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Biomedical subjects

Michael J Yaremchuk

Publications and source records attributed to Michael J Yaremchuk.

15 recordsLinked to original sources
PubMed2006

Tissue engineered cartilage integration to live and devitalized cartilage: a study by reflectance mode confocal microscopy and standard histology.

This study investigated the in vivo formation of engineering cartilage within living or devitalized cartilage discs using reflectance mode confocal microscopy and conventional light microscopy. Pig articular chondrocytes were suspended in fibrin glue and placed between two cartilage discs. Four experimental groups were prepared: in groups 1 and 2, the cell-hydrogel composite was placed between two live or between two devitalized cartilage discs, respectively; in groups 3 and 4, acellular fibrin glue was placed between two live or between two devitalized cartilage discs, respectively. Samples were implanted in the back of nude mice and analyzed after 2, 5, and 8 weeks. Results showed that engineered cartilage seems to grow more homogenously when the cell-seeded gel was placed between devitalized cartilages than when it was placed between live cartilage matrices. Confocal microscopy provides valuable information on the integration of tissue-engineered cartilage with native tissue and could be useful for nondestructive imaging in vivo.

Animals↗
PubMed2006

Review of injectable cartilage engineering using fibrin gel in mice and swine models.

More than a decade of work has been devoted to engineering cartilage for articular surface repair. This review covers the use of fibrin gel polymer as an injectable scaffold for generating new cartilage matrix from isolated articular chondrocytes beginning with studies in mice and culminating in an applied study in swine joints. These studies began with developing a formulation of fibrin that was injectable and promoted cartilage matrix formation. Subsequent studies addressed the problems of volume loss after the scaffolds were placed in vivo by adding lyophilized cartilage matrix. Additional studies focused on the ability of isolated chondrocytes to heal and repair cartilage in a model that could be biomechanically tested. In conclusion, this series of studies demonstrated that fibrin gel is a suitable polymer gel for generating new cartilage matrix from articular chondrocytes. The new matrix is capable of forming mechanical bonds between cartilage disks and can lead to healing and integration. Armed with these results, implantation of fibrin-cell constructs into defects in swine knees showed new cartilage formation and filling of the defects. Continuing work in these models with fibrin and other polymerizable hydrogels could result in a suitable cell-based therapy for articular cartilage lesions.

Animals↗
PubMed2006

Cranioplasty with subcutaneously preserved autologous bone grafts.

BACKGROUND: The efficacy of reconstructing a cranial defect with the craniectomy bone graft (bone flap) banked in a subcutaneous pocket of the abdominal wall after emergency decompressive craniotomy was evaluated. METHODS: A retrospective study was performed on 53 of 65 consecutive patients who underwent emergency decompressive craniectomy and bone graft placement in the abdominal wall and survived to graft replacement. Clinical outcome after graft replacement was determined by the adequacy of the recovered craniectomy graft to achieve satisfactory reconstruction, the incidence of infection and the need for revisional surgery. RESULTS: Forty-nine of the 53 patients (92 percent) in whom delayed autogenous graft replacement was attempted achieved a satisfactory one-stage reconstruction. In 42 of these 49 patients, autogenous graft replacement alone was performed. In eight patients it was necessary to supplement the graft with alloplastic material to achieve desired contour. One patient who underwent reconstruction with the autogenous bone graft alone, underwent late revision cranioplasty to improve contour. There were three infections. One graft was found infected in the abdominal pocket at retrieval. Two were lost to operative infection after graft replacement. Histology of two stored grafts performed after abdominal pocket retrieval demonstrated a mixture of necrotic and newly formed woven bone. A bone scan performed 1 year after graft replacement showed radionuclide activity of the graft almost identical to that of intact neighboring bone. CONCLUSIONS: Subcutaneous storage preserves viability of portions of autogenous bone grafts. Cranioplasty performed with a subcutaneously preserved craniectomy graft has a low revision rate.

Abdomen↗
PubMed2006

Tissue engineering cartilage with aged articular chondrocytes in vivo.

BACKGROUND: Tissue engineering has the potential to repair cartilage structures in middle-aged and elderly patients using their own "aged" cartilage tissue as a source of reparative chondrocytes. However, most studies on tissue-engineered cartilage have used chondrocytes from postfetal or very young donors. The authors hypothesized that articular chondrocytes isolated from old animals could produce neocartilage in vivo as well as articular chondrocytes from young donors. METHODS: Articular chondrocytes from 8-year-old sheep (old donors) and 3- to 6-month-old sheep (young donors) were isolated. Cells were mixed in fibrin gel polymer at 40 x 10 cells/ml until polymerization. Cell-polymer constructs were implanted into the subcutaneous tissue of nude mice and harvested at 7 and 12 weeks. RESULTS: Samples and native articular cartilage controls were examined histologically and assessed biochemically for total DNA, glycosaminoglycan, and hydroxyproline content. Histological analysis showed that samples made with chondrocytes from old donors accumulated basophilic extracellular matrix and sulfated glycosaminoglycans around the cells in a manner similar to that seen in samples made with chondrocytes from young donors at 7 and 12 weeks. Biochemical analysis revealed that DNA, glycosaminoglycan, and hydroxyproline content increased in chondrocytes from old donors over time in a pattern similar to that seen with chondrocytes from young donors. CONCLUSIONS: This study demonstrates that chondrocytes from old donors can be rejuvenated and can produce neocartilage just as chondrocytes from young donors do when encapsulated in fibrin gel polymer in vivo. This study suggests that middle-aged and elderly patients could benefit from cartilage tissue-engineering repair using their own "aged" articular cartilage as a source of reparative chondrocytes.

Age Factors↗
PubMed2005

Making concave faces convex.

Inadequate projection of the midface skeleton results in midface concavity. Patients with this skeletal morphology tend to have prominent eyes and noses. Lack of skeletal support for the midface soft tissue envelope predisposes to premature cheek descent, resulting in palpebral fissure distortion and lower lid "bags," an appearance of early aging. Concave midfaces can be made convex with two basic maneuvers performed through intraoral and periorbital incisions. Midface skeletal projection can be increased by augmenting the facial skeleton with alloplastic implants. Multiple implants are required to replicate the complex curvature of the midface skeleton and to avoid impingement on the infraorbital nerve. Subperiosteal elevation of the midface soft tissues and repositioning provides cheek fullness and narrows the palpebral fissure while masking eyelid "bags." The resultant midface concavity makes the eyes and nose appear less prominent. This procedure has been a safe and effective treatment for 14 patients treated over a 4-year period.

Adult↗
PubMed2005

Tissue-engineered flexible ear-shaped cartilage.

BACKGROUND: Previous attempts to engineer human ear-shaped constructs mimicked human shape but lacked the flexibility and size of a human ear. Recently, the authors engineered flexible cartilage by incorporating a perichondrium-like layer into the construct. In this study, they used lyophilized swine perichondrium as a pseudoperichondrium, examined its ability to confer flexibility to tissue-engineered cartilage, and used it to engineer flexible cartilage in the shape and size of a human ear. METHODS: Auricular chondrocytes and perichondrium were isolated from swine. Chondrocytes were mixed with fibrin polymer and gelled to form 5 x 20-mm constructs. Constructs alone (control, n = 6) or constructs sandwiched between two layers of lyophilized swine perichondrium (experimental, n = 6) were implanted into athymic mice. Auricular chondrocytes in fibrin polymer and lyophilized perichondrium were also used to form a tri-layer, ear-shaped construct, which was implanted into an athymic rat and externally stented for 6 weeks (n = 1). At 12 weeks, constructs were analyzed with histology and gross mechanical testing. RESULTS: New cartilaginous tissue was engineered in both the experimental and control groups. In samples laminated with lyophilized swine perichondrium, the intimate integration of the laminate with the neocartilage closely resembled the histoarchitecture of the native swine ear. Experimental constructs had mechanical properties similar to those of the native swine ear, while control constructs fractured with similar testing. The engineered ear could not be fractured with gross mechanical testing, and its size, shape, and flexibility remained stable. CONCLUSIONS: This study demonstrates that it is possible to engineer a cartilage construct that resembles the human ear not only in shape but also in size and flexibility. This study also confirms that lamination is a reliable method to confer elastic-like flexibility to an engineered cartilage construct.

Animals↗
PubMed2005

Producing a flexible tissue-engineered cartilage framework using expanded polytetrafluoroethylene membrane as a pseudoperichondrium.

BACKGROUND: Both native and engineered cartilage is brittle and fractures easily without perichondrium. The aim of this study was to understand the role of the perichondrium and try to enhance the flexible properties of tissue-engineered cartilage using expanded polytetrafluoroethylene (ePTFE) membrane as a pseudoperichondrium. METHODS: The study was conducted in two phases. In phase I, native swine auricular cartilage of different thicknesses was studied by histologic evaluation and failure testing. Next, isolated perichondrium was bonded to native cartilage slices using fibrin glue or Dermabond and tested to failure. In phase II, swine auricular chondrocytes were suspended in fibrin glue. The chondrocyte-fibrin glue composites were then bound to expanded polytetrafluoroethylene membrane in two trilaminar configurations: In group EC-1, the membrane was in the center, whereas it was on the surfaces in group EC-2. Specimens were implanted into nude mice for 4 weeks, 8 weeks, 12 weeks, and 8 months and subjected to histologic evaluation and failure testing. RESULTS: In phase I, the results demonstrated that perichondrium securely bonded to the cartilage plays an important role in maintaining the flexible nature of elastic cartilage. In phase II, failure testing revealed that specimens in group EC-1 (expanded polytetrafluoroethylene core) were fractured during bending and destroyed after torsion, whereas those in group EC-2 (cartilage core) returned to their original shape without fracturing even after rigorous torsion. Histologic analysis demonstrated that transplanted chondrocytes penetrated into the microporous structure of expanded polytetrafluoroethylene and created a bond to it. CONCLUSION: It is possible to engineer flexible cartilage using expanded polytetrafluoroethylene as a pseudoperichondrium.

Animals↗
PubMed2004

Improving periorbital appearance in the "morphologically prone".

Patients with prominent eyes are predisposed to lower lid descent and rounding of the palpebral fissure. This deformity may be exaggerated and symptomatic after conventional lower blepharoplasty. Normalization of the periorbital appearance in "morphologically prone" patients involves three basic maneuvers. Augmenting the projection of the infraorbital rim with an alloplastic implant effectively changes the skeletal morphology, thereby providing support for the lower lid and midface soft tissues. Subperiosteal freeing and elevation of the lower lid and midface recruits soft tissues and allows lower lid repositioning. Lateral canthopexy restores palpebral fissure shape and provides additional lid support. The technique can be adapted for morphologically prone patients who are first seeking improvement in their periorbital appearance or for those whose lid malposition and round eye appearance have been exaggerated by previous lower blepharoplasty. This surgery has been effective treatment for 13 morphologically prone patients operated on over a 4-year period.

Adult↗
PubMed2004

Injectable tissue-engineered cartilage with different chondrocyte sources.

Injectable engineered cartilage that maintains a predictable shape and volume would allow recontouring of craniomaxillofacial irregularities with minimally invasive techniques. This study investigated how chondrocytes from different cartilage sources, encapsulated in fibrin polymer, affected construct mass and volume with time. Swine auricular, costal, and articular chondrocytes were isolated and mixed with fibrin polymer (cell concentration of 40 x 10 cells/ml for all groups). Eight samples (1 cm x 1 cm x 0.3 cm) per group were implanted into nude mice for each time period (4, 8, and 12 weeks). The dimensions and mass of each specimen were recorded before implantation and after explantation. Ratios comparing final measurements and original measurements were calculated. Histological, biochemical, and biomechanical analyses were performed. Histological evaluations (n = 3) indicated that new cartilaginous matrix was synthesized by the transplanted chondrocytes in all experimental groups. At 12 weeks, the ratios of dimension and mass (n = 8) for auricular chondrocyte constructs increased by 20 to 30 percent, the ratios for costal chondrocyte constructs were equal to the initial values, and the ratios for articular chondrocyte constructs decreased by 40 to 50 percent. Constructs made with auricular chondrocytes had the highest modulus (n = 3 to 5) and glycosaminoglycan content (n = 4 or 5) and the lowest permeability value (n = 3 to 5) and water content (n = 4 or 5). Constructs made with articular chondrocytes had the lowest modulus and glycosaminoglycan content and the highest permeability value and water content (p < 0.05). The amounts of hydroxyproline (n = 5) and DNA (n = 5) were not significantly different among the experimental groups (p > 0.05). It was possible to engineer injectable cartilage with chondrocytes from different sources, resulting in neocartilage with different properties. Although cartilage made with articular chondrocytes shrank and cartilage made with auricular chondrocytes overgrew, the injectable tissue-engineered cartilage made with costal chondrocytes was stable during the time periods studied. Furthermore, the biomechanical properties of the engineered cartilage made with auricular or costal chondrocytes were superior to those of cartilage made with articular chondrocytes, in this model.

Animals↗
PubMed2003

Tissue engineering of cartilage.

The primary goal of engineering cartilage as a therapeutic approach is to restore the physiological conditions of an affected or defective tissue in the body. Cartilage tissue is distributed widely in the human body and possesses an organization related to the specific demand of a particular anatomical region. In selecting the proper material for engineering cartilage, the functional demands of the replacement tissue must be considered. In summary, there is a multitude of scaffolds, naturally occurring and synthetic, that are suitable for engineering cartilage. Investigators have shown that the characteristics of the neocartilage differ significantly depending upon which scaffold is used. There are also large differences when a single scaffold is tested in vitro as opposed to in vivo. Moreover, the addition of other materials internally or externally to the cartilage composite influences the physical and biomechanical properties of the newly formed tissue. The results achieved so far are extremely encouraging and motivate further investigative efforts in the field. The biochemical composition and, more importantly, the biomechanical properties of the native tissue still represent the ideal replacement tissue.

Biocompatible Materials↗
PubMed2003

Restoring palpebral fissure shape after previous lower blepharoplasty.

The youthful palpebral fissure can be described as long and narrow. Both the aging process and transcutaneous lower blepharoplasty can cause descent of the lower lid margin and medial migration of the lateral canthus, resulting in a rounding of the palpebral fissure. This article presents a technique to correct significant postsurgical lower lid malposition and palpebral fissure distortion without the use of outer or inner lamellar grafts. In overview, subperiosteal dissection frees scarred lid structures and cheek soft tissues, creating a continuous composite flap. Elevation of the cheek soft tissues recruits deficient outer lamellae and allows the sub-orbicularis oculi fat to be positioned between the orbital rim and scarred lid structures, filling this space and helping to support the repositioned lid margin. Titanium screws placed in the lateral orbit provide a point for secure fixation of elevated cheek tissues. Transosseous wire fixation securely repositions the lateral canthus. This procedure not only restores lower lid position and the vertical height of the palpebral fissure, but it also restores the palpebral fissure's horizontal length and the lateral canthal angle. It has been effective in correcting palpebral fissure distortion after lower blepharoplasty in 15 patients during a 6-year period.

Adult↗
PubMed2003

Facial skeletal reconstruction using porous polyethylene implants.

A retrospective review of clinical outcomes was performed to determine the clinical utility and morbidity associated with the use of porous polyethylene facial implants. Three hundred seventy implants were placed in 162 consecutive patients, in 178 operations performed in 11 years. The number of patients, the number of implants used, and the average follow-up period were categorized according to the cause of the deformity. The resultant distribution was as follows: acquired (tumor-related), 17 patients, 39 implants, and 30 months; congenital, eight patients, 31 implants, and 92 months; aesthetic, 39 patients, 97 implants, and 24 months; secondary posttraumatic, 48 patients, 139 implants, and 37 months; and acute trauma (internal orbit reconstruction), 50 patients, 64 implants, and 9 months. The distribution of implants according to location was as follows: frontal, 21; temporal, 30; internal orbit, 145; infraorbital rim, 28; malar, 58; paranasal, 29; nasal, 13; mandible, 24; and chin, 22. The combined average follow-up period per patient was 27 months (range, immediate postoperative period to 11 years). All implants were placed in the subperiosteal plane, and the majority were fixed with titanium screws. Antibiotics were administered perioperatively. No implants were extruded or migrated, formed clinically apparent capsules, or caused symptoms attributable to bioincompatibility. The overall reoperation rate was 10 percent (n = 16), which included operations to remove implants because of acute infections (2 percent, n = 3) or a late infection (1 percent, n = 1), to remove implants causing displeasing contours (2 percent, n = 3), and to improve contours (6 percent, n = 9). Porous polyethylene implants have biomaterial properties favorable for facial skeletal augmentation. Screw application of the implants to the skeleton allows precise predictable contouring, thus limiting the need for revisional surgical procedures.

Adolescent↗
PubMed2003

Improving aesthetic outcomes after alloplastic chin augmentation.

A novel approach to increase chin projection with alloplastic material is presented. Key aspects of the technique include the consideration of anthropometric normal values in preoperative assessment and planning, a submental approach with wide subperiosteal exposure of the area to be augmented, the use of two-piece porous polyethylene implants for augmentation, and screw fixation of the implant to the mandible. Screw fixation improves the predictability and precision of reconstruction by preventing implant displacement, by obliterating gaps between the implant and the facial skeleton, and by facilitating final implant contouring. In a series of 46 patients (24 primary and 22 secondary) operated on over a 6-year period, this approach allowed anatomically correct, stable chin contours to be created. Iatrogenic problems with macrogenia, mentalis dysfunction, and soft-tissue distortion resulting from implant migration and capsular contracture have been avoided. There have been no infections. Two patients who had had multiple previous chin operations requested revisional surgery to refine contour.

Adolescent↗
PubMedDate not supplied

Integrative repair of cartilage with articular and nonarticular chondrocytes.

Articular chondrocytes can synthesize new cartilaginous matrix in vivo that forms functional bonds with native cartilage. Other sources of chondrocytes may have a similar ability to form new cartilage with healing capacity. This study evaluates the ability of various chondrocyte sources to produce new cartilaginous matrix in vivo and to form functional bonds with native cartilage. Disks of articular cartilage and articular, auricular, and costal chondrocytes were harvested from swine. Articular, auricular, or costal chondrocytes suspended in fibrin glue (experimental), or fibrin glue alone (control), were placed between disks of articular cartilage, forming trilayer constructs, and implanted subcutaneously into nude mice for 6 and 12 weeks. Specimens were evaluated for neocartilage production and integration into native cartilage with histological and biomechanical analysis. New matrix was formed in all experimental samples, consisting mostly of neocartilage integrating with the cartilage disks. Control samples developed fibrous tissue without evidence of neocartilage. Ultimate tensile strength values for experimental samples were significantly increased (p < 0.05) from 6 to 12 weeks, and at 12 weeks they were significantly greater (p < 0.05) than those of controls. We conclude that articular, auricular, and costal chondrocytes have a similar ability to produce new cartilaginous matrix in vivo that forms mechanically functional bonds with native cartilage.

Animals↗