Meniskus- und Bandläsionen

The knee is one of the major weight-bearing joints and is relatively exposed to trauma. Capsuloligamentous structures are essential to provide joint stability and -- in turn -- persistent instability bears a risk for osteoarthritis that needs timely and comprehensive diagnosis. Using MRI it may be beneficial to routinely apply (T)SE sequences in all three major planes as a basic protocol and to add additional sequences according to the clinical information available and imaging findings in the basic protocol. Especially fat-suppressed sequences (STIR, T2w/PDw FS TSE) are very useful because they sensitively depict bone marrow edema pattern (BMEP)-like changes. This finding often alerts the reader to -- sometimes only discrete -- underlying pathologies and may -- if found in typical locations -- give information about the mechanism of injury and thus lead the radiologist to look for specific concomitant capsuloligamentous, cartilage, and/or meniscal injury. BMEP is quite prominent in contusion injury, whereas often it is but discrete in avulsion lesions. There is extensive literature about the signs, possible pitfalls, and the accuracy of MRI for the diagnosis of specific pathologies such as meniscal tears or cruciate or collateral ligament ruptures. However, combined injuries of more than one structure are frequent and affect the therapeutic approach. Thus, the primary goal of the radiologist is to go beyond the description of any isolated lesion and to give a comprehensive description of (or to reliably exclude) any injury to other structures. A necessary prerequisite to accomplish this is a thorough knowledge of the -- in some locations -- complex anatomic relationships, pitfalls, and locations where lesions typically occur and where they may be overlooked.

[Digital teaching archive. Concept, implementation, and experiences in a university setting]

Film-based teaching files require a substantial investment in human, logistic, and financial resources. The combination of computer and network technology facilitates the workflow integration of distributing radiologic teaching cases within an institution (intranet) or via the World Wide Web (Internet). A digital teaching file (DTF) should include the following basic functions: image import from different sources and of different formats, editing of imported images, uniform case classification, quality control (peer review), a controlled access of different user groups (in-house and external), and an efficient retrieval strategy. The portable network graphics image format (PNG) is especially suitable for DTFs because of several features: pixel support, 2D-interlacing, gamma correction, and lossless compression. The American College of Radiology (ACR) "Index for Radiological Diagnoses" is hierarchically organized and thus an ideal classification system for a DTF. Computer-based training (CBT) in radiology is described in numerous publications, from supplementing traditional learning methods to certified education via the Internet. Attractiveness of a CBT application can be increased by integration of graphical and interactive elements but makes workflow integration of daily case input more difficult. Our DTF was built with established Internet instruments and integrated into a heterogeneous PACS/RIS environment. It facilitates a quick transfer (DICOM_Send) of selected images at the time of interpretation to the DTF and access to the DTF application at any time anywhere within the university hospital intranet employing a standard web browser. A DTF is a small but important building block in an institutional strategy of knowledge management.

[Speech recognition: impact on workflow and report availability]

With ongoing technical refinements speech recognition systems (SRS) are becoming an increasingly attractive alternative to traditional methods of preparing and transcribing medical reports. The two main components of any SRS are the acoustic model and the language model. Features of modern SRS with continuous speech recognition are macros with individually definable texts and report templates as well as the option to navigate in a text or to control SRS or RIS functions by speech recognition. The best benefit from SRS can be obtained if it is integrated into a RIS/RIS-PACS installation. Report availability and time efficiency of the reporting process (related to recognition rate, time expenditure for editing and correcting a report) are the principal determinants of the clinical performance of any SRS. For practical purposes the recognition rate is estimated by the error rate (unit "word"). Error rates range from 4 to 28%. Roughly 20% of them are errors in the vocabulary which may result in clinically relevant misinterpretation. It is thus mandatory to thoroughly correct any transcribed text as well as to continuously train and adapt the SRS vocabulary. The implementation of SRS dramatically improves report availability. This is most pronounced for CT and CR. However, the individual time expenditure for (SRS-based) reporting increased by 20-25% (CR) and according to literature data there is an increase by 30% for CT and MRI. The extent to which the transcription staff profits from SRS depends largely on its qualification. Online dictation implies a workload shift from the transcription staff to the reporting radiologist.

Coracoid tip position on frontal radiographs of the shoulder: a predictor of common shoulder pathologies?

The coracoacromial arch is a static anterior-superior stabilizer of the humeral head. Thus coracoacromial arch inclination, which varies depending on coracoid tip position, may be related to shoulder pathologies. Therefore, we retrospectively analysed coracoid tip positions in the true anterior posterior view of different shoulder pathologies: reference shoulders (n=27), shoulders with rotator cuff tear (supraspinatus tear n=29; subscapularis tear n=21) and shoulders with anterior glenohumeral instability (traumatic n=17; atraumatic n=14). In supraspinatus tear shoulders, the coracoid tip projected onto inferior glenoid half in 86% of cases (type I coracoid), extending more inferiorly compared with reference group (p=0.0002) or subscapularis tear shoulders (p<0.0001). In contrast, 78% of cases with subscapularis tear show the coracoid tip projected onto the superior glenoid half (type II coracoid). Atraumatic glenohumeral instabilities had a more superior coracoid tip position than traumatic instabilities (p=0.04), but no differences were observed on basis of coracoid type or in comparison with normal controls. We conclude that coracoid tip position is highly variable. Since type I coracoids are predominant in shoulders with supraspinatus tears and type II coracoids in shoulders with subscapularis tears, coracoid tip position may thus provide a simple diagnostic complement for a probable site of rotator cuff tears.

High-resolution diffusion tensor imaging of human patellar cartilage: feasibility and preliminary findings

MR diffusion tensor imaging (DTI) was used to analyze the microstructural properties of articular cartilage. Human patellar cartilage-on-bone samples were imaged at 9.4T using a diffusion-weighted SE sequence (12 gradient directions, resolution = 39 x 78 x 1500 microm(3)). Voxel-based maps of the mean diffusivity, fractional anisotropy (FA), and eigenvectors were calculated. The mean diffusivity decreased from the surface (1.45 x 10(-3) mm(2)/s) to the tide mark (0.68 x 10(-3) mm(2)/s). The FA was low (0.04-0.28) and had local maxima near the surface and in the portion of the cartilage corresponding to the radial layer. The eigenvector corresponding to the largest eigenvalue showed a distinct zonal pattern, being oriented tangentially and radially in the upper and lower portions of the cartilage, respectively. The findings correspond to current scanning electron microscopy (SEM) data on the zonal architecture of cartilage. The eigenvector maps appear to reflect the alignment of the collagenous fibers in cartilage. In view of current efforts to develop and evaluate structure-modifying therapeutic approaches in osteoarthritis (OA), DTI may offer a tool to assess the structural properties of cartilage.

Preoperative radiochemotherapy and radical resection for stages II–IV oral and oropharyngeal cancer: outcome of 222 patients

To analyse survival and locoregional control in patients with advanced oral and oropharyngeal squamous cell carcinoma (SCC) after multimodal therapy with preoperative radiochemotherapy (RCT) and radical surgery. We included in this analysis 222 patients who underwent multimodal therapy between 1990 and 2000. Eligible were patients with UICC disease stages II-IV (T2: 33.3%; T3: 12.6%; T4: 54.1%; N0: 45.9%; N1: 17.6%; N2: 33.3%; N3: 3.2%; stage II: 21.1%; stage III: 14.9%; stage IV: 64%). Patients received preoperative radiochemotherapy consisting of Mitomycin C (15-20 mg/m2, day 1) plus 5-Fluorouracil (750 mg/m2/24 h-infusion, days 1-5) and concomitant radiotherapy for a total dose of 50 Gy. Radical locoregional en bloc-resection according to the pretherapeutic tumour extension was carried out in all patients. After a median surveillance period of 72.3 months (24-152 months), 131 patients (59%) were alive, and 91 (41%) patients died; 12 (5%) of them died postoperatively, 46 (21%) due to tumour recurrence, and 33 (15%) deaths were not directly related to the primary tumour. Overall survival probability was 76% after 2 years, and 62% after 5 years. Two- and 5-year local control probability were 88 and 81%, respectively. Regarding the high percentage of stage IV disease in the reported patients, the multimodal concept is an effective therapy offering excellent survival and local control probability.

In vivo cartilage deformation after different types of activity and its dependence on physical training status

BACKGROUND

Knowledge of the deformational behaviour of articular cartilage in vivo is required to understand the pathogenesis of osteoarthritis and the mechanical target environment of prospective cartilage transplant recipients.

OBJECTIVES

To study the in vivo deformational behaviour of patellar and femorotibial cartilage for different types of physiological activities; and to test the hypothesis that in vivo deformation of cartilage is modified by intense physical exercise.

METHODS

Magnetic resonance imaging and 3D digital image analysis were used to determine cartilage volume before and after physical activity in the patella of 12 volunteers (knee bends, squatting, normal gait, running, cycling). Deformation of femorotibial cartilage was investigated in 10 subjects (knee bends, static compression, high impact loading). Patellar cartilage deformation after knee bends was compared in seven professional weight lifters, seven sprinters, and 14 untrained volunteers.

RESULTS

Patellar cartilage deformation was -5.9% after knee bends, -4.7% after squatting, -2.8% after normal walking, -5.0% after running, and -4.5% after cycling. The pattern of patellar cartilage deformation corresponded to the range of motion involved in the particular activity. Tibial cartilage deformation was greatest under high impact loading (-7%), but small for other activities. No significant difference was found between athletes and non-athletic controls.

CONCLUSIONS

Patellar cartilage deformation shows a "dose dependent" response, where more intense loading leads to greater deformation. Relatively little deformation was observed in the femorotibial joint, except during high impact activities. The findings provide no evidence that adult human cartilage properties are amendable to training effects in vivo.

Fixation of zygomatic fractures with a biodegradable copolymer osteosynthesis system: short- and long-term results

Biodegradable osteosynthesis devices can be viewed as addition to, not yet replacement for conventional metal osteosynthesis materials. In a series of 65 patients with zygomatic fractures, a short-term complication/sequelae rate of 22.8% and a long-term complication rate of 9.4% were recorded. Lactosorb plates, panels and screws were the only devices used for osteosynthesis. All complications associated with the biodegradable material could be considered minor and were resolved by the use of minor surgical procedures or conservative measures. The results of this study indicate that treatment of zygomatic fractures with biodegradable osteosynthesis material has no major long-term adverse effects beyond the total material resorption time.

Correlation and sex differences between ankle and knee cartilage morphology determined by quantitative magnetic resonance imaging

OBJECTIVE

To study the correlation between ankle and knee cartilage morphology to test the hypothesis that knee joint cartilage loss in gonarthritis can be estimated retrospectively using quantitative MRI analysis of the knee and ankle and established regression equations; and to test the hypothesis that sex differences in joint surface area are larger in the knee than the ankle, which may explain the greater incidence of knee osteoarthritis in elderly women than in elderly men.

METHODS

Sagittal MR images (3D FLASH WE) of the knee and hind foot were acquired in 29 healthy subjects (14 women, 15 men; mean (SD) age, 25 (3) years), with no signs joint disease. Cartilage volume, thickness, and joint surface area were determined in the knee, ankle, and subtalar joint.

RESULTS

Knee cartilage volumes and joint surface areas showed only moderate correlations with those of the ankle and subtalar joint (r = 0.33 to 0.81). The correlations of cartilage thickness between the two joints were weaker still (r = -0.05 to 0.53). Sex differences in cartilage morphology at the knee and the ankle were similar, with surface areas being -17.5% to -23.5% lower in women than in men.

CONCLUSIONS

Only moderate correlations in cartilage morphology of healthy subjects were found between knee and ankle. It is therefore impractical to estimate knee joint cartilage loss a posteriori in cross sectional studies by measuring the hind foot and then applying a scaling factor. Sex differences in cartilage morphology do not explain differences in osteoarthritis incidence between men and women in the knee and ankle.

Dixyrazine for the prevention of postoperative nausea and vomiting after laparoscopic cholecystectomy

BACKGROUND

The study assessed the efficacy and safety of dixyrazine, an alternative neuroleptic drug to droperidol, in the prophylaxis of postoperative nausea and vomiting (PONV).

METHODS

A total of 197 patients scheduled for laparoscopic cholecystectomy under general anesthesia were randomized to receive either dixyrazine 10 mg or placebo double-blinded at the end of surgery. Scores pertaining to PONV episodes, analgetic supply, rescue medication, adverse events and patient satisfaction were collected over the first 2 h in the PACU and the next 22 h in the ward.

RESULTS

The incidence of PONV over the entire 24-h period was reduced from 32% in the placebo group to 13% in the dixyrazine group (P< or =0.004). The incidence of nausea in the first 2 h was reduced from 15% in the placebo group to 4% in the dixyrazine group (P< or =0.02) and from 12% to 5% in the next 22 h. The incidence of emetic episodes was not different between the two groups. Postoperative shivering was significantly less prevalent in the dixyrazine than in the placebo group (2% vs. 13%; P< or =0008), and opioid analgesics were required significantly less often (61% vs. 75%; P< or =0.01). No significant adverse effects were observed. Patient satisfaction was similar in both groups.

CONCLUSION

Prophylactic dixyrazine is an effective, safe, and cheap antiemetic drug for laparoscopic cholecystectomy without involving any significant adverse events.

Cartilage atrophy in the knees of patients after seven weeks of partial load bearing

OBJECTIVE

It is currently unknown whether human cartilage properties change during short periods of partial load bearing. We used a post-ankle fracture model to explore whether changes in cartilage morphology occur in the knee under conditions of partial load bearing.

METHODS

The knees of 20 patients with Weber type B and type C fractures were examined using magnetic resonance imaging. The first scan was obtained shortly (mean +/- SD 3.2 +/- 3.0 days) after the injury, and a second scan was obtained 7 weeks later (mean +/- SD 50.7 +/- 5.5 days). The morphology (mean and maximum thickness, volume, and surface area) of the patellar, tibial, and femoral cartilage was determined from coronal and axial magnetic resonance images (fat-suppressed gradient-echo).

RESULTS

Between week 0 and week 7, the cross-sectional area of the quadriceps muscle was reduced by 11% (P< 0.001). Changes in the mean (+/-SD) cartilage thickness ranged from -2.9 +/- 3.2% in the patella to -6.6 +/- 4.9% in the medial tibia. No significant change in cartilage morphology of the contralateral knee was observed.

CONCLUSION

Results of this study demonstrate that in a post-ankle fracture model of partial load bearing, cartilage morphology in all knee compartments is subject to significant change. Changes in the femorotibial joint exceeded those in the patella, whereas no change was observed in the contralateral knee. These findings raise the question of whether cartilage is mechanically less competent and particularly vulnerable after states of partial or complete immobilization.

Feasibility of T and Z scores from magnetic resonance imaging data for quantification of cartilage loss in osteoarthritis

OBJECTIVE

T scores (an indicator of the difference between patients and young healthy subjects) and Z scores (an indicator of the difference between patients and age-matched healthy subjects) are used in the diagnosis of osteoporosis and form the current basis for the definition of osteoporosis by the World Health Organization. We tested the feasibility of using T and Z scores derived from quantitative cartilage imaging with magnetic resonance imaging (MRI) for the diagnosis of osteoarthritis (OA).

METHODS

High-resolution MR images of tibial cartilage were acquired from 126 young healthy adults (ages 20-35 years), 24 age-matched elderly healthy adults (ages 50-75 years), 7 OA patients prior to tibial osteotomy, and 7 OA patients prior to knee arthroplasty. Cartilage volume, thickness, surface area, and original joint surface area (before onset of disease) were determined in the medial and lateral tibia.

RESULTS

The cartilage volume of the medial tibia of osteotomy patients with varus malalignment displayed moderate T scores (-1.0), and more negative T scores (-3.8) were observed in knee arthroplasty patients with varus malalignment. Normalization of the cartilage volume to the original joint surface area substantially enhanced the scores in patients undergoing osteotomy (-2.3) and in patients undergoing knee arthroplasty (-5.5), and this was superior to the normalization ratios of cartilage volume to body height and cartilage volume to body weight, in terms of distinguishing the loss of articular cartilage.

CONCLUSION

Quantitative analysis of OA by MRI is feasible using T and Z scores. However, cartilage volume should be normalized to the individual joint surface area in order to maximize the discriminatory power of this technique for the diagnosis of OA.

Effective techniques for reduction of radiation dosage to patients undergoing invasive cardiac procedures

The goal of this study was to improve radiation dose reduction techniques in invasive cardiology and after patients' radiation data had approached minimal levels, to evaluate predictors of their radiation exposure resulting from invasive cardiac procedures. Over the course of 1 year (and 1996 procedures) we minimized cinegraphic frames and runs, as well as fluoroscopy time, and trained ourselves to achieve effective fluoroscopy-saving positioning of blinds and filters toward the regions of interest. We were consequently able to reduce the mean dose-area products (DAP) for coronary angiography and angioplasty, combined interventions, high-frequency rotational atherectomy, and excimer laser angioplasty: from levels of 53.9 Gy cm(2), 79.6 Gy cm(2), 112.3 Gy cm(2), 119.4 Gy cm(2), and 168.0 Gy cm(2) as currently reported in the literature, to 12.9 Gy cm(2), 13.3 Gy cm(2), 25.9 Gy cm(2), 33.0 Gy cm(2), and 27.1 Gy cm(2), respectively. The mean DAP due to interventions in acute myocardial infarction was 38.3 Gy cm(2). DAP was influenced by body mass index, complexity of coronary artery disease, tube angulation, documented structure, coronary recanalization, emergency circumstances, and the percutaneous transluminal coronary angioplasty (PTCA) target vessel involved, but not by stent implantation. By favouring radiation-reducing cranial posteroanterior views over standard left anterior oblique views for visualization of the left anterior descending and the diagonal artery, we consequently achieved mean PTCA-DAPs of 10.4 Gy cm(2) and 8.6 Gy cm(2), respectively: levels significantly lower than those for PTCA of the right coronary artery (13.3 Gy cm(2)), left circumflex artery (13.7 Gy cm(2)), and obtuse marginal branch (16.9 Gy cm(2)). In conclusion, enhanced knowledge of radiation dose-reduction techniques significantly reduces patient radiation hazards in invasive cardiology.

Short communication: time of day influences patient radiation exposure from percutaneous cardiac interventions

The objective of this study was to investigate the influence of time of day on patient radiation exposure due to cardiac interventions. The elective interventional workload of one experienced cardiologist documented over the course of 4 months amounted to 325 diagnostic catheterizations and 145 percutaneous coronary interventions (PCI). All radiation parameters documented during diagnostic coronary angiography remained constant throughout the entire day. In contrast, for PCI measurements made from 7:00 a.m. to 1:00 p.m., our study revealed a mean overall dose-area product (DAP) of 11.8+/-6.8 Gy cm(2) (n=115). These radiation exposure levels increased significantly later in the afternoon (n=30) by 28% to a level of 15.0+/-11.1 Gy cm(2) (p<0.045). Cinegraphic DAP increased from 3.7+/-2.7 Gy cm(2) to 5.0+/-3.2 Gy cm(2) (p<0.033). The number of cinegraphic runs and frames rose from 7.9+/-2.9 to 9.1+/-3.1 (p<0.025), and from 136+/-63 to 164+/-70 (p<0.014), respectively. The following conclusion is warranted by our data and should now be confirmed in a wider multicentre study: radiation protection of the patients could be influenced by the fatigue of the cardiologist conducting the procedure. To enhance patient radiation safety, elective percutaneous angioplasty should be scheduled for the first 6 h of the interventionalist's occupational workload. Diagnostic interventions may be safely scheduled later.

Quality of life 2-10 years after combined treatment for advanced oral and oropharyngeal cancer

This study reports the findings of an evaluation of Quality of Life (QOL) in long-term survivors of advanced oral and oropharyngeal cancer treated with preoperative chemoradiotherapy followed by surgery (combined treatment=multimodal therapy). All patients had T2-T4 tumours and all received locoregional radical resection and simultaneous microvascular reconstruction. From 1990 to 1998, 181 patients have been treated at the University Hospital of Cranio-Maxillofacial and Oral Surgery in Vienna. 100 (55%) of these patients were alive and free of disease in 2000. Sixty-seven of them completed the EORTC questionnaires QLQ 30 and QLQ H&N 35. We found these questionnaires to be very good tools for determining QOL, which constitutes part of the therapeutic success. Patients tended to report good to very good QOL. A comparison between groups according to clinical data was conducted as well as a group comparison of patients who claimed especially high or low QOL in the questionnaires. It was found that combined treatment not only offers the best chances for survival, but also allows a subsequent QOL, that is comparable to other forms of therapy.

Mechanical strength of the thoracolumbar spine in the elderly: prediction from in situ dual-energy X-ray absorptiometry, quantitative computed tomography (QCT), upper and lower limb peripheral QCT, and quantitative ultrasound

The objective of this study was to compare the ability of clinically available densitometric measurement techniques for evaluating vertebral strength in elderly individuals. Measurements were related to experimentally determined failure strength in the thoracic and lumbar spine. In 127 specimens (82 women and 45 men, age 80 +/- 10 years), dual-energy X-ray absorptiometry (DXA) was performed at the lumbar spine, femur, radius, and total body, and peripheral-quantitative computed tomography (pQCT) at the distal radius, tibia, and femur under in situ conditions with intact soft tissues. Spinal QCT and calcaneal ultrasound parameters were performed ex situ in degassed specimens. Mechanical failure loads of thoracic vertebrae 6 and 10 (T-6 and -10), and lumbar vertebra 3 (L-3) were determined in axial compression on functional three-segment units. In situ anteroposterior DXA and QCT of the lumbar spine explained approximately 65% of the variability of thoracolumbar failure. A combination of cortical and trabecular density (QCT) provided the best prediction in the lumbar spine. However, this was not the case in the thoracic spine, for which lumbar cortical density (QCT) and DXA provided significantly better estimates than trabecular density (QCT). pQCT was significantly less correlated with the strength of lumbar and thoracic vertebrae (r(2) = 40%), but was equivalent to femoral or radial DXA. pQCT measurements in the lower limb showed no advantage over those at the distal radius. Ultrasound explained approximately 25% of the variability of vertebral failure strength and added independent information to spinal QCT, but not to spinal DXA. These experimental results advocate site-specific assessment of vertebral strength by either spinal DXA or QCT.

Chest imaging with flat-panel detector at low and standard doses: comparison with storage phosphor technology in normal patients

The purpose of this study was to evaluate the performance of standard-dose and low-dose cesium iodide (CsI)-doted amorphous silicon (a-Si) flat-panel detector technology (FDT) as compared with storage-phosphor technology (SPT) in the depiction of relevant anatomical structures in chest radiography. In 75 patients referred for thoracic CT, digital chest radiographs were randomly obtained with either SPT at a standard dose (speed class S400, n=25), standard-dose FDT (S400, n=25) or FDT at a low dose (S800, n=25). Five radiologists evaluated the visibility of eight pulmonary and mediastinal anatomical structures using a five-point rating scale. To determine statistically significant differences between the three groups, the Mann-Whitney U-test was employed. No statistically significant differences were found in the depiction of eight criteria between SPT and standard-dose or low-dose FDT chest radiographs. The performance of FDT S400 was equal to SPT for most criteria and better for retrocardiac structures and soft tissue. FDT S800 was inferior to both SPT and FDT S400. Standard-dose FDT is equivalent to SPT in the depiction of relevant anatomical structures of the chest. Our results also indicate that a dose reduction of 50% with FDT may result in small but not significant decrease of image quality.

Functional anatomy of articular cartilage under compressive loading Quantitative aspects of global, local and zonal reactions of the collagenous network with respect to the surface integrity

OBJECTIVE

To assess the influence of local compressive loading on the arrangement of the collagenous fibers in intact articular cartilage. To quantitate the zonal deformation of intact cartilage under load. To analyse the influence of removal of the tangential zone on the load-induced changes.

MATERIALS AND METHODS

380 cylinder shaped cartilage-on-bone samples (d=7 mm) were harvested from 20 bovine femoral heads. In 120 of them the tangential zone was removed. All samples were loaded for 20 min by 0.42 MPa or 0.98 MPa. After proteoglycan extraction, fixation in 4% formalin, dehydration by increasing concentrations of acetone, critical point drying, freeze-fracturing and gold-coating the samples were analysed by scanning-electron-microscopy.

RESULTS

Fiber bulging away from the center of load occurred in an area larger than the directly loaded one and its extent increased parallel to loading (P< 0.01). Crimp was seen only under the indenter and spread with increasing load from the intermediate zone into the tangential zone and radial zone. The absolute height of tangential zone and intermediate zone together remained constant under all loading situations at the costs of the radial zone. All changes due to loading were fully reversible. Removal of the tangential zone reduced the area of bulging (P< 0.01) but markedly increased the amount of crimp. Overall radial strain was not altered, but overall superficial tangential strain was increased by up to 20% (P< 0.01) and high peaks in the local distribution of superficial tensile strain developed.

CONCLUSIONS

The collagenous architecture is a dynamic property of the articular cartilage adapting to its respective loading situation. Crimp reflects local compressive strain. Under compressive loading larger portions of cartilage than the directly loaded areas are functionally included in the process of load transmission. During this process the tangential zone and the intermediate zone form a common functional unit providing a high degree of fiber cross-linkage as a possible mechanism to increase zonal compressive stiffness. Removal of the tangential zone seems to impair distribution of a locally applied compressive load sideways and leads to a reduced cartilage volume included in the process of load transmission. An intact tangential zone contributes to prevent peaks of surface tensile strain.

Magnetic resonance imaging-based assessment of cartilage loss in severe osteoarthritis: accuracy, precision, and diagnostic value

OBJECTIVE

To examine the in vivo accuracy and precision of magnetic resonance imaging (MRI)-based assessment of cartilage loss in patients with severe osteoarthritis (OA) of the knee.

METHODS

High-resolution MRI images of the tibial cartilage were obtained in 8 patients prior to total knee arthroplasty, using a water-excitation gradient-echo MRI sequence (acquisition time 6 minutes 19 seconds; spatial resolution 1.2 x 0.31 x 0.31 mm3). The MRI measurements were repeated after joint repositioning. The precision of the cartilage volume and thickness computations was determined after 3-dimensional reconstruction. During surgery, the tibial plateaus were resected, and the MRI data were compared with water displacement of surgically retrieved cartilage.

RESULTS

The standard deviation (coefficient of variation) of repeated tibial cartilage volume measurements was 56 mm3 (5.5%) medially and 59 mm3 (3.8%) laterally. The deviation from surgically removed tissue was -13%, on average, with a high linear correlation between both methods (r = 0.98). In patients with varus OA, the tissue loss was estimated to be 1,290 mm3 in the medial tibia and 1,150 mm3 in the lateral tibia, compared with the data in healthy volunteers.

CONCLUSION

Noninvasive quantitative MRI-based analysis of cartilage morphometry in severe OA is accurate, precise, and displays high potential diagnostic value.