Biomedical subjects

R T Müller

Publications and source records attributed to R T Müller.

At least 19 recordsLinked to original sources

PubMed2005

[Therapy of enchondroma in long bones].

The treatment of enchondroma in long tubular bones has been the subject of controversial discussions for several years. Whereas secondary malignancy is very rare when the enchondroma is located in a hand, a position near to the trunk represents a high risk of transformation into a chondrosarcoma. For an enchondroma in long tubular bones, authors recommend a whole variety of approaches ranging from regular controls to radical en bloc resection. Between 1989 and 2001 we followed a concept of intralesional resection and cement filling. After an interval without recurrences, the cement was extracted and replaced by a spongiosaplasty. Of 16 patients 12.5% suffered from an intralesional fracture in the course of the treatment, and 25% complained of persistent pain and loss of function after surgery. These complications led us to change our concept. Though there were two cases of secondary transformation into chondrosarcoma G1, we now prefer to keep the patients under close clinical and radiological control without performing surgery.

Adolescent↗

PubMed2004

In vitro and in vivo performance of Ti6Al4V implants with plasma-sprayed osteoconductive hydroxylapatite-bioinert titania bond coat "duplex" systems: an experimental study in sheep.

To evaluate the in vivo performance of "duplex" hydroxylapatite top coat/TiO(2) bond coat systems, cylindrical Ti6Al4V rods of 130 mm in length and 11-13 mm in diameter were coated by atmospheric plasma spray (APS) technique with both a standard hydroxylapatite (HAp) layer and a HAp+TiO(2) bond coat "duplex" layer. In this pilot study coated and uncoated rods serving as controls were implanted into the femur of sheep so that their distal ends were freely suspended in the medulla of the femur. After an observation time of six months it was found that bone apposition and bone ingrowth were considerably increased in the presence of a osteoconductive coating. In particular, in vivo spalling and delamination frequently observed with HAp coatings was virtually absent in duplex coatings owing to the strong adhesion of the bond coat to the HAp top coat that anchored the latter solidly to the metallic surface of the implant. Some tentative mechanisms leading to this improved coating adhesion will be discussed.

Alloys↗

PubMed2001

HPV16 L1E7 chimeric virus-like particles induce specific HLA-restricted T cells in humans after in vitro vaccination.

Cervical cancer has been shown to be highly associated with human papillomavirus (HPV) infection. The viral oncogenes E6 and E7 are constantly expressed by the tumor cells and are therefore targets for immunotherapy. In the present study we investigated the potential of HPV16 L1E7 chimeric virus-like particles (CVLP) to activate specific cytotoxic T lymphocytes in human blood donors. CVLP were expressed by recombinant baculovirus and purified. Direct incubation of freshly isolated peripheral blood lymphocytes (PBL) with CVLP resulted in induction of proliferation and growth of T cell lines. To enhance antigen presentation we also loaded dendritic cells with CVLP and used them to activate naive T cells. Growing cell lines were mainly CD3 positive (>95%) with a predominant CD4-positive and a minor CD8-positive component. Analysis of Tcell specificity was carried out by an interferon-gamma ELISpot assay. Dendritic cells pseudoinfected with CVLP or pulsed with human leukocyte antigen (HLA)-A*0201-restricted peptide E7(11-20) or with a newly identified HPV16 peptide L1(323-331) were used as stimulator cells. T cells responsive to CVLP were found in the cultures with frequencies of 0.5%-0.7%. Frequencies to peptides were around 0.1%. These T cells had cytolytic activity toward autologous B-lymphoblastic cell lines either pseudoinfected with CVLP or pulsed with HLA-A*0201-restricted peptides. They also lysed the HPV16- and HLA-A*0201-positive cervical cancer cell line CaSki, whereas HLA-A*0201-negative SiHa cells were not lysed. We conclude from our data that CVLP show promise for a therapeutic vaccine in patients with HPV16-positive cervical intraepithelial neoplasia lesions or cervical cancer.

Antigens, Viral↗

PubMed2001

[Effect of graduate education on complication rate and costs of hip prosthesis implantation].

PURPOSE: We studied the effect of surgical experience with regard to complications and costs after 3290 primary total hip arthroplasties (diagnosis: osteoarthritis). METHODS: We retrospectively analysed duration of clinical treatment and anaesthesia, blood loss, number of banked blood and perioperative complications (fractures of the shaft and acetabulum, dislocations, peripheral nerve injuries, thrombosis of the deep veins, embolism and deep wound infections) related to the experience of the surgeon (junior surgeons in comparison to the consultant) after 3290 primary THA's from 1974 to 1997. Cost analysis was performed by measurement of time and material expenditure. RESULTS: 39.2% of all operations were performed by junior surgeons. This number emphasizes the realisation of the order of education in our clinic. Both groups showed just few differences in number of duration of clinical treatment, banked blood, nerve leasions and embolism. We found statistically not significant increased rates of fractures and dislocations in the THA's performed by an unexperienced surgeon, however the rates decreased the last 14 years. Significantly higher rates of deep wound infection at the beginning decreased in the last 9 years to the level of experienced surgeons. Due to longer operation times, we calculated higher expenses of DM 85 per case in the group of junior surgeons. CONCLUSIONS: Using an educational program, carried out with an experienced surgeon, there is nearly no additional risk for the patient regarding the complication rates in THA's. However, there are higher financial expenses that have to be calculated.

Aged↗

PubMed2001

[Cost analysis of hip and knee prostheses as the basis for cost-benefit evaluation].

INTRODUCTION: The diagnosis-related reimbursement for total hip- and knee arthroplasty is often interpreted as a claim for cost reduction and thus influences increasingly the surgeon's choice of treatment. With regard to further planned budget reductions the following questions arise: Remains quality payable? Where are cost savings possible? PATIENTS AND METHODS: Prospective analysis of 21 patients with primary hip- and 26 with knee arthroplasties to identify all cost factors during the hospitalization period including the implantation technique and quality improvement measures. RESULTS: Expenses of 18,763.26 DM for hip- and 18,649.40 DM for knee implants were covered by the diagnosis-related reimbursement. Compared to cemented implants, the average total costs of cementless prostheses were usually less expensive. CONCLUSION: Although the current costs are covered, a further reduction of the diagnosis-related reimbursement may result in a loss of quality. The present cost analysis outlines a guideline for an individual calculation and assessment of possible saving effects.

Aged↗

PubMed2001

[Value of digital subtraction arthrography and radionuclide arthrography in determination of indications and planning of revision surgery in total hip replacement].

PURPOSE: Clinical and radiographic findings are of little value in the diagnosis of hip endoprothesis loosening. Refined contrast and radionuclide arthrographic techniques are more precise in predicting endoprothesis loosening. Here we compare both techniques with respect to the surgical result. MATERIAL AND METHODS: 68 patients with hip pain after various arthroplasty procedure were investigated by clinical examination, X-ray, DSAr and AS. Surgical proof was obtained in 73.5%. RESULTS: An acetabular component loosening was detected in 89% by DSAr and in 86% by AS with a specificity for both methods of 93%. The femoral component loosening was seen with a sensitivity of 89% by DSAr and 100% by AS, respectively. Specificity of DSAr in the femoral compartment was 94%, of AS 88%. CONCLUSIONS: DSAr and AS are useful tools in the diagnosis of hip endoprothesis loosening and in planning surgical treatment. Both methods are comparable concerning the acetabular component, whereas AS is more sensitive in detecting femoral stem loosening. Combination of both methods is not recommended for routine diagnosis.

Aged↗

PubMed2001

[Unusual course of sacrococcygeal chordoma].

Observation of a sacrococcygeal chordoma with exceptional long survival of now 17 years after incomplete surgery with following additional resection and adjuvant radiotherapy. Local recurrence occurred after more than 10 years, metastases after 15 years.

Aged↗

PubMed2000

[Implant positioning in epiphysiolysis capitis femoris. Sequelae of poor outcome and consequences].

Which consequences can be ascribed to the intraarticular position of devices in the operative treatment of a slipped capital femoral epiphysis? Which steps are to define as a standard of a careful procedure? The clinical and radiological results of five cases of a pin or nail penetration after the operative treatment of a slipped capital femoral epiphysis are described, a possible connection of casualties is investigated. The intraarticular position of devices in most cases goes along with an unfortunate clinical outcome and leads to a higher risk of developing chondrolysis. Because of the radiologic overprojection with the femoral head it is possible to oversee the malposition of the pin. Any operative treatment of a slipped capital femoral epiphysis requires a careful intraoperative X-ray examination combined with documentation. With this procedure the bad results of an intraarticular implant position must be ascribed to the reminding risk of a fateful development.

Adolescent↗

PubMed2000

[Early loosening of a cemented hip endoprosthesis stem of titanium].

Up to now there are no facts concerning the loosening rate of the cemented titanium stem (Trios). The central guiding canula and the longitudinal drilled stem shall ensure a symmetric cement mantle. In order to estimate the risk of aseptic loosening all Trios prostheses implanted in our clinic (n = 67; operations 1/95-11/96; max. follow-up: 3.1 years) were examined in a retrospective study and compared with a conventional femoral component (n = 141; Müller special; CoCr; operations 1977-1982). We used survivorship analysis to assess the results (Kaplan-Meier method; end point: revision). Compared to the conventional femoral stem the survival rate of the Trios prostheses was significantly worse (p = 0.0001). The probability of no revision after 3 years was 72% (conventional femoral component: 96%). Preoperative x-rays showed radiolucent lines surrounding the cement mantle. These findings as well as the loosening at the cement metal interface were confirmed intraoperatively. The explanted stems showed corresponding signs of abrasion on the surface. Our results prove that the application of cemented titanium stems might be problematic. With regard to the Trios prosthesis we recommend close routine check-ups to keep the chance of an early revision.

Aged↗

PubMed1999

Shear strength of the cement metal interface--an experimental study.

The shear strength of the cement-metal interface using rods with different surface treatments and a clinical standardized cementing technique was studied. Under "dry" conditions, a low interface shear strength can be obtained with polished and smooth CoCrMo surfaces (peak-to-valley height Rt: 1 microm, average 0.2 MPa; 5 microm, 0.38 MPa). Grit-blasted and polymethylmethacrylate (PMMA)-precoated surfaces achieved higher values (PMMA precoat: average 5.16 MPa; CoCrMo peak-to-valley height Rt: 20 microm, average 8.61 MPa: 60 microm, average 7.8 MPa). After immersion in physiological saline solution for 60 days, the PMMA-precoated rods kept their initial stability whereas all the other test rods had lost their stability completely. A microscopic analysis of cross-sections revealed gap formations at the cement-metal interface to varying degrees (1-16 microm). PMMA-precoated rods rarely showed any gap formation at all. The above-mentioned gap formation was seen independently of the porosity at the cement-metal interface and corresponds to the clinical and postmortem observed debonding of the interface.

Biomechanical Phenomena↗

PubMed1999

[Computer-based patient information. Legal bases, concept and 10-year experience].

Culpable deficits of the preoperative information cause a complete illegality of the whole medical intervention and lead to liability for any resulting damage. In cases of controversy it's the physician's due to prove the correct preoperative information. To reduce these liability-risks a computer based information system has been developed. With its help an working sheet is provided which is individually adjusted for the patient. Based upon this record the real preoperative information takes place. After the patient signed the record the physician keeps it at his disposal for proving the contents of the preoperative information. The conception's use over many years shows that overlooking essential aspects and misunderstanding can grossly be excluded for the patient and a high quality of information can be reached.

Germany↗

PubMed1998

Characteristics of phenol. Instillation in intralesional tumor excision of chondroblastoma, osteoclastoma and enchondroma.

Because of the typical metaphyseal-epiphyseal growth of giant cell tumors and chondroblastomas, the optimal result of an en bloc resection can usually only be achieved by a loss of joint function. For this reason, intralesional excision has prevailed, though it leads to a high rate of relapses. Adjuvant therapy involving irrigation of the remaining bone cavity with phenol can distinctly decrease the rate of relapse. Little is known about the amount of phenol applied that is absorbed. This study investigated the urinary excretion of phenol following the instillation of 102 ml of a 5% phenol solution. The method consisted of urine collection from 11 patients treated by phenol instillation preoperatively, and at 1, 3, 6, 12 and 24 h postoperatively. The urine specimens were analysed for phenol by mass spectrometry. Preoperatively, the value was 5.1 mg/l on average. The maximum concentration of 62 mg/l was found 1 h after instillation, with an average value of 41.5 mg/l, and after 3 h of 18.9 mg/l. A further rapid decrease in the excretion rate was recorded, with normal values being reached after 12 h. This means a maximum of 9% and an average of 2% of the instilled amount of phenol were excreted in the urine within 24 h postoperatively. By comparing these urinary concentrations to published standards, we conclude that the instillation of a 5% phenol solution into bony lesions is associated with a relatively low risk of systemic toxicity.

Adult↗

PubMed1998

Cost analysis for total hip arthroplasty by measurement of time and material expenditure.

We prospectively determined the total cost of total hip arthroplasty in 26 consecutive cases by comprehensive measurement of time consumption and detailed data acquisition for material consumption including every single item. The average partial cost caused by complications was calculated through the average prolongation of hospitalization in 1550 cases. Expenses of 18,660 DM for a hospitalization period of 23 days and 2/3 cementless arthroplasties were just covered by the diagnosis-related reimbursement, even though quality improvement measures like optimized cementing techniques, jet lavage, intraoperative X-ray control, autologous blood collection, and retransfusion sets were employed.

Adult↗

PubMed1998

Improvement of the cement mantle of the acetabular component with bone cement spacers. A retrospective analysis of 200 cemented cups.

A discontinuous or thin cement mantle of a socket is associated with increased polyethylene wear and cement fractures. In a retrospective radiological analysis we examined the quality of the cement mantle in cups without (group I = 100 Charnley-Mueller cups) and with (group II = 100 Contemporary cups, Howmedica) bone cement spacers. Under-filling (0-2 mm) and over-filling (> 8 mm) of the cement mantle were noted and classified. Statistics show significantly less under-filling of the cement mantle in group II than in group I (P = 0.001), in particular when comparing separate cup regions (thirds: P << 0.001). Furthermore, there is no significant difference in the frequency of overfilling with cement between groups I and II (P = 0.108). To sum up, utilization of an acetabular component with performed bone cement spacers considerably improves the quality of the cement mantle without additional cost.

Acetabulum↗

PubMed1998

Targeting of the myosin-I myr 3 to intercellular adherens type junctions induced by dominant active Cdc42 in HeLa cells.

Myr 3, a member of the myosin-I family from rat, is shown in this study to be localized at adherens-type intercellular junctions in epithelial and nonepithelial tissues. Formation of intercellular junctions and the accompanying recruitment of myr 3 to these junctions involves signaling by the Rho subfamily of small GTP-binding proteins. This conclusion is based on studies with HtTA-1 HeLa cells that were induced by overexpression of constitutively active Cdc42Hs to form typical adherens-type intercellular junctions enriched in cadherins (N-cadherin), beta-catenin, filamentous actin and myr 3. Recruitement of myr 3 to Cdc42-induced adherens junctions in HeLa cells was dependent on a short region of the tail domain and a functional myosin motor domain, but was independent of its myosin-I tail homology and SH3 regions. Overexpression of constitutively active Rac1 induced a distinct type of adherens junction in HeLa cells that was characterized by elaborate intercellular interdigitations enriched in N-cadherin, beta-catenin and F-actin. Myr 3 was often present, but not specifically enriched in the intercellular junctions induced by constitutively active Rac1.

Amino Acid Sequence↗

PubMed1997

Shear and tensile strength of hydroxyapatite coating under loading conditions. An experimental study in dogs.

The shear and tensile strength of a hydroxyapatite (HA) coating on a femoral component was studied after physiological loading conditions in 8 German Shepherds. A proximal macrostructure on the stem was used to protect this region from shear stresses. Another four implantations with uncoated components were used as controls. In vitro testing of the HA layer demonstrated excellent tensile strength and stability to surface deformation. The loaded implants were tested at 6, 12, and 24 weeks. At 6 weeks the HA-coated components could easily be removed by axial loading, whereas the HA layer remained undamaged on the metal. However, pull out tests of implants older than 12 weeks showed complete debonding of the HA layer from the non-macrostructured surface due to shear forces in all cases. Debonding of the HA layer was also observed with microradiography. The macrostructured surface prevented dislodging of the component from this area at pull out test by distributing shear forces. Unlike in uncoated implants, considerable amounts of bone remained attached onto the HA macrostructure when the surrounding femur was pulled out. Shear forces cause debonding of the HA layer, while tensile stress affects failure within the bone. Physiological loading partially produces gaps at the interface so direct transmission of tensile forces onto the bone is lost, and the coating-metal interface becomes the weak point in the system.

Animals↗

PubMed1997

The mechanism of loosening in cemented hip prostheses determined from long-term results.

Analysis of the mechanisms of loosening of cemented stems by radiological long-term follow-up in 129 cases. The most important finding was the failure of the cement-metal interface (29.5%), which was correlated significantly with osteolysis (31%). This suggests that the polyethylene debris reaches the bone through defects in the cement mantle (76.7%). In fact, the appearance of cement defects matches the number of identified osteolyses. This study shows that no permanent fixation can be achieved by the surface roughness of 2.0 microns Ra tried herein.

Adult↗

PubMed1997

[Process and outcome quality in giant cell tumor in relation to surgical management].

Giant-cell bone tumors display a locally aggressive growth pattern, frequently recur if no adjuvant treatment is given, and may potentially metastasize. By virtue of their biological behavior and typically juxta-articular localization, giant-cell bone tumors require specific surgical management. Thus, an intralesional tumor excision must be supplemented by adjuvant bone cementing, possibly combined with instillation of phenol or cryotherapy. These combined treatment modalities assure a high-quality procedure, defined as the actual way medical care is delivered, by promoting the quality of the outcome, defined as the effect of a medical procedure on the patient's state of health.

Adult↗