Search

Background: Quantitative magnetic resonance (qMR) can be used to measure macromolecules in tissues and is a potential method of observing early cartilage changes in the development of posttraumatic osteoarthritis. Hypothesis/Purpose: We hypothesized that specific patient and surgical factors affecting cartilage matrix composition after anterior cruciate ligament (ACL) reconstruction (ACLR) can be detected using T1&#961 and T2 relaxation times. Our purpose was to demonstrate this ability in a multicenter feasibility study. Study Design: Case series; Level of evidence, 4. Methods: A total of 54 patients who underwent ACLR underwent bilateral MRI at baseline before surgery and 6 months postoperatively. Operative findings were recorded. T1&#961 and T2 relaxation times were calculated for 6 cartilage regions: the medial femur, lateral femur, medial tibia, lateral tibia, patella, and trochlea. A paired t test compared relaxation times at baseline and 6 months, univariate regression identified regions that influenced patient-reported outcome measures, and analysis of covariance was used to determine the surgical factors that resulted in elevated relaxation times at 6 months. Results: The injured knee had significantly prolonged T1&#961 and T2 relaxation times in the tibiofemoral compartment at baseline and 6 months but had shorter values in the patellofemoral compartment compared with the uninjured knee. Prolonged T1&#961 and T2 times at 6 months were noted for both the injured and uninjured knees. At 6 months, prolongation of T1&#961 and T2 times in the tibial region was associated with lower patient-reported outcome measures. ACLR performed within 30 days of injury had significantly shorter T1&#961 times in the tibial regions, and lateral meniscal tears treated with repair had significantly shorter T1&#961 times than those treated with excision. Conclusion: Prolonged relaxation times in multiple regions demonstrate how the injury affects the entire joint after an ACL tear. Changes observed in the uninjured knee may be caused by increased loading during rehabilitation, especially in the patellofemoral articular cartilage and distal femur. Relaxation times in the tibial regions may be predictive of patient symptoms at 6 months. These same regions are affected by surgical timing as early as 30 days after injury, but this may partially be reflective of the severity of the preoperative injury and the choice of treatment of meniscal tears. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Veterinary Journal / Revue Vétérinaire Canadienne is the property of Canadian Veterinary Medical Association and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Aim: The purpose of this study was to evaluate the intra- and interexaminer resegmentation precision of patellar cartilage T 2 mapping measurements in healthy subjects. Materials and Methods: T 2-weighted images of patellar cartilage for 10 subjects were acquired. Two individuals manually segmented patellar cartilage at each slice location twice, once on each of two separate days. Bulk average and zonal T 2 values for the superficial, middle, and deep layers of cartilage were calculated. The root mean square (RMS) and coefficient of variation (COV) were calculated using the repeated measurements of each slice of each subject by each examiner. Results: The intraexaminer bulk T 2 differences were 0.2±1.0 ms, with an RMS error of 0.7 ms and a COV of 1.9%. The differences of interexaminer bulk T 2 values was 1.0±1.4 ms, with an RMS error of 1.2 ms and a COV of 3.3%. The superficial zone of cartilage had the highest zonal variability of T 2 values. The average interexaminer T 2 values for the superficial, middle and deep zones were 42.2±5.6, 38.1±5.3 and 31.9±4.6 ms, respectively. Conclusion: The interexaminer variability of calculated T 2 values highlights the difficulty of interpreting significant differences of T 2 values which are similar in magnitude. The repeatability measurements of patellar cartilage T 2 values were less than reported intersession T 2 repeatability. [Copyright &y& Elsevier]

Abstract: Purpose: To determine how different methods for calculating T2 affect the resulting T2 values of patellar cartilage. Materials and Methods: T2-weighted images of patellar cartilage for 10 subjects were acquired using two MRI scanners. T2 values of patellar cartilage were calculated using linear, weighted and nonlinear fitting algorithms for a monoexponential decay equation. T2 values were also calculated for the superficial, middle and deep zones of the cartilage. Results: All three methods of calculation resulted in significantly different T2 values (P<.0001). The weighted calculation produced the highest T2 values, and the nonlinear calculation produced the lowest T2 values. The average difference of T2 value between the methods was under 5 ms. Similar results were found in a zonal analysis of the tissue. The nonlinear calculation of T2 consistently had the best fit to the acquired data. Conclusion: The T2 value of patellar cartilage depends on the method of calculation. It is unclear if larger T2 value differences would be seen in subjects diagnosed with osteoarthritis. This study highlights the potential difficulty of comparing different studies with one another based on the method of T2 calculation. [Copyright &y& Elsevier]

The objective of the study was to evaluate tibial cartilage thickness (TCT), T1ρ and T2 values within both loaded and baseline configurations in a cadaveric knee model using a 3D bone based tibial coordinate system. Ten intact cadaveric knees were mounted into an magnetic resonance imaging (MRI) compatible loading device. Morphologic and quantitative MRI (qMRI) images were acquired with the knee in a baseline configuration and after application of 50% body weight. The morphologic images were evaluated for cartilage degeneration using a modified Noyes scoring system. A 3D bone‐based tibial coordinate system was utilized to evaluate regional changes of tibial T1ρ, T2, and cartilage thickness values among regions covered and uncovered by the meniscus. Inter‐regional differences in medial and lateral MRI outcomes were found between loaded and baseline configurations. Cartilage regions covered by the meniscus demonstrated disparate qMRI and TCT results as compared to cartilage regions not covered by the meniscus. The regions covered by meniscus experienced a ~3.5%, ~0.5%, and ~5.5% reduction of T1ρ (p < 0.05, medial and lateral compartments), T2 and TCT, respectively, in both compartments while regions not covered by the meniscus experienced larger reductions of ~10%, ~2%, and ~10.5% reduction of T1ρ (p < 0.05, medial and lateral compartments), T2 and TCT (p < 0.05, lateral compartment only), respectively, in both compartments. T1ρ and T2 decreases following application of 50% body weight load were substantially larger in the tibial regions with modified Noyes grade 3 (n = 2) compared to either healthy regions (n = 85, p < 0.0.003) or regions with modified Noyes grade 2 (n = 13, p < 0.004). Interregional differences in MRI outcomes reflect variations in structure and function, and largely followed a pattern in cartilage regions that were covered or not covered by the meniscus. Results of the current study suggest that ΔT1ρ and ΔT2 values may be sensitive to superficial fissuring, more than baseline or loaded T1ρ or T2 values, or TCT alone, however future studies with additional specimens, with greater variability in OA grade distribution, may further emphasize the current findings. [ABSTRACT FROM AUTHOR]

To understand the mechanical consequences of knee injury requires a detailed analysis of the effect of that injury on joint contact mechanics during activities of daily living. Three-dimensional (3D) knee joint geometric models have been combined with knee joint kinematics to dynamically estimate the location of joint contact during physiological activities--using a weighted center of proximity (WCoP) method. However, the relationship between the estimated WCoP and the actual location of contact has not been defined. The objective of this study was to assess the relationship between knee joint contact location as estimated using the image-based WCoP method, and a directly measured weighted center of contact (WCoC) method during simulated walking. To achieve this goal, we created knee specific models of six human cadaveric knees from magnetic resonance imaging. All knees were then subjected to physiolo-gical loads on a knee simulator intended to mimic gait. Knee joint motion was captured using a motion capture system. Knee joint contact stresses were synchronously recorded using a thin electronic sensor throughout gait, and used to compute WCoC for the medial and lateral plateaus of each knee. WCoP was calculated by combining knee kinematics with the MRI-based knee specific model. Both metrics were compared throughout gait using linear regression. The anteroposterior (AP) location of WCoP was significantly correlated with that of WCoC on both tibial plateaus in all specimens (p < 0.01, 95% confidence interval of Pearson's coefficient r > 0), but the correlation was not significant in the mediolateral (ML) direction for 4/6 knees (p > 0.05). Our study demonstrates that while the location of joint contact obtained from 3D knee joint contact model, using the WCoP method, is significantly correlated with the location of actual contact stresses in the AP direction, that relationship is less certain in the ML direction. [ABSTRACT FROM AUTHOR]

Meniscal implants have been developed in an attempt to provide pain relief and prevent pathological degeneration of articular cartilage. However, as yet there has been no systematic and comprehensive analysis of the effects of the meniscal design variables on meniscal function across a wide patient population, and there are no clear design criteria to ensure the functional performance of candidate meniscal implants. Our aim was to develop a statistically-augmented, experimentally-validated, computational platform to assess the effect of meniscal properties and patient variables on knee joint contact mechanics during the activity of walking. Our analysis used Finite Element Models (FEMs) that represented the geometry, kinematics as based on simulated gait and contact mechanics of three laboratory tested human cadaveric knees. The FEMs were subsequently programmed to represent prescribed meniscal variables (circumferential and radial/axial moduli--Ecm, Erm, stiffness of the meniscal attachments--Slpma, Slamp) and patient variables (varus/valgus alignment--VVA, and articular cartilage modulus--Ec). The contact mechanics data generated from the FEM runs were used as training data to a statistical interpolator which estimated joint contact data for untested configurations of input variables. Our data suggested that while Ecm and Erm of a meniscus are critical in determining knee joint mechanics in early and late stance (peak 1 and peak 3 of the gait cycle), for some knees that have greater laxity in the mid-stance phase of gait, the stiffness of the articular cartilage, Ec, can influence force distribution across the tibial plateau. We found that the medial meniscus plays a dominant load-carrying role in the early stance phase and less so in late stance, while the lateral meniscus distributes load throughout gait. Joint contact mechanics in the medial compartment are more sensitive to Ecm than those in the lateral compartment. Finally, throughout stance, varus-valgus alignment can overwhelm these relationships while the stiffness of meniscal attachments in the range studied have minimal effects on the knee joint mechanics. In summary, our statistically-augmented, computational platform allowed us to study how meniscal implant design variables (which can be controlled at the time of manufacture or implantation) interact with patient variables (which can be set in FEMs but cannot be controlled in patient studies) to affect joint contact mechanics during the activity of simulated walking. [ABSTRACT FROM AUTHOR]

Objective:  The aim of this study was to provide normative ultrashort echo time magnetic resonance imaging (UTE MRI) data of the patellar ligament (PL), cranial cruciate ligament (CrCL) and caudal cruciate ligament (CdCL) in non-lame Beagles., Study Design:  Eight stifles from four subjects obtained immediately postmortem were imaged using UTE MRI in the true sagittal plane. Regions of interest were drawn manually and the total (T2*), short T2* (T2*S) and long T2* (T2*L) values of the signal decay were calculated to evaluate the bound and free water components of the tendon. The T2*S, T2*L and T2* values were compared between the PL, CrCL and CdCL RESULTS:  The mean and standard deviation of T2*S, T2*L and T2* were as follows: 0.54 ± 0.13, 4.65 ± 1.08 and 8.35 ± 0.82 ms for the PL; 0.46 ± 0.14, 5.99 ± 0.52 and 8.88 ± 0.4 ms for the CrCL and 0.41 ± 0.13, 7.06 ± 0.57 and 9.26 ± 0.18 ms for the CdCL. Significant differences were found between the T2*L component of the PL and each CrCL/CdCL and a smaller difference was noted between the T2*L of the CrCL and CdCL ( p  = 0.05). No difference of the T2*S value was found between any of the ligaments., Conclusion:  Establishing normative UTE data of the canine stifle is valuable for comparison in future studies in which normal and damaged ligaments may be evaluated, particularly in those affected limbs in which no instability is identified on physical examination in which normal and damaged ligaments may be evaluated., Competing Interests: None declared, (Thieme. All rights reserved.)

Objective:  The normal canine supraspinatus tendon has properties commonly attributed to damage such as core hyperintensity and increased width. Little is published regarding the normal tendon, including how senescent changes and sex differences may affect the appearance. Conventional magnetic resonance imaging (MRI) techniques provide subjective analysis of tendons based on observer assessment of signal intensity and appearance. Quantitative MRI (qMRI) techniques such as T2 mapping provide an objective comparison of collagen orientation with analysis of a decay constant, T2. This study investigates age and sex related changes in the canine supraspinatus tendon using the qMRI technique of T2 mapping., Study Design:  In this study, 34 tendons of clinically sound male and female dogs (0.6-13 years) were imaged using qMRI T2 mapping techniques. Sagittal plane T2 maps of the supraspinatus tendon were depth-normalized, and profiles compared using two separate four-parameter logistic equations describing T2 mapping profiles as sigmoidal curves. Combined parameters evaluated included range of T2 values, curve steepness, vertical curve shift, lower bound of T2, upper bound of T2 and horizontal curve shift., Results:  A significant reduction in the most central portion of the supraspinatus tendon was found for every increased year in age (-1.56 ± 0.47 milliseconds [-2.56, -0.56, p  = 0.004]). No significant difference in curve parameters was found between sexes., Conclusion:  The reduction in T2 with age suggests a senescent change may be anticipated with the canine supraspinatus tendon., Competing Interests: HSS MRI Laboratory receives institutional research support from GE Healthcare, although no funds were provided for this study., (Thieme. All rights reserved.)

Background: Several previous studies have described broad histologic classifications of peri-prosthetic reactions that likely reflect the underlying mechanism of arthroplasty failure; however, a consensus has not yet been reached about the relative importance of individual observations., Question/purpose: The purpose of this study was to evaluate the inter-examiner repeatability of commonly used histopathologic grading methods, and to determine the utility of assigning a more simple, global categorization in patients undergoing revision THA surgery of implants with a variety of bearing combinations., Methods: Between March 2013 and February 2020, a total of 2131 patients underwent revision hip arthroplasty surgery at a one center, of which 12% (248 of 2131) of patients were enrolled. Two pathologists independently reviewed microscope slides of periprosthetic tissue from these patients, of which 425 slides (229 hips, 222 subjects) were reviewed by both pathologists. Separate slides were used for a priori training of the pathologists. Slides were evaluated with the Campbell Aseptic Lymphocyte-dominant Vasculitis-Associated Lesion (ALVAL) score, the Oxford ALVAL score as modified by Grammatopolous, the Fujishiro and Natu scores, and a proposed simplified pattern classification, similar to that of Krenn et al., that incorporates individual factors of these existing scoring methods and was previously shown to correspond to Magnetic Resonance Imaging findings. Inter-rater agreement was assessed using Gwet's AC1 and AC2 coefficients and correspondence analysis was used to examine associations between individual factors of prior scoring methods with the proposed major pattern., Results: Almost perfect inter-rater repeatability (Gwet's AC2 > 0.8) was found for 71% (15/21) of the individual factors, and substantial interrater agreement was found for the proposed major overall pattern (Gwet's AC1: 0.80, 95%CI: 0.72-0.85). Correspondence analysis was able to explain 89-91% of data variability and was able to identify individual features not commonly associated with a major pattern, but discriminatory of the major pattern, such as "Lymph Cuff Thickness 0.25-0.5″ with ALVAL., Conclusion: In contrast to prior examinations, excellent interrater agreement was found that may be attributable to a priori training of raters with a test set of slides or difficulty of interpreting grading criteria. The proposed simplified major pattern classification may facilitate evaluation of histopathologic tissue samples., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

Background: Hip arthroplasty is increasingly prevalent, and early detection of complications can improve outcomes. Quantitative magnetic resonance imaging (qMRI) methods using multi-acquisition variable-resonance image combination (MAVRIC) may allow for the assessment of soft tissues in close proximity to hip arthroplasty devices. Question/Purposes : We sought to determine the clinical feasibility of MAVRIC-based T2 mapping as a qMRI approach for assessing synovial reactions in patients with a hip arthroplasty device. We hypothesized that there would be differences in T2 metrics by synovial type, clinical impression, and clinical findings related to synovitis. Methods : We conducted a cross-sectional study of 141 subjects with 171 hip arthroplasties with greater than 1 year post-implantation. We enrolled subjects who had had a primary total hip arthroplasty or hip resurfacing arthroplasty between May 2019 and March 2020, excluding those with a revision hip arthroplasty and those with standard safety contraindications for receiving an MRI. Institutional standard 2D fast spin echo (FSE), short-tau inversion recovery (STIR), and susceptibility-reduced MAVRIC morphological MR images were acquired for each hip and followed by a dual-echo acquisition MAVRIC T2 mapping sequence. Results : While 131 subjects (81%) were classified as having a "normal" synovial reaction, significantly longer T2 values were found for fluid synovial reactions compared with mixed reactions. In addition, subjects with synovial dehiscence and decompression present had T2 prolongation. Larger synovial volumes were found in subjects with low-signal intensity deposits. Conclusions : MAVRIC-based T2 mapping is clinically feasible and there are significant quantitative differences based on type of synovial reaction. Patients undergoing hip arthroscopy revision surgery will warrant comparison of T2 values with direct histologic assessment of a tissue sample obtained intraoperatively. The approach used in this study may be used for a quantitative evaluation and monitoring of soft tissues around metal implants., Competing Interests: Declaration of Conflicting Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: HSS has an institutional research agreement (PI: Potter) in place with GE Healthcare. Medical College of Wisconsin has an institutional research agreement (PI: Koch) in place with GE Healthcare. No funding, input, or guidance from GE Healthcare was used in the presented study., (© The Author(s) 2021.)

OBJECTIVE. The objective of our study was to compare the quality and diagnostic utility of the following three metal artifact reduction sequences in evaluating hip arthroplasties: conventional multiacquisition variable-resonance image combination selective (MAVRIC SL), isotropic MAVRIC SL, and reduced-TR isotropic MAVRIC SL. SUBJECTS AND METHODS. Ninety-three hip arthroplasties (85 total hip replacements and eight hip resurfacings [nine bilateral hips]) in 84 patients (38 men and 46 women; mean age ± SD, 69.1 ± 9.7 years old) were imaged and evaluated. A calibration scan determined the number of spectral bins needed for each implant, and isotropic and conventional MAVRIC SL images were acquired. Reduced-TR isotropic MAVRIC SL scans were acquired for 40 arthroplasties. Two board-certified radiologists blinded to MRI acquisition evaluated images for clinical and image quality features and compared images using a mixed-effects ordinal logistic regression model and odds ratios. Rater agreement was assessed with Gwet agreement coefficients. Scanning times were compared using mixed-effects linear regression. Significance was set at p < 0.05. RESULTS. Calibration scans decreased the number of bins needed (median, 12 bins; interquartile range, 10-16 bins). Isotropic MAVRIC SL (mean scanning time, 7 minutes 16 seconds; 95% CI, 7 minutes 7 seconds-7 minutes 25 seconds) acquisitions had the longest scanning time, and conventional (mean, 5 minutes 46 seconds; 95% CI, 5 minutes 37 seconds-5 minutes 55 seconds) and reduced-TR isotropic (5 minutes 28 seconds; 95% CI, 5 minutes 15 seconds-5 minutes 41 seconds) MAVRIC SL acquisitions had scanning times that were similar. Both isotropic and reduced-TR isotropic MAVRIC SL images showed decreased blurring and improved visualization of the synovium and periprosthetic bone compared with conventional MAVRIC SL images ( p < 0.001). Isotropic MAVRIC SL acquisitions more effectively improved signal-to-noise ratio (SNR), visualization of the synovium and periprosthetic bone, and lesion conspicuity and decreased blurring compared with reduced-TR isotropic MAVRIC SL acquisitions ( p < 0.032). CONCLUSION. Isotropic MAVRIC SL acquisitions improve SNR, conspicuity of lesions, and visualization of synovium and periprosthetic bone and decrease blurring compared with conventional MAVRIC SL acquisitions.

Objective:  The purpose of this observational study was to establish normative data for the canine menisci using magnetic resonance imaging (MRI)., Methods:  Ten fresh stifles from five normal male Beagles were obtained from animals with no known lameness. Conventional MRI and ultrashort echo time (UTE) imaging were performed and T 2 * values calculated. Five stifles were assessed histologically., Results:  The caudal horn of the medial meniscus had significantly prolonged T 2 * values (4.6 ± 1.27 ms; p  = 0.002) as compared with the cranial horn of the medial meniscus (3.25 ± 0.86 ms), and the cranial (3.06 ± 0.54 ms) and caudal (3.64 ± 0.72 ms) horns of the lateral meniscus. Histology demonstrated normal tibial, femoral, interior and peripheral meniscal margins, and normal cellularity. The medial meniscus was noted to be obliquely oriented to the scan plane compared with the relatively perpendicular orientation of the lateral meniscus as compared with the bore of the magnet in a limb-extended orientation., Clinical Significance:  Variability of MRI UTE T 2 * is seen in the normal canine meniscus, with prolongation of the caudal horn, medial meniscus. Prolongation may be due to magic angle effects, as the medial meniscus of the Beagle is not perpendicular to the axis of the main magnetic field. Canine meniscal injury is a common sequela to cruciate tear, and detecting meniscal damage is important for directing patient care. The non-invasive quantitative MRI technique of UTE imaging can be used for the evaluation of collagen orientation, while acknowledging inherent regions of prolongation., Competing Interests: None of the authors of this article have a financial or personal relationship with other individuals or organizations which could inappropriately influence or bias the content of this article., (Georg Thieme Verlag KG Stuttgart · New York.)

Objectives:  The purpose of this study was to evaluate regional differences of canine stifle articular cartilage using the quantitative magnetic resonance imaging (MRI) technique of T2 mapping., Methods:  Fourteen stifle joints from seven juvenile male Beagle dogs with no evidence or prior history of pelvic limb lameness were imaged ex vivo using standard of care fast spin echo MRI and quantitative T2 mapping protocols. Regions of interest were compared between the femoral, patellar and tibial cartilages, as well as between the lateral and medial femorotibial compartments. Limbs were processed for histology with standard stains to confirm normal cartilage., Results:  The average T2 value of femoral trochlear cartilage (37.5 ± 2.3 ms) was significantly prolonged ( p  < 0.0001) as compared with the femoral condylar, patellar and tibial condylar cartilages (33.1 ± 1.5 ms, 32.8 ± 2.3 ms, and 28.0 ± 1.7 ms, respectively). When comparing medial and lateral condylar compartments, the lateral femoral condylar cartilage had the longest T2 values (34.8 ± 2.8 ms), as compared with the medial femoral condylar cartilage (30.9 ± 1.9 ms) and lateral tibial cartilage (29.1 ± 2.3 ms), while the medial tibial cartilage had the shortest T2 values (26.7 ± 2.4 ms)., Clinical Significance:  As seen in other species, regional differences in T2 values of the canine stifle joint are identified. Understanding normal regions of anticipated prolongation in different joint compartments is needed when using quantitative imaging in models of canine osteoarthritis., Competing Interests: HSS MRI Laboratory receives institutional research support from General Electric Healthcare; however, no funding was provided for this study. None of the authors of this article have a financial or personal relationship with other individuals or organizations which could inappropriately influence or bias the content of this paper., (Schattauer GmbH Stuttgart.)

Background: Quantitative magnetic resonance (qMR) can be used to measure macromolecules in tissues and is a potential method of observing early cartilage changes in the development of posttraumatic osteoarthritis. Hypothesis/Purpose: We hypothesized that specific patient and surgical factors affecting cartilage matrix composition after anterior cruciate ligament (ACL) reconstruction (ACLR) can be detected using T1ρ and T2 relaxation times. Our purpose was to demonstrate this ability in a multicenter feasibility study., Study Design: Case series; Level of evidence, 4., Methods: A total of 54 patients who underwent ACLR underwent bilateral MRI at baseline before surgery and 6 months postoperatively. Operative findings were recorded. T1ρ and T2 relaxation times were calculated for 6 cartilage regions: the medial femur, lateral femur, medial tibia, lateral tibia, patella, and trochlea. A paired t test compared relaxation times at baseline and 6 months, univariate regression identified regions that influenced patient-reported outcome measures, and analysis of covariance was used to determine the surgical factors that resulted in elevated relaxation times at 6 months., Results: The injured knee had significantly prolonged T1ρ and T2 relaxation times in the tibiofemoral compartment at baseline and 6 months but had shorter values in the patellofemoral compartment compared with the uninjured knee. Prolonged T1ρ and T2 times at 6 months were noted for both the injured and uninjured knees. At 6 months, prolongation of T1ρ and T2 times in the tibial region was associated with lower patient-reported outcome measures. ACLR performed within 30 days of injury had significantly shorter T1ρ times in the tibial regions, and lateral meniscal tears treated with repair had significantly shorter T1ρ times than those treated with excision., Conclusion: Prolonged relaxation times in multiple regions demonstrate how the injury affects the entire joint after an ACL tear. Changes observed in the uninjured knee may be caused by increased loading during rehabilitation, especially in the patellofemoral articular cartilage and distal femur. Relaxation times in the tibial regions may be predictive of patient symptoms at 6 months. These same regions are affected by surgical timing as early as 30 days after injury, but this may partially be reflective of the severity of the preoperative injury and the choice of treatment of meniscal tears.

A 5-year-old, spayed female Weimaraner dog was evaluated for progressive left forelimb lameness localized to the carpus. Magnetic resonance imaging (MRI) was used to arrive at a presumptive diagnosis of intermedioradial carpal (IRC) bone fracture with avascular necrosis (AVN). To the authors' knowledge, this is the first report of naturally occurring AVN of the canine IRC diagnosed using MRI.

Background: Analysis of fresh specimens in research studies is ideal; however, it is often necessary to freeze samples for evaluation at a later time. Limited evaluation of the effect of freeze-thawing of tendon tissue samples on inherent magnetic resonance imaging (MRI) parameters, such as ultrashort echo time (UTE) T2* values, have been performed to date., Methods: This study performed UTE MRI on 14 bovine patellar tendons at harvest and after four consecutive freeze-thaw cycles., Results: Results demonstrated a small but significant reduction (12%) in tendon T2* values after the first freeze thaw cycle, but not after successive cycles. Tendons from juvenile animals with open physis had a significant reduction of T2* following a single freeze thaw cycle, P<0.0001., Conclusions: The results of this study emphasize the importance of using uniform tendon storage protocols when using UTE MRI in preclinical models.

Objective: The purpose of this article is to explain the basic physics of imaging patients with metal implants, explain conflicting information regarding MRI scanning of "MR Conditional" devices, and relate our experience of scanning total joint arthroplasty (TJA) at our institution., Conclusion: MRI near TJA is effective with appropriate imaging protocols and standardized safety precautions. Strict adherence to MR Conditional labeling may preclude broad use of MRI for TJA assessment.

Objective: The objective of our study was to compare the frequency of osseous and soft-tissue abnormalities in patients presenting with hip pain after resurfacing arthroplasty and after total hip arthroplasty (THA), correlate the MRI findings with histologic results, and determine which MRI findings are predictive of aseptic lymphocytic vasculitis-associated lesions., Materials and Methods: The MRI examinations of patients with metal-on-metal hip prostheses placed at resurfacing arthroplasty (n=31) or THA (n=29) were reviewed for osteolysis, synovitis, extracapsular disease, synovial pattern, and mode of decompression into adjacent bursae. Regional muscles and tendons were assessed for tendinosis, tear, atrophy, and edema. Histologic and operative findings were reviewed in 19 patients (20 hips) who underwent revision surgery. Chi-square tests were performed to detect differences between the resurfacing arthroplasty and THA groups. The Wilcoxon rank sum test was performed to detect differences in MRI findings in patients with and those without aseptic lymphocytic vasculitis-associated lesions., Results: Synovitis was detected in 77.4% of resurfacing arthroplasty hips and 86.2% of THA hips. Extracapsular disease was present in 6.5% of resurfacing arthroplasty hips and 10.3% of THA hips. Osteolysis was detected in 9.7% of resurfacing arthroplasty hips and 24.1% of THA hips. There was no difference in the incidence of synovitis (p=0.51), osteolysis (p=0.17), or extracapsular disease (p=0.67) between the resurfacing arthroplasty and THA groups. Patients with aseptic lymphocytic vasculitis-associated lesions had higher volumes of synovitis (p=0.04) than patients without aseptic lymphocytic vasculitis-associated lesions. Extracapsular disease and muscle edema were seen only in patients with aseptic lymphocytic vasculitis-associated lesions., Conclusion: Synovitis is common in patients with metal-on-metal hip prostheses and occurs with a similar incidence after resurfacing arthroplasty and after THA; osteolysis and extracapsular disease are uncommon. The MRI signs most suggestive of aseptic lymphocytic vasculitis-associated lesions are high volumes of synovitis, extracapsular disease, and intramuscular edema.

Objective: The goal of this study was to evaluate the quality of images obtained with a prototype imaging technique, multiacquisition variable-resonance image combination (MAVRIC), compared with fast spin-echo (FSE) images in the evaluation of patients who have undergone hip, shoulder, or knee arthroplasty., Materials and Methods: MRI with metal-artifact reduction FSE and MAVRIC sequences was performed in the care of 122 patients who had undergone 74 hip, 27 shoulder, and 21 knee arthroplasties. The FSE and MAVRIC images were subjectively graded for visualization of the synovium, prosthesis-bone interface, and hip abductors or supraspinatus tendon. The presence of synovitis, osteolysis, or supraspinatus tendon tear was recorded., Results: Visualization of the synovium was significantly better on MAVRIC images than on FSE images of the hip (p < 0.0001), shoulder (p < 0.01), and knee (p < 0.01). Synovitis was detected only on the MAVRIC images of nine subjects (12%) who had undergone hip arthroplasty and five subjects (18%) who had undergone shoulder arthroplasty. Visualization of the periprosthetic bone was significantly better on MAVRIC images of the hip (p < 0.0001), shoulder (p < 0.0001), and knee (p < 0.01). Osteolysis was detected only on the MAVRIC images of 12 subjects (16%) who had undergone hip arthroplasty, six (22%) who had undergone shoulder arthroplasty, and five (24%) who had undergone knee arthroplasty. Visualization of the supraspinatus tendon was significantly better on MAVRIC images (p < 0.0001). Supraspinatus tendon tears in 12 subjects (44%) were detected only on MAVRIC images., Conclusion: MAVRIC complements the information on FSE images after arthroplasty and is a useful additional sequence, particularly when there is concern about synovitis, periprosthetic osteolysis, or the presence of a supraspinatus tendon tear.

Purpose: This study compared the functional kinematic outcome of the temporomandibular joint (TMJ) in patients with end-stage TMJ osteoarthritis before and after TMJ hemijoint replacement surgery., Materials and Methods: Fourteen patients (15 joints), with a mean age of 46.1 years, undergoing metal fossa eminence hemijoint replacement surgery, participated in this study. Each patient's jaw motion was recorded using an electromagnetic tracking device and patient-specific computed tomography images. A visual analog scale patient response questionnaire was used before and after the operation to assess the subjective outcome of the surgery., Results: The mean linear distance (LD) traveled by the incisors increased significantly due to the surgical intervention, from 30.4 +/- 6.9 mm preoperatively to 35.5 +/- 5.3 mm postoperatively (P = .02). The LD of the operated condyle decreased from 14.1 +/- 5.7 mm to 11.4 +/- 6.2 mm, but this was not significant. The mean LD for the unoperated condyle remained similar (preoperative, 13.2 +/- 5.9 mm; postoperative, 13.3 +/- 6.5 mm). The total mandibular rotation increased significantly, from 19.3 +/- 4.9 degrees preoperatively to 24.8 +/- 3.9 postoperatively (P < .01)., Conclusions: Kinematic data support the functional efficiency of hemijoint replacement surgery, with benefits of increased maximal mouth opening, preservation of operated and unoperated condyle translation motion, and increased mandibular rotation.