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Biomedical subjects

K Knahr

Publications and source records attributed to K Knahr.

At least 37 records · Page 2Linked to original sources
PubMed1994

Ten-year results of cemented Weller-type total hip arthroplasties. Analysis using different definitions of failure.

The first 100 consecutive cemented Weller-type total hip arthroplasties carried out between 1976 and 1977 were reexamined. Clinical analysis of 43 implants with more than 10 years follow-up showed that results were excellent in 21 patients (49%), good in 13 (30%), fair in 7 (16%) and poor in 2 (5%). Radiographic analysis revealed 33 (87%) stable femoral and 31 (81%) stable acetabular components. Statistical survivorship analysis of all 100 implants produced a probability of reoperation of 6.2%, a probability of radiographic implant loosening of 28.2% and a probability of radiographic loosening with clinical symptoms of 7.6%. The definition of failure should be "radiographic loosening of the prosthesis with clinical symptoms" because this evaluation seems to have the best clinical relevance. Concerning the fact that the cement fixation was not performed to today's standard, the results after more than 10 years with this total hip system (Weller long stem) are sufficient.

Adult↗
PubMed1994

Long-term results of uncemented alumina acetabular implants.

We report the clinical and tribological performance of 67 ceramic acetabular prostheses implanted between 1976 and 1979 without bone cement. They articulated with ceramic femoral heads mounted on mental femoral stems. After a mean elapsed period of 144 months, 59 sockets were radiographically stable but two showed early signs and six showed late signs of loosening. Four of the loose sockets have been revised. Histological analysis of the retrieved tissue showed a fibrous membrane around all the implants, with fibrocartilage in some. There was no bone ingrowth, and the fibrous membrane was up to 6 mm thick and infiltrated with lymphocytes, plasma cells, and macrophages. Intra- and extracellular birefringent wear particles were seen. Tribological analysis showed total wear rates in two retrieved alumina-on-alumina joints of 2.6 microns per year in a stable implant and 68 microns in a loose implant. Survival analysis showed a revision rate of 12.4% at 136 months.

Adult↗
PubMed1991

Rotationplasty for limb salvage in the treatment of malignant tumors at the knee. A follow-up study of seventy patients.

Seventy patients who had a rotationplasty for treatment of a malignant tumor in the region of the knee (the femur or the tibia) between 1974 and 1987 were followed for two to thirteen years (mean duration of follow-up, four years). Forty-seven patients had a stage-IIB osteosarcoma; the remaining twenty-three patients had a malignant fibrous histiocytoma, a chondrosarcoma, a Ewing sarcoma, or a giant-cell tumor. The most severe postoperative complication was occlusion of the reanastomosed vessels (seven patients), leading to amputation proximal to the knee in three patients. Other complications were problems with wound-healing (eight patients), transient nerve palsy (five patients), irreversible nerve palsy (two patients), pseudarthrosis (four patients), and rotational malalignment (one patient). Late complications included eight fractures, two infections, two delayed unions, and one lymphatic fistula. More than half of the patients were free of complications related to the operative procedure. Forty-four of the patients who had a stage-IIB osteosarcoma could be followed, and their data were analyzed for survival statistics. These patients had a 58 percent rate of disease-free survival and a 70 per cent rate of over-all survival. One patient had a local recurrence five years after the operation.

Adolescent↗
PubMed1990

A radiological analysis of uncemented PCA tibial implants with a follow-up period of 4-7 years.

A total of 63 uncemented PCA tibial implants were followed radiologically for a period of 4-7 years to establish whether primary fit, alignment, bone quality, age, and diagnosis have an effect on radiological results. Fifty-eight of the 63 tibial plateaus investigated (92%) showed excellent or good radiological results. In three cases the implant was rated radiologically endangered and in two cases radiologically loose. The results show that successful long-term anchorage depends principally on a primary stable fit. If implantation is inexact, poor bone quality, improper alignment, advanced age, and rheumatoid arthritis may be responsible for unsatisfactory radiological results. The authors conclude that particular importance must be attached to exact primary fixation when several unfavorable factors are encountered.

Aged↗
PubMed1988

Heterotopic ossification with total hip endoprostheses in various models of thrombosis prophylaxis.

The influence of thrombosis prophylaxis on the occurrence of heterotopic ossification after implantation of total hip endoprostheses was analyzed in a series of randomized studies. When low-dose heparin or dextran 40 was administered, the rate of ossification was comparatively high (30.1% and 65.1%). When a combination of acetylsalicylic acid and an antirheumatic (oxyphenbutazone) or low-dose heparin with an antirheumatic (indomethacin) was administered, the ossification rate became significantly lower (6.2% and 16.7%). No severe ossification (Arcq degree III) was observed in the groups given an antirheumatic in addition to thrombosis prophylaxis.

Aspirin↗
PubMed1987

Survival analysis of an uncemented ceramic acetabular component in total hip replacement.

Follow-up examinations of 67 implants of cement-free ceramic sockets show the need for an exact definition of failure, to warrant comparable evaluations of results. Statistical survival analysis offers the possibility of presenting both the incidence of failures and the dates of their occurrence. If only revision surgery with removal of the socket is considered to be a failure, our material shows the "survival quota" of the ceramic socket after 8 years to be 96.7% +/- 2.2%. If radiological signs of loosening are included in the evaluation of failures, the "survival quota" of the stable implants is reduced to 81.9% +/- 6.9%.

Acetabulum↗
PubMed1987

[Surgical tactics in malignant bone tumors].

In treating bone sarcomas two principles apply: 1) Oncologically radical removal of the tumor. 2) Maximum functional preservation and/or restoration of the extremity. Modern chemotherapy has clearly improved the prognosis for some sarcomas (e.g. osteosarcoma, Ewing's sarcoma), justifying even extensive surgery and lengthy rehabilitation. Primary malignant bone tumors are fairly rare. To optimize therapeutical results, supraregional and interdisciplinary treatment centers have to be established.

Bone Neoplasms↗
PubMed1983

The effect of prophylaxis for thrombosis on heterotopic ossification following total hip joint replacement.

The effect of prophylaxis for thrombosis on heterotopic ossification was investigated using 216 total hip joint endoprostheses implanted between 1976 and 1978. During this period a random comparative study of low dose heparin and oxyphenbutazone/acetylsalycilic acid was carried out. The rate of ossification in the 216 hip joints was 17.6%, and was about average for the values specified in literature on this subject. Heterotopic ossification occurred in 30.1% of the 103 hip joints treated with heparin, whilst the rate of ossification in the 113 hip joints treated with oxyphenbutazone/acetylsalycilic acid was only 6.2%. This represents a statistically significant difference in disfavour of prophylaxis with heparin.

Aspirin↗
PubMed1981

Treatment of osteosarcomata of the distal femur by rotation-plasty.

Rotation-plasty was carried out on fifteen patients--10 male and 5 female patients aged between 6 and 32--with an osteosarcoma of the distal femur following resection of the tumor. In the operation the lower leg was rotated through 180 degrees after resection of the distal femur and knee joint so that the ankle joint was effectively turned into a "knee joint". The indication for this operation was initially limited to children for whom the only possible therapeutic alternative was a high above-knee amputation. The surprisingly good functional rehabilitation justifies the indication of this method as an alternative to an endoprosthesis or arthrodesis even for young adults. In spite of the cosmetically very unusual position of the foot, none of the patients has so far experienced psychological problems thanks to suitable guidance. Both from an oncological and psychological point of view, this method represents an extremely responsible operation and should therefore only be carried out by hospital departments specializing in the therapy of bone tumors.

Adolescent↗
PubMed1981

Experience with bioceramic implants in orthopaedic surgery.

In the period from 1974 to March 1980 bioceramic endoprostheses were implanted in 155 patients. 94 patients were suffering from degenerative hip diseases and 61 had been operated for malignant bone tumours. The majority of the total endoprostheses consisted of a ceramic socket and a metal shaft prosthesis with ceramic head attached to it. Bioceramic double-cup prostheses were implanted in 19 patients without using bone cement. Following resection of malignant bone tumours, the proximal humerus and the proximal femur were replaced by special bioceramic endoprostheses. The post-operation period after implantation has reached 70 months in the case of tumour endoprostheses (average 22 months) and up to 49 months in the case of hip joint endoprostheses (average 24 months). The analysis deals exclusively with complications specific to the ceramic material. These complications are: breakage of the ceramic head (8 X), loosening of the ceramic cup (13 X) and pseudarthrosis of the cone connection in tumour endoprostheses (9 X). Abrasion particles were found in all cases which we were able to follow up histologically.

Aged↗
PubMed1981

[The cementless implantation of tumor endoprostheses (author's transl)].

Due to the improved prognosis of patients with primary malignant bone tumours, permanent attachment is also one of the problems encountered in the implantation of tumour endoprosthesis without bone cement, as surgeons are at present attempting to do in the case of conventional joint endoprostheses. The two methods which can be used for the cementless implantation of tumour endoprostheses are intramedullary stem fixation and extracortical attachment. Both methods require additional stabilisation by plates. Mechanical loading tests on 90 pairs of anatomical femurs showed that all the forms of attachment investigated exhibited adequate primary stability. However, it would appear necessary to fix two securing plates laterally and ventrally in order to achieve stable permanent attachment. The clinical results so far obtained with 18 cone endoprostheses and 12 stem endoprostheses are satisfactory. In the case of cone endoprostheses observed for an extended period after insertion, radiological checks showed the "incorporation" of the implant as an indication of stable permanent attachment. Radiological checks of patients with stem endoprostheses showed considerable structural movement in the area of the attachment. However, this did not result in signs of loosening so far. At the present time the cone attachment is preferable in view of the simpler operating technique involved and the more favourable radiological observations following the operation.

Adolescent↗
PubMed1979

A bioceramic endoprosthesis for the replacement of the proximal humerus.

In patients with malignant tumors in the region of the shoulder, radical resection can avoid amputation in most instances. To improve the function of the arm, endoprosthetic replacement of the defect is desirable. A three-component endoprosthesis made of a bioceramic material (aluminium oxide) was designed, implanted without bone cement. Fast anchorage to bone is achieved by using a conical sleeve, fixed upon the previously conically reamed humerus shaft. A stable primary fit is always feasible. Subsequent bone in growth into grooves inside the conical sleeve provides a permanent anchorage of the endoprosthesis. The authors experiences are based on implantations of 38 endoprostheses. The original diseases were primary malignant bone tumors in 19 patients, one case of "solitary" plasmocytoma and metastases into the proximal humerus in 16 patients. In two women, resection was made because of posttraumatic subcapital humeral pseudarthrosis. The follow-up study includes only those 27 cases operated on at least one year ago. 12 of the 14 patients with primary tumors have been surviving for 12-55 months (range 27.4) without signs of metastases or recurrent disease. Seven patients with metastases died of their original diseases after 7.7 months on the average. Owing to extensive resection of the shoulder musculature the mobility in the shoulder joint is considerably reduced. All the patients have good movement of the elbow joint and free function of the hand.

Activities of Daily Living↗
PubMed1979

[Disarticulation in the knee joint (author's transl)].

Based on the results with thirty patients, disarticulation in the knee is to be recommended as a very good amputation level. Two groups of patients seem to be especially suitable for this amputation level: patients with malignant bone tumors of the proximal tibia or fibula and patients with peripheral vascular diseases. Above all, the easy operational technique and the functionally valuable long thigh stump offer decisive advantages as compared with amputation of the thigh. Problems with prosthesis fitting were solved through modification of the socket shape as well as new developments in artificial knee joints.

Adolescent↗
PubMed1979

[Endoprosthetic replacement following resections of malignant tumors of the extremities (author's transl)].

Due to advances in chemotherapy and endoprothetics, amputation is increasingly being replaced by local resectioning in malignant tumors. While suitable implantations for bridging defects in the proximal humerus and proximal femur are available, prostheses for resectioned tumors in the knee area have not yet been fully developed. From 1966 to 1978, 77 endoprostheses were implanted in 29 primary bone tumors, 3 malignant soft-tissue tumors and 45 bone metastases. There were 43 endoprostheses of the proximal femur, 31 endoprostheses of the proximal humerus and 3 special endoprostheses of the knee region. In most cases, eliminating the tumor radically was successful and a functional extremity was retained.

Bone Neoplasms↗
PubMed1978

[Osteoid osteoma. (Plain films, angiography and scintigraphy in fifty patients) (author's transl)].

The radiological diagnosis and differential diagnosis of osteoid osteomas was considered in relation to a series of 50 histologically verified cases. In twenty, angiography had been performed and scintigraphy was carried out seven times. Various problems in the diagnosis of osteoid osteomas in relation to their localisation within bone (cortical, medullary, sub-periosteal, subarticular) and within the skeleton (near the hip, in the hand or foot, in the spine and in flat bones) are discussed.

Adolescent↗
PubMed1978

[Surgical treatment of the congenital femural defect by means of rotation plasty (author's transl)].

Experiences made in 5 cases with Borggreve's rotation plasty have shown that in cases of congenital femural defects and exceptionally also in malignant bone tumors of the distal femur this method should be suggested to the patient as a possible therapy. By rotating and shortening of the leg, the ankle joint is converted to a new knee joint. With this method an active movement of the knee joint can be obtained, so that the fitting with a below knee prosthesis becomes possible.

Abnormalities, Multiple↗