Q112351310
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To compare the anchorage strength of Socon CS cannulated pedicle screws (B. Braun, Aesculap) with that of Socon screws in human cadaver vertebrae, using pull-out strength testing. MATERIAL Twelve samples involving T12 to L3 vertebrae were prepared and a total of 20 pedicle screws, 10 Socon CS and 10 Socon screws, were inserted in them. All screws were 55 mm in length and 6 mm in diameter. After placement, Socon CS pedicle screws were augmented with bone cement (Cimplant cement application kit, B. Braun, Aesculap). METHODS Both Socon CS and Socon screws were subjected to monotonous loading in the testing device ZWICK Z 020-TND with tensile stress applied in the screw axis. We evaluated the magnitude of strength resulting in screw loosening and the relationship between this strength and bone density of the sample. RESULTS Bone density of measured samples corresponded either to osteopenia, i.e. T-score range of -1 to -2.5 SD (standard deviation) or osteoporosis, i.e. T-score -2.5 SD. The average bone density of all samples corresponded to a T-score of -3.1 SD. Bone-screw linkage was found to be associated with both bone-cement and screw-cement interface. Pull-out strength was significantly higher for the Socon CS than the Socon screws (t-test, p<0.0005). In the Socon screws, the linear correlation between pull-out strength and bone density was significant at a 5% level of statistical significance (p=0.008) while, in the Socon CS screws, it was not significant (p=0.065). DISCUSSION The poor quality of osteoporotic bone is responsible for a higher frequency of implant failure due to loosening, particularly when implants developed for healthy bone are used. In this biomechanical study, we tested one of the possibilities of how to reduce the risk of implant failure by pedicle screw augmentation with bone cement. CONCLUSIONS The results of this study confirm the hypothesis that the anchorage of Socon CS cannulated pedicle screws with bone cement augmentation is disrupted by significantly higher pull-out strength than that of Socon screws, when subjected to monotonous loading. However, more clinical studies are needed to evaluate clinical outcomes
- MeSH
- bederní obratle chirurgie patofyziologie zranění MeSH
- biomechanika MeSH
- fraktury páteře chirurgie patofyziologie MeSH
- hrudní obratle chirurgie patofyziologie zranění MeSH
- kostní denzita MeSH
- kostní šrouby MeSH
- lidé MeSH
- mrtvola MeSH
- osteoporotické fraktury chirurgie patofyziologie MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- techniky in vitro MeSH
- Check Tag
- lidé MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- Publikační typ
- srovnávací studie MeSH
Aims. It is possible to reconstruct the elbow motion in tetraplegic patients using the posterior portion of the deltoid muscle. In this surgery however, it is a problem to achieve a firm suture between the deltoid muscle and the tendon graft which extends the muscle and is sewn in order to compensate for the plegic musculus triceps brachii function. This study assesses two methods of attachment between muscle and free tendon graft from the biomechanical point of view. Methods. The assessment was made on 7 fresh-frozen cadaveric samples where the rear portion of the deltoid muscle was sewn with the strip of fascia lata (A1-A7) and 7 samples (B1-B7) where the free tendon graft was attached with a strengthened part of deltoid fascia. The character of the attachment defect was evaluated as strength and elongation parameters using the device Zwick Z020-TND. Results. The ANOVA showed a statistically significant greater suture solidity connecting the muscle and tendon for group B (B1-B7) than group A. The deformation of the actual suture location was smaller in group B than the deformation of attachment surroundings. Conclusion. From the biomechanical solidity point of view, it is more efficient to use the strengthened fascia of the deltoid muscle on its inner side for the suture with the tendon graft for reconstruction of the elbow extension in tetraplegic patients.
Background. The aim of the experiment was to compare the mechanical properties of intact spinal segment with impaired intervertebral disc and impaired intervertebral disc fixed by TSLP (Thoracolumbar Spine Locking Plate). Methods and results. Spinal specimens were taken from domestic swine. A total of 8 test mechanical states (intact, impaired and fixed) were modeled and the mechanical properties, expressed by the value of moment of couple necessary to twist the specimen at tensile force F = 200 N and the value of moments necessary for extension straining, were determined. The study was based on in vitro biomechanical testing of the TSLP plate used to stabilize the front thoracolumbar column of spinal segments taken from a pig. The plate was used for monosegmental fixation. The disc was cut by scalpel to simulate the Type A injury to front spinal column. In each state (intact, impaired or fixed), specimens were subjected to a tension load of prescribed force and, then, twisted by a given angle. Subsequently, extension load of intact, impaired and impaired & fixed segment was measured. Statistical evaluation verified the hypothesis of the different behavior of intact, impaired and fixed specimens – both for tension & torsion load and extension load. The analyses did not indicate different mechanical behavior of intact and fixed specimens. In other words, monosegmental fixation of both impaired and intact specimens by TSLP Synthes implant will lead to similar mechanical behavior of these specimens. Further, we found that intact and fixed specimens show non-symmetric behavior at positive and negative twisting angles. This was not observed for impaired specimens. Conclusion. Several stabilization systems were developed to stabilize the front thoracolumbar spinal column. Surgery of the anterior column of injured spine should restore the correct position of the spine, ensure decompression of vertebral canal when neural structures are compressed, and stabilize the spine to allow immediate loading and mobilization of the patient. The aim of this study was to compare mechanical properties of intact spinal segment, impaired spinal segment and impaired spinal segment stabilized by TSLP Synthes implant. The problems were solved by experimental modeling using a testing machine that simulated loads for several mechanical states of the spinal segment. Favorable mechanical properties of TSLP Synthes fixator were demonstrated. The experimental results will be used for subsequent computational modeling of the spinal segment in all experimentally solved states.
An unusual case of implant failure after revision total knee arthroplasty (TKA) is presented and the case report is completed with the results of an ensuing biomechanical study made to explain possible causes leading to a fracture of the tibial stem. For this we used electron microscopic and biomechanical analyses. There was no material defect found at the site of fracture. By computerized modelling of the clinical situation, however, we found out that asymmetrical progressive osteolysis of the proximal tibia could have caused significant changes in mechanical straining associated with qualitative alterations in the process of degradation and erosion of the implant, eventually leading to a fracture of the tibial stem. In this way mechanical straining at the site of fracture could have exceeded the failure threshold of titanium alloy. Stem fracture of a current tibial component design has not yet been described in the literature. The only failure so far reported concerns the stem of a femoral component, and this has also been explained by biomechanical reasons. It follows from this study that patients with progressive osteolysis around the TKA should be followed up more frequently. The conclusions of this biomechanical analysis emphasize the importance of a thorough reconstruction of bone defects in order to improve long-term survival of the implant.
- MeSH
- biomechanika MeSH
- financování organizované MeSH
- fraktury tibie etiologie chirurgie patofyziologie MeSH
- lidé MeSH
- osteolýza etiologie komplikace MeSH
- reoperace MeSH
- selhání protézy MeSH
- senioři MeSH
- totální endoprotéza kolene škodlivé účinky využití MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- Publikační typ
- kazuistiky MeSH
To evaluate the results of primary total hip replacement with the CLS acetabular cup at a minimum of 15 years of follow- up. MATERIAL AND METHODS A total of 105 patients, with 112 hips, undergoing hip arthroplasty with the use of CLS acetabular cup between 1991 and 1993 were evaluated. The group comprised of 33 men and 72 women with an average age of 51.3 years (range, 28 to 66) at the time of surgery. All patients received the CLS expansion cup with a polyethylene Sulen-type liner. Cemented femoral stems were used in 75 hips and uncemented CLS stems were implanted in 37 hips. Ceramic heads of the femoral component were used in 86 hips and metal heads were used in 26 hips. The clinical outcome was assessed by the Merle dAubignnd Postel score and the Harris hip score, and the radiological results were evaluated on anterior posterior X-ray films of the pelvis and the affected hip. RESULTS The average follow-up was 16.2 years (range, 15 to 17). The average Merle dAubignnd Postel score increased from 8.1 (range, 5.7 to 9.8) pre-operatively to 14.6 (range, 14.1 to 16.8) post-operatively. The average Harris hip score improved from 42 to 86 points (range, 71 to 99). The complications requiring revision arthroplasty included aseptic loosening in two hips, fracture of the CLS shell in three, dislocation in three and replacement of the liner due to high wear in two hips. The cumulative proportion of clinical survivorship with revision for any reason was 92 %. Fixation by bone ingrowth, assessed by the method of Engh et al. occurred in 98 cases, fibrous tissue fixation was found in ten hips. Unstable fixation was recorded in four hips (two with aseptic loosening and two with fracture of the shell). There were no signs of rarefaction of bone along acetabular shell in 98 hips. No noticeable migration was found in the stable cups. Only in ten cups from 112, polyethylene wear exceeded 4 mm. Cumulative probability of radiological survivorship of the CLS acetabular cup with any radiological sign of loosening was 86.6 %. DISCUSSION The causes of fracture of the CLS cup can be explained by insufficient bone support or bone resorption in the proximallateral part of the acetabulum in patients with developmental hip dysplasia, by low bone quality due to severe osteoporosis or by insufficient primary stability of the cup. The advantages of the CLS cup include removal of a small amout of bone and favourable force distribution in circumferential anchorage. The cup showed good osteointegration even in a bone of lower quality and with defects of the acetabular bottom. CONCLUSIONS The CLS acetabular cup shows good results at 16-year follow-up period. No increase in fractures of the shell, migration or radiolucent lines, or in bone rarefaction or osteolysis was recorded with time. The reliability of this implant has been recently increased with the use of cross-linked polyethylene (Durasul). Key words: primary total hip replacement, uncemented cup.
- MeSH
- acetabulum MeSH
- dospělí MeSH
- kyčelní kloub radiografie MeSH
- kyčelní protézy MeSH
- lidé středního věku MeSH
- lidé MeSH
- náhrada kyčelního kloubu škodlivé účinky MeSH
- následné studie MeSH
- reoperace MeSH
- selhání protézy MeSH
- senioři MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
Příspěvek uvádí výsledky experimentálních studií použitelných v klinické ortopedii, které byly realizovány v Ústavu mechaniky těles, mechatroniky a biomechaniky, Fakulta strojního inženýrství VUT v Brně. Jedná se o tyto experimentální studie: určování mechanických vlastností Kesslerova jedno- a víceramenného šlachového stehu, vliv augmentace Socon šroubů na jejich únosnost, chování páteřního segmentu s neporušenou/porušenou ploténkou (fixátor TSLP), pevnostní problematika kliček a páteřních háčků u operačních postupů podle Luqueho a Galvestonea, určování mechanických vlastností vysokomolekulárního polyetylenu pro výpočtové modelování chování totálních kolenních endoprotéz.
The paper presents results of experimental studies applicable in clinical orthopedics which were carried out at the Institute of Mechanics of Solids, Mechatronics and Biomechanics at Brno University of Technology, Faculty of Mechanical Engineering. This concerns in particular the following experimental studies: determination of mechanical properties of Kessler's tendon sutura, influence of Socon screws augmentation on their limit load, behaviour of spinal segment with both normal and defective spinal disc (TSLP fixator), structural problems of sublaminar wires and pedicular hooks in Luque and Galvestone surgery protocols, determination of mechanical quality of macromolecular polyethylene used in computer simulation of total knee endoprothesis.
- MeSH
- biomechanika MeSH
- financování organizované MeSH
- fraktury páteře MeSH
- klinické zkoušky jako téma MeSH
- kostní šrouby MeSH
- lidé MeSH
- matematické výpočty počítačové MeSH
- modely strukturální MeSH
- mrtvola MeSH
- ortopedie metody MeSH
- osteoporóza MeSH
- polyethyleny MeSH
- poranění šlachy MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- grafy a diagramy MeSH
- srovnávací studie MeSH
V příspěvku se autoři zamýšlí nad současnou situací biomechaniky u nás. Dále je zde uvedena struktura biomechaniky a struktura biomechanických problémů. Je zde stručně pojednáno i o modelování, jako prostředku k řešení problémů. Závěr příspěvku je věnován diskuzi pojmů soustava a systém, které se nejenom v medicíně používají ve vágních významech.
In the paper the authors think about the actual situation of biomechanics in our country. A systemization of biomechanics and biomechanical problems is presented. The paper deals with modelling as an instrument for problem solution. The paper ends with a discussion regarding the concept of real and abstract systems, which are used in vague meanings not only in medicine.
