Kozo Sagara

Idiopathic necrosis of the femoral epiphyseal nucleus in rats.

To study the cause of osteonecrosis of the femoral head in spontaneously hypertensive rats, the site and mechanism of the occlusion of the blood vessels feeding the femoral head were investigated histologically and microangiographically. Tracing the blood vessels using serial sections revealed that the lateral epiphyseal vessels disappeared immediately before entry into the ossific nucleus. As the reparative process advanced, the blood vessels from the lateral side of the head entered the ossific nucleus again. To investigate the relationship between osteonecrosis and mechanical stress on the femoral head, some treatments to reduce mechanical stress were applied, and the frequency of the femoral head lesions, such as osteonecrosis, disturbed ossification, and abnormality of the growth plate, was compared among the groups of treatments for stress relief. The incidence of femoral head lesions was found to be directly proportional to the mechanical stress working on the area, as was evident from a decrease in the incidence of osteonecrosis as a result of reduction of mechanical stress. Thus, the obstruction of the vessels in the lateral part of the femoral head might result from the breakdown of cartilage caused by the mechanical stress on the femoral head.

Necrosis of the femoral head in growing rats Occlusion of lateral epiphyseal vessels

The cause of the vascular occlusion in necrosis of the femoral head of growing, spontaneously hypertensive rats was investigated histologically using serial sections. The lateral epiphyseal vessels, which supply the proximal femoral epiphysis, disappeared immediately before entry into the femoral heads. In fresh osteonecrosis the pathway of the vessels between the margin of the articular cartilage and the growth plate was replaced with granulation or scar tissue. We conclude that the vascular occlusion occurs in the layer of the epiphyseal cartilage where the lateral epiphyseal vessels penetrate, and that the abnormalities of the epiphyseal cartilage might play a part in the occurrence of osteonecrosis.

Results of Surgical Treatment for Ossification of the Yellow Ligament of the Thoracic Spine

Some patients with ossification of the yellow ligament of the thoracic spine (OYL) have been reported as achieving poor results following surgery. We investigated the factors affecting postoperative prognosis of OYL in our cases.Since 1984, ten patients with OYL have been operated in our hospital. Nine were available for follow-up. Four were male and five were female. The age at operation ranged from 34 to 77 years (mean age 58.4 years). Average symptomatic period prior to surgery was 22 months. The JOA score improved from a mean of 4.6 pre-operatively to 7.6 after surgery. Patients who were either elderly or had a long period of symptoms tended to achieve poorer results after surgery. Severe stenosis on CT (or CTM) and combined OPLL of cervical or thoracic spine seemed to influence their prognosis to some degree.

Treatment of Bilateral Fractures of Lower Extremities

We reviewed the treatment of ten patients with bilateral long bone fractures of lower extremities. Six patients had bilateral leg fractures. 2 patients had a leg fracture and a contralateral femoral fracture and 2 patients had bilateral femoral fractures. Seventeen fractures were treated operatively and three conservatively. The average period from surgery to P. W. B. (Partial Weight Bearing) was 85.6 days in comminuted fractures and 38.6 days in non-comminuted fractures. Intra-articular fractures of the ankle which included three comminuted fractures needed 84.0 days before P. W. B and bilateral femoral fractures needed 78.0 days on average. Fractures of the upper extremity and foot affected the starting time of P. W. B.. The average period from P. W. B. to Full Weight Bearing was 45.6 days in comminuted fractures and 17.6 days in non-comminuted fractures. From this study we think that other associated fractures, comminuted fractures and bilateral femoral fractures cause delay in post-operative treatment. For these fractures, nonweight-bearing braces are effective and it is better to use intra-medullary nailing in order to allow P. W. B. earlier.