Nobuyuki Yoshino

Impact load transmission of the knee joint-influence of leg alignment and the role of meniscus and articular cartilage

OBJECTIVE The objective of this study was to evaluate load transmission in the cancellous bone of the tibia under static and impact load.BACKGROUND. Abnormal transmission of loads may result in osteoarthritis and fractures. However, the role of the cancellous bone in these processes is not well understood.METHODS. The compressive stresses in the subchondral bone, epiphysis and diaphysis of the tibia of porcine knees were measured under static and impact load using mini-pressure transducers. The tests were performed using a drop-tower type testing machine in neutral, varus and valgus alignments. Tests were repeated after meniscectomy and again after removing the articular cartilage.RESULTS. In the intact knee in all alignments, the highest stress on the medial side was found in the epiphysis, and in the subchondral bone on the lateral side. After meniscectomy, a significant increase was observed in the stress in the subchondral bone on both sides. After the articular cartilage was also removed, the stress in the subchondral bone increased again, but slightly.CONCLUSION. The importance of the meniscus in load transmission is supported by this study. The contribution of the articular cartilage to load transmission is less than that of the meniscus.Relevance. The patterns of static and dynamic load transmission observed in this study correlate with the sites of insufficiency fractures of the medial tibial plateau and traumatic lateral tibial plateau fractures observed clinically. Examination of the load transmission is key to a more complete understanding of the causes of osteoarthritis and tibial plateau fractures.

Prediction of mechanical properties of healing fractures using acoustic emission.

The objective of this study was to develop a non‐destructive method for monitoring fracture healing with acoustic emission (AE). Experimentally produced fractures of the rat femur were tested in tension and in torsion at 4, 6, 8 and 12 weeks after fracture. AE signals were monitored during these mechanical tests. The values for load and torque at the initiation of the AE signal were defined as new mechanical parameters. The apparent density and ash density of the fracture site were also measured at each time period. Tensile strength, tensile stiffness, maximum torque and torsional stiffness of the fracture site increased with time. The AE signal was detected before complete specimen failure. Load and torque for initiation of AE increased proportionally with increasing mechanical properties. The mineral density, however, reached a plateau at 8 weeks, when callus mechanical strength was approximately 50% of control. Load for initiation of AE was strongly correlated with the strength (r = 0.98), stiffness (r = 0.88), and failure strain (r = –0.63) of the callus. Torque for initiation of AE was highly correlated with the maximum torque (r = 0.95) and torsional stiffness (r = 0.93) of the callus. The findings of the present study indicated that some mechanical properties of healing fractures could be estimated by monitoring AE signals.

Delayed Aseptic Swelling After Fixation of Talar Neck Fracture with a Biodegradable Poly-L-Lactide Rod: Case Reports

A 63-year-old woman complained of acute swelling and pain in her ankle at 15 months, after fixation of a talar neck fracture with poly-L-lactide rods. Roentgenographic and laboratory data revealed no abnormalities, but T1-weighted magnetic resonance imaging showed a diffuse area of low intensity in the talus. After nonweightbearing for 1 month, local findings had disappeared and the area of low intensity shown by magnetic resonance imaging had decreased without surgical treatment. Although there have been some reports of aseptic swelling or synovitis after fixation of a fracture with polyglycolide rods or screws, there has been no report of such cases with poly-L-lactide rods or screws.

In situ strain and stress of nerve conduction blocking in the brachial plexus

The objective of the present study was to determine the in situ strain and stress of nerve conduction blocking in the brachial plexus. The measurement of the in situ tension stress inducing functional failure of the brachial plexus consisted of two steps. Step I (in vivo): The brachial plexus of the rabbit was stretched laterally until electrophysiological conduction blocking occurred. The distance between two dye marks placed on the lower trunk was simultaneously recorded using a video dimensional analyzer system. Step II (in vitro): The lower trunk that was removed was loaded again, and the nerve tension was recorded. The load at complete conduction blocking was determined by a load‐elongation curve. The results showed that when the in situ nerve strain reached 8.1 ± 0.5%, the compound muscle action potential was not evoked. The in situ load and stress were 2.5 ± 0.4 N and 0.89 ± 0.14 MPa, respectively, at complete conduction blocking. These findings should be helpful in understanding the mechanism of brachial plexus traction injury.

Case Report Arthroscopic treatment of voluntary superior dislocation of the patella

The patient, a 45-year-old woman who complained of crepitation and locking of her patella, had a voluntary superior dislocation of the patella and was arthroscopically treated. Radiography showed patella alta and osteoarthrosis in the patellofemoral joint. Fluoroscopy showed that, during active contraction of the quadriceps muscle, the tip of the osteophyte on the inferior edge of the patella was positioned at the same level as the osteophyte on the superior margin of the articular surface of the medial femoral condyle. The inferior edge of the patella could be made to catch on the femoral osteophyte by application of slight pressure to the patella. Arthroscopic resection of the osteophte was performed, and the postoperative course was uneventful. The patient reported no difficulty when she was last seen 1 year after the operation.

Unusual proximal tibiofibular synostosis

Abstract Proximal tibiofibular synostosis without multiple hereditary exostosis is extremely rare and only 7 cases have been reported in the literature. All of the previously reported cases accompanied deformities such as distal positioning of the proximal tibiofibular joint, leg length discrepancy, bowing of the fibula, and valgus deformity of the knee. The present case of a 24-year-old man had neither a history of trauma nor deformity around the knee. Therefore, it was suggested that this type of synostosis occurred after epiphyseal plate closure.Résumé Une synostose tibio-fibulaire proximale sans une maladie exostosante héréditaire multiple est extrémement rare et seulement sept cas ont été mentionnés dans la bibliographie. Tous les cas précédemment rapportés s’accompagnaient de déformations telles qu’un positionnement distal de l’articulation tibio-fibulaire proximale, une anomalie dans la longueur de la jambe, une courbure de la fibula avec une distance interosseuse augmentée, et/ou une déformation en valgus du genou. Le cas présent concerne un homme âgé de 24 ans ne présentant pas l’antécédent d’un trauma ni d’un déformation du genou. Par conséquent, il est suggéré que ce type de synostose s’est produit aprés une obturation de la plaque épiphysaire.

Recurrent horizontal dislocation of the patella in the sagittal plane. A case report.

Dislocation of the patella usually occurs to the lateral side, in the coronal plane. Horizontal dislocation of the patella in the sagittal plane is rare; we are aware of thirty-five previously reported cases, all of which involved dislocation into the intra-articular space between the femur and tibia3-6,10,12. The patient in the present report had a dislocation of the patella in which the patella rotated in the sagittal plane to lie horizontally at the level of the suprapatellar pouch without rupture of the patellar ligament. To our knowledge, there is no previous report of this condition having been treated operatively1,7,8,14. In December 1992, a sixty-five-year-old man tripped and fell while walking, after which he found the right knee to be locked in a slightly flexed position, with a prominence anteriorly at the level of the patella and a concavity distal to the prominence. He was able to manipulate the knee and reduce the dislocation without medical assistance. In …

Stress Analysis of the Proximal Tibia After Unicompartmental Knee Arthroplasty with Finite-Element Method

The finite-element method (FEM) has recently been employed to optimize the design of prostheses and to examine the mechanical problems of total knee arthroplasty. Stress analyses of unicompartmental knee arthroplasty (UKA) using FEM have not been previously reported, although UKA is a more popular procedure. The objective of this study is to determine the factors affecting the stress distribution of the tibia after UK A. A two-dimensional FEM in consideration of the heterogeneous and anisotropic properties of cancellous bone was apphed for stress analysis at the proximal tibia after UK A. Two types of implants, an ultrahigh molecular weight polyethylene (UHMWPE) type and a metal-backed type, were compared in three different alignments (neutral, varus, and valgus). Two different widths of implants and four different levels of the osteotomy (6–20 mm distal to the joint line) were then compared in neutral alignment. Higher stress concentrations were observed in the cancellous bone beneath the UHMWPE implants than beneath the metal-backed implants in all alignments. Stress concentrations in cancellous bone beneath implants in varus were higher than beneath bone in neutral alignment. High stress concentration at the intercondylar eminence was found in valgus alignment. There were no remarkable differences with respect to the level of the osteotomy.