Although surgical remedies tend to be the long-term solutions for patients with osteoarthritis (OA), many alternatives exist that offer the potential to slow progression, alleviate pain, and/or restore function. One such option is the unloader OA knee brace. The objective of this study was to assess the in vivo medial joint space narrowing with and without the brace during weight-bearing portion of gait. Twenty subjects were evaluated after being clinically assessed by a single surgeon to be bone-on-bone on the medial side. In vivo gait kinematics were collected using a validated 3D-to-2D fluoroscopic registration technique (Figure 1). Subjects were asked to first walk on a treadmill without a brace (Figure 2), and then, after a qualified technician fit a properly sized brace to each subject, they were asked to walk again (Figure 3). In vivo fluoroscopic images were captured and registered at heel-strike (HS) and mid stance (MS) for both scenarios. CT scans were used to acquire the patient-specific bone models that were used in the registration process.Introduction
Methods
Forward solution joint models (FSMs) can be powerful tools, leading to fast and cost-efficient simulation revealing i The objective of this study was to use the knee FSM to predict the condylar translations and axial rotation of both fixed- and mobile-bearing TKA designs during a deep knee bend activity and to compare these kinematics to known fluoroscopy evaluations.Introduction
Objective
Untreated hip osteoarthritis is a debilitating condition leading to pain, bone deformation, and limited range of motion. Unfortunately, studies have not been conducted under in vivo conditions to determine progressive kinematics variations to a hip joint from normal to pre-operative and post-operative THA conditions. Therefore, the objective was this study was to quantify normal and degenerative hip kinematics, compared to post-operative hip kinematics. Twenty unique subjects were analyzed; 10 healthy, normal subjects and 10 degenerative, subjects analyzed pre-operatively and then again post-operatively after receiving a THA. During each assessment, the subject performed a gait (stance and swing phase) activity under mobile, fluoroscopic surveillance. The normal and diseased subjects had CT scans in order to acquire bone geometry while implanted subjects had corresponding CAD models supplied. Femoral head and acetabular cup centers were approximated by spheres based on unique geometries while the component centers were pre-defined as the center of mass. These centers were used to compare femoral head sliding magnitudes on the acetabular cup during the activity for all subjects. Subjects were noted to have separation with changes in center magnitudes of more than 1 mm during gait. Utilizing 3D-to-2D registration techniques, the hip joint kinematics were derived and assessed. This allowed for visualization of normal subject positioning, pre-op bone deterioration, and implant placement within the bones.Introduction
Methods
Numerous fluoroscopic studies have been conducted to investigate kinematic variabilities of total knee arthroplasty (TKA). In those studies, subjects having a posterior stabilized (PS) TKA experience greater weightbearing knee flexion and posterior femoral rollback of the lateral condyle. In those same studies, subjects did experience a high incidence of variable medial condyle motion and reverse axial rotation, especially occurring when the cam engaged the post. More recently, a PS TKA was designed to accommodate both gender and ethnicity. Therefore, the objective of this study was to assess in vivo kinematics for subjects having this TKA type to determine if subjects having this PS TKA experienced more optimal knee kinematics. Twenty-five subjects in this study were asked to perform a deep knee bend to maximum knee flexion and a step-up maneuver while under fluoroscopic surveillance. All subjects were patients of one experienced surgeon and received the same PS TKA. Using a 3D-2D registration technique, the CAD models, supplied by the sponsoring company, were superimposed over x-ray images at specified increments throughout the fluoroscopic footage. The kinematics were then analyzed to evaluate lateral anterior/posterior (LAP) and medial anterior/posterior (MAP) condyle translation as well as axial rotation of the femur with respect to the tibia.Introduction
Methods
Many fluoroscopic studies on total knee arthroplasty (TKA) have identified kinematic variabilities compared to the normal knee, with many subjects experiencing paradoxical motion patterns. The intent of this study was to investigate the results of a newly designed PCR TKA to determine kinematic variabilities and assess these kinematic patterns with those previously documented for the normal knee. The study involves determining the in vivo kinematics for 80 subjects compared to the normal knee. 10 subjects have a normal knee, 40 have a Journey II PCR TKA and 40 subjects with the Journey II XR TKA (BCR). Although all PCR subjects have been evaluated, we are continuing to evaluate subjects with a BCR TKA. All TKAs were performed by a single surgeon and deemed clinically successful. All subjects performed a deep knee bend from full extension to maximum flexion while under fluoroscopic surveillance. Kinematics were calculated via 3D-to-2D registration at 30° increments from full extension to maximum flexion. Anterior/posterior translation of the medial (MAP) and lateral (LAP) femoral condyles and femorotibial axial rotation were compared during ranges of motion in relation to the function of the cruciate ligaments.Introduction
Methods
Diagnosis of osteoarthritis relies primarily on image-based analyses. X-ray, CT, and MRI can be used to evaluate various features associated with OA including joint space narrowing, deformity, articular cartilage integrity, and other joint parameters. While effective, these exams are costly, may expose the patient to ionizing radiation, and are often conducted under passive, non-weightbearing conditions. A supplemental form of analysis utilizing vibroarthrographic (VAG) signals provides an alternative that is safer and more cost-effective for the patient. The objective of this study is to correlate the kinematic patterns of normal, diseased (pre-operative), and implanted (post-operative) hip subjects to their VAG signals that were collected and to more specifically, determine if a correlation exists between femoral head center displacement and vibration signal features. Of the 28 hips that were evaluated, 10 were normal, 10 were diseased, and 8 were implanted. To collect the VAG signal from each subject, two uniaxial accelerometers were placed on bony landmarks near the joint; one was placed on the greater trochanter of the femur and the other along the anterior edge of the iliac crest. The subjects performed a single cycle gait (stance and swing phase) activity under fluoroscopic surveillance. The CAD models of the implanted components were supplied by the sponsoring company while the subject bone models were created from CT scans. 3D-to-2D registration was conducted on subject fluoroscopic images to obtain kinematics, contact area, and femoral center head displacement. The VAG signals were trimmed to time, passed with a denoise filter and wavelet decomposition.Introduction
Methods
At present, orthopaedic surgeons utilize either CT, MRI or X-ray for imaging a joint. Unfortunately, CT and MRI are quite expensive, non weight-bearing and the orthopaedic surgeon does not receive revenue for these procedures. Although x-rays are cheaper, similar to CT scans, patients incur radiation. Also, all three of these imaging modalities are static. More recently, a new ultrasound technology has been developed that will allow a surgeon to image their patients in 3D. The objective of this study is to highlight the new opportunity for orthopaedic surgeons to use 3D ultrasound as alternative to CT, MRI and X-rays. The 3D reconstruction process utilizes statistical shape atlases in conjunction with the ultrasound RF data to build the patient anatomy in real-time. The ultrasound RF signals are acquired using a linear transducer. Raw RF data is then extracted across each scan line. The transducer is tracked using a 3D tracking system. The location and orientation for each scan line is calculated using the tracking data and known position of the tracker relative to the signal. For each scan line, a detection algorithm extracts the location on the signal of the bone boundary, if any exists. Throughout the scan process, a 3D point cloud is created for each detected bone signal. Using a statistical bone atlas for each anatomy, the patient specific surface is reconstruction by optimizing the geometry to match the point cloud. Missing regions are interpolated from the bone atlas. To validate reconstructed models output models are then compared to models generated from 3D imaging, including CT and MRI.Introduction
Methods
Many fluoroscopic studies on total knee arthroplasty (TKA) have identified kinematic variabilities compared to the normal knee, with many subjects experiencing paradoxical motion patterns. The intent of this research study was to investigate the results of customized-individual-made (CIM) and off-the-shelf (OTS) PS and PCR TKA to determine kinematic variabilities and to assess these kinematic patterns with those previously documented for the normal knee. In vivo kinematics were assessed for 151 subjects – 44 with CIM-PCR, 75 with OTS-PCR, 14 with CIM-PS, and 18 with OTS-PS TKA – using a mobile fluoroscopic system and then evaluated using a 3D-2D registration technique. This was a multicenter evaluation so the group of implants were implanted by two surgeons and selected based on recruitment criteria. Each subject performed a deep knee bend activity (DKB) while under fluoroscopy. The kinematics assessed for each subject were condyle translation (LAP/MAP) and rotation (axial rotation).Introduction
Methods
Hip osteoarthritis can be debilitating, often leading to pain, poor kinematics and limiting range of motion. While the in vivo kinematics of a total hip arthroplasty (THA) are well documented, there is limited information pertaining to the kinematics of native, non-arthritic (normal) hips and degenerative hips requiring a THA. The objective of this study is to evaluate and compare the in vivo kinematics of the normal hip with pre-operative, degenerative hips and post-operative THA. Twenty subjects, ten having a normal hip and ten having a pre-operative, degenerative hip that were analyzed before surgery and then post-operatively after receiving a THA. Each subject was asked to perform gait while under mobile fluoroscopic surveillance. Normal and pre-operative degenerative subjects underwent a CT scan so that 3D models of their femur and pelvis could be created. Using 3D-to-2D registration techniques, the hip joint kinematics were derived and assessed. Femoral head and acetabular cup rotational centers were derived using spheres. The centers of these spheres were used to obtain the femoral head sliding distance on the acetabular cup during the activity. The patient-specific reference femoral head values were obtained from the subjects’ CT scans in a non-weight bearing situation.Introduction
Methods
Previous fluoroscopic studies of total knee arthroplasty (TKA) have revealed significant kinematic differences compared to the normal knee. Often, subjects having a TKA experienced kinematic patterns opposite of the normal knee. Therefore, the objective of this study was to determine the in vivo kinematics of subjects implanted with either a customized-individual-made (CIM) or the traditional (OTS) PS TKA to determine if customization offers a distinct advantage to the patient. In-vivo kinematics were determined for 33 subjects, 15 having a CIM-TKA and 18 having OTS-TKA using a mobile fluoroscopic system and a 3D–2D registration technique. All of the subjects were implanted by a single surgeon and were scored to be clinically successful. Each subject underwent fluoroscopic observation while performing a weight-bearing (WB) deep knee bend (DKB) and chair rise (CR). The two groups were then compared for the range of motion, condyle translation, and axial rotation.Introduction
Methods
Previous in vivo fluoroscopic studies have documented that subjects having a PS TKA experience a more posterior condylar contact position at full extension, a high incidence of reverse axial rotation and mid flexion instability. More recently, a PS TKA was designed with a Gradually Reducing Radius (Gradius) curved condylar geometry to offer patients greater mid flexion stability while reducing the incidence of reverse axial rotation and maintaining posterior condylar rollback. Therefore, the objective of this study was to assess the in vivo kinematics for subjects implanted with a Gradius curved condylar geometry to determine if these subjects experience an advantage over previously designed TKA. In vivo kinematics for 30 clinically successful patients all having a Gradius designed PS fixed bearing TKA with a symmetric tibia were assessed using mobile fluoroscopy. All of the subjects were scored to be clinically successful. In vivo kinematics were determined using a 3D-2D registration during three weight-bearing activities: deep-knee-bend (DKB), gait, and ramp down (RD). Flexion measurements were recorded using a digital goniometer while ground reaction forces were collected using a force plate as well. The subjects then assessed for range of motion, condyle translation and axial rotation and ground reaction forces.Background
Methods
