Yoshikatsu Kuroki

Role of Impairment of Blood Supply of the Femoral Head in the Pathogenesis of Idiopathic Osteonecrosis

To investigate the role of blood supply in the pathogenesis of idiopathic osteonecrosis of the femoral head, superselective angiography of the medial circumflex artery was performed. Sixteen hips with early stage osteonecrosis diagnosed by bone scintigraphy were studied, as were 22 contralateral normal hips (from unilateral cases) and 22 roentgenographically and scintigraphically normal hips in patients who had been administered corticosteroids. All hips demonstrated abnormal superior retinacular arteries in the extraosseous area, and small arteries penetrated 14 hips with early stage osteonecrosis. Abnormal findings were noted in 17 of 22 contralateral normal hips and in 20 of 22 normal hips with corticosteroid administration. Follow-up roentgenographic analysis showed that the hips with small arterial penetration most often developed osteonecrosis. There were two important findings: (1) The blood supply of the superior retinacular arteries from the extraosseous site was impaired. (2) Revascularization was observed not only in hips with early stage osteonecrosis but also in contralateral normal hips and normal hips with corticosteroid therapy. Osteonecrosis is not necessarily a consequence of a single episode of impairment of blood supply of the femoral head but that of a repetitive episode if interruption of revascularization.

Femoral deformity in adults with developmental hip dysplasia.

Quantitative computed tomography and 3 dimensional modeling were used to portray the deformity of the proximal femur in 24 Japanese adults with low subluxations to high dislocations secondary to developmental dysplasia of the hip. Periosteal and canal bony contours were extracted, 3 dimensional models generated, and morphologic parameters were calculated for each femur. Three dimensional illustrations of the average deformity and variability were created. Morphologic parameters were not found to be statistically correlated with the degree of the disease. Interestingly, the major axis of the canal contours of the proximal femur was found to be aligned with the plane of the femoral neck (anteversion), regardless of the degree of anteversion. Thus, the amount of version correctable in an uncemented prosthesis is limited, and at times may require a special prosthesis, overreaming, undersizing and cementing, or an osteotomy. Additionally, the proximal medial curvature of the dysplastic femurs was straighter than that of normal femurs. This necessitated a corresponding reduction in the proximal medial curvature of a conventional uncemented prosthesis to match the medial curvature of the individual femur and the average developmentally dysplastic femur. This objective description of the developmentally dysplastic femur corroborates clinical observations, highlights some unrecognized findings, provides a rationale for planning reconstructions, and aids in the design of prostheses for adult patients with this deformity.

Modified Sugioka's osteotomy : More than 130° posterior rotation for osteonecrosis of the femoral head with large lesion

High degree posterior rotational osteotomy was performed on 31 hips with extensive osteonecrosis that were outside of Sugiokas indication. Among them, 18 hips of 13 patients were reviewed at 24 to 94 months (mean, 42 months). The remaining 13 hips were excluded because the followup was less than 2 years. All hips had less than 1/3 of the posterior area intact preoperatively, which is out of the indication for traditional anterior rotational osteotomy. The posterior rotation applied to the femoral head was 130° to 180° (mean, 138°). Furthermore, 10° to 25° of intentional varus position was added to the rotation (mean, 15.80°). The preoperative intact articular surface of the loaded portion of the femoral head was 0% to 40% (mean, 6.9%) on anteroposterior radiograph, and it was extended postoperatively to a mean of 80.3% (range, 53%-100%). Collapse was prevented in 17 hips that have remained pain free. The remaining 1 hip sustained secondary collapse and joint narrowing. Mean flexion was 105° and abduction was 20°. Postoperative angiography of 9 hips and bony scintigraphy of 17 hips indicated no findings implying impairment of blood supply. Despite a relatively short term experience, it is concluded that this technique was effective in the treatment of large necrotic lesions, especially for young patients.

FEMORAL COMPONENT WEAR IN RETRIEVED HIP PROSTHESES

We retrieved 159 femoral heads at revision surgery to determine changes in surface configuration. Macroscopic wear of the head was observed in three bipolar hip prostheses as a result of three-body wear. There was a considerable change in surface roughness in the internal articulation of bipolar hip prostheses. Roughness in alumina heads was almost the same as that in new cobalt-chromium heads. The annual linear wear rate of polyethylene cups with alumina heads was less than that of cups with cobalt-chromium alloy heads. Polyethylene wear was increased in the prostheses which had increased roughness of the head.

Efficacy of Lateral Retinacular Release for Painful Bipartite Patella

We treated painful bipartite patella with a modified lateral retinacular release technique in 15 patients (16 knees). Bony union of the separated fragment and the patella was obtained in 15 of 16 knees within 8 months of surgery. Sustained traction acting on the patella laterally and proximally is presumed to cause the pain. The surgical technique to reduce this force proved effective not only in relieving the pain but also in achieving bony union. Painful bipartite patella can lead to excessive lateral pressure syndrome or pa tellar compression syndrome, these complications can be effectively treated by this surgical technique. In contrast to conventional treatments, such as ex cision of smaller fragments or osteosynthesis to achieve bony union, the modified lateral retinacular release technique is easy to perform and provides an effective means for relieving patellofemoral pain and achieving bony union.

A microangiographic study of idiopathic osteonecrosis of the femoral head.

Microangiography was performed on 31 femoral heads with idiopathic osteonecrosis to investigate the pathogenesis of this disease from the aspect of circulation disturbance. Microangiography showed the following: (1) the interruption of the superior retinacular arteries in the extraosseous area; (2) the presence of numerous newly formed vessels of varying diameter arising from the stumps of the interrupted superior retinacular arteries; (3) compensatory hypertrophy and large-area invasion of the inferior retinacular arteries and the ligamentum teres arteries, both of which medially enter the affected head; and (4) the blockage of revascularization, which occurred along the area of subchondral fracture and collapse at the weight-bearing region. These findings strongly suggest that revascularization is aborted by the subchondral fracture and collapse caused by weight bearing. It was assumed that interference with revascularization occurred repeatedly in the repair process of affected heads due to the influence of subchondral fracture and collapse caused by weight bearing.

Wear of bipolar hip prostheses

A method was developed to take radiographs showing the inner articulation of bipolar hip prostheses. By this method, wear was measured in 68 hips whose inner head diameter was 22 mm. Average annual wear rate was 0.17 mm. Osteolysis was observed in 25 hips (37%) and there was no difference between the annual wear rate of hips with and without osteolysis. Studying 19 retrieved prostheses, abrasion of the rim was deeper in hips with osteolysis than those without it. Wear rate of the inner articulation in bipolar hip prosthesis is much larger than that in Charnleys prosthesis, as linear penetration into the articulation surface reduces the motion range of the inner articulation and this increases impingement and advances rim abrasion.

Osteochondritis dissecans of the patellofemoral groove in athletes: unusual cases of patellofemoral pain.

Five athletes who developed osteochondritis dissecans in the patellofemoral groove in the course of sports events at high school and college league level are described. They were male athletes complaining of anterior knee pain. When examining young people engaged in violent sports, it is well to remember that they might have osteochondritis dissecans in the patellofemoral groove. Clinically, four of the five patients under discussion were characterized by tight movements of the patella in a direction parallel to its transversal axis. X-ray studies in lateral projections and CT scans provided useful tools for definitive diagnosis, but AP radiography was no help in diagnosis. Release of a tight lateral retinaculum with or without drilling on the degenerated cartilage was effective in the treatment of osteochondritis dissecans of the patellofemoral groove in three of the four patients.

Clinical and histological study of patellar chondropathy in adolescents

An arthroscopic and histological investigation of patellar chondropathy in adolescents was performed in 98 knees of 83 patients who were classified into three clinical types of patellofemoral disorder. These were the anterior knee pain syndrome, idiopathic chondropathy, and unstable patella. Histological findings suggested little evidence of progression to high-grade chondropathy in the patients with anterior knee pain syndrome, and this may account for the resolution of clinical symptoms in this group. Even in patients with high-grade lesions in the idiopathic chondropathy and unstable patella groups, histological observations indicated that these lesions could heal either by intrinsic (fibrous metaplasia of chondrocytes and regeneration of matrix) or extrinsic repair. Chondropathy in adolescents may be similar to the early changes of osteoarthritis of the knee. However, chondropathy shows far more potential for repair by the synovium and/or the cartilage itself than does osteoarthritis.

A scanning electron microscopic study of the degenerative cartilage in patellar chondropathy.

Patellar chondropathy as cartilage degeneration localized in patellar cartilage in young persons is characterized by cartilaginous changes, such as softening, swelling, and fissuring. With a view to structural characterization of early cartilaginous degeneration before erosion, the morphology of affected cartilage was studied under a scanning electron microscope. The surface network of cartilage constituting fibrils had an edematous change, presenting with fibrillation on the medial facet, whereas many fibrils of the central ridge had a collagen bundle, and fissuring of varying size was observed. It appeared that a mechanical force (shearing) acting on the site of the central ridge was associated with the formation of a collagen bundle and its destruction. On the lateral facet, fibrils were arranged perpendicular to the joint surface; the superficial layer of fibrils was worn by hyper-pressure acting on the lateral facet. On the fractured surface, the coarseness of collagen fibrils showed changes that varied with the site and stage of cartilage degeneration. Frequent changes were signs of fibril loosening (coarsening), such as reduction in fibril density (i.e., edematous change), collagen fibril aggregation, and fissuring, and longitudinal restructuring of fibrils. The patellar cartilage in the patients of this series showed a structure adapted to the mechanical force. The initial structural changes of cartilage consisted of collagen fibril aggregation and reduction in fibril density. These changes give rise to matrix rarefaction, which in turn causes cartilage degeneration to progress. These changes were concurrent in both the superficial and middle layers and were not localized as basal degeneration.