Search

A 37-year-old woman entered our hospital because of bilateral knee pain. Tc-99m HMDP bone scintigram demonstrated increased activity in the bilateral patellae and cold lesion in the center and left lateral segments of the left patellae, so-called doughnut pattern. Trephine biopsy was performed to prove bilateral idiopathic asepct osteonecrosis of the patellae. The knee pain subsided and a bone scan 5 months later demonstrated increased activity in the bilateral patellae more widely than initial scan. We report the usefulness of Tc-99m HMDP bone scintigraphy to observe a reparative phase of idiopathic asepct osteonecrosis of the patellae.

In 119 young athletes (116 boys and 3 girls), 171 patellae partitae were reviewed. The incidence of patella partita was 20% in boys and 2.2% in girls involved in athletics, being significantly higher (37.1%) in boys between 8 to 10 years of age than in older boys. According to the radiographic study, most cases of patella partita developed before the age of 12 years and the lesion could heal spontaneously in the patients under 13 years of age: the lesion healed in 83.9% of the patients who stopped playing sports, or played less strenuously, but in only 33.2% of those who continued playing as hard as before. From these results, patella partita is apparently caused by repeated stress on the marginal chondroosseous region of the developing patella and can heal spontaneously in growing children younger than 13 years in age.

Patella alta has so far been given attention with reference to the patellofemoral disorder. However, neither its morphological concept has been quite coherent yet nor its clinical significance has been fully understood. In order to clarify these points, the author made a roentgenographic investigation of patella alta and also conducted an experimental study. Defining as patella alta the condition in which the articular surface of the patella is higher than the patellar surface on the femur, the author evaluated the patella position by seizing, from the dynamic viewpoint, the positions of the articular surface of the patella to the patellar surface on the femur by serial roentgenography and their graphic representations. The results obtained revealed that in the patellofemoral osteoarthritis, compared with the normal, there was observed retarded descending of the patella into the femoral intercondylar notch at knee flexion. Moreover, on the rabbit knee whose patellar ligament was lengthened, descending condition of the patella similar to that observed for human patellofemoral osteoarthritis was created, thus leading to an experimental patellofemoral osteoarthritis. The above results suggested an of important role of patella alta in the pathogenesis of patellofemoral osteoarthritis.

There are many theories concerning the etiology of chondromalacia patellae, as well as many points which have not been fully investigated yet. Using rabbits experimentally, shortening and elongation of the 3 mm patellar ligament were performed, producing the changes of contact surface and pressure on the patellar cartilage, and the patellar cartilage and the subchondral bone were studied sequentially. In the group of shortening, after the course of 16 weeks, no particular changes were recognized in the cartilage and the subchondral bone, compared with the control. In the group with elongation, 2-4 weeks after the operation, thinning of the trabecular and the subchondral bone, proliferation of blood vessels in the subchondral bone and their invasion into the calcified cartilage, were seen, without abnormality in the articular cartilage. After 4 weeks, irregularity or disappearance of the tide mark and degeneration of the ground substance toward the deep layer of the cartilage began to be recognized. After 8 weeks fasciculation was produced in the ground substance from the deep to the middle layers of the cartilage. After 12 weeks, degeneration extended to the superficial layer of the cartilage, producing blister formation, fibrillation and fissura, and finally proceeding to the desquamation of the superficial layer, degeneration and decrease in the thickness of the cartilage. These findings are similar to the histological findings of chondromalacia patellae, and seem to be different from those of arthrosis deformans in the bony changes. It is further suggested that decrease of contact surface and pressure on the cartilage can be considered to be one of the causes for chondromalacia patellae.

Fifty-eight patellae and femora of cadaveric knees were studied. Radiological measurement of the osseous projection and cartilaginous projection, aided by contrast medium, revealed several morphological characteristics of the patella and the facies patellaris of the femur as follows. Depth index, facet angle, facet ratio of the patella and median ridge index which indicates position of the median ridge, showed almost the same value as reported by many authors previously. There were configurational rules in the axial view and the lateral view of the patella. Imaging of the configuration of the articular surface of the patella was therefore possible when osseous projection was measured. Regardless of the positioning to take radiograph, depth index and sulcus angle of the trochlea showed almost the same value, but the facet ratio varied considerably. There were good correlations between facet angle of the patella and sulcus angle of the trochlea both in osseous and cartilagenous projections. The depth index and facet ratio, on the other hand, were shown to have correlation in cartilagenous projection only.