Bone Allograft and Locking Plate for Severe Proximal Humeral Fractures: Early and Late Outcomes.

BACKGROUND Early failure of osteosyntheses is common even with use of locking plates. In patients with comminuted fractures and epiphyseal osseous defects, we performed a series of osteosyntheses by locking plate in combination with an allograft bone augmentation. Because of encouraging short-term results in the literature, we assumed that the method could be a potential alternative to a reverse shoulder prosthesis. MATERIAL AND METHODS Twenty-six patients with a dislocated proximal humeral fracture (Neer IV/V/VI) were studied. A lyophilized allogeneic bone graft was used to reinforce the humeral head fragments before locking plate osteosynthesis. The outcomes of fractures were assessed with Disabilities of the Arm, Shoulder and Hand (DASH) and Constant-Murley (Constant) scores, range of motion, a visual analog scale, and with radiological testing. The Constant-Murley scores were the endpoint of our study. RESULTS The Neer classification of the fractures was type IV in 4 patients, type V in 20 patients, and type VI in 2 patients. The mean DASH score was 52.85 (range, 4.17-79.3) and the mean Constant score was 39.26 (range, 17-88). We observed late necrosis of the humeral head in 15 of 24 patients (62.5%), although early radiological follow-up showed that the humeral head had been anatomically reconstructed. CONCLUSIONS Long-term follow-up demonstrated inferior functional results, as displayed by poor Constant scores. There was a high incidence of necrosis, in spite of initial anatomical reconstruction. Biointegration of the allogeneic bone graft and revascularization of the humeral head fragments could be impaired in geriatric patients who have gross dislocation. Therefore, augmentation of the humeral head with allogeneic bone grafts cannot be recommended in these patients.

Polytetrafluoroethylene (PTFE) suture vs fiberwire and polypropylene in flexor tendon repair.

BACKGROUND: In this study, we evaluate the value of novel suture material based on monofilamentous-extruded polyfluoroethylene (PTFE) compared to polypropylene (PPL) and Fiberwire (FW). MATERIALS AND METHODS: 60 flexor tendons were harvested from fresh cadaveric upper extremities. 4-0 sutures strands were used in the PPL, FW and PTFE group. Knotting properties and mechanical characteristics of the suture materials were evaluated. A 4-strand locked cruciate (Adelaide) or a 6-strand (M-Tang) suture technique was applied as core sutures for a tendon repair. Two-way ANOVA tests were performed with the Bonferroni correction. RESULTS: Stable knotting was achieved with 5 throws with the PPL material, 7 throws for FW and 9 throws for PTFE. In the PPL group, linear tensile strength was 45.92 ± 12.53 N, in the FW group 80.11 ± 18.34 N and in the PTFE group 76.16 ± 29.10 N. FW and PTFE are significantly stronger than PPL but show no significant difference among each other. Similar results were obtained in the subgroup comparisons for different repair techniques. The Adelaide and the M-Tang knotting technique showed no significant difference. CONCLUSION: Fiberwire showed superior handling and knotting properties in comparison to PTFE. However, PTFE allows easier approximation of the stumps. In both, M-Tang and Adelaide repairs, PTFE was equal to FW in terms of repair strength. Both PTFE and FW provide for a robust tendon repair so that early active motion regimens for rehabilitation can be applied.

Flexor tendon repair with a polytetrafluoroethylene (PTFE) suture material.

BACKGROUND: There is a consensus that after a flexor tendon repair an aggressive rehabilitation protocol with early active motion can improve functional outcome, provided that the combination of material and suturing technique can meet the higher biomechanic demands. Bearing this in mind we evaluated a polytetrafluoroethylene (PTFE) suture (SERAMON®, Serag-Wiessner) as a possible material for flexor tendon repair. MATERIALS AND METHODS: 40 flexor tendons were harvested from fresh cadaveric upper extremities. 3-0 and 5-0 strands were used both in the polypropylene (PPL) as well as in the PTFE group. In the first phase of the study, we evaluated knotting properties and mechanical characteristics of the suture materials themselves. In the second phase, a 2-strand Kirchmayr-Kessler suture technique was applied for a core suture of a flexor tendon (n = 16). In the third phase, we performed a tendon repair including an epitendinous running suture with 5-0 PPL or 5-0 PTFE material (n = 22). One way ANOVA tests were performed. RESULTS: The linear loading strength of single strand knotted PPL 3-0 was 19.87 ± 0.59 N. The linear loading strength of knotted PTFE 3-0 was 32.47 ± 1.67 N. For PPL 3-0 maximum linear strength was achieved with five knots, for PTFE 3-0 with eight knots. When a Kirchmayr-Kessler core-only repair was performed, then in the PPL group the loading strength of the repaired tendon was 30.74 ± 9.77 N. In the PTFE group the loading strength was 23.74 ± 5.6 N (p = 0.10). However, all repairs in the PTFE group failed due to cheese wiring. When a Kirchmayr-Kessler core and epitendinous repair technique was used, then in the PPL group the loading strength of the repaired tendon was 49.90 ± 16.05 N. In the PTFE group the loading strength was 73.41 ± 19.81 N (p = 0.006). CONCLUSION: PTFE demonstrates superior strength properties in comparison to PPL for flexor tendon repairs. However, standard 2 strand techniques have proved inadequate to bear the higher biomechanic demands.

Can systemically administered antibiotics be detected in wound tissues and surfaces under negative pressure wound therapy?

In this study, we evaluated a new aspect of negative pressure wound therapy (NPWT) as an analytical tool for pharmacokinetic studies. Twenty-one patients with soft tissue defects scheduled to receive NPWT were included in this study. Concomitant to NPWT, all patients received intravenous moxifloxacin (MX). At different time intervals, blood plasma levels of MX were sampled and compared with synchronous concentrations of MX in the exudate obtained from the NPWT drainage system. Serial measurements were performed upon initiation of the therapy as well as in the steady state (after 5 days). At steady state, wound tissue was obtained intraoperatively. High-performance liquid-chromatography (HPLC) was used for analysis. At 1 hour post-administration, the exudate/plasma levels (mg/L) were 1.92/3.07; at 12 hours, 0.80/1.14; at 24 hours, 0.26/0.43; and at 120 hours (steady state), 0.42/0.47. There was a correlation between exudate and plasma levels reaching approximately 0.75. Until now, methods for pharmacokinetic studies concerning interstitial fluid are difficult to apply in the clinical context. The presented method showed limitations, but we believe that, after methodological improvements, measurements of substances in the interstitial fluid by means of NPWT are feasible.

[The Value of Endoscopic Decompression in Surgical Therapy of Carpal Tunnel Syndrome]. / Stellenwert der endoskopischen Karpaltunneldekompression.

Carpal tunnel syndrome is one of the most common diseases in hand surgery. The gold standard in therapy is the surgical release of the carpal tunnel. We provide a brief update on the relevant pathogenesis, diagnosis and therapy and discuss questions related to minimal invasive decompression of the median nerve. Together with a review of the current literature, we report on our experiences in minimally invasive carpal tunnel release via a monoportal endoscopic access in over 700 cases. In conclusion, the endoscopic technique provides superior convalescence and patient safety is comparable to open methods. In addition, advantages and disadvantages of the various techniques are discussed.

Flow Induced Microvascular Network Formation of Therapeutic Relevant Arteriovenous (AV) Loop-Based Constructs in Response to Ionizing Radiation.

BACKGROUND The arteriovenous (AV) loop model enables axial vascularization to gain a functional microcirculatory system in tissue engineering constructs in vivo. These constructs might replace surgical flaps for the treatment of complex wounds in the future. Today, free flaps are often exposed to high-dose radiation after defect coverage, according to guideline-oriented treatment plans. Vascular response of AV loop-based constructs has not been evaluated after radiation, although it is of particular importance. It is further unclear whether the interposed venous AV loop graft is crucial for the induction of angiogenesis. MATERIAL AND METHODS We exposed the grafted vein to a single radiation dose of 2 Gy prior to loop construction to alter intrinsic and angio-inductive properties specifically within the graft. Vessel loops were embedded in a fibrin-filled chamber for 15 days and radiation-induced effects on flow-mediated vascularization were assessed by micro-CT and two-dimensional histological analysis. RESULTS Vessel amount was significantly impaired when an irradiated vein graft was used for AV loop construction. However, vessel growth and differentiation were still present. In contrast to vessel density, which was homogeneously diminished in constructs containing irradiated veins, vessel diameter was primarily decreased in the more peripheral regions. CONCLUSIONS Vascular luminal sprouts were significantly diminished in irradiated venous grafts, suggesting that the interposing vein constitutes a vital part of the AV loop model and is essential to initiate flow-mediate angiogenesis. These results add to the current understanding of AV loop-based neovascularization and suggest clinical implications for patients requiring combined AV loop-based tissue transfer and adjuvant radiotherapy.

A histopathologic and immunohistochemical study on liquification of human adipose tissue ex vivo.

BACKGROUND: This preliminary ex vivo study aimed to clarify the pathophysiologic mechanisms of fat tissue depletion by subcutaneous drug application. Therefore, the lipolytic effects of phosphatidylcholine plus deoxycholate (Lipostabil) (L) and of deoxycholate (DC) alone were compared with those of sodium chloride (NaCl) and hydrogen peroxide (H2O2) as control agents. The study enrolled 10 patients receiving abdominoplasty. The treatment periods for each sample and solution were 1, 3, 5, and 7 h. The samples were analyzed morphologically using hematoxylin-eosin (H&E) staining and also immunohistochemically using Caspase 3 and tumor necrosis factor (TNF)-alpha. Morphologic changes were seen best after 5 h of application time. Except for NaCl, all the samples in the H&E staining showed marked damage of adipocyte cell membranes, with the greatest disruption of normal cell architecture after hydrogen peroxide (H2O2) application. Immunohistochemistry using TNF-alpha showed positive results for the deoxycholate and Lipostabil samples and highly positive results for the H2O2 sample. Data from this study indicate that Lipostabil and deoxycholate induce pathways of cell necrosis involving TNF-alpha. These short-term experiments indicate that Lipostabil affects fat tissue in the way of a chemical-toxic destruction rather than via a physiologically induced, programmed cell death.

Tissue engineering and regenerative medicine -where do we stand?

Tissue Engineering (TE) in the context of Regenerative Medicine (RM) has been hailed for many years as one of the most important topics in medicine in the twenty-first century. While the first clinically relevant TE efforts were mainly concerned with the generation of bioengineered skin substitutes, subsequently TE applications have been continuously extended to a wide variety of tissues and organs. The advent of either embryonic or mesenchymal adult stem-cell technology has fostered many of the efforts to combine this promising tool with TE approaches and has merged the field into the term Regenerative Medicine. As a typical example in translational medicine, the discovery of a new type of cells called Telocytes that have been described in many organs and have been detected by electron microscopy opens another gate to RM. Besides cell-therapy strategies, the application of gene therapy combined with TE has been investigated to generate tissues and organs. The vascularization of constructs plays a crucial role besides the matrix and cell substitutes. Therefore, novel in vivo models of vascularization have evolved allowing axial vascularization with subsequent transplantation of constructs. This article is intended to give an overview over some of the most recent developments and possible applications in RM through the perspective of TE achievements and cellular research. The synthesis of TE with innovative methods of molecular biology and stem-cell technology appears to be very promising.

Individualized Wound Closure-Mechanical Properties of Suture Materials.

Wound closure is a key element of any procedure, especially aesthetic and reconstructive plastic surgery. Therefore, over the last decades, several devices have been developed in order to assist surgeons in achieving better results while saving valuable time. In this work, we give a concise review of the literature and present a biomechanical study of different suturing materials under mechanical load mimicking handling in the operating theatre. Nine different suture products, all of the same USP size (4-0), were subjected to a standardized crushing load by means of a needle holder. All materials were subjected to 0, 1, 3 and 5 crushing load cycles, respectively. The linear tensile strength was measured by means of a universal testing device. Attenuation of tensile strength was evaluated between materials and between crush cycles. In the pooled analysis, the linear tensile strength of the suture materials deteriorated significantly with every cycle (p < 0.0001). The suture materials displayed different initial tensile strengths (in descending order: polyglecaprone, polyglactin, polydioxanone, polyamid, polypropylene). In comparison, materials performed variably in terms of resistance to crush loading. The findings were statistically significant. The reconstructive surgeon has to be flexible and tailor wound closure techniques and materials to the individual patient, procedure and tissue demands; therefore, profound knowledge of the physical properties of the suture strands used is of paramount importance. The crushing load on suture materials during surgery can be detrimental for initial and long-term wound repair strength. As well as the standard wound closure methods (sutures, staples and adhesive strips), there are promising novel devices.

Polytetrafluoroethylene (PTFE) as a Suture Material in Tendon Surgery.

With the evolution of suture materials, there has been a change in paradigms in primary and secondary tendon repair. Improved mechanical properties allow more aggressive rehabilitation and earlier recovery. However, for the repair to hold against higher mechanical demands, more advanced suturing and knotting techniques must be assessed in combination with those materials. In this protocol, the use of polytetrafluoroethylene (PTFE) as a suture material in combination with different repair techniques was investigated. In the first part of the protocol, both linear tension strength and elongation of knotted against not-knotted strands of three different materials used in flexor tendon repair were evaluated. The three different materials are polypropylene (PPL), ultra-high molecular weight polyethylene with a braided jacket of polyester (UHMWPE), and polytetrafluoroethylene (PTFE). In the next part (ex vivo experiments with cadaveric flexor tendons), the behavior of PTFE using different suture techniques was assessed and compared with PPL and UHMWPE. This experiment is comprised of four steps: harvesting of the flexor tendons from fresh cadaveric hands, transection of the tendons in a standardized manner, tendon repair by four different techniques, mounting, and measurement of the tendon repairs on a standard linear dynamometer. The UHMWPE and PTFE showed comparable mechanical properties and were significantly superior to PPL in terms of linear traction strength. Repairs with four- and six-strand techniques proved stronger than two-strand techniques. Handling and knotting of PTFE are a challenge due to very low surface friction but fastening of the four- or six-strand repair is comparatively easy to achieve. Surgeons routinely use PTFE suture material in cardiovascular surgery and breast surgery. The PTFE strands are suitable for use in tendon surgery, providing a robust tendon repair so that early active motion regimens for rehabilitation can be applied.

Factors influencing successful outcome in the arteriovenous loop model: a retrospective study of 612 loop operations.

The arteriovenous (AV) loop is a complex model and requires advanced microsurgical skills. After several years of studies including characterization of the physiological and molecular phenomena behind the process of neovascularization, we would like to evaluate our experience from a microsurgical point of view. The AV loop operation was performed in 612 male Lewis rats. Species, surgeon, previous microsurgical skills, solid or soft consistency of matrix, weeks from implantation to explantation, experience, and practice of surgeon as well length of operation and outcome (patent versus thrombosed) upon evaluation were analyzed for each loop operation. Previous microsurgical skills, matrix, and explantation interval were not significant predictors. There was a significant correlation of experience, practice, and individual performance of microsurgical technicians with the rate of thrombosis and duration of the procedure. Experimental microsurgical operations on animals are best performed by especially trained technicians, rather than microsurgeons working parallel to their clinical activities. The AV loop is an excellent model in the arena of translational technologies, but due to its complexity is unsuitable for screening purposes. Experience and practice are both significant predictors of successful outcome. Possible applications of the model for research purposes are discussed.

Acute postoperative infection with Aeromonas hydrophila after using medical leeches for treatment of venous congestion.

INTRODUCTION: Venous convulsion after reconstructive microsurgery procedures is one major complication a surgeon has to deal with. Today, especially in the field of reconstructive microsurgery, medicinal leech therapy enjoys a renaissance. The potential risks such as infections associated with leech therapy are generally underestimated and not sufficiently discussed in literature. METHOD/PATIENTS: We present five male patients with an average age of 47 years. All patients suffered from a trauma incident, which had to be treated as an emergency. Three patients showed, postoperatively, a venous congestion after the reconstructive procedures. Another two patients with flap reconstruction and flap training developed venous problems after 12 and 14 days. In all five cases, the indication was given to use medical leeches (Hirudo medicinalis). In all the patients, a local infection of the injured extremity could be regarded after beginning with the leech treatment. The treatment duration with medical leeches for postoperative venous congestion was an average of 6 days. RESULTS: The reconstructive procedures in all five cases were unfortunately unsuccessful as major local infections were observed. Microbiological analyses showed, in all cases, an infection with Aeromonas hydrophila. CONCLUSION: We recommend making a considered indication for leech therapy, to diagnose wound infections early and to think about prophylactic antibiotics in patients with leech application.

Collagen matrices from sponge to nano: new perspectives for tissue engineering of skeletal muscle.

BACKGROUND: Tissue engineering of vascularised skeletal muscle is a promising method for the treatment of soft tissue defects in reconstructive surgery. In this study we explored the characteristics of novel collagen and fibrin matrices for skeletal muscle tissue engineering. We analyzed the characteristics of newly developed hybrid collagen-I-fibrin-gels and collagen nanofibers as well as collagen sponges and OPLA-scaffolds. Collagen-fibrin gels were also tested with genipin as stabilizing substitute for aprotinin. RESULTS: Whereas rapid lysis and contraction of pure collagen I- or fibrin-matrices have been great problems in the past, the latter could be overcome by combining both materials. Significant proliferation of cultivated myoblasts was detected in collagen-I-fibrin matrices and collagen nanofibers. Seeding cells on parallel orientated nanofibers resulted in strongly aligned myoblasts. In contrast, common collagen sponges and OPLA-scaffolds showed less cell proliferation and in collagen sponges an increased apoptosis rate was evident. The application of genipin caused deleterious effects on primary myoblasts. CONCLUSION: Collagen I-fibrin mixtures as well as collagen nanofibers yield good proliferation rates and myogenic differentiation of primary rat myoblasts in vitro In addition, parallel orientated nanofibers enable the generation of aligned cell layers and therefore represent the most promising step towards successful engineering of skeletal muscle tissue.

Tensiometry as a decision tool for abdominal wall reconstruction with component separation.

BACKGROUND: The recurrence rate for incisional hernias following reconstruction depends not only on the size of the initial hernia or abdominal wall defect but also on the number of the concomitant diseases. The surgical approach chosen and the level of tension affecting the sutures both represent essential indicators of long-term success in abdominal wall reconstruction. Several techniques have been advocated to reconstruct the abdominal wall, either with or without use of alloplastic material. A number of authors even recommended separating the lateral components of the abdominal wall to preserve innervation and blood supply of the advanced parts. METHODS: This retrospective study is based on a patient collective consisting of 23 patients. In addition to hernias or abdominal wall defects, all of them suffered several concomitant diseases and were treated at the German university hospitals in Erlangen-Nürnberg and Freiburg. All procedures were performed between the years 2000 and 2006. In all cases, reconstruction of the abdominal wall was achieved by employing the separation of components technique by Ramirez. Some of these procedures entailed the use of alloplastic material. Use of this material was based on intraoperative tensiometry results. Surgical outcome was determined by evaluating postoperative complications and the hernia recurrence rate. RESULTS: We achieved complete anatomic reconstruction of the abdominal wall in 61% of cases. Alloplastic mesh was used in 39% of the cases. Results of a long-term follow-up (56 months) revealed that only 18% of patients experienced hernia recurrence. CONCLUSIONS: Intraoperative tensiometry provides an additional important parameter for the surgical algorithm. Depending on the results, the appropriate surgical method for each case can be chosen. The decision on whether this procedure entails the use of alloplastic mesh can also be based on intraoperative tensiometry results.

Intrapulmonary and cutaneous siliconomas after silent silicone breast implant failure.

Since the implementation and use of silicone implants in breast surgery the risks are published and discussed. Especially, the incidence of late silicone implant rupture and its potential risk to induce local siliconomas are still under discussion and not sufficiently evaluated. So far literature data offer no information of intrapulmonal or peripheral located cutaneous siliconomas because of systemic migration of silicone after breast augmentation. In light of silicones checkered history, and given the large and growing number of women who choose to undergo breast augmentation surgery each year, the presented clinical findings in our study are likely to be of interest to medical professionals, producers, and consumers alike. We present six female patients with an average age of 55 (+/-5) years with bilateral rupture of silicone implants after breast augmentation for aesthetic reasons. The average time after operation was 18 (+/-6) years. In five patients, we identified peripheral located cutaneous siliconomas and one patient suffered from an intrapulmonal siliconoma. The diagnosis of bilateral rupture of the silicone implants was performed preoperatively by MRI-scans. All five peripheral cutaneous siliconomas and the intrapulmonal siliconoma were validated by histopathologic analysis. Six female patients suffered from bilateral rupture of silicone implants after breast augmentation. In five patients, we identified peripheral located cutaneous siliconomas which were surgically excised. One patient suffered from an intrapulmonal siliconoma. In this unique case a lobectomy with resection of the pulmonal segment 10 had to be performed. Clinical findings of peripheral cutaneous and even intrapulmonary siliconomas after bilateral rupture of silicone breast implants indicate a systemic hematogen or lymphatic pathway of silicone. These findings suggest that it is mandatory to inform the patient about the potential risk of local siliconomas, but also about the potential risk of peripheral cutaneous or even intrapulmonary siliconomas caused by systemic hematogen or lymphatic pathways of silicone after silent implant failure.

De novo generation of axially vascularized tissue in a large animal model.

De novo generation of axially vascularized tissue with clinically relevant dimensions in a large animal model and implementation of clinically established imaging modalities for in vivo evaluation of vascularization. To be used for reconstruction of tissue defects, engineered grafts need to be axially vascularized to enable transplantation without graft loss due to hypoxia. Limitations to dimensions in small animal models had not yet been overcome, which is necessary to yield clinical relevance. Anatomical studies of groin and axillary regions in eight merino sheep were followed by microsurgical creation of an arteriovenous loop (AV-loop), embedded in an isolation chamber filled with fibrin matrix. Constructs were implanted in the groin of six sheep for up to 6 weeks. Course of vascularization in de novo forming tissue was assessed by sequential computed tomography angiography (CTA) and magnetic resonance angiography (MRA) in vivo, as well as by postexplantational micro-computed tomography and histology. A vascular axis was constantly found epifascially at the medial aspect of all sheep's thighs, which was used for AV-loop creation. Patency of AV-loop could be visualized by CTA and MRA scans during 1-6 weeks. Complex 3D-vessel-reconstruction revealed increasing axial vascularization of the fibrin matrix and growing connective tissue within the isolation chamber, which was confirmed by micro-computed tomography and histology postexplantation. De novo formation of axially vascularized tissue was demonstrated for the first time ever in a large animal model, paving the way for the first application of tissue engineering vascularized grafts with clinically relevant dimensions.

Biomechanical and functional analysis of the pins and rubbers tractions system for treatment of proximal interphalangeal joint fracture dislocations.

INTRODUCTION: Dynamic external fixation systems are considered as optimal devices for treatment of fracture dislocations of the proximal interphalangeal joint (PiP). The pins and rubbers traction system (PRTS) is cheap, easy to assemble and comfortable and allows early mobilization of the affected digit. We investigated the influence of different wire positions and rubber strength and provided a follow-up of five consecutively treated patients. METHODS: Sixteen cadaver fingers (dig 2-5) were included into the biomechanical study. Forces for flexion of the PiP joint (30 degrees, 60 degrees, and 90 degrees) were measured by pulling the flexor digitorum profundus tendon; width of the PiP joint was assessed radiologically. Measurements were obtained prior and after assembly of PRTS and were repeated with three different types of rubbers and two different positions of the retention wire (distal and proximal). The clinical part of the study included five patients (21-72 years) who were treated using the PRTS. Mean follow-up was 272 days. RESULTS: The PRTS increased flexion force of the PiP joint. Proximal position of the retention wire increased forces for 30 degrees flexion. Different rubber strengths did neither increase PiP width nor influence flexion forces. In the clinical part of the study total range of motion was 74 degrees and DASH score was 10.1. Pinch grip of the affected digit was 72% of the unaffected side. DISCUSSION: The PRTS allows for efficient treatment of intraarticular fractures with PiP involvement. Although standardized positioning of the wires is important, proximal position of the retraction only increased forces for 30 degrees flexion.

Axial prevascularization of porous matrices using an arteriovenous loop promotes survival and differentiation of transplanted autologous osteoblasts.

Generation of axially vascularized bioartificial bone might be performed using matrix neovascularization in connection with osteoblast injection. We sought to evaluate whether prevascularization of porous hard matrices using an arteriovenous (AV) loop promotes survival of transplanted osteoblasts. A processed bovine cancellous bone matrix was inserted into the AV loop. Six weeks later, 5 x 10(6) carboxyfluorescein diacetate-stained osteoblasts were injected into the matrix (group A, n = 34). Osteoblast-seeded matrices without prevascularization were implanted subcutaneously as controls (group B, n = 32). Specimens were subjected to histologic, morphometric, and molecular-biological analysis after 1, 4, 8, and 16 weeks. Upon cell injection, matrices were completely vascularized. An intense foreign body reaction was observed in matrices from both groups. Group A was significantly superior to group B in terms of osteoblast survival at any time point. Expression of bone-specific genes was detected in the AV loop group but not in the subcutaneous control. Bone formation was only detectable in 1 long-term animal of group A. This study demonstrates for the first time that axial prevascularization increases the survival of implanted osteoblasts in porous matrices. Matrices with optimized biocompatibility might eventually facilitate generation of axially vascularized bone tissue after injection of osteogenic cells in the AV loop model.

Engineering of vascularized transplantable bone tissues: induction of axial vascularization in an osteoconductive matrix using an arteriovenous loop.

INTRODUCTION: Vascularization remains an obstacle to engineering of larger volume bone tissues. Our aim was to induce axial vascularization in a processed bovine cancellous bone (PBCB) matrix using an arteriovenous (AV) loop (artery, vein graft, and vein). METHODS: Custom-made PBCB discs (9 x 5 mm) were implanted into rats. In group A (n = 19), the matrices were inserted into microsurgically constructed AV loops between the femoral vessels using a vein graft from the contralateral side. In group B (n = 19), there was no vascular carrier. The matrices were encased in isolation chambers. After 2, 4, and 8 weeks, the animals were perfused with India ink via the abdominal aorta. Matrices were explanted and subjected to histological and morphometric analysis. Results were compared with intravital dynamic micro & magnetic resonance imaging and scanning electron microscopy images of vascular corrosion replicas. RESULTS: In group A, significant vascularization of the matrix had occurred by the 8th week. At this time, vascular remodeling with organization into vessels of different sizes was evident. Blood vessels originated from all 3 zones of the AV loop. Group A was significantly superior to group B in terms of vascular density and vascularization kinetics. DISCUSSION: This study demonstrates for the first time successful vascularization of solid porous matrices by means of an AV loop. Injection of osteogenic cells into axially prevascularized matrices may eventually create functional bioartificial bone tissues for reconstruction of large defects.