IDENTIFYING FEATURES OF EARLY AND LATE AGE-RELATED MACULAR DEGENERATION: A Comparison of Multicolor Versus Traditional Color Fundus Photography.

PURPOSE: To compare multicolor (MC) and traditional color fundus photography (CFP) in their ability to detect features of early and late age-related macular degeneration (AMD). METHODS: Study design: Observational case series. PARTICIPANTS: fundus images captured using standard CFP and MC imaging from 33 patients attending hospital clinics and 26 participants from the pilot phase of the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA). Systematic grading of early and late AMD features; (hard drusen, soft drusen, reticular pseudodrusen, pigment clumping, non-geographic atrophy hypopigmentation, atrophy, hemorrhage, and fibrosis) on CFP and MC. RESULTS: There were 105 eyes with gradable images for comparison. Using CFP as the gold standard, sensitivity values for MC ranged from 100% for atrophy, non-geographic atrophy hypopigmentation, and fibrosis to 69.7% for pigment clumping. Specificity values were high: >80% for all features. On using MC as the comparator, CFP had lower sensitivity for the detection of early AMD features (27.8% for reticular drusen to 77.8% for non-geographic atrophy hypopigmention). Analysis of OCT in discrepant cases showed better agreement with MC for all AMD lesions, except hemorrhage and non-geographic atrophy hypopigmentation. For pigment clumping, CFP and MC were in equal agreement with OCT. CONCLUSION: Multicolor retinal imaging allowed for improved detection and definition of AMD features.

Drusen prevalence and pigmentary changes in Caucasians aged 18-54 years.

AIMS AND PURPOSE: The aim of this study was to describe the prevalence and characteristics of drusen and pigmentary changes in a middle-aged population. METHODS: Retinal images from 500 individuals aged 18-54 years were included. The source of participants was two UK optometry practices. Retinal images were graded using the Wisconsin Age-Related Maculopathy Grading System. However, owing to the relatively young age of the population studied, a new category of drusen of smaller size (<31.5 µm) was introduced. RESULTS: Drusen were identified within the central macular grid in 91.48% of all gradable eyes and in 444 subjects. Drusen sized <31.5 µm were present in 89.7% of eyes, drusen sized >31.5 µm and <63 µm were present in 45.9% of all eyes and drusen >63 µm and <125 µm were present in only 1.7% of eyes. No eye had drusen larger or equal to 125 µm. Very few eyes (1.2%) showed pigmentary changes within the grid. Drusen load increased with increasing age, P <0.001. CONCLUSIONS: The frequency of drusen in a younger Caucasian population aged 18-54 years is high, with 91.48% of all gradable eyes having drusen. The most frequent drusen subtype was hard distinct drusen <31.5 µm. No druse greater or equal in size to 125 µm was seen. Pigmentary changes are rare.

Different cellular p16(INK4a) localisation may signal different survival outcomes in head and neck cancer.

BACKGROUND: Recently, the management of head and neck squamous cell carcinoma (HNSCC) has focused considerable attention on biomarkers, which may influence outcomes. Tests for human papilloma infection, including direct assessment of the virus as well as an associated tumour suppressor gene p16, are considered reproducible. Tumours from familial melanoma syndromes have suggested that nuclear localisation of p16 might have a further role in risk stratification. We hypothesised p16 staining that considered nuclear localisation might be informative for predicting outcomes in a broader set of HNSCC tumours not limited to the oropharynx, human papilloma virus (HPV) status or by smoking status. METHODS: Patients treated for HNSCC from 2002 to 2006 at UNC (University of North Carolina at Chapel Hill) hospitals that had banked tissue available were eligible for this study. Tissue microarrays (TMA) were generated in triplicate. Immunohistochemical (IHC) staining for p16 was performed and scored separately for nuclear and cytoplasmic staining. Human papilloma virus staining was also carried out using monoclonal antibody E6H4. p16 expression, HPV status and other clinical features were correlated with progression-free (PFS) and overall survival (OS). RESULTS: A total of 135 patients had sufficient sample for this analysis. Median age at diagnosis was 57 years (range 20-82), with 68.9% males, 8.9% never smokers and 32.6% never drinkers. Three-year OS rate and PFS rate was 63.0% and 54.1%, respectively. Based on the p16 staining score, patients were divided into three groups: high nuclear, high cytoplasmic staining group (HN), low nuclear, low cytoplasmic staining group (LS) and high cytoplasmic, low nuclear staining group (HC). The HN and the LS groups had significantly better OS than the HC group with hazard ratios of 0.10 and 0.37, respectively, after controlling for other factors, including HPV status. These two groups also had significantly better PFS than the HC staining group. This finding was consistent for sites outside the oropharynx and did not require adjustment for smoking status. CONCLUSION: Different p16 protein localisation suggested different survival outcomes in a manner that does not require limiting the biomarker to the oropharynx and does not require assessment of smoking status.

Verteporfin photodynamic therapy for neovascular age-related macular degeneration: cohort study for the UK.

OBJECTIVES: The verteporfin photodynamic therapy (VPDT) cohort study aimed to answer five questions: (a) is VPDT in the NHS provided as in randomised trials?; (b) is 'outcome' the same in the nhs as in randomised trials?; (c) is 'outcome' the same for patients ineligible for randomised trials?; (d) is VPDT safe when provided in the NHS?; and (e) how effective and cost-effective is VPDT? DESIGN: Treatment register. SETTING: All hospitals providing VPDT in the NHS. PARTICIPANTS: All patients attending VPDT clinics. INTERVENTIONS: Infusion of verteporfin followed by infrared laser exposure is called VPDT, and is used to treat neovascular age-related macular degeneration (nAMD). The VPDT cohort study advised clinicians to follow patients every 3 months during treatment or active observation, retreating based on criteria used in the previous commercial 'TAP' (Treatment of Age-related macular degeneration with Photodynamic therapy) trials of VPDT. MAIN OUTCOME MEASURES: The primary outcome was logarithm of the minimum angle of resolution monocular best-corrected distance visual acuity (BCVA). Secondary outcomes were adverse reactions and events; morphological changes in treated nAMD (wet) lesions; and for a subset of patients, 6-monthly contrast sensitivity, generic and visual health-related quality of life (HRQoL) and resource use. Treated eyes were classified as eligible for the TAP trials (EFT), ineligible (IFT) or unclassifiable (UNC). RESULTS: Forty-seven hospitals submitted data for 8323 treated eyes in 7748 patients; 4919 eyes in 4566 patients were treated more than 1 year before the last data submission or had completed treatment. Of 4043 eyes with nAMD in 4043 patients, 1227 were classified as EFT, 1187 as IFT and 1629 as UNC. HRQoL and resource use data were available for about 2000 patients. The mean number of treatments in years 1 and 2 was 2.3 and 0.4 respectively. About 50% of eyes completed treatment within 1 year. BCVA deterioration in year 1 did not differ between eligibility groups. EFT eyes lost 11.6 letters (95% confidence interval 10.1 to 13.0 letters) compared with 9.9 letters in VPDT-treated eyes in the TAP trials. EFT eyes had poorer BCVA at baseline than IFT and UNC eyes. Adverse reactions and events were reported for 1.4% of first visits - less frequently than those reported in the TAP trials. Associations between BCVA in the best-seeing eye with HRQoL and community health and social care resource use showed that the 11-letter difference in BCVA between VPDT and sham treatment in the TAP trials corresponded to differences in utility of 0.012 and health and social service costs of £60 and £92 in years 1 and 2, respectively. VPDT provided an incremental cost per quality-adjusted life-year (QALY) of £170,000 over 2 years. CONCLUSIONS: VPDT was administered less frequently than in the TAP trials, with less than half of those treated followed up for > 1 year in routine clinical practice. Deterioration in BCVA over time in EFT eyes was similar to that in the TAP trials. The similar falls in BCVA after VPDT across the pre-defined TAP eligibility groups do not mean that the treatment is equally effective in these groups because deterioration in BCVA can be influenced by the parameters that determined group membership. Safety was no worse than in the TAP trials. The estimated cost per QALY was similar to the highest previous estimate. Although VPDT is no longer in use as monotherapy for neovascular AMD, its role as adjunctive treatment has not been fully explored. VPDT also has potential as monotherapy in the management of vascular malformations of the retina and choroid and with trials underway in neovascularisation due to myopia and polypoidal choroidopathy. FUNDING: The National Institute for Health Research Health Technology Assessment programme.

Further validation of the Daily Living Tasks Dependent on Vision: identification of domains.

AIM: To examine the Daily Living Tasks Dependent on Vision (DLTV), a visual function questionnaire for domain structure, and redundancy. METHOD: 235 subjects underwent full ophthalmic assessment and completed the DLTV questionnaire by interview. Principal component analysis with varimax rotation and item response theory (IRT) were used to assign the items to domains. The internal consistency of each domain was examined using Cronbach's alpha. Redundancy was assessed by regressing each item in a domain against the remainder of items in that domain. RESULTS: Four domains were identified. Domain 1 was formed by nine items, which after applying IRT were seen to be among the most difficult questions in the instrument. Domain 2 contained eight items, all of which fell in the easier half of the instrument on applying IRT. Domain 3 contained only three items, all of which were among the easier questions and appear to deal with peripheral vision function. Domain 4 consisted of two items dealing with adaptation to light and dark conditions. Cronbach's alpha for each domain was 0.96, 0.93, 0.73, 0.66. Redundancy was found to be present in domain 1, which was therefore reduced by two items, with little effect on internal consistency. CONCLUSIONS: The authors believe using the domains identified in this report will optimise the information provided by patients on their ability to function on visually demanding tasks.

Morphometric analysis of angiograms of exudative lesions in age-related macular degeneration.

OBJECTIVES: To analyze the morphometric composition of lesion components in exudative age-related macular degeneration and to study the relationships between individual lesion components and choroidal neovascularization (CNV) subtype, at 2 time points. METHODS: Morphometric analysis of 98 sets of angiograms separated by an interval of at least 3 weeks, with no treatment delivered in the intervening period between angiograms. Area measurements of individual lesion components were made from digitally captured angiograms. Choroidal neovascularizations were classified into subtypes based on the proportions of classic CNV. Fully corrected distance visual acuity measured on logMAR Early Treatment of Diabetic Retinopathy Study charts was available at baseline and at a subsequent visit in 78 subjects. Data were analyzed using parametric and nonparametric tests, linear regression, and McNemar test of equal proportions. RESULTS: Wholly and predominantly classic CNVs were significantly smaller at initial presentation than minimally classic or occult with no classic CNVs. Lesions containing blood and lipid were also significantly larger than lesions not exhibiting these features. Lesions containing any classic CNV expanded at a significantly greater rate than lesions without classic CNV. Approximately 40% of lesions categorized as wholly classic CNV converted to predominantly classic CNV between baseline and the next follow-up visit. CONCLUSION: The presence of classic leakage in exudative age-related macular degeneration is the most important risk factor for rapid expansion of CNV.

CNV subtype in first eyes predicts severity of ARM in fellow eyes.

AIM: To examine the relation between the type of choroidal neovascularisation (CNV) in the first eye and age related maculopathy (ARM) severity in the fellow eye. METHODS: Colour fundus photographs and fluorescein angiograms from 67 subjects with a clinical diagnosis of CNV in one eye were scrutinised. CNV was classified as wholly classic, predominantly classic, minimally classic, or occult based on the proportion of classic leakage within the lesion. ARM changes in the fellow eye were assigned a severity stage using the system described by the Rotterdam Eye Study. Logistic regression analysis was employed to examine the association between CNV subtype and ARM stage. RESULTS: Of subjects with classic or predominantly classic CNV in the first eye 78% exhibited least no or early ARM features in the fellow eye. By contrast, 85% of subjects with minimally classic or occult CNV in the first eye exhibited more advanced ARM features in the fellow eye. Kruskall-Wallis one way ANOVA by ranks showed that this was highly significant (p = 0.002). Logistic regression analysis showed that as the proportion of occult CNV increased in the first eye, fellow eyes of subjects in this category were more likely to have been assigned to a higher ARM stage (p = 0.019). The area occupied by the CNV in the first eye also influenced severity of ARM changes in the fellow eye. CONCLUSION: The type and extent of CNV in the first affected eye has a distinct relation to ARM severity in the fellow eye. Fellow eyes of subjects with minimally classic or occult CNV in the first affected eye show widespread ARM changes suggestive of retinal pigment epithelial dysfunction. These findings suggest that classic CNV may be focal disease while occult CNV is essentially a more widespread retinal pigment epithelial disorder.

Cryopreservation of intact human articular cartilage.

Damaged articular cartilage (AC) impairs joint function and many treatment techniques are being investigated to determine their long term results. Successful cryopreservation of AC can provide a reliable source of intact matrix with viable chondrocytes to maintain the cartilage over long periods of time. This study investigated the application of an established cryopreservation protocol to determine the recovery of intact chondrocytes from human AC. Ten millimeter diameter osteochondral dowels were harvested from two human donors. The cryopreservation protocol was performed and the samples were rapidly warmed from varying experimental holding temperatures (-10, -20, -30, -40 degrees C), with and without plunging into liquid nitrogen, using 1 M dimethyl sulfoxide as cryoprotectant. The cartilage was stained with membrane integrity dyes and viewed under fluorescence microscopy. The percent of intact chondrocytes was compared to fresh controls. Low recovery of intact chondrocytes was recorded from all temperature levels with and without cryoprotectant. The results of this experiment demonstrated that the cryopreservation procedure used to achieve moderate success with intact sheep AC was not successful with intact human AC and further investigation is required.

Flounder antifreeze peptides increase the efficacy of cryosurgery.

Type I antifreeze protein (AFP) from the winter flounder (Pseudopleuronectes americanus) was used as an adjuvant to cryosurgery of subcutaneous tumors of Dunning AT-1 rat prostate cells grown in Copenhagen rats. The cryosurgical procedure was performed with a commercially available cryosurgery device (CRYO-HIT, Galil Medical) with clinically relevant single- and double-freeze protocols. Injury was assessed with the alamar blue indicator of metabolic activity. The assay gave anomalous results when used to assess the extent of injury immediately following the procedure, underestimating the extent of injury. However, a double-freeze procedure with antifreeze protein present was found to give significantly better ablation than a double-freeze without AFP or a single-freeze with or without AFP.

Oxidative stress and reactive nitrogen species generation during renal ischemia.

Previous evidence suggests that both oxygen radicals and nitric oxide (NO) are important mediators of injury during renal ischemia-reperfusion (I-R) injury. However, the generation of reactive nitrogen species (RNS) has not been evaluated in this model at early time points. The purpose of these studies was to examine the development of oxidant stress and the formation of RNS during I-R injury. Male Sprague-Dawley rats were anesthetized and subjected to 40 min of bilateral renal ischemia followed by 0, 3, or 6 h of reperfusion. Control animals received a sham operation. Plasma urea nitrogen and creatinine levels were monitored as markers of renal injury. Glutathione (GSH) oxidation and 4-hydroxynonenal (4-HNE)-protein adducts were used as markers of oxidant stress. 3-Nitrotyrosine (3-NT) was used as a biomarker of RNS formation. Significant increases in plasma creatinine concentrations and urea nitrogen levels were found following both 3 and 6 h of reperfusion. Increases in GSH oxidation, 4-HNE-protein adduct levels, and 3-NT levels were observed following 40 min of ischemia with no reperfusion. Since these results suggested RNS generation during the 40 min of ischemia, a time course of RNS generation following 0, 5, 10, 20, and 40 min of ischemia was evaluated. Significant increases in 3-NT generation was detected as early as 10 min of ischemia and rose to values nearly 10-fold higher than Control at 40 min of ischemia. No additional increase was observed following reperfusion. The data clearly demonstrate that oxidative stress and RNS generation occur in the kidney during ischemia.

Simultaneous optimization of cryoprobe placement and thermal protocol for cryosurgery.

We demonstrate that it is possible to simultaneously optimize multiple cryoprobe placements and their thermal protocol for one freeze-thaw cycle. A numerical optimization algorithm is used and three different forms of objective function are examined in terms of algorithm convergence rate, minimum value of the chosen objective function, temperature-volume histograms and isotherm distributions. The optimization results depend on the initial values of the variables, the form of the objective function, optimization goals and the mathematical method adopted for gradient calculation. The proposed optimization model offers significant advantages over the previously reported semi-empirical approach to conformal cryotherapy, such as the ability to handle an unlimited number of variables and eliminating the need for the user input between iterations, thereby reducing, if not removing, the subjectivity of cryosurgery treatment planning.

A model for the time dependent three-dimensional thermal distribution within iceballs surrounding multiple cryoprobes.

A time dependent three-dimensional finite difference model of iceball formation about multiple cryoprobes has been developed and compared to experimental data. Realistic three-dimensional probe geometry is specified and the number of cryoprobes, the cryoprobe cooling rates, and the locations of the probes are arbitrary inputs by the user. The simulation accounts for observed longitudinal thermal gradients along the cryoprobe tips. Thermal histories for several points around commercially available cryoprobes have been predicted within experimental error for one, three, and five probe configurations. The simulation can be used to generate isotherms within the iceball at arbitrary times. Volumes enclosed by the iceball and any isotherms may also be computed to give the ablative ratio, a measure of the iceball's killing efficiency. This ratio was calculated as the volume enclosed by a critical isotherm divided by the total volume of the iceball for assumed critical temperatures of -20 and -40 degrees C. The ablative ratio for a single probe is a continuously decreasing function of time but when multiple probe configurations are used the ablative ratio increases to a maximum and then essentially plateaus. Maximum values of 0.44 and 0.55 were observed for three and five probe configurations, respectively, with an assumed critical temperature of -20 degrees C. Assuming a critical temperature of -40 degrees C, maximum ablative ratios of 0.21 and 0.3 for three and five probe configurations, respectively, were observed.

Evidence of chondrocyte repopulation in adult ovine articular cartilage following cryoinjury and long-term transplantation.

OBJECTIVE: To characterize the response of articular chondrocytes to a specific cryoinjury that leads to cluster formation following long-term transplantation. DESIGN: Osteochondral dowels from 20 adult sheep were cryopreserved to optimize the recovery of chondrocytes immediately after thawing. The dowels were transplanted as allografts and observed at 3 and 12 months. Chondrocyte distribution and viability was assessed using paravital dyes after transplantation. Chondrocyte phenotype was assessed by in situ hybridization and immunohistochemistry to detect type II collagen. An anticentrosome antibody was used to identify cells undergoing cell cycle progression towards mitosis. RESULTS: All cryopreserved grafts showed the presence of spheroidal clusters of chondrocytes 1 year after transplantation while the host cartilage adjacent to the graft appeared morphologically normal. The average size of the clusters increased from four cells at 3 months to 12 cells at 1 year. The chondrocytes in the clusters displayed newly formed type II collagen protein and mRNA. Some cells within clusters were observed with two centrosomes, indicative of cells progressing through the S phase of the cell cycle. CONCLUSION: Adult articular chondrocytes retain the ability to repopulate the matrix, an ability which is demonstrated with this specific cryoinjury. This may be an initial stage of cartilage regeneration.

Transplantation of articular cartilage following a step-cooling cryopreservation protocol.

Using a step-cooling cryopreservation protocol that held the tissue 60 min at -4 degrees C, 30 min at -8 degrees C, and 10 min at -40 degrees C before plunging into liquid nitrogen, we were able to get a substantial improvement in the magnitude and pattern of chondrocyte recovery following cryopreservation, achieving postthaw recoveries of 62 +/- 13%. These results are consistent with the hypothesis that ice growth within articular cartilage is planar, but they provide no direct support for that hypothesis. Transplanting (step-cooled) cryopreserved osteochondral allografts into adult Suffolk/Romanoff crossbred sheep for periods of 3 months and 1 year further tested the efficacy of the cryopreservation protocol. Unfortunately, the cryoinjury sustained by the chondrocytes during cryopreservation, although apparently nonlethal immediately after thawing in many cases, was not innocuous in the long term. The presence of large clusters of chondrocytes at 1 year after transplantation illustrates that cryoinjury not detectable with a membrane integrity assay can still have far-reaching effects on transplanted tissue.

Kinetics of osmotic water movement from rabbit patellar tendon and medial collateral ligament fibroblasts.

The present study is part of a program to optimize the cryopreservation ligament and tendon allografts for the biological remodeling that occurs following transplantation. The osmotic behavior of fibroblasts from the medial collateral ligament (MCL) and the patellar tendon (PT) of new zealand white rabbits was measured to obtain the hydraulic conductivity (and its temperature dependence) as well as the osmotically inactive volume. MCL fibroblasts were found to have an isotonic cell volume of 3800 (m(3), an osmotically inactive volume of 1300 (microm(3), and a hydraulic conductivity of 0.56 (microm/min/atm at 20 degrees C with an activation energy of 10.9 kcal/mol. PT fibroblasts were found to have an isotonic cell volume of 6300 (microm(3), an osmotically inactive volume of 2000 (microm(3), and a hydraulic conductivity of 0.71 (m/min/atm at 20 degrees C with an activation energy of 10.1 kcal/mol.

A semi-empirical treatment planning model for optimization of multiprobe cryosurgery.

A model is presented for treatment planning of multiprobe cryosurgery. In this model a thermal simulation algorithm is used to generate temperature distribution from cryoprobes, visualize isotherms in the anatomical region of interest (ROI) and provide tools to assist estimation of the amount of freezing damage to the target and surrounding normal structures. Calculations may be performed for any given freezing time for the selected set of operation parameters. The thermal simulation is based on solving the transient heat conduction equation using finite element methods for a multiprobe geometry. As an example, a semi-empirical optimization of 2D placement of six cryoprobes and their thermal protocol for the first freeze cycle is presented. The effectiveness of the optimized treatment protocol was estimated by generating temperature-volume histograms and calculating the objective function for the anatomy of interest. Two phantom experiments were performed to verify isotherm locations predicted by calculations. A comparison of the predicted 0 degrees C isotherm with the actual iceball boundary imaged by x-ray CT demonstrated a spatial agreement within +/-2 mm.

Suppression of high-density artefacts in x-ray CT images using temporal digital subtraction with application to cryotherapy.

Image guidance in cryotherapy is usually performed using ultrasound. Although not currently in routine clinical use, x-ray CT imaging is an alternative means of guidance that can display the full 3D structure of the iceball, including frozen and unfrozen regions. However, the quality of x-ray CT images is compromised by the presence of high-density streak artefacts. To suppress these artefacts we applied temporal digital subtraction (TDS). This TDS method has the added advantage of improving the grey scale contrast between frozen and unfrozen tissue in the CT images. Two sets of CT images were taken of a phantom material, cryoprobes and a urethral warmer (UW) before and during the cryoprobe freeze cycle. The high density artefacts persisted in both image sets. TDS was performed on these two image sets using the corresponding mask image of unfrozen material and the same geometrical configuration of the cryoprobes and the UW. The resultant difference image had a significantly reduced artefact content. Thus TDS can be used to significantly suppress or eliminate high-density CT streak artefacts without reducing the metallic content of the cryoprobes. In vivo study needs to be conducted to establish the utility of this TDS procedure for CT assisted prostate or liver cryotherapy. Applying TDS in x-ray CT guided cryotherapy will facilitate estimation of the number and location of all frozen and unfrozen regions, potentially making cryotherapy safer and less operator dependent.

Cryobiology of articular cartilage: ice morphology and recovery of chondrocytes.

The cryopreservation of articular cartilage chondrocytes has been achieved with cells isolated from the cartilage matrix but has found only limited success when the tissue is left intact. Previous work with ovine cartilage has shown that cryopreservation of the chondrocytes of the superficial and deep zones is possible, but the cells of the intermediate zone have not been successfully cryopreserved. This finding led to the suggestion that there might be biological differences between chondrocytes of the different morphological zones that were responsible for this differential recovery. This study investigates the hypothesis that the cells of the intermediate zone are more sensitive to cryoinjury by introducing cuts in the cartilage so that cells of the intermediate zone have the same proximity to the outer surface of the tissue as the cells of the superficial zone. When this was done, it was found that cells of the intermediate zone could survive cryopreservation as well as the cells of the superficial zone when they were near a surface, but not when they were embedded deep within the tissue. Thus the hypothesis of a biological difference between the cells of the two zones being responsible for the differential recovery is disproved. It is further hypothesized that physical proximity to a surface leads to higher recovery as a result of planar ice growth into the cartilage.

Transplantation of cryopreserved osteochondral Dowel allografts for repair of focal articular defects in an ovine model.

The purpose of this study was to test whether successful cryopreservation of osteochondral tissue is possible and whether, with the appropriate surgical procedure, it can be used for the successful repair of focal articular defects within joints. Fresh (nonfrozen) and snap-frozen (plunged in liquid nitrogen and thawed in a water bath at 37 degrees C, repeated three times) autografts were used as positive and negative controls, respectively. Snap-frozen, frozen (fresh tissue placed in a freezer at -80 degrees C), and cryopreserved (immersed in 10% dimethyl sulfoxide for 30 minutes and then frozen at 1 degrees C/min to -80 degrees C) allografts were transplanted into the knees of adult sheep. Outcomes were evaluated 3, 6, and 12 months after transplantation. The morphological, histological, biochemical, and biomechanical behaviors and characteristics of the graft cartilage, the host cartilage adjacent to the grafts, and the opposing tibial cartilage were assessed. Freezing protocols that yielded poor chondrocyte recovery after thawing (frozen and snap-frozen) resulted in poor overall graft outcome. The cryopreservation protocol, however, resulted in intermediate recovery (50%) of chondrocytes and in intermediate overall graft outcome compared with fresh autografts. The membrane integrity of the allograft chondrocytes immediately following cryopreservation was identified as the most reliable predictor of long-term outcome of the graft. Further improvements in cryopreservation technique may lead to an effective method of banking osteochondral tissue for successful transplantation for the repair of focal defects and larger joint reconstructions.

Articular cartilage joint surface reconstruction techniques.

There is renewed interest in joint surface reconstruction using a variety of new and evolving techniques for articular cartilage resurfacing. Neochondrogenesis and articular cartilage transplantation are gaining a prominent place in orthopaedic basic science research. The authors have published a reliable, repeatable, stable, and sensitive model utilizing osteochondral dowel core transplantation in an ovine model to assess various treatment and follow-up evaluation techniques for articular cartilage transplantation. As well, our laboratory has developed a handheld articular cartilage indentor for clinical assessment of biomechanical performance of joint surfaces. This article presents and reviews that model as well as a semiquantitative visual analog scale for documenting articular cartilage gross morphology. The results of magnetic resonance imaging of the osteochondral dowel transplants and the gross morphology grading are compared to the histological and histochemical grading and biochemical and biomechanical assessments to form the foundation for future work in this critical and important study area for clinical application.