This study aimed to develop and validate a fully automated system that quantifies proximal femoral bone mineral density (BMD) from CT images. The study analyzed 978 pairs of hip CT and dual-energy X-ray absorptiometry (DXA) measurements of the proximal femur (DXA-BMD) collected from three institutions. From the CT images, the femur and a calibration phantom were automatically segmented using previously trained deep-learning models. The Hounsfield units of each voxel were converted into density (mg/cm3). Then, a deep-learning model trained by manual landmark selection of 315 cases was developed to select the landmarks at the proximal femur to rotate the CT volume to the neutral position. Finally, the CT volume of the femur was projected onto the coronal plane, and the areal BMD of the proximal femur (CT-aBMD) was quantified. CT-aBMD correlated to DXA-BMD, and a receiver operating characteristic (ROC) analysis quantified the accuracy in diagnosing osteoporosis.Aims
Methods
To compare the effect of femoral bone tunnel configuration on tendon-bone healing in an anterior cruciate ligament (ACL) reconstruction animal model. Anterior cruciate ligament reconstruction using the plantaris tendon as graft material was performed on both knees of 24 rabbits (48 knees) to mimic ACL reconstruction by two different suspensory fixation devices for graft fixation. For the adjustable fixation device model (Socket group; group S), a 5 mm deep socket was created in the lateral femoral condyle (LFC) of the right knee. For the fixed-loop model (Tunnel group; group T), a femoral tunnel penetrating the LFC was created in the left knee. Animals were sacrificed at four and eight weeks after surgery for histological evaluation and biomechanical testing.Objectives
Methods
Patients with hip osteoarthritis have a substantial loss of muscular strength in the affected limb compared to the healthy limb preoperatively, but there is very little quantitative information available on preoperative muscle atrophy and degeneration and their influence on postoperative quality of life (QOL) and the risk of falls. The purpose of the present study were two folds; to assess muscle atrophy and degeneration of pelvis and thigh of patients with unilateral hip osteoarthritis using computed tomography (CT) and to evaluate their impacts on postoperative QOL and the risk of falls. We used preoperative CT data of 20 patients who underwent primary total hip arthroplasty. The following 17 muscles were segmented with our developed semi-automated segmentation method: iliacus, gluteus maximus, gluteus medius, gluteus minimus, rectus femoris, tensor facia lata, adductors, pectinus, piriformis, obturator externus, obturator internus, semimenbranosus, semitendinosus, vastus medialis and vastus lateralis/intermedius (Fig. 1). Volume and radiological density of each muscle were measured. The ratio of those of affected limb to healthy limb was calculated. At the latest follow-up, the WOMAC score was collected and a history of falls after surgery was asked. The average follow- up period was 6 years. Comparison of the volume and radiological density of each muscle between affected and healthy limbs was performed using the Wilcoxon signed rank test. Correlations between the volume and radiological density of each muscle and each score of the WOMAC were evaluated with Spearman's correlation coefficient. The volume and radiological density of each muscle between patients with and without a history of falls were compared using Mann-Whitney U test.Introduction
Methods
Cup anteversion and inclination are important to avoid implant impingement and dislocation in total hip arthroplasty (THA). However, it is well known that functional cup anteversion and cup inclination also change as the pelvic sagittal inclination (PSI) changes, and many reports have been made to investigate the PSI in supine and standing positions. However, the maximum numbers of subjects studied are around 150 due to the requirement of considerable manual input in measuring the PSIs. Therefore, PSI in supine and standing positions were measured fully automatically with a computational method in a large cohort, and the factors which relate to the PSI change from supine to standing were analyzed in this study. A total of 422 patients who underwent THA from 2011 to 2015 were the subjects of this study. There were 83 patients with primary OA, 274 patients with DDH derived secondary OA (DDH-OA), 48 patients with osteonecrosis, and 17 patients with rapidly destructive coxopathy (RDC). The median age of the patient was 61 (range; 15–87). Preoperative PSI in supine and standing positions were measured and the number of cases in which PSI changed more than 10° posteriorly were calculated. PSI in supine was measured as the angle between the anterior pelvic plane (APP) and the horizontal line of the body on the sagittal plane of APP, and PSI in standing was measured as the angle between the APP and the line perpendicular to the horizontal surface on the sagittal plane of APP (Fig. 1). The value was set positive if the pelvis was tilted anteriorly and was set negative if the pelvis tilted posteriorly. Type of hip disease, sex, and age were analyzed with multiple logistic regression analysis if they were related to PSI change of more than 10°. For accuracy verification, PSI in supine and standing were measured manually with the previous manual method in 100 cases and were compared with the automated system used in this study.Background
Methods
The aim of this study was to investigate the effect of granulocyte-colony stimulating factor (G-CSF) on mesenchymal stem cell (MSC) proliferation MSCs from rabbits were cultured in a control medium and medium with G-CSF (low-dose: 4 μg, high-dose: 40 μg). At one, three, and five days after culturing, cells were counted. Differential potential of cultured cells were examined by stimulating them with a osteogenic, adipogenic and chondrogenic medium. A total of 30 rabbits were divided into three groups. The low-dose group (n = 10) received 10 μg/kg of G-CSF daily, the high-dose group (n = 10) received 50 μg/kg daily by subcutaneous injection for three days prior to creating cartilage defects. The control group (n = 10) was administered saline for three days. At 48 hours after the first injection, a 5.2 mm diameter cylindrical osteochondral defect was created in the femoral trochlea. At four and 12 weeks post-operatively, repaired tissue was evaluated macroscopically and microscopically.Objectives
Methods
To achieve 3D kinematic analysis of total knee arthroplasty (TKA), 2D/3D registration techniques which use X-ray fluoroscopic images and computer-aided design (CAD) model of the knee implants, have been applied to clinical cases. These techniques are highly valuable for dynamic 3D kinematic measurement of TKA implants, but have needed time-consuming and labor-intensive manual operations in some process. To overcome a manual operations problem of initial pose estimation for 2D/3D registration, this study proposes an improvement method for semi-automated 3D kinematic measurement of TKA using X-ray fluoroscopic images. To automatically estimate the initial pose of the implant CAD model, we utilise a transformation with feature points extracted from the previous and next frames. A transform matrix which has three degree of freedom (translations parallel to the image, and a rotation perpendicular to the image) is calculated by registration of corresponding feature points between the previous and next frame extracted with speeded up robust features (SURF) algorithm. While, the corresponding point sets extracted by SURF sometimes include some error sets. Therefore, in this study, least median of squares method is employed to detect the error corresponding sets and calculate a transform matrix accurately. Finally, the 3D pose of the model estimated (by the 2D/3D registration) in previous frame is transformed with the accurately calculated transform matrix, and the transformed pose is used as an initial 3D pose of the model (for the 2D/3D registration) in next frame. To validate the feasibility of the improved semi-automated 3D kinematic measurement method, experiments using X-ray fluoroscopic images of four TKA patients during knee motions were performed. In order to assess the performance of the improved method, automation rate was calculated, and the rate was defined as the X-ray frame number of satisfying clinical required accuracy (error within 1mm, 1 degree) relative to all X-ray frame number. As results of the experiments, 3D pose of the model for all X-ray images except for the first frame is automatically stably-estimated, the automation rate of the femoral and tibial component were 83.7 % and 73.5 %, respectively. The improved method doesn't need labor-intensive manual operations for 3D kinematic measurement of TKA, and is thought to be very helpful for actual clinical practice.
To achieve 3D kinematic analysis of total knee arthroplasty (TKA), 2D/3D registration techniques, which use X-ray fluoroscopic images and computer-aided design model of the knee implants, have been applied to clinical cases. In previous feature-based registration methods, only edge contours originated from knee implants are assumed to be extracted from X-ray images before 2D/3D registration. Due to the influence of bone and bone-cement close to knee implants, however, edge detection methods extract unwanted spurious edges and noises in clinical images. Thus, time-consuming and labor-intensive manual operations are often necessary to remove the unwanted edges. It has been a serious problem for clinical applications, and there is a strong demand for development of improved method. The purpose of this study was to develop a pose estimation method to perform accurate 2D/3D registration even if spurious edges and noises exist in knee images. Our 2D/3D registration technique is based on a feature-based algorithm, and contour points from X-ray images are extracted by Gaussian Laplacian filter and zero crossing methods. The basic principle of the algorithm is that the 3D pose of a model can be determined by projecting rays from contour points in an image back to the X-ray focus and noting that all of these rays are tangential to the model surface. Therefore, 3D poses are estimated by minimizing the sum of Euclidean distances between all projected rays and the model surface. Additionally, we introduce robust statistics into the 3D pose estimation method to perform accurate 2D/3D registration even if spurious edges and noises exist in knee images. The robust estimation method employs weight functions to reduce the influence of spurious edges and noises. The weight functions are defined for each contour point, and optimization is performed after the weight functions are multiplied to a cost function.Purpose
Methods
We have developed a CT-based navigation system using infrared light-emitting diode markers and an optical camera. We used this system to perform cementless total hip replacement using a ceramic-on-ceramic bearing couple in 53 patients (60 hips) between 1998 and 2001. We reviewed 52 patients (59 hips) at a mean of six years (5 to 8) postoperatively. The mid-term results of total hip replacement using navigation were compared with those of 91 patients (111 hips) who underwent this procedure using the same implants, during the same period, without navigation. There were no significant differences in age, gender, diagnosis, height, weight, body mass index, or pre-operative clinical score between the two groups. The operation time was significantly longer where navigation was used, but there was no significant difference in blood loss or navigation-related complications. With navigation, the acetabular components were placed within the safe zone defined by Lewinnek, while without, 31 of the 111 components were placed outside this zone. There was no significant difference in the Merle d’Aubigne and Postel hip score at the final follow-up. However, hips treated without navigation had a higher rate of dislocation. Revision was performed in two cases undertaken without navigation, one for aseptic acetabular loosening and one for fracture of a ceramic liner, both of which showed evidence of neck impingement on the liner. A further five cases undertaken without navigation showed erosion of the posterior aspect of the neck of the femoral component on the lateral radiographs. These seven impingement-related mechanical problems correlated with malorientation of the acetabular component. There were no such mechanical problems in the navigated group. We conclude that CT-based navigation increased the precision of orientation of the acetabular component and control of limb length in total hip replacement, without navigation-related complications. It also reduced the rate of dislocation and mechanical problems related to impingement.
There was no statistically significant difference in baseline lesion volume between decreasing lesions and unchanged lesions.
