Poly(L-lactide) implants in repair of defects of the orbital floor: an animal study

Bony realignment in surgically treated orbital blowout fractures based on computed tomography

BACKGROUND

This study investigated postoperative bony realignment using follow-up computed tomography (CT) scans of patients with blowout fracture repair using an alloplastic implant.

METHODS

This is a retrospective study of patients who underwent surgical treatment for orbital blowout fractures and had follow-up CT at least 4 months after the surgery. Preoperative, early, and late postoperative CT scans were obtained to assess the outcome measures including reduction completeness, reconstructed wall composition, and presence of implant-related complications. CT scans of patients with complications were compared with those of patients without complications for radiologic changes.

RESULTS

Our study comprised 48 orbits from 48 patients. The mean age was 28.1 years, the mean time from injury to surgery was 18.3 days, and the mean time from surgery to the latest CT scan was 47.2 months (4-212 months). Most orbits (n = 41, 91.7%) showed complete reduction postoperatively. Among the 36 patients without complications, 89% showed total and 11% showed partial bony coverage. Among the 12 patients with complications, 42% showed total, 42% showed partial, and 16% showed no bony coverage. Partial or no bony coverage was noted in 11.1% (4/36) of patients without complications and in 58.3% (7/12) with complications. Reconstructed wall composition was significantly related to the presence of complications (p = 0.002). The group with total bony coverage was younger than the group with partial or no bony coverage (p = 0.048).

CONCLUSIONS

A displaced bone in the sinus is repositioned in the early postoperative stage along with the implant substantially. Partial or no bony coverage was related to the complicated cases. Young age was found to be a favoring factor for total bony coverage over the implant.

The Use of Functional Biomaterials in Aesthetic and Functional Restoration in Orbital Surgery

The integration of functional biomaterials in oculoplastic and orbital surgery is a pivotal area where material science and clinical practice converge. This review, encompassing primary research from 2015 to 2023, delves into the use of biomaterials in two key areas: the reconstruction of orbital floor fractures and the development of implants and prostheses for anophthalmic sockets post-eye removal. The discussion begins with an analysis of orbital floor injuries, including their pathophysiology and treatment modalities. It is noted that titanium mesh remains the gold standard for orbital floor repair due to its effectiveness. The review then examines the array of materials used for orbital implants and prostheses, highlighting the dependence on surgeon preference and experience, as there are currently no definitive guidelines. While recent innovations in biomaterials show promise, the review underscores the need for more clinical data before these new materials can be widely adopted in clinical settings. The review advocates for an interdisciplinary approach in orbital surgery, emphasizing patient-centered care and the potential of biomaterials to significantly enhance patient outcomes.

Resorbable Implants for Orbital Fractures: A Systematic Review

BACKGROUND

Orbital fractures are one of the most common sequelae of facial trauma.

OBJECTIVE

The objective of this study was to summarize published data for resorbable implants in orbital reconstruction, including polymer composition, degradation characteristics, osteoconductivity, and complications such as enophthalmos, diplopia, and peri-implant inflammation. A literature search of the National Library of Medicine was performed via PubMed using the keyword resorbable orbital implant. A total of 27 studies were reviewed. Strength of data was assessed according to the Oxford Centre criteria.

RESULTS

Most commercially available implants provide adequate tensile strength for up to 6 months (with the exception of polydioxanone, which loses strength within 1 month, and poly(D,L-lactide) within 3 months). This is sufficient for the isolated orbital floor or medial wall (tensile strength, ~300 MPa) but insufficient for reconstruction of load-bearing areas (eg, the inferior orbital rim with tensile strength of ~1.2 GPa). Thicker products (>1 mm) have increased risk for delayed inflammation than thinner products. Postoperative complications including delayed inflammation (0%-9%), eyelid malposition (0%-5%), enophthalmos (5%-16%), diplopia (0%-16%), infection (0%-2%), and infraorbital nerve hypesthesia (2%-18%) are variably distributed across implants with several notable exceptions: poly(L-lactide) has an increased risk of delayed inflammation, and polydioxanone has a risk of delayed enophthalmos and hematoma.

CONCLUSIONS

Resorbable implants are suitable for isolated medial wall or floor fractures with intact bony buttresses and function as a barrier rather than a load-bearing support.

Morphological Evaluation of Soft Tissue Augmentation Using Porous Poly-DL-Lactic Acid With Straight Holes

OBJECTIVES

This study investigated the biological reaction to porous poly-DL-lactic acid (PDLLA) scaffolds with holes for soft tissue augmentation.

MATERIALS AND METHODS

The control group was porous PDLLA with a diameter of 5.0 mm and a height of 2.0 mm. For the 2 test groups, 7 holes were drilled from the upper to the lower base of the scaffolds; the holes had diameters of 0.5 and 1.0 mm. A scaffold was placed in the periosteum of the cranium. The height and molecular weight (Mw) of the scaffolds were measured at 4 and 8 weeks. Hematoxylin and eosin staining was used to measure the connective tissue and blood vessel areas.

RESULTS

All groups had similar scaffold heights, but the Mw decreased significantly over time. There were significant differences in the connective tissue and blood vessel areas among the control, 0.5-mm, and 1.0-mm groups at the same time point. The soft tissue was increased by drilling holes in the scaffolds.

CONCLUSION

Porous poly-DL-lactic acid (PDLLA) contributed favorable prognosis for soft tissue. A wider hole was associated with increased connective tissue and blood vessel areas. The scaffold height and Mw were not impacted by size of the holes.

Application of Computer-Aided Designing and Rapid Prototyping Technologies in Reconstruction of Blowout Fractures of the Orbital Floor

INTRODUCTION

Traumatology of the maxillofacial region represents a wide range of different types of facial skeletal injuries and encompasses numerous treatment methods. Application of computer-aided design (CAD) in combination with rapid prototyping (RP) technologies and three-dimensional computed tomography techniques facilitates surgical therapy planning for efficient treatment.

OBJECTIVE

The purpose of this study is to determine the efficiency of individually designed implants of poly-DL-lactide (PDLLA) in the reconstruction of blowout fractures of the orbital floor.

METHODS

In the course of a surgical treatment, individually designed implants manufactured by CAD/RP technologies were used. Preoperative analysis and postoperative monitoring were conducted to evaluate the successfulness of orbital floor reconstruction using customized PDLLA implants, based on: presence of diplopia, paresthesia of infraorbital nerve, and presence of enophthalmos.

RESULTS

In 6 of the 10 patients, diplopia completely disappeared immediately after surgical procedure. Diplopia gradually disappeared after 1 month in 3 patients, whereas in 1, it remained even after 6 months. In 7 patients, paresthesia disappeared within a month after surgery and in 3 patients within 2 months. Postoperative average Orbital volume (OV) of the injured side (13.333 ± 3.177) was significantly reduced in comparison with preoperative OV (15.847 ± 3.361) after reconstruction of the orbital floor with customized PDLLA implant (P < 0.001). Thus, average OV of corrected orbit was not different compared with the OV of the uninjured orbit (P = 0.981).

CONCLUSIONS

Reconstruction of blowout fractures of the orbital floor by an individually designed PDLLA implant combined with virtual preoperative modeling allows easier preoperative preparation and yields satisfactory functional and esthetic outcomes.

Comparison of efficacy of mandible and iliac bone as autogenous bone graft for orbital floor reconstruction

OBJECTIVE

This study evaluated and compared the efficacy of mandible and iliac bone as autogenous bone graft for correction of orbital floor fractures.

PATIENTS AND METHODS

Twenty patients who suffered orbital floor fractures took part in the study. The subjects enrolled in the study sustained both isolated orbital floor fracture and orbital floor fracture associated with fracture of zygomatico-maxillary complex. Each inferior orbital wall was reconstructed using either a mandible bone graft or an iliac graft. Mandibular symphysis was opted as a donor site for graft harvest from mandible and anterior iliac crest for the iliac group. CT scans were taken before the operation. Inclusion criteria consisted of at least 2 months postsurgical follow-up, pre- and post-surgical photographic documentation, and complete medical records regarding inpatient and outpatient data. To describe the distribution of complications and facilitate statistical analysis, we categorized our findings into diplopia, enophthalmos, and restriction of ocular movements before and after treatment. We also considered the time required for the harvest of the grafts and the donor site complications. A comparative study was carried out using Chi square test and student t test. We considered P value <0.05 to be statistically significant.

RESULTS

Ten iliac crest grafts and ten mandible bone grafts were placed. The mean age of the patients was 33.1 years. 80 % of the patients were males. The most common complication of orbital floor fracture was diplopia, followed by enophthalmos and restriction of ocular movements. The post operative results were compared after 2 months of the surgery. In iliac crest group, diplopia got corrected in six out of seven patients (85 %), enophthalmos in four out of five patients (80 %) and restricted ocular movement showed 100 % correction. While in mandible group, diplopia and ocular movement showed 100 % correction and enophthalmos got corrected in five out of six patients (83 %). No statistically significant differences were found between the two groups on comparing these variables. On the other hand the mean time required for the harvest of iliac graft and mandible graft was 30.2 ± 3.52 min and 16.8 ± 1.75 min respectively. The difference was statistically significant.

CONCLUSION

There is no difference in the ability of mandible and anterior iliac crest bone grafts to correct post-traumatic diplopia, enophthalmos and restricted ocular movements. But the time and ease of harvest of the graft from mandible was comparatively less and easy especially when the treating doctor was an oral and maxillofacial surgeon. Secondly the post-operative morbidity was low and the quality and contour of the bone graft was very adaptable for the reconstruction of the orbital floor.

Biomaterials for reconstruction of the internal orbit

Orbital floor injuries, alone or combination with other facial fractures, are one of the most commonly encountered midface fractures. Techniques for orbital reconstruction have migrated away from autogenous bone grafts to well-tolerated alloplasts, such as titanium and Medpor. Material for reconstructing the orbit can then be selected based on requirements of the defect matched to the mechanical properties of the material. Material selection is largely and ultimately dependent upon surgeon preference.

Vegetal polymer in repair of defects of the orbital floor: an experimental study in rabbits

BACKGROUND

An experimental study was done to assess the ability of the vegetal polymer miniplates and screws to repair defects of the orbital floor.

METHODS

An artificial standard-sized defect was created in the bony floor of right orbit of 45 albino rabbits. The animals were divided into three experimental groups: control group (G1) involving animals with orbital floor defect and no treatment; titanium group (G2) containing animals with orbital floor defect repaired by titanium miniplates and screws; vegetal polymer group (G3) composed of animals with similar orbital floor defects repaired by vegetal polymer miniplates and screws. Throughout the course of the experiment, the animals were clinically evaluated. At 15, 30 and 60 days after surgery, the animals were killed. They were X-rayed immediately after the floor defect and at the moment of sacrifice. Histological and morphometric evaluation of inflammatory reaction and bone healing was done. Data were statistically evaluated.

RESULTS

No implants were extruded. Bone consolidation was similar in G2 and G3 and better than in G1 group animals. Inflammatory reaction was most pronounced in animals of G3 15 days after surgery, and it subsided over time.

CONCLUSION

Vegetal polymer miniplates and screws induces small inflammatory reaction and had the ability to stimulate bone growth with good integration in the orbital floor defect allowing to consider the vegetal polymer adequate option to treat orbital floor defects. Future studies involving long-term follow-up and biomechanical tests to evaluate material resistance to traction are needed.

Biomaterials and implants for orbital floor repair

Treatment of orbital floor fractures and defects is often a complex issue. Repair of these injuries essentially aims to restore the continuity of the orbital floor and to provide an adequate support to the orbital content. Several materials and implants have been proposed over the years for orbital floor reconstruction, in the hope of achieving the best clinical outcome for the patient. Autografts have been traditionally considered as the "gold standard" choice due to the absence of an adverse immunological response, but they are available in limited amounts and carry the need for extra surgery. In order to overcome the drawbacks related to autografts, researchers' and surgeons' attention has been progressively attracted by alloplastic materials, which can be commercially produced and easily tailored to fit a wide range of specific clinical needs. In this review the advantages and limitations of the various biomaterials proposed and tested for orbital floor repair are critically examined and discussed. Criteria and guidelines for optimal material/implant choice, as well as future research directions, are also presented, in an attempt to understand whether an ideal biomaterial already exists or a truly functional implant will eventually materialise in the next few years.

Orbital floor reconstruction considering orbital floor slope

Orbital floor fractures are among the more challenging injuries faced by plastic surgeons. Enophthalmos is defined as backward, usually downward, displacement of the globe into the bony orbit. We describe reconstruction of the orbital floor slope in orbital floor fractures that prevents postoperative complications, especially posttraumatic enophthalmos. Thirty-three patients with orbital floor fractures were treated using reconstruction of the orbital floor slope between April 2009 and July 2010. The patients ranged in age from 12 to 54 years. There were 31 males and 2 females. All patients were operated on using a transconjunctival approach under general anesthesia. The orbital floor was reconstructed with poly-l/d-lactide sheets in all cases. Preoperatively, 23 [Float1]patients (69%) had enophthalmos, and 12 patients (36%) had symptomatic diplopia. The enophthalmos was corrected in 20 patients (86%), and the diplopia resolved in 10 (83%). Extrinsic ocular movement was impaired preoperatively in 1 patient (3%), but resolved after surgery. No patient had impaired visual acuity preoperatively or postoperatively. The results suggest that orbital floor reconstruction considering the orbital floor slope is a safe, reliable method with fewer complications that is more effective at preventing posttraumatic enophthalmos.

The efficacy of periosteal cells compared to chondrocytes in the tissue engineered repair of bone defects

We studied the efficacy of tissue generated from polymers seeded with periosteal cells and compared it to that of polymers seeded with chondrocytes, for its ability to repair surgically created cranial bone defects in rats. Large (approximately 40 mm2) bilateral defects were created in the parietal and temporal bones of 20 nude rats. One defect in each mouse was filled with synthetic biocompatible and biodegradable polymer templates seeded in vitro with either bovine periosteal cells (experimental group I) or chondrocytes (experimental group II). Contralateral defects were filled with either polymer not seeded with cells (control group I), or nothing at all (control group II). There was gross evidence of new bone formation repairing the defect in 7 of the 10 defects filled with polymers seeded with periosteal cells, while 8 of the 10 defects filled with polymers containing chondrocytes showed gross evidence of new cartilage formation covering the defect. Control defects showed no gross evidence of repair with either bone or cartilage.

The effect of a slow mode of BMP-2 delivery on the inflammatory response provoked by bone-defect-filling polymeric scaffolds

We investigated the inflammatory response to, and the osteoinductive efficacies of, four polymers (collagen, Ethisorb, PLGA and Polyactive) that bore either an adsorbed (fast-release kinetics) or a calcium-phosphate-coating-incorporated (slow-release kinetics) depot of BMP-2. Titanium-plate-supported discs of each polymer (n = 6 per group) were implanted at an ectopic (subcutaneous) ossification site in rats (n = 48). Five weeks later, they were retrieved for a histomorphometric analysis of the volumes of ectopic bone and foreign-body giant cells (a gauge of inflammatory reactivity), and the degree of polymer degradation. For each polymer, the osteoinductive efficacy of BMP-2 was higher when it was incorporated into a coating than when it was directly adsorbed onto the material. This mode of BMP-2 carriage was consistently associated with an attenuation of the inflammatory response. For coated materials, the volume density of foreign-body giant cells was inversely correlated with the volume density of bone (r(2) = 0.96), and the volume density of bone was directly proportional to the surface-area density of the polymer (r(2) = 0.97). Following coating degradation, other competitive factors, such as the biocompatibility and the biodegradability of the polymer itself, came into play.

Comparison of the supporting strength of a poly-L-lactic acid sheet and porous polyethylene (Medpor) for the reconstruction of orbital floor fractures

The aim of this study was to elucidate the supporting strength of the curved poly-L-lactic acid (PLLA) sheet and porous polyethylene (Medpor) for reconstruction of orbital floor fractures. For one-half and two-thirds orbital floor fractures, reconstruction was performed using the PLLA sheet and Medpor. The PLLA sheet was molded to fit the orbital floor (concavity). The anterior portion (1 cm) was curved to fit the inferior orbital rim and fixed with a screw. Medpor was designed to fit the orbital floor. A screw was fixed 6 mm away from the anterior border of the orbital floor. Each implant was hung by wire, and the degree of sagging of the implant was measured using micrometers by the power of a force gauge. For one-half orbital floor fractures, the power of the PLLA sheet to sag 5 mm was 2.46 (SD, 0.14) N, and that of Medpor was 0.59 (SD, 0.04) N. The power of the PLLA sheet to sag 10 mm was 6.9 (SD, 0.14) N, and that of Medpor was 1.52 (SD, 0.16) N. For two-thirds orbital floor fractures, the power of the PLLA sheet to sag 5 mm was 1.79 (SD, 0.24) N, and that of Medpor was 0.39 (SD, 0.04) N. For 10 mm of sagging, the power of the PLLA sheet was 5.61 (SD, 0.29) N, and that of Medpor was 0.94 (SD, 0.09) N. For sagging of 15 mm, the power of the PLLA sheet was 8.99 (SD, 0.16) N, and that of Medpor was 2.98 (SD, 0.24) N. The PLLA sheet was irreversibly bent when the force reached approximately 8 to 9 N. For Medpor, the degree of sagging during the early stage was larger than at the later stage. In all situations, the supporting power of the PLLA sheet was greater than that of Medpor. The differences were significant in all situations (P = 0.000). The degree of sagging in one-half orbital floor fractures was 2.87 mm for the PLLA sheet and 7.96 mm for Medpor. There was an increased orbital volume of 0.4 mL with the PLLA sheet and 1.19 mL for Medpor. The predicted enophthalmos was 0.41 mm with the PLLA sheet and 1.07 mm with Medpor. The degree of sagging for the two-thirds orbital floor fractures was 4.28 mm for the PLLA sheet and 11.47 mm for Medpor. The increased orbital volume was 0.78 mL for the PLLA sheet and 2.22 mL for Medpor. The predicted enophthalmos was 0.73 mm with the PLLA sheet and 1.93 mm with Medpor. The predicted enophthalmos was below 2 mm with both the PLLA sheet and Medpor for reconstruction of orbital floor fractures; however, it was near 2 mm with Medpor in reconstruction of two-thirds orbital floor fractures. The results of this study show that the PLLA sheet and Medpor were sufficient for reconstruction of one-half and two-thirds orbital floor fractures with a defective posterior part. However, the supporting power of the PLLA sheet was stronger than that of Medpor.

Effectiveness of a nasoseptal cartilaginous graft for repairing traumatic fractures of the inferior orbital wall

The goals of reconstruction after an orbital fracture are to restore the continuity of the floor, provide support for the orbital contents, and prevent fibrosis of the soft tissues. Nasoseptal cartilage is an easily accessible, abundant, and autogenous source that supports the orbital floor and gives minimal donor site morbidity. We evaluated the effectiveness of nasoseptal cartilage for repairing traumatic defects of the orbital floor. Autogenous nasoseptal cartilage was used in 20 patients. Presence or absence of diplopia, enophthalmos, paraesthesia of the infraorbital nerve, dystopia, range of covering of the defect by nasoseptal cartilage, complications at the recipient and donor sites, resorption of the graft, and ocular mobility disorders were recorded. Entrapment of orbital tissues, a large orbital defect (more than 50% of orbital floor or more than 8mm), or defects of the orbital floor with involvement of other fractures of the zygomaticofrontal complex are indications for exploration of the orbit. In one case after 24 months, the surgical field was explored for direct evaluation of the efficacy of the graft. All patients were treated successfully by restoration of the continuity of the orbital floor. Six months to 2 years follow up showed only one patient with postoperative enophthalmos. There was no donor site morbidity, and no grafts became infected or extruded. The nasoseptal graft was completely covered with underlying tissue. Nasoseptal cartilage is readily accessible autogenous tissue that should be considered when an autogenous graft is needed for reconstruction of a defect of the orbital floor.

Reconstruction of Traumatic Orbital Floor Fractures With Resorbable Mesh Plate

Various materials such as autogenous bone, cartilage and alloplastic implants have been used to reconstruct orbital floor fractures. A new material is needed because of disadvantages of nonresorbable alloplastic materials and difficulties in harvesting autogenous tissues. In this study safety and value of the use of resorbable mesh plate in the treatment of orbital floor fractures are discussed. Between 2002 and 2004 a total of 17 maxillofacial trauma patients complicated with orbital floor fractures were treated with resorbable mesh plate through subciliary or transconjunctival incisions. Pure blow-out fractures were determined in 6 patients and 11 patients had accompanying maxillofacial fractures. Resorbable plate was easily shaped to fit to the orbital floor by cutting with scissors. Patients were evaluated clinically and with computed tomography scans preoperatively and at 3-, 6- and 12-month intervals postoperatively. Twelve patients had preoperative enophthalmos. Two patients had diplopia that was corrected postoperatively. In all 17 cases there was no evidence of infection, diplopia and gaze restriction postoperatively. Scleral show appeared in three patients by the second postoperative week but resolved totally within 3 to 6 weeks except one patient. In this patient anterior displacement of mesh was evident which caused ectropion and enophthalmos and required re-operation. No any other mesh related problems were seen at 15 months mean follow-up time. The advantage of the resorbable mesh system in orbital floor fracture is the maintenance of orbital contents against herniation forces during the initial phase of healing and then complete resorption through natural processes after its support is no longer needed. Our experience represents that resorbable mesh is a safe and effective material for reconstruction of the selected, non-extensive orbital floor fractures.

Reconstruction of orbital wall defects with calcium phosphate cement: clinical and histological findings in a sheep model

The aim of this pilot study was to investigate the potential of calcium phosphate cement in the treatment of orbital wall defect fractures in an adult sheep model, and to compare this alloplastic material to autologous calvaria split-bone grafts. Clinical, volumetric and histological examinations were carried out of both reconstruction materials. The use of cement made intraoperative corrections easier to perform, and increased the precision of reconstruction of the orbital volume. This material also proved to be osseoconductive. The two materials were used successfully in combination. Regions of most intensive remodelling were the anterior orbital floor and the adjacent orbital rim. The preliminary results of this study demonstrate the potential of calcium phosphate cement as a useful biomaterial in the reconstruction of the anterior orbital region. Further animal and clinical trials are necessary to investigate its ability as a carrier for mediators where bone healing requires influence or support.

Use of Calcium Phosphate Cement Paste in Orbital Volume Augmentation

BACKGROUND

The development of calcium phosphate in cement paste form has made its application simplified and easy. In this study, the authors used an alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide/hydroxyapatite injectable calcium phosphate cement paste to evaluate its potential use in orbital volume augmentation.

METHODS

Five New Zealand white rabbits were used in this study. In each rabbit, the right orbit was directly implanted with calcium phosphate cement in its injectable paste form, and a prehardened form was placed in the left orbit. The orbital roof was approached through a subciliary skin incision and the implant was placed posterior to the globe of the eyeball to push it outward. Measurement of proptosis and intraocular pressure was monitored before and after implantation. The animals were killed after 3 months, and orbit bone-implant samples were taken for histology and microradiography.

RESULTS

In both groups, proptosis was induced, 4.2 +/- 0.27 mm in the prehardened group and 3.8 +/- 0.22 mm in the injectable group. These values taken 1 week postimplantation were unchanged until the end of the experiment and were maintained without significant intraocular pressure changes. The implants were well tolerated, and no sign of infection, extrusion, or migration was noted. Histologic analysis showed good biocompatibility and osteoconductivity, and microradiography has confirmed a well-set cement with direct bone union to it.

CONCLUSION

These findings therefore indicate that calcium phosphate cement implant, when used as an injectable paste or in its prehardened form, can be a safe, effective material for orbital volume augmentation.

Les matériels d'ostéosynthèse résorbables

There is continued interest in the development of new biomaterials. The application of new implantable biomaterials requires intense research and thorough evaluation. Much time and effort has been required to overcome the risks and problems associated with the bioabsorbable devices. For surgical bone fixation, these materials were investigated since the 1960's. Different polymer properties were explored to ensure adequate strength and biocompatibility. High-molecular-weight bioabsorbable polymers were initially used, followed by addition of reinforcement materials. The most recent materials are self-reinforced, small yet strong devices. The newer generations contain bioactive substances such as antibiotics and growth factors. Bioabsorbable materials are constantly changing as we try to adopt the principles of tissue engineering. Surgeons are using new techniques to exploit these polymers and their bioabsorbable properties. It is hoped that this multidisciplinary approach of surgery and research will continue to help the further evolution of biomaterial science.

Biodegradable polydioxanone and poly(l/d)lactide implants: an experimental study on peri-implant tissue response

Several implants for orbital wall fracture treatment are available at the present, but they have drawbacks: resorption, risk for migration and foreign body reaction. Alloplastic resorbable implants would be advantageous: no removal operation and no donor side morbidity. The purpose of this study was to evaluate the foreign body reaction, capsule formation and mechanical properties of two bioresorbable implants. PDS and SR-P(L/DL)LA mesh sheet (70/30) with solid frame (96/4) implants (SR-P(L/DL)LA 70,96) were placed into subcutaneous tissue of 24 rats. Immunohistochemistry was used to evaluate reactivity for Tn-C, alpha-actin, type I and III collagens and two mononuclear cells: T-cells and monocyte/ macrophage. GPC, DSC and SEM were performed. Student's t-test or nonparametric Kruskall-Wallis test were used for statistical analysis. Histology of peri-implant capsule exhibited an inner cell-rich zone and an outer connective tissue zone around both materials. Tn-C reactivity was high in the inner and alpha-actin in the outer zone. At the end of the study, the difference of type I collagen versus type III collagen reactivity in inner zone was statistically significant (P<0.0001) as was the difference of type I collagen versus type III collagen reactivity in outer zone (P<0.0001). Immunohistochemistry did not reveal any statistical differences of T-cell and monocyte/macrophage reactivity around PDS versus SR-P(L/DL)LA 70,96 implants, nor any differences as a function of time. PDS were deformed totally after 2 months. SR-P(L/DL)LA 70,96 implants were only slightly deformed during the follow up of 7 months. PDS degraded rapidly in SEM observation. Particles were detaching from surface. SEM observation revealed that polylactide implant was degrading from the surface and the inner porous core became visible. The degradation came visible at 7 months. There were cracks in perpendicular direction towards to the long axis of the filaments. M(w) of PDS decreased fast compared to the polylactide implant. Foreign body reaction was minimal to both materials but continued throughout the whole observation period. Mechanically PDS was poor, it looses its shape totally within 2 months. It cannot be recommended for orbital wall reconstruction. New mesh sheet-frame structure (SR-P(L/DL)LA 70,96) approved to be mechanically adequate for orbital wall reconstruction. It seems not to possess intrinsic memory and retains its shape. The resorption time is significantly longer compared to PDS and is comparable to other studied P(L/DL)LA copolymers. Thus, the new polylactide copolymer implant may support the orbital contents long enough to give way to bone growth over the wall defect.

Orbital Floor Reconstruction Using Calcium Phosphate Cement Paste: An Animal Study

Orbital floor defects were created in 10 New Zealand white rabbits and were reconstructed using an injectable calcium phosphate paste. These animals were euthanized at 2, 4, 8, and 12 months after implantation and were examined for biocompatibility and osteoconductivity. Grossly, implants were found to be adherent to the floor and covered with fibrous tissues. There was no sign of infection, extrusion, or migration of implant within the orbit and maxilla. The orbital floor was completely restored. Histological examination showed active new bone formation that encroached within the implant and gradually increased in density with time. Maxillary mucosa and glands were likewise reconstituted. Thin fibrovascular tissues were seen on top of and within the surface of the implant, and few to slight inflammatory cells were seen. Microradiography showed direct apposition between the new bone and the implant. These findings compare favorably with previously published reports on the biocompatibility and osteoconductivity of calcium phosphate cement. The authors believe that, together with ease of use and structural integrity, calcium phosphate paste can be useful in orbital floor reconstruction.

Biological and biophysical principles in extracorporal bone tissue engineering. Part III

Over the last decade extracorporal bone tissue engineering has moved from laboratory to clinical application. The restoration of maxillofacial bones from cell harvesting through product manufacture and end-use has benefited from innovations in the fields of biomechanical engineering, product marketing and transplant research. Cell/scaffold bone substitutes face a variety of unique clinical challenges which must be addressed. This overview summarises the recent state of the art and future anticipations in the transplantation of extracorporally fabricated bone tissues.

Orbital floor reconstruction with poly-L/D-lactide implants: clinical, radiological and immunohistochemical study in sheep

In this study the reconstruction capacity of orbital wall in sheep was evaluated when poly-L/D-lactide (PLDLA96) implants were used for large blow-out defects in 18 sheep. The contralateral side, where the defects healed spontaneously, served as controls. The follow-up was 12, 16, 22 and 36 weeks. Healing was evaluated clinically, radiologically, histologically and immunohistochemically. Physiochemical properties of the implants were also studied. At first, the implants were surrounded by elastic capsules, which gradually ossified. At 36 weeks, 60% were still visible and deformed but surrounded by bone. Light microscopy revealed a low grade inflammatory reaction. Expression of Tn-c and cFn was intense throughout the study. Shear strength decreased gradually and was not measurable after 16 weeks. Crystallinity increased steadily from 1.5 to 29.30% and molecular weight decreased from 49,000 to 4186. In CT, the final bony defect was smaller in the reconstructed sides than in the controls. Based on this study it can be concluded that PLDLA96 implant provokes a local inflammation, which does not prevent bone healing. The deformation of the implant, however, indicates that this PLDLA96 plate is not suitable for orbital floor reconstruction.

Reconstruction of Orbital Floor Fracture Using Solvent-Preserved Bone Graft

The orbital floor is one of the most frequently damaged parts of the maxillofacial skeleton during facial trauma. Unfavorable aesthetic and functional outcomes are frequent when it is treated inadequately. The treatment consists of spanning the floor defect with a material that can provide structural support and restore the orbital volume. This material should also be biocompatible with the surrounding tissues and easily reshaped to fit the orbital floor. Although various autografts or synthetic materials have been used, there is still no consensus on the ideal reconstruction method of orbital floor defects. This study evaluated the applicability of solvent-preserved cadaveric cranial bone graft and its preliminary results in the reconstruction of the orbital floor fractures. Twenty-five orbital floor fractures of 21 patients who underwent surgical repair with cadaveric bone graft during a 2-year period were included in this study. Pure blowout fractures were determined in nine patients, whereas 12 patients had other accompanying maxillofacial fractures. Of the 21 patients, 14 had clinically evident diplopia (66.7 percent), 12 of them had enophthalmos (57.1 percent), and two of them had gaze restriction preoperatively. Reconstruction of the floor of the orbit was performed following either the subciliary or the transconjunctival approach. A cranial allograft was placed over the defect after sufficient exposure. The mean follow-up period was 9 months. Postoperative diplopia, enophthalmos, eye motility, cosmetic appearance, and complications were documented. None of the patients had any evidence of diplopia, limited eye movement, inflammatory reactions in soft tissues, infection, or graft extrusion in the postoperative period. Providing sufficient orbital volume, no graft resorption was detected in computed tomography scan controls. None of the implants required removal for any reason. Enophthalmos was seen in one patient, and temporary scleral show lasting up to 3 to 6 weeks was detected in another three patients. Satisfactory cosmetic results were obtained in all patients. This study showed that solvent-preserved bone, which is a nonsynthetic, human-originated, processed bioimplant, can be safely used in orbital floor repair and can be considered as another reliable treatment alternative.

In vivo efficacy of bone-marrow-coated polycaprolactone scaffolds for the reconstruction of orbital defects in the pig

Alloplastic materials offer a number of advantages over bone autografts in the reconstruction of craniofacial defects. These include: lack of donor site morbidity, unlimited quantities of available material, and the possibility to conform exactly to the defect. An ideal bioresorbable material would degrade slowly, and have osteoconductive properties to allow replacement and remodeling by osseous tissue. This is seldom observed, the materials instead being replaced by fibrous tissue. Polycaprolactone (PCL), an FDA-approved bioresorbable polymer, has several properties that might make it suitable for reconstruction of craniofacial defects. The technique of fused deposition modeling (FDM) allows for the fabrication of highly reproducible bioresorbable 3D scaffolds. The nature of the fully interconnected pore network might enhance vascular ingrowth and osteoconductive properties. It was hypothesized that coating the scaffolds in bone marrow might enhance bone formation due to the osteoinductive nature of the bone-marrow mesenchymal cells. This study aimed to test these hypotheses in the pig model. Defects measuring 2 x 2 cm were surgically created in each orbit of eight Yorkshire pigs. The orbits were divided into three groups: Group 1 (n=4), no reconstruction (control); Group 2 (n=6), reconstruction with no coated PCL scaffolds; and Group 3 (n=6) reconstruction with bone-marrow-coated PCL scaffolds. The results were evaluated at 3 months by histological and histomorphometric analyses. The defects in Group 1 were covered with fibrous scar tissue. The shape of the reconstructed area was insufficient. The defects in Groups 2 and 3 were reconstructed correctly. In Group 2 the noncoated scaffolds showed 4.5% of new bone formation compared with 14.1% in Group 3, which is statistically significant (p<0.05). The entirely interconnected 3D polycaprolactone scaffold seems to be a promising material. It induces the bone ingrowth required for reconstructing craniofacial and orbital defects. Further long-term evaluations of these PCL scaffolds must be made in order to confirm these conclusions.

Spotlight on naturally absorbable osteofixation devices

The practice of using implants is growing day by day, and more foreign materials are being inserted for various indications. The field of implantology thus deserves intensive research and careful evaluation of results. Solutions to overcome current problems and risks are necessary. It has taken a long time to arrive at where we are now. Bioabsorbable devices were explored in the 1960s for surgical bone fixation. Failures were followed by changes in ways of thinking and innovations. Improvements in the strength properties and biocompatibility were achieved. Bioabsorbable polymeric materials such as high-molecular-weight polymers were used and also reinforced with other material or, more recently, by self-reinforcement to produce small yet strong devices. New generations of implants include those that contain bioactive substances such as antibiotics and growth factors. Developments in bioabsorbable materials continue to accommodate the new way of thinking brought about by the emergence of the field of tissue engineering. Surgeons, conversely, are also inventing new surgical techniques and methods to exploit the plastic and bioabsorbability properties of these materials for the better future of our patients. Such a multidisciplinary approach that involves surgeons and materials scientists should help to find solutions to the current limitations of these devices.

Orbital floor reconstruction with flexible Ethisorb patches: a retrospective long-term follow-up study

OBJECTIVE

The purpose of the study was to investigate whether a flexible, biodegradable material (Ethisorb) shows better long-term results with regard to diplopia, bulbus motility, and exophthalmos/enophthalmos compared to the use of lyophilized dura-patches and polydioxanone (PDS) foils.

METHODS

During a period of 6 years 435 patients with an orbital fracture were investigated retrospectively. Inclusion criteria were patients with fractures of the orbital floor with a maximum size of 2 x 2 cm. Bulbus motility, exophthalmos, enophthalmos, and diplopia were investigated during a period of 2 years.

RESULTS

One hundred twenty orbital floors were reconstructed by lyophilized dura-patches, 81 by PDS, and 136 by Ethisorb. An exploration without an implantation was performed in 91 patients. The long-term investigation 12 to 15 months after surgery showed an exophthalmos and enophthalmos incidence of 1%, whereas a reduced bulbus motility and diplopia were found in 5% and 4%, respectively. Fifteen to 24 months after surgery 2% of the patients had an exophthalmos and 1% had an enophthalmos. A reduction of bulbus motility was found in 4% of the patients, and diplopia was found in 3%. The use of Ethisorb resulted in a significantly lower incidence of exophthalmos 3 months after surgery compared to PDS.

CONCLUSION

The low rate of acquired bulbus motility demonstrates acceptable results in using Ethisorb in the floor of the orbit.

Transmission electron microscopic visualization of the degradation and phagocytosis of a poly-L-lactide screw in cancellous bone: a long-term experimental study

The increasing clinical use of biodegradable implants in orthopedic surgery makes it necessary to determine their long-term behavior in tissues. In this study, a biodegradable screw made of poly-L-lactide (PLLA) was inserted axially into the right distal femur in 18 rabbits. The degradation and phagocytosis process of PLLA was assessed histologically and by transmission electron microscopy (TEM). The follow-up times were 3 and 4.5 years for groups of nine and eight animals, respectively. Abundant birefringent polymeric material was still present in the center of the implant channel in all specimens in both follow-up groups. The PLLA material studied appeared to be a biologically relatively inert material, with only sparse reactive cellular activity at the tissue-implant boundary. In the TEM specimens, polymeric particles of an average area of 2 microm2 were seen to be located intracellularly within phagocytic cells. The spheric and polygonal particles were membrane-bound and to a great extent filled up each phagocyte. In the 4.5-year specimens, the size of the polymeric particles, measured as area and perimeter, was significantly smaller (p < 0.02) than that of the 3-year specimens. The findings indicate that the ultimate degradation process of PLLA is much longer than it previously was thought to be. Complete degradation probably still would have taken years after the 4.5-year span of this study.

Influence of bioresorbable, unsintered hydroxyapatite/poly-L-lactide composite films on spinal cord, nerve roots, and epidural space

The effect of forged unsintered hydroxyapatite/poly-L-lactide (u-HA/PLLA) composite films on spinal cord and nerve roots and its degradation behavior and osteoconductivity in epidural space were compared with those of calcined HA (c-HA)/PLLA and unfilled PLLA films. Partial laminectomy was performed on 20 rabbits, and u-HA/PLLA and PLLA films were implanted in the intervertebral space. Total laminectomy was performed on 30 rabbits to implant u-HA/PLLA, c-HA/PLLA, and PLLA films in both epidural and subcutaneous spaces. For up to 50 weeks, there were no histological changes in the spinal cord or nerve root, and no inflammatory cell infiltration into the epidural space around the films. The rate of decrease in viscosity average molecular weight of both composite films was initially higher than that of PLLA but eventually became lower, although there was no difference in the degradation behavior of the three films in either the epidural or subcutaneous spaces after 50 weeks. Scanning electron microscopic and energy-dispersive X-ray analysis indicated calcium phosphate deposits on the surface of composite films with new bone formation from 4 weeks. The u-HA/PLLA composite film therefore has good biocompatibility, osteoconductivity, and fast primary degradation rate, which may prove compatible with application to spinal surgery.

A comparison of parietal and iliac crest bone grafts for orbital reconstruction

PURPOSE

This study evaluated the results of cranial (membranous) versus iliac crest (endochondral) bone grafts as implants to correct post-traumatic globe malposition and/or diplopia.

PATIENTS AND METHODS

Twenty-two patients underwent 25 orbital reconstructions with bone for enophthalmos, hypophthalmos, and diplopia after trauma to the orbit. Inclusion criteria consisted of at least 4 months postsurgical follow-up, pre- and postsurgical quantitative orbital measurements, photographic documentation, and complete medical records regarding inpatient and outpatient data.

RESULTS

Nine cranial bone grafts and 16 iliac crest grafts were placed. Ages were similar in both groups. The average follow-up was 24 months for the cranial graft group (range, 4 to 54 months) and 18 months for the iliac crest graft group (range, 4 to 51 months). Preoperative enophthalmos averaged 4.11 and 5.06 mm in the cranial and iliac crest groups, respectively, and postoperatively the measurements were 1.78 and 1.37 mm, respectively. Changes in hypophthalmos generally reflected changes in the enophthalmos correction. In 10 patients diplopia was corrected by the procedure. There was a statistically significant change in the enophthalmos of patients when comparing pre- and postoperative status, but no statistically significant difference between the results of the cranial and iliac crest graft groups.

CONCLUSION

There is no difference in the ability of cranial and iliac crest bone grafts to correct post-traumatic enophthalmos.

Repair of traumatic inferior orbital wall defects with nasoseptal cartilage

PURPOSE

This study evaluated the effectiveness of nasoseptal cartilage for repairing traumatic orbital floor defects.

PATIENTS AND METHODS

Autogenous septal cartilage was used in 20 patients. They were evaluated for the presence or absence of diplopia, enophthalmus, infraorbital nerve paresthesia, and ocular motility disorders. Surgical indications for orbital exploration included entrapment of orbital tissues, large orbital defect (greater than 50% of the orbital floor or more than 8 mm), or orbital floor defects with involvement of other zygomaticofrontal complex fractures.

RESULTS

All patients were successfully treated by restoration of the orbital wall continuity. Follow-up at 1 week to 6 months showed 1 patient with postoperative enophthalmos and 1 patient with lower lid edema. There were no donor site and graft infections or graft extrusion.

CONCLUSIONS

Nasal septal cartilage is a readily accessible autogenous tissue that should be considered when an autogenous graft is needed for orbital floor defect reconstruction.

Degradation of poly(D,L)lactide implants with or without addition of calciumphosphates in vivo

The study was aimed at examining the in vivo degradation of pure poly(D,L)lactide (PDLLA) or PDLLA with an admixture of calciumphosphates. One rod (20 x 3 x 2 mm) and one cube (3 x 2 x 2 mm) of pure PDLLA, PDLLA with tricalciumphosphate (PDLLA + TCP) or PDLLA with calciumhydrogenphosphate (PDLLA + CHP), respectively, were implanted into the dorsal muscles of 50 male Wistar Albino rats. After definite intervals (from 2nd to 72nd week), pH measurements were performed in the environment of the implants. Afterwards, the cubes with their surrounding tissues were excised for histological examinations, measurements of the outer dimensions and mechanical analyses of the explanted rods were performed. No drop of more than 0.1 pH units was detectable in the tissue surrounding any type of implants. No advantageous effect of the calciumphosphates could be proved. A mild foreign body reaction could be observed around PDLLA implants. After 72 weeks, pure PDLLA had been totally resorbed from the extracellular space, the degradation of calciumphosphate-enriched PDLLA was still in progress. A large amount of inflammations occurred in the tissues surrounding PDLLA with an admixture of slowly degrading TCP or CHP, leading to two abscesses and four fistulas at PDLLA + TCP, and two abscesses and three fistulas at PDLLA + CHP implantation site. Bending strength of pure PDLLA was constant up to the 4th week post-implantation and reduced to 60% of the initial value up to the 12th week. No traces of crystallinity could be observed during the degradation of PDLLA. As a conclusion of the study, complete resorption from the extracellular space and tissue tolerance of pure PDLLA is proved. An admixture of small calciumphosphate particles is not suitable to improve the biocompatibility of PDLLA but leads to a decrease in the mechanical characteristics.

Use of self-reinforced polylactide osteosynthesis devices in craniofacial surgery: a long-term follow-up study

Self-reinforced polylactic acid or polylactide (SR-PLA) is a biodegradable polymer, which is strong enough to fix weight-bearing cortical bone fractures and osteotomies. We report our experience and follow-up of the use of SR-PLA plates in 15 clinical cranioplasties. Two of the cases are described in greater detail. In one of them SR-PLA plates were used in addition to titanium plates, and in the other an SR-PLA plate fixed with mini-titanium screws was used as the only fixation material. In the other patients SR-PLA plates or wire were used in addition to titanium. So far no complications have been observed in these 15 patients. The only small superficial fistula was associated with a titanium plate and titanium screws. The longest follow-up has been over eight years. Recent results show metal-like deformation properties in addition to complete late resorption, making SR-PLA osteosynthesis devices promising for use in craniofacial surgery.

Cranial reossification with absorbable plates

The purpose of this study was to examine the effect of Lactosorb absorbable plates on bone healing across cranial bone defects in the rabbit skull. Two 10-mm diameter parietal skull defects were created in each of 20 rabbits, with one defect being placed on either side of the sagittal suture. In 10 rabbits, an absorbable plate was placed across both the inner and outer cortices of the left defect, and in the other 10 rabbits, an absorbable plate was placed across the outer cortex only of the left defect. The right defect always served as the control side, with no plate being placed across it. Rabbits were killed an average of 25 weeks postoperatively. Areas of reossification in the experimental and control defects of each rabbit were then measured, examined histologically, and compared. Growth across defects spanned by one plate was also compared with growth across defects spanned by two plates. Histologic and statistical analyses revealed no significant differences in reossification between the control and experimental defects in each animal and between the defects spanned by one versus two plates. This study suggests that these copolymer absorbable plates neither inhibit nor facilitate reossification across 10-mm diameter rabbit cranial defects.

Use of membrane and bone grafts in the reconstruction of orbital fractures

OBJECTIVE

To present and analyze the clinical results derived from the use of different grafts for the reconstruction of orbital defects during a 10-year period.

STUDY DESIGN

Fifty-five fracture cases with orbital bony defect, requiring a graft, are presented. The surgical treatment includes the reconstruction of the fracture (osteosynthesis) and the repair of the remaining bone defect by graft, with the type of graft dependent on the size of the defect. For minor defects membranes were used (lyophilized dura or alloplastic dura mater), whereas major defects were repaired with bone grafts (autografts, heterografts, or bone substitute material). All patients have been regularly evaluated for at least one year postoperatively.

RESULTS

All grafts were well tolerated by the patients. Diplopia subsided in all but 5 cases, motility disturbance was fully repaired in all but 3 cases. Esthetics were improved in cases with severe bone defect.

CONCLUSION

The wide variety of grafts available allows successful reconstruction of all types of orbital bony defects. The clinician should be able to use different types of grafts depending on the type and size of the defect.

The efficacy of bioresorbable fixation in the repair of mandibular fractures: an animal study

PURPOSE

The efficacy of bioresorbable fixation has recently been described in the treatment of cranial vault deformities and in midfacial trauma. However, little to no data exist regarding its use in load-bearing areas. The purpose of this study is to analyze and compare the treatment of mandibular fractures by using a bioresorbable fixation system with a conventional titanium system in a canine model.

MATERIALS AND METHODS

Four adult beagles constituted the experimental group (A), and 2 beagles constituted the control group (B). Both groups underwent extraoral iatrogenic left mandibular angle osteotomies/fractures and open reduction and internal fixation by use of a bioresorbable fixation system (A) or a titanium fixation system (B). All operated animals were allowed to function immediately. Lateral skull radiographs were obtained preoperatively, immediately postoperatively after reduction, and at 3- and 6-month intervals. Preoperative and 6-month follow-up bite registrations were taken. At the 3-month interval, 1 animal from the experimental group was killed, and at 6 months the remaining animals were killed for morphologic, radiographic, and histologic analysis of the fractured interface and screw sites.

RESULTS

Morphologically, in the bioresorbable group, there was no clinical evidence of 1) intraoral/ extraoral incisional dehiscence of wound infection; 2) deviation of the occlusion from maximum intercuspation; 3) intraoral/extraoral palpability of the device; 4) mobility of the fractured segments on manual manipulation; or 5) malunion as visualized at the time of sacrifice. All bioresorbable plates were clinically absent after 6 months and associated with adequate fixation and healing. Adequate restoration of function was achieved in both groups, with all of the animals showing weight gain. Radiographically, good alignment of the inferior border was seen, and histologically bony union was apparent in all specimens.

CONCLUSIONS

This bioresorbable fixation system is effective in the treatment of mandibular angle fractures in a dog model, despite being placed in a load-bearing region.

The science of tissue engineering

This article reviews the development of tissue engineering during the last decade. The science began to fully develop in association with efforts to combine viable cells with biocompatible material. The history and scope of this new field are presented. Basic principles of cell biology, materials, and technologies are discussed. Future challenges in the field are presented.

An overview of tissue engineered bone

Numerous important developments in tissue engineering of new bone during the last 10 years are reviewed. Early efforts to combine cells with biocompatible materials are described and applications of this technology are presented with particular focus on uses in orthopaedics and maxillofacial surgery. Basic principles of tissue engineering focusing on cell biology and materials science as used currently in the field are presented. Finally, future challenges are outlined from the perspective of integrating technologies from medicine, biology, and engineering in hopes of translating tissue engineering to clinical applications.

An evaluation of the support provided by common internal orbital reconstruction materials

PURPOSE

The objectives of this investigation were to assess the weight of the combined internal orbital contents, to evaluate the ability of common internal orbital reconstruction materials to resist loads, and to determine whether these materials provide enough load resistance to support the orbital contents.

MATERIALS AND METHODS

The combined exonerated internal orbital contents (globe, fat, extraocular musculature, neurovascular structures, lacrimal apparatus, and musculocutaneous lids) from 16 human orbits were weighed. Five each of 13 different internal orbital reconstruction materials (titanium mesh, bioresorbables, Marlex [CR Bard, Cranston, RI], Medpore [Porex Medical, College Park, GA], Silastic [Dow Coming, Midland, MI], dried calvarium) were evaluated for their ability to resist loads applied by Instron 85.11 mechanical testing device (Canton, MA) when used to reconstruct uniform orbital floor defects in synthetic skulls (Sawbones, Vashon Island, WA). Yield load, yield displacement, maximum load, and displacement at maximum load were measured. A comparison was then made between orbital content weight and the load-resisting capabilities of the various materials.

RESULTS

The weight of the combined internal orbital contents was 42.97+/-4.05 g (range, 37.80 to 51.03 g). All of the materials tested except Marlex mesh met or exceeded the requirements for support of the combined internal orbital contents.

CONCLUSION

Except in the instance of complete loss of the orbital floor, all of the materials tested should provide adequate orbital support.

Host response to tissue engineered devices

The two main components of a tissue engineered device are the transplanted cells and the biomaterial, creating a device for the restoration or modification of tissue or organ function. The implantation of polymer/cell constructs combines concepts of biomaterials and cell transplantation. The interconnections between the host responses to the biomaterial and transplanted cells determines the biocompatibility of the device. This review describes the inflammatory response to the biomaterial component and immune response towards transplanted cells. Emphasis is on how the presence of the transplanted cell construct affects the host response. The inflammatory response towards a biomaterial can impact the immune response towards transplanted cells and vice versa. Immune rejection is the most important host response towards the cellular component of tissue engineered devices containing allogeneic, xenogeneic or immunogenic ex vivo manipulated autologous cells. The immune mechanisms towards allografts and xenografts are outlined to provide a basis for the mechanistic hypotheses of the immune response towards encapsulated cells, with antigen shedding and the indirect pathway of antigen presentation predominating. A review of experimental evidence illustrates examples of the inflammatory response towards biodegradable polymer scaffold materials, examples of devices appropriately integrated as assessed morphologically with the host for various applications including bone, nerve, and skin regeneration, and of the immune response towards encapsulated allogeneic and xenogeneic cells.