Tetsunao Matsushita

Hypoxia-induced hyaluronan synthesis by articular chondrocytes: the role of nitric oxide

Abstract.Objective: Articular cartilage is an avascular tissue in which chondrocytes are exposed to hypoxic conditions. We previously demonstrated that reactive oxygen species (ROS) induced apoptosis of chondrocytes. We also demonstrated that nitric oxide (NO) was induced when chondrocytes were exposed to hypoxia and that NO inhibited the ROS-induced apoptosis. Hyaluronan (HA) is a high molecular weight glycosaminoglycan whose antioxidative effects have been reported. The purpose of the present study was to determine whether HA synthesis was induced in chondrocytes exposed to hypoxia, and, if so, whether the hypoxia-induced HA synthesis is regulated by NO. Methods: Bovine articular chondrocytes were used in this study. Levels of HA were determined by the sandwich enzyme-binding assay. Expression of HA synthase (HAS) was determined with reverse transcription-polymerase chain reaction. The production of NO was examined using the Griess reaction. We also determined inducible nitric oxide synthase (iNOS) enzyme synthesis using the histochemistry and Western blot analysis. Results: Chondrocytes cultured under hypoxic conditions exhibited enhanced HA synthesis. When the NO inhibitors, L-NMMA and L-NAME, were added, the hypoxia-enhanced HA levels in the culture medium were significantly inhibited. Conclusions: Endogenous NO synthesis plays an important role in hypoxia-enhanced HA synthesis.

Cyclic Tensile Stretch Stimulates the Release of Reactive Oxygen Species from Osteoblast-like Cells

It is known that the excessive generation of reactive oxygen species (ROS) is a significant factor in tissue injury observed in many disease states. To determine whether extreme levels of mechanical stress applied to osteoblasts enhances ROS synthesis, we loaded cyclic tensile stretch on osteoblast-like HT-3 cells. Cyclic tensile stretch loaded on these cells clearly enhanced ROS synthesis in a time- and magnitude-dependent fashion. Cyclic tensile stretch also enhanced superoxide dismutase (SOD) activity. The disruption of microfilaments with cytochalasin D abolished the stress-induced ROS synthesis. Rotenone, an inhibitor of the mitochondrial electron transport chain, enhanced stress-induced ROS synthesis. These data suggest that actin filament and mitochondria are involved in this action.

Hypoxia-induced nitric oxide protects chondrocytes from damage by hydrogen peroxide

AbstractObjective:Because articular cartilage has no vascular supply, chondrocytes are hypoxic under normal physiological conditions. Nitric oxide (NO) plays an important role in chondrocyte damage, such as apoptosis. Although oxygen stress with hydrogen peroxide was found to cause chondrocyte damage, these data were obtained under normoxic (21% O2) conditions. We investigated the effects of hypoxia on hydrogen peroxide-induced chondrocyte damage Methods:Bovine articular chondrocytes were used in this study. Proteoglycan (PG) synthesis and the induction of apoptosis were analyzed with [35S]-sulfate incorporation and annexin V staining, respectively. The induction of NO was examined using a fluorescent probe and RT-PCR. Results:Cells maintained at 5% O2 had the maximum PG synthesis. Under normoxic conditions, hydrogen peroxide inhibited PG synthesis and induced annexin V positive cells in a dose-dependent fashion. However, in those cells cultured under hypoxic (5%) conditions, the hydrogen peroxide-induced annexin V expression was attenuated. Chondrocytes exposed to hypoxia showed induction of NO. When the hypoxia-induced NO was inhibited, the hypoxia-enhanced PG synthesis was abolished and hydrogen peroxide clearly induced cell damage. Conclusions:Endogenous NO induced by hypoxia protects chondrocytes from apoptosis induced by an oxidative stress.

Comparison of MRI- and CT-based patient-specific guides for total knee arthroplasty

BACKGROUND The patient-specific guide for total knee arthroplasty (TKA) is created from the data provided by magnetic resonance imaging (MRI) or computed tomography (CT) scans. It remains unknown which imaging technology is suitable for the patient-specific guide. The purpose of this study was to compare the accuracy of implant positioning and operative times between the two types of patient-specific guides for TKA. METHODS Forty arthritic knees were divided into two treatment groups using MRI-based (PS-MRI group) or CT-based (PS-CT group) patient-specific guides in this prospective, comparative study. The guide in the PS-MRI group had a cutting slot, whereas that in the PS-CT group only had a pin locator. The operative times were compared between the two groups. The angular error and number of outliers (deviations >3°) of the implant position using pre- and postoperative CT were investigated in both groups. RESULTS The mean operative time was significantly shorter in the PS-MRI group (109.2 ± 16.5 min) than in the PS-CT group (129.5 ± 19.4 min) (p<0.001). There were no significant differences in the accuracy of the implant position regarding the coronal, sagittal, and axial planes between the groups (p>0.05). CONCLUSIONS To reduce the operative time, guides with additional functions, such as cutting and positioning, should be used. Both CT- and MRI-based-guides would result in the same accuracy in three planes but high inaccuracy in the sagittal plane. The use of patient-specific guide based on MRI might not be cost-effective. LEVEL OF EVIDENCE level 2.

Effects of cartilage remnants of the posterior femoral condyles on femoral component rotation in varus knee osteoarthritis

Preoperative planning of total knee arthroplasty (TKA) based on computerized tomography (CT) data can produce a femoral rotational error due to lack of information on the femoral cartilage thickness. The research question of this study is how much femoral rotational error is expected due to the cartilage remnants when using the posterior condylar angles (PCA, angle between the posterior condylar line and the surgical epicondylar axis (SEA)) on CT data. CT arthrography was performed for 35 consecutive varus osteoarthritic knees in 31 patients who underwent TKA, on which the cartilage thicknesses of the posterior femoral condyles were measured. The PCAs when including or excluding the cartilage remnants were also measured. The cartilage thicknesses of the medial and lateral posterior condyles averaged 0.39mm (SD=0.53) and 1.55mm (SD=0.26), respectively (p<0.0001). When the cartilage was included or excluded, the PCA averaged 2.2° (SD=1.5) and 3.3° (SD=1.5), respectively (p=0.002). The cartilage remnants in the posterior femoral condyles produced an average of 1.1° and a maximum of 2.1° of additional femoral external rotation when using CT data for the preoperative planning. CT scan measurements of femoral rotation are subject to error. Although this is said to be small and within the safety margin for setting the femoral component parallel to the trans-epicondylar axis, this difference should be considered by surgeons who use the posterior condylar axis, in order to avoid excessive external rotation of the femoral component.

Tibia Vara Affects the Aspect Ratio of Tibial Resected Surface in Female Japanese Patients Undergoing TKA

BackgroundTibia vara seen in Japanese patients reportedly influences the tibial component alignment when performing TKA. However, it is unclear whether tibia vara affects the component position and size selection.Questions/purposesWe therefore determined (1) the amount of medial tibial bow, (2) whether the tibia vara influences the aspect ratio of the tibial resected surface in aligning the tibial component with the tibial shaft axis, and (3) whether currently available tibial components fit the shapes of resected proximal tibias in terms of aspect ratio.MethodsWe measured the tibia vara angle (TVA), proximal varus angle (PVA), and the mediolateral and middle AP dimensions of the resected surface using three-dimensional preoperative planning software in 90 knees of 74 female patients with varus osteoarthritis. We determined the correlations of the aspect ratio with TVA or PVA and compared the aspect ratios to those of five prosthesis designs.ResultsThe mean TVA and PVA were 0.6° and 2.0°, respectively. The aspect ratio negatively correlated with both TVA and PVA (r = −0.53 and −0.55, respectively). The mean aspect ratio of the resected surface was 1.48 but gradually decreased with increasing AP dimension, whereas four of the five prostheses had a constant aspect ratio.ConclusionsThe aspect ratio of resected tibial surface was inversely correlated to the degree of tibia vara, and currently available prosthesis designs do not fit well to the resected surface in terms of aspect ratio.Clinical RelevanceThe design of a tibial component with a smaller aspect ratio could be developed to obtain better bone coverage in Japanese patients.

Estimation of frontal alignment error of the extramedullary tibial guide on the bi-malleolar technique: A simulation study with magnetic resonance imaging

PURPOSE The bi-malleolar technique for the extramedullary tibial guide is a representative method for determining the ankle center in total knee arthroplasty (TKA). The purpose of this study is to estimate three-dimensionally the lateral errors (difference between the real ankle center and the bi-malleolar center) and the varus angular errors of this technique under the condition that the malleolar prominences were correctly identified. METHODS Magnetic resonance images of 51 lower limbs from 51 healthy volunteers were analyzed. The lateral errors were measured, including or excluding the subcutaneous thickness, along the line perpendicular to the transmalleolar axis (TMA) or along the tibial anteroposterior (AP) axis. Furthermore, we evaluated the effects of the tibial torsion and the difference between the subcutaneous thicknesses on the malleoli on the lateral error. RESULTS When including the skin, the mean lateral errors of the ankle center observed along the line perpendicular to the TMA and along the tibial AP axis were 3.7 ± 1.4mm and 1.2 ± 1.5mm, respectively. The mean angular errors were 0.6 ± 0.2° and 0.2 ± 0.3°, respectively. A significant correlation between the tibial torsion and the lateral error was noted when observed along the tibial AP axis. The difference between the subcutaneous thicknesses on the malleoli affected the lateral error. CONCLUSION The errors were small enough to determine the mechanical axis of the tibia if the tibial guide could catch the bi-malleolar prominences of the ankle accurately and align along the tibial AP axis.

Influence of the Sagittal Reference Axis on the Femoral Component Size

The sagittal reference axes used for setting of the femoral component vary according to surgical methods. The purpose of the study was to clarify the relation of the sagittal reference axis with the anteroposterior (AP) length of the distal femur at the time of determining the femoral component size. Fifty consecutive varus osteoarthritic knees with primary total knee arthroplasty were divided into two groups according to surgical methods (intramedullary and extramedullary groups) and were examined based on CT data. AP length of the distal femur changed nearly 0.6mm corresponding to each 1° flexion of the sagittal reference axis. The size of the femoral component in the intramedullary group was larger than that in the extramedullary group. The sagittal reference axis had an influence on the component size.

Nonunited insufficiency fracture of the proximal tibia and the distal femur treated by high tibial osteotomy in a patient under hemodialysis

Insufficiency fracture occurs when normal or physiological activity stresses a bone that is deficient in mineral or elastic resistance [1]. Insufficiency fractures are most often seen in elderly women with postmenopausal osteoporosis. However, it can occur in a variety of conditions in which the mineral content or the elasticity of bone is impeded, including osteoporosis of any cause, osteomalacia, hyperparathyroidism, rheumatoid arthritis, fluoride treatment, diabetes mellitus, fibrous dysplasia, Paget’s disease of the bone, and also renal osteodystrophy [1–3]. Insufficiency fractures most commonly occur in the pelvic girdle and in the sacrum [2]. In addition, the tibia is also a common site of insufficiency fractures [2]. The tibial insufficiency fractures are often treated by conservative measures, such as adequate rest, immobilization with casts or braces, analgesic agents, and reduced activities in daily living [3–5]; surgical treatments are rarely indicated unless the fractures do not heal or heal incorrectly [6–9]. Therefore, there is very little information available when adopting the surgical treatment to the proximal tibial insufficiency fractures [2]. Here, we report a case of nonunited insufficiency fracture of the proximal tibia with a marked varus deformity in a hemodialysis patient, which was complicated with a supracondylar insufficiency fracture of the ipsilateral femur. To our knowledge, correction osteotomy for such a case has not been reported previously. Our patient was informed and gave the consent that data concerning the case would be submitted for publication.