To prevent the reported side effects of rhBMP-2, an important cytokine with bone forming capacity, the sustained release of rhBMP-2 is highly important. Synthetic copolymer polylactic acid-polyethylene glycol (PLA-PEG) is already shown to be a good carrier for rhBMP-2. The nano-sized hydroxyapatite (nHAp) is mentioned to be superior to conventional hydroxyapatite due to its decreased particle size which increases the surface area, so protein-cell adhesion and mechanical properties concomitantly. In the literature no study is reported with PLA-PEG / rhBMP-2/ nHAp for bone regeneration. In this study, we assessed the controlled release profile of rhBMP-2 from the novel biomaterial of PLA-PEG / rhBMP-2 / nHAp in vitro and evaluated the bone forming capacity of the composite in rat posterolateral spinal fusion (PSF) model in vivo.

Composites were prepared via addition of rhBMP-2 (0µg, 3µg or 10µg) and nHAp (12.5mg) into PLA-PEG (5mg) + acetone solution and shaping. The release kinetics of the cytokine from the composites with 5µg BMP-2 was investigated by ELISA. The effect of nHAp and nHAp with rhBMP-2 on cell differentiation (rat BMSC cells, passage 3) was tested with ALP staining. In vivo bone formation was investigated by PSF on L4-L5 in a total of 36 male SD rats and weekly µCT results and histology at 8^th weeks post operation were used for assessment of the bone formation. All animal experiments was approved by the institutional review board confirming to the laws and regulations of Japan.

The composite showed an initial burst release in the first 24 hours (51.7% of the total released rhBMP-2), but the release was continued for the following 21 days. Thus, the sustained release of rhBMP-2 from the composite was verified. ALP staining results showed nHAp with rhBMP-2 contributed better on differentiation than nHAp itself. µCT and histology demonstrated that spinal fusion was achieved either one or both transverse processes in almost all BMP 3µg and BMP 10µg treated animals. On the contrary, only small or no bone formation was observed in the BMP0µg group (bilateral non-union / unilateral fusion/ bilateral fusion, BMP0µg group; 9/0/0, BMP3µg group; 1/0/11, BMP10µg group; 0/1/11).

We developed a new technology for bone regeneration with BMP-2/PLA-PEG/nHAp composite. With this composite, the required dose of BMP-2 for spinal fusion in rats (10µg) was decreased to 1/3 (3µg) which can be explained by the superior properties of nano-sized hydroxyapatite and by the achievement of sustainable release of rhBMP-2 from the composite.

This study is supported by Japanese Society of the Promotion of Science (JSPS) and Scientific and Technological Research Council of Turkey (TUBITAK). [Project No: 215S834]

Aims

The aim of this study was to explore risk factors for complications associated with dural tear (DT), including the types of DT, and the intra- and postoperative management of DT.

Bi-cruciate stabilized (BCS) TKA is the prosthesis that aims to substitute bi-cruciate ligament with post-cam engagement. We estimated to describe the in vivo kinematics during deep knee bending in BCS and Cruciate retaining (CR) TKA with the same articular geometry. We analyzed 26 knees who agreed to the current investigation under institutional review board approval. 17 knees were implanted with BCS (Journey ∥BCS, Smith & Nephew. Memphis, US) and 9 knees with CR (Journey∥CR). Each patient was asked to perform deep knee bending under weight-bearing condition. To estimate the spatial position and orientation of the TKA, 2D/3D registration technique with single fluoroscopy was used. We evaluated anteroposterior (AP) translation of the nearest point from femoral component to tibial axial plane for medial and lateral sides, femoral external rotation relative to tibial component and post-cam engagement in BCS. Measurement results were analyzed using Wilcoxon test. Values of P<0.05 were considered statistically significant. Medial AP translation indicated 11.7±5.1% posterior movement in BCS and 4.0±6.6% anterior movement in CR from minimum flexion to 130°. Lateral AP translation indicated 28.9±11.4% posterior movement in BCS and 18.3±6.2% posterior movement in CR from minimum flexion to 130°. Femoral external rotation were observed in both group and the amount of rotation were 5.2°±4.5° in BCS and 8.2°±4.0° in CR. Anterior post-cam engagement was not observed in all cases (76.5%). But medial AP translation in BCS was anteriorly in shallow flexion angles compared to CR. It suggested that anterior post-cam engagement couldn't work in valid.

Our aim was to investigate whether it is possible to predict post-operative kinematics (Post-Ope) from intra-operative kinematics (Intra-Ope) after total knee arthroplasty. Our study were performed for 11 patients (14 knees) who underwent primary PS TKA using CT-based navigation system between Sept.2012 and Sept.2014. The mean subject age was 71.5 ± 5.5 years at the time of surgery. Intra-Ope was measured using the navigation system after implantation during passive full extension and flexion imposed by the surgeon. Under fluoroscopic surveillance, each patient was asked to perform sequential deep knee flexion under both non-weight bearing (NWB) and weight bearing (WB) conditions from full extension to maximum flexion. To estimate the spatial position and orientation, we used a 2- to 3- dimensional (2D3D) registration technique. Intra-Ope and Post-Ope had a common coordinate axis for bones. Evaluations were range of motion (ROM), external rotation angles (ER). The level of statistical significant difference was set at 0.05. Mean ROM in Intra-Ope(130°± 7.9°) was statistically larger than both NWB(121.1°±10.5°) and WB(124.0°±14.7°). No Statistically significant difference was found in the mean ER from 10° to 120° among Intra-Ope (11.2°± 8.5°) and NWB(7.1°±6.0°) and WB(5.3°±3.2°). It is suggested that we could predict Post-Ope from Intra-Ope by considering the increase of the range of motion due to the muscle relaxation condition and the amount of change in the ER.

Purpose

This study was to investigate the effect of posterior tibial slope (PTS) on the kinematics in the cruciate-retaining total knee arthroplasty (CR-TKA) using 2- to 3- dimensional registration technique.

Aims

In Asia and the Middle-East, people often flex their knees deeply in order to perform activities of daily living. The purpose of this study was to investigate the 3D kinematics of normal knees during high-flexion activities. Our hypothesis was that the femorotibial rotation, varus-valgus angle, translations, and kinematic pathway of normal knees during high-flexion activities, varied according to activity.

The purpose of this experimental study was to elucidate the accuracy of neck-cut PSG setting, and femoral component implantation using neck-cut PSG in the THA through the anterolateral-approach relative to the preoperative planning goals, and to determine the usefulness of PSG compared with the procedure without PSG. A total of 32 hips from 16 fresh Caucasian cadaveric samples were used and classified into 4 groups: cementless anatomical stem implantation with wide-base-contact PSG (AWP: 8 hips, Fig.2); (2) cementless anatomical stem implantation with narrow-base-contact PSG (ANP: 8 hips, Fig.2); (3) cementless anatomical stem implantation without PSG (Control: 8 hips); and (4) cementless taper-wedge stem implantation with wide-base-contact PSG (TWP: 8 hips). The absolute error of PSG setting in the sagittal plane of the AWP group was significantly less than that of the ANP (p=0.003).THA with wide-base- contact PSG resulted in better alignment of the femoral component than THA without PSG or with narrow- base-contact PSG. Although the neck-cut PSG did not control the sagittal alignment of taper-wedge stem, the neck-cut PSG was effective to realise the preoperative coronal alignment and medial height for THA via the anterolateral approach regardless of the femoral component type.

For figures and tables, please contact authors directly.

INTRODUCTION

The purpose of this study is to elucidate longitudinal kinematic changes of the hip joint during heels-down squatting after THA.

Purpose

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. However, most conventional methods have needed time-consuming and labor-intensive manual operations in some process. In particular, for the 3D pose estimation of tibial component model from X-ray images, these manual operations were carefully performed because the pose estimation of symmetrical tibial component get severe local minima rather than that of unsymmetrical femoral component. In this study, therefore, we propose an automated 3D kinematic estimation method of tibial component based on statistical motion model, which is created from previous analyzed 3D kinematic data of TKA.

We hypothesized that using the navigation system, intra-operative knee kinematics after implantation measured may predict that post-operative kinematic in activities of daily living. Our aim was to compare intra-operative knee kinematics by a computed tomography (CT)-based navigation system and post-operative by the 2- to 3-dimensional registration techniques (2D3D).

This study were performed for 8 patients (10 knees, medial osteoarthritis) who underwent primary PS TKA using CT-based navigation system. The median follow-up period from operation date to fluoroscopic surveillance date was 13 months (range 5 – 37 months). Navigation and 2D3D had a common coordinate origin for components. Medial and lateral femoral condyle anterior-posterior translation (MFT and LFT) were respectively defined as the distance of the projection of the points (which was set on the top of the posterior femoral pegs) onto the axial plane of the tibial coordinate system. Intraoperative kinematics was measured using the navigation system after final implantation and closure of the retinaculum during passive full flexion and extension imposed by the surgeon. Under fluoroscopic surveillance in the sagittal plane, each patient was asked to perform sequential deep knee flexion under both weight bearing (WB) and non-weight bearing (NWB) conditions from full extension to maximum flexion. Repeated two-way ANOVA (tasks × flexion angles) were used, and then post-hoc test (paired t-tests with Boferroni correction) were performed. The level of statistical significant difference was set at 0.05 on two-way ANOVAs and 0.05 / 3 on post-hoc paired t-tests.

Mean range of motion between femoral and tibial components were Intra-operative (Intra): 28.0 ± 9.7, NWB conditions: 120.6 ± 11.1, WB conditions: 125.1 ± 12.9°, respectively. Mean ER (+) / IR (−) from 0° to 120° were Intra-operative (Intra): 9.3 ± 10.2°, NWB conditions: 8.1 ± 8.9, WB conditions: 5.2 ± 7.0, respectively. Mean MFT /LFT from 0° to 90° were Intra; 4.4 ±14.8/ 4.2± 8.5mm, NWB; 6.2 ± 6.9 / 9.2 ± 3.1 mm, WB; 9.2 ± 3.5 / 7.4 ± 2.8 mm, respectively. Mean MFT /LFT from 90° to 120° were Intra; −4.4 ± 2.5 / −5.7 ± 2.9 mm, NWB; −5.5 ± 1.8 / −8.2 ± 0.6 mm, WB; −4.0 ± 1.9 / −5.4 ± 2.3mm, respectively. Mean ADD/ABD from 0° to 120° were Intra;-4.2 ± 3.0, NWB; −0.2 ± 2.1, WB; −0.1 ± 0.8, respectively. Repeated two-way ANOVA showed a significant all interaction on kinematic variables (p<0.05). No statistically significant difference at post-hoc test was found in ER/ IR of all tasks and MFT /LFT of Intra vs NWB and Intra vs WB from 0° to 120° (p>0.05 / 3).

The Conditions of these tasks were different from each others. Our study demonstrated that intra-operative kinematics could predict post-operative kinematics.

The purpose of this study is to investigate the three-dimensional (3D) kinematics of normal knees in deep knee-bending motions like squatting and kneeling.

Material & Methods: We investigated the in vivo kinematics of 4 Japanese healthy male volunteers (8 normal knees in squatting, 7 normal knees in kneeling). Each sequential motion was performed under fluoroscopic surveillance in the sagittal plane. Femorotibial motion was analyzed using 2D/3D registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femur and tibia from single-view fluoroscopic images. We evaluated the femoral rotation relative to the tibia and anteroposterior (AP) translation of the femoral sulcus and lateral epicondyle on the plane perpendicular to the tibial mechanical axis. Student's t test was used to analyze differences in the absolute value of axial rotation and AP translation of the femoral sulcus and lateral epicondyle during squatting and kneeling. Values of P < 0.05 were considered statistically significant.

During squatting, knees were gradually flexed from −2.8 ± 1.3° to 145.5 ± 5.1° on average. Knees were gradually flexed from 100.8 ± 3.9° to 155.6 ± 3.2° on average during kneeling. Femurs during squatting displayed sharp external rotation relative to the tibia from 0° to 30° of flexion and it reached 12.5 ± 3.3° on average. From 30° to 130° of flexion, the femoral external rotation showed gradually, and it reached 19.1 ± 7.3° on average. From 130° to 140° of flexion, it was observed additionally, and reached 22.4 ± 6.1° on average. All kneeling knees displayed femoral external rotation relative to the tibia sharply from 100° to 150° of flexion, and it reached 20.7 ± 7.5° on average. From 100° to 120° of flexion, the femoral external rotation during squatting was larger than that during kneeling significantly. From 120° to 140° of flexion, there was no significant difference between squatting and kneeling. The sulcus during squatting moved 4.1 ± 4.8 mm anterior from 0° to 60° of flexion. From 60° of flexion it moved 13.6 ± 13.4 mm posterior. The sulcus during kneeling was not indicated significant movement with the knee flexion. The lateral epicondyle during squatting moved 39.4 ± 7.7 mm posterior from 0° to 140° of flexion. The lateral epicondyle during kneeling moved 22.0 ± 5.4 mm posterior movement from 100° to 150° of flexion. In AP translation of the sulcus from 100° to 140° of flexion, there was no significant difference between squatting and kneeling. However in that of the lateral epicondyle, squatting groups moved posterior significantly.

Even if they were same deep knee-bending, the kinematics were different because of the differences of daily motions. The results in this study demonstrated that in vivo kinematics of deep knee-bending were different between squatting and kneeling.

Aims

To clarify the asymmetrical ossification of the epiphyseal ring between the convex and concave sides in patients with adolescent idiopathic scoliosis (AIS).

Introduction

Inappropriate soft tissue tension around an artificial hip is regarded as one cause of dislocation or abductor muscle weakness. It has been considered that restoration of leg offset is important to optimise soft tissue tension in THA, while it is unclear what factors determine soft tissue tension around artificial hip joints. The purpose of the present study was to assess how postoperative leg offset influence the soft tissue tension around artificial hip joints.

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.

Patella resection has been the least controlled element of total knee arthroplasty (TKA). We have developed an intraoperative guide system involving a custom-made surgical template designed on the basis of a three-dimensional computer simulation incorporating computed tomography (CT) data for several years. This time we have applied this intraoperative guide system for the patella resection in TKA. We investigated the accuracy of CT-based patient-specific templating (PST) for patella resection using cadaveric knee joints in vitro.

To plan the corrective patella resection, we attempted to simulate a three-dimensional patella resection with the use of computer models of the patella. From CT images of the patella we obtained three-dimensional surface models of the patella by performing a three-dimensional surface generation of the bone cortex. After the patella resection using CT-based custom-made surgical templating instrumentation, CT scan was performed again and we compared the patella shape in three-dimensional patella bone model reconstructed from pre and after cut from CT data. We compared the accuracy of patella cut using three-dimensional patella bone model reconstructed from pre and after cut from CT data. Statistical analysis was performed using paired t test.

The difference between patella cut with CT-based custom-made surgical templating instrumentation and pre-operative planning were 0.8±1.2mm (medial side) and 0.1±1.4mm (lateral side). More than 60% resulted within 2mm from the pre-operative planning. There were significant differences both in flexion/extension, external/internal rotation and bone cut depth between CT-based custom-made surgical templating instrumentation and conventional instrument.

The results in this study demonstrated the usefulness of CT-based custom-made surgical templating instrumentation for patella resection in TKA.

Objective

Excessive mechanical stress on synovial joints causes osteoarthritis (OA) and results in the production of prostaglandin E2 (PGE2), a key molecule in arthritis, by synovial fibroblasts. However, the relationship between arthritis-related molecules and mechanical stress is still unclear. The purpose of this study was to examine the synovial fibroblast response to cyclic mechanical stress using an in vitro osteoarthritis model.

Summary

The effect of the geometry of the tibial polyethylene insert was investigated in vivo loaded conditions.

We retrospectively assessed the value of identifying impinging osteophytes using dynamic computer simulation of CT scans of the elbow in assisting their arthroscopic removal in patients with osteoarthritis of the elbow. A total of 20 patients were treated (19 men and one woman, mean age 38 years (19 to 55)) and followed for a mean of 25 months (24 to 29). We located the impinging osteophytes dynamically using computerised three-dimensional models of the elbow based on CT data in three positions of flexion of the elbow. These were then removed arthroscopically and a capsular release was performed.

The mean loss of extension improved from 23° (10° to 45°) pre-operatively to 9° (0° to 25°) post-operatively, and the mean flexion improved from 121° (80° to 140°) pre-operatively to 130° (110° to 145°) post-operatively. The mean Mayo Elbow Performance Score improved from 62 (30 to 85) to 95 (70 to 100) post-operatively. All patients had pain in the elbow pre-operatively which disappeared or decreased post-operatively. According to their Mayo scores, 14 patients had an excellent clinical outcome and six a good outcome; 15 were very satisfied and five were satisfied with their post-operative outcome.

We recommend this technique in the surgical management of patients with osteoarthritis of the elbow.

Cite this article: Bone Joint J 2014;96-B:237–41.

Purpose:

To materialize 3D kinematic analysis of total knee arthroplasty (TKA), 2D/3D registration techniques, which use X-ray fluoroscopic images and the knee implants CAD, have been applied to clinical cases. However, most conventional methods have needed time-consuming and labor-intensive manual operations in some process. In previous study, we addressed a manual operations problem when setting initial pose of implants model for 2D/3D registration, and reported a semi-automated initial pose estimation method based on an interpolation technique. However, this method still required appropriate initial pose estimation of the model with manual operations for some X-ray images (key frames). Additionally, in the situation like fast knee motion and use of low frame rate, good registration results were not obtained because of the large displacement between each frame silhouette. To overcome these problems, this study proposes an improved semi-automated 3D kinematic estimation method.

We investigated differences in the location and mode of labral tears between dysplastic hips and hips with femoroacetabular impingement (FAI). We also investigated the relationship between labral tear and adjacent cartilage damage. We retrospectively studied 72 symptomatic hips (in 68 patients: 19 men and 49 women) with radiological evidence of dysplasia or FAI on high-resolution CT arthrography. The incidence and location of labral tears and modes of tear associated with the base of the labrum (Mode 1) or body of the labrum (Mode 2) were compared among FAI, mildly dysplastic and severely dysplastic hips. The locations predominantly involved with labral tears were different in FAI and mild dysplastic hips (anterior and anterosuperior zones) and in severely dysplastic hips (anterosuperior and superior zones) around the acetabulum. Significant differences were observed in the prevalence of Mode 1 versus Mode 2 tears in FAI hips (72% (n = 13) vs 28% (n = 5)) and severe dysplastic hips (25% (n = 2) vs 75% (n = 6)). The frequency of cartilage damage adjacent to Mode 1 tears was significantly higher (42% (n = 14)) than that adjacent to Mode 2 tears (14% (n = 3)).

Hip pathology is significantly related to the locations and modes of labral tears. Mode 1 tears may be a risk factor for the development of adjacent acetabular cartilage damage.

Cite this article: Bone Joint J 2013;95-B:1320–5.

Purpose

For 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. These techniques are highly valuable for dynamic 3D kinematic analysis, but have needed time-consuming and labor-intensive manual operations in some process. In previous study, we reported a robust method to reduce manual operations to remove spurious edges and noises in edge detection process of X-ray images. In this study, we address another manual operations problem occurred when setting initial pose of TKA implants model for 2D/3D registration. To set appropriate initial pose of the model with manual operations for each X-ray image is important to obtain the good registration results. However, the number of X-ray images for a knee performance is very large, and thus to set initial pose with manual operations is very time-consuming and a problem for practical clinical applications. Therefore, this study proposes an initial pose estimation method for automated 3D kinematic analysis of TKA.

Background

Various postoperative evaluations using fluoroscopy have reported in vivo knee flexion kinematics under weight bearing conditions. This method has been used to investigate which design features are more important for restoring normal knee function. The objective of this study is to evaluate the kinematics of a Low Contact Stress total knee arthroplasty (LCS TKA) in weight bearing deep knee flexion using 2D/3D registration technique.

The in vivo kinematics of squatting after total hip arthroplasty (THA) has remained unclear. The purpose of the present study was to elucidate range of motion (ROM) of the hip joint and the incidence of prosthetic impingement during heels-down squatting after THA.

23 primary cementless THAs using a computed tomography-based navigation system (CT-HIP, Stryker Navigation, Freiberg, Germany) were investigated using fluoroscopy. An acetabular component with concavities around the rim (TriAD HA PSL, Stryker Orthopaedics, Mahwah, NJ) and a femoral component with reduced neck geometry (CentPiller, Stryker Orthopaedics), which provided a large oscillation angle, were used. The femoral head size was 28mm (8 hips), 32mm (10 hips), and 36mm (5 hips). Post-operative analysis was performed within 6 months in 6 hips, and at 6 months to 2 years in 17 hips. Successive hip motion during heels-down squatting was recorded as serial digital radiographic images in a DICOM format using a flat panel detector. The coordinate system of the acetabular and femoral components based on the neutral standing position was defined. The images of the hip joint were matched to three-dimensional computer aided design models of the acetabular and femoral components using a two-dimensional to three-dimensional (2D/3D) registration technique. In the previous computer simulation study of THA, the root mean square errors of rotation was less than 1.3°, and that of translation was less than 2.3 mm.

We estimated changes in the relative angle of the femoral component to the acetabular component, which represented the hip ROM, and investigated the incidence of prosthetic impingement during squatting. We also estimated changes in the flexion angle of the acetabular component, which represented the pelvic posterior tilting angle (PA), and the flexion angle of the femoral component, which represented the femoral flexion angle (FA). The contribution of the PA to the FA at maximum squatting was evaluated as the pelvic posterior tilting ratio (PA/FA). In addition, when both components were positioned most closely during squatting, we estimated the minimum angle (MA) up to theoretical prosthetic impingement.

No prosthetic impingement occurred in any hips. The maximum hip flexion ROM was mean 92.7° (SD; 15.7°, range; 55.1°–119.1°) and was not always consisted with the maximum squatting. The maximum pelvic posterior tilting angle (PA) was mean 27.3° (SD; 11.0°, range; 5.5°–46.5°). The pelvis began to tilt posteriorly at 50°–70° of the hip flexion ROM. The maximum femoral flexion angle (FA) was mean 118.9° (SD; 10.4°, range; 86.4°–136.7°). At the maximum squatting, the ratio of the pelvic posterior tilting angle to the femoral flexion angle (pelvic posterior tilting ratio, PA/FA) was mean 22.9% (SD; 10.4%, range; 3.8%–45.7%). The minimum angle up to the theoretical prosthetic impingement was mean 22.7° (SD; 7.5°, range; 10.0°–37.9°). The maximum hip flexion of ROM in 36 mm head cases was larger than that in 32 mm or 28 mm head cases, while the minimum angle up to the prosthetic impingement in 36 mm head cases was also larger than that in 32 mm or 28 mm head cases.

Three-dimensional assessment of dynamic squatting motion after THA using the 2D/3D registration technique enabled us to elucidate hip ROM, and to assess the prosthetic impingement, the contribution of the pelvic posterior tilting, and the minimum angle up to theoretical prosthetic impingement during squatting.

Purpose

There are concerns of soft-tissue reactions such as metal hypersensitivity or pseudotumors for metal-on-metal (MoM) bearings in hip arthroplasty, however, such reactions around ceramic or polyethylene bearings are incompletely understood. The present study was conducted to examine the capabilities of ultrasound screening and to compare the prevalence of periarticular soft-tissue lesions among various types of bearings.

Purpose

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.

Purpose

Ceramic-on-ceramic bearings in total hip arthroplasty (CoC THA) have theoretical advantages of wear resistance and favorable biocompatibility of ceramic particles to the surrounding bony and soft tissue. Long-time durability of CoC THA has been expected, however, clinical results over 10 years after operation were scarcely reported. In the present study, clinical results at follow of 10 years were examined for CoC THAs with a changeable femoral neck which allowed correction of anteversion of the femoral component in cases with abnormal femoral anteversion in dysplastic hips.

Introduction

Lesion location and volume are critical factors to select patients with osteonecrosis for whom resurfacing arthroplasty is appropriate. However, no reliable surgical planning system which can assess relationship between necrotic lesions and the femoral component has been established. We have developed a 3D-MRI-based planning system for resurfacing arthroplasty. The purpose of the present study was to evaluate its feasibility.

Introduction

In osteonecrosis of the femoral head (ONFH), progression of collapse is influenced by a repair reaction, especially bone resorptive activity, around the necrotic bone. Alendronate is a potent inhibitor of bone resorption by inhibiting osteoclast activity. We performed a clinical study to test if systemic alendronate treatment would prevent the development of collapse in patients with ONFH.

Introduction

Femoral neck fracture (FNF) is a common trauma in the elderly individuals. When the blood supply to the femoral head is impaired with a fracture event, the reduction or disruption of blood supply to the bone, hypoxia, leads to death of the bone marrow and trabecular bone, and eventual late segmental collapse. In the reparative process, osteoblasts and osteoclasts perform the important function of repairing the fracture site at the femoral neck. However, the reparative reaction including angiogenesis and osteogenesis remains unknown. In order to investigate the reparative reaction in patients with FNF, the distribution of tartrate resistant acid phosphatase (TRAP)-positive cells and expression of HIF-1 alpha, VEGF, and FGF-2 were observed in 36 hips in 35 patients.

Using a larger diameter femoral head in total hip arthroplasty (THA) has advantages in terms of the increased joint stability and range of motion. And the wear resistance of highly cross-linked polyethylene (HXLPE) even combined with a larger head has already been demonstrated by in vitro studies. The purpose of this study was to compare the in vivo wear of Longevity HXLPE sockets against 32 mm and 26 mm heads at a 5-year follow-up.

From November 2000 to November 2001, 51 primary cementless THAs were performed with a 26 mm cobalt-chromium head and a Longevity HXLPE socket (Zimmer). A cohort of 32 mm cobalt-chromium heads was comprised of 51 THAs with the same prosthesis performed from December 2001 to December 2003. No significant differences between the groups were observed in gender, age, and BMI, however, polyethylene liners with 32 mm heads were significantly thinner than those with 26 mm heads. Two-dimensional linear wear was measured using PolyWare software on annual x-rays, and total head penetration rates at postoperative 5-year and steady state wear rates were calculated. In addition, periprosthetic osteolysis was evaluated.

At the 5-year follow-up, the total head penetration rates were 0.047±0.022 mm/year with 26 mm heads and 0.048±0.026 mm/year with 32 mm heads. The steady state wear rates were −0.008 mm/year with 26 mm heads and 0.001 mm/year with 32 mm heads. No significant differences were seen between the two groups (p=0.82 and p=0.24). Osteolysis was not observed around pros-theses in any hips.

At the 5-year follow-up, the wear rate of Longevity HXLPE was very low. A Longevity HXLPE socket will undergo the same level of wear whether with a 32 mm head or a 26 mm head.

Mobile-bearing (MB) total knee prostheses have been developed to achieve lower contact stress and higher conformity than fixed-bearing total knee prostheses. However, little is known about the in vivo kinematics of MB prostheses especially about the motion of polyethylene insert (PE). And the in vivo motion of PE during squat motion has not been clarified. The objective of this study is to clarify the in vivo motion of MB total knee arthroplasty including PE during squat motion. Patients and methods: We investigated the in vivo knee kinematics of 11 knees (10 patients) implanted with PFC-Sigma RPF (DePuy). Under fluoroscopic surveillance, each patient did a wight-bearing deep knee bending motion. And motion between each component was analyzed using two-to three-dimensional registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femoral, tibial components, and PE (implanted with four tantalum beads intra-operatively) from single-view fluoroscopic images. We evaluated the range of motion between the femoral and tibial components, axial rotation between the femoral component and PE, the femoral and tibial component, and the PE and tibial component, and AP translation of the nearest point between the femoral and tibial component and between the femoral component and PE.

Results: The mean range of hyper-extension was 2.1° and the mean range of flexion of 121.2°. The femoral component relative to the tibial component demonstrated 10.4° external rotation for 0–120 degrees flexion. The tibial component rotated 10.2° externally relative to the PE and the femoral component minimally rotated relative to the PE within ± 5 degrees. In upright standing position, the femoral component already rotated externally relative to the tibial component in 6.3°, and the PE also rotated on average 6.4° externally on the tibial tray. Typically the femoral component relative to the tibial component exhibited a central pivot pattern external rotation from extension to 80° knee flexion. Subsequently from 80 to 120°, bilateral condyles moved backward. In a similar fashion, the femoral component relative to the PE exhibited a central pivot pattern external rotation from extension to 70° knee flexion and subsequently bicondylar rollback from 70 to 120° knee flexion.

Discussion and Conclusion: In this study, we evaluated the in vivo motion of PE during squat motion. About this total knee prosthesis, the mobile-bearing mechanism which advantages over fixed-bearing prosthesis to reduce contact stress and keep high comformity might work well, and arc of range of motion was maintained. Furthermore, in upright standing position, the femoral component and tibial component already rotated externally relative to the PE in almost equal measure. This indicated that, self-aligning mechanism, another characteristic of the MB prosthesis might also work well.

Recently mobile-bearing total knee arthroplasty (TKA) has become more popular. However, the advantages of mobile bearing (MB) PS TKA still remain unclear especially from a kinematic point of view. The objective of this study was to investigate the difference and advantage in kinematics of mobile baring PS TKA compared with fixed bearing (FB) PS TKA.

Femorotibial nearest positions for 19 subjects (20 knees), 10 knees implanted with NexGen Legacy flex (Zimmer, Warsaw, IN)with mobile bearing PS TKA, and 10 knees implanted with NexGen Legacy flex (Zimmer, Warsaw, IN)with fixed bearing PS TKA were analyzed using the sagittal plane fluoroscopic images. All the knees were implanted by a single surgeon. All the subjects performed weight bearing deep knee bending motion. We evaluated range of motion, axial rotation of the femoral component, AP translation of medial and lateral sides.

The average range of motion between femoral component and tibial component was 119°±18° in MB and 122°±10 ° in FB. The axial rotation of the femoral component was 11.8°±6.2° in MB and 11.8°±4.9° in FB. There was no significant difference both in range of motion and axial rotation between MB and FB. The AP translation of MB and FB showed same patterns. They were rollback in early flexion, the lateral pivot pattern (the medial condyle moved forward significantly compared with the lesser amount of AP translation for the lateral condyle) at mid flexion, and bicondylar rollback at deep flexion. The rollback in early flexion was 3.4mm in MB and 1.8mm in FB at medial side, 4.2mm in MB and 4.8mm in FB at lateral side. There was no significant difference. The lateral pivot pattern, which moved anteriorly, was 7.8mm in MB and 7.0mm in FB at medial side, 3.0mm in MB and 2.4mm in FB at lateral side. There was no significant difference. The bicondylar rollback at deep flexion was 6.4mm in MB and 7.7mm in FB at medial side, 6.9mm in MB and 4.8mm in FB at lateral side. In four subjects, more than 12°axial rotation was observed in knees implanted with FB TKA which allows only 12°axial rotation.

The results in this study demonstrate that there was no significant difference in kinematics of weight bearing deep knee bending motion between MB and FB. The advantage of MB is allowance of axial rotation which restricted until 12° in FB NexGen Legacy flex PS TKA.

Introduction: Recently several retrieval reports of PS TKA have demonstrated that the wear and deformation can occur on the anterior tibial post and the hyperextension of femorotibial components was a pivotal factor in the mechanism of anterior tibial post impingement. The objective of this study was to investigate the in vivo mechanism of anterior tibial post impingement during gait in PS TKAs.

Methods: Twenty knees with PS TKAs implanted by single surgeon were assessed in this study. The Review Board Committee of the author’s institution approved this study and informed consent was obtained from all patients. In this study ten knees implanted with Scorpio NRG PS (Stryker Orthopedics, Mahwah, NJ) and ten knees implanted with NexGen Legacy-flex fixed (Zimmer, Warsaw, IN) were examined. Each patient was asked to perform treadmill gait under fluoroscopic surveillance in the sagittal plane. Treadmill gait speed was 0.5–1.0 m/s at Patients selected comfortable speed. Patients were explicitly encouraged to fully extend their knees at heel-strike and to avoid a shuffling gait pattern. Patients used light-touch hand-support to maintain the foot position on the treadmill. In vivo 3D poses of the knee prostheses were computed using a two- to three-dimensional (2D/3D) registration technique, which uses CAD models to reproduce spatial postures of the femoral and tibial components from calibrated single-view fluoroscopic images. We evaluated range of motion and the anterior-posterior (AP) translations between femoral and tibial inserts. The anterior tibial post impingement was determined when the proximity between tibial post and femoral cam is within the 0.5mm threshold.

Results: The maximum flexion during gait was 41.9° (25°–56°) in NRG and 42.3° (23°–59°) in Legacy-flex. The minimum flexion during gait was 1.5° (−9.2° − 8.4°) in NRG and 1.8° (−13.0° − 17.0°) in Legacy-flex. The AP translations of the medial and lateral contact points in stance phase were significantly larger in Legacy-flex compared with NRG (medial ; p=0.02,lateral ; p=0.007, Mann-Whitney’s U test). Anterior tibial post impingement was recognized in four knees implanted with Legacy-flex, and in two of three knees, the knee was not hyper extended. On the other hand, no impingement was recognized in knee implanted with NRG.

Discussion: In this study, the anterior tibial post impingement occurred not only in hyper extended knee but also in slightly flexed knee in Legacy-flex. One of the reasons why the anterior tibial post impingement was recognized in Legacy-flex was the large amount of the AP translation in stance phase. Posterior translation in stance phase may be one pivotal factor in the mechanism of the anterior tibial post impingement.

Ceramic heads and highly cross-linked polyethylene (HXLPE) as bearing surface materials have been introduced to reduce the production of polyethylene wear particles. The present study hypothesized that the wear rate of HXLPE could be further reduced when combined with a ceramic head. The purpose of this study was to compare the in vivo wear of Longevity HXLPE against cobalt-chromium and zirconia heads after a minimum 5-year follow-up.

A prospective cohort study was performed in 102 cementless total hip arthroplasties (THAs) with the Longevity HXLPE socket (Zimmer) between June 2000 and October 2001. Same prostheses were used in all cases both acetabular cups (Trilogy; Zimmer) and femoral stems (Versys Fiber Metal Taper; Zimmer). 26-mm zirconia heads (NGK) or 26-mm cobalt-chromium heads (Zimmer) were randomly used in 51 hips each. A minimum 5-year follow-up was completed for 47 hips with zirconia heads and 46 hips with cobalt-chromium heads. Two-dimensional linear wear of Longevity HXLPE was measured using computer-assisted methods (PolyWare) on annual x-rays, and total head penetration rates and steady state wear rates were calculated. In addition, periprosthetic osteolysis was evaluated.

At a mean 6-year follow-up, the total head penetration rates were 0.034±0.016 mm/year (zirconia) and 0.031±0.015 mm/year (cobalt-chromium). The steady state wear rates were −0.01 mm/year (zirconia) and −0.01 mm/year (cobalt-chromium). No significant difference was seen between the two groups (p=0.4 and p=0.91). Osteolysis was not observed around prostheses in any hips.

In conclusion, no advantage was seen for the zirconia head compared with the cobalt-chromium head in this time period.

Background: Mobile-bearing (MB) total knee prostheses have been developed to achieve lower contact stress and higher conformity than fixed-bearing total knee prostheses. However, little is known about the in vivo kinematics of MB prostheses especially about the motion of polyethylene insert (PE). And the in vivo motion of PE during deep knee bending under weight-bearing conditions has not been clarified. The objective of this study is to clarify the in vivo motion of MB total knee arthroplasty including PE during weight-bearing deep knee bend motion.

Patients and methods: We investigated the in vivo knee kinematics of 9 knees (9 patients) implanted with PFC-Sigma RPF (DePuy). Under fluoroscopic surveillance, each patient did a wight-bearing deep knee bending motion. And motion between each component was analyzed using two- to three-dimensional registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femoral, tibial components, and PE (implanted with four tantalum beads intra-operatively) from single-view fluoroscopic images. We evaluated the range of motion between the femoral and tibial components, axial rotation between the femoral component and PE, the femoral and tibial component, and the PE and tibial component, and AP translation of the nearest point between the femoral and tibial component and between the femoral component and PE.

Results: The mean range of hyper-extension was 2.1° and the mean range of flexion of 121.2°. The femoral component relative to the tibial component demonstrated 13.0° external rotation for 0–120 degrees flexion. The tibial component rotated 12.1° externally relative to the PE and the femoral component minimally rotated relative to the PE within ± 5 degrees. In upright standing position, the femoral component already rotated externally relative to the tibial component in 7.8°, and the PE also rotated on average 8.2° externally on the tibial tray. Typically the femoral component relative to the tibial component exhibited a central pivot pattern external rotation from extension to 80° knee flexion. Subsequently from 80 to 120°, bilateral condyles moved backward. In a similar fashion, the femoral component relative to the PE exhibited a central pivot pattern external rotation from extension to 70° knee flexion and subsequently bicondylar rollback from 70 to 120° knee flexion.

Discussion and conclusion: In this study, we evaluated the in vivo motion of PE during deep knee bend motion under weight-bearing condition. About this total knee prosthesis, the mobile-bearing mechanism which advantages over fixed-bearing prosthesis to reduce contact stress and keep high comformity might work well, and arc of range of motion was maintained. Furthermore, in upright standing position, the femoral component and tibial component already rotated externally relative to the PE in almost equal measure. This indicated that, self-aligning mechanism, another characteristic of the MB prosthesis might also work well.

Introduction: In order to investigate the reparative reaction process in patients with osteonecrosis of the femoral head (ONFH), we performed tartrate resistant acid phosphatase (TRAP) staining for the femoral head retrieved from the patients at the surgery.

Methods: This study included 21 hips in 19 patients. There were 15 women and 4 men who had a mean age of 42 years (range, 22 to 79 years). Associated risk factors included corticosteroids (n=15), alcohol (n=4), and idiopathic (n=1). Radiologic staging according to the Japanese Orthopaedic Classification included one stage 1, six stage 3A (collapse < 3mm), five stage3B (collapse> 3mm), and nine stage 4 (osteoarthritic change). After femoral head samples were fixed in formalin, 15 samples were decalcified by EDTA, while 6 were not decalcified. All samples were stained by Haematoxylin and Eosin and TRAP.

Results: TRAP positive multinucleated cells were existed at not only necrotic trabecular bone but also new appositional trabecular bone. TRAP positive cells were mainly located at the reactive interface (revascularized) zone while they did not exist in the necrotic zone. They were sometimes located at the normal bone marrow area near the retinacula or teres. While subchondral fractures were detected in two stage 3A hips, five stage 3B hips, and three stage 4 hips, TRAP positive cells around the subchondral fracture were detected in only two stage 3B hips and three stage 4 hips. In one stage 1 hip, TRAP positive mononuclear cells were detected around the enlarged adipocytes at the reactive interface zone. In six stage 3A hips, TRAP positive cells were detected at the reactive interface zone just around the subchondral area. In five stage 3B hips, they were detected along the reactive interface zone in the femoral head. In nine stage 4 hips, they were detected through the subchondral area and along the reactive interface zone.

Discussion: The expression mode of TRAP positive cells changes according to the radiologic stages in ONFH, represents the reparative reaction process.

We evaluated 30 patients with cervical myelopathy before and after decompressive surgery and compared them with 42 healthy controls. All were asked to grip and release their fingers as rapidly as possible for 15 seconds. Films recorded with a digital camera were divided into three files of five seconds each. Three doctors independently counted the number of grip and release cycles in a blinded manner (N1 represents the number of cycles for the first five-second segment, N2 for the second and N3 for the third). N2 and N3 of the pre-operative group were significantly fewer than those of the control group, and the postoperative group’s results were significantly greater than those of the pre-operative group. In the control group, the numbers decreased significantly with each succeeding five-second interval (fatigue phenomenon). In the pre-operative myelopathy group there was no significant difference between N1 and N2 (freezing phenomenon).

The 15-second test is shown to be reliable in the quantitative evaluation of cervical myelopathy. Although it requires a camera and animation files, it can detect small changes in neurological status because of its precise and objective nature.

While numerous studies have examined dislocation caused by basic everyday movements, no objective studies have investigated body positions to minimize risk of dislocation during intercourse. We therefore used a four-dimensional motion analysis system to assess sexual activities in patients who had undergone total hip arthroplasty (THA), to identify body positions displaying less risk of dislocation.

Five body-surface infrared sensors were placed on five healthy female volunteers, and maximum hip joint angle was measured. Subjects were asked to take the following three body positions: supine (missionary); top (woman on top); and kneeling (doggy-style). Angle data obtained using body surface markers were combined with three-dimensional skeletal models extracted using CT images obtained from the 24 joints of 16 patients who had undergone THA, to ascertain angles at which collision with the artificial joint or skeleton would occur.

Collision angle for: supine position at maximum abduction in flexion was 77±16° in flexion and 82±57° in medial rotation; top position at maximum extension was 36±16° in flexion and 68±53° in medial rotation; top position at maximum flexion was 12±9° in flexion and 14±11° in medial rotation; kneeling position at maximum extension was 115±1° in flexion and 127±44° in medial rotation; and kneeling position at maximum flex-ion was 14±8° in flexion and 17±11° in medial rotation.

The present study only assessed risk for dislocation caused by collision with the artificial joint or skeleton, and did not take into account the effects of soft tissue. However, we were able to quantitatively assess angle of the hip joint for some leg positions involved with various common coital positions. The results showed that the supine position at maximum abduction in flexion is relatively safe, since the range of motion before collision would occur was relatively wide. In addition, top and kneeling positions at maximum extension were relatively safe, but caution must be exercised at maximum flexion, as not much extra angle was available in flexion and medial rotation.

We have developed a novel system of 4-dimensional motion analysis after total hip arthroplasty (THA) that can aid in preventing dislocation by assessing safe range of motion for patients in several daily activities.

This system uses skeletal structure data from CT and motion capture data from an infrared position sensor. A 3-D model reconstructed from CT data is combined with the motion capture data. Using this system, we analyzed hip motion when getting up from and sitting down in a chair or picking up an object while sitting in a chair in 17 patients (26 hips) who underwent THA. To assess the accuracy of this system’s measurements, open MRI was used to evaluate positions of skin markers against bones in 5 healthy volunteers in various postures.

No impingement between bones and/or implants was found in any subjects during any activities. However, mean angle at the point of maximum hip flexion was different for each patient. The open MRI results indicated that average error in hip angle of the present system was within 5 degrees for each static posture.

The functional position of the pelvis during daily activities must be taken into account when assessing the real risk of dislocation. The present system enables dynamic analysis involving not only alignment of components and bones of each patient, but also individual differences in characteristics of daily motions. Further investigation using this system can help determine safe ranges of motion for preventing hip dislocation, improving the accuracy of individualized guidance for patients regarding postoperative activities.

Alendronate is a potent inhibitor of bone resorptive activity, and has been shown to prevent and restore periprosthetic osteolysis in experimental models. A preliminary study was conducted to examine clinical usefulness of a lendronate treatment.

Twenty-five patients (27 hips) with radiological evidence of osteolysis after cemented total hip arthroplasty were included. Of these, 14 patients (15 hips) were administered 5 mg of alendronate daily (alendronate group), and 11 patients (12 hips) did not receive alendronate treatment (control group). The subjects were followed up for 12 months, using radiological examinations and biochemical markers. The radiological analysis was evaluated blindly by 2 joint arthroplasty experts, each with more than 10 years of experience, without knowledge of alendronate administration.

In the alendronate group, average serum bone alkaline phosphatase and urinary excretion of the N-telopep-tide of type I collagen values decreased from the baseline values after administration of alendronate, to 71% and 76% of baseline at the 3-month examination, and 57% and 62% at the 1-year examination, respectively. In the control group, expansion of osteolysis was found in 5 hips (42%) and no hip showed restoration of osteolysis. In the alendronate group, expansion of osteolysiswas found in 2 hips (13%), and restoration of osteolysis was found in 5 hips (33%). There was a statistically significant difference in ratio of hips with osteolysis restoration between the 2 groups (p< 0.05). In the alendronate group, there was no significant difference in age, average linear wear rate of polyethylene, and the biochemical markers, between the hips with and without diminishment of osteolysis.

Conclusions: The present results indicate that clinicala-lendronate treatment can prevent and restore periprosthetic osteolysis, which is generally thought to require surgical intervention. These findings warrant further study of the effects of duration and dose of alendronate treatment, component materials, and component fixation methods.

The current study aimed to analyze in vivo kinematics during deep knee bending motion by subjects with fully congruent designed mobile-bearing total knee arthroplasty (TKA) allowing axial rotation and anterior/posterior (AP) gliding.

Twelve subjects were implanted with Dual Bearing-Knee (DBK, slot type: Finsbury, UK) prostheses. These implants include a mobile-bearing insert that is fully congruent with the femoral component throughout flex-ion and allows axial rotation and a 4–6 mm limited AP translation. Sequential fluoroscopic images were taken in the sagittal plane during loaded knee bending motion. In vivo kinematics of knee prostheses were computed accurately using a 2D/3D registration technique, which uses computer-assisted design models to reproduce the spatial position of metallic femoral and tibial components from calibrated single-view fluoroscopic images.

The average femoral component demonstrated 13.4° external axial rotation for 0° to 120° flexion. On average, the medial condyle moved anteriorly 6.2 mm for 0° to 100° flexion, then posteriorly 4.0 mm for 100° to 120° flexion. On average, the lateral condyle moved anteriorly 1.0 mm for0° to 40° flexion, then posteriorly 8.7 mm for 40° to 120° flexion. The average subject experienced a lateral pivot pattern from −5° to 60° flexion, a central pivot pattern from 60° to 100° flexion, and a rollback pattern which bilateral condyles moved backward from 100° to 120° of knee flexion.

Subjects with DBK mobile-bearing TKA in some-degree reproduced femoral external rotation during increasing knee flexion and bicondylar posterior rollback during terminal flexion, due to surrounding soft tissue structures. The geometry of replaced articular surfaces and mobility of the mobile-bearing insert produced lateral-to-central pivoting motions during the flexion cycle, a phenomenon not typically observed in normal knees. Using the current technique, we characterized the unique kinematics of fully congruent designed DBK mobile-bearing knee prostheses.

We used three-dimensional movement analysis by computer modelling of knee flexion from 0° to 50° in 14 knees in 12 patients with recurrent patellar dislocation and in 15 knees in ten normal control subjects to compare the in vivo three-dimensional movement of the patella. Flexion, tilt and spin of the patella were described in terms of rotation angles from 0°. The location of the patella and the tibial tubercle were evaluated using parameters expressed as percentage patellar shift and percentage tubercle shift. Patellar inclination to the femur was also measured and patellofemoral contact was qualitatively and quantitatively analysed.

The patients had greater values of spin from 20° to 50°, while there were no statistically significant differences in flexion and tilt. The patients also had greater percentage patellar shift from 0° to 50°, percentage tubercle shift at 0° and 10° and patellar inclination from 0° to 50° with a smaller oval-shaped contact area from 20° to 50° moving downwards on the lateral facet.

Patellar movement analysis using a three-dimensional computer model is useful to clearly demonstrate differences between patients with recurrent dislocation of the patella and normal control subjects.

We investigated the three-dimensional morphological differences of the articular surface of the femoral trochlea in patients with recurrent dislocation of the patella and a normal control group using three-dimensional computer models.

There were 12 patients (12 knees) and ten control subjects (ten knees). Three-dimensional computer models of the femur, including the articular cartilage, were created. Evaluation was performed on the shape of the articular surface, focused on its convexity, and the proximal and mediolateral distribution of the articular cartilage of the femoral trochlea. The extent of any convexity, and the proximal distribution of the articular cartilage, expressed as the height, were shown by the angles about the transepicondylar axis. The mediolateral distribution of the articular cartilage was assessed by the location of the medial and lateral borders of the articular cartilage.

The mean extent of convexity was 24.9° sd 6.7° for patients and 11.9° sd 3.6° for the control group (p < 0.001). The mean height of the articular cartilage was 91.3° sd 8.3° for the patients and 83.3° sd 7.7° for the control group (p = 0.03), suggesting a wider convex trochlea in the patients with recurrent dislocation of the patella caused by the proximally-extended convex area. The lateral border of the articular cartilage of the trochlea in the patients was more laterally located than in the control group.

Our findings therefore quantitatively demonstrated differences in the shape and distribution of the articular cartilage on the femoral trochlea between patients with dislocation of the patella and normal subjects.

We have measured the three-dimensional patterns of carpal deformity in 20 wrists in 20 rheumatoid patients in which the carpal bones were shifted ulnarwards on plain radiography. Three-dimensional bone models of the carpus and radius were created by computerised tomography with the wrist in the neutral position. The location of the centroids and rotational angle of each carpal bone relative to the radius were calculated and compared with those of ten normal wrists.

In the radiocarpal joint, the proximal row was flexed and the centroids of all carpal bones translocated in an ulnar, proximal and volar direction with loss of congruity. In the midcarpal joint, the distal row was extended and congruity generally well preserved. These findings may facilitate more positive use of radiocarpal fusion alone for the deformed rheumatoid wrist.

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.

Background: Juxta-articular intraosseous cystic lesions (JAICL) are common lesion in patients with rheumatoid arthritis (RA) and could cause spontaneous pathological fractures and extensive joint destruction. Although surgical treatment is well indicated for benign bone tumour such as solitary bone cyst, RA induced JAICL have been rarely treated surgically because of following reasons. The first is the possible re-absorption of grafted bone due to disease progression. The second is donor site problem of iliac bone autografting. The third is limitation of autograft for possible operations in the future. The fourth is the lack of bone graft substitutes with good osteoconductivity. We have developed the interconnected porous calcium hydroxyapatite ceramic (IP-CHA) with excellent osteoconductivity. The IP-CHA achieved major incorporation with host bone much more rapid than the other porous calcium hydroxyapatite ceramics. We evaluated the feasibility and effectiveness of curettage and packing with the IP-CHA for the treatment of JAICL in RA patients.

Methods: Nine JAICL in 7 RA patients were treated by curettage and packing with IP-CHA. Eight lesions were impending pathological fractures. Two were male and five were female, the average age of operation was 57.8 years (range, forty-nine to seventy-two years). Follow-up assessment was based on final radiography at an average of 10.9 months after surgery (range, five to seventeen months). The expansion of the cystic lesions around the implanted IP-CHA and the re-absorption of the IP-CHA itself, which means erosion or increasing porosity of implanted IP-CHA, were assessed on the basis of the radiographies at just after operation and final follow up.

Results: The locations were as follows: distal radius, 6 lesions; distal ulna, 1; proximal tibia, 1; distal fibula, 1. No lesions showed the re-absorption of implanted IP-CHA itself. One of 9 lesions showed out-expansion of radiolucent area around the implanted IP-CHA without re-absoption of IP-CHA itself at the final follow-up. There were no postoperative fractures as complication.

Conclusions: These results suggested that surgical intervention with the IP-CHA could be useful for prevention of pathological fractures due to arthritis related JAICL. The efficacies of this technique might be augmented by amelioration of disease activity with concomitant drug therapy including biologics, since there was one case with out-expansion of cystic lesions in RA patients.

We reviewed the results of 51 patients with benign bone tumours treated by curettage and implantation of calcium hydroxyapatite ceramic (CHA). The mean follow-up was 11.4 years (10 to 15.5). Post-operative fractures occurred in two patients and three had local recurrences; three had slightly limited movement of the adjacent joint and one had mild osteoarthritis. There were no allergic or neoplastic complications. In all cases, radiographs showed that the CHA was well incorporated into the host bone.

Statistical analysis showed that absorption of the implanted CHA was greater in males (odds ratio, 6.2; 95% CI, 1.6 to 23.7) and younger patients (odds ratio, 0.6 for increase in age of 10 years; 95% CI, 0.91 to 0.99). However, the implanted CHA was not completely absorbed in any patient.

We conclude that CHA is a useful and safe bone substitute for the treatment of benign bone tumours.

We investigated the rates of expression of bone morphogenetic protein-2 (BMP-2) in 29 adult patients with high-grade malignant fibrous histiocytoma of soft tissue, using the BMP-2-specific monoclonal antibody, AbH3b2/17, and found that they ranged from 1.9% to 78.9%. The survival at five years of the groups expressing high (≥30%) and low (< 30%) levels of BMP-2 was 85.7% and 36.3%, respectively. Multivariable analysis showed that only BMP-2 had prognostic significance for continuous disease-free survival and for overall survival (p < 0.05). Our findings indicate that over-expression of BMP-2 in malignant fibrous histiocytoma of soft tissue is the most reliable prognostic indicator of the parameters assessed.

Introduction: The purpose of this study is to evaluate the clinical and radiogra phic outcome of patients with secondary osteoarthritis of the hip, who underwent custom-made cementless THA.

Methods: Between January 1994 and June 1997, 98 prim ary cementless custom-made THA’s were performed in 76 patients with secondary osteoarthritis and reviewed at mean 6 years follow-up (range: 4 – 7.5 years). Nine patients had a previous femoral osteotomy. There were 69 females and seven males. The mean age at operation was 54 years (40 – 73 years). Custom-made, 125 mm-long, titanium femoral components with blasted surface were fabricated based on the computerized tomography.

Results: The mean Harris Hip Score improved from 43 to 95 points. 97 patients (99%) had more than 80 points for total score, and 2 patients (2%) had thigh pain at the latest follow-up. Radiographically, 86 hips (87%) showed obviously extensive bone ongrowth onto the middle part of the stem while 8 hips (9%) showed stable fibrous fixation. Four hips (4%) were unstable: more than 2 mm subsidence in 2 hips and more than 2 degrees varus migration in 2 hips. Of these 4 hips, 2 had intraoperative cracks of the poximal femur and 2 had varus positioning of the stem.

Discussion and conclusion: Cementless THA has been advocated to enhance fit and fill of variable hip geometry. However, some clinical studies failed to show that custom implants significantly improve clinical success or implant longevity because their surface finish was not optimal. Custom-made titanium femoral components with blasted surface showed good clinical results. The reasons for radiolographical failures were because of intraoperative technical errors and these might be derived from 125 mm-long stem with maximum canal fill. A shorter stem may be an option because it may improve the feasibility of stem insertion and the distal fill.

We investigated the effect of the Birmingham hip resurfacing (BHR) arthroplasty on the bone mineral density (BMD) of the femur. A comparative study was carried out on 26 hips in 25 patients. Group A consisted of 13 patients (13 hips) who had undergone resurfacing hip arthroplasty with the BHR system and group B of 12 patients (13 hips) who had had cementless total hip arthroplasty with a proximal circumferential plasma-spray titanium-coated anatomic Ti6A14V stem. Patients were matched for gender, state of disease and age at the time of surgery. The periprosthetic BMD of the femur was measured using dual-energy x-ray absorptiomentry of the Gruen zones at two years in patients in groups A and B.

The median values of the BMD in zones 1 and 7 were 99% and 111%, respectively. The post-operative loss of the BMD in the proximal femur was significantly greater in group B than in group A. These findings show that the BHR system preserves the bone stock of the proximal femur after surgery.

Introduction: Progression of collapse in osteonecrosis of the femoral head (ONFH) is greatly influenced by repair reactions, especially bone resorptive activity. This study was performed to test if systemic alendronate treatment, a potent inhibitor of osteoclast activity, can prevent the development of collapse in ONFH.

Materials and Methods: Daily administration of oral alendronate (5mg/day) was started in 14 hips in 11 patients with ONFH (Alendronate group). At the beginning of the study (3, 6, 12 months), plain radiographs, T1-weighted MR imaging, and biochemical makers of osteoclast activity (N-telopeptide of type-I collagen) and osteoblast activity (Bone-specific alkaline phosphatase), were examined. At 12 months, MR imaging was repeated. Eleven hips in 6 patients with ONFH who did not receive alendronate administration were considered as the control group.

Results: There was no significant difference with respect to gender distribution, etiology factors, initial ARCO stages, and extent of necrosis in the two groups. In the alendronate group, there was an early decrease of osteoclast activity at 3 months, with a decrease to 62% at 12 months, while the decrease of osteoblast activity was smaller with 80% at 12 months. Development of collapse was observed in 4 of the 11 hips (36%) in the control group, and in none of the 14 hips in the alendronate group. There was a significant difference of collapse development between the two groups (p=0.026, Mann-Whitney U-test). Signal change on serial MR images was observed in 5 of 9 hips (56%) in the control group, with only one of 9 hips (11%) in the alendronate group.

Discussion: The low incidence of signal change on serial MR images may reflect the decrease of repair activity in the alendronate group. The present study was the first clinical trial to show that alendronate has a significant preventive effect of collapse development in patients with osteonecrosis of the femoral head.

Introduction: In order to investigate the relationship between the degeneration of the acetabular cartilage and the radiological staging of osteonecrosis of the femoral head, the following study was performed.

Materials and Methods: Acetabular cartilage with sub-chondral bone was taken from the superior dome from 34 hips from 30 patients undergoing total hip arthroplasty due to osteonecrosis of the femoral head. The specimens were stained with hematoxylineosin and safranin-O, and were evaluated as to the thinning of cartilage, fibrillation, clefts, and proliferation of chondrocytes. There were 18 females and 12 males with an average age of 49 years. We used the radiological staging system proposed by the working group of the Specific Disease Investigation Committee under the auspices of the Japanese Ministry of Health, Labor and Welfare. There were eight hips in stage IIIA disease (collapse of the femoral head less than 3 mm), 19 hips in stage IIIB disease (collapse 3 mm or greater), and seven stage IV disease hips.

Results: All 34 specimens showed histological abnormalities. In eight stage IIIA hips, six hips were mild and two were moderate histological degeneration. In 19 stage IIIB hips, five hips were mild, six were moderate, and eight had severe arthrosis. Seven stage IV hips had severe arthrosis.

Discussion: Although the radiographs cannot demonstrate early degeneration of cartilage, degenerative changes were present in all stage III hips. Histological degenerative changes in stage IIIB hips were more severe than those in stage IIIA hips. These findings should be kept in mind in treating patients with osteonecrosis of the femoral head.

Introduction: There is controversy over whether the lesions of osteonecrosis of the femoral head (ONFH) will spontaneously decrease. This study reports a longitudinal study of lesion volume using high-resolution serial MRI and recently developed techniques for image registration to realign serial images.

Materials and Methods: Baseline and follow-up (minimum one year later) MRI scans were carried out on 15 patients (18 hips). Accurate subvoxel registration was performed and subtraction images were produced to reveal areas of regional necrotic lesion change. Volume-to-femoral head ratio (VFR) was calculated to normalize the measured volume to the total femoral head volume.

Results: Three of 18 hips showed spontaneous reductions in the size of the lesions. They were all related to steroid use and were within one year after initial steroid treatment The mean volume decrease of these 3 hips was 3.4 ± 2.0 cm³ (SD) and its VFR was 6.8 ± 3.1 % (SD). Mean necrotic lesion volumes at baseline of decreasing lesions and unchanged lesions were 4.6 ± 2.5 cm³ (VFR, 9.1 ± 3.9 %) and 7.5 ± 5.5 cm³ (VFR, 16.7 ± 12.4 %), respectively.

There was no statistically significant difference in baseline lesion volume between decreasing lesions and unchanged lesions.

Discussion: In conclusion, some early lesions within one year after onset can decrease in size on MRI, regardless their size at baseline.

[Objectives] Hallux valgus, dorsal sublaxation or dislocation of metatarsophalangeal joints and clawing of the lateral toes are seen frequently in patients with rheumatoid arthritis (RA). Resection arthroplasty of the metatarsophalangeal joints (MTP joints) are widely used to correct these forefoot deformities and the clinical results are almost good. However lateral toes tend to displace dorsally and painful callosity tends to recur. We used the metatarsal shortening offset osteotomy for shortening and dorsal/medial displacement of the prominent metatarsal head. In this report, we introduce the surgical techniques of shortening offset osteotomy and postoperative changes of plantar pressure measured with F-scan system (Tekscan, Inc. ), and review the short term result during 1 to 4 year follow-up.

[Materials and Methods] This study involved 26 feet of 18 patients with RA which were performed with the metatarsal osteotomy for lateral toes and followed more than 1 year (average follow-up 29 months, range 14–46 months). The average age of the 17 women and 1 man was 61 years (range, 51–77 years). The mean duration from the onset of RA to operation on the forefoot was 17 years (range, 7–42 years). Skin incision was placed on the dorsum of the foot and the extensor digitorum brevis and longus were severed (or elongated). After reposition of MTP joint, transverse osteotomy of distal fifth of the lateral metatarsal bone was performed with resection of few millimeters length metaphysial bone. Cortical bone of the distal end of the proximal stump was chiseled into a small rod between two ditches with rongeur and then the rod was put into medullary canal mortise of distal stump. This procedure make offset shift of metatarsal head medially or dorsally. Swanson implant arthroplasty, distal osteotomy was performed on the great toe. Postoperative clinical and radiological results were evaluated with AOFAS rating system. We measured dynamic plantar pressure before and one year after operation in one representative case.

[Results] At the time of follow-up, the mean AOFAS score was 80 points (59–95) and the mean pain score was 36 points. The recurrence of painful callosity was one case. Nevertheless, the range of motion of the MTP joint remained low: 30 degrees and less in 16 feet (62%) including 3 bony ankylosis of MTP joints. There was no nonunion case. [Discussion]

Resection arthroplasty has been accepted as the treatment of choice for forefoot deformities in RA patients. Recent advance of drug therapy against RA encouraged us to preserve the joint in correction of forefoot deformities. Our technique aimed at preservation of the function of the MTP joints and is suitable for mild deformities in which only one or two rays are involved. Furthermore it is easy to correct the deformity of spray foot and reduce the plantar prominence of metatarsal head. This study revealed the good clinical result in short term follow-up. Although the long term result must to be waited, this method is one of recommendable options for RA patients with forefoot deformities.

We developed a new type of bioactive bone cement, CAP (Hydroxyapatite composite resin; composed of 77% w/w hydroxyapatite granules and bisphenol-A glycidyl methacrylate-based resin) for bony defect filling. Elastic modulus of CAP is similar to a cortical bone, while it is injectable before hardening and physiologically bonding with bone in 4 to 8 weeks. We present a new method of treatment for unstable Colles’ fracture with this material in clinical use.

Experimental comminuted Colles’ fracture was produced in three fresh frozen cadavara. Fracture was reduced and fixed percutaneously with K-wires. 4.5mm drill hole was opened on the radial cortex 3cm proximal to the fracture site. Comminuted fragments were pushed-up to the subchondral area with a blunt rod and CAP was injected through the same way. After cement hardening, K-wires were removed. X-ray photos were examined before fracture, after fracture and after reconstruction with CAP, in order to evaluate the shape of the radius. CT was examined to evaluate the placement of CAP.

Radiographic parameters of radii were well recovered after reconstruction with CAP. Over correction of the radial length was observed in one bone but good reduction was generally achieved (Table). This means realignment of the distal radioulnar joint, which results in good outcome clinically. In transverse section of CT, 41 to 69% (average 55%) of subchondral area was filled with CAP. Filling of CAP was better in an osteoporotic bone. These results show the usefulness of this material for treatment of unstable Colles’ fracture especially in osteoporotic patients.

We report two cases of surface deterioration of a zirconia ceramic femoral head associated with phase transformation after total hip arthroplasty. One head was retrieved at revision due to recurrent dislocation after six years and the other because of failure of the locking mechanism of the polyethylene liner after three years. The monoclinic content of the zirconia ceramics rose from 1% to about 30% on the surface of the heads. SEM revealed numerous craters indicating extraction of the zirconia ceramics at the surface. Surface roughness increased from an initial value of 0.006 3m up to 0.12 3m. This is the first report to show that phase transformation of zirconia ceramics causes deterioration of the surface roughness of the head in vivo after total hip arthroplasty.

We present three cases of intramuscular haemangioma adjacent to bone in the lower limb. All patients had local pain during the third decade. Plain radiographs showed an irregular or hypertrophic periosteal reaction on the shaft of the fibula and an intramuscular mass adjacent to the bone with inhomogenous high signal intensity on MRI. These lesions mimic periosteal or parosteal tumours.

We reviewed 277 patients with soft-tissue sarcoma (STS) treated between 1975 and 1995 to study the incidence, distribution, time of appearance, and radiological findings of skeletal metastases. Of these, 28 (10.1%) had metastases within a mean period of 18.6 months after admission.

The incidence of skeletal metastases differed among the histological subtypes of sarcoma; alveolar soft-part sarcoma, dedifferentiated liposarcoma, angiosarcoma, and rhabdomyosarcoma tended to show higher incidences. The regional bones close to the primary tumour were affected in 13 (46.4%) of the 28 patients, and the axial bones in 18 (64.3%). Radiologically, the metastatic bony lesions predominantly showed osteolytic changes, and there were pathological fractures in 21 of 44 lesions.

We have investigated the significance of local recurrence on survival in 173 patients with localised soft-tissue sarcomas of the limbs and of the trunk.

The overall survival rates at five and ten years were 75.2% and 68.0%, respectively. After definitive surgery at our hospitals, there was local recurrence in 25 patients (14.5%). After inadequate operations elsewhere, there was a higher incidence of late local recurrence (28.3%), in comparison with those with primary tumours treated by us (9.0%), or patients referred to us immediately after inadequate surgery elsewhere (10.2%). Because of small numbers these differences in the survival rates were not statistically significantly different.

Univariate survival analysis showed that local recurrence after definitive surgery (p = 0.006) together with the histological grade (p = 0.0002), the size of the tumour (p = 0.002), its depth in relation to deep fascia (p = 0.003), and the surgical margin (p = 0.0001) were the significant prognostic factors. Local recurrence at the initial presentation did not affect survival. Multivariate analysis showed that local recurrence after definitive surgery also lost its apparent prognostic significance.

We report the case of a 19-year-old man with inguinal lymphadenopathy caused by metallic debris from the loosening of a prosthesis inserted after tumour resection. Large amounts of wear debris may be released from such massive replacements, and surgeons should be aware of the range of possible adverse effects.

We report 60 benign bone tumours treated by resection and curettage followed by the implantation of calcium hydroxyapatite ceramic (CHA). After follow-up of six to 60 months (average 36), no patient had local recurrence of the tumour or any adverse effects from the implants. In almost all cases radiography showed that the CHA was well-incorporated into the host bone, with new bone formation in and around the CHA. Corrective remodelling of deformed bone and normal fracture healing suggested that there was normal bone turnover in the presence of the CHA. Histology of biopsies from seven patients showed bone ingrowth into the pore structure of CHA in the central zone of some defects by one year after implantation. CHA appears to be a useful substitute for bone graft in the treatment of some benign tumours.