MR imaging of the knee ligaments and the postoperative knee

MR imaging is an accurate, noninvasive, and cost-effective method for the evaluation of acute knee ligament injuries and in the examination of the postoperative knee. Understanding the normal anatomy and the pertinent clinical aspects of knee injuries is a prerequisite for accurate interpretation of MR imaging studies. The increasing popularity of ACL reconstruction following disruption of this ligament requires knowledge of the various surgical techniques and their MR imaging appearance as well as the appearance of possible complications.     

Computer-assisted instruction: MR imaging of the knee

Computer-assisted education offers a unique method of learning that is complementary to conventional learning techniques. The regional anatomy of musculoskeletal magnetic resonance (MR) imaging lends itself well to discrete learning modules on the computer. This article describes a computer-assisted educational program for MR imaging of the knee. The program is divided into four sections: MR imaging physics, anatomy, pathology, and a quiz. The program has cross-references between the sections that allow comparison of normal versus pathologic findings, review of specified pathologic entities, and self-testing of comprehension. The student can progress through the program in a linear or nonlinear fashion at his or her own pace. All images in the program were digitally acquired with an MR imager and transferred directly to the computer used to develop the program. The program is available throughout the radiology department on a local area network and in the medical school library on stand-alone units. The program is currently being used at a medical school as a supplement to the recently implemented problem-based learning curriculum and for resident education.     

Meniscal position on routine MR imaging of the knee

OBJECTIVE: To determine the prevalence of meniscal protrusion (i.e. location of the outer edge of a meniscus beyond the tibial articular surface), and to determine its relationship with internal derangement, joint effusion, and degenerative arthropathy. DESIGN AND PATIENTS: Sagittal and coronal MR images of 111 abnormal and 46 normal knees were evaluated for the presence of meniscal protrusion. We set 25% as the minimum amount of displacement considered abnormal because this was the smallest amount of displacement we could confidently discern. Presence of meniscal tear, anterior cruciate ligament (ACL) injury, joint effusion, or osteophytosis was also recorded. RESULTS AND CONCLUSION: Normal examinations demonstrated protrusion of the medial meniscus in 6.5% of sagittal images and 15% of coronal images, and of the lateral meniscus in 2% and 13%, respectively. Fisher's exact test demonstrated a statistically significant difference between the normal and abnormal groups for the medial meniscus on both sagittal (P < 0.0001) and coronal (P = 0.01) images, but not for the lateral meniscus in either plane (P > 0.2). A protruding medial meniscus was associated with effusion and osteophytosis (P < 0.05) but not with meniscal or ACL tear (P > 0.1). Posterior protrusion of the lateral meniscus was only associated with ACL injury (P < 0.0001); protruding anterior horns and bodies of lateral menisci were not associated with any of the four abnormalities. It is concluded that the medial meniscus may occasionally protrude more than 25% of its width, but protrusion is more often due to effusion and osteophytes. Protrusion of the posterior horn of the lateral meniscus is associated with ACL insufficiency, while protrusion of the body and anterior horn of the lateral meniscus is a normal variant.     

Relationship between pulse sequences and signal intensity of joint fluid in the gradient-echo MR imaging

Platelet-activating factor (PAF) is a proinflammatory phospholipid mediator implicated in necrotizing enterocolitis. Regulation of PAF-acetylhydrolase (AH), the enzyme degrading PAF, is poorly understood. In this study we found that administration of a dose of PAF (1.5 microg/kg, i.v.), which does not cause gross intestinal injury, increased plasma and intestinal PAF-AH in the rat. Cycloheximide (CHX, 5 mg/kg, i.v.) reduced the activity of plasma (but not intestinal tissue) AH in control, as well as in PAF-injected rats, and aggravated systemic inflammation and tissue injury in the latter. The intestinal necrosis induced by PAF and CHX was ameliorated by posttreatment with WEB2170 (a PAF antagonist), indicating a role of endogenous PAF in mediating injury. Both WEB2170 and anti-TNF antibody reduced PAF-induced AH activity in intestinal tissue, but not in the plasma. Allopurinol largely prevented the injury induced by PAF and CHX, but had no effect on the up-regulation of AH. We conclude: 1) de novo protein synthesis is required to maintain physiologic AH level in the plasma; 2) PAF up-regulates plasma and intestinal AH activity; 3) CHX enhances the injurious effect of PAF; 4) endogenous PAF and TNF also play a role in the up-regulation of intestinal AH; the former probably mediating the intestinal injury by PAF; and 5) reactive oxygen species may mediate the injurious effect of PAF plus CHX, but do not contribute to the regulation of AH by PAF.     

Internal derangement of the knee after ipsilateral femoral shaft fracture: MR imaging findings

OBJECTIVE: This study uses magnetic resonance (MR) imaging to delineate the types and frequencies of injuries seen in the knee after ipsilateral femoral shaft fracture. We also compare the results of the orthopedic knee examination with the MR findings. DESIGN AND PATIENTS: MR imaging of the ipsilateral knee was performed on 34 patients with closed femoral shaft fractures. Indications for knee MR imaging included knee pain at the time of fracture, soft tissue swelling or an effusion of the knee, or a positive knee examination under anesthesia. The patients had a mean age of 27 years and all were stabilized with intramedullary nails. Imaging was performed a mean time of 2.5 days after surgery. All patients had knee examinations done under anesthesia, and the MR results were compiled and compared with the clinical examinations. RESULTS: Ninety-seven percent of patients demonstrated knee effusions. Twenty-seven percent of patients demonstrated meniscal tears, with the posterior horn of the medial meniscus most frequently torn. The medial collateral ligament was the most frequent site of ligamentous injury (38%) followed by the posterior cruciate ligament (21%). Fifty percent of patients had injuries of the extensor mechanism. Bone bruises were noted in 32% of patients. Articular cartilage injuries were confined to the patella in four cases. One occult tibial plateau fracture and one meniscocapsular separation were seen. CONCLUSIONS: There is a common incidence of both ligamentous and meniscal injury to the knee after ipsilateral femoral shaft fracture. MR imaging can be useful in assessing the extent of injury, and may reveal findings unsuspected after clinical examination of the knee.     

Arthroscopy of the knee joint

A manual version and mechanized versions for several types of analyzers are described for the kinetic determination of glucose with glucose dehydrogenase. Results of glucose determinations with and without deproteinization of samples are discussed. The correlation of results with the hexokinase method is shown.     

Characterization of atherosclerotic plaque components by high resolution quantitative MR and US imaging

Dopamine beta-monooxygenase requires copper ions for catalytic activity. The stoichiometry of copper activation has been a matter of discussion, but most of the recent literature agrees on a model with two copper ions per active site. We have now reinvestigated this problem with kinetic experiments at high and low protein levels. The apoenzyme (metal free) is rapidly activated by adding copper. Incremental addition of copper to high levels (up to 10 microM subunits) of enzyme raised the catalytic activity until the stoichiometric relationship between copper and enzyme subunits was 1:1. No increase in activity was observed upon addition of copper in excess of this up to levels of 3 Cu/subunit. Experiments at low protein levels (0.12 microM subunits) revealed that copper activation is described by a hyperbolic, Michaelis-Menten-type curve. This is to be expected for the 1 Cu/subunit model, whereas the 2/1 model predicts sigmoid curves. With an incremental addition of apoenzyme (high level) to a fixed level of copper, a sharp break was again observed at 1 Cu/subunit, and excess apoenzyme showed no evidence of the inhibition predicted by the 2 Cu/subunit model. Steady-state kinetics experiments with variation of the concentrations of copper and the three substrates supported an equilibrium-ordered mechanism, whereby a single activating copper ion is trapped in the active site by the substrates. Treatment of enzyme containing more than 1 Cu/subunit [both the Cu(I) and Cu(II) states were examined] with a chelating column resulted in loss of all copper in excess of 1 Cu/subunit. Reactivation of apoenzyme by vanadyl ions was studied, both as dopamine beta-monooxygenase-catalyzed electron transfer and hydroxylation. The maximal velocity with vanadium was 70% of that with copper, and the activation curve was clearly hyperbolic, again supporting the requirement of only one metal ion per active site. In conclusion, our results support the view that the copper ions bound to dopamine beta-monooxygenase in excess of 1 Cu/subunit are not required for catalysis.     

High resolution, dynamic, magnetic resonance imaging in complicated strabismus

Strabismus cases, especially after previous surgery or trauma to extraocular muscles, often present diagnostic challenges. Conventional clinical tests are helpful in some cases but may be inconclusive. High resolution, dynamic, orbital magnetic resonance imaging (MRI) may yield additional critical information about orbital and extraocular muscle anatomy and function. We report four complicated strabismus cases for which dynamic surface coil MRI helped formulate a precise diagnosis and the most appropriate surgical plan.     

Three-dimensional thickness and volume measurements of the knee joint cartilage by MR tomography: reproducibility in volunteers]

A rapidly expanding number of genetic mechanisms contributing to disease can be accessed via molecular analysis. In order to take full advantage of this potential for genetic diagnostics, and to monitor treatment by gene therapy and other emerging methods, a new generation of diagnostic techniques will be required. Of central importance in future analyses is the possibility to perform very large numbers of simultaneous genetic analyses in analytical devices of small linear dimensions. We have developed a new molecular probe design that is amenable to highly multiplex, specific analyses of total genomic DNA or of RNA molecules expressed in tissue samples. Here, a brief history of gene analytical procedures is presented, followed by a discussion of the properties, means of synthesis and applications of this new class of gene analytic reagents, padlock probes.     

MR arthrography of the glenohumeral joint

The review contains the present-day data on new neurophysiological and neurochemical mechanisms of learning and memory processes disturbances induced by such extreme factors as microwaves, hypoxia [correction of hyghproxia], motion sickness, electro-convulsive shock, etc. The main attention is concentrated on the role of some nootropic drugs in preventing the memory-impairing effect of all these extreme factors. The current concept of the mechanisms action of the nootropics in these extreme conditions is discussed.     

Total endoprosthesis of the knee joint

The results of conduction of 7 operations endoprosthetics of the knee joint using AGC-system of the "Biomet" concern are adduced. Details of operative procedure are enlightened, clinical cases and immediate results of operation are adduced.     

Is knee joint proprioception worse in the arthritic knee versus the unaffected knee in unilateral knee osteoarthritis?

OBJECTIVE: Neuromuscular joint protection requires proprioceptive input and motor output. Impairment of proprioception in knee osteoarthritis (OA) may contribute to, and/or result from, the disease. If this impairment was exclusively a local result of OA, a between-knee difference would be expected in patients with unilateral OA (UOA). To explore causal directions, 2 hypotheses were tested: 1) proprioception is worse in UOA patients versus elderly controls; 2) proprioception is worse in the arthritic knee versus the unaffected knee in UOA patients. METHODS: Twenty-eight UOA patients (Kellgren-Lawrence grade > or =2 in 1 knee and <2 in the other knee) and 29 elderly controls were enrolled. The unaffected knee of each UOA patient and both knees of the elderly controls were required to meet symptom, examination, and radiographic criteria. Proprioception (detection threshold of joint displacement after slow, passive, automated knee motion), body mass index, pain, functional status, range of motion, and laxity were measured. RESULTS: UOA patients had worse proprioception than did elderly controls, in either knee. A between-knee difference was not found in UOA patients. CONCLUSION: Impaired proprioception is not exclusively a local result of disease in knee OA. The relative importance of impaired proprioception in the development and progression of knee OA will require longitudinal study.     

Experimental osteoarthritis in the rabbit knee joint

The development of arthrotic-like changes following the resection of the cruciate ligaments in the knee joint of rabbits has been studied at intervals from 2 weeks to 10 months in 35 animals. Signs of cartilage degeneration were followed by changes in the subchondral bone, where formation of osteophytes and condensation took place. An increased vascular supply was demonstrated by microangiographic and scintigraphic investigations. The uptake of 18F and 99mTc-polyphosphate reached a maximal value about 2 months after the operation and then diminished despite further development of arthrotic changes.     

MR imaging of the gallbladder

Implementation of fast T1- and T2-weighted sequences on state-of-the-art magnetic resonance (MR) imagers increases the potential of MR imaging for examining the gallbladder and permits imaging of both cooperative and acutely ill patients with fewer artifacts. Comprehensive evaluation of gallbladder and biliary tract disease is feasible on new generation MR scanners using MR cholangiographic techniques in combination with tissue imaging sequences (spoiled gradient-echo and fat-suppressed spoiled gradient-echo) and dynamic intravenous gadolinium-chelate administration. Inflammatory and neoplastic diseases of the gallbladder are well shown with these techniques.     

High resolution ultrasound imaging: value in treatment of basocellular carcinoma by cryosurgery

OBJECTIVE: We conducted a prospective evaluation of the contribution of high-resolution ultrasound imaging prior to cryosurgery for basocellular carcinoma and in search for recurrence. PATIENTS AND METHODS: All patients seen between 1992 and 1994 at the skin tumor clinic and treated by cryosurgery were included. Ultrasound imaging using 20 MHz prototype was performed prior to cryosurgery and 2 months later. RESULTS: Among 101 patients treated, 112 basocellular carcinomas were treated by cryosurgery. Ultrasound imaging provided good visualization of the tumor limits in all cases. The ultrasound aspect was anechogenic, often with rare areas of highly dense echoes. The tumor limits described by ultrasound imaging were larger than the clinical limits in 32% of the cases. In 8 of the 16 cases of recurrent tumors, the ultrasound examination revealed the recurrence first. In the other 8 cases, clinical manifestations were confirmed by ultrasonography. In our series, recurrence of basocellular carcinoma was statistically more frequent when the depth of the tumor was 3 mm (ultrasonographic measurement) or when the lateral limits established by ultrasound assessment were greater than the clinical evaluation. DISCUSSION: These findings demonstrate that high-resolution ultrasound imaging of basocellular carcinomas prior to cryosurgery: 1) visualizes tumor limits allowing adapted cryosurgery, 2) identifies factors with predictive value for recurrence, 3) can identify recurrences early. Ultrasound imaging of the skin is a useful non-invasive technique for pre- and post-therapeutic assessment of skin tumors and could be a particularly useful tool for "blind" cryosurgery destruction of skin tumors.     

Arthritic temporomandibular joint: correlation of macromolecular contrast-enhanced MR imaging parameters and histopathologic findings

PURPOSE: To assess the utility of macromolecular contrast material-enhanced magnetic resonance (MR) imaging parameters for determining the histopathologic severity of temporomandibular joint (TMJ) arthritis. MATERIALS AND METHODS: Ovalbumin was used to induce arthritis in the TMJs of 10 previously sensitized adult white rabbits. Five rabbits composed the sham-treated control group. Dynamic spin-echo imaging was performed immediately before and for 30 minutes after injection of macromolecular contrast medium. Histologic specimens of TMJ were assessed quantitatively for arthritis. Changes in MR signal intensity were derived from the synovial and subsynovial tissues of the TMJ, and plasma volume (PV) and permeability surface area product (PS) were calculated. These MR parameters and the arthritic scores were compared between sham-treated and antigen-challenged TMJs. The relationships between MR parameters and histopathologic indexes were also determined. RESULTS: Arthritic TMJs showed marked enhancement of the synovial and subsynovial tissues over the imaging period. PS and all histopathologic indexes of arthritis were significantly greater (P < .005) in antigen-challenged than in sham-treated TMJs. PS demonstrated strong positive relationships with all histologic parameters of arthritis, indicating its utility for assessing the severity of joint inflammation. CONCLUSION: Macromolecular contrast-enhanced MR imaging enables quantification of PS and PV in inflamed joints. This technique may provide insights into the pathogenesis of joint inflammation and noninvasive monitoring of disease severity and treatment response in arthritis.