Toshiro Otani

Metal ions induce bone-resorbing cytokine production through the redox pathway in synoviocytes and bone marrow macrophages.

To evaluate the biological reactions to metal ions potentially released from prosthetic implants, we examined the ability of metal ions to produce bone-resorbing cytokines and the underlying mechanism using synoviocytes and bone marrow (BM) macrophages. The cells were incubated with NiCl(2), CoCl(2), CrCl(3) or Fe(2)(SO(4))(3) at optimal concentrations, which are detectable in joint fluid following total joint arthroplasty. The production of interleukin-1beta, interleukin-6 and tumor necrosis factor-alpha were enhanced by all metal ions tested as determined by enzyme-linked immunosorbent assay. From the results of electrophoresis mobility shift assay, all metal ions enhanced the DNA-binding activity of nuclear factor kappaB (NF-kappaB), and p50-p65 heterodimers and p50 homodimers were the major subunits. These effects of the metal ions were considerably blocked by pyrrolidine dithiocarbamate (PDTC) known as a radical scavenger. An electron spin resonance study clearly demonstrated the ability of metal ions to generate activated oxygen species (AOS), especially hydroxyl radicals (*OH), which accounts for PDTC-blockade of metal ion-induced NF-kappaB activation and subsequent cytokine production. Taken together, our data raised the possibility that small amounts of metal ions released from prosthetic implants activate synoviocytes and BM macrophages through the AOS-mediated process (i.e. the redox pathway), and contribute to the initiation of osteolysis at the bone-implant interface.

A quantitative assessment of varus thrust in patients with medial knee osteoarthritis

Varus thrust is an abnormal lateral knee motion frequently seen in patients with medial knee osteoarthritis (OA) during gait. It is a worsening of the alignment in the stance phase of the gait cycle and closely relates to disease progression. In this study, we measured the thrust quantitatively using skin markers and examined the relationship to other static and dynamic parameters. Forty-four knees in 32 patients (mean age, 72years; range, 64-81years) who exhibited the radiographic OA at least grade 2 according to the Kellgren-Lawrence (K-L) scale were enrolled. Gait analysis was performed for each patient to measure the amount of thrust and knee adduction moment. The amounts of thrust in subjects with K-L grades 2 (25 knees), 3 (13 knees), and 4 (6 knees) were 2.4°(±1.3°), 2.8°(±1.4°), and 7.2°(±5.3°), respectively and the knee adduction moments were 3.6(±1.5) %BW⁎Ht, 3.9(±1.2) %BW⁎Ht and 6.9(±2.2%) BW⁎Ht, respectively. The amount of thrust also exhibited significant correlation to static radiographic alignment (R=0.47: 95% confidence interval 0.67-0.21, p=0.0038) and showed greater correlation to the knee adduction moment (R=0.73: 95% confidence interval 0.84-0.55, p<0.001), which has been identified as an important dynamic index of the disease. The amount of thrust, which is able to be measured by simple inexpensive equipment, correlated to static and dynamic parameters and may offer an important clinical index for knee OA.

Knee flexion contracture will lead to mechanical overload in both limbs: A simulation study using gait analysis

The purpose of the current study was to investigate the effect of knee flexion contracture on the knee mechanics both in affected and contralateral limbs during gait. Ten healthy old women, with mean age of 62 years, participated. Unilateral knee flexion contractures of 0, 15, and 30 degrees were simulated with a knee brace. All subjects performed walking trials with or without the simulation. Net knee extension moments, net knee adduction moments (%BW Ht), external knee forces (%BW), and maximum axial loading rate (%BW/s) at the knee were calculated both in contracture side and non-contracture side under different contracture conditions. Bilateral net knee extension moment gradually increased as the angle of contracture increased. The net knee extension moments in non-contracture limb were significantly larger with 15 and 30 degrees contracture than those without the contracture. Net knee adduction moment in non-contracture limb significantly increased with 15 and 30 degrees contracture. The knee shearing forces in contracture side and the knee compressive force in non-contracture side also significantly increased with 15 and 30 degrees simulation. As the flexion contracture became greater than 15 degrees , maximum axial loading rate also significantly increased in non-contracture side. From our results, the knee flexion contracture greater than 15 degrees led to mechanical overloads in both limbs. Correction of the contracture is clinically important to avoid any adverse effect.

Extension Limitation in Standing Affects Weight-Bearing Asymmetry After Unilateral Total Knee Arthroplasty

The aim of this study was to evaluate weight-bearing condition after unilateral total knee arthroplasty (TKA) during standing and to examine whether the condition affects knee kinetics during gait in both limbs. Twenty-five patients, who underwent unilateral TKA for symptomatic bilateral osteoarthritis and who were on average 74 years old, participated. As a result, operated limbs became dominant in 80% of the patients. The other 20%, who had lack of knee extension during standing, showed more weight bearing in nonoperated knees. Furthermore, extension limitation in the operated knee in standing led to mechanical overload in the contralateral limb during gait. Therefore, to avoid progression of the osteoarthritis in the contralateral knee, it is important to acquire full extension in the operated knees during standing after unilateral TKA.

Axis location of tibial rotation and its change with flexion angle.

The magnitude and location of the axis of tibial rotation were measured at 15° increments between 0° and 90° flexion using 24 normal anatomic knee specimens, and their changes with flexion angle were investigated. The magnitude of tibial rotation was small (8.3°) at 0° flexion, but increased rapidly as the flexion angle increased and reached a maximum rotation (31.7°) at 30° flexion. It then decreased again with additional flexion (24.8° at 90° flexion). The location of the axis was close to the tibial insertion of the anterior cruciate ligament at 0° flexion, gradually moving toward insertion of the posterior cruciate ligament (observed at 45° and 60° flexion), and then moved anteriorly again with additional flexion: the axis was approximately equidistant from the two cruciate insertions at 90° flexion. The results showed that a relatively large degree of tibial rotation was possible in a normal knee and that the location of the axis remained approximately in the area between the two cruciate ligament insertions throughout the range of flexion. However, the location of the axis changed with the flexion angle within this area according to the changes in direction and tension of the cruciate ligaments and the surrounding soft tissues.

Kinematic motion of the anterior cruciate ligament deficient knee during functionally high and low demanding tasks

The purpose of this study was to determine whether mechanical adaptations were present in patients with anterior cruciate ligament (ACL)-deficient knees during high-demand activities. Twenty-two subjects with unilateral ACL deficiency (11 males and 11 females, 19.6 months after injury) performed five different activities at a comfortable speed (level walking, ascending and descending steps, jogging, jogging to a 90-degree side cutting toward the opposite direction of the tested side). Three-dimensional knee kinematics for the ACL-deficient knees and uninjured contralateral knees were evaluated using the Point Cluster Technique. There was no significant difference in knee flexion angle, but an offset toward the knee in less valgus and more external tibial rotation was observed in the ACL-deficient knee. The tendency was more obvious in high demand motions, and a significant difference was clearly observed in the side cutting motions. These motion patterns, with the knee in less valgus and more external tibial rotation, are proposed to be an adaptive movement to avoid pivot shift dynamically, and reveal evidence in support of a dynamic adaptive motion occurring in ACL-deficient knees.

Accuracy of Implant Positioning for Minimally Invasive Total Knee Arthroplasty in Patients With Severe Varus Deformity

Minimally invasive surgery (MIS) in total knee arthroplasty (TKA) reportedly yields decreased patient morbidity and a rapid return of function, but how much deformity can be accepted for MIS-TKA remains unclear. This study investigated 238 knees from 218 consecutive patients who underwent MIS-TKA. Patients were divided into groups with tibiofemoral mechanical axis (TFM) 195 degrees or greater and TFM less than 195 degrees, then clinical and radiographic results were compared. Similar improvements in knee score at 3 months postoperatively were obtained in the both groups, whereas radiographic accuracy of the coronal alignment in the TFM >or=195 degrees group was inferior to that in TFM <195 degrees group. Postoperative TFM was significantly worsened in patients with lateral bowing angle of the femoral shaft (LBFS) 4 degrees or greater, and 53% of patients in the TFM >or=195 degrees group displayed LBFS 4 degrees or greater, explaining the inferior radiographic accuracy in this group compared with the TFM <195 degrees group. These results indicate that use of MIS techniques decreases radiographic accuracy, particularly in patients with severe genu varum and increased LBFS.

Extensive post-traumatic ossification of the patellar tendon: A REPORT OF TWO CASES

Two men, aged 21 and 50 years, were seen with ossification of the patellar tendon after injury to the knee in adolescence. They complained of pain and had patella alta. Large bony masses were excised from below the affected patellae. The patellar tendon was then reconstructed using a Leeds-Keio ligament. The results at six and ten years, respectively, were good, with neither patient having pain or an extension lag.

Gigantic popliteal synovial cyst caused by wear particles after total knee arthroplasty.

We present a case exhibiting persistent joint effusion and formation of a gigantic popliteal synovial cyst 8 years after total knee joint arthroplasty. Assessment using flow cytometry revealed that both joint and cyst fluid contained abundant macrophage-phagocytosing wear particles. This finding indicates that wear particles participated in formation of the cyst through the communication between the joint cavity and cyst. Intraoperatively, prominent villous synovial proliferation was observed in both the joint and cyst, and delamination failure of the polyethylene insert was identified. Because no evidence of prosthetic loosening was found, only polyethylene insert revision and synovectomy were undertaken, resulting in a successful outcome. This case suggests that synovial cyst formation in popliteal lesions might represent a sign of wear-particle generation after total knee joint arthroplasty.

Conservative treatment of isolated posterior cruciate ligament injury in professional baseball players: a report of two cases.

Conservative treatment is currently recommended for most isolated posterior cruciate ligament (PCL) injuries in athletes. However, it is not known whether conservative treatment is applicable even in high performance athletes with isolated PCL injury. The results in two extremely high performance athletes, professional baseball players with isolated acute PCL injury treated conservatively are reported. A catcher and an out fielder, who were regular players, hurt their knees in baseball games. Magnetic resonance images of the knee detected complete PCL rupture. Following a carefully guided physical therapy program, a 3-week period of immobilization of the knee in full extension was achieved with a knee brace, while performing hard quadriceps muscle strengthening exercise, and then running exercise was started. Six to eight weeks after injury, they were able to return fully to their original sporting activity despite tibial posterior translation on posterior drawer test, and to sustain this activity over 2 years. Switching of weight-bearing to non-weight-bearing in a deep knee flexion is considered to contribute to subjective instability in athletes with PCL-deficiency. Probably because our cases, even though extremely high performance athletes were infrequently subjected to such a situation while playing baseball, they were able to return to their pre-injury level of athletic performance without severe subjective instability through conservative treatment.