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Biomedical subjects

H G Willert

Publications and source records attributed to H G Willert.

At least 73 records · Page 4Linked to original sources
PubMed1976

Animal studies on bone ingrowth kinetics of ceramic material under dynamic stress.

Two of the primary problems of implants in use today result from the materials used in their construction (metal and polyethylene) and from the necessary additional fixation with bone cement. In order to alleviate these well known difficulties, we studied ceramic material (99.7% Al2O3 with 0.25% MgO) which exhibits several advantages in these areas, but has a diminished bending strength. To take advantage of the ceramic material, we tested a cement-free implantation which should allow unhindered growth of bone tissue to or into the material. In particular, the interface relationship under load bearing was investigated. The course of the tissue differentiation and ingrowth on the surface of the ceramic implants under dynamic stress, was studied by a specifically disegned distance-spacer. These were tested on the femur of foxhounds and sheep, as well as by use of temporary immobilization. Histological investigations in intervals of 4 weeks showed the course of the development of the interface tissue. After removal of the binding materials, the behavior of the implant support is studied in 4-week intervals with free load bearing. Radiological and histological development studies are shown. The results we obtained implicate the use of ceremic impants. But the application in humans still seems to be problematic, as there is a need for designs which are loaded by pressure only.

Aluminum↗
PubMed1975

Osteosarcoma in children. A study of 125 cases.

A study is presented of the aetiology and results of treatment in a group of 125 proven osteosarcomas present in children under fifteen years of age. These cases have been collected from the records of one English and six European treatment centres. There is a slight male preponderance, but the striking aetiological feature is the very high proportion of tumours of the long bones of the limbs (96 per cent). The two and a half and five year disease-free survival rates were respectively 15 and 12 per cent, with a further 9 per cent still living, but under observation for less than two and a half years. Evidence of metastasis after two and a half years is very unusual, but no child with a tumour of an axial or girdle bone lived this length of time. Although the differences in the results of the different methods of treatment employed are not statistically valid, the largest number of long survivors had been treated by early amputation, which method also provided the lowest rate of local tumour recurrences. Reasons are discussed which indicate that prompt ablation is the treatment of choice, perhaps with certain advantages in the light of recent advances in adjuvant treatment. The past situation in connection with childhood osteosarcoma certainly provides strong support for immediate carefully designed clinical trials of the new adjuvant methods cited.

Age Factors↗
PubMed1975

[Treatment of segmental ischemic necroses of the head of femur with intertrochanteric flexion-osteotomy (author's transl)].

We call conditions with focal necroses in the head of femur "segmental necroses". Where possible we prefer to treat this condition with intertrochanteric displacement osteotomy, either with flexion- or varus displacement. As with arthrosis of the hip-joint the effects of displacement osteotomy are: reduction of tension of the muscles acting on the joint and increase in the leverage of the abductors reduce the work-load of the joint. An intact sector of the femoral head is placed into the weightbearing position and the necrotic segment is relieved. Immediate freedom from pain is supposed to be due to a normalization of the internal pressure in the marrow-cavity. For radiologic examination of segmental necroses of the femoral head tangential films (after Schneider) in addition to AP and axial films have proved useful. Early results of 16 flexion osteotomies for segmental necrosis of the head of femur, followed up for 6-34 months after operation (and further for up to 54 months), are encouraging. Impressive improvement of pain occurred in 14, of gait in 11 patients. The range of movement of the diseased joints, however, was not essentially increased.

Adult↗