Biomedical subjects

H J Refior

Publications and source records attributed to H J Refior.

At least 19 recordsLinked to original sources

PubMed1995

[Effect of the manufacturing process on creep and wear properties of UHMWPE (ultra-high molecular weight polyethylene)].

The creep and wear behaviour of pressed UHMWPE and extruded UHMWPE was compared, taking Chirulen and extruded UHMWPE of the Lennite type as examples. Using the ring-on-disc test, the wear and deformation volumes per 360,000 cycles were determined. The static tests were performed at surface pressures of 5.62 MPa and 9.37 MPa, while the test duration was 41.86 and 100 hours, respectively. The surface pressures result from the axial forces of 900 N and 1500 N, respectively, and a ring surface analogous to the DIN 58,835 and ISO 6474 standards. Between conventionally pressed and the extruded UHMWPE material differences of up to 350% in the sums of wear and deformation were found. It was noted that already at low surface pressures the extruded UHMWPE is more susceptible to creep deformation than is the conventionally pressed material, and that this effect dramatically increases at high surface pressures.

Biomechanical Phenomena↗

PubMed1994

Surgical treatment of acromioclavicular dislocation.

Sixty-five patients were operated on for acromioclavicular dislocation between 1980 and 1991. Seventeen type II and 48 type III dislocations according to the criteria of Tossy et al. were treated. Three different surgical techniques were employed. (1) tension band wiring, (2) a modification of the Bosworth repair, (3) reconstruction of the ligaments with augmentation by a PDS (polydioxanon) cord. Forty-four patients could be investigated retrospectively, and an additional 12 were recorded by questionnaire. The Taft score was used, representing self-assessment, clinical statements and radiological findings. Of all investigated patients 87.5% had a normal range of motion without any loss of strength, and 32% suffered an osteoarthritis of the acromioclavicular joint. The average Taft score was 9.8. With respect to the three surgical techniques, reconstruction of the ligaments augmented by a PDS cord produced the best result, an average Taft score of 10.8.

Acromioclavicular Joint↗

PubMed1994

[MRI in orthopedics: diagnosis of joint disorders].

For the visualization of joint structures, magnetic resonance imaging (MRI) has definite advantages over other imaging modalities. High soft tissue contrast and multiplanar capabilities contribute to adequate representation of the joints. With surface and special coils as well as high gradient field strengths, superior spatial resolution can be achieved, thus allowing for depiction of fine anatomical details. Newly developed pulse sequences, especially with fat suppression techniques and utilization of paramagnetic contrast agents (gadolinium complexes) have improved image contrast. Examination techniques, results and diagnostic value of MRI in various joints are discussed. Close cooperation between orthopaedic surgeons and radiologists is mandatory for effective and economically acceptable use of MRI in the diagnosis of joint disorders.

Ankle Joint↗

PubMed1994

[Results of surgical treatment of posterior knee instability].

A retrospective study was performed to evaluate the outcome of operative treatment of posterior cruciate ligament (PCL) lesions in 115 patients operated on between 1980 and 1989. Follow-up was possible in 89 patients at 18-124 months postoperatively (average 76 months). In 65 re-examination was possible, while 24 patients returned a questionnaire. The results of patients who were operated on in the acute state were superior to those with chronic instabilities (Lysholm 79.9 +/- 18.5 vs 64.3 +/- 22.1; Tegner 5.7 +/- 2.3 vs 4.2 +/- 2.2; instrumented posterior drawer 5.3 +/- 3.5 mm vs 5.9 +/- 3.8 mm). On the other hand, the preoperative scores of symptomatic patients with chronic instabilities (Lysholm 38.8 +/- 22.0; Tegner 2.1 +/- 1.7) were clearly lower. Extraarticular procedures (Hughston) slightly improved symptoms in posterolateral instabilities. Olecranization of the patella had no influence on the results. Interpretation of the data is difficult as there was no matched group of patients with nonoperative treatment. A reviews of the literature suggests that isolated PCL tears are best treated with conservative management. Only in cases where associated ligamentous injuries require operative treatment should PCL reconstruction be performed. Chronic posterior instabilities should be treated operatively only if the patients are severely symptomatic. However, complete restoration of knee stability was usually not achieved with the techniques presented in this paper.

Adolescent↗

PubMed1993

Mechanical failure of the femoral component in cemented total hip replacement--a finite element evaluation.

The quality of cementation is of paramount importance for the long-term clinical outcome in cemented total hip replacement. Four "modes of failure" have been differentiated by various authors and correlated with the clinical findings. A finite element analysis was performed to simulate an ideally cemented femoral stem-type prosthesis as well as failure modes III (proximal anchorage of implant only) and IV (Distal anchorage of implant only). While failure mode III produces a stress distribution at the bone/acrylic cement interface, which is similar to the ideally cemented prosthesis, failure mode type IV leads to a hazardous rise of the interface stresses. This correlates well with the clinical findings given in the literature, thus validating the computer simulation used. Distal cementation only of a stem-type femoral component in total hip replacement should definitely be avoided.

Bone Cements↗

PubMed1993

[Primary suture of the anterior cruciate ligament. A critical analysis].

Recently some authors have claimed that primary repair of an acute tear in the anterior cruciate ligament will fail in the long run. A review of the literature reveals that this opinion is mainly based on an American study in 1976. However, the poor results presented in this study were never reproduced. The study is critically analyzed, and 14 more papers presenting successful primary reconstructions of the anterior cruciate ligament are discussed. Preserving proprioceptive structures may be an important advantage of this technique, as it is hypothesized that the anterior cruciate ligament functions as a significant sensory organ, not only providing proprioceptive information, but also initiating protective and stabilizing muscular reflexes. In conclusion, it is recommended that primary suture be used combined with intra-articular semitendinosus tendon augmentation for rapid rehabilitation in cases of acute tears in the anterior cruciate ligament.

Anterior Cruciate Ligament↗

PubMed1992

Clinical results and radiologic findings after cementless implantation of PCA stems in total hip replacement.

The results of radiologic and clinical follow-up of 81 PCA (porous coated anatomie) hip joint prostheses implanted in our clinic between 1986 and 1988 are presented. One of the prostheses had to be explanted because of aseptic loosening after 2.5 years' implantation. Contrary to the fixation concept of the prosthesis, which requires both proximal osseointegration and free axial shifting of the distal part of the prosthesis, our follow-up radiographs showed proximal lysis of 2 mm and more as well as distal hypersclerosis of 3 mm and more in the form of endosteal bone formation in 70% of cases 3 years after implantation. On the basis of our data, the question whether these bone reactions will finally lead to aseptic loosening of the implant cannot be answered yet.

Biomechanical Phenomena↗

PubMed1992

Bone-cement removal with the excimer laser in revision arthroplasty.

The excimer laser was thought to be an appropriate tool for the removal of bone cement without damaging the bone. However, due to its low ablation rate, its clinical use in total hip revision arthroplasty proved to be impossible. This experimental study was designed to evaluate the maximal ablation rate by adjusting the laser's parameters. Energy density, frequency, pulse duration, radiation area, quantity of pulses, and environmental conditions were varied in the experimental setup. Even with the best set of parameters the excimer laser was about ten times slower than, e.g., the carbon dioxide laser. The removal of 10 g bone cement takes about 1 h. Thus, complete cement removal by means of the excimer laser alone is not possible. However, selective application of the excimer laser in combination with other techniques could be discussed.

Arthroplasty↗

PubMed1992

Moderate heat treatment of bone allografts. Experimental results of osteointegration.

The use of bone allografts is often essential in orthopedic surgery. Strict donor screening, including HIV testing 3 months postoperatively, is mandatory before a transplant may be used. Yet these measures do not definitely rule out the possibility of HIV transmission, as there is a window period before infection is revealed by blood testing. Accordingly, there is a need for virus inactivation methods that can be used on bone allografts. As radiation treatment and chemical methods have a number of disadvantages, we chose a moderate heat treatment of 65 degrees C for a series of animal experiments. In 12 rabbit femoral condyles, moderate-heat-treated bone allografts were implanted into 6-mm drill holes. Twelve normal allografts and 12 empty drill holes served as controls. Radiologic and histological evaluation up to 12 weeks postoperatively revealed slow spontaneous bone remodeling from the rim to the center of the empty cavities. Normal deep frozen allografts were quickly intergrated after a short period of osteoclast reaction around the transplant, with occasional bone bridges between host and allograft. The examination of heat-treated allografts showed no differences to the controls, including morphologic aspects and the time course of osteointegration. Five zones of bone repair and osteointegration were distinguished. We conclude that thermal treatment of bone allografts has adverse effects on osteointegration in the rabbit femoral condyle. Thus, it may contribute to improving safety in human bone transplantation.

Animals↗

PubMed1992

[Results of the surgical therapy of distal biceps tendon rupture].

The rupture of the distal tendon of the biceps brachii is a relatively uncommon but severe injury of the upper extremity. Different techniques for surgical reattachment are described with a small number of patients. The purpose of this study was to show whether the surgical technique modified after Max Lange leads to good clinical results in the number of eleven patients who underwent physical examination between six months and eight years after surgical repair. Three patients showed a small deficit in the range of motion. Six patients had ossifications in the distal tendon, no patient had an osteoarthritis of the elbow. Strength and endurance, tested by the Cybex-II isokinetic dynamometer, showed no significant difference between operated and healthy extremity. The surgical technique modified after Max Lange is a safe and effective way for reattaching the distal tendon of the biceps brachii.

Adult↗

PubMed1992

[Results of surgical treatment of proximal biceps tendon rupture].

During a 9-year period we operated on 19 patients in whom the proximal tendon of the biceps brachii muscle had been disruptured. Various surgical techniques were employed, such as refixation at the processus coracoideus, tenodesis in the sulcus intertubercularis, keyhole operation, in combination with an intraarticular inspection, revision, or if necessary widening of a narrow passage ("defile"). Follow-up was possible in 15 patients for an average period of 3 years after the operation, in respect of clinical, roentgenological and isokinetic findings. Results were mainly good while employing a variety of different surgical techniques; in only 3 patients the shoulder function remained restricted, painful and/or weakened. The isokinetic maximum torque was either increased on the operated side (after coracoid refixation) or reduced (after tenodesis in the sulcus). The underlying biomechanical causes are explained. Good results can be obtained in surgical treatment of the rupture of the proximal biceps tendon provided the procedure is accurately executed while taking into consideration, at the same operation stage, the associated pathology of the rotatory cuff. For biomechanical reasons, preference should be given to the operations according to Hitchcock and Bechtol in respect of refixation, and to the keyhole operation method.

Adult↗

PubMed1990

Destructive changes of the spine in magnetic resonance imaging.

Twenty-nine patients were examined by magnetic resonance imaging for various lesions of the spine. The results of these scans were compared with those of plain radiographs, computertomographs, and radionuclide bone scans. The findings were substantiated by intraoperative or histological findings in 18 cases. The MRI scans proved to be very sensitive in the detection of a wide spectrum of morphological changes of the bone marrow of vertebral bodies. Characteristic changes of the signal patterns for inflammatory and tumorous lesions were not observed. The differentiation of these lesions will presently continue to have to be based on morphological criteria.

Adolescent↗

PubMed1990

The importance of functional magnetic resonance imaging (MRI) in the planning of stabilizing operations on the cervical spine in rheumatoid patients.

Chronic inflammatory diseases, such as chronic polyarthritis or spondylarthritis ankylopoietica, can occasionally lead to vertebral instabilities of the occipitoatlantal or atlantoaxial level, requiring some form of stabilizing operation. By means of functional magnetic resonance imaging, i.e., with the cervical spine at its maximal range of flexion and extension, performed on 11 patients suffering from an instability at the above level, it was possible to demonstrate not only the extent of synovial tissue, but also how this sometimes excessive soft-tissue growth hinders an adequate reduction of the subluxated vertebrae. The importance of this investigation lies in the fact that the necessary operation can be planned appropriately. As such, three patients required a decompressing operation entailing resection of the posterior arch of the atlas, widening of the foremen magnum, or both.

Aged↗

PubMed1990

[Patellar dislocation as a cause of osteochondral fracture of the femoro-patellar joint].

Acute traumatic dislocation of the patella may be associated with osteochondral fractures. Clinical examination invariably shows a tense effusion. A detailed radiographic examination including antero-posterior, lateral and skyline views of the patella is usually necessary to establish an exact diagnosis. Once diagnosis is made open reduction and fixation of the osteochondral fracture should be carried out if it is possible. Out of 78 patients of our own with patella dislocation 24 cases suffered an osteochondral fracture. In ten cases refixation of the osteochondral fragment was achieved. Intraoperatively the alignment of the patella was controlled in any case. In cases of lateral subluxation lateral release and medial reconstruction was performed. In two cases medial transfer of the tibial tuberosity was carried out. Osteochondral fractures of the femoro-patellar groove represent an important injury in the course of acute patellar dislocation. With exact diagnosis and correct treatment congruity of the femoro-patellar joint can be restored in many cases.

Bone Transplantation↗

PubMed1990

[The treatment of post-traumatic recurrent anterior shoulder dislocation using Du Toit's operation].

From 1.4. 1986 to 31.12. 1987 we operated 21 patients with a recurrent anterior dislocation of the shoulder with the Du Toit staple capsulorrhaphy. 20 patients we followed clinically and radiologically for an average period of one year and four months. By using a rating sheet 17 patients had an excellent and three patients a good result. There was, against other operation techniques, a minimally limiting of external rotation. We had no recurrents of dislocation. We concluded that the Du Toit staple capsulorrhaphy makes necessary only short postoperative immobilisation and renders an early return of motion and that a good function can be expected.

Adult↗

PubMed1990

[Scintigraphic control and x-ray findings following the cement-free implantation of the PM shaft in connection with hip joint allo-arthroplasty].

147 bone scans with 99mTc-MDP following 60 cementless hip arthroplasties were analysed at 3 to 160 weeks after operation. Results are compared to clinical evaluation according to Merle d'Aubigné. X-ray changes in a number of patients are included. In uncomplicated cases, bone scan activity decreased quickly within 26 weeks postoperatively. Decrease of scintigraphic activity was markedly delayed in patients with low Merle d'Aubigné values or persisting pain. In 4 cases, bone scan activity increased again. In these cases, reoperation revealed rotational instability of the shaft endoprostheses. Unusual x-ray phenomena such as development of a bony cup at the tip of the prosthesis or seams were found mainly in patients with less satisfying results. We consider nuclear imaging an important additional examination to evaluate bony integration of PM shaft endoprostheses after hip replacement, especially as interpretation of x-ray features alone is still doubtful.

Adult↗

PubMed1990

[Use of a capacitive measuring mat for recording inter-fragment pressures and pressure distribution in ventral inter-corporal spondylodesis].

With respect to ventral interbody fusion, rates of pseudarthrosis of up to 30% are reported. With the aim of reducing this figure, the use of dorsal fixation systems to stabilise the fused spinal units is recommended by a number of authors. The aim of these osteosynthetic procedures is to elevate the interfragmentary compression between the ventral bone block and the adjacent vertebrae. In order to measure the pressure achievable, and its local distribution, an experimental investigation involving the use of a capacitive measuring mat has been designed. The system of capacitive measurement and its application to the spine is described. The simple mode of measurement and mechanical stability, combined with high accuracy, are the specific advantages of capacitive systems of measurement. Especially in the documentation of interfragmentary pressure and pressure distribution, capacitive measuring mats are superior to comparable systems.

Biomechanical Phenomena↗

PubMed1989

Micromotions in the primary fixation of cementless femoral stem prostheses.

Thirty cementless femoral stems of six different types of hip endoprostheses were implanted in femurs taken at autopsy and underwent static loading and afterwards dynamic loading of 50,000 cycles to simulate walking during the early months after implantation. After that, the static load tests were performed again. During both static load series a certain amount of micromotion between stem and implantation bed occurred in the frontal and sagittal planes and also during rotation. The six prostheses exhibited clearly differing results. The influence of dynamic load on the extent of micromotion was small.

Bone Cements↗