Evaluation of chondral repair using quantitative MRI

Various quantitative magnetic resonance imaging (qMRI) biomarkers, including but not limited to parametric MRI mapping, semiquantitative evaluation, and morphological assessment, have been successfully applied to assess cartilage repair in both animal and human studies. Through the interaction between interstitial water and constituent macromolecules the compositional and structural properties of cartilage can be evaluated. In this review a comprehensive view of a variety of quantitative techniques, particularly those involving parametric mapping, and their relationship to the properties of cartilage repair is presented. Some techniques, such as T2 relaxation time mapping and delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC), are well established, while the full potential of more recently introduced techniques remain to be demonstrated. A combination of several MRI techniques is necessary for a comprehensive characterization of chondral repair. J. Magn. Reson. Imaging 2012; 36:1287–1299. © 2012 Wiley Periodicals, Inc.     

Ultrasound Arthroscopy of Human Knee Cartilage and Subchondral Bone in Vivo

Arthroscopic ultrasound imaging enables quantitative evaluation of articular cartilage. However, the potential of this technique for evaluation of subchondral bone has not been investigated in vivo. In this study, we address this issue in clinical arthroscopy of the human knee (n = 11) by determining quantitative ultrasound (9 MHz) reflection and backscattering parameters for cartilage and subchondral bone. Furthermore, in each knee, seven anatomical sites were graded using the International Cartilage Repair Society (ICRS) system based on (i) conventional arthroscopy and (ii) ultrasound images acquired in arthroscopy with a miniature transducer. Ultrasound enabled visualization of articular cartilage and subchondral bone. ICRS grades based on ultrasound images were higher (p < 0.05) than those based on conventional arthroscopy. The higher ultrasound-based ICRS grades were expected as ultrasound reveals additional information on, for example, the relative depth of the lesion. In line with previous literature, ultrasound reflection and scattering in cartilage varied significantly (p < 0.05) along the ICRS scale. However, no significant correlation between ultrasound parameters and structure or density of subchondral bone could be demonstrated. To conclude, arthroscopic ultrasound imaging had a significant effect on clinical grading of cartilage, and it was found to provide quantitative information on cartilage. The lack of correlation between the ultrasound parameters and bone properties may be related to lesser bone change or excessive attenuation in overlying cartilage and insufficient power of the applied miniature transducer.     

Carotid intima-media thickness and calcification in relation to bone mineral density in postmenopausal women—The OSTPRE-BBA study

Objectives

Atherosclerosis (AS) and osteoporosis are common diseases in elderly people and may be metabolically related. The aim of this cross-sectional population-based study was to explore the association between common carotid artery intima-media thickness (cIMT), carotid artery calcification (CAC), and BMD in postmenopausal women. In addition, the association of postmenopausal hormone therapy (HT) and selected diseases with cIMT and carotid calcification was studied.

Study design

The 290 women (mean age 73.6 years) included in this Bone Brain Atherosclerosis study (OSTPRE-BBA) were randomly selected from the population-based Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) study cohort, Finland.

Main outcome measures

For this cross-sectional study, cIMT was measured with B-mode ultrasound; femoral neck and total body BMD were measured with dual-energy X-ray absorptiometry.

Results

There were no statistically significant associations between mean cIMT and femoral neck T-score (p > 0.05). However, an increased maximum cIMT was significantly associated with low femoral neck T-score. In the osteoporotic group (T-score <−2.5, n = 20), the maximum cIMT was 2.51 ± 0.88 mm (mean ± SD); in the normal BMD group (T-score >−1, n = 122), it was 1.93 ± 0.64 mm (p = 0.001). The odds of having CAC were approximately four-fold higher in the osteoporotic group compared with the group with a normal femoral neck T-score (odds ratio [OR] = 4.2, p = 0.038). The maximum cIMT was smaller in HT users (1.98 ± 0.56 mm, n = 190) than in non-users (2.16 ± 0.74 mm, n = 156, p = 0.036).

Conclusions

The results of our population-based study suggest that BMD is related to AS, at least in carotid arteries. They indirectly support the hypothesis of partially shared pathophysiological mechanisms between these two disorders.     

Comparison of postoperative skeletal stability of maxillary segments after Le Fort I osteotomy,using patient-specific implant versus mini-plate fixation

BackgroundThree-dimensionally (3D) designed osteotomies and customised osteosynthesis are rapidly becoming standard in maxillofacial reconstructive and deformity surgery. Patient-specific implants (PSIs) have been in use for a few years in orthognathic surgery as well. In Le Fort I osteotomy, wafer-free fixation of the maxillary segment can be performed by individually manufactured cutting and drill guides together with PSIs.AimThis retrospective study was performed to compare the postoperative skeletal stability of the maxillary segment fixed by patient-specific implants versus mini-plates after Le Fort I osteotomy.PatientsFifty-one patients were divided into subgroups according to the fixation method and the advancement of the sub-spinal point. The postoperative skeletal stability of the maxillary segment was evaluated from lateral cephalometric radiographs one year postoperatively.ResultsNo statistically significant differences were found between the postoperative skeletal stability of the PSI and mini-plate fixed maxillae. Prospective studies, possibly with 3D fusion analysis, are warranted to confirm the results.ConclusionThe choice between the two fixation methods does not seem to affect the postoperative skeletal stability of the maxillary segments.     

Relation of EEG spectrum progression to loss of responsiveness during induction of anesthesia with propofol.

OBJECTIVE: Our purpose is to find out whether the Loss of obeying a Verbal Command (LVC) and the preceding progression of the EEG frequency patterns are mutually related during an anesthetic induction. METHODS: EEG was analyzed from sixteen patients, anesthetized with a fixed rate infusion of propofol (30 mg/kg/h). An artifact-purified EEG from electrode Fz referenced to the average of mastoid signals was filtered to consecutive 4 Hz frequency passbands with a filter bank. Signal envelope time-series were computed for all the passbands and studied as a function of the elapsed induction time t and as a function of the relative time r, which is t divided by the time of the LVC. RESULTS: A frequency band specific biphasic activity pattern progressed from high towards low frequencies systematically and uniformly in the population studied when presented on the relative time scale r, irrespective of individual responses to the dosage. CONCLUSIONS: The grouping of the individual progression patterns on the r scale indicates a strong relation between the EEG spectral behavior and the LVC. SIGNIFICANCE: EEG may provide phenomenological grounds for a continuous control variable of a sedative drug effect, even in between the discrete clinical end-points.     

Multiparametric MR imaging reveals early cartilage degeneration at 2 and 8 weeks after ACL transection in a rabbit model

In this study, the rabbit model with anterior cruciate ligament transection (ACLT) was used to investigate early degenerative changes in cartilage using multiparametric quantitative magnetic resonance imaging (qMRI). ACLT was surgically induced in the knees of skeletally mature New Zealand White rabbits (n = 14). ACL transected and contralateral knee compartments—medial femur, lateral femur, medial tibia, and lateral tibia—were harvested 2 (n = 8) and 8 weeks (n = 6) postsurgery. Twelve age-matched nonoperated rabbits served as control. qMRI was conducted at 9.4 T and included relaxation times T₁, T₂, continuous-wave T_1ρ (CWT_1ρ), adiabatic T_1ρ (AdT_1ρ), adiabatic T_2ρ (AdT_2ρ), and relaxation along a fictitious field (T_RAFF). For reference, quantitative histology and biomechanical measurements were carried out. Posttraumatic changes were primarily noted in the superficial half of the cartilage. Prolonged T₁, T₂, CWT_1ρ, and AdT_1ρ were observed in the lateral femur 2 and 8 weeks post-ACLT, compared with the corresponding control and contralateral groups (P < .05). Collagen orientation was significantly altered in the lateral femur at 2 weeks post-ACLT compared with the corresponding control group. In the medial femur, all the studied relaxation time parameters, except T_RAFF, were increased 8 weeks post-ACLT, as compared with the corresponding contralateral and control groups (P < .05). Similarly, significant proteoglycan loss was observed in the medial femur at 8 weeks following surgery (P < .05). Multiparametric MRI demonstrated early degenerative changes primarily in the superficial cartilage with T₁, T₂, CWT_1ρ, and AdT_1ρ sensitive to cartilage changes at 2 weeks after surgery.     

Estimation of the Effect of Body Weight on the Development of Osteoarthritis Based on Cumulative Stresses in Cartilage: Data from the Osteoarthritis Initiative

Evaluation of the subject-specific biomechanical effects of obesity on the progression of OA is challenging. The aim of this study was to create 3D MRI-based finite element models of the knee joints of seven obese subjects, who had developed OA at 4-year follow-up, and of seven normal weight subjects, who had not developed OA at 4-year follow-up, to test the sensitivity of cumulative maximum principal stresses in cartilage in quantitative risk evaluation of the initiation and progression of knee OA. Volumes of elements with cumulative stresses over 5 MPa in tibial cartilage were significantly (p < 0.05) larger in obese subjects as compared to normal weight subjects. Locations of high peak cumulative stresses at the baseline in most of the obese subjects showed a good agreement with the locations of the cartilage loss and MRI scoring at follow-up. Simulated weight loss (to body mass index 24 kg/m²) in obese subjects led to significant reduction of the highest cumulative stresses in tibial and femoral cartilages. The modeling results suggest that an analysis of cumulative stresses could be used to evaluate subject-specific effects of obesity and weight loss on cartilage responses and potential risks for the progression of knee OA.     

Effects of High‐Impact Training on Bone and Articular Cartilage: 12‐Month Randomized Controlled Quantitative MRI Study

Osteoarthritis and osteoporosis often coexist in postmenopausal women. The simultaneous effect of bone‐favorable high‐impact training on these diseases is not well understood and is a topic of controversy. We evaluated the effects of high‐impact exercise on bone mineral content (BMC) and the estimated biochemical composition of knee cartilage in postmenopausal women with mild knee osteoarthritis. Eighty women aged 50 to 66 years with mild knee osteoarthritis were randomly assigned to undergo supervised progressive exercise three times a week for 12 months (n = 40) or to a nonintervention control group (n = 40). BMC of the femoral neck, trochanter, and lumbar spine was measured by dual‐energy X‐ray absorptiometry (DXA). The biochemical composition of cartilage was estimated using delayed gadolinium‐enhanced magnetic resonance imaging (MRI) cartilage (dGEMRIC), sensitive to cartilage glycosaminoglycan content, and transverse relaxation time (T2) mapping that is sensitive to the properties of the collagen network. In addition, we evaluated clinically important symptoms and physical performance–related risk factors of falling: cardiorespiratory fitness, dynamic balance, maximal isometric knee extension and flexion forces, and leg power. Thirty‐six trainees and 40 controls completed the study. The mean gain in femoral neck BMC in the exercise group was 0.6% (95% CI, –0.2% to 1.4%) and the mean loss in the control group was –1.2% (95% CI, –2.1% to –0.4%). The change in baseline, body mass, and adjusted body mass change in BMC between the groups was significant (p = 0.005), whereas no changes occurred in the biochemical composition of the cartilage, as investigated by MRI. Balance, muscle force, and cardiorespiratory fitness improved significantly more (3% to 11%) in the exercise group than in the control group. Progressively implemented high‐impact training, which increased bone mass, did not affect the biochemical composition of cartilage and may be feasible in the prevention of osteoporosis and physical performance–related risk factors of falling in postmenopausal women. © 2014 American Society for Bone and Mineral Research.