Treatment Of Focal Chondral Defects Research Articles

Comparative efficacy of synthetic peptide, platelet-rich plasma, and hyaluronic acid alone or in combination in microfracture treatment of focal chondral defects

Aims: Although previous limited studies have evaluated the efficacy of adjuvants used alone or in combination to augment microfracture (MF) treatment for focal chondral defects, there are no studies comparing the outcomes of the synthetic peptide (SP) with other adjuvants such as platelet-rich plasma (PRP), hyaluronic acid (HA), or their combinations. This study aimed to evaluate whether the efficacy of MF treatment in focal chondral defects is influenced by the use of adjuvants either alone or in combination. Methods: Thirty-six rats were included in the study. Group 1 received MF alone, Group 2 received PRP after MF, Group 3 received HA after MF, Group 4 received a SP after MF, Group 5 received a SP plus PRP therapy after MF, and Group 6 received a SP plus HA therapy. The knees of the rats were assessed according to the International Cartilage Repair Society (ICRS) Cartilage Repair Assessment 1 (ICRS-1) and 2 (ICRS-2). Results: The median ICRS-1 and ICRS-2 scores in Group 1 were lower compared to the other groups, while these scores in Group 2 and Group 4 were similar and higher than the other groups. Also, these scores in Group 5 and Group 6 were similar and lower compared to Group 3 (Group 1: 1 vs. Group 2: 12 vs. Group 3: 9 vs. Group 4: 11 vs. Group 5: 7 vs. Group 6: 7, p < 0.001 for ICRS-1 scores; Group 1: 0 vs. Group 2: 85 vs. Group 3: 70 vs. Group 4: 80 vs. Group 5: 45 vs. Group 6: 45, p < 0.001 for ICRS-2 scores). Conclusion: In the MF treatment of focal chondral defects, SP, PRP, and HA injections have a beneficial adjuvant effect based on macroscopic and histopathological findings. However, the combination of these adjuvants is less beneficial than their individual usage.

Bone Marrow-Derived Mesenchymal Stem Cell Implants for the Treatment of Focal Chondral Defects of the Knee in Animal Models: A Systematic Review and Meta-Analysis.

Osteoarthritis remains an unfortunate long-term consequence of focal cartilage defects of the knee. Associated with functional loss and pain, it has necessitated the exploration of new therapies to regenerate cartilage before significant deterioration and subsequent joint replacement take place. Recent studies have investigated a multitude of mesenchymal stem cell (MSC) sources and polymer scaffold compositions. It is uncertain how different combinations affect the extent of integration of native and implant cartilage and the quality of new cartilage formed. Implants seeded with bone marrow-derived MSCs (BMSCs) have demonstrated promising results in restoring these defects, largely through in vitro and animal studies. A PRISMA systematic review and meta-analysis was conducted using five databases (PubMed, MEDLINE, EMBASE, Web of Science, and CINAHL) to identify studies using BMSC-seeded implants in animal models of focal cartilage defects of the knee. Quantitative results from the histological assessment of integration quality were extracted. Repair cartilage morphology and staining characteristics were also recorded. Meta-analysis demonstrated that high-quality integration was achieved, exceeding that of cell-free comparators and control groups. This was associated with repair tissue morphology and staining properties which resembled those of native cartilage. Subgroup analysis showed better integration outcomes for studies using poly-glycolic acid-based scaffolds. In conclusion, BMSC-seeded implants represent promising strategies for the advancement of focal cartilage defect repair. While a greater number of studies treating human patients is necessary to realize the full clinical potential of BMSC therapy, high-quality integration scores suggest that these implants could generate repair cartilage of substantial longevity.

EE338 Cost-Effectiveness Analysis of Arthroscopic Injection of a Bioadhesive Hydrogel Implant in Conjunction with Microfracture for the Treatment of Focal Chondral Defects of the Knee: An Australian Perspective

JointRep is a bioadhesive hydrogel arthroscopically injected to facilitate cartilage regeneration. The cost-effectiveness of JointRep with microfracture surgery compared to microfracture alone was evaluated from the Australian healthcare system perspective, in patients with symptomatic focal osteochondral defects (Outerbridge Grade 3 or 4) of the knee who had failed conservative treatment and were indicated for surgery.

Cost-effectiveness analysis of arthroscopic injection of a bioadhesive hydrogel implant in conjunction with microfracture for the treatment of focal chondral defects of the knee – an Australian perspective

Aim JointRep is a bioadhesive hydrogel arthroscopically injected to facilitate cartilage regeneration. The cost-effectiveness of JointRep with microfracture surgery compared to microfracture alone was evaluated from the Australian healthcare system perspective, in patients with symptomatic focal chondral defects (Outerbridge Grade 3 or 4) of the knee who had failed conservative treatment and were indicated for surgery. Materials and methods A de novo Markov model comprising two health states- ‘Alive’ and ‘Dead’ was developed. Model transition probability was based on the general population mortality rates. Clinical outcomes were assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, a validated patient-reported tool measuring pain, stiffness, and physical function. The utility was derived by mapping WOMAC scores to EQ-5D scores using a published algorithm. Cost inputs were based on published Australian costs from AR-DRGs, Medicare Benefits Schedule, and Prostheses List. Model outcomes included costs, Quality-adjusted life years (QALYs), and incremental cost-effectiveness ratio (ICER). Base-case analysis was conducted for a time horizon of 3 years and a cycle length of 1 year. Cost and health outcomes were discounted at 5% per annum. Sensitivity and scenario analyses were also conducted. Results Total QALYs were estimated to be higher for JointRep with microfracture surgery (2.61) compared to microfracture surgery alone (1.66), an incremental gain of 0.95 QALY. JointRep with microfracture surgery was associated with an incremental cost of $6,022 compared to microfracture surgery alone, thus leading to an ICER of $6,328. Results were substantially robust to varying parameters in the sensitivity analyses conducted, alternative model settings and assumptions in scenario analyses. Limitations The clinical inputs used in the model were based on data from short duration, non-randomized, post-market clinical trial. Conclusions JointRep with microfracture surgery is a cost-effective treatment option compared to microfracture alone from the Australian health care system perspective.

The Use of Autologous Chondrocyte and Mesenchymal Stem Cell Implants for the Treatment of Focal Chondral Defects in Human Knee Joints-A Systematic Review and Meta-Analysis.

Focal chondral defects of the knee occur commonly in the young, active population due to trauma. Damage can insidiously spread and lead to osteoarthritis with significant functional and socioeconomic consequences. Implants consisting of autologous chondrocytes or mesenchymal stem cells (MSC) seeded onto scaffolds have been suggested as promising therapies to restore these defects. However, the degree of integration between the implant and native cartilage still requires optimization. A PRISMA systematic review and meta-analysis was conducted using five databases (PubMed, MEDLINE, EMBASE, Web of Science, CINAHL) to identify studies that used autologous chondrocyte implants (ACI) or MSC implant therapies to repair chondral defects of the tibiofemoral joint. Data on the integration of the implant-cartilage interface, as well as outcomes of clinical scoring systems, were extracted. Most eligible studies investigated the use of ACI only. Our meta-analysis showed that, across a total of 200 patients, 64% (95% CI (51%, 75%)) achieved complete integration with native cartilage. In addition, a pooled improvement in the mean MOCART integration score was observed during post-operative follow-up (standardized mean difference: 1.16; 95% CI (0.07, 2.24), p = 0.04). All studies showed an improvement in the clinical scores. The use of a collagen-based scaffold was associated with better integration and clinical outcomes. This review demonstrated that cell-seeded scaffolds can achieve good quality integration in most patients, which improves over time and is associated with clinical improvements. A greater number of studies comparing these techniques to traditional cartilage repair methods, with more inclusion of MSC-seeded scaffolds, should allow for a standardized approach to cartilage regeneration to develop.

Improved Outcomes with Arthroscopic Bone Marrow Aspirate Concentrate and Cartilage-Derived Matrix Implantation versus Chondroplasty for the Treatment of Focal Chondral Defects of the Knee Joint: A Retrospective Case Series

PurposeTo compare the outcomes of patients undergoing treatment of focal chondral defects (FCDs) of the knee joint with chondroplasty versus bone marrow aspirate concentrate (BMAC) and cartilage-derived matrix (CDM) implantation.MethodsA retrospective chart review was performed for patients diagnosed with Outerbridge grade 3-4 FCDs. Patients were included if they were treated arthroscopically with BMAC/CDM implantation or chondroplasty alone between March 2016 and May 2019 and had more than 1-year follow-up. Postoperative outcomes included the visual analog scale (VAS) for pain; University of California, Los Angeles (UCLA) activity scores; Knee Outcome Survey (KOS) Activities of Daily Living (ADL) and Sports subscores; postoperative corticosteroid or hyaluronic acid injections; subsequent surgeries; and conversion to total knee arthroplasty.ResultsA total of 98 patients were identified with a mean follow-up in BMAC/CDM of 24 months (range 13-41 months) and in chondroplasty of 44 months (range 34-55 months). A subanalysis was performed to control for significant differences in age, which yielded 39 patients, ages 40-60 years. Within the subanalysis group, mean VAS scores were significantly lower in the BMAC/CDM group (1.7 vs 4.4; P = .005) and mean UCLA scores were significantly greater (7.1 vs 5.0; P = .002). Mean improvement in VAS and UCLA scores were similar between the BMAC/CDM and chondroplasty groups (–3.7 vs –1.3; P = .71, 1.9 vs 0.1; P = .14, respectively). Mean KOS ADL and Sports subscores were significantly greater among patients in the BMAC/CDM group (87% vs 55%; P = .001, 71% vs 41%; P = .002, respectively). There were no differences in postoperative injections, subsequent surgeries, or conversion to total knee arthroplasty between the BMAC/CDM and chondroplasty groups.ConclusionsPatients with grade 3-4 FCDs of the knee had improved postoperative outcomes when treated with BMAC/CDM implantation versus chondroplasty alone, as evidenced by a significant improvement in VAS and UCLA scores and significantly greater postoperative KOS ADL, and KOS Sport subscores.Level of EvidenceIV, therapeutic case series.

Mid-term outcomes of arthroscopic osteochondral autograft transplantation for focal chondral defects of the knee

Objectives: Osteochondral autograft transplantation (OAT) for the management of cartilage defect involves direct transfer of hyaline cartilage to the defect site. The study aims to assess mid-term functional outcomes of arthroscopic treatment of focal chondral defects of the knee using the OAT technique. Materials and Methods: In this prospective follow-up study, patients who had previously undergone an OAT procedure for chondral defects of the knee at least 2 years prior were included. All the cartilage defects were treated arthroscopically with one or two plugs. Patients were followed up at 2 time points – in June 2016 and June, 2020. The International Knee Documentation Committee (IKDC) score and Tegner activity scale (TAS) were recorded preoperatively and at both follow-ups. Results: There were 20 patients with 21 focal cartilage defects, comprising 14 males and 6 females, with an average age of 30.9 ± 7 years and mean body mass index (BMI) of 27.2 ± 4 kg/m2. The first follow-up was after a mean 42.4 ± 12 months and the second after mean 90.4 ± 11.9 months post-surgery. The IKDC score improved significantly at both follow-ups compared to pre-operative scores (P < 0.001). At the first follow-up, the mean change in IKDC score was 25.3 ± 16.7 with 14 patients (70%) achieving minimal clinically important difference (MCID) but only 5 (25%) achieving substantial clinical benefit (SCB). At the second follow-up, 16 patients (80%) achieved MCID and 8 (40%) achieved SCB in IKDC score, with a mean change of 28.3 ± 12.6. The TAS showed statistically significant improvement at the first follow-up (P = 0.011), but not at the second follow-up (P = 0.052). Conclusion: OAT for focal cartilage defects of the knee is an excellent option as it provides clinically significant and incremental improvement in functional results in the mid-term. The results are not inferior even when a concomitant ligament or meniscus surgery is performed. Higher age or BMI does not have a negative impact on the outcomes.

Autologous Chondrocyte Transplantation in Femoroacetabular Impingement Syndrome: Growth and Redifferentiation Potential of Chondrocytes Harvested from the Femur in Cam-Type Deformities.

Cam-type femoroacetabular impingement (FAI) syndrome is one of the most frequent reasons for cartilage damage in the hip. Autologous chondrocyte transplantation has proven high success rates in the treatment of focal chondral defects; however, harvesting of chondrocytes in the hip has been reported but not specifically from the region of femoral cam lesions. Therefore, the goal of this study was to analyze the growth and redifferentiation potential of cartilage samples harvested from the cam deformities in patients with FAI. Cartilage samples were gained from 15 patients with cam-type FAI undergoing arthroscopic femoral cam resection. Healthy (hyaline cartilage of the hip and knee joint, n = 12) and arthritic control groups (degenerative changes in cartilage of the hip joint, n = 8) were also analyzed. Chondrocytes were initially cultured under monolayer, and subsequently under pellet conditions. A comparative representation of the groups was performed by Mankin score classification, immunohistochemistry (IHC) (Col1, Col2, aggrecan), and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) (Col1, Col2, Col10, Sox9, RunX2). Mankin score of FAI-samples (4.1±3.1, Range 0-10) showed a wide variation but was significant lower (P = 0.0244) when compared with the arthritic control (7.5 ± 2.7, range 4-12). IHC showed an increased deposition of Col2 (P = 0.0002) and aggrecan (P = 0.0261) after pellet culture compared with deposition after monolayer culture in all groups. In qRT-PCR, FAI samples showed after pellet culture increased Col2 (P = 0.0050) and Col10 expression (P = 0.0006) and also Mankin score correlated increasing gene-expression of Col10 (r = 0.8108, P = 0.0341) and RunX2 (r = 0.8829, P = 0.123). Cartilage samples of patients with cam-type FAI showed sufficient but heterogeneous composition relating to histological quality and chondrogenic potential. However, harvesting of chondrocytes from the cam lesion might be a valid option especially if a cartilage lesion is noted in a diagnostic arthroscopy and individual preexisting stage of cartilage degeneration and appropriate pellet-culturing conditions are considered.

Results at 10-14years after microfracture treatment of articular cartilage defects in the knee.

To evaluate the long-term clinical outcome after microfracture treatment of focal chondral defects of the knee and to investigate possible early determinants of the outcome. A prospective cohort of 110 patients, treated with microfracture, was evaluated at a median of 12years (range 10-14) by Lysholm score, VAS of knee function and VAS of knee pain. Pre- and perioperative information was collected, and additional surgery to the same knee during the follow-up period was recorded. Analysis of variance and paired t test were used for comparison of the long-term data to results from the baseline examination and a former 5-year (midterm) follow-up evaluation. Forty-three patientsneeded additional surgery to the knee including seven knee replacements. Fifty had a poor long-term outcome-defined as a knee replacement surgery or Lysholm score below 64. A poor result was more common in subgroups with mild degenerative changes in the cartilage surrounding the treated defect, concurrent partial meniscectomy, poor baseline Lysholm score or long-standing knee symptoms. The Lysholm score, function VAS and pain VAS all significantly improved from the baseline values to the mean scores of 65 (SD 24), 65 (SD 24) and 31 (SD 24), respectively, at the long-term evaluation. The long-term scores did not differ significantly from the midterm scores. The outcome scores improved significantly from baseline to the long-term evaluation and were not different from the midterm outcome. Still, a normal knee function was generally not achieved, and many patients had further surgery. The results call for more research and, at present, caution in recommending microfracture in articular cartilage defects, especially in subgroups with worse prognosis. Case series, Level IV.

Minced Cartilage Techniques

Minced articular cartilage techniques are viable one-stage, off-the-shelf cartilage repair procedures for treatment of focal chondral defects in the knee. In the United States, DeNovo natural tissue (NT) is the only particulated juvenile allograft one-stage articular cartilage technique currently available that does not violate the subchondral bone. DeNovo NT is composed of 1mm 3 fragments of juvenile (donor age is less than 13 years) articular cartilage, embedded within fibrin adhesive at the time of implantation. DeNovo NT is a chondroconductive, chondroinductive, and chondrogenic product. Given that it is minimally manipulated, it does not require US Food and Drug Administration premarket approval. DeNovo NT has been available in the United States since May 2007, and approximately 7500 cases have been performed to date. The basic science and clinical outcome literature supporting minced articular cartilage techniques in treatment of focal chondral defects of the knee is early and short term, but nonetheless promising. Juvenile cells are advantageous over adult cells in that they have a greater migration and proliferation capacity without immunogenicity. Clinical outcomes, at up to 2.5 years of follow-up, have demonstrated a significant improvement in validated cartilage outcome scores, reductions in pain, and improvements in function and activity in patients with both patellofemoral and tibiofemoral lesions treated with DeNovo NT.

Low elastic modulus contributes to the osteointegration of titanium alloy plug

Resurfacing of cartilage defect with mini titanium plug is considered a promising alternative for the treatment of focal chondral defects. Elastic modulus of the metal implant plays a significant role in force transmission which influences the stability of plug. This study assessed the effects of two kinds of titanium alloy plug with different elastic modulus, that is, titanium 2448 (Ti2448) plug and titanium-6 aluminum-4 vanadium (TAV) plug on osteointegration. The full-thickness chondral defects were created in bilateral knees of dogs and then TAV and Ti2448 plugs were implanted, respectively. After 12 weeks, radiographic evaluation did not reveal any signs of disassembly, subsidence, or periprosthetic radiolucency in both groups. Microcomputed tomography analysis revealed that bone histomorphometric parameters in Ti2448 group were all significantly better than those of TAV group. Furthermore, the value of pullout force in Ti2448 group was also significantly higher. Histology showed that the screw threads of Ti2448 plug were well integrated into the newly formed bone. In contrast, the trabecular bone was sparsely distributed around TAV plug. In conclusion, Ti2448 plug with low elastic modulus showed more favorable characteristics in osteointegration. Ti2448 may be a promising biomaterial for fabricating mini plug applied for cartilage resurfacing.

Paper 42: Autologous Osteochondral Grafts in the Treatment of Focal Chondral Defects of the Femoral Head: An Experimental Study in Rabbits

To investigate and compare macroscopically and histologically the reconstructed articular surface of a focal defect of the right femoral head treated with subchondral drilling or autologous osteochondral transplantation in rabbits A 2,5 mm diameter and 3 mm depth iatrogenic osteochondral defect in the anterolateral weight bearing area of the right femoral head was created in 12 rabbits. Autologous osteochondral transplantation was performed in a group of 6 rabbits. Donor site was the lateral condyle of the ipsilateral knee joint. The other group of 6 rabbits was treated with subchondral drilling. Both groups were sacrificed and evaluated histologically under the classification system of the ICRS after 6 weeks. For statistical analysis we used the Mann – Wittney test According to the ICRS, score statistical significance favoring the osteochondral transplantation was found in all variables between the 2 groups: articular surface (p=0,049), matrix (p=0,003), cell distribution (p< 0,0005), subchondral bone (p=0,010), cartilage mineralization (p=0,0) except cell population viability. In comparison to subchondral drilling, autologous osteochondral transplantation offered mature fully constructed tissue providing better results. Both methods provided viable cells. All grafts had successful incorporation of the osseous part. No necrosis of the femoral head was noticed. Reconstruction of the articular surface of the femoral head through autologous osteochondral graft transplantation after focal osteochondral defect in rabbits gives superior macroscopical and histological results in comparison to subchondral drilling

The Effect of Autologous Conditioned Plasma on the Treatment of Focal Chondral Defects of the Knee. An Experimental Study

The purpose of the present study was to evaluate the effect of local application of Autologous Conditioned Plasma (ACP) on the treatment of full-thickness cartilage injuries of the knee. The hypothesis of the study was that ACP can enhance healing response of injured cartilage. A full-thickness chondral lesion on the weight-bearing area of the medial femoral condyle was performed in 30 sheep. Animals were divided into 2 groups, according to postoperative treatment: in group 1, weekly injections of ACP for five times were performed; in group 2, lesions were left untreated. Animals were sacrificed at 3, 6 and 12 months after treatment. A histological evaluation was performed according to a modified O'Driscoll histological score. Comparison between groups for each time interval was performed with the Student's t-test. Significance was set at P<0.05. A post-hoc power analysis was performed according to the hypothesis of the study. Histological evaluation at 3 and 6 months showed that group 1 had significantly greater total score than group 2. At 12 months, no significant difference was observed between groups. In conclusion, local injections of ACP for treatment of full-thickness cartilage injuries did not produce hyaline cartilage. However, it promoted reparative response of the cartilage defect until 6 months after treatment.

P139 Autologous osteochondral grafts in the treatment of focal chondral defects of the femoral head. An experimental study in rabbits.

P139 Autologous osteochondral grafts in the treatment of focal chondral defects of the femoral head. An experimental study in rabbits.

What&amp;#146;s New in the Treatment of Focal Chondral Defects of the Knee?

What&amp;#146;s New in the Treatment of Focal Chondral Defects of the Knee?

Autologous Chondrocyte Implantation

ABSTRACT Autologous chondrocyte implantation (ACI) uses cultured chondrocytes implanted beneath a periosteal patch for the treatment of focal chondral defects of the knee. ACI can be used for defects measuring 2 to 10 cm2. The surgery is performed in 2 stages. In the first stage, a biopsy of normal cartilage is taken from a non-weight-bearing portion of the knee. The biopsy sample is processed and the isolated cells are expanded through cell culture to approximately 12 million chondrocytes. In the second stage of the procedure, the cells are implanted into the chondral defect, beneath a periosteal patch. Rehabilitation consists of early range of motion with restricted weight bearing. Most patients return to daily activities within 4 months, with return to sport at 12 to 16 months.

Experimental autologous osteochondral plug transfer in the treatment of focal chondral defects: magnetic resonance imaging signs of technical success in sheep

To describe the magnetic resonance imaging (MRI) signs of technically successful osteochondral plug transfer and to correlate the findings with histology using the Mankin score. The study was done in a prospective animal experiment: 11 adult black-head sheep underwent surgical treatment with osteochondral plug transfer of a knee joint. The animals were killed 6 months later and MRI of the joints was done immediately. MRI was applied with a 1.5T MR scanner using a spin-echo (SE) T1-weighted, turbo spin-echo (TSE) T2-weighted with spectral fat suppression and a fat-suppressed 3D-spoiled gradient echo (GRE) sequence (manufacturer's acronym: FLASH) (TR 50.0 ms, TE 11.0 ms, flip 35 degrees). After MRI, all knee joints were dissected and a biopsy of the plug and the adjacent cartilage was taken. Classification of the cartilage biopsies was carried out in accordance with a modified Mankin score. Cartilage repairs with a hypointense cartilage signal in the FLASH 3D sequence were correlated with poor histological results (lower Mankin score). Histologically, the regions of cartilage with a hypointense signal showed a fibrocartilage-like repair tissue. Hyaline cartilage with well-defined layers had the same signal intensity in the FLASH sequence relative to adjacent hyaline cartilage. There were two plugs with a surface defect, graded as Outerbridge grade 1 in MRI and histology. Both had a poor outcome in the histologic Mankin score. Grade 2-4 lesions were not observed in the MRI study nor in the histologic study. MRI is a useful non-invasive tool for evaluating the morphologic status of osteochondral plug transfers. A good postoperative result of the cartilage repair was found histologically if an isointense cartilage signal of the graft was documented in the FLASH 3D sequence, and the graft had good congruity with the articular surface without defects.

Autologous chondrocyte implantation for treatment of focal chondral defects of the knee—a clinical, arthroscopic, MRI and histologic evaluation at 2 years

To determine the efficacy of autologous chondrocyte implantation (ACI) in treating focal chondral defects of the knee, we reviewed the 2-year treatment outcome of ACI in 53 patients (72 lesions) through clinical evaluation, MRI, second-look arthroscopy and biopsies obtained. Improvement in mean subjective score from preoperative (37.6) to 12 months (56.4) and 24 (60.1) months post-ACI were observed. Knee function levels also improved [86% International Cartilage Repair Society (ICRS) III/IV to 66.6% I/II] from preoperative period to 24 months postimplantation. Objective IKDC score of A or B were observed in 88% preoperatively. This decreased to 67.9% at 3 months before improving to 92.5% at 12 months and 94.4% at 24 months post implantation. Transient deterioration in all these clinical scores was observed at 3 months before progressive improvement became evident. MRI studies demonstrated 75.3% with at least 50% defect fill, 46.3% with near normal signal, 68.1% with mild/no effusion and also 66.7% with mild/no underlying bone marrow oedema at 3 months. These values improved to 94.2%, 86.9%, 91.3% and 88.4%, respectively, at 12 months. At 24 months, further improvements to 97%, 97%, 95.6% and 92.6%, respectively, were observed. Second-look arthroscopy carried out in 22 knees (32 lesions) demonstrated all grafts to be normal/nearly normal based on the International Cartilage Repair Society (ICRS) visual repair assessment while core biopsies from 20 lesions demonstrated 13 grafts to have hyaline/hyaline-like tissue. Improvement in clinical and MRI findings obtained from second-look arthroscopy and core biopsies evaluated indicate that, at 24 months post-ACI, the resurfaced focal chondral defects of the knee remained intact and continued to function well.