Meniscus transplantation using a cryopreserved allograft. Histological and ultrastructural study of the transplanted meniscus

We performed allogenic meniscus transplantation in rabbits and investigated the regenerative process in the transplanted meniscus with particular respect to its ultra-structure. Under a transmission electron microscope, the chondrocytes and extracellular matrix were degenerated or destroyed in week 0. Fibroblasts were observed 4–8 weeks postoperatively. Immature chondrocytes emerged at 12 postoperative weeks. At 16 weeks, the newly formed chondrocytes and extracellular matrix were virtually normal. Although the diameter of collagen fibrils still varied, their arrangement was dense and the filaments had almost normal banding. This study demonstrated that newly formed chondrocytes may differentiate from fibroblasts 8–12 weeks after transplantation. The fibroblasts synthesized collagen fiber and glycosaminoglycan, indicating that repair of the extracellular matrix may be initiated 4–8 weeks postoperatively, becoming were active after 12 weeks when the newly formed chondrocytes emerge. The extracellular matrix is injured during rapid freezing, cryopreservation, and slow thawing, and repair is delayed due to this deterioration. The extracellular matrix thus needs to be protected from injury as far as possible in order to promote its repair, since it normalizes more slowly than chondrocytes. Received for publication on Feb. 25, 1998; accepted on Oct. 1, 1998     

Vascularized synovial flap promoting regeneration of the cryopreserved meniscal allograft: experimental study in rabbits

 The purpose of this investigation was to evaluate whether a vascularized or free synovial flap or a fibrin clot can promote regeneration of meniscal allograft in the rabbit. Seventy-eight mature New Zealand white rabbits were used. The harvested medial meniscus for the allotransplantation was frozen and stored at −80°C for 2 weeks. After resecting the medial meniscus, an allogenic meniscus was transplanted in the anatomical position (group A). The surface of the graft was covered by a vascularized synovial flap (group B), a free synovial flap (group C), or a fibrin clot (group D). The animals were killed 4, 6, 8, 12, and 16 weeks after transplantation, and the transplants were examined by gross inspection, histology, and microangiography. Connective tissue infiltration into the matrix of the graft was found to begin at 6 weeks (2/5 menisci) and to be complete at 8 weeks (5/5 menisci) in group B, whereas it began at 8 weeks (1/5) in group A. The newly formed repair tissue developed from the synovial tissue and consisted of connective tissue at the beginning and fibrocartilage later. The fibrocartilage had appeared at 8 weeks (3/5) in group B but not yet in group A (0/5). A free flap or fibrin clot coverage resulted in delayed revascularization compared to a vascularized synovial flap, but both tended to achieve faster revascularization than the controls. We concluded that regeneration of allografted meniscus with a vascularized synovial flap occurs earlier than under other conditions. Thus, allografts with synovial implantation may be considered for management of the meniscectomized knee. Received: October 18, 2001 / Accepted: September 27, 2002 Offprint requests to: K. Yamazaki     

Early rupture of a cryopreserved arterial allograft

Cryopreserved arterial allografts are used in vascular surgery to treat infected arterial prosthesis. This treatment reduces mortality and morbidity compared to conventional surgery. We observed a case of early rupture of the allograft with the death of the patient due to a misdiagnosis. Recent findings show that cases of rupture have been described, and that current cryopreservation protocols may be the cause of degeneration. To avoid a sudden death for the patient, this complication must be known to diagnose quickly and treat surgically before a final haemorrhagic shock.     

Posterior peripheral sutures in meniscal allograft replacement.

In our experience, meniscal allograft transplantation does have a role after a total or a significant partial meniscectomy in young to middle-aged symptomatic patients. While the quality of the meniscal tissue is crucial to the success of the operation, it is equally important to duplicate the mechanical function of the original semilunar cartilage and assure a secure peripheral attachment of the meniscal implant. The technique for peripheral meniscal suture placement described in this article permits an easier and more secure attachment of the posterior third of the implant to the joint capsule.     

Biologic resurfacing of the glenoid using a meniscal allograft

Biologic resurfacing of the glenoid is a treatment alternative for young patients who develop rapid and aggressive destruction of glenoid. In 2001, a technique was developed to allow secure fixation of a meniscal allograft to the glenoid in combination with hemi-arthroplasty replacement of the humeral head. The authors have modified this technique by addressing posterior wear factors, as well as circumferential covering of the glenoid perimeter. The meniscal horns are sutured together to fashion the allograft in an ovoid shape. The meniscus closely matches the circumference of the glenoid and therefore 180 degrees coverage of the glenoid rim is achieved. In addition, the wedge shape of the meniscus may enhance comfort and stability.     

同种异体半月板移植术临床效果的初步分析

目的探讨关节镜下异体半月板移植的手术适应证、康复训练计划和免疫反应等问题。方法建立国人异体半月板组织库，对12例半月板损伤后切除半月板的患者，在关节镜下实施异体半月板移植微创手术，制定康复计划，观查其临床效果，结合文献讨论异体半月板移植术的围手术期相关问题。结果本组患者均无手术副损伤，早期关节轻度肿胀，无伤口渗液。术后2周，伤口愈合良好。术后6周，关节肿胀基本消失。随访6—17个月（平均10．3个月），患者行走功能正常，膝关节活动度均值与术前比较差异无统计学意义。膝关节疼痛评分（VAS）术后明显低于术前（P〈0．01）。Lysholm评分术后明显提高（P〈0．05）。术后各项免疫学指标均在正常范围。MRI示移植半月板位置良好，固定可靠。1例患者术后12周关节镜检查，见移植半月板形态正常，与关节囊愈合良好。结论鉴于目前对半月板切除术后（半月板缺损）的并发症治疗存在很大困难，异体半月板移植可能成为一项重要的临床治疗技术。异体半月板移植可获得较好的近期临床效果，临床未见明显的免疫排斥反应。但有关异体半月板移植手术适应证、康复训练及远期效果等围手术期的相关问题还需更深入的探讨。     

Experimental tracheal transplantation using a cryopreserved aortic allograft

BACKGROUND: The tracheal reconstruction after wide resections remains a critical surgical problem. Our aim was to replace trachea with a tissue easy to vascularize, which allows a simple reconstruction and does not require an immunosuppressive regimen. MATERIALS AND METHODS: A segment of cryopreserved aorta was used in order to verify its adequacy as tracheal substitute. In phase 1, the thoracic aorta of 10 rabbits was excised, obtaining 20 segments that were cryopreserved. Ten segments were implanted in the omentum of 10 rabbits that were sacrificed on postoperative days 7, 14 and 21, and the grafts were examined histologically. In phase 2, a segment of cryopreserved aorta arranged with a silicone prosthesis was transplanted in 10 rabbits and wrapped with omentum. The animals were sacrificed on postoperative days 7, 14 and 21. RESULTS: In phase 1, the neovascularization of the grafts was present after 7 days, and after 14 days the fibroblasts invaded the lumen of the aorta. In phase 2, 8 rabbits survived and the histologic examination after 7, 14 and 21 days showed neovascularization, the absence of rejection and the proliferation of fibroblasts inside the lumen of the aorta; this growth has been restrained by an endoluminal prosthesis. CONCLUSIONS: Our study demonstrated that replacing the trachea with cryopreserved aorta is technically feasible and does not evoke immunologic reactions. It requires, however, a silicone tube inside the allograft to limit the colonization of fibroblasts.     

Valve replacement with cryopreserved allograft

Allograft valves have several advantages such as 1) the absence of thromboembolic complications without anticoagulation, 2) superior durability to bioprosthetic valves, 3) good resistance to infection, 4) excellent hemodynamic performance especially in small sizes. Surgeons in western countries, therefore often use these valves and have reported good long-term results. In Japan, there have been only a small number of case reports on such valve replacement. We experienced five cases of valve replacement with cryopreserved allografts, four men and one woman. Four of them had formerly received AVR or Cabrol operation, and the prosthetic valve (graft) infection or aortitis syndrome was the main reason of reoperation. One 15 year-old woman suffering from congenital aortic stenosis underwent Ross operation with pulmonary allograft. Although one case with PVE received re-re-AVR 2 years and 4 months after the allograft replacement because of the recurrence of infection, the other four cases are in good condition long after the surgery. We hope that the use of allograft valves will become common in Japan.     

Transplantation of viable meniscal allograft. Survivorship analysis and clinical outcome of one hundred cases

BACKGROUND: Few medium-term or long-term reports on meniscal allograft transplantations are available. In this study, we present the results of a survival analysis of the clinical outcomes of our first 100 procedures involving transplantation of viable medial and lateral meniscal allografts performed in ninety-six patients. METHODS: Thirty-nine medial and sixty-one lateral meniscal allografts were evaluated after a mean of 7.2 years. Survival analysis was based on specific clinical end points, with failure of the allograft defined as moderate occasional or persistent pain or as poor function. An additional survival analysis was performed to assess the results of the sixty-nine procedures that involved isolated use of a viable allograft (twenty of the thirty-nine medial allograft procedures and forty-nine of the sixty-one lateral allograft procedures) and of the thirteen viable medial meniscal allografts that were implanted in combination with a high tibial osteotomy in patients with initial varus malalignment of the lower limb. RESULTS: Overall, eleven (28%) of the thirty-nine medial allografts and ten (16%) of the sixty-one lateral allografts failed. The mean cumulative survival time (11.6 years) was identical for the medial and lateral allografts. The cumulative survival rates for the medial and lateral allografts at ten years were 74.2% and 69.8%, respectively. The mean cumulative survival time and the cumulative survival rate for the medial allografts used in combination with a high tibial osteotomy were 13.0 years and 83.3% at ten years, respectively. CONCLUSIONS: Transplantation of a viable meniscal allograft can significantly relieve pain and improve function of the knee joint. Survival analysis showed that this beneficial effect remained in approximately 70% of the patients at ten years. This study identified the need for a prospective study comparing patients with similar symptoms and clinical findings treated with and without a meniscal allograft and followed for a longer period with use of clinical evaluation as well as more objective documentation tools regarding the actual fate of the allograft itself and the articular cartilage.     

Evaluation of cryopreserved allograft venous conduits in dogs.

We investigated the effects of cryopreservation, immunosuppression, and antibiotic treatment on the patency and histologic appearance of venous conduits in the arterial circulation. Twenty-eight dogs received arterial replacements with autograft vein, fresh allograft, and two types of cryopreserved allograft vein implanted into both carotid and both femoral arteries. All animals were given aspirin, and half were given cyclosporine. After 3 months the vein grafts were harvested. Patency and light, transmission, and scanning electron microscopic criteria were scored to evaluate quality of preservation of the endothelium, the appearance of rejection, and the effects of cryopreservation with and without antibiotic pretreatment. The results show that patency is not statistically different based on graft type or treatment modality. The histologic appearance among the various vein types was remarkably similar at 3 months, with the exception of a cellular infiltrate present most prominently in the fresh allografts and least in the fresh autografts. Cyclosporine, even at a low dose, decreased the incidence of cellular infiltration. Preservation of endothelium was generally good in the cryopreserved allografts both with and without antibiotic pretreatment. In general, the effects of cryopreservation, cyclosporine, and antibiotics ameliorated the effects of venous allografting into an arterial position.     

Mid-term evaluation of cryopreserved aortic allograft

Recently aortic root replacement and free-hand aortic valve replacement with cryopreserved allograft are accepted and established as useful procedures in USA and Europe. Otherwise allograft aortic valve failure due to structural valve degeneration, progressive loss of leaflet extensibility or progressive aortic root dilatation are reported. Aortic root replacement and free-hand aortic valve replacement with cryopreserved allograft were performed on three patients in the Department of Cardiovascular Surgery, NCVC between March of 1992 and March of 1994. We evaluated the mid-term function of implanted allograft. Case 1, 2; 58-year-old male and 42-year-old male with aortic regurgitation due to Aortitis had modified Bentall procedures with composite graft and had redo surgery for aortic regurgitation due to graft detachment with cryopreserved allograft using “aortic root replacement”. Case 3: 54-year-old male received a cryopreserved allograft for aortic stenosis/regurgitation using “free-hand technique”. Postoperative echocardiogram showed excellent valve function without regurgitation any calcification in all cases. However chest computed tomography suggested the new calcification of allograft wall at 15 months after operation in Case 1 who was administered steroid agents, despite no calcification in Case 2 during 17 months follow-up.     

Meniscal replacement using a cryopreserved allograft. An experimental study in the dog

The medial menisci of 14 adult dogs were replaced using a cryopreserved meniscal allograft. The morphology and metabolic activity of the transplanted allografts were then evaluated using routine histology, a vascular-injection (Spalteholz) technique, and autoroentgenography (Na2(35)SO4 incorporation) at various intervals, from two weeks to six months postoperatively. After transplantation, the allografts retained their normal gross appearance and healed to the capsular tissues of the host by fibrovascular scar tissue. Histologically, the grafts demonstrated a decrease in the number of metabolically active cells after transplantation but had a normal cellular distribution and Na2(35)SO4 uptake by three months. The allografts appeared to function normally after transplantation. Although some degenerative changes were noted in the tibial articular cartilage not covered by the meniscus, the cartilage beneath the allograft appeared normal.     

Comparison of meniscal allograft transplantation techniques using a preclinical canine model

Meniscal allograft transplantation (MAT) can be a safe, effective treatment for meniscal deficiency resulting in knee dysfunction, leading to osteoarthritis (OA) without proper treatment with 5‐year functional success rates (75%‐90%). While different grafts and techniques have generally proven safe and effective, complications include shrinkage, extrusion, progression of joint pathology, and failure. The objective of this study was to assess the functional outcomes after MAT using three different clinically‐relevant methods in a preclinical canine model. The study was designed to test the hypothesis that fresh meniscal‐osteochondral allograft transplantation would be associated with significantly better function and joint health compared with fresh‐viable or fresh‐frozen meniscus‐only allograft transplantations. Three months after meniscal release to induce meniscus‐deficient medial compartment disease, research hounds (n = 12) underwent MAT using meniscus allografts harvested from matched dogs. Three MAT conditions (n = 4 each) were compared: frozen meniscus–fresh‐frozen meniscal allograft with menisco‐capsular suture repair; fresh meniscus–fresh viable meniscal allograft (Missouri Osteochondral Preservation System (MOPS)‐preservation for 30 days) with menisco‐tibial ligament repair; fresh menisco‐tibial–fresh, viable meniscal‐tibial‐osteochondral allografts (MOPS‐preservation for 30 days) with menisco‐tibial ligament preservation and autogenous bone marrow aspirate concentrate on OCA bone. Assessment was performed up to 6 months after MAT. Pain, comfortable range of motion, imaging, and arthroscopic scores as well histological and cell viability findings were superior (P < .05) for the fresh menisco‐tibial group compared with the two other groups. Novel meniscal preservation and implantation techniques with fresh, MOPS‐preserved, viable meniscal‐osteochondral allografts with menisco‐tibial ligament preservation appears to be safe and effective for restoring knee function and joint health in this preclinical model. This has the potential to significantly improve outcomes after MAT.     

Magnetic resonance imaging evaluation of recipient for cryopreserved aortic allograft.

Aortic valve replacement with a cryopreserved aortic allograft is the procedure of choice for many patients with aortic valvular heart disease. We have used magnetic resonance imaging preoperatively to determine annular size and coronary artery orientation in the recipient, which not only has enabled us to select an allograft of appropriate size from a distant tissue bank, but also has helped us to identify preoperatively the recipient with a truly bicuspid valve in which the coronary arteries are oriented 180 degrees apart. Sixteen consecutive patients were evaluated preoperatively, the aortic annulus being measured with both magnetic resonance imaging and echocardiography. Cryopreserved aortic allografts were ordered on the basis of the magnetic resonance imaging measurement. Annular size was then measured intraoperatively with calibrated sizers. Magnetic resonance imaging annular measurements correlated highly with those found at operation (r = 0.92), whereas echocardiographic measurements correlated less well (r = 0.69). Coronary orientation was accurately predicted in every case (r = 1.0). Therefore, we have found magnetic resonance imaging to be useful in the preoperative evaluation of patients for aortic valve replacement with a cryopreserved aortic allograft.     

Aortic root replacement and coronary interposition using a cryopreserved allograft and its branch.

This communication describes a modified aortic root replacement technique using a cryopreserved allograft consisting of the aortic conduit and its branch. This method was applied in a patient suffering from infective pseudoaneurysm which had developed after aortic root replacement using an artificial graft with a mechanical aortic valve. A piece of the innominate artery obtained from the aortic allograft was used for interposition between the fragile left coronary artery root and the main conduit of the allograft.     

Successful management of an aortoesophageal fistula using a cryopreserved arterial allograft

We report a case of aortoesophageal fistula occurring as a complication of colonic esophagoplasty. Emergency treatment during the hemorrhagic phase combined aortic replacement using a cryopreserved arterial allograft and digestive tract exclusion. Immediate recovery and follow-up at 8 months were good. This is the first reported case of successful in situ aortic replacement using a cryopreserved allograft for an aortoesophageal fistula. The lack of previous reports of successful treatment and related treatment modalities are discussed.     

Immediate versus delayed meniscal allograft transplantation in sheep

The aim of the current study was to assess the effect of immediate and delayed transplantation on articular cartilage. Icelandic sheep had surgery on the medial menisci in both knees. The knees were divided into four groups; 16 control knees had sham surgery, 15 knees had meniscectomy, 14 knees had immediate allograft transplantation, and 14 knees had delayed transplantation 3 months after meniscectomy. The two horns of the fresh allograft were fixed with suture anchors through bone tunnels. The sheep had autopsies 6 months after surgery. An additional six knees were examined 3 months after meniscectomy to examine the cartilage before the delayed implantation. Four standardized samples were taken from the medial compartment of the knee for histologic evaluation according to a modification of Mankin's system, where degenerative changes to the articular cartilage were scored semiquantitatively for structure, proteoglycan content, cellularity, and cell cloning. Knees that had meniscectomy and delayed transplantation showed equally high scores in articular cartilage degeneration, and both scored higher than knees that had immediate transplantation, which again scored higher than the control knees. In short-term observations, immediate medial meniscal allograft transplantation reduced but did not prevent degeneration of the articular cartilage. Immediate transplantation was superior to delayed transplantation in preventing cartilage degeneration.     

Early valvular obliteration of cryopreserved aortic valve allograft

This report describes a 60-year-old male patient who developed early valvular obliteration of a cryopreserved aortic valve allograft with associated severe valvular leakage. The patient had previously undergone two operations for aortic valve insufficiency resulting from infective endocarditis, and prosthetic valve endocarditis: aortic valve replacement with a mechanical prosthesis was done 4 years ago, and two years later aortic root replacement with a cryopreserved allograft was performed. Perforation through the non-coronary cusp of the aortic allograft was found, and valve replacement was achieved using a mechanical prosthesis. The intraoperative findings, histological, immunological, and bacteriological studies of the resected cusps demonstrated negative for infection and rejection, therefore, the valvular perforation might have been caused by an injury or degeneration during management of the homologous graft. The patient showed neither aortic regurgitation on echocardiography nor recurrence of endocarditis 10 months after surgery.