Histological and Radiological Assessment of Endogenously Generated Repair Tissue In Vivo Following a Chondral Harvest.

OBJECTIVE: To examine repair tissue formed approximately 15 months after a chondral harvest in the human knee. DESIGN: Sixteen individuals (12 males, 4 females, mean age 36 ± 9 years) underwent a chondral harvest in the trochlea as a pre-requisite for autologous chondrocyte implantation (ACI) treatment. The harvest site was assessed via MRI at 14.3 ± 3.2 months and arthroscopy at 15 ± 3.5 months (using the Oswestry Arthroscopy Score [O-AS] and the International Cartilage Repair Society Arthroscopy Score [ICRS-AS]). Core biopsies (1.8 mm diameter, n = 16) of repair tissue obtained at arthroscopy were assessed histologically (using the ICRS II and OsScore histology scores) and examined via immunohistochemistry for the presence of collagen types I and II. RESULTS: The mean O-AS and ICRS-AS of the repaired harvest sites were 7.2 ± 3.2 and 10.1 ± 3.5, respectively, with 80.3% ± 26% repair fill depth on MRI. The histological quality of the repair tissue formed was variable, with some hyaline cartilage present in 50% of the biopsies; where this occurred, it was associated with a significantly higher ICRS-AS than those with no hyaline cartilage present (median 11 vs. 7.5, P = 0.049). Collagen types I and II were detected in 12/14 and 10/13 biopsies, respectively. CONCLUSIONS: We demonstrate good-quality structural repair tissue formed following cartilage harvest in ACI, suggesting this site can be useful to study endogenous cartilage repair in humans. The trochlea is less commonly affected by osteoarthritis; therefore, location may be critical for spontaneous repair. Understanding the mechanisms and factors influencing this could improve future treatments for cartilage defects.

Combined Autologous Chondrocyte and Bone Marrow Mesenchymal Stromal Cell Implantation in the Knee: An 8-year Follow Up of Two First-In-Man Cases.

Autologous chondrocyte implantation (ACI) has been used to treat cartilage defects for >20 years, with promising clinical outcomes. Here, we report two first-in-man cases (patient A and B) treated with combined autologous chondrocyte and bone marrow mesenchymal stromal cell implantation (CACAMI), with 8-year follow up. Two patients with International Cartilage Repair Society (ICRS) grade III-IV cartilage lesions underwent a co-implantation of autologous chondrocytes and bone marrow-derived mesenchymal stromal cells (BM-MSCs) between February 2008 and October 2009. In brief, chondrocytes and BM-MSCs were separately isolated and culture-expanded in a good manufacturing practice laboratory for a period of 2-4 weeks. Cells were then implanted in combination into cartilage defects and patients were clinically evaluated preoperatively and postoperatively, using the self-reported Lysholm knee score and magnetic resonance imaging (MRI). Postoperative Lysholm scores were compared with the Oswestry risk of knee arthroplasty (ORKA) scores. Patient A also had a second-look arthroscopy, at which time a biopsy of the repair site was taken. Both patients demonstrated a significant long-term improvement in knee function, with postoperative Lysholm scores being consistently higher than ORKA predictions. The most recent Lysholm scores, 8 years after surgery were 100/100 (Patient A) and 88/100 (Patient B), where 100 represents a fully functioning knee joint. Bone marrow lesion (BML) volume was shown to decrease on postoperative MRIs in both patients. Cartilage defect area increased in patient A, but declined initially for patient B, slightly increasing again 2 years after treatment. The repair site biopsy taken from patient A at 14 months postoperatively, demonstrated a thin layer of fibrocartilage covering the treated defect site. The use of a combination of cultured autologous chondrocytes and BM-MSCs appears to confer long-term benefit in this two-patient case study. Improvements in knee function perhaps relate to the observed reduction in the size of the BML.

Human Articular Chondrocytes Retain Their Phenotype in Sustained Hypoxia While Normoxia Promotes Their Immunomodulatory Potential.

OBJECTIVE: To assess the phenotype of human articular chondrocytes cultured in normoxia (21% O2) or continuous hypoxia (2% O2). DESIGN: Chondrocytes were extracted from patients undergoing total knee replacement (n = 5) and cultured in ~21% (normoxic chondrocytes, NC) and 2% (hypoxic chondrocytes, HC) oxygen in both monolayer and 3-dimensional (3D) pellet culture and compared with freshly isolated chondrocytes (FC). Cells were assessed by flow cytometry for markers indicative of mesenchymal stromal cells (MSCs), chondrogenic-potency and dedifferentiation. Chondrogenic potency and immunomodulatory gene expression was assessed in NC and HC by reverse transcription quantitative polymerase chain reaction. Immunohistochemistry was used to assess collagen II production following 3D pellet culture. RESULTS: NC were positive (>97%, n = 5) for MSC markers, CD73, CD90, and CD105, while HC demonstrated <90% positivity (n = 4) and FC (n = 5) less again (CD73 and CD90 <20%; CD105 <40%). The markers CD166 and CD151, indicative of chondrogenic de-differentiation, were significantly higher on NC compared with HC and lowest on FC. NC also produced the highest levels of CD106 and showed the greatest levels of IDO expression, following interferon-γ stimulation, indicating immunomodulatory potential. NC produced the highest levels of CD49c (>60%) compared with HC and FC in which production was <2%. Hypoxic conditions upregulated expression of SOX9, frizzled-related protein (FRZB), fibroblast growth factor receptor 3 (FGFR3), and collagen type II (COL2A1) and downregulated activin receptor-like kinase 1 (ALK1) in 3 out of 4 patients compared with normoxic conditions for monolayer cells. CONCLUSIONS: Hypoxic conditions encourage retention of a chondrogenic phenotype with some immunomodulatory potential, whereas normoxia promotes dedifferentiation of chondrocytes toward an MSC phenotype with loss of chondrogenic potency but enhanced immunomodulatory capacity.

Predictors of fracture healing in patients with recalcitrant nonunions treated with autologous culture expanded bone marrow-derived mesenchymal stromal cells.

The study reports the prospective outcome of treating severe recalcitrant fracture nonunion in patients with autologous bone marrow-derived mesenchymal stromal cells (BMSC) from 2003 to 2010 and analyze predictors of union. Autologous BMSC were culture expanded and inserted at nonunion site with or without carriers in addition to surgical stabilization of the fracture. Radiological union was ascertained by musculoskeletal radiologists on plain radiographs and/or CT scans. A logistic regression analysis was performed with cell-expansion parameters (cell numbers, cell doubling time) and known clinical factors (e.g., smoking and diabetes) as independent variables and fracture union as the dependent variable to identify the factors that influence bony healing. An Eq5D index score assessed the effect of treatment on general quality of health. A total of 35 patients (mean age 51+/-13 years) with established nonunion (median 2.9 years, 1-33) and, at least one failed nonunion surgery (median 4,1-14) received treatment. Fracture union was achieved in 21 patients (60%; 95%CI 44-75) at 2.6 years. Multiple penalized logistic regression revealed faster cell doubling time (p = 0.07), absence of diabetes (p = 0.003), less previous surgeries (p = 0.008), and lower age at cell implantation (p = 0.02) were significant predictors for fracture union. A significant increase in Eq5D index (p = 0.01) was noted with a mean rise of the score by 0.34 units (95%CI 0.11-0.58) at 1 year following the study. In summary, the study revealed cell doubling time as a novel in vitro parameter in conjunction with age, multiple surgeries, and diabetes as being significant predictors of the fracture union. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. J Orthop Res 37:1303-1309, 2019.

Magnetic Resonance Imaging Parameters at 1 Year Correlate With Clinical Outcomes Up to 17 Years After Autologous Chondrocyte Implantation.

BACKGROUND: The ability to predict the long-term success of surgical treatment in orthopaedics is invaluable, particularly in clinical trials. The quality of repair tissue formed 1 year after autologous chondrocyte implantation (ACI) in the knee was analyzed and compared with clinical outcomes over time. HYPOTHESIS: Better quality repair tissue and a better appearance on magnetic resonance imaging (MRI) 1 year after ACI lead to improved longer-term clinical outcomes. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Repair tissue quality was assessed using either MRI (11.5 ± 1.4 [n = 91] or 39.2 ± 18.5 [n = 76] months after ACI) or histology (16.3 ± 11.0 months [n = 102] after ACI). MRI scans were scored using the whole-organ magnetic resonance imaging score (WORMS) and the magnetic resonance observation of cartilage repair tissue (MOCART) score, with additional assessments of subchondral bone marrow and cysts. Histology of repair tissue was performed using the Oswestry cartilage score (OsScore) and the International Cartilage Repair Society (ICRS) II score. Clinical outcomes were assessed using the modified Lysholm score preoperatively, at the time of MRI or biopsy, and at a mean 8.4 ± 3.7 years (maximum, 17.8 years) after ACI. RESULTS: At 12 months, the total MOCART score and some of its individual parameters correlated significantly with clinical outcomes. The degree of defect fill, overall signal intensity, and surface of repair tissue at 12 months also significantly correlated with longer-term outcomes. The presence of cysts or effusion (WORMS) significantly correlated with clinical outcomes at 12 months, while the presence of synovial cysts/bursae preoperatively or the absence of loose bodies at 12 months correlated significantly with long-term clinical outcomes. Thirty percent of repair tissue biopsies contained hyaline cartilage, 65% contained fibrocartilage, and 5% contained fibrous tissue. Despite no correlation between the histological scores and clinical outcomes at the time of biopsy, a lack of hyaline cartilage or poor basal integration was associated with increased pain; adhesions visible on MRI also correlated with significantly better histological scores. CONCLUSION: These results demonstrate that MRI at 12 months can predict longer-term clinical outcomes after ACI. Further investigation regarding the presence of cysts, effusion, and adhesions and their relationship with histological and clinical outcomes may yield new insights into the mechanisms of cartilage repair and potential sources of pain.

Two independent proteomic approaches provide a comprehensive analysis of the synovial fluid proteome response to Autologous Chondrocyte Implantation.

BACKGROUND: Autologous chondrocyte implantation (ACI) has a failure rate of approximately 20%, but it is yet to be fully understood why. Biomarkers are needed that can pre-operatively predict in which patients it is likely to fail, so that alternative or individualised therapies can be offered. We previously used label-free quantitation (LF) with a dynamic range compression proteomic approach to assess the synovial fluid (SF) of ACI responders and non-responders. However, we were able to identify only a few differentially abundant proteins at baseline. In the present study, we built upon these previous findings by assessing higher-abundance proteins within this SF, providing a more global proteomic analysis on the basis of which more of the biology underlying ACI success or failure can be understood. METHODS: Isobaric tagging for relative and absolute quantitation (iTRAQ) proteomic analysis was used to assess SF from ACI responders (mean Lysholm improvement of 33; n = 14) and non-responders (mean Lysholm decrease of 14; n = 13) at the two stages of surgery (cartilage harvest and chondrocyte implantation). Differentially abundant proteins in iTRAQ and combined iTRAQ and LF datasets were investigated using pathway and network analyses. RESULTS: iTRAQ proteomic analysis confirmed our previous finding that there is a marked proteomic shift in response to cartilage harvest (70 and 54 proteins demonstrating ≥ 2.0-fold change and p < 0.05 between stages I and II in responders and non-responders, respectively). Further, it highlighted 28 proteins that were differentially abundant between responders and non-responders to ACI, which were not found in the LF study, 16 of which were altered at baseline. The differential expression of two proteins (complement C1s subcomponent and matrix metalloproteinase 3) was confirmed biochemically. Combination of the iTRAQ and LF proteomic datasets generated in-depth SF proteome information that was used to generate interactome networks representing ACI success or failure. Functional pathways that are dysregulated in ACI non-responders were identified, including acute-phase response signalling. CONCLUSIONS: Several candidate biomarkers for baseline prediction of ACI outcome were identified. A holistic overview of the SF proteome in responders and non-responders to ACI  has been profiled, providing a better understanding of the biological pathways underlying clinical outcome, particularly the differential response to cartilage harvest in non-responders.

Autologous chondrocyte implantation-derived synovial fluids display distinct responder and non-responder proteomic profiles.

BACKGROUND: Autologous chondrocyte implantation (ACI) can be used in the treatment of focal cartilage injuries to prevent the onset of osteoarthritis (OA). However, we are yet to understand fully why some individuals do not respond well to this intervention. Identification of a reliable and accurate biomarker panel that can predict which patients are likely to respond well to ACI is needed in order to assign the patient to the most appropriate therapy. This study aimed to compare the baseline and mid-treatment proteomic profiles of synovial fluids (SFs) obtained from responders and non-responders to ACI. METHODS: SFs were derived from 14 ACI responders (mean Lysholm improvement of 33 (17-54)) and 13 non-responders (mean Lysholm decrease of 14 (4-46)) at the two stages of surgery (cartilage harvest and chondrocyte implantation). Label-free proteome profiling of dynamically compressed SFs was used to identify predictive markers of ACI success or failure and to investigate the biological pathways involved in the clinical response to ACI. RESULTS: Only 1 protein displayed a ≥2.0-fold differential abundance in the preclinical SF of ACI responders versus non-responders. However, there is a marked difference between these two groups with regard to their proteome shift in response to cartilage harvest, with 24 and 92 proteins showing ≥2.0-fold differential abundance between Stages I and II in responders and non-responders, respectively. Proteomic data has been uploaded to ProteomeXchange (identifier: PXD005220). We have validated two biologically relevant protein changes associated with this response, demonstrating that matrix metalloproteinase 1 was prominently elevated and S100 calcium binding protein A13 was reduced in response to cartilage harvest in non-responders. CONCLUSIONS: The differential proteomic response to cartilage harvest noted in responders versus non-responders is completely novel. Our analyses suggest several pathways which appear to be altered in non-responders that are worthy of further investigation to elucidate the mechanisms of ACI failure. These protein changes highlight many putative biomarkers that may have potential for prediction of ACI treatment success.

Efficacy and safety of autologous cell therapies for knee cartilage defects (autologous stem cells, chondrocytes or the two): randomized controlled trial design.

AIM: The main aim of this trial is to test the safety and efficacy of autologous stromal/stem cells, chondrocytes or the two combined in the treatment of knee cartilage defects. PATIENTS & METHODS: Patients with symptomatic chondral/osteochondral defects will be randomized to cell therapy treatment with one of three cell populations (1:1:1). The primary efficacy outcome is a functional knee score (Lysholm) at 15 months post-treatment and the primary safety outcome is the incidence of adverse events. Secondary objectives are to analyze repair tissues, quality of life and cost-utility assessments. Exploratory objectives are to identify predictors for success/potency and dose-response relationships. RESULTS & CONCLUSION: This trial has been carefully designed so that valuable scientific and clinical information can be gathered throughout and in the final analysis.

Development of a Tool to Predict Outcome of Autologous Chondrocyte Implantation.

Objective The study had 2 objectives: first, to evaluate the success of autologous chondrocyte implantation (ACI) in terms of incidence of surgical re-intervention, including arthroplasty, and investigate predictors of successful treatment outcome. The second objective was to derive a tool predicting a patient's arthroplasty risk following ACI. Design In this Level II, prognostic study, 170 ACI-treated patients (110 males [aged 36.8 ± 9.4 years]; 60 females [aged 38.1 ± 10.2 years]) completed a questionnaire about further surgery on their knee treated with ACI 10.9 ± 3.5 years previously. Factors commonly assessed preoperatively (age, gender, defect location and number, previous surgery at this site, and the preoperative Lysholm score) were used as independent factors in regression analyses. Results At final follow-up (maximum of 19 years post-ACI), 40 patients (23.5%) had undergone surgical re-intervention following ACI. Twenty-six patients (15.3%) underwent arthroplasty, more commonly females (25%) than males (10%; P = 0.001). Cox regression analyses identified 4 factors associated with re-intervention: age at ACI, multiple operations before ACI, patellar defects, and lower pretreatment Lysholm scores (Nagelkerke's R2 = 0.20). Six predictive items associated with risk of arthroplasty following ACI (Nagelkerke's R2 = 0.34) were used to develop the Oswestry Risk of Knee Arthroplasty index with internal cross-validation. Conclusion In a single-center study, we have identified 6 factors (age, gender, location and number of defects, number of previous operations, and Lysholm score before ACI) that appear to influence the likelihood of ACI patients progressing to arthroplasty. We have used this information to propose a formula or "tool" that could aid treatment decisions and improve patient selection for ACI.

Chondrogenic Potency Analyses of Donor-Matched Chondrocytes and Mesenchymal Stem Cells Derived from Bone Marrow, Infrapatellar Fat Pad, and Subcutaneous Fat.

Autologous chondrocyte implantation (ACI) is a cell-based therapy that has been used clinically for over 20 years to treat cartilage injuries more efficiently in order to negate or delay the need for joint replacement surgery. In this time, very little has changed in the ACI procedure, but now many centres are considering or using alternative cell sources for cartilage repair, in particular mesenchymal stem cells (MSCs). In this study, we have tested the chondrogenic potential of donor-matched MSCs derived from bone marrow (BM), infrapatellar fat pad (FP), and subcutaneous fat (SCF), compared to chondrocytes. We have confirmed that there is a chondrogenic potency hierarchy ranging across these cell types, with the most potent being chondrocytes, followed by FP-MSCs, BM-MSCs, and lastly SCF-MSCs. We have also examined gene expression and surface marker profiles in a predictive model to identify cells with enhanced chondrogenic potential. In doing so, we have shown that Sox-9, Alk-1, and Coll X expressions, as well as immunopositivity for CD49c and CD39, have predictive value for all of the cell types tested in indicating chondrogenic potency. The findings from this study have significant clinical implications for the refinement and development of novel cell-based cartilage repair strategies.

Cellular senescence in aging and osteoarthritis.

- It is well accepted that age is an important contributing factor to poor cartilage repair following injury, and to the development of osteoarthritis. Cellular senescence, the loss of the ability of cells to divide, has been noted as the major factor contributing to age-related changes in cartilage homeostasis, function, and response to injury. The underlying mechanisms of cellular senescence, while not fully understood, have been associated with telomere erosion, DNA damage, oxidative stress, and inflammation. In this review, we discuss the causes and consequences of cellular senescence, and the associated biological challenges in cartilage repair. In addition, we present novel strategies for modulation of cellular senescence that may help to improve cartilage regeneration in an aging population.

Evaluating Joint Morbidity after Chondral Harvest for Autologous Chondrocyte Implantation (ACI): A Study of ACI-Treated Ankles and Hips with a Knee Chondral Harvest.

OBJECTIVE: To establish if harvesting cartilage to source chondrocytes for autologous chondrocyte implantation (ACI) results in donor site morbidity. DESIGN: Twenty-three patients underwent ACI for chondral defects of either the ankle or the hip. This involved cartilage harvest from the knee (stage I), chondrocyte expansion in the laboratory and implantation surgery (stage II) into the affected joint. Prior to chondral harvest, no patient had sought treatment for their knee. Lysholm knee scores were completed prior to chondral harvest and annually post-ACI. Histological analyses of the donor site were performed at 12.3 ± 1.5 months for 3 additional patients who had previously had ACI of the knee. RESULTS: The median preoperative Lysholm score was 100, with no significant differences observed at either 13.7±1.7 months or 4.8±1.8 years postharvest (median Lysholm scores 91.7 and 87.5, respectively). Patients whose cartilage was harvested from the central or medial trochlea had a significantly higher median Lysholm score at latest follow-up (97.9 and 93.4, respectively), compared with those taken from the intercondylar notch (median Lysholm score 66.7). The mean International Cartilage Repair Society (ICRS) II histological score for the biopsies taken from the donor site of 3 additional knee ACI patients was 117 ± 10 (maximum score 140). CONCLUSIONS: This study suggests that the chondral harvest site in ACI is not associated with significant joint morbidity, at least up to 5 years postharvest. However, one should carefully consider the location for chondral harvest as this has been shown to affect knee function in the longer term.

Autologous Bone Plug Supplemented With Autologous Chondrocyte Implantation in Osteochondral Defects of the Knee.

BACKGROUND: Structural and functional outcome of bone graft with first- or second-generation autologous chondrocyte implantation (ACI) in treating cartilage and subchondral bone defect has not been reported previously. PURPOSE: To evaluate the outcome of simultaneous transplantation of an autologous bone plug with first- or second-generation ACI for restoration of concomitant subchondral bone and full-thickness cartilage defect in the femoral condyle of the knee. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Seventeen patients (mean ± SD age, 27 ± 7 years; range, 17-40 years)-12 with osteochondritis dissecans (International Cartilage Repair Society [ICRS] grades 3 and 4) and 5 with an isolated osteochondral defect (ICRS grade 4)-had the defect reconstructed with implantation of a unicortical autologous bone graft combined with ACI (the OsPlug technique). Functional outcome was assessed with Lysholm scores obtained preoperatively and at 1 and 5 years postoperatively. The repair site was evaluated with the Oswestry Arthroscopy Score (OAS), MOCART score (magnetic resonance observation of cartilage repair tissue), and ICRS II histology score. Formation of a subchondral lamina and lateral integration of the bone grafts were evaluated from magnetic resonance imaging scans. RESULTS: The mean defect size was 4.5 ± 2.6 cm(2) (range, 1-9 cm(2)), and the mean depth was 11.3 ± 5 mm (range, 5-18 mm). The preoperative Lysholm score improved from 45 (interquartile range [IQR], 24; range, 16-79) to 77 (IQR, 28; range, 41-100) at 1 year (P = .001) and 70 (IQR, 35; range, 33-91) at 5 years (P = .009). The mean OAS of the repair site was 6.2 (range, 0-9) at a mean of 1.3 years. The mean MOCART score was 61 ± 22 (range, 20-85) at 2.6 ± 1.8 years. Histology demonstrated generally good integration of the repair cartilage with the underlying bone. Poor lateral integration of the bone graft, as assessed on magnetic resonance imaging scan, and a low OAS were significantly associated with a poor Lysholm score and failure. A total of 3 patients had treatment failure, with 1 requiring total knee replacement at 5 years (Lysholm score of 33 at failure) and the other 2 requiring further surgical intervention because of persistent symptoms at 2 and 4 years, respectively (both had Lysholm score of 45 at failure). The Lysholm score in these patients before failure were still noted to be higher than at the preoperative level. CONCLUSION: The OsPlug technique shows significant improvement of functional outcome for up to 5 years in patients with high-grade osteochondritis dissecans or osteochondral defect. This is the first report describing association of bone graft integration with functional outcome after such a procedure. It also demonstrates histologic evidence of integration of the repair cartilage with the underlying bone graft.

Aarhus Regenerative Orthopaedics Symposium (AROS).

The combination of modern interventional and preventive medicine has led to an epidemic of ageing. While this phenomenon is a positive consequence of an improved lifestyle and achievements in a society, the longer life expectancy is often accompanied by decline in quality of life due to musculoskeletal pain and disability. The Aarhus Regenerative Orthopaedics Symposium (AROS) 2015 was motivated by the need to address regenerative challenges in an ageing population by engaging clinicians, basic scientists, and engineers. In this position paper, we review our contemporary understanding of societal, patient-related, and basic science-related challenges in order to provide a reasoned roadmap for the future to deal with this compelling and urgent healthcare problem.

Efficacy of hip resurfacing arthroplasty: 6 year results from an international multisurgeon prospective cohort study.

Metal-on-metal hip resurfacing is undertaken worldwide. This procedure helps preserve femoral bone stock and allows patients to return to high activity sports. Most outcome studies are individual surgeon case series from single centers where the results and outcomes are evaluated by the same surgeon. One method of increasing the external validity of a follow-up study is to have a multi-centre study design with independent assessment of the outcomes. We present an independent assessment of eleven year follow-up of hip resurfacing outcomes from an international hip resurfacing register. The purpose of this study was to assess: Implant survival at maximum follow-up for revision due to any reason, implant survival at maximum follow-up for revision due to major causes of failure, hip function following hip resurfacing and factors affecting hip function, effect of gender and age on hip function and implant survival, effect of femoral component size on hip function and implant survival. 4535 patients (5000 hips) entered into the registry during 1997-2002 were studied. In summary, at a maximum follow-up of 11 years hip resurfacing has a good implant survival of 96.2% and excellent post-operative function. This is excellent given the international and multisurgeon nature of this cohort where majority of the surgeons were in their learning curve.

Pre-Osteoarthritis: Definition and Diagnosis of an Elusive Clinical Entity.

OBJECTIVE: An attempt to define pre-osteoarthritis (OA) versus early OA and definitive osteoarthritis. METHODS: A group of specialists in the field of cartilage science and treatment was formed to consider the nature of OA onset and its possible diagnosis. RESULTS: Late-stage OA, necessitating total joint replacement, is the end stage of a biological process, with many previous earlier stages. Early-stage OA has been defined and involves structural changes identified by arthroscopy or radiography. The group argued that before the "early-stage OA" there must exist a stage where cellular processes, due to the presence of risk factors, have kicked into action but have not yet resulted in structural changes. The group suggested that this stage could be called "pre-osteoarthritis" (pre-OA). CONCLUSIONS: The group suggests that defining points of initiation for OA in the knee could be defined, for example, by traumatic episodes or surgical meniscectomy. Such events may set in motion metabolic processes that could be diagnosed by modern MRI protocols or arthroscopy including probing techniques before structural changes of early OA have developed. Preventive measures should preferably be applied at this pre-OA stage in order to stop the projected OA "epidemic."

Characterization of the cells in repair tissue following autologous chondrocyte implantation in mankind: a novel report of two cases.

AIM: Autologous chondrocyte implantation (ACI) is used worldwide for the treatment of cartilage defects. This study has aimed to assess for the first time the cells that are contained within human ACI repair tissues several years post-treatment. We have compared the phenotypic properties of cells from within the ACI repair with adjacent chondrocytes and subchondral bone-derived mesenchymal stromal/stem cells (MSCs). MATERIALS & METHODS: Two patients undergoing arthroplasty of their ACI-treated joint were investigated. Tissue and cells were isolated from the repair site, adjacent macroscopically normal cartilage and MSCs from the subchondral bone were characterized for their growth kinetics, morphology, immunoprofile and differentiation capacity. RESULTS: ACI repair tissue appeared fibrocartilaginous, and ACI repair cells were heterogeneous in morphology and size when freshly isolated, becoming more homogeneous, resembling chondrocytes from adjacent cartilage, after culture expansion. The same weight of ACI repair tissue resulted in less cells than macroscopically normal cartilage. During expansion, ACI repair cells proliferated faster than MSCs but slower than chondrocytes. ACI repair cell immunoprofiles resembled chondrocytes, but their differentiation capacity matched MSCs. CONCLUSION: This novel report demonstrates that human ACI repair cell phenotypes resemble both chondrocytes and MSCs but at different stages of their isolation and expansion in vitro.

Increased Production of Clusterin in Biopsies of Repair Tissue following Autologous Chondrocyte Implantation.

OBJECTIVE: To characterize the immunolocalization of clusterin in the repair cartilage of patients having undergone autologous chondrocyte implantation (ACI) and evaluate correlation to clinical outcome. DESIGN: Full-depth core biopsies of repair tissue were obtained from 38 patients who had undergone ACI at an average of 18 ± 13 months previously (range 8-67 months). The biopsies were snap frozen, cryosectioned, and clusterin production immunolocalized using a specific monoclonal clusterin antibody and compared with normal and osteoarthritic cartilage. Clinical outcome was assessed from patients preoperatively, at the time of biopsy, and annually postoperatively. RESULTS: Intensity of immunostaining for clusterin decreased with age in healthy cartilage tissue. Clusterin was detected to a variable degree in 37 of the 38 ACI cartilage biopsies, in single and clustered chondrocytes, in the pericellular capsule and the cartilage extracellular matrix, as well as the osteocytes and osteoid within the bone. Chondrocytes in hyaline repair tissue were significantly more immunopositive than those in fibrocartilage repair tissue. Clinical outcome improved significantly post-ACI, but did not correlate with the presence of clusterin in the repair tissue. CONCLUSIONS: These results demonstrate the presence of clusterin in actively repairing human cartilage and indicate a different distribution of clusterin in this tissue compared to normal cartilage. Variability in clusterin staining in the repair tissue could indicate different states of chondrogenic differentiation. The clinical significance of clusterin within repair tissue is difficult to assess, although the ideal functioning repair tissue morphology should resemble that of healthy adult cartilage.

Spectroscopic measurement of cartilage thickness in arthroscopy: ex vivo validation in human knee condyles.

PURPOSE: To evaluate the accuracy of articular cartilage thickness measurement when implementing a new technology based on spectroscopic measurement into an arthroscopic camera. METHODS: Cartilage thickness was studied by ex vivo arthroscopy at a number of sites (N = 113) in human knee joint osteoarthritic femoral condyles and tibial plateaus, removed from 7 patients undergoing total knee replacement. The arthroscopic image spectral data at each site were used to estimate cartilage thickness. Arthroscopically derived thickness values were compared with reference cartilage thickness as measured by 3 different methods: needle penetration, spiral computed tomography scanning, and geometric measurement after sample slicing. RESULTS: The lowest mean error (0.28 to 0.30 mm) in the regression between arthroscopic and reference cartilage thickness was seen for reference cartilage thickness less than 1.5 mm. Corresponding values for cartilage thickness less than 2.0 and 2.5 mm were 0.32 to 0.40 mm and 0.37 to 0.47 mm, respectively. Cartilage thickness images--created by pixel-by-pixel regression model calculations applied to the arthroscopic images--were derived to demonstrate the clinical use of a camera implementation. CONCLUSIONS: On the basis of this investigation on osteoarthritic material, when one is implementing the spectroscopic method for estimating cartilage thickness into an arthroscopic camera, errors in the range of 0.28 to 0.30 mm are expected. This implementation does not, however, influence the fact that the spectral method performs less well in the cartilage thickness region from 1.5 to 2.5 mm and cannot assess cartilage thicker than 2.5 mm. CLINICAL RELEVANCE: Imaging cartilage thickness directly in the arthroscopic camera video stream could serve as an interesting image tool for in vivo cartilage quality assessment, in connection with cartilage diagnosis, repair, and follow-up.

Function and survival after revision of hip resurfacing.

The purpose of this study was to compare functional outcome and survival of isolated acetabular, isolated femoral and both component revision after failure of primary Birmingham Hip Resurfacing. The Oswestry Outcome Centre prospectively collected data on 5000 hip resurfacing between 1997 and 2002. Of these, 182 hips were revised: 8% had revision of the acetabular component only, 42% had revision of the femoral component only to conventional stemmed prosthesis, and 50% had revision of both components to conventional total hip arthroplasty (THA). We used a postal questionnaire to assess function by Harris and Merle d'Aubigné and Postel hip scores and determined survival using re-revision as an endpoint. In patients with isolated acetabular revision, the median Harris hip score (HHS) was 74 at a mean of 4.5 years follow up. Isolated femoral revision had a median HHS of 82 at a mean of 3.8 years. When both components were revised, the median HHS was 85 at a mean of 4 years. We observed no difference in HHS between the groups. There was an average survival of 92% at 10 years. Survival was significantly lower for isolated acetabular revision (75%) than isolated femoral (93%) or both component revision (96%).