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Biomedical subjects

U Pfister

Publications and source records attributed to U Pfister.

At least 19 recordsLinked to original sources
PubMed2005

Primary stability of various forms of osteosynthesis in the treatment of fractures of the proximal tibia.

The treatment of fractures of the proximal tibia is complex and makes great demands on the implants used. Our study aimed to identify what levels of primary stability could be achieved with various forms of osteosynthesis in the treatment of diaphyseal fractures of the proximal tibia. Pairs of human tibiae were investigated. An unstable fracture was simulated by creating a defect at the metaphyseal-diaphyseal junction. Six implants were tested in a uniaxial testing device (Instron) using the quasi-static and displacement-controlled modes and the force-displacement curve was recorded. The movements of each fragment and of the implant were recorded video-optically (MacReflex, Qualysis). Axial deviations were evaluated at 300 N. The results show that the nailing systems tolerated the highest forces. The lowest axial deviations in varus and valgus were also found for the nailing systems; the highest axial deviations were recorded for the buttress plate and the less invasive stabilising system (LISS). In terms of rotational displacement the LISS was better than the buttress plate. In summary, it was found that higher loads were better tolerated by centrally placed load carriers than by eccentrically placed ones. In the case of the latter, it appears advantageous to use additive procedures for medial buttressing in the early phase.

Biomechanical Phenomena↗
PubMed2004

Two procedures for Kirschner wire osteosynthesis of distal radial fractures. A randomized trial.

BACKGROUND: The treatment of displaced Colles-type fractures of the distal part of the radius remains a challenge. Two procedures for closed reduction and Kirschner wire osteosynthesis of these fractures were compared in a prospective randomized study. METHODS: One hundred consecutive patients with a Colles fracture of the distal part of the radius (AO classification 23-A2, 23-A3, or 23-C1) were treated over an eighteen-month period. One group was managed with the conventional method, described by Willenegger and Guggenbuhl in 1959, in which two Kirschner wires are introduced into the styloid process of the radius. The other group was treated with the Kapandji method, as modified by Fritz et al., in which two Kirschner wires are inserted into the fracture gap and a third is placed through the styloid process. Postoperative care was standardized for both groups and carried out according to a strict procedure. Forty patients who had been operated on according to the modified Kapandji method and forty-one treated with the Willenegger technique were available for follow-up, for a follow-up rate of 81%. The follow-up assessment was performed with a modified version of the Martini score. RESULTS: The median time to follow-up was ten months (range, six to twenty months). The results as assessed with the Martini score were, on the average, good to very good for the patients treated with the Kapandji method and satisfactory to good for the patients treated with the conventional Kirschner wire fixation. The duration of radiographic exposure was significantly shorter with the Kapandji method than with the Willenegger technique. CONCLUSIONS: Conventional Kirschner wire fixation remains a good method of osteosynthesis for the treatment of displaced fractures of the distal part of the radius. We found both the functional and radiographic outcomes of the Kapandji method to be significantly better than those of the Willenegger technique. LEVEL OF EVIDENCE: Therapeutic study, Level I-1a (randomized controlled trial [significant difference]). See Instructions to Authors for a complete description of levels of evidence.

Adult↗
PubMed2003

[Scapho-capitate fracture syndrome of both hands--first description of a bilateral occurrence of a rare carpal injury].

The scapho-capitate fracture syndrome is a rare but severe injury of the carpus. It is characterized by a rotation of the proximal fragment of the capitate bone of 90 or 180 degrees and a fracture of the navicular bone in the intermediate third. This injury is caused by a fall on the outstretched and dorsiflected hand. The scapho-capitate fracture syndrome was firstly described in 1956 by Fenton. There are 31 cases described in literature but none of these involves both hands. Here we describe the first case of scapho-capitate fracture syndrome in both hands, in a 21 year old woman who jumped out of a window with suicidal intentions. She was treated operatively by Herbert-screws and K-wires.

Adult↗
PubMed2002

[Isolated transverse fracture of the os triquetrum. Case report of a rare injury].

With the case of a 25 year old patient we will report of a rare injury, the isolated body fracture of a triquetrum bone. This kind of injury often happens in dorsalflected and ulnarducted hand position because of the anatomical position of the triquetral bone. The therapy of choice is conservative treatment with a volar splint for three to six weeks. Operation is only necessary in case of dislocation of a fragment [4]. Complications as an aseptic necrosis of a fragment is not reported. We found only one case of a pseudarthrosis [5]. Even in our case occurred a complete healing of the bone and a complete functional remission.

Adult↗
PubMed2001

[Esophageal perforation by osteosynthesis material after ventral spondylodesis of the cervical spine].

Esophageal perforation after cervical spine surgery is a rare complication. Based on the case of a 77-year-old female patient with a late, asymptomatic esophageal perforation after a ventral spondylodesis of the cervical spine, the symptoms, diagnostics, and therapy of this complication are discussed. The therapy of choice is the operation. Nonoperative therapy should only be chosen--like in our case--for special indications. An esophageal perforation with symptoms should be treated operatively. Our patient was treated conservatively in consideration of her age and missing symptoms.

Aged↗
PubMed2000

Technical innovations in medullary reaming: reamer design and intramedullary pressure increase.

BACKGROUND: Reaming the medullary cavity leads to an increase in intramedullary pressure, which can cause local necrosis and lung malfunction after intramedullary nailing. This investigation concentrates on the effect of reamer design parameters on intramedullary pressure increase. METHODS: Pressure measurements were obtained for three newly designed solid reamers and one hollow reamer. The AO/ASIF reamer was used for reference values. All reamers were connected with small flexible shafts. The pressures were measured in Plexiglas tubes filled with a mixture of Vaseline and paraffin oil with flow properties at 20 degrees C equivalent to those of bovine medullary fat at 36 degrees C. The reaming assemblies were inserted into the tubes using a materials testing machine at a constant speed. In addition, pressure measurements were made using five pairs of human femora. RESULTS: The highest pressures occurred with the AO/ASIF reamer head (258+/-29 mm Hg, p+/-0.05). By creating a conical form and enlarging the flutes, pressures were reduced by up to 37% (164+/-13 mm Hg, p < or = 0.05) compared with the AO/ASIF reamer, depending on the depth of the flutes. With a newly designed hollow reamer, pressure was reduced by 58% (108+/-19 mm Hg, p < or = 0.05) compared with the AO/ASIF reamer. CONCLUSION: The results show that optimizing the design of the reamer head leads to a significant reduction in pressure increase. These results should be taken into consideration when designing new reaming systems in an attempt to minimize the complication rate for intramedullary nailing.

Analysis of Variance↗
PubMed1998

[Clinical results of primary intramedullary osteosynthesis with the unreamed AO/ASIF tibial intramedullary nail of open tibial shaft fractures].

From 04/91 to 06/96 sixty-nine open fractures of the tibia were primarily treated on the day of the accident with unreamed nailing (UTN, Synthese). The distributions of fracture type according to the AO classification and of soft tissue injury according to Gustilo were as follows: fracture type: A: 28%, B: 52%, C: 20%; soft tissue injury: I: 30%, II: 28%, IIIA: 12%, IIIB: 12%, IIIC: 6%. Of the 65 fractures assessed 46 (71%) healed within 18 weeks without secondary intervention. There was delayed healing in three fractures requiring secondary conversion to reamed nailing. Eight fractures (12%) developed pseudarthrosis of which five (8%) healed uneventfully. Deep infections was manifest in four fractures (6%). Three of these infections developed after secondary intervention to treat pseudarthrosis. Seven of the eight pseudarthroses and three of the four infections healed eventually. Revision procedures were necessary in 11 patients (17%) to deal with disturbed fracture healing or infection (10 reamed nailing procedures, three cancellous bone grafts, and one of each of the following: sequestrectomy, fibular osteotomy, plate fixation, external fixator, monorail procedure). The results show that the same good infection rates were achieved for the UTN as for the external fixator. The advantages of the UTN are, however, a lesser need for secondary intervention and greater patient comfort. Therefore, we find the UTN to be a good alternative to the external fixator in the treatment of open fractures with severe soft tissue damage.

Adolescent↗
PubMed1998

Distribution of mobilized progenitor cells in the buffy coat of the haemonetics MCS3p cell separator: a study to optimize the collection of progenitors by leukapheresis.

Hematopoietic progenitor and stem cells for transplantation can be mobilized into the circulation and collected by leukapheresis. In this procedure, the leukocytes are distributed in the buffy coat along a density gradient, and the composition of the final product depends on which layer was collected. For the Haemonetics MCS3p Cell Separator, the manufacturer recommended starting the progenitor cell collection at a light transmission of 30%-40% (compared with plasma) and continue it for 40-50 ml. To optimize the use of this machine, the buffy coat it produces was studied in 12 patients by collecting it in fractions of increasing specific weight. Each fraction was analyzed by morphology, immunocytometry, and cell culture. We found that the buffy coat uniformly contains 8 times more leukocytes than blood, but the proportion of each white cell type varies along a gradient. The lymphocyte-predominant lighter layers are richer in CD34+ cells when compared with the granulocyte-predominant denser layers (6-14 times versus 2-4 times more than blood). The majority of CD34+ cells are found at a light transmission of 10%-70% (hematocrit 6-9). We conclude that cells for transplantation should be collected in a lighter fraction of the buffy coat than originally suggested by the manufacturer.

Antigens, CD↗
PubMed1997

[Guidelines in trauma surgery--geriatric traumatology].

The treatment of injuries in elderly patients requires thorough planning. Preexisting diseases and the current status determine the priorities and methods of treatment. The advantages of extensive preoperative assessment must be judged against the risks of a delay in undertaking operative measures. Fracture treatment aims at fast, careful and simple fixation, which is nevertheless stable and sufficient. Modern methods and implants allow acceptable results to be achieved, even under the limitations of modern health care systems.

Aged↗
PubMed1996

[What treatment expectations does the elderly patient have from surgery and what can surgery achieve? From the viewpoint of joint surgery].

Age-dependent wear, increasing proneness to injury during unsuitable activities and sudden falls caused by a general frailness are the reasons why the aged patient meets the joint surgeon. The desired treatment comprises different aims: painless and free motion, full weight-bearing capacity, avoidance of permanent nursing, facilitation of nursing. Adequate osteosynthetic techniques and the application of artificial joint replacement usually allow a fair restoration with early mobilisation and weight-bearing. The operative risks in the acute situation are higher than in elective surgery, while the long-term results of hip and knee replacements are very good.

Activities of Daily Living↗
PubMed1994

The incidence, pathogenesis, diagnosis, and treatment of fat embolism.

Fat embolism syndrome is a potentially serious and life threatening complication of long bone trauma, blunt trauma, and intramedullary manipulation. In long bone fractures, fat embolism is encountered in 0.9% to 2.2% of cases. During intramedullary manipulations, such as prosthetic stem insertion or reaming, the incidence is typically lower (range, 0.5% to 0.8%). Diagnosis is dependent upon the clinical recognition of dyspnea, petechiae, and cognitive dysfunction in the first several days following fracture, trauma, or intramedullary surgery. Treatment consists of pulmonary support and aggressive resuscitation. Studies support early fracture fixation, but the role of systemic steroids, heparin, and other modalities remains speculative.

Brain Diseases↗
PubMed1993

Intramedullary pressure, strain on the diaphysis and increase in cortical temperature when reaming the femoral medullary cavity--a comparison of blunt and sharp reamers.

Clinical application has shown intramedullary nailing to be a safe therapeutic procedure, although damage to the vascular system and fat embolism have been demonstrated in animal experiments. The main negative factors were presumed to be the increase in intramedullary pressure and the increase in cortical temperature. In this study, the effect of the blunting of the reamers on the increase in intramedullary pressure, the tangential strain on the diaphysis and the increase in cortical temperature was to be clarified. The measurements were carried out on pairs of human femora reamed with sharp and blunt AO reamers. The pressure was measured in the middle of the diaphysis and in the metaphysis, the strain in the middle of the femur and the temperature on four aspects of the femur. The femora were reamed with identical compression and traction forces in a water bath at 37 degrees C. In comparison with the sharp reamer, the blunt reamer develops 2.1 times the positive diaphyseal pressure, 1.7 times the positive metaphyseal pressure, 1.6 times the negative diaphyseal pressure, 1.5 times the positive tangential strain, 55 times the negative tangential strain and 2.8 times the increase in cortical temperature. There is no difference in the negative metaphyseal pressure. Since blunt reamers produce greater intramedullary pressure values, greater tangential strain on the diaphysis and a greater increase in cortical temperature, the attention of surgeons and operating staff must be drawn to the fact that they should treat the reamers gently and replace them whenever necessary.

Equipment Failure↗
PubMed1993

Extent of bluntness and damage to reamers from hospitals.

The negative effects of intramedullary nailing, such as aseptic cortical necroses and fat embolisms, are mainly caused by an increase in intramedullary pressure and an increase in cortical temperature during the reaming process. The degree of bluntness of the reamers has a negative influence on these two parameters. The objective of this study was to examine the degree of bluntness and damage to intramedullary reamers in clinical use. 10 sets of intramedullary reamers returned from Swiss clinics were examined with regard to the radius of the cutting edge and the degree of damage. The following results were established (MN = medullary nailings): Sharpest reamers: hospitals with 300-400 beds. Hospitals with < 5 MN per year. Bluntest reamers: hospitals with > 1000 beds. Hospitals with 40-60 MN/year. Least damaged reamers: hospitals with 300-400 beds. Hospitals with 40-60 MN/year Most damaged reamers: hospitals with > 1000 beds. Hospitals with 40-60 MN/year Due to the fact that some of the reamers in clinical use are of inadequate quality both with regard to the sharpness of the milling lips and the degree of damage, doctors and operating staff should be instructed to check the quality of cutting tools before using them, to treat them carefully and to replace them if necessary.

Equipment Failure↗
PubMed1993

Influence of the compression force on the intramedullary pressure development in reaming of the femoral medullary cavity.

The reaming process is considered the main damage factor in intramedullary nailing, as there are repeated increases in intramedullary pressure and cortical temperature, which can lead to aseptic cortex necroses and fat embolisms. In this study, the influence of the compression force on the increase in pressure is to be examined. The intramedullary pressure was measured in the middle of the diaphysis and in the metaphysis of human femora reamed under various compression forces. The compression force exerted by the surgeon was measured on polyurethane femora. It was observed that an increase in the compression force of 1.8 times led to an increase in the diaphyseal pressure of 4.7 times and of the metaphyseal pressure of 3.1 times. As surgeons exert high compression forces, peak pressures of 970 mmHg diaphyseally and 1150 mmHg metaphyseally must be expected in the hospital. If reaming is carried out with less compression force, the intramedullary pressure can easily be reduced by 79% in the area of the diaphysis and by 68% in the metaphysis.

Femoral Fractures↗
PubMed1993

Effect of flexible drive diameter and reamer design on the increase of pressure in the medullary cavity during reaming.

Reaming the medullary cavity before insertion of an intramedullary nail, results in an increase in both temperature and pressure. This may lead to aseptic necrosis of the cortex and to fat embolism, whereby the increased pressure in the medullary cavity plays a significant role. This paper aims to determine whether a reduction of the drive diameter combined with a different reamer design reduces the amount of intramedullary pressure. The pressure levels were measured in plexiglass tubes filled with a mixture of vaseline and paraffin. The viscoelastic properties of this mixture at 20 degrees C were equivalent to those of bovine medullary fat at 36 degrees C. In comparison with the conventional reamer system (9.0 mm drive + 9.5 mm AO reamer), the 7.0 mm drive+AO reamer and the 7.0 mm drive+hollow reamer, the pressure values were reduced as follows: 1. 9.0 mm drive + 9.5 mm hollow reamer: diaphyseally by 19%, metaphyseally by 21% 2. 7.0 mm drive + 9.5 mm AO reamer: diaphyseally by 48%, metaphyseally by 49% 3. 7.0 mm drive + 9.5 mm hollow reamer: diaphyseally by 61%, metaphyseally by 66%. If the gap between the flexible shaft and the wall of the plexiglass tube became large enough, only small pressure values were recorded for all three types of reamer. In summary, it can be stated that the reduction of the drive diameter causes a sustained reduction in the intramedullary pressure, but that the newly developed hollow reamer only leads to a further reduction in pressure in combination with a thin flexible drive.

Equipment Design↗
PubMed1993

[Selection of treatment in femoral shaft fractures].

It is not possible and seems not reasonable to treat all kinds of femoral shaft fractures in the same way. Any type of osteosynthesis has its own advantages and disadvantages. The decision towards an operative procedure and the application of a special method depends on the individual situation of the patient and on the familiarity and experience of the orthopedic surgeon with the different available procedures. Single fractures, shaft fractures in combination with jointnear lesions, fractures in polytraumatized patients require a differentiated approach. Doubtless, nowadays the trend to treat all femoral shaft fractures by i.m. nailing is obvious. But it seems that there still exist a lot of indications where the plate or an external fixation can be used with remarkable advantages.

Femoral Fractures↗