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Biomedical subjects

F Löer

Publications and source records attributed to F Löer.

At least 37 records · Page 2Linked to original sources
PubMed1982

[Value of radiologic evidence for the diagnosis of the loosening of cement-fixed total prostheses of the hip joint].

A diagnosis of loosening of cement-anchored alloarthroplasties of the hip joint is mainly based on morphological x-ray film findings. Definite signs of loosening, however, are represented by drastic positional changes or ruptures of the implant only. All other radiological signs, such as concentric or defined osseous absorptions (bordering), damage of the osseous implant bed with slight positional change, or reactive ossifications of the osseous prosthesis bed, as well as disruption of the bone cement alone, are useful only as pointers or as latent signs of loosening. It is only when several of these signs appear together in a typical constellation, that one can safely concluded that loosening has actually occurred.

Equipment Failure↗
PubMed1981

[Possible uses for computerized tomography in orthopedics].

Computer assisted tomography (CT) is a new radiographic technique, which displays a transverse representation of a slice of the body. The resulting images have a remarkable capacity for density resolution. In Neuroradiology, the use of CT is well established and it is becoming more and more often utilized for orthopaedic investigations. The value of CT in the diagnosis and management of musculoskeletal system lesions is being determined by evaluation of the literature and of our own experiences. The CT method appears definitely indicated for diagnosis and precise localization of tumors of the muusculoskeletal system. Especially, regions of complex anatomy, where determination of different angles and various anatomical measurements are possible from the display which is free from projection errors. The possibility of using CT for intravital examination of bone density of patients needs further development.

Bone Neoplasms↗
PubMedDate not supplied

A new motor-driven percutaneous bone biopsy system: technical note.

A new coaxial needle system was designed for percutaneous puncture of osteoclerotic lesions. Driven by a conventional motor unit, the instrument allows safe guidance even where difficult biopsy routes are used, and has been shown to penetrate radiopaque lesions. Preliminary clinical results from 29 patients are presented. The specimens obtained yielded a correct diagnosis in 28 cases. No major complications were observed.

Biopsy, Needle↗
PubMedDate not supplied

CT-guided percutaneous large-bore biopsies in benign and malignant pediatric lesions.

Thirty-nine consecutive pediatric patients underwent large-bore biopsies of 41 lesions under computed tomography (CT) guidance; general anesthesia was not required. Adequate material was obtained in all patients. There were no false-negative or false-positive results. Typing accuracy was 100% in malignant disease and 92% in benign lesions. No significant complications occurred. Percutaneous large-bore biopsy is a safe, reliable, and time-saving method that obviates the need for open surgery and general anesthesia in the diagnosis of primarily non-resectable lesions, or lesions that do not require resection. Another major advantage over open surgery in malignant disease is the absence of delay in starting urgently needed chemotherapy.

Adolescent↗
PubMedDate not supplied

[Curved osteotomy technique for intertrochanteric varus surgery--an experimental and computer-assisted surgery].

PURPOSE: In conventional intertrochanteric varus osteotomy, shortening of the leg and insufficiency of the abductor muscles occur frequently. To avoid these disadvantages, a curved osteotomy is presented. METHOD: 189 intertrochanteric barrel vault and wedge osteotomies were compared. By means of digitized preoperative radiographs the varus osteotomies were planned with a computer program optimising postoperative leg length, bone contact area at the osteotomy site, femoral offset, and abductor muscle length. RESULTS: The average leg shortening was 3.9 mm (range: 0-5 mm) for barrel vault osteotomy and 13.6 mm (range: 8-22.2 mm) for the wedge technique. After correction the mean contact area at the osteotomy sites was 1731.6 mm2 (range: 1087.8-2341.8 mm2) in the barrel vault technique compared with 783.7 mm2 (range: 563.7-1249.6 mm2) in the wedge procedure (p < 0.001, t-test). Adequate femoral offset was achieved in both types of osteotomy. In all curved osteotomies the length of the abductor muscles remained nearly constant in contrast to the wedge procedure. Additional comparative experimental barrel vault osteotomies in 22 human autopsy femora with a high-speed dissecting tool and round jigs revealed a precise application of the preoperative planning. CONCLUSION: The intertrochanteric curved osteotomy provides minimum leg shortening and increased bone contact area. It can prevent an insufficiency of the abductor muscles, because shortening is minimized.

Adult↗
PubMedDate not supplied

[Size and shape of commercially available polyethylene particles for in-vitro and in-vivo-experiments].

AIM: The longevity of total hip arthroplasty is sometimes limited by osteolysis and aseptic loosening. Aseptic loosening may be caused by the biologic reaction to polyethylene wear particles. Particles of less than 1 micro m diameter are of particular importance. These particles are not easily available for experimental use. METHOD: We performed a morphologic analysis of commercially available, very small polyethylene particles (Ceridust(R)) in order to determine the specific size distribution. We measured 1 978 particles. Size analysis was performed using an electron microscope. Particle size was described as the equivalent circle diameter (ECD). Particle morphology was described as feret ratio. In addition, Ceridust(R) particles were compared to different particles stemming from a hip simulator experiment. RESULTS: More than 35 % of the particles were less than 1 micro m in size. The particle size was 1.75 micro m +/- 1.43 micro m (median 1.42 micro m). The minimum was 0.06 micro m, the maximum was 11.06 micro m. The feret ratio was 0.58 +/- 0.17 (median 0.63). The minimum was 0.07, the maximum was 0.93. The majority of Ceridust(R) particles had a rough surface. Compared to polyethylene particles stemming from a hip simulator experiment, Ceridust(R) particles had a rougher surface, were less longitudinal, and had a more even size distribution. CONCLUSIONS: The pure, commercially available polyethylene particles analyzed here are suitable for in vitro and in vivo experiments due to their easy availability, minor costs, and large fraction of very small particles.

Biocompatible Materials↗
PubMedDate not supplied

[The cement free hollow hip prosthesis to reduce intramedullary pressure].

PURPOSE: A hollow cementless femoral stem has been developed to reduce intramedullary pressure and fat embolism during implantation. METHODS: In a prospective randomized clinical study, cementless hip stems (ALPHA-FIT) were implanted in 42 patients (24 women, 18 men, mean age: 65.9 years). In Group I (n=21) a solid standard stem was used. In Group II (n=21) a modified hollow stem was implanted with vertical and longitudinal communicating drill holes opening at the implant surface. During surgery the intramedullary pressure was measured by a cannula fixed distally. RESULTS: During stem insertion the mean pressure was 82 mmHg (minimum-maximum, 12-259 mmHg) for Group I and 27 mmHg (minimum-maximum, 0-48 mmHg) for Group II. This difference was statistically significant (t-test, p < 0.00076). The pressure measured in Group II was similar to the base pressure before opening of the intramedullary canal (mean 35 mmHg; minimum-maximum, 4-72 mmHg). In both groups higher pressures were found for opening of the canal, drilling with the smallest drill size and rasping. CONCLUSION: Using the hollow prosthesis, the intramedullary pressure could be reduced significantly. The higher pressures during preparation of the femoral canal need further research.

Adult↗
PubMedDate not supplied

[Revision of failed acetabular cups with extensive structural allografts].

AIM: Structural allografts are used with encouraging results for revision of failed total hip arthroplasty and in the surgery of bone tumours. The aim of the present study is to describe the clinical and radiological results achieved with structural allografts in revision of a total hip arthroplasty. MATERIAL AND METHODS: 15 patients (12 female and 3 male patients) were revised with an acetabular defect situation of type 3 A or 3 B according to the Paprosky classification. Five fresh-frozen acetabula, nine distal femora and one proximal tibia were used for acetabular reconstruction. The rigid graft fixation was performed with 2 > or = AO screws. In one case a cemented acetabular ring was implanted, four cementless cups and ten cemented polyethylene acetabular components were used. The mean follow-up was 7.9 years (1.6-11.0 years). RESULTS: A stable osseointegration of fifteen transplanted structural allografts was achieved in thirteen cases. Two allografts (one aseptic loosening, one deep infection) failed to osseointegrate. In one case the migration of a cementless cup was registered. Revision surgery of this female patient was performed successfully with a cemented reconstruction ring. The mean Harris hip score at the latest follow-up was 81.4 points (70-99 points). CONCLUSION: For reconstruction of acetabular bone stock and restoration of the bone anatomy structural allografts can be recommended. The use of cementless cups in combination with structural grafts is to be evaluated as critical.

Acetabulum↗
PubMedDate not supplied

[Localization of the neurokinin 1 receptor in hip joints of patients with painful osteoarthritis].

INTRODUCTION: Recent studies on osteoarthritis have focused on nociceptive substance P (SP) containing afferent nerve fibres. The effects of SP are known to be mainly mediated by the tachykinin receptor neurokinin 1 (NK1-R). AIM: The aim of the present study was to demonstrate the NK1-R in human joint tissues. METHODS: The hip joint capsule of three patients with painful hip osteoarthritis (Group 1), three patients with femoral neck fracture showing no cartilage destruction (Group 2, controls) and the soft tissue of the fossa acetabuli of Group 1 were resected during hip arthroplasty implantation. The tissue samples were cut into small blocks and immersion-fixed in Zamboni's fixative. The specimens were frozen, cut into 50 microm sections and immunostained using a standard immunohistochemical staining protocol. RESULTS: In Groups 1 and 2 the NK1-receptor was localised in the wall of venous vessels, on Schwann cells of nerve bundles and on nerve fibres. In the osteoarthritis group the staining pattern was similar but the number of NK1-bearing cell structures seemed to be enhanced. CONCLUSIONS: The present study provides the first evidence of NK1-R in the human hip joint. In patients with painful osteoarthritis the density of NK1-R-positive cell structures seemed to be increased. The localisation of the NK1 receptor on different cell types suggests multiple effects of SP in normal and osteoarthritic joints.

Acetabulum↗
PubMedDate not supplied

[Effects of bisphosphonates in arthroplasty].

AIM: This study presents an overview of the general effects of bisphosphonates and in particular of their effects on different problems in joint arthroplasty. METHOD: First the chemical properties are described, then the biological effects. It is already known that bisphosphonates have effects on orthopaedic diseases and an increasing number of studies are investigating what effects can be achieved in joint arthroplasty with these substances. RESULTS: The bisphosphonates group was derived from industrial pyrophosphate which is used to prevent calcification. Bisphosphonates inhibit bone mineralisation and resorption. Several direct and indirect mechanisms are responsible for these effects. The inhibition of bone resorption is used to benefit patients suffering from various diseases causing increased bone resorption. Treatment with bisphosphonates results in greater bone density and improved mechanical bone quality. Indications for this treatment include osteoporosis, tumour-associated osseo-destruction, fibrous dysplasia and Paget's disease. Recent studies have shown that osseo-integration of metal implants is accelerated and periprosthetic bone loss, which is caused by various different mechanisms during the lifetime of an implant, can be reduced. CONCLUSION: Bisphosphonates have been an established element in the treatment of bone metabolic disorders for many years. Their use in joint arthroplasty could become increasingly important.

Animals↗
PubMedDate not supplied

[Influence of the x-ray technique on evaluation of cup anteversion after total hip arthroplasty].

AIM: Total hip arthroplasty (THA) is a standard procedure in orthopaedic surgery. Planar radiography of the implant is routinely performed to ensure that the operation has achieved the desired result. This study investigates the influence of varying the X-ray beam on the analysis of the radiograph. METHOD: Twenty-three patients were analysed after implantation of a total hip replacement. Besides a CT scan of the pelvis, symphysis- and hip-centred radiographs were available. The cup anteversion was calculated using two published algorithms. The CT-based data were the gold standard. RESULTS: Our study revealed a significant major error in the analysis of the symphysis-centred radiographs when compared with the hip-centered radiographs. Widmer's algorithm showed a significant superiority over Pradhan's formula. CONCLUSION: The best approximation of the anteversion angle was achieved using Widmer's technique by centering the X-ray beam onto the hip.

Acetabulum↗
PubMedDate not supplied

[Studies on the stability of pertrochanteric fractures following the application of various osteosynthesis techniques with special reference to torsional forces at the proximal femur].

Fourteen different commonly used osteosyntheses for unstable pertrochanteric fractures with medial bone defect were systematically analysed concerning their stability. For this purpose the deformation and the maximum stability of 36 surgically stabilized fractured femora from donor corpses were tested. For the experimental investigations the hip force FM was not only induced on the femora in orthograde direction but also in an inclination of 45 degrees of anteflexion of the femur as it appears during walking up stairs. As a result, all tested osteosyntheses had significantly lower maximum stability and greater deformation if the hip force was induced on the anteflexed femur in contrast to orthograde loading. From our analysis clinically important conclusions can be drawn concerning the operation techniques and the post-operative after treatment concepts.

Biomechanical Phenomena↗
PubMedDate not supplied

[The magnitude of forces acting on the proximal femur in various weight alleviating gait forms with reduced ground reaction forces].

To estimate the forces of the hip during partial or non-body-weight-bearing-gait a simple mechanical principle was used. For identification of the acting muscles of the hip during the swing period Electromyography was used. In the pure swing period without ground touch, being recommended as "de-loading" for the hip, forces resulted up to 85% of body-weight. In contrast to that, partial body-weight-bearing with limb-weight (approximately 12-15% body weight) resulted in the most efficient reduction of hip forces.

Biomechanical Phenomena↗
PubMedDate not supplied

[Surgical technic in femur shaft fenestration within the scope of revision operations following hip joint total endoprostheses].

In revision arthroplasty the loss of stability secondary to fenestration of the proximal femur reduces the loading capacity of the limb and increases the risk of postoperative fractures. Trying to improve the fenestration technique we tested the usual fenestration procedure experimentally. Besides pure axial load we investigated the torsional forces of the proximal femur in the bended hip position. We recorded the deformation under increasing load and analysed the fracture pattern. The results shows an unwarantable loss of stability in lateral or complete ventral fenestration procedures. Ventral fenestration procedures with smooth edges and intact proximal bony ring having additional prosthesis stem support presented the best mechanical results. According to the tolerated load it is possible to give guide-lines for the postoperative treatment in the cemented and cementless arthroplasty of the hip joint.

Adult↗
PubMedDate not supplied

[A treatment principle with questionable effectiveness in Perthes disease].

The reduction of hip joint forces is a generally accepted part of the conservative treatment of Perthes disease. To reach this effect with help of splints (e.g. Thomassplint and the following models) does not seem to be efficient enough even from a clinical point of view. Theoretical considerations of former investigations of other authors point out the insufficient effect of these splints regarding the hip joint force reduction during the weight bearing phase in walking. The effect of these splints during the non-weight bearing phase in walking with regard to the hip joint forces has not been investigated so far. Therefore this paper is dealing with the forces onto the hip joint during the swinging phase of the leg with a splint, shown in a simplified, mechanical model. The results reveal significantly higher hip joint forces if the splint is used compared to the physiological forces during the swinging phase which in a static situation rise up to twice the body weight. These joint loadings are important because they occur during hip flexion and therefore cause pressure on the ventro-cranial part of the head of the femur, a region which unfortunately is often involved in Perthes' disease and therefore especially vulnerable to these forces. From a biomechanical point of view the principle of reducing the hip joint forces with splints has to be abandoned.

Biomechanical Phenomena↗
PubMedDate not supplied

[Analysis of stress on the proximal femur in various kinds of loading using the finite element method].

Loading of the limb in bending hip position causes a torque loading component in respect to the femoral axis. In this condition a characteristical increase of the mechanical tension of the femoral surface occurs. The tension was calculated for different kinds of loading and for the first time in different bending hip positions by means of Finite-Element-Method (FEM). The results show, that the torque loading component causes different torsional deformations. Even in physiological gait patterns different sizes of torsion and even changing of the direction of the torsion could be demonstrated.

Biomechanical Phenomena↗