Aims

To evaluate mid-to long-term patient-reported outcome measures (PROMs) of endoprosthetic reconstruction after resection of malignant tumours arising around the knee, and to investigate the risk factors for unfavourable PROMs.

Accurate cup placement in total hip arthroplasty (THA) for the patients with developmental dysplasia of the hip (DDH) is one of the challenges due to distinctive bone deformity. Robotic-arm assisted system have been developed to improve the accuracy of implant placement. This study aimed to compare the accuracy of robotic-arm assisted (Robo-THA), CT-based navigated (Navi-THA), and manual (M-THA) cup position and orientation in THA for DDH.

A total of 285 patients (335 hips) including 202 M-THAs, 45 Navi-THAs, and 88 Robo-THA were analyzed. The choice of procedure followed the patient's preferences. Horizontal and vertical center of rotation (HCOR and VCOR) were measured for cup position, and radiographic inclination (RI) and anteversion (RA) were measured for cup orientation. The propensity score-matching was performed among three groups to compare the absolute error from the preoperative target position and angle.

Navi-THA showed significantly smaller absolute errors than M-THA in RI (3.6° and 5.4°) and RA (3.8° and 6.0°), however, there were no significant differences between them in HCOR (2.5 mm and 3.0 mm) or VCOR (2.2 mm and 2.6 mm). In contrast, Robo-THA showed significantly smaller absolute errors of cup position than both M-THA and Navi-THA (HCOR: 1.7 mm and 2.9 mm, vs. M-THA, 1.6 mm and 2.5 mm vs. Navi-THA, VCOR:1.7 mm and 2.4 mm, vs. M-THA, 1.4 mm and 2.2 mm vs. Navi-THA). Robo-THA also showed significantly smaller absolute errors of cup orientation than both M-THA and Navi-THA (RI: 1.4° and 5.7°, vs. M-THA, 1.5° and 3.6°, vs. Navi-THA, RA: 1.9° and 5.8° vs. M-THA, 2.1° and 3.8° vs. Navi-THA).

Robotic-arm assisted system showed more accurate cup position and orientation compared to manual and CT-based navigation in THA for DDH. CT-based navigation increased the accuracy of cup orientation compared to manual procedures, but not cup position.

Aims

Although periacetabular osteotomies are widely used for the treatment of symptomatic dysplastic hips, long-term surgical outcomes and patient-reported outcome measures (PROMs) are still unclear. Accordingly, we assessed hip survival and PROMs at 20 years after transpositional osteotomy of the acetabulum (TOA).

Although periacetabular osteotomies are widely used for the treatment of symptomatic acetabular dysplasia, the surgical outcomes after long term follow-up are still limited. Thus, we assessed hip survival and patient-reported outcomes (PROMs) at 20 years after the transposition osteotomy of acetabulum (TOA).

Among 260 hips in 238 patients treated with TOA, 172 hips in 160 patients were evaluated at average 20.8 years, excluding patients who died or lost to follow-up. Kaplan-Meier analysis was used to assess survivorship with an end-point of THA. PROMs were evaluated using the VAS satisfaction, VAS pain, Oxford hip score (OHS), and Forgotten joint score (FJS). The thresholds of favorable outcomes of FJS and OHS were obtained using the receiver-operating characteristic curve with VAS satisfaction ≥ 50 and VAS pain < 20 as anchors.

Thirty-three hips (19.2%) underwent THA at average 13.3 years after TOA. Kaplan-Meier analysis revealed hip survival rate at 20 years was 79.7%. Multivariate analysis showed the preoperative Tönnis grade significantly influenced hip survival. Survival rates with Tönnis grade 0, grade 1, and grade 2 were 93.3%, 86.7%, and 54.8% at 20 years, respectively. More than 60% of the patients showed favorable PROMs (VAS satisfaction ≥ 50, VAS pain < 20, OHS ≥ 42, FJS ≥ 51). Advanced Tönnis grade at the latest follow-up and higher BMI were significantly associated with unfavorable OHS, but not with other PROMs.

This study demonstrated the durability of TOA for hips with Tönnis grade 0–1 and favorable satisfaction in majority of the patients at 20 years after surgery. Current presence of advanced osteoarthritis is associated with the lower hip function (OHS), but not necessarily associated with subjective pain and satisfaction. Higher BMI also showed a negative impact on postoperative function.

Aims

This study aims to investigate the effects of posterior tibial slope (PTS) on knee kinematics involved in the post-cam mechanism in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA) using computer simulation.

Aims

Appropriate acetabular component placement has been proposed for prevention of postoperative dislocation in total hip arthroplasty (THA). Manual placements often cause outliers in spite of attempts to insert the component within the intended safe zone; therefore, some surgeons routinely evaluate intraoperative pelvic radiographs to exclude excessive acetabular component malposition. However, their evaluation is often ambiguous in case of the tilted or rotated pelvic position. The purpose of this study was to develop the computational analysis to digitalize the acetabular component orientation regardless of the pelvic tilt or rotation.

Regaining the walking ability is one of the main purposes of total knee arthroplasty (TKA). Improving the activities of daily living is a key of patient satisfaction after TKA. However, some patients do not gain enough improvement of ADL as they preoperatively expected, and thus are not satisfied with the surgery. The purpose of this study is to clarify the relationship between preoperative and postoperative physical functional status and whether preoperative scoring can predict the postoperative walking ability. Consecutive 136 patients who underwent total knee arthroplasty for osteoarthritis were prospectively assessed. The average age (±SD) was 74±7.7 and 74% of the patients was female. Berg Balance Scale (BBS) was assessed preoperatively and one year after the surgery. The time needed for 10m walking, muscle power for knee extension and flexion, visual analog scale (VAS) for pain in walking, and necessity of canes in walking were also assessed at one year after the surgery. Multivariate correlation analysis was performed for each parameter. Speaman rank correlation coefficient revealed that preoperative BBS was significantly correlated with the time needed for 10m walking (ρ=0.66, p<0.001). Logistic regression analysis also revealed that preoperative BBS is also correlated with the necessity for canes in walking one year after the surgery. The cut-off value of preoperative BBS for the necessity of canes in walking by ROC curve analysis was 48 points with 79% in sensitivity and 80% in specificity. The muscle powers were also weakly correlated with the walking ability at one year after the surgery, but VAS for pain was not. The study indicated that preoperative physical balance could predict the ability of walking one year after TKA regardless of the reduction of pain. It is suggested that surgery should be recommended before the physical balance function deteriorates to achieve the better walking ability after the TKA

Similar to the radiological findings in rapidly destructive arthrosis of the hip joint (RDA), subchondral insufficiency fracture of the femoral head (SIF) can result in progressive femoral head collapse of unknown etiology. We thus examined the osteoclast activity in hip joint fluid in SIF with progressive collapse in comparison to that in RDA. Twenty-nine hip joint fluid samples were obtained intraoperatively with whole femoral heads from 12 SIF patients and 17 RDA patients. SIF cases were classified into subgroups based on the presence of ≥2mm collapse on preoperative radiographs: SIF with progressive collapse (n=5) and SIF without progressive collapse (n=7). The levels of tartrate-resistant acid phosphatase (TRACP)-5b, interleukin-8, vascular endothelial growth factor (VEGF), and matrix metalloproteinase (MMP)-9 were measured. Numbers of multinuclear giant cells at the subchondral region were assessed histopathologically using mid-coronal slices of each femoral head specimen. Median levels of all markers and median numbers of multinuclear giant cells in SIF with progressive collapse were significantly higher than those in SIF without progressive collapse, while there were no significant differences in SIF with progressive collapse versus RDA. Regression analysis showed that the number of multinuclear giant cells correlated positively with the level of TRACP-5b in joint fluid. This study suggests an association of increased osteoclast activity with the existing condition of progressive collapse in SIF, which was quite similar to the findings in RDA. Therefore, high activation of osteoclast cell may reflect the condition of progressive collapse in SIF as well as RDA.

Osteonecrosis of the femoral head (ONFH) is an ischemic disorder that causes bone and bone marrow necrosis. In spite of many studies, the primary cause of ischemia is still unknown. The purpose of this study is to identify the susceptibility genes in ONFH.

We performed a genome-wide association study (GWAS) in 1,602 ONFH cases and 60,000 controls. Stratified GWASs based on the 3 subgroups of ONFH (corticosteroids, alcohol, idiopathic) were also performed. We then evaluated the candidate gene in silico using public databases.

Two loci in 12q24.11–12 and 20q12 showed significant association with ONFH. A stratified analysis suggested that the 12q24 locus was associated with ONFH through the drinking capacity. In the 20q12 locus, LINC01370 was the only gene, which functions were related to the plausible biological pathway for the development of ONFH.

A novel ONFH locus was identified at chromosome 20q12, and LINC01370 was the best candidate gene in this locus.

Introduction

CT-based navigation system in total hip arthroplasty (THA) is widely used to achieve accurate implant placement. Now, we developed our own CT-based navigation system originally, and since then we have been conducting various analysis in order to use the system more effectively. We compared the accuracy of registration with this navigation system and land mark matching type navigation system. In this study, we evaluated the influence of the surgical approach to the accuracy of registration.

Objectives

Osteophytes are products of active endochondral and intramembranous ossification, and therefore could theoretically provide significant efficacy as bone grafts. In this study, we compared the bone mineralisation effectiveness of osteophytes and cancellous bone, including their effects on secretion of growth factors and anabolic effects on osteoblasts.

Object

CT-based navigation system in total hip arthroplasty(THA) is widely used to achieve accurate implant placement. However, its internal structure was a trade secret. Therefore, it was hard to analyze optimal reference points. Now, we developed our own CT-based navigation system originally, and since then we have been conducting various analyses in order to use the system more effectively. The purpose of this study was to analyze the optimal area and the number of registration points, which enables to move initial errors into the acceptable range.

INTRODUCTION

Golf is considered low-impact sport, but concerns exist about whether golf swing can be performed in safe manner after THA. The purpose of this study was to clarify dynamic hip kinematics during golf swing after THA using image-matching techniques.

Introduction

Total knee arthroplasty (TKA) has achieved excellent clinical outcomes and functional performances. However, there is a need for greater implant longevity and higher flexion by younger and Asian patients. We determined the relationship between mobility and stability of TKA product because they are essential for much further functional upgrading. This research evaluated the geometry characteristics of femorotibial surfaces quantitatively by measuring their force of constraint by computer simulation and mechanical test.

Bone remodeling effects is a significant issue in predicting long term stability of hip arthroplasty. It has been frequently observed around the femoral components especially with the implantation of prosthesis stem. Presence of the stiffer materials into the femur has altering the stress distribution and induces changes in the architecture of the bone. Phenomenon of bone resorption and bone thickening are the common reaction in total hip arthroplasty (THA) which leading to stem loosening and instability. The objectives of this study are (i) to develop inhomogeneous model of lower limbs with hip osteoarthritis and THA and (ii) to predict the bone resorption behavior of lower limbs for both cases.

Biomechanical evaluations of lower limbs are established using the finite element method in predicting bone remodeling process. Lower limbs CT-based data of 79 years old female with hip osteoarthritis (OA) are used in constructing three dimensional inhomogenous models. The FE model of lower limbs was consisted of sacrum, left and right ilium and both femur shaft. Bond between cartilage, acetabulum and femoral head, sacrum and ilium were assumed to be rigidly connected. The inhomogeneous material properties of the bone are determined from the Hounsfield unit of the CT image using commercial biomedical software. A load case of 60kg body weight was considered and fixed at the distal cut of femoral shaft. For THA lower limbs model, the left femur which suffering for hip OA was cut off and implanted with prosthesis stem. THA implant is designed to be Titanium alloy and Alumina for stem and femoral ball, respectively.

Distribution of young modulus of cross-sectional inhomogeneous model is presented in Fig. 2 while model of THA lower limbs also shown in Fig. 2. Higher values of young modulus at the outer part indicate hard or cortical bone. Prediction of bone resorption is discussed with the respect of bone mineral density (BMD). Changes in BMD at initial age to 5 years projection were simulated for hip OA and THA lower limbs models.

The results show different pattern of stress distribution and bone mineral density between hip OA lower limbs and THA lower limbs. Stress is defined to be dominant at prosthesis stem while femur experienced less stress and leading to bone resorption. Projection for 5 years follow up shows that the density around the greater tronchanter appears to decrease significantly.

Background

CT-based navigation system in total hip arthroplasty(THA) is widely used to achieve accurate implant placement. The purpose of this study was to evaluate the influence of initial error correction according to the differences in the shape of the acetabulum, and correction accuracy associated with operation approach after localization of registration points at anterior or posterior area of the acetabulum.

Today's aging society is seeing an increase of patients with rheumatoid arthritis and osteoarthritis, as well as an increase in joint replacement surgery. The artificial joints used in this surgery frequently uses ultra-high molecular weight polyethylene (UHMWPE) as a bearing material. However, UHMWPE wear particles are considered to be a major factor in long-term osteolysis, and implant loosening. Many researchers have reported that the volume and size of particles are critical factors in macrophage activation, with particles in the size range of 0.1 – 1.0 μm being the most biologically active. The micro slurry-jet erosion (MSE) apparatus was introduced to minimize the amount of wear, and increase the size of UHMWPE wear particles by texturing the surfaces of Co-Cr-Mo alloy implants. The MSE apparatus uses a slurry of alumina particles (WA#8000: average diameter 1.2 μm) mixed with water. The slurry and compressed air are mixed within an injection nozzle, which is then applied to the Co-Cr-Mo alloy at high speed to achieve a desired nano-textured surface. In this study, four Co-Cr-Mo alloy surface profiles were prepared. The MSE injection nozzle was fed 40.0 mm in alternating directions across each surface with an orthogonal step of 0.5 mm. The surface M-1 was processed with an injection nozzle feed rate of 1.0 mm/s, and obtained a surface roughness of 5.7 nm. M-2 was processed with a feed rate of 2.0 mm/s, and had a surface roughness of 2.3 nm. The M-4 surface used a 40.0 mm alternating directions surface feed, but with a 1.0 mm orthogonal step, and an injection nozzle feed rate of 0.5 mm/s. It obtained a surface roughness of 4.0 nm. The G-1 surface, with a roughness of 10.0 nm, was processed with the typical lapping method, which is used in conventional artificial joints [Fig. 1]. A pin-on-disk wear tester, capable of multidirectional motion, was used to assess which surface was the most appropriate for artificial joints. The UHMWPE pins were flat ended cylinders, 12.0 mm in diameter, and were placed on the disk with a contact pressure of 6.0 MPa. Tests were carried out in 25% (v/v) fetal calf serum with sodium azide to retard bacterial growth. A sliding speed of 12.1 mm/s, and a total sliding distance of 15.0 km were applied. The wear weight of the MSE textured surface M-1 was significantly lower than the wear weight of the conventional surface. Moreover, the percentages of various wear particle sizes obtained from MSE surface texturing was significantly different from those obtained from the traditional surface.

Effectiveness and long term stability of hip resurfacing and total hip arthroplasty for osteoarthritis patients are still debated nowadays. Several clinical and biomechanical issues have to be considered, including pain relief, return to function, femoral neck fractures, impingement and prosthesis loosening. Normally, patients with hip arthroplasties are facing gait adaptation and at risk of fall. Sudden impact loading and twisting during sideway falls may lead to femoral fractures and joint failures. The purposes of this study are (i) to investigate the stress behavior of hip resurfacing and total hip arthroplasty, and (ii) to predict pattern of femoral fractures during sideway falls and twisting configurations.

Computed tomography (CT) based images of a 54-year old male were used in developing a 3D femoral model. The femur model was designed to be inhomogeneous material as defined by Hounsfield Unit of the CT images. CAD data of hip arthroplasties were imported and aligned to represent RHA and THA femur modelas shown in Fig.1. Prosthesis stem is modeled as Ti-6Al-4V material while femoral ball as Alumina properties. Meanwhile, RHA implant is assigned as Co-Cr-Mo material. Four types of loading and boundary conditions were assigned to demonstrate different falling (FC) and twisting (TC) configurations (see Fig.2). Finite element analysis combined with a damage mechanics model was then performed to predict bone fractures in both arthroplasty models. Different loading magnitudes up to 4BW were applied to extrapolate the fracture patterns.

Prediction of femoral fracture for RHA and THA femurs are discussed in corresponding to maximum principal stress and damage formation criterion. The load bearing strain was set to 3000micron, the physiological bone loading that leads to bone formation. The test strength was wet to 80% of the yield strength determined from the CT images. Different locations of fracture are predicted in each configuration due to different loading direction and boundary conditions as shown in Fig.3. For falling configurations, fractures were projected at trochanteric region for intact and RHA femur, while THA femurs experience fracture at inner proximal region of bone. Differs to twisting configurations, both arthroplasties were predicted to fracture at the distal end of femurs.

Introduction

3D-to-2D model registration technique has been used for evaluating 3D kinematics from 3D surface models of the prostheses or bones and radiographic image sequences. However, no studies have employed these techniques to evaluate in vivo hip kinematics under dynamic weight-bearing conditions. The purposes of this study were to evaluate kinematics of healthy hips and also hips with osteoarthritis (OA) prior to total hip arthroplasty (THA) during four different weight-bearing activities using 3D-to-2D model-to-image registration technique.

This study presents the use of precision surface machining on artificial joint bearing surfaces in order to inhibit macrophage activation. Ultra-high molecular weight polyethylene (UHMWPE) is widely used as a bearing material in polymer-on-hard joint prostheses. However, UHMWPE wear particles are considered to be a major factor in long-term osteolysis and implant loosening. Several studies report that wear particle size is a critical factor in macrophage activation, with particles in the size range of 0.1 – 1.0 μm being the most biological active. The surface for a conventional Co-Cr-Mo alloy joint implant generally has a 10.0 – 20.0 nm roughness. After precision machining, the Co-Cr-Mo alloy surface had a 1.0 – 2.0 nm roughness with scattered concave shapes up to 50 nm in depth. This precision surface machining method used a typical lapping method, but the relationship between the slurry and the machining surface was strictly controlled in order to emphasize the micro-erosion mechanism. A pin-on-disc wear tester capable of multidirectional motion was used to verify that the new surface was the most appropriate for joints. Tests were carried out in 25% (v/v) fetal calf serum with sodium azide to retard bacterial growth. UHMWPE pins, 12.0 mm in diameter with a mean molecular weight of 6.0 million, were placed on the Co-Cr-Mo alloy disc at a contact pressure of 6.0 MPa. A sliding speed of 12.1 mm/s, and a total sliding distance of 15.0 km were applied. The new surface reduced the amount of UHMWPE wear, which would ensure the long-term durability of joints. The new surface also enlarged the size of UHMWPE particles, but did not change their morphological aspect. Primary human peripheral blood mononuclear phagocytes were cultured with the particles. The wear particles generated on the new surface inhibited the production of IL-6, which indicates a reduction of induced tissue reaction and joint loosening.