Soft tissue defects after-knee arthroplasty are a severe problem, which can even result in a loss of the prosthesis or the limb. Well-planned strategies are necessary for sufficient soft tissue reconstruction, resulting in optimal functional and aesthetic results.This report provides information on the classification of the tissue defects and the appropriate options for surgical reconstruction. Besides the basic therapy principles of immobilisation, debridement, planned lavages and antibiotic therapy, defect-dependent surgical techniques of reconstructive surgery are implemented. These include skin transplantation, local fasciocutaneous flaps, local pedicled muscle flaps and free flaps. For best results, interdisciplinary treatment by orthopaedic surgeons, plastic surgeons, microbiologists and physiotherapists is mandatory.

Weichteildefekte nach Knieendoprothetik stellen ein schwerwiegendes Problem dar, sodass sogar die Prothese oder das gesamte Bein gefährdet sein können. Sorgfältig geplante Strategien sind für eine suffiziente Defektdeckung notwendig, die ein möglichst optimales funktionelles und ästhetisches Ergebnis gewährleisten.

Background Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis. VEGF A also plays an important role in wound healing of the skin by promoting angiogenesis and by stimulating blood vessel growth. Therefore we tested the hypothesis that flap survival could be increased by the preoperative injection of AdVEGF(165).Methods We studied the effect of AdVEGF(165) in an overdimensioned ischemic random-pattem-flap model in the rat (n = 50) with a length-to-width ratio of 4: 1. VEGF cDNA was administered in two concentrations of 5 x 10(8) plaque-forming units (pfU) and 1 x 10(9) pfU using a recombinant adenoviral vector. Recombinant virus was injected subdermally 7, 3 or 0 days prior to flap harvest for the lower concentration and 7 days prior for the higher concentration. Flap survival and necrosis were observed at day 7, the day the animals were sacrificed.Results Adenoviral gene transfer with VEGF(165) 3 and 7 days before flap harvest showed a significantly increased flap survival of 50% together with a significantly reduced necrosis (p < 0.01). Injection using a titer of 1 x 10(9) pfU 7 days prior to surgery increased flap survival even more, though failing to reach statistical significance compared to the lower concentration. VEGF protein concentration in the injected skin was significantly higher than in controls (p < 0.01). Flap perfusion was increased as well, demonstrated by indocyanine green (ICG) fluoroscopy (p < 0.001).Conclusions Our results confirm the important role of VEGF(165) on angiogenesis in ischemic flaps. Indeed by injecting VEGF(165) at 3 to 7 days preoperatively in a concentration of 1 x 10(9) pfU our data show that length-to-width ratio for random-pattern-flaps could be increased from 2: 1 to 3: 1 and therefore may allow a wider range of applications of this simple flap technique. Copyright (c) 2004 John Wiley & Sons, Ltd.

A regular tissue functioning requires the adequate supply of oxygen and nutrient via blood vessels. The sequences of formation and maturation of vessels are initiated and maintained by different growth factors. The VEGF growth factor plays an exceptional role in these mechanisms. The creation of sublethal ischemia as an angiogenic stimulus known as "Delay" is a well established procedure in plastic surgery, although the underlying molecular biological mechanisms still remain unknown. The important role of VEGF and its regulation depending on oxygen pressure suggest a strong connection between this growth factor and the delay phenomenon. The VEGF concentration in skin and underlying muscle was measured in overdimensioned random pattern flaps on 32 male Sprague-Dawley rats after either VEGF gene therapy or circumcision without elevation of the flap and compared to controls. Additional random pattern flaps were raised seven days post gene therapy or delay. The effect on the flap perfusion was measured postoperatively using Indocyanine green Laser Fluoroscopy and the size of the surviving and necrotic areas of the flaps were analysed. The skin of the random pattern flaps showed both in the Delay group and in the VEGF gene therapy group a significantly elevated VEGF concentration compared to the controls. The underlying rectus abdominis muscle showed no significant differences in VEGF concentration between the groups. The flap perfusion postoperatively was significantly increased solely in the VEGF gene therapy group. The analysis of the surviving area of the flaps showed a significant increase over the controls in the gene therapy group. The Delay procedure results in a significantly and locally raised concentration of the VEGF growth factor. The gene therapeutical use of this growth factor allows us to raise flap perfusion and to reduce necrosis. Both VEGF gene therapy and Delay seem to promote similar mechanisms whereas the gene therapy produced superior results in this setting.

Eine normale Gewebefunktion ist auf die adäquate Sauerstoff- und Nährstoffversorgung durch Blutgefäße angewiesen. Die Abläufe der Bildung und Reifung von Gefäßen werden initiiert und aufrechterhalten durch unterschiedliche Wachstumsfaktoren. Dem Wachstumsfaktor VEGF kommt in diesen Prozessen eine herausragende Bedeutung zu. Die Erzeugung subletaler Ischämie als Angiogenesereiz ist unter dem Namen „Delay“ ein in der Plastischen Chirurgie etabliertes Verfahren, deren zugrunde liegende molekularbiologische Mechanismen jedoch weitgehend unbekannt sind. Ziel der vorliegenden Arbeit ist die weitere Aufklärung des Zusammenhangs zwischen VEGF und dem Delay-Phänomen, insbesondere im Vergleich zur adenoviralen Gentherapie als potenziell konkurrierendes, nicht-invasives Verfahren. An 32 männlichen Crl:CD(SD)-Ratten wurde die VEGF-Konzentration in Haut und Muskulatur nach subdermaler Injektion von AdCMV.VEGF165 oder reiner Umschneidung (Delay) einer überdimensionierten Lappenplastik vom „Random-pattern“-Typ gemessen und mit Kontrollen verglichen. Weiterhin wurden nach VEGF-Gentherapie oder Delay nach jeweils sieben Tagen die Lappenplastik gehoben und die Auswirkung der Therapie auf die postoperative Durchblutung mittels Indocyaningrün-Laser-Fluoreszenzangiographie und auf die Größe der überlebenden und nekrotischen Lappenfläche untersucht. Im Hautanteil der Lappenplastiken in der VEGF-Gentherapie-Gruppe und der Delay-Gruppe konnten jeweils gegenüber den Kontrollen signifikant erhöhte VEGF-Konzentrationen nachgewiesen werden. In der angrenzenden Muskulatur zeigten sich keine signifikanten Unterschiede zwischen den Gruppen. Bei der Messung der Perfusion unmittelbar postoperativ wies nur die VEGF-Gentherapie-Gruppe einen signifikant erhöhten Perfusionsindex gegenüber den Kontrollen auf. Die Messung der überlebten Lappenfläche ergab für die AdVEGF-Gruppe eine signifikante Erhöhung gegenüber der Kontroll- und der Delay-Gruppe. Das Delay-Verfahren resultiert in einer signifikant und lokalisiert erhöhten Konzentration des Wachstumsfaktors VEGF. Die gentherapeutische Verwendung dieses Wachstumsfaktors alleine ist in der Lage, die Hautdurchblutung zu steigern und die Entstehung von Nekrose zu reduzieren. Bei Gentherapie mit VEGF und Delay scheinen ähnliche Phänomene abzulaufen, wobei die Therapie mit AdVEGF eine deutliche Überlegenheit zeigt.

Prediction of necrosis has a clinical relevance in all fields of plastic surgery. The new application of indocyanine green (ICG) fluoroscopy in plastic surgery allows an objective quantification of skin perfusion and a high topographical resolution. The aim of the present study is to determine threshold values for flap perfusion under well-defined experimental conditions. Twenty random pattern flaps with a length to width ratio of 4:1 (8 x 2 cm(2)) were dissected on the anterior abdominal wall of 20 male Sprague-Dawley rats. ICG fluoroscopy was performed at the end of the operation. The animals were sacrificed at the seventh postoperative day with a reliable necrosis of the distal part of the flaps. Postoperative ICG fluoroscopy then was analysed both in regions that will survive and undergo necrosis. At day 7 a mean area of 5.5 cm(2) (57% of the total flap area) survived and a mean of 3.8 cm(2) (43%) became necrotic. The surviving part of the flap had a mean perfusion index of 62% compared to reference skin. The distal parts of the flap that necrotised showed an average perfusion index of only 19% postoperatively. Differences were statistically highly significant (p<0.001). Indocyanine green fluoroscopy is a useful tool to evaluate perfusion topographically and predict necrosis. From a statistical point of view a perfusion index of less than 25% of the reference skin can be considered as a sign of developing flap necrosis.

Prediction of necrosis in critically perfused skin flaps is difficult and rarely precise. An early detection of insufficiently perfused skin is highly desirable since it may lead to surgical decisions such as operative flap revision or early resection. The application of laser-induced indocyanine green (ICG) fluoroscopy allows an objective quantification of skin perfusion and a high topographical resolution. Aim of the present study is to determine a threshold value for flap perfusion under well-defined experimental conditions and test the validity of the results in the clinical application. Twenty overdimensioned random pattern flaps with a length to width ratio of 4 : 1 (8 x 2 cm) were dissected at the anterior abdominal wall of 20 male Sprague-Dawley rats weighing 365 g on average. ICG fluorescence was performed at the end of the operation by intravenous injection of 1 g ICG/kg bodyweight into a tail vein and digital recording. On the seventh postoperative day, both the necrotic and surviving areas of the flaps were measured and the ICG-fluorescence was analysed in the areas that had undergone necrosis. 41 flaps with areas of critical perfusion (18 skin flaps, 13 muscle flaps, 8 replantations) were analysed in 39 patients. The surviving part of the flap had a mean perfusion index of 62 % compared to reference skin. The distal parts of the flap that necrotized during the experiment showed an average perfusion index of 19 % postoperatively. Differences were statistically significant (p < 0.001). In clinical application, a number of 13 flaps were found to have a perfusion index less than 25 % in a region of critical perfusion. Eleven of these developed a partial necrosis in that region, one flap underwent total necrosis. Indocyanine green fluoroscopy allows a detailed topographical analysis of flap perfusion and the prediction of necrosis. Experimental findings presented a threshold value for the perfusion index of 25 % which could be confirmed in clinical application.

Background Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis. VEGF A also plays an important role in wound healing of the skin by promoting angiogenesis and by stimulating blood vessel growth. Therefore we tested the hypothesis that flap survival could be increased by the preoperative injection of AdVEGF 165 . Methods We studied the effect of AdVEGF 165 in an overdimensioned ischemic random‐pattern‐flap model in the rat (n = 50) with a length‐to‐width ratio of 4 : 1. VEGF cDNA was administered in two concentrations of 5 × 10 8 plaque‐forming units (pfU) and 1 × 10 9 pfU using a recombinant adenoviral vector. Recombinant virus was injected subdermally 7, 3 or 0 days prior to flap harvest for the lower concentration and 7 days prior for the higher concentration. Flap survival and necrosis were observed at day 7, the day the animals were sacrificed. Results Adenoviral gene transfer with VEGF 165 3 and 7 days before flap harvest showed a significantly increased flap survival of 50% together with a significantly reduced necrosis ( p < 0.01). Injection using a titer of 1 × 10 9 pfU 7 days prior to surgery increased flap survival even more, though failing to reach statistical significance compared to the lower concentration. VEGF protein concentration in the injected skin was significantly higher than in controls ( p < 0.01). Flap perfusion was increased as well, demonstrated by indocyanine green (ICG) fluoroscopy ( p < 0.001). Conclusions Our results confirm the important role of VEGF 165 on angiogenesis in ischemic flaps. Indeed by injecting VEGF 165 at 3 to 7 days preoperatively in a concentration of 1 × 10 9 pfU our data show that length‐to‐width ratio for random‐pattern‐flaps could be increased from 2 : 1 to 3 : 1 and therefore may allow a wider range of applications of this simple flap technique. Copyright © 2004 John Wiley & Sons, Ltd.

A regular tissue functioning requires the adequate supply of oxygen and nutrient via blood vessels. The sequences of formation and maturation of vessels are initiated and maintained by different growth factors. The VEGF growth factor plays an exceptional role in these mechanisms. The creation of sublethal ischemia as an angiogenic stimulus known as "Delay" is a well established procedure in plastic surgery, although the underlying molecular biological mechanisms still remain unknown. The important role of VEGF and its regulation depending on oxygen pressure suggest a strong connection between this growth factor and the delay phenomenon. The VEGF concentration in skin and underlying muscle was measured in overdimensioned random pattern flaps on 32 male Sprague-Dawley rats after either VEGF gene therapy or circumcision without elevation of the flap and compared to controls. Additional random pattern flaps were raised seven days post gene therapy or delay. The effect on the flap perfusion was measured postoperatively using Indocyanine green Laser Fluoroscopy and the size of the surviving and necrotic areas of the flaps were analysed. The skin of the random pattern flaps showed both in the Delay group and in the VEGF gene therapy group a significantly elevated VEGF concentration compared to the controls. The underlying rectus abdominis muscle showed no significant differences in VEGF concentration between the groups. The flap perfusion postoperatively was significantly increased solely in the VEGF gene therapy group. The analysis of the surviving area of the flaps showed a significant increase over the controls in the gene therapy group. The Delay procedure results in a significantly and locally raised concentration of the VEGF growth factor. The gene therapeutical use of this growth factor allows us to raise flap perfusion and to reduce necrosis. Both VEGF gene therapy and Delay seem to promote similar mechanisms whereas the gene therapy produced superior results in this setting.