Bone Collapse Research Articles

Failure of total knee arthroplasty due to loosening and deformation of the tibial component.

A series of 100 consecutive UCI knee replacements showed a 7 per cent incidence of reoperation due to loosening of the prosthesis associated with permanent deformation of the tibial component. Analysis of the clinical data, roentgenograms, and removed implants showed associations between failure and radiolucency at the cement-bone interface, prosthetic obliquity, collapse of trabecular bone, change of the alignment of the extremity, and permanent deformation of the tibial component. Although no one of these factors by itself can be responsible for the mechanical failure of the arthroplasty, a predominant failure pattern exists. We think that the sequence of events is as follows: implantation of the tibial component with medial or lateral tilt; lack of firm skeletal stabilization; continual microtrabecular fractures; change in alignment of the extremity; and permanent deformation of the plastic component.

Postyield behavior of subchondral trabecular bone

Cylindrical specimens of bovine subchondral trabecular bone were tested to uniaxial compressive strain levels of 75% to study energy absorption during pore collapse. Stress-strain curves were characterized by macroscopic yield at about 8% strain followed by a significant horizontal pore collapse regime. Energy absorption occurred largely in this postyield regime. Yield strength and energy absorption capacity were found to increase linearly with specimen apparent density. Microstructural analysis of the deformed specimens verfied that the mechanism for energy absorption was primarily fracture and buckling of trabeculae. The results suggest that during fracture, the collapse of trabecular bone (and the consequent absorption of energy) serves to attenuate stresses transmitted through the skeleton and thus protect vital structures such as the brain.

The lesions of congenital syphilis.

The clinical and radiological presentation of 108 cases of prenatal or congenital syphilis from a ten-year survey are reviewed. Part I deals with 102 cases of early syphilis aged from one day to six months. The bony presentations are reviewed and the relative incidence of the varying appearances stated. Histology was obtained on four cases. This did not show any specific inflammatory change. The changes are thought to be due to growth disturbance, incomplete bone formation and collapse at the growing ends of the bones. In view of the dystrophic origin rather than inflammatory origin, it is suggested that the nomenclature be reviewed. A prospective pathological study is in progress and two further autopsies have shown no inflammatory skeletal lesion. Part II deals with the late inflammatory changes which occurred. These were six cases which consisted of sabre tibiae, arthropathies and gumma. No explanation for the distribution of the lesions can be given.

THE RESULTS OF OSTEOTOMY FOR EARLY PRIMARY OSTEOARTHRITIS OF THE HIP

1. The clinical and radiological results of seventy-one osteotomies for primary osteoarthritis of the hip performed with internal fixation have been examined two to eight years after operation. Advanced cases where osteotomy would have been purely a salvage procedure were excluded. 2. The hips were divided into two groups: one in a relatively early and the other in a later intermediate stage of the disease. The two criteria for inclusion in the "early" group were a) fiexion movement of 90 degrees or more, either with the patient conscious or completely relaxed under anaesthesia, and b) no collapse of bone seen in the radiograph. 3. The clinical results show that early osteotomy seldom fails to give relief of pain, which is closely correlated with improved function and a favourable assessment of the operation by the patient. A good range of flexion, not less than 70 degrees and frequently 90 degrees, is retained when the criteria mentioned above obtain. 4. The radiological assessment was based upon examination of the joint space, the cystic appearances and the degree of collapse of bone, if any, as seen in serial films. There was convincing evidence of regression indicating arrest of the arthritic process in 70 per cent of the "early" cases. 5. Regression after osteotomy appears to be a well-defined process which is more commonly observed and more complete when the osteotomy is performed sooner rather than at a later stage of the disease. With few exceptions a good radiological result is associated with a good clinical result. 6. Some of the possible causes of failure are discussed. Osteotomy is more likely to fail if delayed till stiffness is severe and collapse of bone has begun. Large cysts, rapid advance of the disease, and a valgus osteotomy in the presence of lateral subluxation may also prejudice the results. 7. This review offers good support for Nissen's suggestion that in primary osteoarthritis of the hip osteotomy should be performed early, while the joint is still mobile and capable of repair, in order to retain good function. 8. Relief from pain is not the only consideration in deciding when to operate; the prospects of arresting the disease and of stimulating a healing reaction in the disordered cancellous bone and articular cartilage by early osteotomy should always be kept in mind. 9. In many respects the findings of this review are complementary to those of Postel and Vaillant (1962) who reported excellent results from varus osteotomy of Pauwels' type in a series of cases of subluxation of the hip with pain but without frank secondary osteoarthritic change.