining wide popularity as acceptable native vascular grafts, but in terms of flow capacity, their small caliber may be unsuitable for immediate replacement of arterial flow. Ten peripheral vascular or central venous reconstructions were performed using superficial femoral vein free grafts for re-establishment of immediate high-flow patency. Seven of the patients were men with a mean age of 61.5 ± 17.9 years (range, 21-81 years). The majority of the patients were of preoperative or intraoperative critically ill statuses in that they had extensive infection (n = 5), bleeding (n = 4), renal failure (n = 3) or hepatic failure (n = 1). The mean preoperative physiology score of the vascular POSSUM was 24.1 ± 8.8 (range, 15-37), and the mean operative severity score was 18.4 ± 4.9 (range, 10-26). All patients survived and recovered from systemic infection or critical hemodynamic instability. During the mean 28.9 months of follow-up, complications such as aneurysmal dilation, recurrent infection, graft stenosis/occlusion, lower limb edema and other clinical problems that required attention were not observed. In conclusion, we determined that deep veins can be applied as ideal graft conduits for reconstructing the major peripheral vessels under complicated conditions in select patients.