Biomedical subjects

K Seide

Publications and source records attributed to K Seide.

15 recordsLinked to original sources

PubMed2006

Locked vs. unlocked plate osteosynthesis of the proximal humerus - a biomechanical study.

BACKGROUND: Locked plates (internal fixators) have been found to be an optimal method for the fixation in proximal humeral fractures. In a biomechanical cadaver study the difference between locked and non-locked osteosyntheses was investigated. METHODS: Paired humeri were harvested, bone density measured. Locked internal fixators were mounted on one specimen; identical plate-screw-systems without locking mechanism applied to the contralateral specimen for comparison. After that, a transverse subcapital osteotomy was performed. With 7 pairs of humeri static tests with increasing axial loads and with 5 pairs dynamic tests with 10 N preload and 80 N maximal axial load for up to 1 million cycles were performed. RESULTS: In the static experiments the elastic stiffness of the construct was 74% higher in the locked group (median 80 N/mm, quartile range 77-86 N/mm) compared with the non-locked group (46 N/mm, 35.5-56.5 N/mm). The difference was statistically significant (Wilcoxon test for paired samples, P<0.05). Similarly, the linear range until failure was definitely extended in the locked group by 64% (92 N, 89-98 N vs. 56 N, 36.5-73.5 N, P<0.05). Under dynamic loading the non-locked group showed fixation failures between 97,000 and 500,000 cycles. In the locked group no failure was observed until the end of the experiment at 1 million cycles (P<0.0.5). The final deformation was found to be 1 mm (median, quartil range 1.0-1.2 mm) in the non-locked group and 0.3 mm (0.2-0.3 mm) in the locked group (P<0.05). The differences were found equally in lower as well as in higher bone density specimen. INTERPRETATION: Because of the optimal load transfer between implant and cancellous bone, a locked screw plate interface will reduce fixation failure in proximal humeral fractures.

Biomechanical Phenomena↗

PubMed2006

[Fracture of the distal lower limb: two-stage surgical treatment with external fixator and locked-screw plate].

From January 1999 until October 2004 we treated 42 patients with closed fractures of the distal calf by a two-stage treatment plan: first the fracture was stabilized with an external fixator bridging the ankle joint. Second, after an average period of 8.3 days, an open reduction and internal fixation with a locked-screw implant followed. As complications we saw a superficial wound necrosis in 3 cases, 2 patients needed an early bone graft after insufficient bone healing and in one case a deep vein thrombosis of the thigh occurred. A deep infection or osteitis were not seen. 17 patients showed no deficit in the range of movement of the ankle joint compared to their opposite side, 21 patients had a deficit of movement of one third compared to the opposite side and 4 patients suffered from a deficit of (2/3). Radiologically we saw in 31 fractures of the pilon-tibiale in 19 cases no or only few arthrosis of the ankle joint, in 9 cases intermediate and in 3 cases advanced arthrosis. With a two-stage surgical treatment with external fixator and locked-screw implant we achieved a good functional result with only few complications.

Adult↗

PubMed2004

[Experiences in the treatment of midfacial fractures using a fixed-angle osteosynthetic system. Biomechanical results].

AIM: Fixed-angle osteosynthetic systems are characterized by mechanical "locking" of the osteosynthetic screw and plate. These systems have found increasing acceptance and use for osteosynthetic fixation and temporary reconstruction of the mandible. The aim of this study was to investigate the applicability and performance of fixed-angle systems in the treatment of midfacial fractures. MATERIAL AND METHOD: A newly developed fixed-angle osteosynthetic plate system (smart lock) was compared to a conventional system using fresh human skulls. The iatrogenically produced zygomatic fractures of the human skulls were treated by osteosynthesis and biomechanically tested. Furthermore, in a dynamic test series, an artificial bone was subjected to an alternating force of 15 N of up to 1,000,000 cycles. The new screws and plates were subjected to further biomechanical tests. RESULTS: The tests using the fixed-angle implants revealed that an increase of stability of up to 40% can be expected after osteosynthetic fixation. Furthermore, the plates resisted 1,000,000 cycles of alternating forces, whereby the conventional systems failed after 170,000 cycles on the average. CONCLUSION: Fixed-angle systems, due to their construction, provide a high degree of stability even in thin bones of the midface. They appear to be promising for the treatment of midfacial fractures.

Bite Force↗

PubMed2004

Three-dimensional load measurements in an external fixator.

On the basis of a six-degree-of-freedom adjustable fracture reduction hexapod external fixator, a system which can be used for measuring axial and shear forces as well as torsion and bending moments in the fixator in vivo was developed. In a pilot study on 9 patients (7 fresh fractures and 2 osteotomies of the tibia), the load in the fixator during the healing process was measured after 2, 4, 8 and 12 weeks and at fixator removal. The measured values enabled both the type of fracture to be determined as well as the monitoring of the healing process. In well-reduced type A3 fractures small axial (direction of the bone axis) forces were found in the fixator. A2, B2 and C3 fractures showed distinct axial forces, which decreased during the healing process, according to an increasing load transfer over the bone. Bending moments in the fixator showed good correspondence with the clinical healing process, except in the case of a C3 fracture. A combination of bending moment and axial force proved to be particularly suitable to assess fracture healing. In transverse fractures, the well-known resorption phenomenon of bone in the fracture gap at approximately 4 weeks was detected by the system. Compared with other external fixator load measurements in vivo, the hexapod offers the advantage of being able to measure all forces and moments in the fixator separately and with a relatively simple mechanical arrangement. In our opinion, it will be possible to control fracture healing using this system, thereby minimizing radiation exposure from radiographs. Furthermore, the measurement system is a step towards the development of external fixator systems that enable automatic adjustments of the callus mechanical situation ("automatic dynamization") and inform the patients about the optimal weight bearing of their extremity ("intelligent fixator").

Equipment Design↗

PubMed2004

Quadriceps tendon ruptures-is there a complete functional restitution?

From January 1986 to November 1999, 35 patients with 36 traumatic ruptures of the quadriceps tendon, all without medical risk factors, were treated (33 men, 2 women; mean age 55 years). Thirty patients were operated within 14 days after trauma. With an average follow up of 55.4 months (7-168) 29 of 30 still living patients (96.7%) were studied retrospectively. Questionnaire (Lysholm score), physical examination, X-ray of both knees and isokinetic testing were performed. The outcome was significantly (P < 0.001) dependent on the time of operative procedure. Twenty-four patients treated within the first 14 days had 20 excellent and 4 good results, the other 5 one good, 1 satisfying and 3 poor results. Twenty-one of 23 patients (91%) could return to work. The type of repair (direct or transosseous suture with or without augmentation), the kind of postoperative physiotherapy, the age and the body mass index had no influence on the final outcome.

Adult↗

PubMed2004

Prevention of thromboembolism with low-molecular-weight heparin in orthopedic surgery: a 5-year experience.

A regimen of prophylaxis of thromboembolism with low molecular weight heparin (LMWH) and unfractionated heparin (UFH) in orthopedic surgery is presented. Over a 5-year period, 11,905 patients have been operated in all fields of orthopedic surgery in a big trauma center. In 498 cases, deep vein thrombosis (DVT) was clinically suspected and phlebography was performed: 122 patients had confirmed DVT (rate 0.98%); 59.8% of the DVT were limited to the calf. Nineteen pulmonary embolisms (rate 0.16%) were diagnosed (3 lethal). Heparin-induced thrombocytopenia type II was diagnosed in 12 of 122 patients. Only one of these had received LMWH. The related rates of DVT were highest for tibial head fractures (12.4%), total knee replacement (6.7%), and multiple trauma (6.4%). The extent of DVT was most severe in multiple trauma. The results proved the regimen to be of good clinical use and showed that more attention has to be paid to fractures, especially of the knee; and to patients with multiple injuries.

Adolescent↗

PubMed2002

[Theory and software of the hexapod external fixator].

Using hexapod kinematics (Stewart platform), an external fixator was developed that can be adjusted in all six spatial degrees of freedom by means of six linear adjusting elements. With such a system, any desired three-dimensional bone movements, for example, fracture reduction or deformity correction, can be effected exactly, without having temporarily to compromise any stability already achieved or to rearrange the construction during treatment. Since the introduction of the hexapod principle by Stewart in 1965, computerized control has been deemed necessary for its application. This paper describes the mathematical basis and the software developed for clinical use. Mathematical procedures are needed for the calculation of the inverse and forward kinematics of the hexapod, and for the description of three-dimensional movements.

Biomechanical Phenomena↗

PubMed2000

[Corrections using the hexapod].

The hexapod is a construction that has been subjected to a great deal of investigation in robotics for use in three-dimensional positioning. One use of it is for positioning of the cockpit in flight simulators. Application of the hexapod principle in the external fixator makes it possible to realize prescribed movements of bone fragments with a simple and stable design. The precise setting of the system requires software that has been developed and optimized for clinical use. Translations, axis corrections and rotations are possible individually and also in combinations for correction of complex deformities. The system has advantages, especially in the case of rotations around the longitudinal axis of the bone and in the realization of translation movements. Because the centres of rotation are taken into account by the mathematical calculations, the planning of corrections is simplified. The hexapod system is described, and its clinical application is presented with reference to case reports.

Adult↗

PubMed1999

Fracture reduction and deformity correction with the hexapod Ilizarov fixator.

A configuration for the Ilizarov external fixator with six distractors and 12 ball joints in the form of a hexapod was developed. The system allows for six degrees of freedom bone fragment displacement by controlling the distractors. Using this assembly, universal three-dimensional corrections or reductions are possible without the need for complicated joint mechanisms. The device was used in 16 patients: five had displaced tibial fractures with severe soft tissue damage, 10 had deformities or pseudarthroses subsequent to treatment of tibial fractures, and one had an axis deviation in the course of tibial lengthening. Translational (to 40 mm) and rotational deformities (to 33 degrees) were corrected. Final radiographic examinations after the correction procedure was complete showed median residual deformities of 3.5 mm (range, 0-5 mm) and 1 degree (range, 0 degree-4 degrees) in the anteroposterior projection and of 1.5 mm (range, 0-6 mm) and less than 1 degree (range, 0 degree-9 degrees) in the lateral projection. The construction is a useful and important addition to the Ilizarov fixator system. As a bone fixation device it is unique in that its optimal use depends on the availability of computer software.

Adolescent↗

PubMed1996

[Universal 3-dimensional correction and reposition with the ring fixator using the hexapod configuration].

A new configuration for the Ilisarov fixator with 6 distractors and 12 ball joints in the form of a hexapod is proposed. Using this assembly, a correction or reduction is possible with respect to any given point and axis in space. The primary position of the rings is not critical. The fixator system is statically determined and there is no stress between the longitudinal rods. Difficult corrections like those necessary for rotational deformities can be done without complicated joint mechanisms.

Biomechanical Phenomena↗

PubMed1996

[Significance of isthmic spondylolisthesis in expert assessment of occupational disease of the lumbar spine].

In Germany, disc-related disease of the lumbar spine is eligible for workmen's compensation if caused by long-standing work requiring heavy lifting or carrying or extreme trunk-bending (BK 2108). The appraisal of causality is particularly difficult if conditions like isthmic spondylolisthesis preexist. 250 consecutive appraisals in nurses concerning the BK 2108 were analysed, 12 applicants (4.8%) had isthmic spondylolisthesis (4.6% of females and 5.9% of males). The literature about the natural history of isthmic spondylolisthesis is reviewed. A person who has isthmic spondylolisthesis is up to 25% more likely to have significant back trouble during his life than one who does not. Back pain in adults associated with spondylolisthesis is usually heralded by back pain in the late teens or early twenties. Progression of the slip is rarely seen after maturity. Due to the loss of protection by the posterior elements the disc is prone to premature degeneration which, however, does not become clinically apparent in most cases. Longstanding vocational heavy lifting or excessive stooping can negatively influence the natural history of isthmic spondylolisthesis. It can produce symptomatic disease in a person who would otherwise have remained asymptomatic, or it can cause a deterioration in those with preexisting symptoms. Criteria for the appraisal of causality are proposed. It is stressed that the course of the disease in relation to age and vocational strains has to be analysed in each individual case.

Adolescent↗

PubMed1992

[Standardized ultrasound study with computer-assisted documentation of findings in diagnosis of polytrauma patients].

Based on the results of a prospective trial to establish the value of routine ultrasound examination in cases of polytrauma or blunt abdominal trauma, we report on our standard ultrasound examination and computer assisted documentation of the findings. Between May 1988 and December 1990 we examined 233 patients with polytrauma or blunt abdominal trauma. The results were compared with those of abdominal lavage (n = 47) performed during the same period. We found a sensitivity of 100% and a specificity of 99.5% for the ultrasound findings and a sensitivity of 80% and a specificity of 100% for the abdominal lavage. We conclude that ultrasonography should be the first diagnostic procedure used in the emergency room in cases of polytrauma and blunt abdominal trauma.

Abdominal Injuries↗

PubMed1990

[The effect of an angle-stable plate-screw connection and various screw diameters on the stability of plate osteosynthesis. An FE model study].

In a finite element model of a human femur with an attached stainless steel six-hole plate exposed to a load equivalent to that set up by standing on one leg, pressures on the face of the screw holes, bending stresses in the screws, and axial bone stresses in the mid-plate transverse section were determined. The calculations were performed for minor thread diameters of 3 mm, 5 mm and 8 mm. Further calculations were done assuming a fixator-like rigid screw-plate connection. As a model of a fracture a medial bone defect was chosen. The results show a definitive influence of the screw diameter and the screw-plate connection on the load distribution in the system. Increasing screw diameter makes for lower bone stresses combined with increased bending stability, a larger part of the load being carried by the plate. The rigid screw-plate connection (plate fixator) causes less bone stresses, but high bending stresses are set up the points of screw-plate fixation. Maximal stresses for screw and bone are found at the end of the plate, caused by the large difference in the E-module between the steel plate and the bone. End-plate bone and screws are loaded in excess of their material limits when 3 mm core diameters are used, and sometimes when 5 mm core diameters are used, under the assumed conditions. When a medial bone defect reducing the bone cross-sectional area by 44% is present, the loads on the inner screws increase by a factor of 3 and the loads of the distant screws, by a factor of only 1.3. The maximal pressure in the bone cross section increases 4-fold.

Biomechanical Phenomena↗

PubMed1984

Three-dimensional dynamic x-ray-computed tomography imaging of stomach motility.

The dynamic spatial reconstructor (DSR), an x-ray-computed, tomography-based imaging machine, scans a cylindrical volume up to 39 cm in transaxial diameter and 21.5 cm in axial height with scan repetition rate up to 60 per second. We applied this technique to three dogs in order to investigate the accuracy with which stomach shape, dimensions, and motility can be measured. Single peristaltic waves of one dog's stomach filled with air and two other dogs' stomachs filled with different volumes of contrast-enhanced semisolid meals (10% Gastrografin) were scanned at 2-s intervals at scan apertures between 0.011- and 1-s duration. On completion of the scan sequence, images of oblique sections perpendicular to the local long axis of the stomach fundus, corpus, and antrum were computed from the DSR scan data. Measurements of differential motion of defined points on the stomach wall surface, propagation velocities, acceleration, and amplitudes of peristalsis as well as gastric volume determinations were made. This approach overcomes problems of superposition and ambiguity inherent in projection imaging. Measurements of the volumes of ingested first meal were accurate to within 1.5% (of the actual volume of solid food introduced into the stomach) using a 0.40-s scan aperture. Wall motion could be detected with an SEE of 1.5 mm (pixel size used was 1.4 mm) using a 0.40-s scan aperture.

Animals↗

PubMed1982

The influence of tilidine and prazepam on withdrawal reflex, skin resistance reaction and pain rating in man.

Pain rating, withdrawal reflex and skin resistance reaction upon electrical skin stimuli were studied on 15 male volunteers under placebo, tilidine and prazepam. Tilidine (Valoron) is an orally applicable narcotic analgesic, with a mode of pain relief presumably similar to morphine; the tranquilizer prazepam (Demetrin) belongs to the benzodiazepine group. Significant reduction in all measured reaction amplitudes was found under tilidine, whereas prazepam reduced significantly only the skin resistance reaction. The relative drug-induced changes in reaction amplitudes, related to the corresponding placebo value, were independent of stimulus intensity for all investigated reactions. Therefore, fitted power functions re = a . Sn between reaction amplitudes re and stimulus intensity S showed a decrease in parameter a under the investigated drugs, whereas the exponent n remained constant. High correlations between parameters a and corresponding reciprocal threshold currents could be shown for all reactions measured. Furthermore the drug-induced changes of withdrawal reflex amplitude and of subjective estimation were found to be correlated over subjects. In contrast, no correlations were found between variations in skin resistance reaction and magnitude estimation due to the selected drugs, i.e., the influence of the drugs on the sensory component of pain sensation and on the skin resistance reaction were independent effects.

Analgesia↗