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

Repair of orbital blow-out fractures with nasoseptal cartilage

The goals of reconstruction in orbital blow-out fractures are to restore floor continuity, provide support of orbital contents, and prevent fibrosis of soft tissues. Although ease of use has popularized alloplasts, autogenous material provides greater biocompatibility and results in low rates of infection, extrusion, and migration. Nasoseptal cartilage is an easily accessible, abundant, autogenous source that provides support to the orbital floor and minimal donor site morbidity. Thirteen patients who presented with orbital blow-out fractures underwent reconstruction with nasoseptal cartilage. Follow-up at 3 months to 4 years shows one patient with persistent manifest enophthalmos requiring further augmentation. There were no recipient or donor site complications. Nasoseptal cartilage is an underutilized and superior material for reconstruction of orbital blow-out fractures.

Lactosorb panel and screws for repair of large orbital floor defects

In a series of five patients with extensive fractures of the orbital floor, we used a biodegradable sheet for bridging of the bony defects. To achieve optimal support of the orbital contents in their anatomically correct position, we fixed the sheet with at least two resorbable screws to the infraorbital rim. This new technique appears to be superior to conventional methods because it offers reproducible results without the need for secondary interventions.

Repair of traumatic orbital wall defects with nasal septal cartilage: report of five cases

PURPOSE

This article reports the use of nasal septal cartilage for the repair of traumatic orbital wall defects.

PATIENTS AND METHODS

Five patients with disruption of the orbital wall after facial trauma were included in this retrospective review. All of the patients underwent open reduction with internal fixation of the fractures as well as repair of the orbital wall defect with autogenous septal cartilage.

RESULTS

Nasal septal cartilage was used in four cases of orbital floor defect and one case of orbital roof defect. All of the cases were successfully treated by restoration of the orbital wall continuity.

CONCLUSION

Nasal septal cartilage is a readily accessible autogenous material that can be easily harvested with minimal donor site morbidity, and it should be considered when an autogenous orbital implant is needed for the repair of a traumatic orbital wall defect.

Effects of implantable biomaterials on radiation dosimetry

BACKGROUND

It is generally known that radiation dose is enhanced in front of and reduced behind metallic plates. This study evaluates metallic, ceramic, and bioabsorbable facial-reconstruction materials for their differential effects on radiation dosimetry.

METHODS

Commercially pure titanium (cpt), stainless steel (steel), titanium alloy (tia), hydroxyapatite (HA), and poly-L-lactide (PLA, a bioabsorbable polymer) were obtained for this study. The radiation doses distal (behind) and proximal (in front of) to the test material were measured with an ionization chamber placed at several distances from the test material. Therefore, transmission (proximal to plate) and backscattering (distal to plate) factors were generated at several distances for each material.

RESULTS

Poly-L-lactide transmitted nearly 100% of the incident radiation beam. The metals had the greatest effect on transmission with steel, followed by cpt, tia, and HA showing the greatest reduction of incident beam. Poly-L-lactide revealed minimal backscattering. Greater backscatter of the incident radiation beam was seen from steel, followed by cpt and HA. Poly-L-lactide also behaved similar to water in transmission and backscatters properties during electron irradiation.

CONCLUSIONS

Poly-L-lactide has a minimal effect on the radiation-dose distribution and may be beneficial as a reconstructive device for patients undergoing head and neck cancer radiotherapy. Hydroxyapatite showed a relatively minor effect, whereas the metals (steel, followed by cpt and tia) revealed the greatest detrimental effect on the radiation-dose distribution.

Reconstruction of the orbital floor with lyophilized tensor fascia lata

PURPOSE

This article describes the results of using lyophilized tensor fascia lata for the repair of orbital floor defects.

PATIENTS AND METHODS

During a 2-year period, orbital floor reconstruction was performed in 12 patients using lyophilized tensor fascia lata. A Foley catheter was placed into maxillary sinus and left in place for 10 days to provide temporary support for the fascia.

RESULTS

Patients were followed for 12 months to 2 years. No cases of infection, exposure, extrusion, or graft removal were encountered, and enophthalmus, symmetry changes, or restricted movement were not observed during the follow-up period.

CONCLUSION

Lyophilized fascia lata is easy to shape and place in the defect. It provides an excellent material for repair of small to moderate-sized orbital floor defects.

Intraosseous plating with absorbable self-reinforced poly-L-lactide plates in the fixation of distal femoral osteotomies on rabbits

Osteotomies of distal femur were fixed by intraosseous self-reinforced poly-L-lactic acid (SR-PLLA) plates in 29 adult rabbits. The follow-up times were from 3 to 24 weeks. After sacrifice, radiological, histological, microradiographic, and oxytetracycline fluorescence studies were performed. Although radiographically no redisplacements were found, in 12 weeks two fixations were broken and a fibrotic nonunion was observed in one case. At 24 weeks full bone consolidation was seen in all except one osteotomy. No foreign-body reactions were observed. The present article is the first report on successful application of absorbable plates for intraosseous fixation of weight-bearing bone osteotomies. The present investigation demonstrated that the SR-PLLA plates were suitable for the fixation of cancellous bone osteotomies in rabbits.

Poly(L-lactide) implants for repair of human orbital floor defects: clinical and magnetic resonance imaging evaluation of long-term results

PURPOSE

The purpose of this study was to evaluate the long-term outcome of repair of orbital floor defects in patients with resorbable as-polymerized poly(L-lactide) (PLLA) implants and to determine whether these patients showed symptoms that could be indicative of the presence of a late tissue response.

PATIENTS AND METHODS

Six patients (four women, two men; mean age, 39 years; range, 18 to 67 years) treated with PLLA implants for orbital floor fractures were recalled for follow-up examination after a period ranging from 3 1/2 to 6 1/2 years. The examination consisted of an interview and a physical examination, including an ophthalmologic and orthoptic consultation. For evaluation of the orbital tissues, coronal spin echo T1- and T2-weighted magnetic resonance images (MRIs) were made through both orbits.

RESULTS

None of the patients reported any problems in the years preceding the follow-up examination that might have indicated complications. Clinical examination of the operative sites revealed no abnormalities. At ophthalmologic and orthoptic consultation, normal eye function, without diplopia or restriction of motility, was found in all patients. The MRIs showed no indication of an abnormal or increased soft tissue reaction in the orbital region.

CONCLUSIONS

Based on the results of this study, it can be concluded that PLLA orbital floor implants have the potential for successful use in repair of human orbital floor defects.

Repair of critical size rat calvarial defects using extracellular matrix protein gels

In this study the authors examined the capacity of gels of reconstituted basement membrane, laminin, and type I collagen to mediate repair of critical size defects in rat calvaria. Although autografts are widely used to repair bone defects caused by trauma or surgical treatment of congenital malformations, neoplasms, and infections, an adequate quantity of graft is not always available. Allogenic bone is readily available, but its use is associated with an increased incidence of nonunion, fatigue fracture, and rejection. Biologically active, purified components of basement membranes, which have been shown to promote osteogenic differentiation and angiogenesis in vitro and type I collagen (the major constituent of bone extracellular matrix) can be formed into native isotonic space-filling gels. In this study critical size calvarial defects were created in retired male Sprague-Dawley rats. Thirty-six animals were divided into seven groups. Group 1 (control) received no treatment for the defects. Group 2 animals were implanted with methylcellulose. Groups 3, 4, 5, and 6 were implanted with gels of type I collagen, reconstituted basement membrane, or laminin, respectively. The last group of three animals (Group 7) was implanted with 100 micrograms of type I collagen gels (identical to Group 3) and sacrificed at 20 weeks following a single CT scan to determine if complete healing could be obtained with this method given sufficient time. Except for rats in the type I collagen group that was evaluated by multiple computerized tomography (CT) scans biweekly from 2 to 12 weeks, bone repair was evaluated using CT at 12 weeks. Healing was quantified using three-dimensional reconstruction of CT. Following the final CT scan in each experimental group, animals were sacrificed, and a sample of tissues was evaluated by conventional histology. Animals treated with type I collagen gels showed 87.5% repair of the area of the defects at 12 weeks and 92.5% repair by 20 weeks. Increasing the gel volume 1.5 x accelerated complete repair to 3 months. Murine-reconstituted basement membrane and laminin gels induced 55.5% and 46.3% repair, respectively, at 3 months. In untreated control animals 7% repair of the area of the defects showed at 3 months. Histological analysis confirmed new bone formation in partial and completely healed defects. Bioengineered native collagen gels may have wide applicability for bone repair as an alternative bone graft material alone, in combination with autograft or marrow aspirate, or as a delivery system for osteogenic growth factors.

Self-reinforced polyglycolic acid membrane: a bioresorbable material for orbital floor repair. Initial clinical report

A self-reinforced polyglycolic acid membrane has been used successfully to repair 15 orbital floor fractures in 12 consecutive patients. As polyglycolic acid is absorbable it does not cause the complications of long-term infection and migration associated with non-absorbable bioinert alloplastic repair materials.

In vivo degradation and biocompatibility study of in vitro pre-degraded as-polymerized polyactide particles

The degradation of high molecular weight as-polymerized poly(L-lactide) (PLLA) is very slow; it takes more than 5.6 yr for total resorption. Moreover, the degradation products of as-polymerized PLLA bone plates, consisting of numerous stable particles of high crystallinity, are related with a subcutaneous swelling in patients 3 yr postoperatively. In order to avoid these complications, polymers were developed that are anticipated to have comparable mechanical properties but a higher degradation rate and do not degrade into highly stable particles that can induce a subcutaneous swelling. On chemical grounds it can be expected that copolymerization of PLLA with 4% D-lactide (PLA96) or by modifying PLLA through cross-linking (CL-PLLA) will lead to less stable particles and a higher degradation rate. To evaluate the long-term suitability of these as-polymerized polymers, the biocompatibility of the degradation products should be studied. Considering the very slow degradation rate of as-polymerized PLLA, in vitro pre-degradation at elevated temperatures was used to shorten the in vivo follow-up periods. In this study, the biocompatibility and degradation of as-polymerized PLLA, PLA96 and CL-PLLA were investigated by implanting pre-degraded particulate materials subcutaneously in rats. Animals were killed after a postoperative period varying from 3 to 80 wk. Light and electron microscopical analysis and quantitative measurements were performed. The histological response of all three pre-degraded materials showed a good similarity with in vivo implanted material. Pre-degraded PLLA induced a mild foreign body reaction and showed a slow degradation rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Biocompatibility study of as-polymerized poly(L-lactide) in rats using a cage implant system

To evaluate the biocompatibility of in vitro predegraded as polymerized poly(L-lactide) (PLLA), a cage implant system was used to investigate white cell and enzyme concentrations with time. The use of a cage permits in a serial fashion a quantitative and qualitative measurement of exudate components formed around an implant. Subcutaneously in rats, caped cages manufactured from stainless-steel mesh were implanted with in vitro predegraded, as-polymerized PLLA, as-polymerized PLLA cylinders, and empty cages serving as controls. In vitro predegradation was used to simulate the degradation products of long-term in vitro degradation. Predegraded PLLA particles were obtained by in vitro hydrolysis at elevated temperatures. The first 7 days of implantation were characterized by an acute inflammatory reaction; the exudate extracted from the cages showed predominantly neutrophils for all types of implants. After day 7, there was a more chronic inflammatory reaction with predominantly macrophages and lymphocytes. There were no significant differences in the total leukocyte concentration or macrophage concentration for any of the cages in the period from 10-21 days. Extracellular enzyme activity also did not show any significant differences among the three types of cages. A possible explanation for the absence of any significant differences could be that the in vitro predegraded particles were sieved before implantation, thus eliminating all small particles (< 70 microns) that are probably mandatory to provoke an increased cellular reaction.

Influence of three alloplastic materials on calvarial bone healing. An experimental evaluation of HTR-polymer, lactomer beads, and a carrier gel

This study evaluated experimentally three alloplastic materials (HTR-polymer, lactomer beads, and a resorbable gel substance). A bioassay performed in a critical size defect rat model disclosed no osteoinductive capacity of any material. A total of 72 trephine calvarial 5-mm defects were created in 18 rabbits. The inlays were tested relative to control (empty) defects in a varied pattern, and the results were assessed by light microscopy and contact radiography after 4 and 15 weeks. The HTR-polymer alone or combined with bone chips displayed the most rapid early bone regeneration and more mature bone marrow redevelopment. The present form of the gel material seems to be less suitable for use as a carrier substance because of the intense inflammatory response produced.

Polylactide screws in the fixation of olecranon osteotomies. A mechanical study in sheep

We studied absorbable self-reinforced poly-L-lactide screws in the fixation of osteotomies in sheep. A left olecranon osteotomy in 10 sheep was fixed with polylactide screws and in an additional 10 sheep with metallic AO cortical screws. Follow-up times were 6 and 12 weeks. 8 polylactide fixations healed and 2 failed. All metal fixations united; one of them had a fracture of the proximal fragment resulting in malposition. After killing the sheep the olecranons were radiographed and the shear strengths of the osteotomies were compared with those of the non-operated contralateral bones. After 6 weeks the mean comparative strength was 74 percent in the polylactide group and 83 percent in the metallic control group. After 12 weeks the corresponding values were 112 and 47 percent (P less than 0.05). Our study demonstrated that the mechanical weakening of fixed bone can be avoided by using absorbable polylactide screws instead of metallic screws. However, polylactide screws are not recommended for use without external support in places of high mechanical strain.

Comparison of absorbable self-reinforced multilayer poly-l-lactide and metallic plates for the fixation of mandibular body osteotomies: an experimental study in sheep

Eighteen unfavorable transverse osteotomies were created in the mandibular body of sheep. Nine were fixed with self-reinforced poly-l-lactide and nine with metallic dynamic compression plates. Both plates were fixed with similar titanium screws. The follow-up times for radiographic, histologic, and microradiographic studies were 6, 12, and 24 weeks. With both methods, bony union with callus formation was accomplished by 6 weeks in all but one osteotomy in the metallic fixation group. There were no signs of plate failure.