Definition of pertinent parameters for the evaluation of articular cartilage repair tissue with high-resolution magnetic resonance imaging

Cartilage T2 assessment at 3-T MR imaging: in vivo differentiation of normal hyaline cartilage from reparative tissue after two cartilage repair procedures--initial experience

PURPOSE

To prospectively compare cartilage T2 values after microfracture therapy (MFX) and matrix-associated autologous chondrocyte transplantation (MACT) repair procedures.

MATERIALS AND METHODS

The study had institutional review board approval by the ethics committee of the Medical University of Vienna; informed consent was obtained. Twenty patients who underwent MFX or MACT (10 in each group) were enrolled. For comparability, patients of each group were matched by mean age (MFX, 40.0 years +/- 15.4 [standard deviation]; MACT, 41.0 years +/- 8.9) and postoperative interval (MFX, 28.6 months +/- 5.2; MACT, 27.4 months +/- 13.1). Magnetic resonance (MR) imaging was performed with a 3-T MR imager, and T2 maps were calculated from a multiecho spin-echo measurement. Global, as well as zonal, quantitative T2 values were calculated within the cartilage repair area and within cartilage sites determined to be morphologically normal articular cartilage. Additionally, with consideration of the zonal organization, global regions of interest were subdivided into deep and superficial areas. Differences between cartilage sites and groups were calculated by using a three-way analysis of variance.

RESULTS

Quantitative T2 assessment of normal native hyaline cartilage showed similar results for all patients and a significant trend of increasing T2 values from deep to superficial zones (P < .05). In cartilage repair areas after MFX, global mean T2 was significantly reduced (P < .05), whereas after MACT, mean T2 was not reduced (P > or = .05). For zonal variation, repair tissue after MFX showed no significant trend between different depths (P > or = .05), in contrast to repair tissue after MACT, in which a significant increase from deep to superficial zones (P < .05) could be observed.

CONCLUSION

Quantitative T2 mapping seems to reflect differences in repair tissues formed after two surgical cartilage repair procedures. (c) RSNA, 2008.

Magnetic resonance imaging for diagnosis and assessment of cartilage defect repairs

Clinical magnetic resonance imaging (MRI) is the method of choice for the non-invasive evaluation of articular cartilage defects and the follow-up of cartilage repair procedures. The use of cartilage-sensitive sequences and a high spatial-resolution technique enables the evaluation of cartilage morphology even in the early stages of disease, as well as assessment of cartilage repair. Sequences that offer high contrast between articular cartilage and adjacent structures, such as the fat-suppressed, 3-dimensional, spoiled gradient-echo sequence and the fast spin-echo sequence, are accurate and reliable for evaluating intrachondral lesions and surface defects of articular cartilage. These sequences can also be performed together in reasonable examination times. In addition to morphology, new MRI techniques provide insight into the biochemical composition of articular cartilage and cartilage repair tissue. These techniques enable the diagnosis of early cartilage degeneration and help to monitor the effect and outcome of various surgical and non-surgical cartilage repair therapies.

International Cartilage Repair Society (ICRS) and Oswestry macroscopic cartilage evaluation scores validated for use in Autologous Chondrocyte Implantation (ACI) and microfracture

OBJECTIVE

For young patients with cartilage defects, the emergence of clinically applicable cell therapy for biological joint reconstruction is an appealing prospect. Acceptation of this method as a means of standard care requires proof of being reproducible, having long-lasting mechanical integrity, and having a good clinical outcome. This study evaluates the reliability of the International Cartilage Repair Society (ICRS) score and the Oswestry Arthroscopy Score (OAS) in the assessment of regenerative cartilage repair.

METHOD

A total of 101 macroscopic images of cartilage repair were made during arthroscopy 12 months post-treatment of either Autologous Chondrocyte Implantation (ACI) or microfracture. These images were examined by seven independent observers with differing levels of experience. The ICRS and OAS scores were randomly presented twice at a 4-week interval. All observers stated their predicted outcome according to actual treatment and defect size.

RESULTS

ICRS and OAS scores showed both good inter- and intra observer reliability (0.62 and 0.56 for ICRS; 0.73 and 0.65 for OAS, respectively). Internal consistency (Cronbach's alpha) was satisfactory for research purposes (0.79 and 0.74, respectively). Correlation (equivalence concordance) between both scoring systems was excellent (r=0.94). All observers were inconsistent in predicting actual treatment. Test-re test reliability of estimated defect size and its correlation to true defect size were poor. These results were also applicable to the sub-analyses of the experience of the observer and the quality of imaging.

CONCLUSION

The ICRS and OAS are reliable and relevant scores that are now both validated for macroscopic evaluation of cartilage repair as a research tool.

Arthroscopic autologous osteochondral grafting for cartilage defects of the knee: prospective study results at a minimum 7-year follow-up

BACKGROUND

Articular cartilage lesions, with their inherent limited healing potential, remain a challenging problem for orthopaedic surgeons. Various approaches have been proposed to treat these lesions; nevertheless, opinions on indications and clinical efficacy of these techniques are still controversial.

PURPOSE

To evaluate the outcome of osteochondral autografts for treatment of femoral condyle cartilage lesions at a medium-to long-term follow-up.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

We prospectively evaluated 30 patients (mean age, 29.3 years) with full-thickness knee chondral lesions (<2.5 cm(2)) treated with arthroscopic autologous osteochondral transplantation. Thirteen patients underwent previous surgery, while 17 patients were operated on for the first time. In 19 patients, associated procedures were performed. All patients were evaluated at 2- and 7-year follow-up. The International Cartilage Repair Society form, Tegner score, and magnetic resonance imaging were used for clinical evaluation.

RESULTS

The International Cartilage Repair Society objective evaluation showed 76.7% of patients had good or excellent results at 7-year follow-up, and International Knee Documentation Committee subjective score significantly improved from preoperative (34.8) to 7-year follow-up (71.8). The Tegner evaluation showed a significant improvement after the surgery at 2- and 7-year follow-up (from 2.9 to 6.2 and 5.6, respectively); however, we noticed reduced sports activity from 2- to 7-year follow-up. Magnetic resonance imaging evaluation showed good integration of the graft in the host bone and complete maintenance of the grafted cartilage in more than 60% of cases.

CONCLUSION

The results of this technique at medium- to long-term follow-up are encouraging. This arthroscopic 1-step surgery appears to be a valid solution for treatment of small, grade III to IV cartilage defects.

Steady-state diffusion imaging for MR in-vivo evaluation of reparative cartilage after matrix-associated autologous chondrocyte transplantation at 3 tesla--preliminary results

OBJECTIVES

To demonstrate the feasibility of time-reversed fast imaging with steady-state precession (FISP) called PSIF for diffusion-weighted imaging of cartilage and cartilage transplants in a clinical study.

MATERIAL AND METHODS

In a cross-sectional study 15 patients underwent MRI using a 3D partially balanced steady-state gradient echo pulse sequence with and without diffusion weighting at two different time points after matrix-associated autologous cartilage transplantation (MACT). Mean diffusion quotients (signal intensity without diffusion-weighting divided by signal intensity with diffusion weighting) within the cartilage transplants were compared to diffusion quotients found in normal cartilage.

RESULTS

The global diffusion quotient found in repair cartilage was significantly higher than diffusion values in normal cartilage (p<0.05). There was a decrease between the earlier and the later time point after surgery.

CONCLUSIONS

In-vivo diffusion-weighted imaging based on the PSIF technique is possible. Our preliminary results show follow-up of cartilage transplant maturation in patients may provide additional information to morphological assessment.

Autologous chondrocyte implantation: Prospective MRI evaluation with clinical correlation

PURPOSE

This study was done to assess the progression of cartilage repair after autologous chondrocyte implantation (ACI) with magnetic resonance imaging (MRI) and to correlate the findings with the clinical outcome.

MATERIALS AND METHODS

Forty-one patients (mean age 30 years) affected by chondral defects of the knee (27 patients) and ankle joint (14 patients) who underwent arthroscopic autologous osteochondral grafting were studied 6 months and 1 year postoperatively with MRI. Cartilage repair after chondrocyte implantation was studied by assessing the degree of defect filling, graft integration, graft signal intensity, integrity of the subchondral lamina and trabecular oedema underneath the graft. MR findings were correlated with clinical data.

RESULTS

Postoperative MRI evaluation at 6 months demonstrated complete filling of the osteochondral defect in 12/41 cases, complete integration in 18/41, mild hyperintensity in 28/41, intact subchondral lamina in 38/41 and trabecular oedema in 11/41. Postoperative MRI evaluation at 1 year demonstrated complete filling of the osteochondral defect in 9/41 patients, complete integration in 22/41, mild hyperintensity in 23/41, intact subchondral lamina in 36/41 and trabecular oedema in 8/41. Filling of the osteochondral defect and incomplete integration, nonintact subchondral lamina, high signal intensity and absence of oedema were found to correlate with worse clinical-functional outcomes.

CONCLUSIONS

MRI shows direct prognostic signs of the clinical outcome of ACI.

MRI and clinical evaluation of collagen-covered autologous chondrocyte implantation (CACI) at two years

We present our experience with the collagen-covered autologous chondrocyte implantation (CACI) technique. Thirty two implantations were performed in 31 patients. Clinical outcome was measured using the KOOS score and the 6-minute walk test, as well as an MRI scoring protocol (75% of patients had a complete data set for MRI follow-up) to describe the repair tissue generated by CACI. We have also correlated our MRI results with our clinical outcome. To the authors knowledge there are no comparative studies of MRI and clinical outcome following CACI in the current literature. Patients demonstrated an increased walk distance that improved significantly from 3 months to 24 months postoperatively (p<0.05). Analysis of the KOOS results demonstrated a significant (p<0.05) improvement in four of the five subscales from 3 months to 24 months after CACI, with the most substantial gains made in the first 12 months. Patients demonstrated an increased MRI outcome score over time that improved significantly from 3 months to 24 months postoperatively (p<0.05). We observed an 8% incidence of hypertrophic growth following CACI. We report one partial graft failure, defined by clinical, MRI and histological evaluation, at the one year time point. In contrast to the current literature we report no incidence of manipulation under anesthesia (MUA) following CACI. This research demonstrates that autologous chondrocytes implanted under a type I/III collagen patch regenerates a functional infill material, and as a result of this procedure, patients experienced improved knee function and MRI scores. Whilst our results indicated a statistically significant relationship between the MRI and functional outcome following CACI, MRI cannot be used as surrogate measure of functional outcome following CACI, since the degree of association was only low to moderate. That is, functional outcome following CACI cannot be predicted by the morphological MRI assessment of the repair tissue at the post-surgery time points to 24 months.

Postoperative Evaluation of the Knee after Autologous Chondrocyte Implantation: What Radiologists Need to Know

Articular cartilage lesions occur commonly. Cartilage is relatively avascular and is unable to self-repair. A chondral lesion may become symptomatic. It may lead to osteoarthritis and increased morbidity. The aim of cartilage repair is to restore hyaline cartilage. There are many types of cartilage repair surgery, most of which result in fibrocartilage repair tissue that is suboptimal. Autologous chondrocyte implantation has been shown to produce hyaline-type repair tissue. Magnetic resonance (MR) imaging is performed preoperatively to define the ulcer and postoperatively to evaluate the technical success of implantation and the state of cartilage healing and to identify potential complications. Features of the autologous chondrocyte implantation graft that are assessed include the degree of filling by repair tissue, its integration with native cartilage and subchondral bone, the character of the graft substance and surface, and the underlying bone. MR arthrography is superior to unenhanced MR imaging because intraarticular contrast material allows the recipient site to be physically separated from adjacent structures so that it can be characterized more accurately. MR imaging and arthroscopy are complementary investigations in the follow-up of an autologous chondrocyte implantation in the knee. The appearance of the knee after autologous chondrocyte implantation varies among individuals and according to the time-course of healing. Familiarity with the surgical procedure and imaging appearance is essential for an accurate postsurgical assessment.

Patellofemoral full-thickness chondral defects treated with Hyalograft-C: a clinical, arthroscopic, and histologic review

BACKGROUND

Tissue engineering has emerged as a potential therapeutic option for cartilage regeneration.

HYPOTHESIS

Hyaluronan-based scaffolds seeded with autologous chondrocytes are a viable treatment for damaged articular surface of the patellofemoral joint.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Thirty-two chondral lesions with a mean size of 4.7 cm(2) were treated with Hyalograft-C. Twenty-two lesions were located in the patella and 10 in the trochlea. Sixteen patients had previous trauma, 3 had osteochondritis dissecans, and 13 had degenerative changes. Transplantations were carried out arthroscopically or through a miniarthrotomy incision. Eight patients had concomitant procedures, including patellar realignment (2), lateral release (3), and meniscectomy (3). Results were evaluated using the International Cartilage Repair Society-International Knee Documentation Committee scale, EuroQol EQ-5D form, and magnetic resonance imaging scans at 12 and 24 months. Six patients had second-look arthroscopy and biopsies. Statistical analysis was performed using the paired t test and Wilcoxon signed rank test.

RESULTS

The International Cartilage Repair Society-International Knee Documentation Committee and EuroQol EQ-5D scores demonstrated a statistically significant improvement (P < .0001). Objective preoperative data improved from 6/32 (18.8%) with International Knee Documentation Committee A or B to 29/32 (90.7%) at 24 months after transplantation. Mean subjective scores improved from 43.2 points preoperatively to 73.6 points 24 months after implantation. Magnetic resonance imaging studies at 24 months revealed 71% to have an almost normal cartilage with positive correlation to clinical outcomes. Second-look arthroscopies in 6 cases revealed the repaired surface to be nearly normal with biopsy samples characterized as hyaline-like in appearance.

CONCLUSION

Biodegradable scaffolds seeded with autologous chondrocytes can be a viable treatment for chondral lesions. The type of tissue repair achieved demonstrated histologic characteristics similar to normal articular cartilage. Long-term investigations are needed to determine the durability of the repair produced with this technique.

MR imaging of osteochondral grafts and autologous chondrocyte implantation

Surgical articular cartilage repair therapies for cartilage defects such as osteochondral autograft transfer, autologous chondrocyte implantation (ACI) or matrix associated autologous chondrocyte transplantation (MACT) are becoming more common. MRI has become the method of choice for non-invasive follow-up of patients after cartilage repair surgery. It should be performed with cartilage sensitive sequences, including fat-suppressed proton density-weighted T2 fast spin-echo (PD/T2-FSE) and three-dimensional gradient-echo (3D GRE) sequences, which provide good signal-to-noise and contrast-to-noise ratios. A thorough magnetic resonance (MR)-based assessment of cartilage repair tissue includes evaluations of defect filling, the surface and structure of repair tissue, the signal intensity of repair tissue and the subchondral bone status. Furthermore, in osteochondral autografts surface congruity, osseous incorporation and the donor site should be assessed. High spatial resolution is mandatory and can be achieved either by using a surface coil with a 1.5-T scanner or with a knee coil at 3 T; it is particularly important for assessing graft morphology and integration. Moreover, MR imaging facilitates assessment of complications including periosteal hypertrophy, delamination, adhesions, surface incongruence and reactive changes such as effusions and synovitis. Ongoing developments include isotropic 3D sequences, for improved morphological analysis, and in vivo biochemical imaging such as dGEMRIC, T2 mapping and diffusion-weighted imaging, which make functional analysis of cartilage possible.

MR imaging of autologous chondrocyte implantation of the knee

Autologous chondrocyte implantation (ACI) is a surgical technique that is increasingly being used in the treatment of full-thickness defects of articular cartilage in the knee. It involves the arthroscopic harvesting and in vitro culture of chondrocytes that are subsequently implanted into a previously identified chondral defect. The aim is to produce a repair tissue that closely resembles hyaline articular cartilage that gradually becomes incorporated, restoring joint congruity. Over the long term, it is hoped that this will prevent the progression of full-thickness articular cartilage defects to osteoarthritis. This article reviews the indications and operative procedure performed in ACI. Magnetic resonance imaging (MRI) sequences that provide optimal visualization of articular cartilage in the post-operative period are discussed. Normal appearances of ACI on MRI are presented along with common complications that are encountered with this technique.

Matrix-based autologous chondrocyte implantation for cartilage repair with Hyalograft®C: Two-year follow-up by magnetic resonance imaging

OBJECTIVE

Monitoring of articular cartilage repair after matrix-associated autologous chondrocyte implantation with HyalograftC by a new grading system based on non-invasive high-resolution magnetic resonance imaging.

PATIENTS AND METHODS

In 23 patients, postoperative magnetic resonance imaging (MRI) was performed between 76 and 120 weeks. In nine of these patients, five MRI examinations were performed at 4, 12, 24, 52 and 104 weeks after HyalograftC implant. The repair tissue was described with separate variables: degree of defect repair in width and length, signal intensity of the repair tissue and status of the subchondral bone. For these variables a grading system with point scale evaluation was applied.

RESULTS

CONCLUSION

High-resolution MRI provides a non-invasive tool for monitoring the development of cartilage repair tissue following HyalograftC technology, shows a good correlation with clinical outcome and may help to differentiate abnormal repair tissue from a normal maturation process.

Magnetic resonance observation of cartilage repair tissue (MOCART) for the evaluation of autologous chondrocyte transplantation: determination of interobserver variability and correlation to clinical outcome after 2 years

In an observational study, the validity and reliability of magnetic resonance imaging (MRI) for the assessment of autologous chondrocyte transplantation (ACT) in the knee joint was determined. Two years after implantation, high-resolution MRI was used to analyze the repair tissue with nine pertinent variables. A complete filling of the defect was found in 61.5%, and a complete integration of the border zone to the adjacent cartilage in 76.9%. An intact subchondral lamina was present in 84.6% and an intact subchondral bone was present in 61.5%. Isointense signal intensities of the repair tissue compared to the adjacent native cartilage were seen in 92.3%. To evaluate interobserver variability, a reliability analysis with the determination of the intraclass correlation coefficient (ICC) was calculated. An "almost perfect" agreement, with an ICC value >0.81, was calculated in 8 of 9 variables. The clinical outcome after 2 years showed the visual analog score (VAS) at 2.62 (S.D. +/-0.65). The values for the knee injury and osteoarthritis outcome score (KOOS) subgroups were 68.29 (+/-23.90) for pain, 62.09 (+/-14.62) for symptoms, 75.45 (+/-21.91) for ADL function, 52.69 (+/-28.77) for sport and 70.19 (+/-22.41) for knee-related quality of life. The clinical scores were correlated with the MRI variables. A statistically significant correlation was found for the variables "filling of the defect," "structure of the repair tissue," "changes in the subchondral bone," and "signal intensities of the repair issue". High resolution MRI and well-defined MRI variables are a reliable, reproducible and accurate tool for assessing cartilage repair tissue.

Cartilage repair: generations of autologous chondrocyte transplantation

Articular cartilage in adults has a limited capacity for self-repair after a substantial injury. Surgical therapeutic efforts to treat cartilage defects have focused on delivering new cells capable of chondrogenesis into the lesions. Autologous chondrocyte transplantation (ACT) is an advanced cell-based orthobiologic technology used for the treatment of chondral defects of the knee that has been in clinical use since 1987 and has been performed on 12,000 patients internationally. With ACT, good to excellent clinical results are seen in isolated post-traumatic lesions of the knee joint in the younger patient, with the formation of hyaline or hyaline-like repair tissue. In the classic ACT technique, chondrocytes are isolated from small slices of cartilage harvested arthroscopically from a minor weight-bearing area of the injured knee. The extracellular matrix is removed by enzymatic digestion, and the cells are then expanded in monolayer culture. Once a sufficient number of cells has been obtained, the chondrocytes are implanted into the cartilage defect, using a periosteal patch over the defect as a method of cell containment. The major complications are periosteal hypertrophy, delamination of the transplant, arthrofibrosis and transplant failure. Further improvements in tissue engineering have contributed to the next generation of ACT techniques, where cells are combined with resorbable biomaterials, as in matrix-associated autologous chondrocyte transplantation (MACT). These biomaterials secure the cells in the defect area and enhance their proliferation and differentiation.

Matrix-based autologous chondrocyte implantation for cartilage repair: noninvasive monitoring by high-resolution magnetic resonance imaging

OBJECTIVE

Monitoring of articular cartilage repair after matrix-associated autologous chondrocyte implantation (MACI) by a new grading and point-scale system based on noninvasive cartilage-specific magnetic resonance imaging (MRI) protocol.

PATIENTS AND METHODS

In 20 patients, postoperative high-resolution MRI follow-up examinations at 4, 12, 24 and 52 weeks after matrix-based ACI for cartilage repair were initiated. The repair tissue was described with separate variables: degree of defect repair in width and length, surface, structure and signal intensity of the repair tissue, and status of the subchondral lamina and bone. For these variables, a grading system with point-scale evaluation was applied, and the mean average values were calculated for every follow-up MR exam of each patient.

RESULTS

In 10 patients, an incomplete filling of the defect improved to complete filling (6 patients) or less incomplete (4 patients) filling of the defect. Three cases of implant hypertrophy returned to normal within 1 year. Complete filling of the defect by repair tissue was found in 2 patients from the beginning. Integration was complete in 10 cases. Improvement of incomplete to complete integration was found in 3 patients. The signal intensity of the implant developed to native cartilage signal in 13 patients. The mean average values increased from the 4th to the 52 nd week in 17 of 20 patients and decreased in 3 of 20 patients.

CONCLUSION

High-resolution MRI provides a noninvasive tool for monitoring the development of cartilage repair tissue in MACI over time and helps to differentiate abnormal repair tissue from a normal maturation process.