Supply Of Allografts Research Articles

Paper 02: Distal Radius Allograft for Glenohumeral Instability: A Novel Osteochondral Allograft Reconstruction Option in the Setting of Glenoid Bone Loss

Objectives: Glenoid bone loss in the setting of recurrent shoulder instability remains a challenging surgical problem. The coracoid process and iliac crest currently serve as primary autograft options for glenoid reconstruction. With regards to allograft alternatives, the distal tibia, first described in 2007, has good midterm outcomes when used during an index surgery and in cases of failed prior Latarjet reconstruction. While the distal tibia performs well in reconstructing the glenoid bony defect, it is a nonanatomic reconstruction and does not match the glenoid radius of curvature (ROC) in the anterior to posterior (AP) plane. No prior work has evaluated and described the utilization of the dorsal articular portion of the distal radius as an allograft reconstruction option for recurrent instability with glenoid bony deficiency. The purpose of this study was to evaluate distal radius fresh frozen allograft as a potential match for glenoid reconstruction through assessment of graft ROC and bone mineral density (BMD). Distal tibia allograft was utilized as the primary comparison group with both cadaveric and Computerized Tomography (CT) analysis. Methods: Eighteen fresh-frozen human cadaveric specimens (6 shoulder, 6 wrist, and 6 tibia) were utilized for this study. Specimens without osteoarthritis or prior surgical procedures were included. CT scans were obtained of all specimens to confirm the absence of osteoarthritis, significant joint deformity, or evidence of prior surgical procedure. Specimens were dissected free of all soft tissues except for the glenoid labrum of the shoulder and dorsal wrist ligaments of the distal radius. The ROC for each specimen were independently measured by two fellowship trained shoulder surgeons in both the superior to inferior (SI) and AP planes. Graft length in the SI plane was also assessed. A thirty percent defect was then created in all glenoid specimens and both distal tibia and distal radius grafts were harvested to assess graft fit post-fixation [Figure 1]. CTs were also analyzed to assess bony ROC and BMD for each specimen. Results: On cadaveric analysis, the mean SI graft length of the glenoid was 39.7 mm compared to 36.8 mm for the distal radius and 30.0 mm for the distal tibia [Table 1A]. Average ROC in the SI plane was 29.0 +/- 5.3 for the glenoid, 37.8 +/- 4.9 for the distal radius and 24.0 +/- 3.7 for the distal tibia; in the AP plan average ROC was 39.6 +/- 6.6 for the glenoid, 30.4 +/- 18.6 for the distal radius and 126.3 +/- 9.5 for the distal tibia [Table 1B]. On CT analysis, average ROC in the SI plane was 30.4 +/- 1.5 for the glenoid, 30.3 +/- 5.6 for the distal radius and 24.5 +/- 9.4 for the distal tibia; in the AP plane average ROC was 30.8 +/- 2.0 for the glenoid, 19.1 +/- 2.3 for the distal radius and 46.7 +/- 21.7 for the distal tibia [Table 2A]. Mean BMD was 226.3 +/- 79.0 for the glenoid, 228.5 +/-94.7 for the distal radius, 235.0 +/- 96.2 for the coracoid process, and 235.1 +/- 84.6 for the distal tibia [Table 2B]. Conclusions: Given fresh frozen allograft supply and cost constraints, exploration of additional graft options is necessitated. This study presents distal radius allograft as a novel reconstruction option for patients with anterior glenoid bone loss in the setting of recurrent glenohumeral instability. Compared with the distal tibia allograft, the distal radius had greater graft length in the SI plane providing possible utilization in cases of larger bony defects. The distal radius also has a more acute ROC in the AP plane (closer to that of the glenoid) compared with the distal tibia allograft providing a greater potential buttress to anterior humeral translation. Furthermore, the distal radius also has potential to employ the dorsal radio-carpal ligaments to perform an anterior capsular repair following allograft fixation. Finally, compared to currently utilized grafts (coracoid process and distal tibia), the distal radius BMD was not significantly diminished on CT analysis. This study presents the distal radius as a novel allograft reconstruction option in the setting of glenoid bone loss; further biomechanical and clinical investigation is indicated. [Table: see text][Table: see text]

Challenging the Perceptions of Human Tendon Allografts: Influence of Donor Age, Sex, Height, and Tendon on Biomechanical Properties

Background: The use of allograft tendons has increased for primary and revision anterior cruciate ligament reconstruction, but allograft supply is currently limited to a narrow range of tendons and donors up to the age of 65 years. Expanding the range of donors and tendons could help offset an increasing clinical demand. Purpose: To investigate the effects of donor age, sex, height, and specific tendon on the mechanical properties of a range of human lower leg tendons. Study Design: Descriptive laboratory study. Methods: Nine tendons were retrieved from 39 fresh-frozen human cadaveric lower legs (35 donors [13 female, 22 male]; age, 49-99 years; height, 57-85 inches [145-216 cm]) including: Achilles tendon, tibialis posterior and anterior, fibularis longus and brevis, flexor and extensor hallucis longus, plantaris, and flexor digitorum longus. Tendons underwent tensile loading to failure measuring cross-sectional area (CSA), maximum load, strain at failure, ultimate tensile strength, and elastic modulus. Results from 332 tendons were analyzed using mixed-effects linear regression, accounting for donor age, sex, height, and weight. Results: Mechanical properties were significantly different among tendons and were substantially greater than the effects of donor characteristics. Significant effects of donor sex, age, and height were limited to specific tendons: Achilles tendon, tibialis posterior, and tibialis anterior. All other tendons were unaffected. The Achilles tendon was most influenced by donor variables: greater CSA in men (β = 15.45 mm2; Šidák adjusted P < .0001), decreased maximum load with each year of increased age (β = −17.20 N per year; adjusted P = .0253), and increased CSA (β = 1.92 mm2 per inch; adjusted P < .0001) and maximum load (β = 86.40 N per inch; adjusted P < .0001) with each inch of increased height. Conclusion: Mechanical properties vary significantly across different human tendons. The effects of donor age, sex, and height are relatively small, are limited to specific tendons, and affect different tendons uniquely. The findings indicate that age negatively affected only the Achilles tendon (maximum load) and challenge the exclusion of donors aged >65 years across all tendon grafts. Clinical Relevance: The findings support including a broader range of tendons for use as allografts for anterior cruciate ligament reconstruction and reviewing the current exclusion criterion of donors aged >65 years.

The Impact of Organ Procurement Injury on Transplant Organ Availability

Patients on the transplant waiting list continue to have a significant wait time as organ supply remains low. Many initiatives have been undertaken in the last few years to attempt to increase the organ allograft supply. As organ procurement organizations have attempted to increase their procurement of organs from deceased donors, emphasis has been placed on avoidance of injury to organs during procurement. To analyze the success of this attention, data were collected from 29 of 57 organ procurement organizations in the United States. Data collection was from November 2017 to January 2020. Total injury rate ranged from 6% (donation after brain death) to 8.4% (donation after circulatory death). Level 3 injuries, those resulting in loss of the allograft, ranged from 1.1% in donation after brain death to 1.6% in donation after circulatory death. The most likely injured organ resulting in loss of viability (level 3 injury) during procurement was the right kidney. We noted that among donors with procurement injuries, a higher number had no previous abdominal surgery and there were more injuries noted from attending surgeons (compared to trainees). Deceased donor procurement organ injuries, though rare, lead to substantial loss of transplantable organs every year. Given that the United Network for Organ Sharing has recorded >10,000 deceased donors yearly for the past few years, such injuries can result in hundreds of transplantable organs lost. In this article we detailed the incidence and degree of injury and some variables that may be associated with these injuries.

Evaluation of the Recipient and Donor in Living Kidney Transplantation

Kidney transplantation is the treatment of choice for end-stage renal disease. A successful kidney transplant improves the quality of life and reduces the mortality risk of patients, as compared to maintenance dialysis. The number of patients awaiting kidney transplantation has steadily increased, and the gap between allograft supply and demand continues to widen despite initiatives to expand the use of nonstandard deceased-donor allografts. The use of organs from living donors is one strategy to address the need for transplants. A medical, surgical, and psychosocial evaluation is mandatory prior to living kidney donation to ensure that the donor candidate is in good health and has normal kidney function, is not a risk to the recipient with respect to transmission of infections and malignancy, and will not face unacceptable risks after donation.

Presumed Consent: A Potential Tool for Countries Experiencing an Organ Donation Crisis.

There is currently an inadequate supply of allografts to meet the number of transplant candidates worldwide. A number of controversial policies, including implementation of a presumed consent organ donation system, have been considered to rectify the organ donation crisis. A secondary retrospective data analysis aimed to assess the impact of switching to a presumed consent organ donation model on organ donation rates. Deceased organ donation rates were compared before and after countries adopted presumed consent. Six countries met entry criteria. All six countries had an increase in liver donation rates, while 4 out of the six countries had an increase in kidney donation rates. The overall mean (± SD) liver donation rate was 3.23 (± 0.97) per million population (pmp) before the transition and 6.46 (± 1.81) pmp after the transition (p < 0.0001). The overall mean (± SD) kidney donation rate was 17.94 (± 3.34) pmp before the transition and 26.58 (± 4.23) pmp after the transition (p < 0.0001). The percentage increase in liver and kidney donation rates varied among countries, ranging from 28 to 1186%. The transition from explicit to presumed consent was associated with a significant increase in liver donation rates in all countries that met our criteria, while the effect on kidney donation rates was partially realized. Although presumed consent alone is unlikely to explain the increase in donation rates, the adoption of such a policy may prove to be a worthwhile risk for countries experiencing consistently low organ donation rates.

Graft-Recipient Anteroposterior Mismatch Does Not Affect the Midterm Clinical Outcomes of Osteochondral Allograft Transplantation of the Femoral Condyle

Background: For the treatment of femoral condyle cartilage defects with osteochondral allograft transplantation (OCA), many surgeons have relaxed their graft-recipient size-matching criteria given the limited allograft supply. However, since the anteroposterior (AP) length is typically correlated with the radius of curvature for a given condyle, a large mismatch in graft-recipient AP length can indicate a corresponding mismatch in the radius of curvature, leading to articular incongruity after implantation. Purpose: To evaluate the association between femoral condyle graft–recipient AP mismatch and clinical outcomes of OCA. Study Design: Case-control study; Level of evidence, 3. Methods: A retrospective review was conducted of patients treated with OCA for femoral condyle chondral defects from 2000 to 2015. Graft characteristics, including AP and mediolateral dimensions, were gathered from vendor-specific allograft offering documents. Patient condyle dimensions were measured on preoperative magnetic resonance imaging. Reoperations and patient responses to validated outcome measures were reviewed. Failure was defined by any partial removal/revision of the allograft or conversion to knee arthroplasty. A multivariable logistic regression model was fitted to examine the association of AP mismatch with OCA failure while adjusting for patient age and number of previous ipsilateral knee surgical procedures. Results: A total of 69 knees from 69 patients (mean age, 35.7 years; 71% male) met the inclusion criteria. Mean duration of follow-up was 4 years (range, 2-16 years). The mean absolute graft-recipient AP mismatch was 6.7 mm (range, 0-20 mm; P < .01). At final follow-up, 19 knees had failed. There was no significant difference in the mean absolute AP mismatch between failures (8.1 mm) and nonfailures (6.2 mm; P = .17). Multivariate logistic regression revealed that AP mismatch was not associated with graft failure (P = .14). At final follow-up, significant improvements were noted in the 36-Item Short Form Health Survey, International Knee Documentation Committee subjective form, and Knee Outcome Survey–Activities of Daily Living (P < .01 for all). Magnitude of AP mismatch was not associated with postoperative outcome scores or achievement of minimal clinically significant differences in outcome scores. Conclusion: Magnitude of graft-recipient AP mismatch was not associated with midterm OCA failure rates or patient-reported outcome scores, suggesting that AP length mismatch within the limits measured here is not a contraindication for graft acceptance.

Nine-year results of whole femoral head allograft with articular cartilage for acetabular impaction grafting in revision hip replacement.

INTRODUCTION Acetabular impaction bone grafting with a cemented polyethylene socket aims to reconstitute the bone stock in hip revision. This is an effective but resource intensive and time consuming technique. Usually, the articular cartilage is removed from the femoral head allograft. Our objective was to assess the late results of using the whole femoral head, retaining the cartilage. METHODS Forty-two acetabular revisions using impacted morselised bone graft (retaining the articular cartilage) and a cemented socket were studied retrospectively. The mean follow-up duration was 9.3 years (range: 6-13 years). Clinical and radiological assessment was made using the Oxford hip score, the classification of Hodgkinson et al (1988) for socket loosening and the classification of Gie et al (1993) for evaluation of allograft incorporation. RESULTS Twenty-seven sockets (75.0%) were radiologically stable, six (16.7%) were radiologically loose and three (8.3%) had migrated. Thirty cases (83.3%) showed good trabecular remodelling and six (16.74%) showed trabecular incorporation without remodelling. Six patients were lost to follow-up. Kaplan-Meier analysis calculated a survival rate of 94.5% at a mean of 9.3 years (95% confidence interval: 8.1-10.4 years) for all reasons of failure, with two re-revisions. CONCLUSIONS The nine-year results of the aforementioned technique are comparable with other major studies. Particularly when the supply of allograft and operative time are limited, retaining the articular cartilage of the femoral head is a safe and successful alternative.

Lumbar intervertebral disc allograft transplantation: long-term mobility and impact on the adjacent segments.

Fresh-frozen intervertebral disc (IVD) allograft transplantation has been successfully performed in the human cervical spine. Whether this non-fusion technology could truly decrease adjacent segment disease is still unknown. This study evaluated the long-term mobility of the IVD-transplanted segment and the impact on the adjacent spinal segments in a goat model. Twelve goats were used. IVD allograft transplantation was performed at lumbar L4/L5 in 5 goats; the other 7 goats were used as the untreated control (5) and for the supply of allografts (2). Post-operation lateral radiographs of the lumbar spine in the neutral, full-flexion and full-extension positions were taken at 1, 3, 6, 9 and 12months. Disc height (DH) of the allograft and the adjacent levels was calculated and range of motion (ROM) was measured using the Cobb's method. The anatomy of the adjacent discs was observed histologically. DH of the transplanted segment was decreased significantly after 3months but no further reduction was recorded until the final follow-up. No obvious alteration was seen in the ROM of the transplanted segment at different time points with the ROM at 12months being comparable to that of the untreated control. The DH and ROM in the adjacent segments were well maintained during the whole observation period. At post-operative 12months, the ROM of the adjacent levels was similar to that of the untreated control and the anatomical morphology was well preserved. Lumbar IVD allograft transplantation in goats could restore the segmental mobility and did not negatively affect the adjacent segments after 12months.

BAG-S53P4 as an additive to bone allografts: A laboratory study using an uniaxial compression test.

We want to address the clinical issue of too sparse supply of allograft in total hip replacement and ambitions of controlling the grain size distribution. Bioglass BAG-S53P4 was evaluated as a bone graft additive to chemically treated allografts with controlled grain size distribution. Allografts were chemically cleaned (CG) and mixed with BAG-S53P4 additive (BG) for comparison. All samples were compacted with a dropped weight apparatus and then underwent a uniaxial compression test. The yield limit was determined by a uniaxial compression test and density was recorded while flowability was calculated. There was no difference between the yield stress limit of BG and CG after compaction (p=0.432). Adding BAG-S53P4 reduced flowability and could indicate better interlocking mechanism between particles. Adding BAG-S53P4 seems to have no impact on the yield stress limit. The extended allografts withstand the compaction equally good which makes it a valid bone substitute in total hip replacement. An in vivo loaded study is needed before clinical use can be recommended.

Geographic inequities in liver allograft supply and demand: does it affect patient outcomes?

Significant geographic inequities mar the distribution of liver allografts for transplantation. We analyzed the effect of geographic inequities on patient outcomes. During our study period (January 1 through December 31, 2010), 11,244 adult candidates were listed for liver transplantation: 5,285 adult liver allografts became available, and 5,471 adult recipients underwent transplantation. We obtained population data from the 2010 United States Census. To determine the effect of regional supply and demand disparities on patient outcomes, we performed linear regression and multivariate Cox regression analyses. Our proposed disparity metric, the ratio of listed candidates to liver allografts available varied from 1.3 (region 11) to 3.4 (region 1). When that ratio was used as the explanatory variable, the R(2) values for outcome measures were as follows: 1-year waitlist mortality, 0.23 and 1-year posttransplant survival, 0.27. According to our multivariate analysis, the ratio of listed candidates to liver allografts available had a significant effect on waitlist survival (hazards ratio, 1.21; 95% confidence interval, 1.04-1.40) but was not a significant risk factor for posttransplant survival. We found significant differences in liver allograft supply and demand--but these differences had only a modest effect on patient outcomes. Redistricting and allocation-sharing schemes should seek to equalize regional supply and demand rather than attempting to equalize patient outcomes.

Differential cross-linking and radio-protective effects of genipin on mature bovine and human patella tendons

Gamma irradiation is a proven sterilization method, but is not widely used on allografts for anterior cruciate ligament reconstruction (e.g., patella tendon) due to radiation-induced decreases in mechanical strength. Addressing this drawback would improve the safety and supply of allografts to meet current and future demand. It was hypothesized that genipin-induced collagen cross-linking would increase the tensile modulus of patella tendon tissue such that 5 MRad gamma irradiation would not reduce the tissue mechanical strength below the original untreated values. Optimized genipin treatment increased the tensile modulus of bovine tendons by ~2.4-fold. After irradiation, genipin treated tissue did not significantly differ from native tissue, proving the hypothesis. Optimized genipin treatment of human tendons increased the tensile modulus by ~1.3-fold. After irradiation, both control and genipin-treated tissues possessed ~50-60% of their native tendon modulus, disproving the hypothesis. These results highlight possible age- and species- dependent effects of genipin cross-linking on tendon tissue. Cross-linking of human allografts may be beneficial only in younger donor tissues. Future research is warranted to better understand the mechanisms and applications of collagen cross-linking for clinical use.

Reply: Liver transplantation costs in the era of a health care crisis

We would like to respond to Dr. Haque's recent letter1 regarding our article on health care charges incurred by liver transplant recipients beyond the transplant admission.2 In his letter, he addressed the need for health care cost curtailment across medical specialties. He stated that analyzing the real cost in terms of the paid amount would have been more helpful for guiding specific interventions for cost containment in this population. Although we agree that actual payments would be interesting, we were limited to the available data. Unlike kidney transplantation, there is no national registry of payments following liver transplants. Thus, access to a national, private payer database offered a unique and valuable opportunity for comparing relative costs and the factors that influence transplant payments across many providers. There is ample evidence that charge data are highly correlated with actual costs and can be used to accurately describe relative differences in health care expenditures following liver transplantation as a function of the Model for End-Stage Liver Disease score. Liver transplantation remains the only life-saving therapy for patients with end-stage liver failure and must be considered in the context of other, expensive life-saving treatments such as implantable cardiac assist devices and multi-agent chemotherapy, both of which are associated with significantly less survival benefit. In addition, the cost of liver transplantation is only partially within the control of providers. The cost of liver transplantation is directly linked to the interplay of the recipient's disease severity, the local allograft supply, and the donor quality.2, 3 Therefore, centers in geographic areas with a very high demand for organs with respect to the supply are able to provide transplants to substantial proportions of their candidates only at advanced stages of disease severity, and they use higher risk organs in order to reduce the risk of certain death from untreated liver failure. As shown in our articles, these factors, more than the process of care, drive the cost of this treatment. We certainly agree that appropriate cost containment measures such as avoiding unnecessary investigation and minimizing the practice of defensive medicine should be pursued where possible. We disagree with the assertion that liver transplant costs are significantly inflated by clinical practice. Transplant specialists are limited in what they can do to minimize costs under an organ allocation system that requires the sickest transplant candidates to undergo transplantation first and is characterized by marked regional differences in the organ supply. We believe that resolving geographic disparities in the organ supply to allow earlier transplantation is vital to the economic sustainability of transplantation in an era of limited health care resources. We thank Dr. Haque for his comments and encourage exploration of other data sources to advance our knowledge of modifiable factors that may help us to manage transplant-related costs without worsening disparities in underserved populations. It is equally important to consider the fact that liver transplantation routinely produces 5-year survival rates in excess of 70% for patients destined to die without treatment. Paula M. Buchanan*, Nino Dzebisashvili*, Krista L. Lentine*, David A. Axelrod* , Mark A. Schnitzler*, Paolo R. Salvalaggio* , * Center for Outcomes Research, Saint Louis University School of Medicine, Saint Louis, MO, Department of Surgery, Dartmouth-Hitchcock Medical Center, Hanover, New Hampshire, Department of Surgery, University of Washington, Seattle, WA.

Allograft Tissue in ACL Reconstruction

Musculoskeletal allografts are an essential component for the surgical management of orthopedic injuries. Allografts are most frequently used in the knee for anterior cruciate ligament (ACL) deficiency and less frequently for other ligament lesions, meniscal transplant, and osteochondral repair. Clinical ACL outcomes have continued to improve as techniques and instrumentation have developed. Allografts are routinely used for ACL reconstructions and although some may argue against them, others feel that not using allografts is a disservice to their patients. The increase in demand for a larger and safer supply of allografts is directly related to the growth in the number of allografts being used. Allografts are safe, reliable, and when all factors are considered, is an excellent ligament replacement solution surgeons should consider for their ACL patients.

In vivo testing of a bone graft containing chitosan, calcium sulfate and osteoblasts in a paste form in a critical size defect model in rats

Bone loss associated with musculoskeletal trauma or metabolic diseases often require bone grafting. The supply of allograft and auto-graft bones is limited. Hence, development of synthetic bone grafting materials is an active area of research. Chitosan, extracted from chitin present in crawfish shells, was tested as a de-livery vehicle for osteoblasts in a 2-3 mm size defect model in rats. Twenty-seven male Lewis rats, divided into three groups with sacrifice intervals of 3, 6 & 9 months were used. In the experimental samples, a critical size defect was filled with chitosan bone graft paste and fixed with a plate, while in the operated control group, a critical size defect was repaired only by a plate (no paste was applied). An unoperated control group was also included. Bone growth was evaluated histologically by examining undecal-cified and decalcified stained sections. The fe-murs were also examined non-destructively by micro-computed tomography (礐T). Defects filled with chitosan bone graft paste demon-strated superior healing across all time periods compared to unfilled defects as examined by histology and micro-computed tomography. Crawfish chitosan has successfully been used as a cell delivery system for osteoblasts for use as a synthetic bone graft material.

Comparison of the age-related porcine endogenous retrovirus (PERV) expression using duplex RT-PCR

Porcine endogenous retroviruses (PERVs) are members of family Retroviridae, genus Gamma retrovirus, and transmitted by both horizontally and vertically like other endogenous retroviruses (ERVs). PERV was initially described in the 1970s having inserted its gene in the host genome of different pig breeds, and three classes, PERV-A, PERV-B, and PERV-C are known. The therapeutic use of living cells, tissues, and organs from animals called xenotransplantation might relieve the limited supply of allografts in the treatment of organ dysfunction. Because of ethical considerations, compatible organ sizes, and physiology, the pig has been regarded as an alternative source for xenotransplantation. Sensitive duplex reverse transcription-polymerase chain reaction protocols for simultaneously detecting PERV gag mRNA and porcine glyceraldehydes 3-phosphate dehydrogenase mRNA in one tube was established. To compare the age-related PERV expression patterns of the lung, liver, spleen, kidney, heart, and pancreas in commercial pigs, 20 pigs from four age groups (5 heads each in 10 days-, 40 days-, 70 days-, and 110 days-old, respectively) were used in this study. The expression patterns of PERV were statistically different among age groups in lung, liver, and kidney (ANOVA, p < 0.05). These data may support in the selection of appropriate donor pigs expressing low levels of PERV mRNA.

Role of complement in xenotransplantation.

The xenotransplantation research is driven by the increasing gap between the number of patients with end-stage organ failure on waiting lists for transplantation and the supply of allografts. The lack of success in developing suitable artificial organs for permanent treatment of organ failure has further strengthened the need for xenotransplantation research. Pigs are now generally accepted to be the source animal of choice. Transplantation of pig organs to humans faces several barriers which have to be overcome before it comes to clinical application: (1) anatomical and physiological conditions; (2) immunological rejection mechanisms; (3) molecular compatibility between signal molecules of the two species; (4) risk of transmission of microorganisms, particularly pig endogenous retroviruses; and (5) legal and ethical aspects both with respect to the animal and the recipient. Here we will focus on the role of the complement system in the rejection of immediately vascularized pig-to-primate xenografts. The hyperacute rejection occurring within minutes after transplantation is mediated by binding of natural antibodies to the Galalpha(l-3)Gal epitope on the endothelial cells with subsequent complement activation. Whereas inhibition of complement activation protects against hyperacute rejection, the role of complement in the later rejection phases is less clarified.

Bone allograft harvesting following multiorgan procurement

BONE allografts have been used in orthopedic reconstructive operations for many years. In the last decade, indications for bone allografting have increased, due to the need for treatment of major bone defects after loosening of total hip or knee endoprostheses. The results of bone transplantation reported are mostly encouraging. So far, in Poland, bones for graft preparations have been procured only in mortuaries of forensic medicine departments. Increasing demand for allogenic bone grafts and limited supply has led to a long waiting time for grafts. Despite the increasing number of multiorgan procurements (MP) in Poland, about 400 annually, severe deficits in the bone allograft supply still exist. In 1999 the group of orthopedic surgeons from the Pomeranian Medical University started to perform bone harvesting following the completion of procurements of vascularised organs. The aim of this paper is to present our experience concerning the technical details and the limitations of bone harvesting from multiorgan donors.

Estimation of the shear stress on the surface of an aortic valve leaflet.

The limited durability of xenograft heart valves and the limited supply of allografts have sparked interest in tissue engineered replacement valves. A bioreactor for tissue engineered valves must operate at conditions that optimize the biosynthetic abilities of seeded cells while promoting their adherence to the leaflet matrix. An important parameter is shear stress, which is known to influence cellular behavior and may thus be crucial in bioreactor optimization. Therefore, an accurate estimate of the shear stress on the leaflet surface would not only improve our understanding of the mechanical environment of aortic valve leaflets, but it would also aid in bioreactor design. To estimate the shear stress on the leaflet surface, two-component laser-Doppler velocimetry measurements have been conducted inside a transparent polyurethane valve with a trileaflet structure similar to the native aortic valve. Steady flow rates of 7.5, 15.0, and 22.5 L/min were examined to cover the complete range possible during the cardiac cycle. The laminar shear stresses were calculated by linear regression of four axial velocity measurements near the surface of the leaflet. The maximum shear stress recorded was 79 dyne/cm2, in agreement with boundary layer theory and previous experimental and computational studies. This study has provided a range of shear stresses to be explored in bioreactor design and has defined a maximum shear stress at which cells must remain adherent upon a tissue engineered construct.

Dialysis compared with transplantation as replacement therapy for end–stage renal disease

For medical, psychosocial and economic reasons, renal transplantation is often preferable to dialysis as long-term renal replacement therapy. Nephrologists and transplantation surgeons are contending with an expanding population of patients with end–stage renal disease (ESRD) requiring treatment, and they are forced to weigh increasingly complicated patient–related issues against significant non-patient factors. On the one hand, ESRD patients must be provided with adequate renal replacement therapy, keeping in mind clinical factors that increase morbidity and mortality. On the other hand, there is a tacit obligation to use optimally the limited allograft supply and the available economic resources for the chronic care of ESRD patients. In selecting appropriate renal replacement therapy, we must recognize factors that predict favorable (or adverse) outcome for transplantation compared with dialysis. We must also consider the long-term consequences of our treatment decisions upon individual patients and upon society.