Objectives. Hips with metal-on-metal total hip arthroplasty (MoM THA) have a high rate of adverse local tissue reactions (ALTR), often associated with hypersensitivity reactions. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) measures tissue perfusion with the parameter Ktrans (volume transfer constant of contrast agent). Our purpose was 1) to evaluate the feasibility of DCE-MRI in patients with THA and 2) to compare DCE-MRI in patients with MoM bearings with metal-on-polyethylene (MoP) bearings, hypothesising that the perfusion index Ktrans in hips with MoM THA is higher than in hips with MoP THA. Methods. In this pilot study, 16 patients with primary THA were recruited (eight MoM, eight MoP). DCE-MRI of the hip was performed at 1.5 Tesla (T). For each patient, Ktrans was computed voxel-by-voxel in all tissue lateral to the bladder. The mean Ktrans for all voxels was then calculated. These values were compared with respect to implant type and gender, and further correlated with clinical parameters. Results. There was no significant difference between the two bearing types with both genders combined. However, dividing patients by THA bearing and gender, women with MoM bearings had the highest Ktrans values, exceeding those of women with MoP bearings (0.067 min. −1. versus 0.053 min. −1. ; p-value < 0.05) and men with MoM bearings (0.067 min. −1. versus 0.034 min. −1. ; p-value < 0.001). Considering only the men, patients with MoM bearings had lower Ktrans than those with MoP bearings (0.034 min. −1. versus 0.046 min. −1. ; p < 0.05). Conclusion. DCE-MRI is feasible to perform in tissues surrounding THA. Females with MoM THA show high Ktrans values in DCE-MRI, suggesting altered tissue perfusion kinematics which may reflect relatively greater inflammation. Cite this article: Dr P. E. Beaule. Perfusion MRI in hips with metal-on-metal and metal-on-polyethylene total hip arthroplasty: A pilot stud. Bone Joint Res 2016;5:73–79. DOI: 10.1302/2046-3758.53.2000572

Introduction: Partial and total meniscectomy has been shown to result in cartilage degeneration and osteoarthritis in the long term. Thus, research efforts have focused on tissue regeneration following meniscectomy. A novel device has recently been developed which, when implanted in the meniscus, provides a three-dimensional honeycombed matrix for vascular ingrowth and tissue regeneration to replace lost meniscus tissue. To evaluate this vascular ingrowth and tissue regeneration a Dynamic contrast-enhanced MRI non invasive technique was used. Methods: A prospective, non-randomised, single-arm, multi-centre, clinical investigation was conducted in 52 patients with an irreparable medial or lateral meniscal tear or partial meniscus loss, with intact rim. Patients were required to have a stable knee joint or be a candidate for knee joint stabilization within 12 weeks of the index procedure, have an International Cartilage Repair Society (ICRS) classification of Grade I or II, and have undergone no more than 3 previous surgeries on the index knee. Following implantation of the novel scaffold, dynamic contrast-enhanced magnetic resonance imaging (DCMRI) using intravenous gadolinium contrast material was performed at 1 week, and at 3 and 12 months post-implantation. Because the scaffold and normal meniscus tissue lack vascularity, the presence of signal enhancement in the device is an appropriate surrogate for the ingrowth of blood vessels and native tissue into the scaffold. All scans were assessed for neovascularization in the scaffold meniscus and integration of the implanted device. To date DCMRI scans at 3 months are available for 48 of the 52 patients. Full data for all available patients will be presented. Results: Using this non-invasive technique evaluable DCMRI data at 3 months were obtained for 42 of the 48 patients (87.5%), showing vascularity, and therefore the presence of tissue, in 35 of the 48 (72.9%) patients. No enhancement (vascularity) was demonstrated in 6 of the 48 (12.5%) patients. Conclusions: At 3 months post-implantation, vascularization, and therefore tissue ingrowth, was demonstrated using DCMRI in the vast majority of patients treated with the novel meniscus scaffold

Introduction: Interest in the relationships between subchondral bone pathology and cartilage breakdown has been stimulated by the observations that bone marrow edema (BME) is related to both pain and bone remodeling and that the progression of cartilage lesions is greater in joints with significant BME. The hypothesis of this study is that changes in perfusion in subchondral bone bear a functional relationship to bone remodeling and cartilage degradation and are a part of a physicochemical signaling mechanism to osteoblasts. We have utilized dynamic, contrast-enhanced magnetic resonance imaging (MRI) to assess perfusion and BME in osteoarthritis (OA) and osteonecrosis (ON). Methods: Investigation of marrow perfusion in BME was performed in both the Dunkin-Hartley guinea pig model of OA patients and cohort of 26 control patients. The human study was performed on a 1.5T magnet using a dedicated surface coil and STIR [3500/17/150 (TR/TE/TI)] and VIBE [5.50/2.89 (TR/TE); 10° (flip angle)] pulse sequences. We determined pharmacokinetic parameters of marrow perfusion according to the two compartment model of Brix, which is characterized by rate and volume transfer constants that can be derived mathematically from time-signal intensity curves. Results: In the guinea pig model, inflow slope was similar at all ages; kel was decreased in the affected medial, but not in the normal lateral, tibia indicating reduced perfusion and outflow obstruction. Comparison of BME and perfusion metrics with morphological features (Mankin scores and subchondral bone plate thickness) at the medial tibia demonstrates that changes in perfusion dynamics precede bone remodeling and cartilage breakdown by several months. Compared to normal marrow, kinetic parameters of contrast-enhancement in areas of BME included higher initial slope (p< .001), higher A (p< .001), lower kep (p=.004), and lower kel (p< .001). In areas of BME around ON, there was significantly lower A (p=.009) and lower kel (p=.04) compared to BME adjacent to OA, but no significant difference in either initial slope (p=.06) or kep (p=.26). Discussion: To our knowledge, these are the first reports of the use of dynamic, enhanced-MRI to characterize bone marrow perfusion in BME associated with OA and ON. In the Dunkin-Hartley guinea pig, reduced perfusion in BME temporally precede alterations in bone remodeling and appearance of cartilage lesions, and are spatially localized to bone subjacent to eventual cartilage lesions. We have also demonstrated similar perfusion kinetics associated with BME in human ON and OA. Calculations of intraosseous pressure associated with outflow obstruction and decreased perfusion are consistent with measurements made in end-stage ON and OA. Osteoblasts are known to be responsive to flow, pressure, and pO2. Increased pressure and decreased flow associated with outflow obstruction may constitute physicochemical signals to osteoblasts which result in changes in cytokine expression and contribute to trabecular remodeling and cartilage breakdown