Scleral Grafts in Ophthalmic Surgery. A Review.

AIM: To summarize the history and current trends in the use of scleral grafts in ophthalmology. MATERIALS AND METHODS: We conducted a review of the literature through the MEDLINE and Cochrane Library databases. The search terms were "sclera", "graft", and "surgery". The search resulted in 1596 articles, of which we evaluated 192 as relevant. The relevant articles were sorted chronologically and according to the method of using scleral grafts, which enabled the development of a review article. RESULTS: The sclera has been routinely used in ophthalmology since the 1950s in many different indications. Some of these indications have become practically obsolete over time (for example, use in the surgical management of retinal detachment), but a large number still find application today (especially use in glaucoma or oculoplastic surgery, or as a patch for a defect in the sclera or cornea). CONCLUSION: Even though allogeneic sclera is currently used less frequently in ophthalmology compared to other tissue banking products and the range of its indications has partially narrowed, it remains a useful material due to its availability and properties.

Giant anterior scleral staphyloma caused by blunt ocular trauma: a case report.

BACKGROUND: Anterior scleral staphyloma is a relatively rare disease characterized by thinning and expansion of sclera. We described the clinical presentation, diagnosis and treatment of a case with giant anterior scleral staphyloma caused by blunt ocular trauma. CASE PRESENTATION: A 24-years-old male, presented with a black cyst-like mass protruding from the right eyeball for 9 years after a history of glass crush contusion. The ultrasound biomicroscopy examination showed two cysts in the right eyeball. The larger one was about 5.92 mm*4.69 mm in size and the scleral lacerations were connected to the posterior chamber below the cyst. For treatment, resection of the anterior scleral staphyloma and the scleral patch graft transplantation was performed. The vision of the patient was improved compared with that before surgery. There were no obvious complications. CONCLUSION: The clinical presentation, diagnosis, and treatment of the case with giant anterior scleral staphyloma can provide a reference for the management of anterior scleral staphyloma. Surgical resection and scleral patch graft should be a good option for the treatment of giant anterior scleral staphyloma.

Acute-onset surgically induced necrotizing scleritis after strabismus surgery.

Surgically induced necrotizing scleritis (SINS) is an uncommon but devastating complication that may occur days to years after ocular surgery. We report the case of a 32-year-old man who underwent uncomplicated strabismus surgery for large-angle exotropia and developed SINS characterized by painless scleral inflammation, choroidal exposure, and globe ectasia within days of surgery. Work-up revealed no associated infectious process or underlying systemic inflammatory condition. Clinical resolution occurred with oral immunosuppression alone, without need for graft.

Encapsulated bleb with scleral fistula - A diagnostic dilemma treated by a simple procedure.

We present a case of post-trabeculectomy encapsulated dysesthetic bleb with scleral fistula, managed successfully with autograft. The child was operated on twice before for trabeculectomy, and intraocular pressure (IOP) recorded was in the normal range for the initial few years. This time child presented with a large encapsulated dysesthetic bleb with borderline IOP. As the IOP was on the lower side, an underlyings cleral fistula was suspected and planned for bleb revision with a donor patch graft. We describe the novel technique of bleb revision along with the repair of the scleral fistula with an autologous free fibrotic Tenon's tissue graft instead of a donor patch graft with a successful outcome.

Every eye needs a best chance to see: Just give it.

Background: Anterior staphyloma is defined as a localized defect in the anterior eye wall with protrusion of the uveal tissue due to alterations in scleral thickness and structure. The causes could be congenital, trauma, or following infection. Surgical options include staphylectomy with graft (corneal/corneoscleral), biosynthetic graft, enucleation or evisceration in a painful blind eye). Purpose: To demonstrate staphylectomy with careful preservation of ocular structures followed by optical keratoplasty in a single setting. Synopsis: A 39-year-old Asian Indian lady presented with complaints of blurring of vision and whitish opacity in both eyes since childhood, associated with progressive enlargement and protrusion of the black part of the left eye with severe pain at the time of presentation. Her clinical examination revealed leucomatous corneal opacity in both the eyes and anterior staphyloma and keratinization in the left eye. Visual acuity was counting fingers close to face in the right eye and hand movements close to face in the left eye with projection of rays being accurate in both eyes. Ultrasound B scan showed posterior staphyloma in the right eye with sub-Tenon's fluid and increased retinochoroidal thickness. The left eye posterior segment with B scan was normal. The available surgical options were evisceration with secondary orbital implant and ocular prosthesis or staphylectomy with corneal transplantation. To provide the best option for the patient in her eye with better visual potential, staphylectomy with corneal transplantation was done. Highlights: Painful blind eye is usually dealt with evisceration. This video demonstrates the technique of staphylectomy with corneal graft and restoration of structural integrity. Evisceration is a destructive procedure that involves removal of the intraocular contents. The patient will have to deal with the hassles of prosthesis maintenance and stigma of the artificial eye. Video link: https://youtu.be/VoS8Irsh1yY.

Novel use of an autologous scleral button graft to close the anterior defect in evisceration surgery.

PURPOSE: To present an alternative evisceration technique with long-term follow-up data. This technique involves the insertion of an acrylic implant into a modified scleral shell which is closed using an autologous scleral graft. METHODS: This was a retrospective analysis of eviscerations performed in a district-general hospital in the UK. All patients underwent conventional ocular evisceration after total keratectomy. A full thickness scleral graft is harvested from the posterior sclera, using an internal approach, with an 8 mm dermatological punch. An 18-20 mm acrylic implant is placed into the shell, and the scleral graft is used to close the anterior defect. Demographic characteristics, implant size and type, and cosmetic results from pictures of all patients were recorded. All patients were invited for a review to measure motility, eyelid height, patient recorded satisfaction and complications. RESULTS: Of the five patients identified, one had since died. The remaining four attended a review in person. The mean time between surgery and review was 48 months. The mean implant size was 19 mm. There were no cases of implant extrusion or infection. All four had a <1 mm asymmetry in measured eyelid height and ≥5 mm horizontal gaze motility. All patients self-reported "good" cosmesis. An independent assessment identified "mild asymmetry" in two cases and "moderate" in the other two. CONCLUSION: Evisceration with this novel autologous scleral graft technique restores volume in the anterior orbit with good cosmetic results, and with no cases of implant exposure reported in this small case series. This technique should be compared prospectively to established techniques.

Application of Decellularized Porcine Sclera in Repairing Corneal Perforations and Lamellar Injuries.

Scleras are mainly used for the treatment of glaucoma, eyelid damage, and scleral ulcers. Given that the sclera and cornea collectively constitute the complete external structure of the eyeball and both have the same tissue and cell origin, we attempted to identify scleral materials to treat lamellar and penetrating corneal injuries. Based on research in our center, antigenic components in decellularized porcine sclera (DPS) were removed using a simplified decellularization method, leaving the collagen structure and active components undamaged. DPS preserved the mechanical properties and did not significantly inhibit the proliferation and replication of human corneal epithelial cells. In vivo, the graft epithelium healed well after lamellar and penetrating scleral grafting, and the graft thickness did not change evidently. DPS can resist suture traction during scleral transplantation and maintain anterior chamber stability until day 28 post-operatively, especially in penetrating repairs. No obvious immune rejection of lamellar or penetrating scleral grafts was found 28 days after DPS transplantation. This study shows that DPS could be used as an alternative material for the emergency repair of corneal perforations and lamellar injuries, representing another application of sclera.

Anterior staphyloma repair following trauma and surgery - A retrospective review of techniques and outcomes over 25 years.

Purpose: To review surgical options, techniques, and outcomes of anterior staphyloma repair done following trauma and surgery. Methods: This was a retrospective case study of patients who underwent staphyloma repair with scleral or tibial periosteal patch grafts following trauma and surgery with a minimum follow-up of 3 months postoperatively. Preoperative risk factors, choice of graft materials, surgical details, and outcomes in terms of graft uptake and tectonic integrity were analyzed. Results: Seventeen eyes of 17 patients underwent successful staphyloma repair (scleral 15, tibial periosteal two). Mean follow-up was 47.1 months (3-159 months). Postoperative intraocular pressure rise noted in four eyes was controlled medically or surgically. Three patients underwent successful repeat patch grafting (graft melt one and recurrent ectasia two). Tectonic integrity of the eyeball was restored and maintained in all patients at the final follow-up. Conclusion: Comprehensive evaluation of the risk factors, control of ocular comorbid conditions, and early and meticulous surgery can optimize results.

The effects of hydroxyapatite implantation with the autogenous sclera cap: A cohort study.

We performed a novel hydroxyapatite (HA) prosthesis implantation method in which an HA implant was implanted into the scleral shell with an autogenous scleral cap. Twenty-six patients who had undergone the novel HA prosthesis implantation method and 32 patients who had undergone traditional HA prosthesis implantation were retrospectively reviewed. The postoperative activity of the artificial eye was measured by the Hirschberg test combined with arc perimetry. The visual analog score (VAS) was used to evaluate 2-month postoperative pain and 2-month postoperative discomfort. HA implant vascularization was measured with enhanced magnetic resonance imaging (MRI) 2 and 6 months after the operation. The enhancement volume (VE) and the volume of the HA implant (VHA) were measured. All cases were followed up for 2 years. Measurement data were processed using SAS 6.12. There was a statistically significant difference (P = .016) between the percentages of excellent grade in the two groups. Two months after implantation, the median pain scores of the study and control groups were 2 and 2.5, respectively, and there was a statistically significant difference (W = 585.0, P = .004); there was a statistically significant difference (W = 535.5, P = .000) between the median discomfort scores of the study group (score = 1) and control group (score = 2); the mean VE/VHA values of the study and control groups were 0.3075 and 0.1535, respectively, and there was a statistically significant difference (t = -8.196, P = .000). Six months after implantation, the VE/VHA values of the study and control groups were 0.9686 and 0.5934, respectively, and there was a statistically significant difference (W = 549.0, P = .000). Within 2 years of postoperative follow-up, there were no serious complications in the study group. In the study group, in which the hydroxyapatite implant was implanted into a preserved scleral shell with unaltered muscles and covered with an autogenous scleral cap, postoperative activity and the fibrovascularization of the HA implant were significantly increased, and postoperative pain and discomfort were significantly reduced.

Four in one: Four recepients with a single donor tissue - A novel concept for eye transplantation surgery post-COVID-19.

A donor corneo-scleral button was dissected into four parts using a simple manual technique. The anterior corneal lamellae was stripped from the Descemet's Membrane (DM) and Deep Anterior Lamellar Keratoplasty (DALK) was performed in a patient with advanced keratoconus after removing the recipient's stroma using the big bubble technique. Descemet's Membrane Endothelial Keratoplasty (DMEK) was done with the stripped donor DM in a patient with Fuch's endothelial dystroph (FECD). The cadaveric limbal stem cells from the tissue were used for simple limbal epithelial transplantation (SLET) in a Steven- Johnson Syndrome (SJS) with localized limbal stem deficiency and symblepharon. The sclera was used to revise a leaking hypotonus bleb in an advanced single-eyed glaucoma patient. No intraoperative or postoperative complications were observed. At 1 year, all the 4 cases retained healthy transplanted tissues with good visual outcomes. Shortage of donor eyes is a global problem and with the present COVID-19 scenario the situation is bound to worsen. The advent of customized component corneal transplantation using simple cost-effective techniques will be the future trend in the years to come.

Scleral defect repair using decellularized porcine sclera in a rabbit model.

BACKGROUND: The sclera is one of the most commonly used repair materials in ophthalmic plastic surgery and is often used for supporting, wrapping, filling, and pressing during surgery. Although the sclera plays an irreplaceable role in ophthalmology applications, there are many restrictive factors, such as high costs and limited sources. Here, we report the use of a decellularized porcine sclera (DPS) for scleral reconstruction in rabbit models. METHODS: The DPS generated by a hybrid decellularization protocol was characterized in respect of histological observation, DNA, α-gal, GAG, and collagen content. The mechanical properties were evaluated by uniaxial tensile testing. LIVE/DEAD and Cell Counting Kit (CCK)-8 assays were performed to assess its in vitro cytocompatibility and cytotoxicity. In vivo biocompatibility and biointegration of the DPS for repairing scleral defect in rabbit were measured by slit-lamp and histological analyses. Immunohistochemical (IHC) staining was used to detect the expression of CD4, CD8, CD45, CD68, and vimentin. RESULTS: Through decellularization, the major xenoantigen DNA and α-gal are efficiently removed while abundant matrix components and mechanical properties are well preserved in the DPS. Extracts of the DPS and DPS samples had no inhibitory effects on the proliferation of HFSFs. Moreover, there was no sign that an immune reaction occurred in or around the transplanted DPS grafts within 28 days of animal implantation. CONCLUSION: The decellularization strategy we developed is feasible and effective. The prepared DPS holds great potential for the repair of scleral injury.

Current clinical application of sclera and amniotic membrane for ocular tissue bio-replacement.

To report the current clinical applications and trends of scleral and amniotic membrane use in ophthalmology. Review of annual reports from the Catalan Transplant Organization (OCATT), on scleral patch and amniotic membrane eye indications in Catalonia region (Spain) over a 6-year period from 2013 to 2018. A total of 874 scleral and 1665 amniotic membranes patches were implanted, from January 2013 to December 2018. The most frequent indication over the 6-year period for scleral patch was glaucoma surgery (77.5%), eyelid reconstruction (5.2%) and corneal or scleral ulcer (5%). Regarding amniotic membrane, corneal ulcer (26.9%), conjunctival reconstruction (23.8%) and corneal epithelial defect (22.7%) were the most common indications. During the study period, an increasing trend was found on sclera patches for eyelid reconstruction (p = 0.0032) and amniotic membrane for inflammation management (p = 0.0198). Glaucoma surgery and corneal ulcers have represented the top indications for scleral patch and amniotic membrane use, over the period, respectively. A significant trend has also been found towards eyelid reconstruction using scleral patches and amniotic membrane for anterior segment inflammation management. This evolving scenario in tissue use for ocular surgery has to be taken into consideration, especially regarding eye banks facing current and futures changes in tissue preservation, storage and indications.

Surgical and Immunohistochemical Outcomes of Scleral Reconstruction with Autogenic, Allogenic and Xenogenic Grafts: An Experimental Rabbit Model.

Purpose: Choukroun's platelet-rich fibrin (PRF), a second-generation platelet concentrate, has unique morphological and chemical features and may be considered as a scaffold for scleral reinforcement and regeneration. The purpose of this study was to compare the use of xenogenic human-derived amniotic membrane (HAM), allogenic sclera, and autogenic PRF in rabbit lamellar scleral defect model with respect to both anatomical and immunohistochemical improvement. Methods: A total of 45 adult New Zealand rabbits were randomized into five groups: normal control; without surgical procedure, negative control; scleral defect model (SDM), xenogenic HAM; SDM+HAM graft, allogenic sclera; SDM+allogenic sclera graft, autogenic PRF; SDM+autogenic PRF graft. Clinical findings, Hematoxylin&Eozin (HE), Masson Trichrome, Verhoeff Acid Fuchsin, Transforming Growth Factor ß Receptor 1, Fibroblast Growth Factor, Bone Morphogenetic Protein 2, collagen type 1, aggrecan, and Matrix Metalloproteinase 2 were evaluated. Results: Ocular surface inflammation was significantly lower in normal control and autogenic PRF groups (p < .001). Graft was avascular and not integrated to scleral wound area in 25% rabbits of allogenic sclera group (p = .02), was out of the scleral wound in 33.3% rabbits of xenogenic HAM group (p > .05), all the grafts were at the normal location and viable in autogenic PRF group. The inflammation and vascularization in autogenic PRF group was significantly lower than negative control and xenogenic HAM groups in HE (p < .001). The collagen score of negative control and xenogenic HAM groups were significantly lower than normal control (p < .001) and autogenic PRF (p < .001) groups. There were insignificant differences between allogenic sclera and autogenic PRF groups (p > .05). For immunohistochemistry, the closest values to normal control group were detected in autogenic PRF group for all immunomarkers. Conclusion: Autogenic PRF showed superior features via its excellent anatomical and chemical composition for scleral regeneration when compared to single-layered xenogenic HAM and allogenic sclera grafts.

Aurolab Aqueous Drainage Implant With and Without Scleral Patch Graft in Refractory Adult and Pediatric Glaucomas: A Comparative Study.

PURPOSE: To compare the 2-year outcomes of eyes that received the Aurolab aqueous drainage implant (AADI) with and without a scleral patch graft. DESIGN: Retrospective comparative interventional case series. METHODS: Eyes with AADI and a minimum of a 2-year follow-up were included. Eyes that underwent implantation before January 2016 had surgery with a scleral patch graft covering the distal end of the tube, whereas those that were implanted after this period underwent surgery using a needle-generated scleral tunnel without the patch graft. The cumulative failure of the AADI was defined as intraocular pressure (IOP) >18 mm Hg or not reduced by 30% below baseline on 2 consecutive follow-up visits after 3 months. RESULTS: We included 215 adult eyes (n = 147 with patch graft, n = 68 without patch graft) and 111 pediatric eyes (n = 73 with patch graft, n = 38 without a patch graft). The mean IOP in eyes without the patch graft was higher at 1 month in adult eyes (before, 27.5 ± 14.1 vs after, 22.3 ± 11.1; P = .01) but not in pediatric eyes (14.3 ± before, 5.8 vs after, 17.8 ± 11.0; P = .39); there were no differences in IOP, vision, number of antiglaucoma medications, and complications between groups at all other time points. None of the eyes without the patch graft experienced tube exposure. Cumulative success rates at 2 years in adults (66.2% vs 63.9%, respectively; P = .85) were similar to those in children (77.2% vs 71.9%, respectively; P = .83) with both techniques. CONCLUSIONS: AADI placed without a scleral patch graft is as safe and effective as AADI placed with a patch graft in pediatric and adult refractory glaucomas.

Early Application of Bevacizumab After Sclerocorneal Grafting for Patients With Severe Late-Stage Ocular Chemical Burns.

PURPOSE: To investigate whether subconjunctival bevacizumab help prevent corneal graft neovascularization and prolong the graft survival of patients with chemical burns. METHODS: We performed a prospective nonrandomized comparative case series study. Twenty-six eyes received subconjunctival bevacizumab (10 mg/0.4 mL) once and topical immunosuppressive agents after sclerocorneal lamellar keratoplasty as the treatment, and 13 eyes received a topical immunosuppressant alone and served as the control group. The main outcomes were a cumulative probability of graft survival, development of corneal neovascularization, and complications. RESULTS: The postoperative follow-up time was 14.3 months (range, 2-62 mo). The cumulative graft survival time was significantly longer in the treatment group than that in the control group (42.9 ± 5.9 vs. 4.8 ± 0.7 mo; log rank < 0.001). In the treatment group, 19 of the 26 grafts (73.1%) survived as transparent with a mean follow-up of 18.7 ± 3.0 months. At the end of the follow-up, 4 grafts remained free of neovascularization, 2 developed edema without neovascularization, and 15 remained transparent with a stable ocular surface and some neovascular vessels in the peripheral transplant interface. The other 5 grafts became opaque and neovascularized. In the control group, all grafts became opaque and neovascularized within the follow-up period (5.5 ± 0.7 mo). During the follow-up, a corneal epithelial defect developed in 9 eyes in the treatment group and 7 in the control group. CONCLUSIONS: Early application of subconjunctival bevacizumab after sclerocorneal lamellar keratoplasty can significantly prevent corneal neovascularization and promote graft survival for severe late-stage ocular chemical burns.

Scleral patch grafting for scleral wound thinning after pars plana phacoemulsification and aspiration: A case report.

RATIONALE: Here we report the case of a patient who required closure with an autologous scleral patch graft during reoperation after developing marked scleral thinning in the late stage after pars plana phacoemulsification and aspiration (PPPEA). To the best of our knowledge, this is the first reports of the procedure being used for the treatment of a thinned scleral section post PPPEA. PATIENT CONCERNS: This study involved a 73-year-old woman who had undergone vitreous surgery combined with PPPEA for retinal detachment in her right eye 8 years earlier and subsequently underwent intraocular lens (IOL) ciliary sulcus suture fixation. DIAGNOSES: She became aware of visual disturbance in her right eye and slit-lamp examination revealed the dislocation of the IOL. INTERVENTIONS: To remove the dislocated IOL and resuture the nasal loop back onto the ciliary sulcus of the patient's right eye, a 25-guage trocar was placed on the superior temporal side. OUTCOMES: Subsequent removal of the trocar from the patient's right eye left an approximately 3-mm-wide oval-shaped gap at the trocar insertion site due to extreme thinning of the sclera in that area; that is, the location where the PPPEA was performed. Since suture fixation failed to stop intraocular fluid leakage, an inferior free half-thickness scleral flap was created to patch the scleral wound. Postsurgery, the leakage in that eye stopped and the intraocular pressure was stable. No complications were observed during the 1-year-postoperative follow-up period. LESSONS: Since thermal injuries during PPPEA may lead to postoperative scleral thinning, surgeons should avoid the site of a prior PPPEA when constructing a scleral wound during reoperation.

Autologous Partial-thickness Scleral Flap and Donor Corneal Graft in Management of Tube Erosion of Glaucoma Drainage Device.

PURPOSE: To evaluate the outcomes of autologous limbus-hinged partial-thickness scleral flap and half-moon-shaped split-thickness donor corneal allograft in management of tube erosion of glaucoma drainage device. METHODS: Consecutive patients who had undergone a limbus-hinged partial-thickness scleral flap and half-moon-shaped split-thickness corneal graft were reviewed. Primary outcome was surgical success of coverage of the exposed tube without complications or additional surgeries. Secondary outcomes were visual acuity (VA), intraocular pressure, number of glaucoma medications, surgical complications, and additional surgeries. RESULTS: From March 1, 2016 to August 30, 2017 (18 mo), 8 consecutive cases (7 patients) of tube erosions were included for analysis. Mean follow-up and age were 16.6±5.4 months and 74.4±15.2 years, respectively. Mean number of intraocular surgeries was 4.8±1.6 (range: 3 to 6 surgeries) and intraocular glaucoma surgeries was 2.9±1.7 (range: 1 to 6 surgeries) before tube erosion. There were no intraoperative or postoperative complications or recurrence of tube erosion in any patient. Differences between the preoperative and postoperative number of medications (2.6±1.8, 2.9±1.8, respectively; P=0.171) and intraocular pressure (12.9±6.9, 10.8±3.5 mm Hg, respectively; P=0.209) were not statistically significant. Preoperative and 3-month postoperative VA were identical in all eyes except in 1 eye that the VA improved from 20/300 to 20/70 after repair. CONCLUSIONS: Combination of limbus-hinged partial-thickness scleral flap and half-moon-shaped split-thickness corneal allograft is a viable surgical option to repair tube erosion.

Outcomes of the Shunt Tube Exposure Prevention Study: A Randomized Clinical Trial.

PURPOSE: To compare the long-term safety and efficacy of amniotic membrane-umbilical cord (AM-UC) and pericardium patch grafts in reducing glaucoma shunt tube exposure. DESIGN: Multicenter, prospective, randomized clinical trial. PARTICIPANTS: Adults with uncontrolled glaucoma undergoing glaucoma drainage device (GDD) implantation. METHODS: Patients were randomized to receive GDD with either AM-UC or pericardium patch grafts to cover GDD tubes. Patients were followed up clinically with anterior segment (AS) OCT to assess patch graft stability and host-tissue integration prospectively. MAIN OUTCOME MEASURES: Tube exposure, graft thinning, and graft-related complications. RESULTS: A total of 81 eyes of 81 patients (50 women, 31 men) with a mean age of 67±13 years underwent GGD implantation using Baerveldt (n = 72) or Ahmed valve (n = 9). Tubes were inserted in the anterior chamber (n = 71), sulcus (n = 6), or pars plana (n = 4). Tube ligation was performed with Baerveldt GDD along with fenestration (n = 51) or orphan trabeculectomy (n = 21). Tubes were covered with AM-UC (n = 41) or pericardium (n = 40). The mean follow-up time was 29±8 months (range, 13-40 months). Tube exposure occurred in 1 eye (2%) in the AM-UC group at 3 months and in 2 eyes (5%) in the pericardium group at 2 and 6 months (P = 0.54). Sequential AS OCT showed better host-tissue integration and significantly less graft thinning in the AM-UC group. Early graft thinning (≤3 months) occurred in 5 eyes (12%) in the AM-UC group and in 17 eyes (43%) in the pericardium group (P = 0.002). Late thinning occurred in 2 eyes (5%) and 11 eyes (28%) in the AM-UC and pericardium groups, respectively (P = 0.007). Graft translucency and cosmetic appearance of the AM-UC graft were superior to those of the pericardium graft. No evidence of graft rejection or infection was associated with the patch grafts in either group. CONCLUSIONS: Amniotic membrane-umbilical cord grafts are well tolerated and offer an alternative to pericardium for safe and stable tube shunt coverage. Its high-tensile strength, low immunogenicity, and excellent host-tissue integration significantly reduced graft thinning.