Magnetic resonance imaging of knee hyaline cartilage and intraarticular pathology

Tissue Engineering and Cell Therapy for Cartilage Repair: Preclinical Evaluation Methods

A chondral injury is a limiting disease that can affect the quality of life and be an economic burden due to the cost of immediate treatment and loss in work productivity. If left untreated, such an injury may progress to osteoarthritis, a degenerative and debilitating joint disease characterized by pain and functional impairment. Mesenchymal stromal cells (MSCs), which have immune-modulatory properties and the ability to differentiate into chondroblasts and osteoblasts, are a predictable source for the treatment of cartilage injuries. This article presents tools to evaluate cartilage restoration by tissue engineering and cell therapy treatment in a translational and preclinical large animal model. In this controlled experimental study with 14 miniature pigs, a scaffold-free tissue engineering construct (TEC) derived from dental pulp and synovial MSCs for cartilage therapy was tested. Total thickness cartilage defects were performed in both posterior knees. The defect was left empty in one of the knees, and the other received the TEC. The tissue repair was morphologically assessed by magnetic resonance imaging (MRI) using the three-dimensional double echo steady-state (3D-DESS) sequence, and compositional assessment was carried out based on the T2 mapping technique. The osteochondral specimens were fixed for histopathology, decalcified, subjected to standard histological processing, sectioned, and stained with hematoxylin and eosin. The sections stained for immunohistochemical detection of collagen types were digested with pepsin and chondroitinase and incubated with antibodies against them. The mechanical evaluation involved analysis of Young's modulus of the cartilage samples based on the indentation and maximum compression test. In addition, a finite element model was used to simulate and characterize properties of the osteochondral block. At 6 months after surgery, there were no complications with the animals and the MRI, histological, immunohistochemical, and biomechanical evaluations proved to be effective and qualified to differentiate good quality chondral repair from inadequate repair tissue. The proposed methods were feasible and capable to properly evaluate the defect filled with TEC containing stromal cells after 6 months of follow-up in a large animal model for articular cartilage restoration. Impact Statement Articular chondral injuries are prevalent and represent an economic burden due to the cost of treatment. The engineering of cartilage tissue can promote the repair of chondral injuries and is dependent on selecting appropriate cells and biocompatible frameworks. In this article, methods for evaluation of a scaffold-free cell delivery system made from mesenchymal stromal cells were present in a translational study that allows further clinical safety and efficacy trials.

Cell-laden hydrogels for osteochondral and cartilage tissue engineering

Despite tremendous advances in the field of regenerative medicine, it still remains challenging to repair the osteochondral interface and full-thickness articular cartilage defects. This inefficiency largely originates from the lack of appropriate tissue-engineered artificial matrices that can replace the damaged regions and promote tissue regeneration. Hydrogels are emerging as a promising class of biomaterials for both soft and hard tissue regeneration. Many critical properties of hydrogels, such as mechanical stiffness, elasticity, water content, bioactivity, and degradation, can be rationally designed and conveniently tuned by proper selection of the material and chemistry. Particularly, advances in the development of cell-laden hydrogels have opened up new possibilities for cell therapy. In this article, we describe the problems encountered in this field and review recent progress in designing cell-hydrogel hybrid constructs for promoting the reestablishment of osteochondral/cartilage tissues. Our focus centers on the effects of hydrogel type, cell type, and growth factor delivery on achieving efficient chondrogenesis and osteogenesis. We give our perspective on developing next-generation matrices with improved physical and biological properties for osteochondral/cartilage tissue engineering. We also highlight recent advances in biomanufacturing technologies (e.g. molding, bioprinting, and assembly) for fabrication of hydrogel-based osteochondral and cartilage constructs with complex compositions and microarchitectures to mimic their native counterparts.

STATEMENT OF SIGNIFICANCE

Despite tremendous advances in the field of regenerative medicine, it still remains challenging to repair the osteochondral interface and full-thickness articular cartilage defects. This inefficiency largely originates from the lack of appropriate tissue-engineered biomaterials that replace the damaged regions and promote tissue regeneration. Cell-laden hydrogel systems have emerged as a promising tissue-engineering platform to address this issue. In this article, we describe the fundamental problems encountered in this field and review recent progress in designing cell-hydrogel constructs for promoting the reestablishment of osteochondral/cartilage tissues. Our focus centers on the effects of hydrogel composition, cell type, and growth factor delivery on achieving efficient chondrogenesis and osteogenesis. We give our perspective on developing next-generation hydrogel/inorganic particle/stem cell hybrid composites with improved physical and biological properties for osteochondral/cartilage tissue engineering. We also highlight recent advances in biomanufacturing and bioengineering technologies (e.g. 3D bioprinting) for fabrication of hydrogel-based osteochondral and cartilage constructs.

MR Imaging of Patellar Cartilage Degeneration at 0.02 T

MR imaging with a 0.02 T resistive magnet was used to establish the correlation between the histologic grading of patellar cartilage degeneration and fat water separation images or T1- and T2-relaxation times. We examined 23 cadaveric patellae. There was a positive correlation between histologically graded cartilage degeneration and T1-relaxation time. Patellar cartilage was well differentiated from surrounding structures on chemical shift water proton images, and an evaluation of cartilage degeneration was possible. No correlation was found between cartilage damage and T2-relaxation time. Chemical shift imaging at 0.02 T is easy to perform and gives further information of cartilage disorders.

Correlation between magnetic resonance imaging and arthroscopic findings in the knee joint

BACKGROUND

The knee joint is the largest and the most complex joint of the human body. It is not covered by any thick muscular covering anteriorly.

OBJECTIVES

The purpose of this study was to explore the diagnostic capabilities of clinical examination, magnetic resonance imaging (MRI), and arthroscopy in traumatic disorders of the knee joint, to seek correlation between clinical findings, MRI findings and arthroscopic.

PATIENTS AND METHODS

A total of 26 patients with a presentation suggestive of traumatic knee pathology were studied prospectively. A detailed history was taken and relevant clinical examination was done, which was followed by MRI of the knee. The patients were scheduled for arthroscopy under general/spinal anesthesia, whenever indicated.

RESULTS

Keeping arthroscopic examination as standard, the correlation between clinical and arthroscopy showed a sensitivity of 80%, specificity of 86%, accuracy of 63.16%, negative predictive value of 93.48%; whereas MRI vs. arthroscopy showed a sensitivity of 74.42%, specificity of 93.10%, accuracy of 84.21%, and negative predictive value of 88.04%.

CONCLUSIONS

The clinical examination is an important and accurate diagnostic modality for evaluation of traumatic derangement of the knee joint. It is noninvasive, easy, available, and valuable diagnostic modality. The MRI is an accurate diagnostic modality. It can be used whenever there is an uncertain indication for arthroscopy. However, costs have to be kept in mind, especially in patients with low socio-economic status.

Improved identification of the palmar fibrocartilage of the navicular bone with saline magnetic resonance bursography

Fibrocartilage degeneration is the earliest pathologic finding in navicular disease but remains difficult to detect, even with magnetic resonance (MR) imaging. We hypothesized that injection of the navicular bursa with saline would improve accuracy of MR imaging evaluation of palmar fibrocartilage. Thoracic limbs were collected from 11 horses within 6 h of death. Imaging was performed with a 1.5 T magnet using sagittal 2D proton density and transverse 3D FLASH sequences with fat saturation. For the purpose of determining sensitivity and specificity of the MR images, fibrocartilage was classified as normal or abnormal, based on combination of the findings of gross and microscopic pathology. Thickness of fibrocartilage was measured on histologic sections and corresponding transverse FLASH MR images before and after injection of saline. A paired Student's t-test was used for comparison of measurements. Partial thickness fibrocartilage loss was present in 6 of 22 limbs. Sensitivity of precontrast MR images for detection of lesions was 100% while specificity was 6%. Saline MR arthrography resulted in both sensitivity and specificity of 100% based on consensus review. Mean histologic fibrocartilage thickness was 0.75 +/- 0.12 mm. Mean fibrocartilage thickness on precontrast transverse FLASH images was 0.93 +/- 0.065 and 0.73 +/- 0.09 mm on postsaline images. The histologic cartilage thickness was signficantly different from that in precontrast images (P<0.001) but not in images acquired after saline injection (P = 0.716). Based on our results, and using pulse sequences as described herein, navicular fibrocartilage can only be evaluated reliably for the presence of partial thickness lesions after intrabursal injection of saline.

Approach to cartilage injury in the anterior cruciate ligament-deficient knee

The treatment of articular cartilage lesions remains one of the great challenges facing orthopedic surgeons today. The technique of chondrocyte transplantation has opened the door for the application of biologic solutions to difficult problems. These techniques will prove the keystone of further advances into biologic joint repair and replacement. Enthusiasm, however, must be tempered by the numerous gaps in cartilage science and the overwhelming need for further long-term data to demonstrate the efficacy of these techniques in thwarting the presumed eventual progression of these lesions toward osteoarthritis. The status of the articular cartilage is of paramount importance in ACL decision-making. Every effort must be made to protect the existing hyaline articular cartilage during ACL reconstruction. Though current cartilage repair techniques are in their infancy, they remain stepping-stones to future developments. It is hoped that we will one day be able to regenerate normal hyaline cartilage without great morbidity. At present, the ACL surgeon must accept techniques that diminish symptoms and do not burn bridges to future advances. The orthopedic surgeon must increase his knowledge of the basic science of articular cartilage in order to best choose from the various cartilage treatments that evolve.

Magnetic resonance imaging follow-up study of bone bruises associated with anterior cruciate ligament ruptures

PURPOSE

The purpose of this study was to perform a magnetic resonance imaging (MRI) follow-up study of bone bruises in a group of patients with acute anterior cruciate ligament (ACL) ruptures that were reconstructed and followed-up for a minimum of 2 years.

TYPE OF STUDY

Cohort study.

METHODS

The study group included 21 patients with a mean age of 31 years whose initial MRI scans showed associated bone bruises. Patients were included if they had an acute isolated ACL tear, no documentation of an episode of repeated injury to the affected knee during the follow-up period, and no evidence of cartilaginous injury at the time of arthroscopy. All patients had preoperative MRI scans and underwent arthroscopic ACL reconstruction using a bone-patellar tendon autograft an average of 2 months after injury. The preoperative MRI scans were analyzed using a 3-level grading system based on the appearance and location of bone bruises. A second MRI of the knee was obtained from 24 to 64 months postoperatively (average 34 months). The presence of resolution of bone bruises was determined and correlation with clinical scoring established.

RESULTS

This study showed resolution of all type I lesions and 91% of type II lesions (10 of 11). In all type III lesions, an articular cartilage thinning and depression was observed after 2 years of follow-up. In 15 patients (71%), MRI showed that the bone bruises had resolved without apparent sequelae. In the remaining 6 patients (29%), sequelae of the osteochondral lesion were evident on MRI.

CONCLUSIONS

According to our clinical data, there was no correlation between scores obtained from patients with resolved lesions against those with osteochondral sequelae. Although long-term clinical implications of these findings are uncertain, a severe occult osteochondral lesion sustained at the time of ACL rupture seems to be persistent on MRI even after a successful reconstruction.

Magnetic resonance imaging of articular cartilage and evaluation of cartilage disease

Clinical magnetic resonance imaging of articular cartilage is possible by using techniques that offer high contrast between articular cartilage and adjacent structures in reasonable examination times. The fat-suppressed, three-dimensional, spoiled gradient-echo sequence has been reported to be accurate and reliable, and the addition of this sequence to a routine examination does not significantly compromise patient throughput. Fast spin-echo imaging also shows promise in the clinical evaluation of articular cartilage, because the newer, stronger-gradient systems allow thinner slice acquisition with two-dimensional sequences. Together, these sequences allow the evaluation of intrachondral lesions and surface defects. Furthermore, quantitative measurements of cartilage volume for follow-up studies are possible with the use of the fat-suppressed, three-dimensional, spoiled gradient-echo sequence.

Two- to 9-year outcome after autologous chondrocyte transplantation of the knee

Autologous cultured chondrocyte transplantation was introduced in Sweden in 1987 for the treatment of large (1.5-12.0 cm2) full thickness chondral defects of the knee. The clinical, arthroscopic, and histologic results from the first 101 patients treated using this technique are reported in this study. Patients were assessed retrospectively using three types of endpoints: patient and physician derived clinical rating scales (five validated and two new); arthroscopic assessment of cartilage fill, integration, and surface hardness; and standard histochemical techniques. Ninety-four patients with 2- to 9-years followup were evaluable. Good to excellent clinical results were seen in individual groups as follows: isolated femoral condyle (92%), multiple lesions (67%), osteochondritis dissecans (89%), patella (65%), and femoral condyle with anterior cruciate ligament repair (75%). Arthroscopic findings in 53 evaluated patients showed good repair tissue fill, good adherence to underlying bone, seamless integration with adjacent cartilage, and hardness close to that of the adjacent tissue. Hypertrophic response of the periosteum or graft or both was identified in 26 arthroscopies; seven were symptomatic and resolved after arthroscopic trimming. Graft failure occurred in seven (four of the first 23 and three of the next 78) patients. Histologic analysis of 37 biopsy specimens showed a correlation between hyalinelike tissue (hyaline matrix staining positive for Type II collagen and lacking a fibrous component) and good to excellent clinical results. The good clinical outcomes of autologous chondrocyte transplantation in this study are encouraging, and clinical trials are being done to assess the outcomes versus traditional fibrocartilage repair techniques.

Axial and lateral radiographs in evaluating patellofemoral malalignment

This is a prospective study of 431 patients (862 knees) with patellofemoral pain, patellar dislocation, or other abnormalities of the knee joint. There were 217 asymptomatic knees with no contralateral problems for comparison. All patients had a history and physical and radiographic examination of both knees. The radiographs included standard anteroposterior views, axial views at 30 degrees of knee flexion, and standing lateral views at 0 degree and 30 degrees of flexion. The presence of patellar tilt or subluxation was noted on the axial view. The lateral view of the patella, with precise overlap of the posterior femoral condyles, allowed determination of relationships between the patella's medial edge, median ridge, and lateral edge to assess patellar tilt. Sixty-two percent of patients with patellar dislocations demonstrated subluxation on the axial view, while 98% demonstrated an abnormal lateral view. Eighteen percent of the control knees revealed evidence of subluxation on the axial view while 35% demonstrated subluxation on the extended lateral view. The axial view demonstrated 62% sensitivity for dislocation, while the lateral view taken in full extension demonstrated 98% sensitivity. The specificity for previous dislocation was 82% for the axial view and 93% for the lateral flexed view. Given the high sensitivity of the lateral view for detecting prior patellar dislocation, a normal result on this view can virtually eliminate the question of previous dislocation. Also, with the high specificity of the axial view and lateral view with knee flexion, the two views combined can confirm a clinical impression of patellofemoral malalignment.

Knee arthrography. Evolution and current status

This article explores arthrography of the knee beginning with a brief historical perspective of conventional knee arthrography and culminating in direct and indirect MR arthrography of the knee. This article discusses the advantages of MR arthrography in the radiologic assessment of the postoperative meniscus, abnormalities of articular cartilage, and synovial-based processes.

Comparison of MR sequences in quantifying in vitro cartilage degeneration in osteoarthritis of the knee

Magnetic resonance imaging of amputated human knees was performed to determine optimal sequences for depicting articular cartilage. 24 knees were examined with eight different sequences in a 1.0 T imager. Each cartilage lesion was graded from 1 to 4 (Outerbridge staging system). The results of each sequence were compared with the macroscopic findings and statistically tested against each other. The FLASH sequence (TR = 50 ms) with combination of flip angle of 40 degrees and echo time of 10 ms and the FISP sequence (TR = 40 ms) with combination of flip angle of 40 degrees and echo time of 11 ms were best for depicting cartilage structure and internal detail. There was no significant difference between fat-saturated three-dimensional FLASH (FS-3D-FLASH) and FS-3D-FISP (p = 0.05). These FS-3D sequences were significantly better than sequences without fat saturation (p = 0.05). There was no significant difference between magnetization transfer (MT) 3D-FLASH, MT-3D-FISP and 3D-FISP. All 3D sequences showed significantly (p = 0.05) better results than spin echo or fast spin echo sequences. The T1 weighted SE pulse sequence was significantly (p = 0.005) better than the T2 weighted TSE sequence. Fast T2 weighted spin echo was not suitable for early and accurate detection of cartilage lesions.

Low-field magnetic resonance imaging of the canine stifle joint: normal anatomy

Low-field magnetic resonance imaging (MRI) was performed on the stifle joints of four normal adult mongrel dogs using a 0.064 Tesla scanner. Markers were placed on each stifle joint to serve as reference points for comparing gross sections with the images. A T1-weighted sequence was used to image one stifle joint on each dog in the sagittal plane and the other stifle joint in the dorsal plane. The dogs were euthanized immediately following MRI and the stifle joints frozen intact. Each stifle joint was then embedded in paraffin, again frozen, and sectioned using the markers as reference points. On T1-weighted images, synovial fluid had low signal intensity (dark) compared to the infrapatellar fat pad which had a high signal intensity (bright). Articular cartilage was visualized as an intermediate bright signal and was separated from trabecular bone by a dark line representing subchondral bone. Menisci, fibrous joint capsule, and ligamentous structures appeared dark. In the true sagittal plane, the entire caudal cruciate ligament was often seen within one image slice. The patella was visualized as an intermediate bright signal (trabecular bone) surrounded by a low intensity signal (cortical bone). The trochlea and the intercondylar notch were difficult areas to analyze due to signal volume averaging of the curved surface of these areas and the presence of several types of tissues.

Current concepts in the treatment of articular cartilage defects

Over time, articular cartilage loses the capacity to regenerate itself, making repair of articular surfaces difficult. Lavage and debridement may offer temporary relief of pain for up to 4.5 years, but offer no prospect of long-term cure. Likewise, marrow-stimulation techniques such as drilling, microfracture, or abrasion arthroplasty fail to yield long-term solutions because they typically promote the development of fibrocartilage. Fibrocartilage lacks the durability and many of the mechanical properties of the hyaline cartilage that normally covers articular surfaces. Repair tissue resembling hyaline cartilage can be induced to fill in articular defects by using perichondrial and periosteal grafts. However, these techniques are limited by the amount of tissue available for grafting and the tendency toward ossification of the repair tissue. Autogenous osteochondral arthroscopically implanted grafts (mosaicplasty), or open implantation of lateral patellar facet (Outerbridge technique), requires violation of subchondral bone. Osteochondral allografts risk viral transmission of disease and low chondrocyte viability, in addition to removal of host bone for implantation. Autologous chondrocyte implantation offers the opportunity to achieve biologic repair, enabling the surgeon to repair the joint surface with autologous articular cartilage. With this technique, care must be taken to ensure the safety, viability, and microbial integrity of the autologous cells while they are expanded in culture over a 4- to 5-week period prior to implantation. Surgical implantation requires equal attention to meticulous technique. In the future, physiologic repair also may become possible using mesenchymal stem cells or chondrocytes delivered surgically in an ex vivo-derived matrix. This would allow in vitro manipulation of cells with growth factors, mechanical stimuli, and matrix sizing to allow implantation of mature biosynthetic grafts which would allow treatment of larger defects with decreased rehabilitation and morbidity.

Comparison of an optical catheter office arthroscope with a standard rigid rod-lens arthroscope in the evaluation of the knee

In a prospective, randomized study, 47 patients underwent arthroscopic evaluation of the knee in an operating room setting with both a standard rod-lens arthroscope and a newer flexible optical catheter fiberoptic system. The goal of the study was to assess the diagnostic accuracy of the newer catheter system, which is recommended for use in the office setting. Forty-four patients were included in the data analysis, three were eliminated because we were unable to perform an adequate examination with the catheter scope secondary to intraarticular adhesions or excessive bleeding. A comparison of the two systems revealed an overall underestimation and underrecognition of intraarticular knee pathologic changes. Anterior cruciate ligament tears were missed in 3 of 21 knees; no posterior cruciate ligament tears were detected by the rod-lens arthroscope in 44 knees, but one false-positive result was "seen" using the optical catheter device. Similar trends in diagnosis (sensitivity, 25% to 67%; specificity, 96% to 99%) were seen for tears of the medial and lateral menisci, chondral lesions, and the identification of loose bodies. We conclude from the results of this study that the use of the optical catheter system for arthroscopic evaluation and treatment of the knee in the office setting may result in a significant compromise in visual acuity, resulting in missed and incorrect diagnoses.

The impact of magnetic resonance imaging of the knee on surgical decision making

Although magnetic resonance imaging (MRI) of the knee is known to be an accurate technique for diagnosing soft tissue disorders of the knee, the value of MRI in improving patient outcome is controversial. The purpose of this project was to study the value of MRI in a subgroup of patients with knee pain and disability whose diagnosis was uncertain after standard orthopaedic evaluation. An extensive database was recorded prospectively for each of 208 patients providing clinical data as well as diagnoses from clinical, MRI, and surgical observations. These data were analyzed to determine the effect of MRI on diagnosis and patient outcome regarding surgical decision making. The overall diagnostic accuracy of MRI was determined to be 97% in patients undergoing arthroscopy. MRI differed from the clinical diagnosis in 33% of cases, the most common variance being diagnosis of meniscal tear. After combining the MRI and clinical information, surgical decision making was altered in 27% of cases. In a group of patients with acute knee symptoms, the decision not to proceed with surgery was made in 64% of cases. The study shows that MRI of the knee is a valuable tool for augmenting the diagnostic process. The data further show that MRI is a cost-effective technique for avoiding unnecessary surgery and affects patient outcome by improving surgical decision making.

Chondral delamination of the knee in soccer players

This study reports on the diagnosis and treatment of chondral delamination in the knees of soccer players. The authors attempted to provide a clinical standard for comparison with emerging cartilage repair techniques. Twenty-three consecutive chondral fractures in a homogeneous population of athletes were evaluated using physical examination, magnetic resonance imaging, and arthroscopic examination. All knees were treated with debridement to a stable border and removal of the calcified cartilage base. Results were graded using the scoring system advocated by proponents of chondral transplant. All patients reported pain that limited soccer activities. Effusions occurred in 48%, joint line tenderness in 33%, and crepitus in 19% of the knees. Results from magnetic resonance imaging correlated with arthroscopic examination in 21% of the knees. Arthroscopic examinations revealed lesions on the medial femoral condyle in eight patients, the patella in six, the lateral femoral condyle in six, and the trochlea in three. Athletes returned to play at an average of 10.8 weeks. Repeat arthroscopic procedures in eight cases revealed fibrocartilage at the initial site. There were 6 excellent, 9 good, 0 fair, and 0 poor results at their 1-year followup examinations (15 knees). The definitive diagnosis of chondral delamination relies on a thorough arthroscopic probing of the articular surface. The early functional results of this treatment compare favorably with the autologous transplantation technique. Caution, however, is recommended when treating articular cartilage injuries because no long-term data exists on whether any treatment modality can prevent the development of degenerative joint disease.

MR diagnosis of retropatellar chondral lesions under compression. A comparison with histological findings

PURPOSE

The aim of the study was to improve the chondromalacia patellae (CMP) diagnosis by MR imaging under defined compression of the retropatellar cartilage, using a specially designed knee compressor. The results were compared with histological findings to obtain an MR classification of CMP.

METHOD

MR imaging was performed in in vitro studies of 25 knees from cadavers to investigate the effects of compression on the retropatellar articular cartilage. The results were verified by subsequent histological evaluation.

RESULTS

There was a significant difference in cartilage thickness reduction and signal intensity behaviour under compression according to the stage of CMP.

CONCLUSION

Based on the decrease in cartilage thickness, signal intensity behaviour under compression, and cartilage morphology, the studies permitted an MR classification of CMP into stages I-IV in line with the histological findings. Healthy cartilage was clearly distinguished, a finding which may optimize CMP diagnosis.

Osteoarthritis staging: comparison between magnetic resonance imaging, gross pathology and histopathology in the rhesus macaque

Although osteoarthritis (OA) is the most common cause of articular skeletal disability in humans, assessing progression (staging) with noninvasive methods remains a major clinical problem. Using the rhesus macaque animal model, the objective of this study was to compare OA staging by noninvasive magnetic resonance imaging (MRI) against gross pathology and histopathology. Right knee joints from 18 rhesus macaques were used in this study. Using a four-point ordinal scale for each of the above-mentioned modalities, the lateral and medial femoral condyle and tibial plateau of each knee joint was independently scored for OA severity, i.e. normal, mild OA, moderate OA and severe OA. Correlation between each staging system was performed using Stuart's Tau-c correlation coefficient. By our criteria, MRI staging correlated as well with gross pathology (tau = 0.75) and histopathology (tau = 0.80) as did gross pathology with histopathology (tau = 0.78). Our study shows that MRI is a promising noninvasive modality to evaluate the severity of OA. MRI appears to be sensitive for demarcating the presence and extent of focal OA cartilage lesions. However, at this time, while MRI is sensitive for detecting OA change it cannot distinguish between certain lesions such as superficial cartilage matrix fibrillation and hypertrophy both of which show elevated signal intensity.

Safety of ciprofloxacin therapy in children: magnetic resonance images, body fluid levels of fluoride and linear growth

We evaluated the safety of ciprofloxacin administered in a dose of 15-25 mg/kg for 9-16 days, in a case series of 58 children who were between 8 months and 13 years of age. No arthropathy was observed during therapy and follow-up. Blinded evaluation of 22 pairs of nuclear magnetic resonance scans obtained before and between day 10 and 15 of therapy did not reveal any cartilage damage. After the first dose of ciprofloxacin (10 mg/kg), serum fluoride levels increased at 12 h in 15 of 19 (79%) patients; 24-h urinary fluoride excretion was higher on day 7 compared with basal values in 16 of 18 (88.9%) patients. Height z scores of 53 patients at a mean of 22.5 months of follow-up were not significantly different from basal scores (p = 0.12). In conclusion, ciprofloxacin may be recommended for use in children for short duration when effective alternative antibacterials are unavailable. However, there is a need for further studies to evaluate the tissue accumulation of fluoride and its potential to cause toxic effects.

Osteoarthritis and magnetic resonance imaging: potential and problems

To date, MRI has primarily been used to study anatomical changes, and at a resolution that makes detailed analysis of focal change difficult. This is primarily because cost limits the development and use of tailor made research systems. The detailed analysis of soft tissue, cartilage, and bone marrow images should provide a fruitful non-invasive method to study OA. However, the development of MRI methods to study movement, diffusion and perfusion, and the spatial localisation of spectroscopic information, promises a revolution in the study of the living joint in man.

Comparison between magnetic resonance imaging and arthroscopy in the diagnosis of patellar cartilage lesions: a prospective study

A blind and prospective study was conducted to assess the accuracy of magnetic resonance imaging (MRI) for diagnosing patellar cartilage lesions. Thirty-three consecutive patients undergoing knee arthroscopy were examined by MRI prior to surgery. Imaging was performed in the axial plane on a 1.5-Tesla unit with spin-echo and gradient-echo T1 and T2 sequences. The MRI and arthroscopic data were compared using a four-grade classification and a patellar map which divided the patellar surface into four quadrants. The overall sensitivity of MRI was 84.7% and the specificity 97.2%. The same pit-fall led to two MRI false positives. A perfect correlation of grading was obtained in 76.5%. When discordance was found, the tendency with MRI was commonly to underestimate the grade of the lesions. The MRI accuracy was high in this study in spite of a high rate of low-grade lesions which are difficult to assess. Related criteria for cartilage assessment with MRI and arthroscopy are suggested for further studies.

Comparison of "catheter" and conventional arthroscopy in the diagnosis of knee derangements

The diagnostic efficiency of the Optical Catheter System (OCS), which uses a 1.7-mm arthroscope, was compared with that of conventional arthroscopy in 50 patients with various knee derangements in standard arthroscopic conditions. Correct diagnoses were obtained with the OCS in 98% of anterior cruciate ligament derangements--92%-98% of those involving the medial and lateral meniscus, respectively--and 96% of cartilage disorders. No false-positives were noted for anterior cruciate ligament and meniscus injuries. False-negatives were caused by abundant intraarticular bleeding (no tourniquet was applied) and peripheral meniscus tears and false-positives by synovial superposition resulting in a mistaken diagnosis of patellar chondromalacia. The OCS proved a good diagnostic tool. Its employment, especially in an outpatient setting, should be restricted to a small number of patients and entrusted to expert arthroscopists.

The morphology of articular cartilage assessed by magnetic resonance imaging (MRI). Reproducibility and anatomical correlation

Quantitative assessment of cartilage volume and thickness in a formalin-alcohol fixed specimen of a human patella was conducted with magnetic resonance imaging (MRI), as it is still unclear whether the morphology of normal and damaged cartilage can be accurately demonstrated with this technique. MR imaging was carried out at 1.0 T (section thickness 2 mm, in-plane-resolution 0.39-0.58 mm) with the following pulse sequences: 1) T1-weighted spin-echo, 2) 3D-MPRAGE, 3) 3D-FISP, 4) 3D-MTC-FISP, 5) 3D-DESS, 6) 3D-FLASH. Following imaging, the patella was sectioned perpendicular to the articular surface at intervals of 2 mm with a diamond band-saw. The volume of its cartilage was determined from the anatomical sections and the MR images, using a Vidas IPS 10 image analysing system (Kontron). Measurements were carried out with and without the low-signal layer in the transitional zone between the articular cartilage and the subchondral bone. If the low-signal layer was included, the volume was overestimated with MRI by 16 to 19%. Without the low-signal layer the volumes were less than those determined from the anatomical sections: T1-SE-18.2%, MPRAGE -22.6%, FISP -17.1%, MTC-FISP -9.5%, DESS -9.3% and FLASH -6.1%. The coefficient of variation for a 6-fold determination of the volume amounted to between 6.2% (T1-SE) and 2.6% (FLASH). The FLASH sequence allowed the most valid and reproducible assessment of the cartilage morphology. The remaining difference from the real volume of the cartilage may be due to the fact that the calcified zone of the cartilage is not delineated by MRI.

Treatment of deep cartilage defects in the knee with autologous chondrocyte transplantation

BACKGROUND

Full-thickness defects of articular cartilage in the knee have a poor capacity for repair. They may progress to osteoarthritis and require total knee replacement. We performed autologous chondrocyte transplantation in 23 people with deep cartilage defects in the knee.

METHODS

The patients ranged in age from 14 to 48 years and had full-thickness cartilage defects that ranged in size from 1.6 to 6.5 cm2. Healthy chondrocytes obtained from an uninvolved area of the injured knee during arthroscopy were isolated and cultured in the laboratory for 14 to 21 days. The cultured chondrocytes were then injected into the area of the defect. The defect was covered with a sutured periosteal flap taken from the proximal medial tibia. Evaluation included clinical examination according to explicit criteria and arthroscopic examination with a biopsy of the transplantation site.

RESULTS

Patients were followed for 16 to 66 months (mean, 39). Initially, the transplants eliminated knee locking and reduced pain and swelling in all patients. After three months, arthroscopy showed that the transplants were level with the surrounding tissue and spongy when probed, with visible borders. A second arthroscopic examination showed that in many instances the transplants had the same macroscopic appearance as they had earlier but were firmer when probed and similar in appearance to the surrounding cartilage. Two years after transplantation, 14 of the 16 patients with femoral condylar transplants had good-to-excellent results. Two patients required a second operation because of severe central wear in the transplants, with locking and pain. A mean of 36 months after transplantation, the results were excellent or good in two of the seven patients with patellar transplants, fair in three, and poor in two; two patients required a second operation because of severe chondromalacia. Biopsies showed that 11 of the 15 femoral transplants and 1 of the 7 patellar transplants had the appearance of hyaline cartilage.

CONCLUSION

Cultured autologous chondrocytes can be used to repair deep cartilage defects in the femorotibial articular surface of the knee joint.

Office arthroscopy: a diagnostic alternative

Twenty patients with enigmatic knee symptoms were selected for evaluation by both magnetic resonance imaging (MRI) and office arthroscopy. Office arthroscopy was performed in a standard examination room using a miniature (1.7 mm) fiberoptic arthroscope under local anesthesia. All MRI scans were performed on a state-of-the-art 1.5-T magnet unit, and included specialized cartilage sequences in 7 patients. In 14 patients, 26 areas showed articular cartilage changes by arthroscopy (grade 2-3). Only nine of these areas were detected by MRI (sensitivity 34.6%). There were five false-positive and four false-negative readings of meniscal tears by MRI as compared with office arthroscopy. These results improved when postoperative menisci were excluded. Only one of three anterior cruciate ligament (ACL) disruptions identified by MRI could be verified by arthroscopy. The one posterior cruciate ligament (PCL) disruption was confirmed by both techniques. MRI was superior to arthroscopy in identifying bone contusions, subchondral sclerosis, and medial cruciate ligament (MCL) sprains. Office arthroscopy is an accurate and cost-efficient alternative to MRI in diagnostic evaluation of knee pathology in patients with enigmatic symptomatology.

Arthroscopic meniscectomy in patients over the age of 40

One hundred eighteen patients, aged 40 or older, underwent partial meniscectomy and limited debridement of coexisting grade III or grade IV degenerative articular cartilage lesions. No curettage, abrasion arthroplasty, or subchondral drilling was performed. The average age of the patients was 57 years (range, 40 to 78). The mean followup was 3.3 years (range, 1 to 7). Sixty-three similar patients who also underwent partial meniscectomy but did not have the finding of significant coexisting articular surface erosion were studied for comparison. Of the 118 patients in the group with articular lesions (78 men and 40 women), 71 (60%) rated their improvement as significant, 22 (19%) as moderate, and 15 (13%) as mild; 10 (8%) noted no improvement. Although 98 (83%) were generally satisfied with their result, only 57 (48%) reported satisfaction for sports. However, 89 (75%) had resumed and continued recreational athletic activities. Results tended to be worse in women, in patients older than 60, in those with moderate or severe tibiofemoral radiographic changes, those who had a grade IV articular lesion, and those with longer followup time. Although results were poorer in patients with coexisting grade III or grade IV degenerative arthritis, arthroscopic partial meniscectomy and limited debridement was an acceptably effective procedure in patients over the age of 40.

MRI of the knee joint with a 3-D gradient echo sequence. Equivalent to diagnostic arthroscopy?

Three-dimensional (3-D) gradient echo sequences offer the advantage of volume imaging within a few minutes scanning time and creating thin contiguous slices. An optimized sequence (FISP 3D 40) was evaluated for its potential to detect lesions of the menisci, cruciate ligaments, and articular cartilage in 80 patients compared to arthroscopy as the standard. Magnetic resonance imaging showed a sensitivity of 97.9%, a specificity of 97.3%, and an accuracy of 97.5% for meniscal lesions, and a sensitivity of 100%, a specificity of 97.1%, and an accuracy of 97.5% for lesions of the cruciate ligaments. Based upon morphological criteria normal cartilage was identified in 91.5%, but fibrillation of different depths (grades 1-3) was poorly recognized. All full-thickness defects (grade 4) were recognized. Measurement of mean signal intensity (95% confidence intervals) was more useful to discriminate normal from abnormal cartilage (grades 1-3). This method promises the capability to detect early stages of oestoarthritis in future. The present results show MRI of the knee joint with a 3-D fast imaging technique to be a noninvasive alternative to diagnostic arthroscopy.

Experimental hyaline cartilage lesions: two-dimensional spin-echo versus three-dimensional gradient-echo MR imaging

The value of magnetic resonance (MR) imaging, with two-dimensional (2D) spin-echo and FISP (fast imaging with steady-state precession) and FLASH (fast low-angle shot) three-dimensional (3D) gradient-echo sequences, for the detection of hyaline cartilage defects of the femoral condyle and the tibial plateau, was investigated in an animal model. In eight dogs, the anterior cruciate ligament was transected in one knee joint, resulting in rapid development of osteoarthritis with degeneration of the hyaline cartilage. At autopsy, 24 cartilage lesions were found, which were classified into four grades. The overall detection of cartilage lesions with MR imaging was poor. Only five of the 24 lesions were visible on 2D spin-echo images, while 11 of 24 were visible on 3D FISP images and 15 of 24 were seen on 3D FLASH images. The best results were obtained in advanced stages of cartilage degeneration, involving ulceration and complete abrasion of the cartilage layer. Signal loss or signal intensity increase in the cartilage layer was seen inconsistently in grades 3 and 4 degeneration. In this animal model, 2D spin-echo imaging was inadequate for the diagnosis of hyaline cartilage lesions, while 3D gradient-echo imaging permitted satisfactory diagnosis in only grade 4 cartilage disease.

Magnetic resonance imaging of traumatic knee articular cartilage injuries

The purpose of this study was to assess the sensitivity of magnetic resonance imaging in determining the presence of articular cartilage injuries of the knee with arthroscopy as the standard for comparison. Forty-nine articular cartilage lesions were documented in 28 knees (27 patients) by arthroscopy. There were 22 men and 5 women with an average age of 29 years. Multiplanar magnetic resonance imaging was performed with spin echo and gradient-refocused acquisition in a steady state pulse technique. All of the knees had magnetic resonance imaging done within 4 weeks prior to arthroscopy. The magnetic resonance images were interpreted before arthroscopy and interpreted again after the results of arthroscopy were known to better define the potential learning curve for evaluating chondral lesions and to identify the technical limits of the existing imaging protocol/software. For full-thickness articular cartilage lesions, the prearthroscopy sensitivity of magnetic resonance imaging was 41% (12/29) and the postarthroscopy sensitivity was 83% (24/29). For partial-thickness chondral injury, the prearthroscopy sensitivity of magnetic resonance imaging was 15% (3/20) and the postarthroscopy sensitivity was 55% (11/20). The presence of an intraarticular effusion assisted the detection of chondral lesions because of an "arthrogram" effect. As a noninvasive method of evaluating articular cartilage and despite experienced interpretation and the benefit of retrospective analysis, both the prearthroscopy and the postarthroscopy sensitivity of magnetic resonance imaging was low using the imaging parameters described. Injury to articular cartilage is a frequent cause of knee pain and knee surgery; it is important to note at this time that magnetic resonance imaging cannot reliably exclude the presence of an articular cartilage injury.

Characterizing osteochondral lesions by magnetic resonance imaging

In a double-blind prospective study, 12 patients with osteochondral lesions of either the knee or talus were studied using magnetic resonance imaging (MRI) prior to arthroscopic treatment. MRI correctly staged 11 of the 12 lesions. We developed a new staging system for osteochondral lesions, which accurately correlates MRI with arthroscopic findings.

Magnetic resonance imaging reflects cartilage proteoglycan degradation in the rabbit knee

Cartilage degeneration in osteoarthritis is initiated by a loss of proteoglycan. Intra-articular injection of papain causes a reversible loss of proteoglycan in rabbit knees. Rabbits were scanned with magnetic resonance imaging (MRI), using a 1.5T Signa superconducting magnet with 3 inch surface coil. Spin echo sequences were performed in the coronal and sagittal planes at 0, 24, 48, and 72 h after intra-articular injection of papain to obtain T1, proton density, and T2-weighted images. Cartilage proteoglycan content was measured biochemically and histochemically. Reduced articular cartilage thickness in the MR images of papain-treated knees corresponded to changes in cartilage proteoglycan content.

Detection of articular defects using magnetic resonance imaging: an experimental study

This study evaluates magnetic resonance imaging (MRI) in the detection of surgically created articular defects in bovine knees. A total of 26 articular defects was created in 2 fresh cadaveric cows' knees. The defects created include chondromalacic grade 2 defects, chondral and osteochondral defects from 3 to 15 mm in diameter. The knee joints were repaired in a normal saline bath to exclude air in the joint prior to MR scanning. T1 weighted spin echo (SE) images and 3D gradient echo (FISP 40 degrees 3D) images were obtained. The T1 weighted SE imaging technique detected 15 defects (57.7%) compared with FISP 3D imaging technique detection of 17 defects (65.4%). The two techniques combined enable 21 of 26 defects (80.8%) to be detected. The imaging techniques used in this study were not able to detect chondromalacic defects less than 10 mm in diameter, nor chondral defects less than 5 mm in diameter. However, small osteochondral defects of 3 mm in diameter are detectable provided the depth of the defect is not less than 10 mm. The FISP 3D imaging technique alone is more sensitive in detecting chondral defects. Both imaging techniques have similarly high sensitivities in detecting osteochondral defects. The imaging time for combined T1 weighted SE and FISP 3D sequence is short (16.5 mm) and this combined technique may be useful for MR scanning of knee joints suspected to have articular defects.

Articular cartilage defects of the knee: correlation between magnetic resonance imaging and gross pathology

Magnetic resonance imaging (MRI) of the knee articular cartilage is possible owing to the contrast provided by different signal intensities of adjacent menisci and subchondral bone. The objective of this study was to determine the accuracy of MRI in quantitatively detecting thinning and focal defects of articular cartilage in vivo. High resolution MRI was performed followed by dissection of the knee within one hour of amputations above the knee of eight patients (62-89 years) with peripheral vascular disease. Articular cartilage was examined for erosions, surface irregularities, and appearance. Mean thicknesses of femoral and tibial articular cartilage sagittal sections from MRI were statistically indistinguishable from matched gross thicknesses. In those joints in which cartilage erosions, thinning, or irregularities were detected by MRI the same defects were apparent by gross examination. Cartilage that appeared normal by MRI had a normal gross appearance by gross examination. Thus high resolution MRI can accurately predict gross articular cartilage appearance and thickness, allowing an objective, quantitative, noninvasive assessment of eroded cartilage.

Chondral lesions of the patella evaluated with computed tomography, magnetic resonance imaging, and arthroscopy

In a small series of cadaver knees, experimentally created lesions of the patellar cartilage were compared using contrast computed tomography (CT) and magnetic resonance (MR) imaging. Contrast CT was able to recognize only 50% of the lesions smaller than 3-mm diameter at the first attempt, and none of the lesions of 0.8 mm. MR imaging detected all the lesions, even those as small as 0.8 mm, without use of contrast material. Simultaneously, a prospective clinical study comparing MR diagnoses of chondral lesions with arthroscopic findings was initiated in a series of 54 knees. This clinical study revealed that, concerning patellar chondral lesions, the accuracy of MR imaging compared with arthroscopy (the gold standard) was 81.5%. The sensitivity was 100%, but the specificity only 50% due to the false positives. Reexamination of the MR records enabled us to refine the MR diagnosis and to propose a staging of the chondral lesions. The high rate of false-positive results in our series can be explained by the hypothesis that MR imaging can possibly detect very early lesions, which appear as abnormalities in the deep cartilage layers.

Magnetic resonance imaging of the knee: current status, new directions

A number of techniques for magnetic resonance imaging of the knee are reviewed. Spin-echo imaging sequences are at present the most widely used and are capable of demonstrating a wide range of pathology including cruciate and collateral ligament tears, meniscal abnormalities, and synovial disease. Fast scan imaging provides effective T2-weighting without the time penalty of T2-weighted spin-echo imaging. These fast scan techniques have also permitted the development of novel sequences including radial techniques and three-dimensional Fourier transform/volume acquisition (which may potentially become the imaging technique of choice in the knee). Inversion recovery may play an important role in evaluating cartilage disorders in the future. The strengths of each technique are discussed together with possible clinical applications.

Magnetic resonance in cartilaginous lesions of the knee joint with three-dimensional gradient-echo imaging

Diagnosis of chondromalacia of the patellofemoral joint using three-dimensional gradient-echo sequences was investigated in 41 patients, with arthroscopic verification in 25 patients. In vitro examinations in human cadaveric patellae were performed in order to determine optimal imaging parameters. FLASH (TR = 40 ms, TE = 10 ms, flip angle = 30 degrees) and FISP (TR = 40 ms, TE = 10 ms, flip angle = 40 degrees) were used in clinical studies. Advanced stages of chrondromalacia could be visualized with high sensitivity. In less advanced disease, overstaging was observed. The therapeutically relevant differentiation of major and minor degrees of chondromalacia seems to be possible. 30 degrees FLASH-images in the axial plane proved to be the most efficacious technique for the diagnosis of chondromalacia.