[Minor amputations - a maxi task. Part 1: From the principles to transmetatarsal amputation]. / Minor-Amputationen - eine "Maxi-Aufgabe". Teil 1: Von den Grundlagen bis zur transmetatarsalen Amputation.

A threatening major amputation represents a fateful turning point for diabetics. This occurs in 50% of cases of amputations in diabetics. This increases the demand for another therapeutic route not only because of the limitations in quality of life but also due to substantially higher mortality. Even if an osteomyelitic ischemic situation is often present specialized centers have succeeded in substantially reducing the rate of major amputations in such patients. The term "minor amputation" commonly used in vascular surgery is not uniformly understood. Following the "vascular surgery working model" developed by Rümenapf, the significance of "minor amputations" for retention of extremities and the associated controversies have been shown. "Minor amputations" therefore represent a maxi-task if patients undergoing such a procedure are to be timely and competently treated. The necessary interdisciplinary cooperation with other specialists should in the future also include orthopedic surgeons.

[Minor amputations: a maxi task : Part 2: From transmetatarsal amputation to hindfoot amputation]. / Minor-Amputationen - eine "Maxi-Aufgabe" : Teil 2: Von der transmetatarsalen Amputation bis zur Rückfußamputation.

The definitive aim of a minor amputation is limited resection with retention of feet and legs resulting in a completely loadable extremity, in contrast to the lower leg stump. A shift in the amputation level in the sense of a shortening is inevitably accompanied by a reduction in the stand area, an increase in axial pressure and a disruption of muscle equilibrium in the extent of movement of the rest of the foot. This knowledge forms the central issue for further treatment of minor amputations in addition to the subtle treatment of the skin of the sole for coverage of a tension-free tip of the stump. Advantageous are longitudinal partial amputations of the forefoot and midfoot.

Classification of wounds at risk and their antimicrobial treatment with polihexanide: a practice-oriented expert recommendation.

Currently, there are no generally accepted definitions for wounds at risk of infection. In clinical practice, too many chronic wounds are regarded as being at risk of infection, and therefore many topical antimicrobials - in terms of frequency and duration of use - are applied to wounds. Based on expert discussion and current knowledge, a clinical assessment score was developed. The objective of this wounds at risk (W.A.R.) score is to allow decision-making on the indication for the use of antiseptics on the basis of polihexanide. The proposed clinical classification of W.A.R. shall facilitate the decision for wound antisepsis and allow an appropriate general treatment regimen with the focus on the prevention of wound infection. The W.A.R. score is based on a clinically oriented risk assessment using concrete patient circumstances. The indication for the use of antiseptics results from the addition of differently weighted risk causes, for which points are assigned. Antimicrobial treatment is justified in the case of 3 or more points.

A practice-oriented recommendation for treatment of critically colonised and locally infected wounds using polihexanide.

UNLABELLED: The problem of wound infection presents a special challenge in the treatment of acute as well as chronic wounds. Typical complications not only jeopardise the successful outcome of treatment modalities as a whole; they may result in amputation or even become life-threatening. Polihexanide is an antimicrobial substance which is highly appropriate for use in critically colonised or infected acute and chronic wounds. This finding is based primarily on the broad antimicrobial spectrum and good cell and tissue compatibility of polihexanide, its capability of binding to organic matrix, the low risk of contact sensitisation, and the fact that it promotes wound healing. Furthermore, there has been no conclusive evidence to date of any pathogens developing resistances under the use of polihexanide. SUMMARY: Wound infections are special and challenging situations in therapy of acute and chronic wounds. Typical complications are risky not only for therapeutic process but also for amputation and viability of patients. Polihexanide is an exceedingly appropriate antimicrobial substance for using in critical colonised and local infected acute and chronic wounds. This evaluation is based on different properties of the compound like the broad antimicrobial spectrum, the excellent cell and tissue tolerability, the binding capacity to organic matrix, low risk of contact sensitisation and adjuvant effects to wound healing. Up to now there are no microbial resistances observed.

Influence of the textile structure on the degradation of explanted aortic endoprostheses.

OBJECTIVES: To investigate mechanisms of textile failure in explanted human aortic endoprostheses. MATERIALS AND METHODS: Endoprostheses (n31) underwent optical and scanning electron microscopy, filament dynamometry, and saturation index measurement. RESULTS: The macroscopic lesions observed in the Stentor and Vanguard devices were holes at the extremities of the stents and slipping of the warp yarns at the level of sutures or of the longitudinal seams. The macroscopic lesions observed in AneurX endoprostheses were holes, slipping of the warp yarns and ruptures of the ligatures. The macroscopic lesions observed in the two Talent endoprostheses were sections of fibers at the level of the suture holes and few areas lesions of wear, with sometimes holes at the contact of the stent extremities. Stentor, Vanguard and AneurX all demonstrated low saturation indexes of the fabric (44-59%) with an important anisotropy. Whereas the Talent endograft demonstrated a high index of saturation (124-131%) with a low anisotropy. We did not demonstrate significant polymer degradation in any of the endoprostheses. CONCLUSIONS: It is essential to take into account the saturation index to optimally choose a woven textile for the construction of an endoprosthesis since this property of the textile may contribute to explain the macroscopic lesions observed. We did not observe significant polymer degradation by filament dynamometry but further studies are needed to confirm these data.

Mechanisms of rupture of knitted polyester vascular prostheses: an in vitro analysis of virgin prostheses.

OBJECTIVES: Previous explant retrieval studies have shown ruptures occurring on the remeshing line and the guide line of two types of warp-knitted grafts. The aim of our study was to characterize the mechanisms these ruptures. MATERIALS AND METHODS: We performed an in vitro study of the mechanical and chemical characteristics of virgin prostheses. We studied 2 virgin polyester warp-knitted grafts models: the Cooley Double Velour and the Microvel Double Velour constructed by Meadox (USA), using the following techniques: characterization and de-knitting of the textile structure, circumferential tensile strength, filament dynamometry, critical dissolution time of the filaments and scanning electron microscopy. RESULTS: Both prostheses were constructed in the same way but the texturized yarns of the Cooley graft included twice as many filaments (54) than the Microvel (27). There was more adsorbed tension in the Cooley structure than in the Microvel. The circumferential tensile strength test demonstrated that the Cooley graft always ruptured on the remeshing line and the Microvel graft always ruptured at the interface between the remeshing line and the standard line. Filament dynamometry demonstrated a heterogeneous behavior of the filaments inside the yarns, mainly at the remeshing line of the Cooley graft (27.1 cN/tex +/- 11.5% versus 26.1 cN/tex +/- 2.2% for the guide line and 28 cN/tex +/- 6.7% for the standard knit). Critical dissolution time of the filaments was significantly lower for the Microvel grafts (2.5 sec versus 17.2 sec for the Cooley). CONCLUSIONS: Rupture of knitted polyester prostheses are probably an underestimated phenomenon. They may occur at specific areas of the graft. Further studies are required to determine whether all grafts of this type are at risk.

What can we learn from explanted endovascular devices?

OBJECTIVE: To examine the durability of the Stentor and Vanguard endovascular devices in human implants. METHODS: The textile covering, the polypropylene ligatures and the stent metal of 34 devices (25 Stentor, 9 Vanguard) with a mean duration of implantation of 28.8 +/- 16 months was examined by means of stereomicroscopy and scanning electron microscopy. RESULTS: The polyester textile covering showed gaps along the sutured seam and isolated holes in the fabric. All of the examined polypropylene ligatures were worn, some ruptured. Four different types of stent corrosion were classified--pits (100%), bizarre craters (68%), large deficiencies (14%) and fractures (32%). CONCLUSION: Holes in the polyester fabric and frame dislocations are specific for the design of Stentor and Vanguard grafts. The early corrosion of the stent metal Nitinol in these devices is surprising. Until more experience is gained with other devices, we have to be reminded, that the "gold standard" for the long-term durability of artificial vascular grafts is still "today's" conventional graft.

[Injury of polyester grafts by vascular clamps]. / Schädigung von Polyestergefässprothesen durch Gefässklemmen.

UNLABELLED: Protected vascular clamps are not new. Clamp associated damage of human arteries has already been published over 20 years ago. The necessity of protective clamps seems to have been forgotten. In our explant archive (230 explants) we have observed an accumulation of graft ruptures in the groin (13 of 25 ruptures). We presume a multifactorial process. Clamp damage could be part of it. The aim of this study is to prove the clamp induced damage of polyester vascular grafts and to examine whether protected clamps can reduce this. METHOD: Five unprotected (Aesculap(R) FB512R, FB502, FB517, Ulrich CC1235, CV3535) and 5 protected vascular clamp types (Aesculap(R) FB667, FB668, Edwards(R) - formally Baxter(R) - Fogarty(R) CV5050, CV5201, Edwards(R) Cosgrove(R) CV1033) were tested. A longitudinal burst test was performed after maximal clamp closure on 6 different, multifilament polyester yarns of 2 different vascular grafts manufacturers (B. Braun(R), Edwards(R)). RESULTS: The yarn tests with protected clamps showed no difference to those of the unclamped yarns. After clamping with unprotected vascular clamps the stress-strain-diagrams differed significantly. The mean, maximum burst strength was up to 75 % lower. Video documentation revealed filament ruptures. Damage of the yarn surface was seen on a simple woven graft in scanning electron microscopy (SEM). DISCUSSION: The application of unprotected vascular clamps on polyester vascular grafts is common in Germany (56 %). The observed damage of multifilament polyester yarns makes it necessary to re-consider the use of unprotected vascular clamps. The benefit for biological vessels has already been shown.

Corroded nitinol wires in explanted aortic endografts: an important mechanism of failure?

PURPOSE: To analyze surface alterations and fractures observed in the nitinol stent wires of explanted endovascular grafts used for treatment of abdominal aortic aneurysm. METHODS: Twenty-one explanted Stentor devices and 1 Cragg stent were received from investigators in Germany and France. After macroscopy and photography, the explants were cleaned and the polyester coating removed. The frame was examined completely by stereomicroscopy, and irregularities were assayed by scanning electron microscopy and energy dispersive x-ray analysis (EDAX). The observed alterations were classified according to stereomicroscopic and electron microscopic morphology. RESULTS: The mean implantation interval for the endografts was 29.1 +/- 13.2 months (range 5-46). All examined explants, even those retrieved after only a few months in situ, showed pitlike surface damage 10-25 microm in diameter. Larger, irregularly shaped surface alterations were observed in approximately 70% of the explants. Older explants (age >32 months) presented vast regions of decay, with bending of the wire and stress cracks in some areas. EDAX examination revealed decreased nickel concentration in the corroded regions. CONCLUSIONS: Corrosion of the nitinol wire in endovascular grafts is confirmed. Presumably, the observed pitting and irregularly shaped corrosion defects are the precursors of material failure. They weaken the thin wire, which leads to stress cracks and eventually fracture of the stent wire under circulatory pulsation. Cell-induced electrochemical corrosion and active cellular destruction of surfaces are well-known mechanisms that must be investigated for their possible roles in the corrosion of stent metals.

Longitudinal ruptures of polyester knitted vascular prostheses.

AIM: The purpose of the study was the characterization of a type of rupture occurring on warp-knitted polyester vascular prostheses. MATERIALS AND METHODS: We studied 20 cases of warp-knitted polyester vascular prostheses that were explanted from humans that showed a longitudinal rupture as a part of a collaborative retrieval program. All the prostheses were immediately fixed in a 10% formaldehyde solution after their explantation in the operating room. The clinical data of these cases were recorded. The explants were photographed, washed to eliminate the surrounding tissues, and photographed again. The ruptures were characterized with macroscopic examination, optical stereomicroscopy, and scanning electron microscopy. RESULTS: The mean duration of implantation of the prostheses was 16.0 +/- 3.3 years (range, 9-20.7 years). The prostheses were Cooley Double Velour (n = 15) and Microvel Double Velour (n = 5). There were 16 aortobifemoral bypass grafts, 1 aorto-biiliac, 1 aorto-aortic, 1 iliofemoral, and 1 axillobifemoral. The longitudinal ruptures occurred on two specific parts of the prostheses: the guide line (6 cases) and the remeshing line (11 cases). In three cases both lines were affected. Scanning electron microscopy showed major degradation of the trilobar filaments of the velour and gradual ruptures of the flat filaments of the remeshing and guide lines. CONCLUSIONS: In this study, we have identified a specific mechanism of late (9-20 years) longitudinal rupture of knitted polyester prostheses consisting of degradation of the polyester filaments along the remeshing and guide lines that run the length of the graft.

Vascular tumors simulating occlusive disease.

Two cases of vascular tumors of large vessels with intraluminal growth simulating venous thrombosis and arterial occlusive disease are reported. One was a borderline malignant epithelioid hemangioendothelioma of the femoral vein and the other a malignant epithelioid angiosarcoma of the carotid artery. Immunohistochemical studies permitted to classify the tumors. Treatment consisted in surgical resection. No recurrence and no metastasis are noted at 24 months. Uncertainty regarding biological behaviour of vascular tumors and treatment persists.

[Late complications after alloplastic vascular replacement]. / Spätkomplikationen nach alloplastischem Gefässersatz.

The follow-up of 273 AAA patients operated 1981-1985 showed a mean dilation of polyester grafts of 17.4% in 12 days and 34.8% in 3 years. This early dilation is due to mesh expansion of the warp knitted grafts. It has no clinical relevance. In contrary the late dilation after approximately 10 years is due to degradation. The evaluation of 436 explanted grafts attained from 75 hospitals showed graft rupture to be the cause of the explanation for 42/255 (16%) polyester grafts and 2/42 (5%) PTFE grafts. The most ruptures were observed in the surrounding of the inguinal ligament after 10 to 20 years of duration. In comparison to modern endovascular grafts the conventional polyester and PTFE grafts still are the gold standard of durability.

[Stent wire fractures and mesh loosening in explanted endovascular prosthesis]. / Stentdrahtbrüche und Maschenlockerungen explantierter, endovaskulärer Prothesen.

UNLABELLED: Vascular grafts are available since the middle of the 50's. Explant retrieval studies still reveal not published material degradation today, after over 40 years of product development. Endovascular grafts exist since the beginning of the 90's. New developments and modifications have lead to numerous devices. The importance of explant retrieval studies grows. MATERIALS AND METHODS: Among 33 stentgrafts, retrieved 5 to 43 months after implantation, the majority were 18 MinTec devices (17 Stentor, 1 Cragg). These 18 explants were examined by endoscopy, stereomicroscopy and scanning electron microscopy. RESULTS: The following material degradation was observed. The textile coating showed holes along the longitudinal seam, the ligatures in-between the stentframes burst, allowing the frames to dislocate. Occasional fractures of the stent wire were seen accompanied by bowl-shaped alterations of the surface. CONCLUSION: The Stentor device is, since its modification 1996, not available any longer. It was one of the most applied devices world-wide. The possible material deficiencies must be known by those performing patient follow-up. The occurrence of alterations within 43 months shows the importance of a continued follow-up besides clinical trials.

Influence of crimping textile polyester vascular prostheses on the fluid flow kinetics. Groupe Européen de Recherche sur les Prothèses appliquées à la Chirurgie Vasculaire.

OBJECTIVES: to characterise the impact of the crimping of polyester prostheses on the fluid flow kinetics. DESIGN: an experimental in vitro study. MATERIALS AND METHODS: we investigated four models of polyester vascular prostheses in a continuous laminar flow circuit. The flow velocity was 80 ml/s for all experiments. We studied two fluids of different viscosity within the circuit. The speed of the particles was measured by a laser Doppler anemometer 2 to 52 mm from the prosthetic interface. We first established a calibrated flow-velocity profile corresponding to the study of the support inside the circuit without any prosthesis. We measured the velocity profiles for each prosthesis corresponding to four crimp densities obtained by stretching the grafts. RESULTS: the crimping of PET textile prostheses led to a decrease of flow velocity especially closer to the prosthetic surface. The decrease of flow velocity was dependent on the model of prosthesis. This decrease of flow velocity is described by the following negative exponential law: DeltaV=a times b(-x)where (a) is the crimp density and (b) the fluid viscosity. CONCLUSIONS: flow velocity near a prosthetic surface is influenced by the morphology of the crimping. The impact of crimping on the flow velocity in a vascular prosthesis can be predicted by computer simulation models. This may provide the optimal shape of crimping for each prosthesis.

The effect of autoclave resterilisation on polyester vascular grafts.

OBJECTIVES: polyester grafts are expensive, single-use items. Some manufacturers of uncoated, woven grafts include instructions for autoclave resterilisation to be performed at the surgeon's own request. Others warn against such manipulation. Theoretically, the glass transition point of polyester at 70-80 degrees C and the possible acceleration of hydrolysis suggest that autoclave resterilisation at 135 degrees C might be a problem. MATERIALS AND METHODS: a DeBakey Soft Woven Dacron Vascular Prosthesis (Bard) and a Woven Double Velour Dacron Graft (Meadox) were autoclave-resterilised 0 to 20 times, having been weighed before and after sterilisation. Tactile testing was performed. Mechanical properties were examined by probe puncture and single-filament testing, the surface was examined by scanning electron microscopy and the degree of hydrolysis by infra-red spectroscopy. RESULTS: tactile testing revealed a change of feeling with increasing cycles of resterilisation. Investigation of weight, textile strength, single-filament strength, electron microscopy of the surface and infra-red spectroscopy showed no change of the material. CONCLUSIONS: changes felt are presumably a surface phenomenon, not measurably affecting strength or chemistry of material after autoclave resterilisation. We therefore feel that it is safe to use once-autoclave-resterilised surplus uncoated polyester grafts, provided that sterility is guaranteed.

Aortobifemoral prosthetic infection treated by cryopreserved arterial homografts of the European Homograft Bank.

The excision of an infected aortobifemoral Dacron graft 9 years after implantation and bilateral axillofemoral Dacron bypass reconstruction led to reinfection of the extra-anatomic bypass grafts. A new aortobifemoral reconstruction was performed using cryopreserved homografts delivered by the European Homograft Bank in Brussels and both axillo-femoral prostheses were removed. No signs of infection and no alterations of the homografts can be detected 3 years later.

Frame dislocation of body middle rings in endovascular stent tube grafts.

OBJECTIVES: To understand the cause, and propose a mechanism for frame dislocation in endovascular grafts. MATERIALS AND METHODS: Five tube grafts were explanted due to secondary distal leakage 15-21 months after operation. One bifurcated graft was removed during emergency operation after aortic rupture caused by secondary leakage. A second bifurcated graft was harvested from a patient with thrombotic occlusion of one limb, who died after transurethral prostatic resection. The inside of the grafts were examined endoscopically. The stent was inspected after removal of the fabric, broken ligatures were counted and examined by scanning electron microscopy. The fabric strength was tested by probe puncture. RESULTS: We found 17-44% of the stent ligatures of the body middle rings to be loose. The knots were intact. Degradation of the polyester textile was not observed. CONCLUSIONS: Continuous movements in the grafted aorta and blood pressure impose permanent stress to the stent frame and the polyester fabric resulting in morphological changes in the body middle ring of grafts. The clinical implications of the suture breakages are unknown although they may be related to distal secondary leakage in tube grafts.

Rupture of an abdominal aortic aneurysm after endovascular graft placement and aneurysm size reduction.

Reduction in aneurysm size during the months after an endovascular graft placement generally is considered one of the criteria of success. We report the case of a patient with an abdominal aortic aneurysm rupture occurring 9 months after a bifurcated endovascular graft placement despite a greater than 45% reduction in size noted on contrast-enhanced computed tomography scan performed at 7 months. Biomaterial modifications of the stent and of the Dacron explanted stent-graft are analyzed.