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Biomedical subjects

W Puhl

Publications and source records attributed to W Puhl.

At least 19 recordsLinked to original sources
PubMed2003

The migration of femoral components after total hip replacement surgery: accuracy and precision of software-aided measurements.

OBJECTIVE: To assess the accuracy and precision of a software-aided system to measure migration of femoral components after total hip replacement (THR) on digitised radiographs. DESIGN AND PATIENTS: Subsidence and varus-valgus tilt of THR stems within the femur were measured on digitised anteroposterior pelvic radiographs. The measuring software (UMA, GEMED, Germany) relies on bony landmarks and comparability parameters of two consecutive radiographs. Its accuracy and precision were calculated by comparing it with the gold standard in migration measurements, radiostereometric analysis (RSA). Radiographs and corresponding RSA measurements were performed in 60 patients (38-69 years) following cementless THR surgery. RESULTS AND CONCLUSIONS: The UMA software measured the subsidence of the stems with an accuracy of +/-2.5 mm and varus-valgus tilt with an accuracy of +/-1.8 degrees (95% confidence interval). A good interobserver and intraobserver reliability was calculated with Cronbach's alpha ranging from 0.86 to 0.97. Measuring the subsidence of THR stems within the femur is an important parameter in the diagnosis of implant loosening. Software systems such as UMA improve the accuracy of migration measurements and are easy to use on routinely performed radiographs of operated hip joints.

Adult↗
PubMed2003

Surface composition analysis of failed cementless CoCr- and Ti-base-alloy total hip implants.

The surfaces of retrieved failed cementless total hip implants made of cobalt-chromium-molybdenum casting alloy and of wrought titanium 6-aluminum 4-vanadium alloy were studied with the use of scanning-electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). New implants of the same make served as controls. The XPS scans revealed a dense carbon layer on the entire analyzed specimen. The relative composition of the titanium alloy implants showed an overall agreement with the international standards for implants for surgery, and the overall surface composition did not change over the period of the implantation. However, an inhomogeneous distribution of the constituents could be demonstrated in the retrieved as well as in the new MEC-screw rings made of TiAl6V4 alloy, an implant that has been linked to a high early failure rate. In the CoCr-alloy components (Lord-screw rings) a high percentage of aluminum, mainly organized in aluminum inclusions, was found in the retrieved as well as in the new implants.

Adult↗
PubMed2003

International variation in hip replacement rates.

OBJECTIVES: To summarise epidemiological data on the frequency of hip replacements in the countries of the developed world, especially in countries of the Organisation for Economic Cooperation and Development (OECD), and to investigate whether missing consensus criteria for the indication for total hip replacement (THR) result in different replacement rates. METHODS: Country-specific hip replacement rates were collected using the available literature, different data sources of national authorities, and estimates of leading hip replacement manufacturers. RESULTS: According to administrative and literature data sources the reported crude primary THR rate varied between 50 and 130 procedures/100000 inhabitants in OECD countries in the 1990s. The crude overall hip implantation rate, summarising THR, partial hip replacement, and hip revision procedures, was reported to range from 60 to 200 procedures/100000 inhabitants in the late 1990s. Moreover, large national differences were seen in the relationship between total and partial hip replacement procedures. CONCLUSION: The reported differences in hip replacement rates in OECD countries are substantial. They may be due to various causes, including different coding systems, country-specific differences in the healthcare system, in total expenditure on health per capita, in the population age structure, and in different indication criteria for THR.

Age Factors↗
PubMed2002

[Neon--a new angle-stable implant system for dorsal occipitocervical instrumentation. Biomechanical comparison with established systems].

Posterior instrumentation of the occipitocervical spine is well-established for different indications. The aim of this study was to evaluate whether posterior internal fixation of the occipitocervical spine with the new implant system improves primary biomechanical stability. Primary stability was significantly increased in all load cases with the new modular implant system compared to the other implant systems. Pedicle screw instrumentation tended to be stabler compared to lateral mass screws; nevertheless, significant differences could be observed only for lateral bending. As the experimental design precluded any cyclic testing, the data represent only the primary stability of the implants. In summary, this study showed that posterior instrumentation of the cervical spine using the new neon occipito-cervical system improves primary biomechanical stability compared to the CerviFix system and the Olerud cervical rod spinal system.

Aged↗
PubMed2002

[Computer navigation in dorsal instrumentation of the cervical spine--an in vitro study].

Transarticular C1/2 screws are widely used in posterior cervical spine instrumentation. Pedicle screws in the cervical spine remain uncommon until now. In view of improved biomechanical stability compared to lateral mass screws, pedicle screws could be used, especially for patients with poor bone quality or defects in the anterior column. Nevertheless, there are potential risks of iatrogenic damage to the spinal cord, nerve roots, or the vertebral artery related to both techniques of posterior cervical spine instrumentation. Therefore, the aim of this study was to evaluate whether C1/2 transarticular screws as well as transpedicular screws in C3 and C4 can be applied safely and with high accuracy using a computer-assisted surgery (CAS) system. C1/2 transarticular screws as well as transpedicular screws in the cervical spine can be applied safely and with high accuracy using a CAS system in vitro. Therefore, this technique may be used in the clinical setup due to improved accuracy and reduced radiation dose for the patient and medical staff. Nevertheless, to prevent iatrogenic damage, users should be aware of known sources of possible errors that cause inaccuracies. Small pedicles with a diameter below 4.0 mm may not be suitable for pedicle screws.

Aged↗
PubMed2002

[Preliminary results in the therapy of psoriatic arthritis with mycophenolate mofetil].

BACKGROUND: Psoriatic arthritis concerns both the skin and the joints. Therapeutic interventions should therefore ideally improve both symptoms. Current disease modifying drugs are effective; however, they are usually limited to either psoriasis or arthritis. AIM OF THE STUDY: The aim of this study was to analyze the therapeutic effects of a new immunosuppressive drug (Mycophenolate mofetil) in the treatment of psoriatic arthritis. METHODS: Six patients with psoriatic arthritis were treated with Mycophenolate mofetil for a period of 12 weeks and examined every 14 days (range of motion, joint swelling, joint deformity, PASI score (Psoriasis Area and Severity Index). In addition, a life quality assessment (SF-36 Health Survey) was performed. White and red blood count as well as inflammation parameter were controlled regularly. RESULTS: 6 patients could be included in a complete follow-up (5 men, 1 woman, average age 50.3 years, average duration of psoriasis 8.3 years, average duration of arthritis 5.7 years). Four of 6 patients showed relevant improvement in pain, mobility and degree of psoriatic skin effluorescences. Only 3 of 6 showed relevant improvement in life quality. CONCLUSION: For the first time results of treatment of psoriatic arthritis with a new immunosuppressive drug (Mycophenolate mofetil) were presented. A positive influence on both, the arthritis and the psoriasis could be shown. These first observations warrant controlled, randomized clinical trials.

Adult↗
PubMed2002

[Clinical epidemiology of hip and knee joint arthroses: an overview of the results of the "Ulm Osteoarthrosis Study"].

AIM OF STUDY: To summarize the strategy of patient recruitment, applied methods and published results within the Ulm Osteoarthritis Study, a multicenter cross-sectional survey of patients with advanced hip and knee osteoarthritis. METHODS: 420 patients with hip OA and 398 patients with knee OA scheduled for unilateral total joint replacement in four hospitals in the southwestern part of Germany underwent detailed clinical investigations and a standardized interview in addition to radiographic analyses of ipsilateral and contralateral hip or knee joint and both hands. Odds ratios and 95% confidence intervals for the association of different possible risk factors with OA patterns (unilateral, bilateral and generalized OA) were calculated with logistic regression, adjusting for potential confounders. RESULTS: In 41.7% of patients with hip OA and 33.4% of patients with knee OA, an underlying pathological condition allowed a classification as secondary OA. 82.1% of patients with hip and 87.4% of patients with knee OA had bilateral disease. Generalized OA (GOA) was found in 19.3 and 34.9%, respectively (after adjustment for different age and sex distribution in the two patient groups; however, this difference was not any more significant). A positive association could be observed between hypercholesterolemia and GOA in knee OA patients as well as between serum uric acid and GOA in hip OA patients. Obesity and overweight were associated with bilateral knee OA, but not bilateral hip OA nor GOA. DISCUSSION: Our innovative study design allows the non-invasive investigation of patient subgroups with established disease and a testing of relevant hypotheses in an appropriate setting. The data add to the evidence regarding the independent role of different systemic risk factors for OA. In an ongoing study the natural course of the disease of the contralateral, unoperated joint is currently being investigated in all recruited patients.

Adult↗
PubMed2002

Vascular endothelial growth factor stimulates chemotactic migration of primary human osteoblasts.

Recent studies have indicated a critical role for vascular endothelial growth factor (VEGF) during the process of endochondral ossification, in particular in coupling cartilage resorption with bone formation. Therefore, we studied the chemoattractive and proliferative properties of human VEGF-A on primary human osteoblasts (PHO) and compared these data with the effects of human basic fibroblast growth factor (bFGF) and human bone morphogenetic protein-2 (BMP-2). Furthermore, initial experiments were carried out to characterize VEGF-binding proteins on osteoblastic cells possibly involved in the response. For the first time, to our knowledge, we could demonstrate a chemoattractive effect of VEGF-A, but not VEGF-E, on primary human osteoblasts. The effect of VEGF-A was dose-dependent and did not reach a maximum within the concentration range tested (up to 10 ng/mL). The maximal effect observed was a chemotactic index (CI) of 2 at a concentration of 10 ng/mL. bFGF and BMP-2 exhibited maxima at 1.0 ng/mL with CI values of 2.5 and 2, respectively. In addition to its effect on cell migration, VEGF-A stimulated cell proliferation by up to 70%. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed the expression of VEGF receptors VEGFR-1 (Flt-1), VEGFR-2 (Kdr), and VEGFR-3 (Flt-4), as well as neuropilin-1 and -2. An in vitro kinase assay failed to demonstrate activation of VEGFR-2 upon stimulation with either VEGF-E or VEGF-A, consistent with the idea that the effect of VEGF-A on primary human osteoblasts is mediated via VEGFR-1. Taken together, our data establish that human osteoblasts respond to VEGF-A, suggesting a functional role for this growth factor in bone formation and remodeling.

Aged↗
PubMed2002

Lipofection of rabbit chondrocytes and long lasting expression of a lacZ reporter system in alginate beads.

OBJECTIVE: Our aim was to investigate the maintenance of the transfection status of non-viral transfected chondrocytes in an alginate culture system. DESIGN: Chondrocytes harvested from rabbit knees were isolated by sequential digestion and cultivated in monolayer culture. At 60-70% cell density, chondrocytes were transfected with different transfection systems (FuGENE6, CaCl2, Lipofectin). A lac Z expression vector (pcDNA 3.1/Myc-His+ lacZ) was used as a reporter system. In order to improve transfection rates, hyaluronidase (4 U/ml) was used prior and during the transfection procedure. Thereafter, transfected cells were either kept in monolayer culture or embedded in alginate beads and kept in culture for up to the next 30 weeks. RESULTS: Transfection efficiency was maximal using FuGENE6TM/DNA at a ratio of 3:2 and hyaluronidase (4 U/ml). Transfection efficiency reached up to 40.8% (+/- 3.2%) after 36 h. In alginate beads lac Z positive cells declined to 8.5% +/- 3.3% after 4 weeks and to 4.6% +/- 3.2% after 12 weeks of culturing. After 30 weeks 3% of chondrocytes still expressed lac Z. In contrast, during culturing in monolayer, no lac Z expression was detectable after 4 weeks. Differentiation status of the chondrocytes was confirmed by histology and immunohistochemistry methods. CONCLUSIONS: After successful gene transfer to rabbit chondrocytes the alginate system made it possible to culture lipofected chondrocytes phenotypically stable. Genetically engineered chondrocytes express the lac Z reporter gene over a period of at least 30 weeks. This transfection and culture system provides a promising tool to further investigate the over-expression of growth factors and enzyme inhibitors.

Alginates↗
PubMed2002

Expression of collagen type I, II, X and Ki-67 in osteochondroma compared to human growth plate cartilage.

In order to characterize the consequences for the process of endochondral ossification we performed an immunohistochemical study and compared the expression of collagen type I, II and X as markers of cartilage differentiation and Ki-67 as a marker of cell proliferation in solitary (7-26 years, n=9) and multiple (11-42 years, n=6) osteochondromas with their expression in human fetal and postnatal growth plates. In fetal and young postnatal controls, we found a thin superficial layer of articular cartilage that stained positive for collagen type I while collagen II was expressed in the rest of the cartilage and collagen type X was restricted to the hypertrophic zone. Osteochondromas from children showed lobular collagen type II-positive areas surrounded by collagen type I. In adults, the separation of collagen type I- and type II-positive areas was more blurred, or the cartilaginous cap was missing. Collagen type X was detected in a pericellular distribution pattern within hypertrophic zones but also deeper between bone trabecula. The proliferative activity of osteochondromas from children younger than 14 years of age was comparable to postnatal growth plates, whereas in cartilage from individuals older than 14 years of age, we could not detect significant proliferative activity.

Adolescent↗
PubMed2001

Proliferation and differentiation rates of a human osteoblast-like cell line (SaOS-2) in contact with different bone substitute materials.

The aim of our study was to investigate the influence of four bone substitutes on the growth behavior of a human osteoblast-like cell line (SaOS-2) culture: pure alpha tricalcium phosphate (alpha-TCP = BIOBASE), a bioactive glass (bioglass), a neutralized glass-ceramic (GB9N), and solvent dehydrated bone. We established an in vitro cell culture model with three-dimensional scaffolds (cubes of 0.7 x 0.7 x 1.0 cm) of porous bone substitutes to investigate proliferation and differentiation rates of SaOS-2 cells. The cultures were analyzed for individual cell morphology after 5 days of growing using scanning electron microscopy. Fracture preparations of the cubes showed that cells could infiltrate the porous structures, but the cell shapes varied from individual round-shaped cells to wide spread cells and cell clusters, depending on the material. Also, the differentiation of the seeded cells was dissimilar after a 5-day incubation. The specific alkaline phosphatase (ALP) enzyme activity (ALP/DNA) measured in the supernatants of alpha-TCP-grown cells was nine times higher than the lowest activity, as observed by cells incubated on GB9N. Early (Collagen1, ALP) and late marker (osteocalcin, bone sialoprotein) of osteoblastic differentiation were proofed by reverse transcriptase-polymerase chain reaction analysis. Cells grown on bone substitutes and bioglass seem to be less differentiated than alpha-TCP-grown cells, because of noticeably less amounts of osteocalcin and bone sialoprotein. The cultivation on GB9N seems to dedifferentiate the cells, because even the ALP expression was reduced as well. Our results indicate that distinct bone substitutes influence proliferation and differentiation of osteoblastic cells in different manners. These results might influence the selection of an adequate bone substitute for clinical use as well, part from degradative and biomechanical properties.

Bone Substitutes↗
PubMed2001

Solvent dehydrated bone transplants to bridge segmental bone defects: histomorphological and biomechanical investigations in an animal model.

Cancellous bone is routinely used in human surgery to fill skeletal defects. The availabilty of autogenous and allogenous grafts is limited, however. The aim of this in vivo study was therefore to determine the in-growth behaviour and biomechanical properties of solvent dehydrated human bone as an alternative to the use of autografts. In a weight-bearing experimental model, solvent dehydrated bone transplants were implanted subchondrally in the medial proximal tibia of merino sheep. After 9 months, explants as well as controls from the contralateral leg were harvested and prepared for histomorphological, histomorphometrical and biomechanical examination. A smaller, but statistically insignificant difference was found for the yield strength after 9 months for harvested specimens in comparison with untreated controls. Regarding the histomorphological results, we found a homogenous ingrowth of new bone trabeculae throughout the transplants. The degradation of the solvent dehydrated bone was not complete within the study period as shown by persistent bone remodelling. The bone per tissue volume of remaining solvent dehydrated graft particles together with newly formed bone was significantly higher than for controls. Our observation period was not long enough to document complete remodelling, but good osteointegration and reasonable biomechanical properties in this weight-bearing large animal model support the application of solvent dehydrated bone in cancellous defects of clinical relevance.

Animals↗
PubMed2001

Hysterectomy and patterns of osteoarthritis. The Ulm Osteoarthritis Study.

OBJECTIVE: To determine the association between hysterectomy (HE) and patterns of osteoarthritis (OA) METHODS: We performed a large cross-sectional study including 504 female patients admitted for arthroplasty of knee or hip joint. Patients with OA were categorized as having bilateral or generalized OA (GOA) according to the presence of radiographic OA in the contralateral or different finger joints. Odds ratios (OR) and their 95% confidence intervals (CI) for the association between HE and OA patterns were estimated adjusting for potential confounders. RESULTS: Hysterectomy (HE) was reported by 24.9 percent of the patients. Bilateral OA was present in 86.2 percent and GOA was present in 33.3 percent of the patients. HE was not associated with bilateral OA (adjusted OR=0.9; 95% CI: 0.5-1.8) but with a lower prevalence of GOA (adjusted OR=0.6; CI: 0.3-0.99). CONCLUSION: In contrast to earlier studies our results suggest that HE might be a marker for a reduced risk for a generalized pattern of OA.

Age Distribution↗
PubMed2001

Gene expression of stromelysin and aggrecan in osteoarthritic cartilage.

OBJECTIVE: To analyze cartilage gene expression of patients with osteoarthritis (OA) in correlation with radiographic and histological findings. MATERIALS AND METHODS: Twenty-one patients with OA of the knee admitted for total knee replacement were analyzed clinically and radiographically by the Kellgren and Lawrence system. During surgery, cartilage samples from the medial and lateral condyles and tibial plateaus were harvested separately. Specimens were analyzed histologically (Mankin score) and total RNA was extracted directly from cartilage tissue. Steady state levels of stromelysin (MMP-3), aggrecan (AGG) and the house-keeping gene beta-actin were measured using quantitative PCR. RESULTS: Histology of medial and lateral knee compartments corresponded to radiographic changes (Spearman correlation coefficient: r = 0.7 (p < 0.01)). There was a positive correlation between MMP-3 and AGG gene expression (r = 0.4; p < 0.01). We found considerable variation of expression levels of MMP-3 and AGG and no correlation of gene expression with histological or radiographic scoring. CONCLUSION: The positive correlation between AGG and MMP-3 suggests a common regulation of anabolic and catabolic metabolism. There was no simple dependency between gene expression and histological and radiological findings in cartilage.

Aged↗
PubMed2001

Anticoagulation: the present and future.

Thrombin is a central bioregulator of coagulation and is therefore a key target in the therapeutic prevention and treatment of thromboembolic disorders, including deep vein thrombosis and pulmonary embolism. The current mainstays of anticoagulation treatment are heparins, which are indirect thrombin inhibitors, and coumarins, such as warfarin, which modulate the synthesis of vitamin K-dependent proteins. Although efficacious and widely used, heparins and coumarins have limitations because their pharmacokinetics and anticoagulant effects are unpredictable, with the risk of bleeding and other complications resulting in the need for close monitoring with their use. Low-molecular-weight heparins (LMWHs) provide a more predictable anticoagulant response, but their use is limited by the need for subcutaneous administration. In addition, discontinuation of heparin treatment can result in a thrombotic rebound due to the inability of these compounds to inhibit clot-bound thrombin. Direct thrombin inhibitors (DTI) are able to target both free and clot-bound thrombin. The first to be used was hirudin, but DTIs with lower molecular weights, such as DuP 714, PPACK, and efegatran, have subsequently been developed, and these agents are better able to inhibit clot-bound thrombin and the thrombotic processes that take place at sites of arterial damage. Such compounds inhibit thrombin by covalently binding to it, but this can result in toxicity and nonspecific binding. The development of reversible noncovalent DTIs, such as inogatran and melagatran, has resulted in safer, more specific and predictable anticoagulant treatment. Oral DTIs, such as ximelagatran, are set to provide a further breakthrough in the prophylaxis and treatment of thrombosis.

Administration, Oral↗
PubMed2001

BMP-4 of Xenopus laevis stimulates differentiation of human primary osteoblast-like cells.

Since bone morphogenetic proteins (BMPs) are highly homologous, we investigated the hypothesis that recombinant BMP-4 of the genome of Xenopus laevis (rxBMP-4) may influence the proliferation or differentiation of human primary osteoblast-like cells (HPOC), as occurs with recombinant human BMP (rhBMP-2). HPOC were incubated in the presence of either rxBMP-4, rhBMP-2 or basic fibroblast growth factor (rh-bFGF). The last two were used as positive controls and are known to induce differentiation or proliferation of HPOC, respectively. rxBMP-4 (50 ng/ml and 100 ng/ml) induced a differentiation of HPOC to almost the same extent as rhBMP-2, whereas the addition of rh-bFGF, applied in the same concentration, failed to have any influence on cell differentiation. rh-bFGF however, provoked an increase in cell proliferation of up to 150% when compared with non-stimulated HPOC, while rhBMP-2 and rxBMP-4 had no such effect. Our results indicate an equipotent effect of rhBMP-2 and rxBMP-4 obtained from Xenopus laevis on the differentiation and proliferation of human primary osteoblast-like cells.

Adult↗
PubMed2000

Computer-assisted surgery in posterior instrumentation of the cervical spine: an in-vitro feasibility study.

Transarticular C1/2 screws are widely used in posterior cervical spine instrumentation. The use of pedicle screws in the cervical spine remains uncommon. Due to superior biomechanical stability compared to lateral mass screws, pedicle screws can be used, especially for patients with poor bone quality or defects in the anterior column. Nevertheless there are potential risks of iatrogenic damage to the spinal cord, nerve roots or the vertebral artery associated with both posterior cervical spine instrumentation techniques. Therefore, the aim of this study was to evaluate whether C1/2 transarticular screws as well as transpedicular screws in C3 and C4 can be applied safely and with high accuracy using a computer-assisted surgery (CAS) system. We used 13 human cadaver C0-C5 spine segments. We installed 1.4-mm Kirschner wires transarticular in C 1/2, using a specially designed guide, and drilled 2.5-mm pedicle holes in C3 and C4 with the assistance of the CAS system. Hole positions were evaluated by palpation, CT and dissection. Forty-eight (92%) of the 52 drilled pedicles were correctly positioned after palpation, imaging and dissection. The vertebral artery was not injured in any specimen. All of the 26 C1/2 Kirschner wires were placed properly after imaging and dissection evaluations. No injury to vascular or bony structures was observed. C /2 transarticular screws as well as transpedicular screws in the cervical spine can be applied safely and with high accuracy using a CAS system in vitro. Therefore, this technique may be used in a clinical setting, as it offers improved accuracy and reduced radiation dose for the patient and the medical staff. Nevertheless, users should take note of known sources of possible faults causing inaccuracies in order to prevent iatrogenic damage. Small pedicles, with a diameter of less than 4.0 mm, may not be suitable for pedicle screws.

Aged↗