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Taro Mawatari

Publications and source records attributed to Taro Mawatari.

11 recordsLinked to original sources
PubMed2006

Asymmetry of mediolateral laxity of the normal knee.

BACKGROUND: Understanding the normal kinematics of the joints is important for reconstructive surgery. However, only a few extensive studies have been done on medial and lateral laxity of the normal knee. METHODS: Radiographs of 50 normal knees were obtained under varus and valgus stress in both extension and flexion and the relative angle of the articular surface was measured. RESULTS: In extension, the mean angle was 4.9 degrees in varus stress and 2.4 degrees in valgus stress. In flexion, the mean angle was 4.8 degrees in varus stress and 1.7 degrees in valgus stress. Lateral laxity was significantly greater than medial laxity in both extension and flexion. CONCLUSIONS: Lateral laxity may be necessary for the medial pivot movement of the normal knee. There is some disagreement regarding the importance of pursuing the perfect rectangular gaps during total knee arthroplasty (TKA). The methods for measuring the tension of soft tissues during the operation are not accurate and do not always reflect the postoperative tensions of dynamic phases, such as walking and standing. Slight lateral laxity can be accepted with TKA, and further studies are necessary to determine whether prosthesis lift-off occurs in the replaced knee with slight lateral laxity similar to that in the normal knee.

Adult↗
PubMed2004

Anatomical analysis of the femoral condyle in normal and osteoarthritic knees.

It is important to understand anatomical feature of the distal femoral condyle for treatment of osteoarthritic knees. Detailed measurement of the femoral condyle geometry, however, has not been available in osteoarthritic knees including valgus deformity. This study evaluated femoral condyle geometry in 30 normal knees, 30 osteoarthritic knees with varus deformity, and 30 osteoarthritic knees with valgus deformity using radiographs and magnetic resonance imaging (MRI). In radiographic analysis in the coronal plane, the femoral joint angle (lateral angle between the femoral anatomic axis and a tangent to femoral condyles) was 83.3 degrees in the normal knees, 83.8 degrees in the varus knees, and 80.7 degrees in the valgus knees. In MRI analysis in the axial plane, the posterior condylar tangent showed 6.4 degrees of internal rotation relative to the transepicondylar axis in the normal knees, 6.1 degrees in the varus knees, and 11.5 degrees in the valgus knees. These results suggested that there was no hypoplasia of the medial condyle in the varus knees, but the lateral condyle in the valgus knees was severely distorted. Surgeons should take this deformity of the lateral femoral condyle into account when total knee arthroplasty is performed for a valgus knee.

Aged↗
PubMed2004

The oblique posterior femoral condylar radiographic view following total knee arthroplasty.

BACKGROUND: It is often difficult to evaluate the posterior aspects of the femoral condyles after total knee arthroplasty. We have developed an imaging technique involving the use of the oblique posterior condylar view for the evaluation of the posterior aspects of the femoral condyles. The purpose of the present study was to compare the efficacy of this view with that of the true-lateral view. METHODS: Three orthopaedic surgeons analyzed fifty-five sets of radiographs (consisting of oblique posterior condylar and true-lateral views) for patients who had undergone total knee arthroplasty. The accuracy and reproducibility of the oblique posterior condylar view for the detection of radiolucencies were compared with those of the true-lateral view. RESULTS: The oblique posterior condylar view was significantly better than the true-lateral view for the detection of radiolucencies of the posterior aspects of the femoral condyles (p < 0.0005). CONCLUSIONS: Radiographic analysis with use of the oblique posterior condylar view is technically easy and is accurate for the evaluation of radiolucencies of the posterior aspects of the femoral condyles after total knee arthroplasty.

Aged↗
PubMed2004

[Bone quantity and quality to its mechanical integrity].

Bone strength is made up of quantity (mass, mineralization), geometry (anatomy, micro architecture, collagen structure), and turnover/damage accumulation. While most of the mechanical behavior can be explained by measures of porosity, several additional descriptors of the geometry have been proposed for better predictions of fracture risk. This review introduces various aspects of these relationships between bone quantity and quality to its mechanical integrity.

Biomechanical Phenomena↗
PubMed2003

Mechanical effects of the intraarticular administration of high molecular weight hyaluronic acid plus phospholipid on synovial joint lubrication and prevention of articular cartilage degeneration in experimental osteoarthritis.

OBJECTIVE: To examine in vivo the effects of a mixture of high molecular weight hyaluronic acid (HA) plus phospholipids on joint lubrication and articular cartilage degeneration. METHODS: Experimental osteoarthritis (OA) of the right knee was induced by anterior cruciate and medial collateral ligament transection in 40 rabbits. The animals were subjected to 8 consecutive weekly intraarticular administrations of high molecular weight HA (the HA200 group), conventional molecular weight HA (the HA80 group), or high molecular weight HA plus L-delta dipalmitoyl phosphatidylcholine liposomes (the PHA group) and were killed 1 week after the final injection. The remaining transected right knees (the OA group) and randomly selected nontransected contralateral left knees (the control group) were collected simultaneously. Each group (n = 10) was divided into 2 equal subgroups, one of which was evaluated histologically while the other was subjected to a lubricating ability test using a pendulum friction tester. RESULTS: The injected knees had a tendency to demonstrate less damage to the articular cartilage compared with the OA group, and the histologic findings in all groups except for the PHA group differed significantly from the control group. There was a significant difference in the mean +/- SD friction coefficient between the control group (0.0100 +/- 0.00300) and the OA (0.0206 +/- 0.00649), HA200 (0.0190 +/- 0.00427), and HA80 (0.0177 +/- 0.00712) groups (P < 0.05 for each comparison), but not between the control group and the PHA group (0.0150 +/- 0.00330) (P = 0.15). CONCLUSION: To our knowledge, this is the first in vivo study to examine whether intraarticular injections of phospholipids influence joint lubrication by acting as a boundary lubricant, thus protecting articular cartilage from degenerative changes.

Animals↗
PubMed2003

Changes in anteroposterior stability following total knee arthroplasty.

This study evaluated the changes in anteroposterior stability at flexion and extension following posterior cruciate ligament (PCL)-retaining and PCL-substituting total knee arthroplasty (TKA), in comparison with normal knees. Altogether, 29 knees of 24 patients underwent either PCL-retaining ( n = 19) or PCL-substituting ( n = 10) TKA. Anteroposterior displacement was measured with a KT-2000 arthrometer preoperatively, 1 month after surgery, and again an average of 3 years after surgery. Anteroposterior stability at flexion and extension did not change following PCL-retaining TKA and was not significantly different from that of normal subjects, whereas anteroposterior stability increased following PCL-substituting TKA and was significantly greater than that of normal subjects an average of 3 years after surgery.

Adult↗
PubMed2003

A comparison of rotational landmarks in the distal femur and the tibial shaft.

The relationship among three anatomic landmarks and the mechanical axis of the tibia was evaluated using magnetic resonance imaging in 30 normal knees in 15 healthy volunteers. These three relationships are calculated for flexion and extension. The angles between the tibial mechanical axis and a line perpendicular to the surgical epicondylar axis, a line perpendicular to the clinical epicondylar axis, and the anteroposterior axis were 3.9 degrees varus, 0.6 degrees varus, and 0.2 degrees valgus, respectively. The mechanical axis of the femur was 3.0 degrees varus relative to the mechanical axis of the tibia. The results of the current study suggest that the surgical epicondylar axis rather than the clinical epicondylar axis or the anteroposterior axis can maintain a more predictable orientation with respect to the mechanical axis of the tibia when moving from flexion into extension.

Adult↗
PubMed2003

Alignment in total knee arthroplasty following failed high tibial osteotomy.

In total knee arthroplasty (TKA) following failed high tibial osteotomy, the mechanical axis does not intersect the center of the tibial component if the tibia has been resected perpendicular to the anatomical axis. Therefore, tibial resection referencing the predicted postoperative mechanical axis instead of the tibial shaft axis is advocated. To obtain the optimal tibial resection, characteristics of the tibial proximal deformity were measured radiographically and predicted postoperative lower limb alignment was calculated using full-length, weight-bearing, lower limb anteroposterior radiographs. Two finite element analysis models also were examined. The proximal tibia was resected perpendicular to the tibial shaft axis in model 1, and perpendicular to the predicted postoperative tibial mechanical axis in model 2. When the proximal tibia was resected perpendicular to the tibial shaft axis, the predicted lower limb mechanical axis was significantly shifted medially to the center of the tibial joint surface. The results of the finite element analysis reflected the medial shift of the lower limb mechanical axis in model 1, where stresses were increased in the medial tibial compartment. Tibial resection referencing the predicted postoperative tibial mechanical axis, instead of the tibial shaft axis, should be performed, especially in cases with a deformed tibia.

Aged↗
PubMed2002

Prediction of total knee arthroplasty polyethylene wear using the wear index.

The predictive value of the wear index for total knee arthroplasty polyethylene wear was determined using a numeric and in vitro model. The wear index was defined as the deformation x the sliding velocity. Four commercially available total knee prostheses were modeled for this study. Deformation and sliding velocity were calculated from the 3-dimensional geometry of the components and the gait kinematic inputs using Hertz's formula. A knee simulation test was performed under the same conditions, and the surface of the inserts was compared with the wear index. This study showed good agreement between the numeric model and the simulation test, suggesting that the wear index is a reliable predictor of total knee arthroplasty polyethylene wear through its incorporation of contact stress and kinematics.

Arthroplasty, Replacement, Hip↗
PubMed2002

Factors affecting patellar tracking after total knee arthroplasty.

This study examined factors that influence patellar tracking after total knee arthroplasty. A total of 62 knees were evaluated radiographically for postoperative patellar tracking. Six factors were examined regarding their influence on postoperative patellar tracking. This study showed the effects of patellar component position, patellar resection angle, and lateral retinacular release on postoperative patellar tracking. There was no significant effect of the remaining 3 factors: the thickness of the patellar resection, preoperative patellar tilt, and rotational alignment of the femoral component. A medialized patellar component and obliquity of resection of the patella are effective for obtaining proper patellar tracking, whereas the evaluation of the influence of the external rotation of the femoral component requires more clinical studies.

Adult↗