Prelaminating the fascial radial forearm flap by using tissue-engineered mucosa: improvement of donor and recipient sites

Prelamination of the Radial Forearm Free Flap Using Free Full-Thickness Eyelid Skin Grafts: A New Approach for Intraoral Defect Reconstruction

ABSTRACT

Free flap transfer for reconstruction of intraoral defects is a common procedure in oral and maxillofacial surgery. For tumor-related defects, the radial forearm flap is widely used for soft tissue restoration. However, transfer of free skin grafts to the donor site region is often required for wound closure after free flap harvesting, resulting in esthetic disturbances due to shrinkage of the grafted skin, attendant scarring, or mismatches in skin texture or color. Furthermore, free flap transfer may result in hair follicle transfer into the oral cavity, causing unfavorable intraoral hair growth in adult men in particular. Free flap prelamination can help reduce the potential disadvantages of free flaps, in terms of both flap design and size and donor site morbidity. For surgical treatment of oral cancer in middle-aged and elderly patients, eyelid dermatochalasis may present as a comorbidity leading to esthetic impairments or, in cases involving the upper eyelid, even a reduced field of view. In these cases, bilateral blepharoplasty can reduce the excess eyelid skin. The present study is the first to attempt to use excised skin after bilateral blepharoplasty as full-thickness skin grafts for radial forearm free flap prelamination. This approach combined surgical therapy of eyelid dermatochalasis with free flap prelamination, thereby avoiding the need to harvest free skin grafts from other anatomically healthy regions to close the donor site defect and preventing the accompanying disadvantages. The reconstruction results and clinical outcomes of patients revealed that radial forearm free flap prelamination using bilateral free full-thickness eyelid skin grafts was an easy and feasible method for intraoral defect reconstruction. In particular, this approach could avoid intraoral hair growth and additional skin grafting from other healthy anatomical regions, yielding good esthetic and functional results at the flap's recipient and donor sites.

Prelaminated flaps in head and neck cancer reconstructive surgery: A systematic review

Background

Prelamination is a reconstructive technique providing fasciomucosal or composite flaps with low donor‐site morbidity. We conducted a systematic review of retrospective studies to assess the application of prelaminated flaps in reconstructive surgery of head and neck cancer patients, and to evaluate the advantages and disadvantages of this technique.

Methods

This systematic review adhered to the recommendations of the PRISMA (Preferred Reporting Items of Systematic Reviews and Meta‐analysis) 2009 guidelines. A computerized MEDLINE search was performed using the PubMed service of the U.S. National Library of Medicine (www.pubmed.org) and Scopus database (www.scopus.com), running the following search string: “prelamination OR prelaminated AND flap.” Two authors screened the articles, then selected and extracted data on malignancies characteristics, reconstructive techniques, outcomes and complications.

Results

A total of 19 articles were selected and reviewed from 128 identified. Seven of 19 articles were case reports, 12 articles were case series. One‐hundred‐two patients underwent reconstructive treatment by prelamination technique using a wide variety of flaps (92 free, 10 pedicled). The sites of reconstruction were oral cavity (66 floor of the mouth, 3 retromolar trigone, 6 hard palate, 4 cheek, 4 tongue), 8 facial skin (5 of them sited on the nose), 4 oropharyngeal defects, 1 laryngotracheal region. No case of total flap loss was reported. Partial flap loss or shrinkage requiring minor surgical revisions was observed in 18 patients (17.6%). Primary closure of the donor site was achieved in 97 cases (97%) and 3 (3%) required revision surgery of the donor site.

Conclusion

Prelamination is an effective and versatile technique, with low donor‐site morbidity. Further studies would be needed to investigate the impact on the patient's oncologic outcome. More comparative studies with standard reconstructive techniques are essential to understand when it is worth performing this sophisticated procedure.

Extended adipofascial wrap around radial forearm flap for hard palate reconstruction

Background

While using radial forearm free flap in palate reconstruction, the pedicle lies in the nasal floor, constantly exposed to the nasal secretions and turbulent air current. To overcome this problem, we have designed a procedure which utilises the adipofascial extension to wrap the pedicle and nasal side of the flap.

Materials and Methods

The study was done during 2017 and 2018, 2 years' period. Totally 13 consecutive patients with defect in the palate status post-oncological resection and those in whom local flaps were not enough to cover the defect were included into the study. These patients were divided into two groups. First group in whom adipofascial extension was not used to cover the pedicle and second group in whom adipofascial extension was used to cover the pedicle. The incidence of nasal crusting, secondary haemorrage, blow out and flap necrosis were analysed and compared.

Results

In Group 1, we had 2 among 6 (33%) patients with secondary haemorrage. One patient had partial flap loss. On exploring, we noticed thrombosis of cephalic vein. We did not had any incidence of blow out of the pedicle. In Group 2, none of the patients had any secondary haemorrage. All flaps healed well. On doing nasal endoscopy at 6 months of follow-up, all flaps showed complete mucosalisation at the nasal side.

Conclusion

Use of adipofascial extension while planning a radial forearm free flap to cover the nasal side of the flap and pedicle in the nasal floor helps to reduce the nasal crusting and secondary haemorrhage.

Aesthetic improvements of radial forearm flap donor site by autologous fat transplantation

Despite its reliability, radial forearm (RF) flap is still affected by high donor site morbidity with poor cosmetic and functional outcomes after coverage with skin grafts. Having fat grafting demonstrated promising and effective filling and rejuvenating properties, we considered and tested it as a valuable alternative to dermal substitutes for the aesthetic improvement of RF flap donor site. Thirty-three patients with previous RF free flap reconstruction and poor donor site outcomes after full-thickness skin grafting to RF region were evaluated for secondary fat injection to improve outcomes. Objective and subjective assessments of results with standardized ultrasonographic soft tissue thickness measurements, cutaneous sensibility tests with the pressure-specified sensory device and scar assessment scale (POSAS) have been performed. Bivariate statistical analyses were performed comparing outcomes with contralateral healthy forearm. All cases showed significant improvement in soft tissue thickness (p< 0.031), cutaneous sensibility and scar appearance, with improved patient's and observers' scar assessment scores (<0.001). In conclusion, fat transplantation is an effective procedure that provided us with an adjunctive autologous layer in-between skin graft and underlying fascia, as well as a rejuvenating effect on skin and scars.

Use of oral mucosal cell sheets for accelerated oral surgical wound healing

BACKGROUND

We developed a highly efficient in vitro-engineered mucosa equivalent using completely autologous mucosa and blood and investigated its feasibility and efficacy for oral surgical wound healing.

METHODS

Small oral mucosa samples were obtained from surgical patients, and keratinocytes and fibroblasts were primarily grown in media without animal products for generating 3D cell sheets.

RESULTS

Morphological characteristics of the cell sheets were comparable to those of human mucosa, although p63-positive cells were more numerous in cell sheets. In addition, cell sheets were flexible, expandable, and easy to handle or transfer. In further in vivo rat experiments with deep wounding of the buccal mucosa and soft tissues, controls had significantly thinner epithelium and thicker collagen densities than those with cell sheets.

CONCLUSION

Autologous cell sheets can be engineered in vitro from oral keratinocytes, fibroblasts, and fibrin, and can be used clinically to accelerate healing of oral soft tissue defects.

Soft Tissue Engineering

There is a recognized need to reconstruct and restore complex craniomaxillofacial soft tissues. The objective of this article is to focus on the role that tissue engineering/regenerative medicine can play in addressing various barriers (vascularity, tissue bulk, volitional control, and esthetics) and impediments (timing, regional applicability/dissemination, and regulation by the US Food and Drug Administration) to optimal tissue reconstruction of complex soft tissue structures. We will use the lips as an example to illustrate our points.

Radial Forearm Free Flap Donor Site Outcomes Comparison by Closure Methods

OBJECTIVE: To compare the functional and aesthetic outcomes of radial forearm free flap (RFFF) donor sites reconstructed with full-thickness skin graft (FTSG), split thickness skin graft (STSG) alone, and STSG overlying an acellular dermal matrix (AlloDerm).

STUDY DESIGN AND SETTING: A cross-sectional cohort study at a tertiary care hospital.

RESULTS: Twenty-five head and neck cancer patients who underwent reconstruction with RFFF completed the evaluations (STSG = 10, FTSG = 8, STSG with AlloDerm = 7). Subjective evaluations of postoperative function by questionnaires showed no significant differences among the 3 groups ( P = 0.93). In blinded evaluations by surgeons, the STSG group obtained the highest aesthetic outcome score (3.39 of 5.0), followed by FTSG (2.89) and STSG with AlloDerm (2.80). However, the difference was not statistically significant ( P = 0.32). Objective measurements of postoperative function by certified occupational therapists were comparable among the 3 groups with the exception of a mildly decreased range of wrist flexion ( P = 0.036) and ulnar deviation ( P = 0.016) in the FTSG group.

CONCLUSIONS: The 3 methods of reconstruction have comparable postoperative functional and aesthetic outcomes.

SIGNIFICANCE: Each of the 3 methods of reconstruction has low morbidity and satisfactory aesthetic and functional outcomes.

EBM rating: B-2b

Inducing re-epithelialization in skin wound through cultured oral mucosal keratinocytes

Objectives

The purpose of this study was to investigate the wound healing effect of primary cultured oral mucosal keratinocytes (OMKs) and to assess their roles in skin wounds.

Materials and Methods

OMK labeled with BromodeoxyUridine were scattered onto 1.5×1.5 cm skin defects of adult female nude mice (OMK group, n=15). For the control, culture media were placed on the wound (control group, n=15). Mice in both groups were sacrificed at three days (n=5), one week (n=5), and two weeks (n=5), and histomorphometric and immunoblot analyses with keratinocyte growth factor (KGF), interleukin (IL)-6, and IL-1α antibody were performed for the biopsied wound specimen. To verify the effect of the cytokine, rhIL-1α was applied instead of OMK transplantation, and the OMK and control groups were compared with regard to re-epithelialization.

Results

Histomorphometric analyses demonstrated faster re-epithelialization in the graft group than in the control group at the third day, first week, and second week. Newly forming epithelium showed maintenance of the histological character of the skin epithelium. The graft group showed superior expression of KGF, IL-6, and IL-1α protein, compared with the control group. Similar faster re-epithelialization was observed after treatment with rhIL-1α instead of OMK transplantation.

Conclusion

We successfully confirmed that the graft of primary cultured OMKs promoted regeneration of skin defects. The mechanism of accelerated wound healing by primary cultured OMKs was attributed to inducement of cytokine expression as required for re-epithelialization.

Fibula osteo-adipofascial flap for mandibular and maxillary reconstruction

BACKGROUND

The fibula free flap is a reliable method for reconstructing composite head and neck defects. However, its skin paddle has drawbacks, including its thickness, hair-bearing surface, desquamation, difficulty insetting it into maxillary defects, and the potential need for skin-grafting the donor site. The fibula osteo-adipofascial flap (FOAFF) is a modification of the fibula flap that overcomes these problems.

METHODS

A retrospective study of 6 consecutive patients who underwent FOAFF reconstruction was evaluated for outcomes and complications.

RESULTS

The mean follow-up was 22.6 months. All flaps survived, with complete oral mucosalization by 7 weeks. Four patients had dental implants placed at the time of reconstruction. Two patients received radiation therapy. Aside from loss of the labial sulcus in anterior maxillary reconstructions, complications were negligible.

CONCLUSION

The FOAFF is useful for reconstructing defects requiring bone, soft tissue, and mucosal replacement without the disadvantages of the traditional fibula skin paddle.

Squamous cell carcinoma arising in a skin flap: case report and review on malignant transformations in skin grafts and microvascular cutaneous flaps

OBJECTIVES

Sufficient closure of intraoral defects can be challenging. Various methods of tissue transfer have been presented in the literature. From skin grafts to microvascular flaps, most techniques used for intraoral reconstruction use skin to line out the oral cavity to guarantee an epithelial surface. Native mucosa tolerates the moist environment of the oral cavity, whereas skin flaps do to just a certain extent. This may lead to chronic inflammation of the flap-skin. Under rare circumstances, these histologic changes can enhance the risk for malignant transformation of the skin graft.

CASE REPORT

We present a case of a patient who derived a squamous cell carcinoma in the skin island of a jump flap raised from the abdominal wall 30 years earlier. The flap was used to close a very wide palatal cleft. The patient had no history of malignancy, smoking, drinking, or other risk factors.

DISCUSSION

To the authors' knowledge, this is the first report on carcinoma in a skin flap in a patient without any history of intraoral malignancy. Although malignant transformations of skin grafts are very rare and usually appear years after the reconstruction, one should be aware that the moist environment can lead to chronic inflammation of the dermis of flap. This fact may increase the risk of malignant transformation in a skin graft.

Tissue engineering of composite grafts: Cocultivation of human oral keratinocytes and human osteoblast-like cells on laminin-coated polycarbonate membranes and equine collagen membranes under different culture conditions

In complex craniomaxillofacial defects, the simultaneous reconstruction of hard and soft tissue is often necessary. Until now, oral keratinocytes and osteoblast-like cells have not been cocultivated on the same carrier. For the first time, the cocultivation of human oral keratinocytes and human osteoblast-like cells has been investigated in this study. Different carriers (laminin-coated polycarbonate and equine collagen membranes) and various culture conditions were examined. Human oral keratinocytes and human osteoblast-like cells from five patients were isolated from tissue samples, seeded on the opposite sides of the carriers and cultivated for 1 and 2 weeks under static conditions in an incubator and in a perfusion chamber. Proliferation and morphology of the cells were analyzed by EZ4U-tests, light microscopy, and scanning electron microscopy. Cocultivation of both cell-types seeded on one carrier was possible. Quantitative and qualitative growth was significantly better on collagen membranes when compared with laminin-coated polycarbonate membranes independent of the culture conditions. Using perfusion culture in comparison to static culture, the increase of cell proliferation after 2 weeks of cultivation when compared with the proliferation after 1 week was significantly lower, independent of the carriers used. In conclusion, the contemporaneous cultivation of human oral keratinocytes and human osteoblast-like cells on the same carrier is possible, a prerequisite for planned in vivo studies. As carrier collagen is superior to laminin-coated polycarbonate membranes. Regarding the development over time, the increase of proliferation rate is lower in perfusion culture. Examinations of cellular differentiation over time under various culture conditions will be subject of further investigations.

In vitro engineering of complete autologous oral mucosa equivalents: characterization of a novel scaffold

BACKGROUND AND OBJECTIVE

Restoration of oral mucosa defects by means of in vitro-cultured equivalents has become a valid alternative in the field of oral and periodontics surgery. Although different techniques have been described, none has been able to provide an equivalent with an autologous scaffold for the epithelium. The purpose of this study was to obtain complete autologous oral mucosa equivalents (CAOME) using the patient's own fibroblasts and plasma and to characterize these equivalents both morphologically and immunohistochemically.

MATERIAL AND METHODS

We acquired cell types (keratinocytes and fibroblasts) from the same mucosal samples, which were taken from healthy patients who underwent oral surgery. To construct the CAOME, a small sample of blood was obtained from the patient and subsequently processed to obtain a fibrin glue scaffold. All CAOME thus obtained were stained using the standard hematoxylin and eosin method to study their morphological characteristics. To establish the type of cells in the epithelial layer, CAOME were stained with pancytokeratin AE1/AE3, cytokeratins 5/6 and 13, p-63 and Ki-67. Finally, laminin 5 and collagen IV were used to reveal the presence of a basal membrane.

RESULTS

The CAOME featured a monolayer of cube-shaped epithelial cells similar to that found on the basal layer of the oral mucosa. Close to the epithelial layer lay the fibrin and fibroblasts-embedded scaffold. The CAOME was positive to pancytokeratin AE1/AE3, cytokeratin 5/6 and p-63. No reaction was found to cytokeratin 13 and Ki-67. There was staining to laminin 5 but not to collagen IV.

CONCLUSIONS

It is possible to engineer a CAOME with an epithelium of basal-like and immature keratinocytes, which could potentially reconstruct in vivo loss of tissue.

Prefabricated bony radial forearm flap for secondary mandible reconstruction after radiochemotherapy

BACKGROUND

Primary reconstruction of the mandible is the golden standard of surgical treatment after ablative tumor surgery. Many different microvascular bone grafts are used to reduce wound healing complications at the severely compromised recipient site. The loss of primary grafts due to radiotherapy or osteoradionecrosis can make secondary mandibular reconstruction necessary. To address this problem, we developed the technique of the prefabrication of a radial forearm flap with cancellous bone. The aims were to establish these techniques into the clinical routine and to create a safe and reliable flap with low donor site morbidity.

METHODS

In patients who had undergone ablative tumor surgery radiochemotherapy, and primary reconstruction, prefabricated bony radial forearm flaps (PBRFFs) were applied for secondary reconstruction of the mandible. Cylinders of cancellous bone taken from the iliac crest were implanted in the lower forearm to allow the necessary vascularization. After a healing period of 4 weeks, the PBRFF was elevated and grafted into the mandibular defect.

RESULTS

All grafts healed uneventfully. However, 1 case required revision of the venous anastomosis after 2 days. The transplants improved the contour of the lower face enabling a good correction of the facial asymmetry. During the follow-up of up to 4 years, the radiographic controls showed good bony consolidation between the graft and the stumps of the mandible as well as formation of cortical bone around the cancellous bone cylinders.

CONCLUSION

These results demonstrate that the PBRFF is a safe and reliable graft which provides alternate solution in which other microvascular bone grafts have already failed. In the future, the iliac bone graft may be replaced with scaffold seeded with stem cells for further reduction of donor site morbidity.

Free radial forearm adiposo-fascial flap for inferior maxillectomy defect reconstruction

A free radial forearm fascial flap has been described for intraoral reconstruction. Adiposo-fascial flap harvesting involves few technical modifications from the conventional radial forearm fascio-cutaneous free flap harvesting. We report a case of inferior maxillectomy defect reconstruction in a 42-year-old male with a free radial forearm adiposo-fascial flap with good aesthetic and functional outcome with minimal primary and donor site morbidity. The technique of raising the flap and closing the donor site needs to be meticulous in order to achieve good cosmetic and functional outcome.

Review of the radial free flap: is it still evolving, or is it facing extinction? Part one: soft-tissue radial flap

The versatile fasciocutaneous radial flap is robust and reliable, straightforward to harvest, and often produces a satisfactory reconstruction with relatively little long-term morbidity at the donor site. Many surgeons prefer to use a limited number of trusted flaps, and these qualities will ensure that in the intermediate future most surgical trainees will continue to be shown the fasciocutaneous radial flap as both the basic training flap and the established option for reconstruction. Evidence from observational clinical studies and one randomised clinical trial indicates that there is increasing support for the use of the evolutionary technique of suprafascial dissection to minimise morbidity at the donor site. The suprafascial donor site may be repaired with either a meshed or unmeshed partial-thickness skin graft, or a fenestrated full-thickness skin graft, with good rates of successful healing. The application of a negative pressure dressing to the wound seems to facilitate the healing of all types of skin graft. The subfascial donor site, however, remains more prone to complications. It may be helpful to position the donor site of the flap more proximally, but this has not been proven. These refinements probably produce the best outcomes that can currently be achieved, given the inherent flaws of the radial donor site.

An algorithm for treatment of nasal defects

Nasal defects are common after cancer resection, and the goal of treatment is to appropriately define the defect and then to select the best reconstructive options. The plastic surgeon must reestablish all deficient layers of the nose (support, lining, and external cover). The authors' algorithm is based on defect location and orientation, with the nose divided transversely into three zones, and then into subunits. In this article, using the aforementioned algorithm, the authors simplify the complex topic of nasal reconstruction, concentrating on local and regional flap reconstruction. The appropriate treatment for full-thickness defects, including options for reconstruction of lining and support, is also discussed.

Comparison of autologous full-thickness gingiva and skin substitutes for wound healing

Ideally tissue-engineered products should maintain the characteristics of the original tissue. For example, skin represents orthokeratinized epithelium and oral gingiva represents parakeratinized epithelium. The aim of this study was to develop an autologous full-thickness gingiva substitute suitable for clinical applications and to compare it with our autologous full-thickness skin substitute that is routinely used for healing chronic wounds. Autologous full-thickness skin and gingiva substitutes were constructed under identical culture conditions from 3-mm punch biopsies isolated from the upper leg or gingiva tissue, respectively. Both consisted of reconstructed epithelia on acellular dermis repopulated with fibroblasts. To compare the characteristics of the original and reconstructed tissue, differential morphological observations and expression of differentiation markers (keratins 6, 10, and 17 and stratum corneum precursors involucrin, loricrin, and SKALP) were determined. Skin and gingiva substitutes were transplanted onto therapy-resistant leg ulcers or tooth extraction sites in order to determine their effects on wound healing. The tissue-engineered constructs maintained many of the differential histological and immunohistochemical characteristics of the original tissues from which they were derived. The skin substitute was orthokeratinized, and the gingiva substitute was parakeratinized. Transplantation of skin (n = 19) and gingiva substitutes (n = 3) resulted in accelerated wound healing with no adverse effects. As identical culture systems were used to generate both the skin and gingiva substitutes, the differences observed in tissue (immuno)histology can be attributed to intrinsic properties of the tissues rather than to environmental factors (e.g., air or saliva). This study emphasizes the importance of closely matching donor sites with the area to be transplanted. Our results represent a large step forward in the area of clinical applications in oral tissue engineering, which have until now greatly lagged behind skin tissue engineering.

Complex nasal reconstruction

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Describe the goals of nasal reconstruction as they apply to extensive, complex defects that may also involve the adjacent lip or cheeks. 2. Understand the advantages and disadvantages of different options for reconstruction of lining, skeletal support, and skin cover. 3. Discuss current advances in complex nasal reconstruction, including microvascular reconstruction of lining and the three-stage forehead flap. 4. Understand the concepts of laminated and prelaminated flaps and their application in complex nasal defects.

SUMMARY

In this article, the authors review methods of reconstructing complex, multilayered nasal defects that may involve surrounding central facial structures. Different means of lining, skeletal support, and skin cover reconstruction are discussed. Emphasis is placed on newer, state-of-the art techniques and reinforcing basic principles.

Laryngotracheal reconstruction using prefabricated and preconditioned composite radial forearm free flaps

OBJECTIVE

Total or subtotal laryngectomy performed as surgical treatment of locally advanced laryngeal tumors requires a permanent laryngostomy or tracheostomy, and are both associated with severe and lifelong disability. The hitherto published reconstructive methods for the rehabilitation of patients after subtotal anterior laryngotracheal resection of extended laryngotracheal malignancies have not been thoroughly convincing.

METHODS

We present a successful method of extended laryngotracheal reconstruction that combines modern surgical and biomedical techniques.

RESULTS

A stable three-dimensional anterior neolarynx was prefabricated, including the use of vacuum-assisted prelamination and preconditioning of a composite radial forearm free flap, which was then transferred to the neck and vascularized by microvascular anastomosis to the cervical vessels. This reconstructive procedure permitted the restoration of a stable laryngotracheal conduit in two cases, with the subsequent successful closure of the tracheo-laryngostomy.

CONCLUSION

In the reported cases the pre- or post-operative irradiation did not compromise the success of reconstruction. Not only did our technique facilitate the rehabilitation of patients suffering from drawbacks of the laryngo-tracheofissure, but it also assisted in avoiding total laryngectomy in cases of advanced anterior laryngeal cancer by extending the indications for subtotal anterior laryngeal resections followed by reconstructive surgery.

Formation of a reliable capsular flap in a rat model

Prefabrication can be used to produce capsular flaps; other researchers have confirmed the feasibility of such flaps. Before the possibilities of capsular flaps can be explored, a reliable method to create these flaps has to be established first.

METHODS

To produce capsular flaps in a rat model, the femoral vascular bundle was sandwiched between two silicone sheets. Three different methods were used and described. The capsule that formed between the two silicone sheets receives its main blood supply from that vascular pedicle. In this way pedicled capsular flaps were created. These flaps were used as a carrier for a skin graft, thus pre-laminating them, to test their ability for reconstructive surgery. The results of the three different methods of creating capsular flaps in a rat model were described and their results were evaluated. Especially the amount of capsule formation and the viability of the skin grafts was observed and compared. The feasibility of pre-laminated capsular flaps is confirmed and the most reliable method of creating them is described.

Bone formation after sinus augmentation with engineered bone

OBJECTIVES

The aim of the following investigation was to quantify the resorption rate of tissue-engineered bone grafts in the maxillary sinus using volume measurements.

MATERIAL AND METHODS

Sinus floor augmentation using autologous bone grafts from the iliac crest (n=17, group 1) was compared with commercially produced transplants of human cells seeded on polyglycolid-polylactid (PLGA) scaffolds (Oral Bone) (n=14, group 2).

RESULTS

The total resorption rate for autologous transplants 3 months post operation was 29%, while the tissue-engineered bone showed a resorption rate of 90%. The autologous bone had a bone density of up to 266-551 Hounsfield units (HU), while sufficient mineralization of tissue-engineered bone was found in only one case (152 HU).

CONCLUSION

In this clinical study, the use of autologous cancellous bone grafts in sinus augmentation was more reliable than scaffolds containing cultured osteoblasts. Further tissue-engineered bone transplants should be examined to draw general conclusions about the use of tissue-engineered grafts compared with autologous bone grafts for maxillary sinus augmentation.

Clinical application of tissue-engineered transplants. Part I: mucosa

OBJECTIVES

The study series aims at testing the feasibility of the clinical application of tissue-engineered oral mucosa. The preliminary results were gathered over a period varying from 6 months to 12 years depending on the surgical method.

METHODS

Tissue-engineered oral mucosa was used to cover defects in various surgical procedures like vestibuloplasty (n=42), freeing of the tongue (n=10), prelaminating the radial flap (n=5) and reconstruction of the urethra (n=16). In all interventions small samples of oral mucosa were harvested, cut into small pieces, resuspended in culture medium and seeded into a culture flask. Cultured keratinocytes were transferred onto membranes which then were used to cover mucosal defects in the oral cavity.

RESULTS

To gain a graft of 15 cm(2) size a mucosa biopsy of 4-8 mm(2) and 40 ml autologous patients serum is needed. Tissue-engineered oral mucosa was applied successfully in all four surgical methods. Six months after transplantation a regular epithelial layering with a histological delimitation of the stratum, epithelial crest and a strong basal membrane appeared. According to the reception site the tissue engineered oral mucosa differentiated in several ways.

CONCLUSION

Tissue-engineered oral mucosa fulfils the requirements for clinical routine. With view to healing time and outcome it does not appear to be superior to regular harvested oral mucosa transplants. Because of a smaller harvesting defect and primary wound closure at the actual operation site the patients' convenience is increased. Thus this method reduces morbidity and advances the quality of life.

Mucosal keratinocyte isolation: a short comparative study on thermolysin and dispase

New techniques for reconstructing large defects of the floor of the mouth include the use of cultured mucosal substitutes. The purpose of this study was to compare dispase and thermolysin for keratinocyte isolation. Keratinocyte yield per surface area of rabbit buccal mucosa was assessed by histology, cytokeratin 13 (CK13) staining, seeding efficiency analysis and cell diameter quantification. Surface areas of cultured mucosa were calculated. Histology showed that treatment by thermolysin resulted in incomplete separation of epidermis from dermis. Also, the absolute number of keratinocytes/cm(2) isolated mucosa, cell yield, cell size and seeding efficiencies was higher in the dispase group. A 3.45-fold larger graft could be reconstituted using dispase. The use of dispase, rather than thermolysin, to isolate cells from buccal mucosa is concluded to be favourable.

Fibroblasts Accelerate Culturing of Mucosal Substitutes

Reconstruction of large mucosal defects of the floor of the mouth is typically performed with keratinizing skin. Drawbacks include donor site defects and hair bearing of the flaps. Cultured mucosal substitutes (CMSs) have been developed for clinical use to replace keratinizing skin. Acellular dermis is often used as a dermal carrier for autologous cells, because it reduces wound contraction and is easier for the surgeon to handle than, for example, collagen gels. A major problem of CMSs using acellular dermis is variation in epidermal quality. To improve the quality of the CMSs, human fibroblasts were incorporated into the acellular dermis and seeded with human keratinocytes. To study the role of the fibroblasts in epidermal morphology and basement membrane formation, CMSs were stained for differentiation markers beta1 integrin, cytokeratin 10, and involucrin after 1 and 2 weeks in culture. Basement membrane formation was analyzed using laminin 5 and collagen IV and VII staining; proliferation was analyzed using Ki-67 staining. The epidermises of fibroblast-containing CMSs matured faster into a well-organized epithelium than did those that did not contain CMSs. A 52.7% increase in basal cells, a 53.5% increase in mitosis index, and a 78.0% increase in keratinocyte cell layers were observed. Addition of fibroblasts reduced culturing time and enhanced proliferation, maturation, and quality of the epidermis.

Comparison of the Radial Forearm Flap and the Thinned Anterolateral Thigh Cutaneous Flap for Reconstruction of Tongue Defects: An Evaluation of Donor-Site Morbidity

The radial forearm flap is commonly used for reconstruction of tongue defects following tumor extirpation. This flap is easy to harvest and offers thin tissue with large-caliber vessels. However, its use leaves behind a conspicuous aesthetic deformity in the forearm and requires the sacrifice of a major artery of that limb, the radial artery. The anterolateral thigh cutaneous flap has found clinical applications in the reconstruction of soft-tissue defects requiring thin tissue. More recently, in a thinned form, the anterolateral thigh flap has been used for reconstructing defects of the tongue with functional results equivalent to that of the radial forearm flap. For the reconstruction of tongue defects, these two flaps could provide similar soft-tissue coverage, but they seem to result in different donor-site appearances. The donor site is closed primarily, leaving only a linear scar that is inconspicuous with normal clothing, and no functional deficit is left behind in the thigh. Thus, for the supply of flaps for tongue defects, a comparison between the radial forearm flap and the anterolateral thigh flap donor sites is provided in this study. Between December of 2000 and August of 2002, 41 patients who underwent reconstruction of defects of the tongue using either a radial forearm flap or an anterolateral thigh flap were evaluated. The focus was on the evaluation of the functional and aesthetic outcome of the donor site after harvesting these flaps for the purpose of reconstructing either total or partial tongue defects. Finally, a comparison was performed between the donor sites of the two flaps. The disadvantages of the radial forearm flap include the conspicuous unattractive scar in the forearm region, pain, numbness, and the sacrifice of a major artery of the limb. In some patients, the donor-site scar of the forearm acted as a social stigma, preventing these patients from leading a normal life. In contrast, the anterolateral thigh cutaneous flap, after thinning, achieved the same results in reconstructing defects of the tongue without the associated donor-site morbidity. Most importantly, the donor site in the thigh could be closed primarily in almost all patients without any functional deficit. The thinned anterolateral thigh cutaneous flap is a viable substitute for the radial forearm flap when reconstructing defects of the tongue. The results achieved are similar to those of the radial forearm flap, and the donor-site morbidity is significantly decreased.

Clinical applications of tissue engineered constructs

The reconstruction of soft tissue defects poses a challenge for plastic surgeons and tissue engineers. The construction of a biologically, functionally, and cosmetically successful replacement part will involve the combination of a composite that contains endoderm, mesoderm, and ectoderm. It will be active in immune surveillance and function. It must be durable to withstand the stress and strain encountered by the skin. Such a composite will involve the use of bone, cartilage, muscle, blood vessels, nerves, connective tissue, dermis, and epidermis. Fortunately, many of these tissues are among the best studied by tissue engineers. The future of this field will likely involve to some degree the co-mingling of current reconstructive modalities, including the techniques of prefabrication and pre-lamination, with more aggressive and successful tissue engineering technology and the rapidly developing science of stem cell biology. Tissues synthesized in vitro with better structure, color, and texture can be pre-laminated to a site that has already been prefabricated. Prefabrication of a bio-absorbable matrix can create a well perfused scaffold onto which larger subunits can be prelaminated. The future of this field of endeavor is exciting, and, with further research, experience, and interdisciplinary collaboration, bioengineered tissue constructs will become a reality.

Effects of subepithelial fibroblasts on epithelial differentiation in human skin and oral mucosa: heterotypically recombined organotypic culture model

The stratified squamous epithelia differ regionally in their patterns of morphogenesis and differentiation. Although some reports suggested that the adult epithelial phenotype is an intrinsic property of the epithelium, there is increasing evidence that subepithelial connective tissue can modify the phenotypic expression of the epithelium. The aim of this study was to elucidate whether the differentiation of cutaneous and oral epithelia is influenced by underlying mesenchymal tissues. Three normal skin samples and three normal buccal mucosa samples were used for the experiments. Skin equivalents were constructed in four ways, depending on the combinations of keratinocytes (cutaneous or mucosal keratinocytes) and fibroblasts (dermal or mucosal fibroblasts), and the effects of subepithelial fibroblasts on the differentiation of oral and cutaneous keratinocytes were studied with histological examinations and immunohistochemical analyses with anti-cytokeratin (keratins 10 and 13) antibodies. For each experiment, three paired skin equivalents were constructed by using single parent keratinocyte and fibroblast sources for each group; consequently, nine (3 x 3) organotypic cultures per group were constructed and studied. The oral and cutaneous epithelial cells maintained their intrinsic keratin expression. The keratin expression patterns in oral and cutaneous epithelia of skin equivalents were generally similar to their original patterns but were partly modified exogenously by the topologically different fibroblasts. The mucosal keratinocytes were more differentiated and expressed keratin 10 when cocultured with dermal fibroblasts, and the expression patterns of keratin 13 in cutaneous keratinocytes cocultured with mucosal fibroblasts were different from those in keratinocytes cocultured with cutaneous fibroblasts. The results suggested that the epithelial phenotype and keratin expression could be extrinsically modified by mesenchymal fibroblasts. In epithelial differentiation, however, the intrinsic control by epithelial cells may still be stronger than extrinsic regulation by mesenchymal fibroblasts.

Making bone: implant insertion into tissue-engineered bone for maxillary sinus floor augmentation-a preliminary report

Autologous, allogenic and alloplastic materials for bony reconstruction in the cranio-maxillofacial area have many drawbacks thus stimulating the on-going search for new (bio-)materials. Whereas cultivated skin and mucosa are already in clinical routine use in head and neck reconstruction, so far there has been no successful clinical application to the best of our knowledge of periosteum-derived, tissue-engineered bone for augmentation of the edentulous posterior maxilla. In a pilot study, augmentation of the posterior maxilla was carried out using a bone matrix derived from mandibular periosteal cells on a polymer fleece. This paper demonstrates fabrication of the matrix, clinical application, and the histological results in two patients. The results suggest that periosteum-derived osteoblasts on a suitable matrix form lamellar bone within 4 months which allows reliable implant insertion.

Lining the mouth floor with prelaminated fascio-mucosal free flaps: clinical experience

Soft-tissue defects of the mouth floor need thin, foldable, and pliable tissues able to preserve local anatomy as well as chewing, phonation, and deglutition. The oral mucosa is made of a stratified, nonkeratinized, epithelium-secreting mucus, which lubricates the oral cavity and facilitates tongue movements. No flap exists that can reproduce the physiology of the oral mucosa better than the oral mucosa itself. Prefabrication of mucosal flaps may represent the best solution. Therefore, 10 consecutive cases of mouth floor cancer were treated with prelamination of the fascia antibrachialis with mucosal grafts obtained from the healthy cheek, and with subsequent transplantation 3 weeks later. A significant increase in mucosal graft surface was seen in all cases, with a mean size twice the original. All flaps healed uneventfully. Follow-up time ranged between 2-60 months (average, 26.6 months). Morphological and functional results were excellent. Tongue motility, speech intelligibility, and swallowing were reestablished in all treated cases. Mucosal prelamination of the forearm fascia is feasible and allows physiological reconstruction of oral cavity defects up to 6 x 4 cm.