Accurate positioning of the acetabular component is essential for achieving the best outcome in total hip arthroplasty (THA). However, the acetabular shape and anatomy in severe hip dysplasia (Crowe type IV hips) is different from that of arthritic hips. Positioning the acetabular component in the acetabulum of Crowe IV hips may be surgically challenging, and the usual surgical landmarks may be absent or difficult to identify. We analyzed the acetabular morphology of Crowe type IV hips using CT data to identify a landmark for the ideal placement of the centre of the acetabular component as assessed by morphometric geometrical analysis and its reliability. A total of 52 Crowe IV and 50 normal hips undergoing total hip arthroplasty were retrospectively identified. In this CT-based simulation study, the acetabular component was positioned at the true acetabulum with a radiographic inclination of 40° and anteversion of 20° (Figure 1). Acetabular shape and the position of the centre of the acetabular component were analyzed by morphometric geometrical analysis using the generalized Procrustes analysis (Figure 2). To describe major trends in shape variations within the sample, we performed a principal component analysis of partial warp variables (Figure 3).Aims
Patients and Methods
Dislocation is one of the most important complications in THA. Dual mobility cup (DMC) inserts reduce the risk for dislocation after total hip arthroplasty by increasing the oscillation angle. A lower rate of dislocation with use of a DMC insert has been reported in different studies. But there is no available research that clearly delineates the stability advantages of DMC inserts in primary THA. The aim of our study was to evaluate the area of the safe zone for a DMC insert, compared to a fixed insert for different anteversion angles of the femoral component. A model of the pelvis and femur were developed from computed tomography images. We defined the coordinate system of the pelvis relative to the anterior pelvic plane and the coordinate system of the femur relative to the posterior condylar plane. In our model, we simulated a positive anteversion position of the acetabular cup. The lower border for cup inclination is 50°. The safe zone was evaluated for the following range of motion of the implant: 120° of flexion, 90° of flexion 30° of internal rotation, 30° of extension, 40° of abduction, 40° of adduction, and 30° of external rotation. (Fig.1) The safe zone was calculated for both a fixed insert and a DMC insert over a pre-determined range of three-dimensional motion, and the effect of increasing the anteversion position of the femoral component from 5° to 35° quantified. The ratio of the safe zone for a DMC insert to a fixed insert was calculated.INTRODUCTION
Material and Methods
Compared with the cruciate-retaining (CR) insert for total knee arthroplasty (TKA), the cruciate-substituting (CS) insert has a raised anterior lip, providing greater anterior constraint, and thus, can be used in cases of posterior cruciate ligament (PCL) sacrifice. However, studies have shown that the PCL maintains femoral rollback during flexion, acts as a stabilizer against distal traction force and aids knee joint proprioception; therefore, the argument for PCL excision in CS TKA remains controversial. The purpose of this study was to analyze CS TKA kinematics and identify the role of the PCL. Seven fresh-frozen lower-extremity cadaver specimens were analyzed using Orthomap® Precision Knee Navigation software (Stryker Orthopaedics, Mahwah, NJ, USA). They were surgically implanted with Triathlon® components (Stryker Orthopaedics). The CS insert has a raised anterior lip, and the posterior geometry shares the same profile as the CR, so we can choose retaining or sacrificing the PCL. Six patterns were analyzed: (1) natural knee; (2) only anterior cruciate ligament excision; (3) CS TKA, PCL retention, and bony island preservation; (4) CS TKA, PCL retention, and bony island resection; (5) CS TKA and PCL excision; and (6) CR TKA and PCL excision. Center of the knee and center of the proximal tibia were registered using navigation system, and the magnitudes of the condylar translation were evaluated. And then, using trigonometric function, the magnitude of anterior-posterior translation of the femur was calculated.Introduction
Methods
One of the serious postoperative complications associated with joint replacement is bacterial infection. In our recent investigations, iodine supported titanium implants demonstrated antibacterial activity in both Titanium rods were implanted in intramedullary rabbit femur models, in regard to the cementless hip stem. The implant rods were 5mm in diameter and 25mm in length. Half of the implants were treated with iodine (ID implants) and the other half were untreated (CL implants). The rods were inserted into the distal femur; ID implants into the right femur and CL implants into the left. We assessed the bonding strength by a measuring pull-out test at 4, 8, and 12 weeks after implantation. The bone-implant interfaces were evaluated at 4 weeks after implantation.Background
Methods
Pelvic posterior tilt change (PPTC) after THA is caused by release of joint contracture and degenerative lumbar kyphosis. PPTC increases cup anteversion and inclination and results in a risk of prosthesis impingement (PI) and edge loading (EL). There was reportedly no component orientation of fixed bearing which can avoid PI and EL against 20°PPTC. However, dual mobility bearing (DM) has been reported to have a large oscillation angle and potential to withstand EL without increasing polyethylene (PE) wear against high cup inclination such as 60∼65°. The purpose of this study was to investigate the optimal orientation of DM-THA for avoiding PI and EL against postoperative 20°PPTC.Introduction
Objective
Computer navigation systems are quite sophisticated intra-operative support systems for the precise placement of acetabular or femoral components in THA. However, few studies have addressed the clinical benefits derived from using a navigation system to achieve precise placement of the implants. The purpose of this study is to investigate the early dislocation rate of navigation-assisted primary THA through a posterior approach in order to clarify the short-term benefit of using a computer navigation system. We retrospectively reviewed the early dislocation rate (within 12 months after surgery) of 475 consecutive primary cementless or hybrid THAs with femoral head sizes ≦32mm performed via posterior approach. There were 85 men and 390 women, with a mean age of 60 years (17 to 88) at operation. Preoperative diagnoses included osteoarthritis in 384 hips, osteonecrosis in 45 hips, and others in 46 hips (ex. RA, trauma, infection, congenital disease). All THAs were planned using a 3D templating system based on the combined anteversion theory, performed by single surgeon through a posterior approach with repair of the posterior capsule, assisted by a CT-based surface matching type computer navigation system for cup implantation. All patients were directly followed up at least 1 year after surgery. We classified all 475 joints into four groups: normal or mildly deformed hips (Group A; 308 joints, ex. primary OA, Crowe group 1, osteonecrosis), moderately deformed hips (Group B; 97 joints, ex. Crowe group 2, protrusio acetabuli, Perthes like deformity), severely deformed hips (Group C; 53 joints, ex. Crowe group 3 or 4, ankylosis, fused hip), and neuromuscular and cognitive disorders (Group D; 17 joints), and examined the dislocation rate for each group.Introduction
Methods
The number of total hip arthroplasties has been increasing worldwide, and it is expected that revision surgeries will increase significantly in the near future. Although reconstructing normal hip biomechanics with extensive bone loss in the revision surgery remains challenging. The custom−made acetabular component produced by additive manufacturing, which can be fitted to a patient's anatomy and bone defect, is expected to be a predominant reconstruction material. However, there have been few reports on the setting precision and molding precision of this type of material. The purpose of this study was to validate the custom−made acetabular component regarding postoperative three−dimensional positioning and alignment. Severe bone defects (Paprosky type 3A and 3B) were made in both four fresh cadaveric hip joints using an acetabular reamer mimicking clinical cases of acetabular component loosening or osteolysis in total hip arthroplasty. On the basis of computed tomography (CT) after making the bone defect, two types of custom−made acetabular components (augmented type and tri−flanged type) that adapted to the bone defect substantially were produced by an additive manufacturing machine. A confirmative CT scan was taken after implantation of the component, and then the data were installed in an analysis workstation to compare the postoperative component position and angle to those in the preoperative planning.Introduction
Methods
