Degenerative osteoarthritis after Perthes' disease: a 36-year follow-up.

BACKGROUND: Although the prognosis of Perthes' disease at skeletal maturity is considered favorable, little is known about the long-term results after middle age. METHODS: We retrospectively analyzed the radiographic and functional outcomes of 67 patients (70 hips) who had been treated for Perthes' disease. Of these patients, 28 patients (29 hips) were evaluated using JOA (Japanese Orthopaedic Association) score and radiographs at follow-up (Group 1), 39 patients (41 hips) were evaluated by a postal questionnaire (Group 2). The mean follow-up period was 36.1 years. The mean age at follow-up was 43.1 years. RESULTS: Group 1, good radiographic results (Stulberg class I or II) were achieved in 59% of hips. No osteoarthritis (Tönnis Grade 0) was observed in only 48% of hips. The clinical results were good (JOA score ≥ 70) in 79% of hips. Disturbance of walking ability and activities of daily living was little. The Tönnis grade and JOA score declined after 40 years of age. All patients older than 50 years showed severe osteoarthritis. The severity of osteoarthritis correlated significantly with age at follow-up. Group 2, the clinical results were good (JOA score ≥ 56) in 76% of hips. In both groups, no patient had undergone total hip arthroplasty. Younger age at diagnosis (<8 years) correlated significantly with a better result. The JOA score correlated significantly with age at follow-up. CONCLUSION: Patients who were treated for Perthes' disease have a risk of osteoarthritis and a clinically poor outcome after the age of 40-50 years.

Deep flexion-oriented bisurface-type knee joint and its tibial rotation that attributes its high performance of flexion.

In 1989, we developed an artificial knee prosthesis that could accommodate the oriental lifestyle where people would sit more often on the floor than on a chair. The knee had a bisurface feature with an auxiliary joint of a ball and socket at the center of the posterior part aiming at an improved flexional function. The auxiliary joint functions not only to facilitate a rollback movement but also to add a rotational movement. It was investigated whether this knee prosthesis could show an internal rotation of the tibia during flexion such as the physiologic movement of the knee. The internal rotation of the tibia was evaluated for the patients who could sit on legs in the oriental style after total knee arthroplasty. The average flexion angle of patients who achieved this style of sitting was 144.1°, and the average internal rotation was estimated as 14.3° by a pattern matching method using a computer-assisted design system.

The Bi-Surface total knee arthroplasty: minimum 10-year follow-up study.

The Bi-Surface Knee System (Japan Medical Material, Kyoto, Japan), which has a unique ball-and-socket joint and whose femoral component is made from alumina ceramic, was designed to improve deep knee flexion and long-term durability after total knee arthroplasty. The purpose of this study was to review the clinical results of a minimum 10-year follow-up. Between 1989 and 1997, 507 total knee arthroplasties were carried out in 371 patients. Forty three patients (56 knees) were lost to follow-up. The mean age of the patients at operation was 68.5 years, and the patients were followed up for a mean of 11.7 years. The knees were evaluated on the basis of Knee Society knee score and functional score, radiographs, and Kaplan-Meier survivorship analysis. The knee score was improved from 38.9+/-17.4 points preoperatively to 93.3+/-7.8 points at the latest follow-up (p<0.001). The functional score was improved from 34.9+/-19.3 points to 52.7+/-24.1 points (p<0.001). The mean range of flexion was improved from 118.7+/-21.7 degrees to 124.2+/-20.8 degrees (p<0.001). The critical angle, which means the border to gain more range of flexion postoperatively, was 130.1 degrees. Kaplan-Meier survivorship at 10-year was 95.9% with any operation or radiographic failure as the end point. The corresponding rate was 97.4% with revision of any component as the end point. No ceramic component fracture occurred. The present study demonstrates that good range of flexion was maintained for a long time after total knee arthroplasty with excellent durability. The Bi-Surface Knee System appears to have achieved its design objectives.

A new plain radiography method using the optimal angle of knee flexion for assessing early degeneration of the knee joint.

During total knee arthroplasty for primary osteoarthritis, we measured the area of worn cartilage on the medial femoral condyle in 44 knees. By reference to a lateral femoral radiograph of each knee, the optimal knee flexion angle-reflecting the worn area of the femoral condyle-was determined and found to be 19.8 degrees +/- 7.6 degrees. Using this result, a new method for posteroanterior radiography of the weight-bearing knee (20/10 radiography) was devised. We compared the use of our method with Rosenberg's method in 56 varus knees and found that the width of the cartilage space determined by our method was narrower than that determined by Rosenberg's method (t test, <0.001). These results confirmed that 20/10 radiography well reflects the region of worn cartilage in knees with early-stage primary osteoarthritis.

A mechanical comparison of 2 posterior-stabilizing designs: Insall/Burstein 2 knee and Bisurface knee.

A posterior-stabilizing knee prosthesis, called the Bisurface knee (Kyocera Corp, Kyoto, Japan), with a ball-and-socket joint installed in the midposterior portion of the tibiofemoral joint, has been developed to satisfy 2 conflicting demands in knee joint design: kinematics and wear resistance. To confirm if the prosthesis has achieved its design objectives, a contact area and stress study was done throughout the range of motion and compared with results obtained for the Insall-Burstein 2 knee. The posterior-stabilizing ability of the ball-and-socket joint also was assessed. This study showed that the ball-and-socket joint could provide sufficient posterior stability, earlier start of flexion, and lower contact stress in the tibial polyethylene insert in flexion. The design of the Bisurface knee could provide a good balance between kinematics, stability, and wear resistance.