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Biomedical subjects

N M Meenen

Publications and source records attributed to N M Meenen.

At least 19 recordsLinked to original sources
PubMed2005

Response of primary fibroblasts and osteoblasts to plasma treated polyetheretherketone (PEEK) surfaces.

Polyetheretherketone (PEEK) is a synthetic polymer with suitable biomechanical and stable chemical properties, which make it attractive for use as an endoprothetic material and for ligamentous replacement. However, chemical surface inertness does not account for a good interfacial biocompatibility, and PEEK requires a surface modification prior to its application in vivo. In the course of this experimental study we analyzed the influence of plasma treatment of PEEK surfaces on the cell proliferation and differentiation of primary fibroblasts and osteoblasts. Further we examined the possibility of inducing microstructured cell growth on a surface with plasma-induced chemical micropatterning. We were able to demonstrate that the surface treatment of PEEK with a low-temperature plasma has significant effects on the proliferation of fibroblasts. Depending on the surface treatment, the proliferation rate can either be stimulated or suppressed. The behavior of the osteoblasts was examined by evaluating differentiation parameters. By detection of alkaline phosphatase, collagen I, and mineralized extracellular matrix as parameters for osteoblastic differentiation, the examined materials showed results comparable to commercially available polymer cell culture materials such as tissue culture polystyrene (TCPS). Further microstructured cell growth was produced successfully on micropatterned PEEK foils, which could be a future tool for bioartificial systems applying the methods of tissue engineering. These results show that chemically inert materials such as PEEK may be modified specifically through the methods of plasma technology in order to improve biocompatibility.

Animals↗
PubMed2004

[Bone grafts endoscopically applied to the spine Ergebnisse der anterioren Fusion und therapeutische Konsequenzen].

The application of autogenous bone grafts represents the golden standard for reconstruction of the load-bearing anterior column in the thoracolumbar spine. However, the osseous integration of the implanted grafts is demanding and delayed union or pseudarthrosis may occur. There are no standardized data available yet indicating the further course in such cases. The aim of this study was to evaluate the incorporation of endoscopically applied grafts and to develop therapeutic strategies for delayed or non-fusions. Twenty patients suffering from unstable injuries of the thoracolumbar spine were studied in a prospective clinical trial. After primary dorsal stabilization, the anterior column was thoracoscopically reconstructed with an autogenous iliac crest graft and a fixed-angle implant (MACS). The osseous integration of the bone grafts was detected by MSCT 1 year postoperatively. Complete integration of the transplanted bone grafts was observed in only 65% of the cases. In 25% partial integration was detected and in two cases a fracture of the transplanted iliac crest graft occurred. Despite the incomplete integration of the bone grafts, the further course without surgical intervention revealed no clinical or radiological evidence of a concomitant implant loosening or a relevant secondary loss of correction. Similar to the open technique, endoscopic reconstruction of the anterior column with autogenous bone grafts may lead to disadvantageous results concerning the integration and healing of the applied bone grafts. Decision making in such cases depends on the individual clinical and radiological findings (i.e., evidence of implant loosening and concomitant loss of correction).

Adult↗
PubMed2003

[Investigation of the health-related quality of life after a dorso ventral stabilization of the thoracolumbar junction].

OBJECTIVE: Combined dorsoventral stabilization provides superior mechanical stability in the operative treatment of thoracolumbar spine fractures. Currently, there are no data available reflecting the quality of life in trauma patients following the combined procedure. The aim of this investigation was to study the health-related quality of life after dorsoventral stabilization of the thoracolumbar junction using the SF-36 Health Survey. METHODS: In order to assess the quality of life, 30 patients from a consecutive series with unstable fractures of the thoracolumbar junction were investigated in a clinical study. After posterior stabilization with an internal fixator (USS, Synthes),anterior arthrodesis was performed subsequently by autogenous iliac bone grafting in combination with osteosynthesis (MACS, Aesculap; VentroFix, Synthes). The quality of life was investigated 2 years after surgery. Additionally, plain X-rays were obtained and the degree of kyphotic deformation was measured. RESULTS: The evaluation of the data obtained from the SF-36 revealed a reduced quality of life, especially regarding the "physical functioning index", the "bodily pain index", and the "emotional functioning index". Of the patients, 42% still suffered from moderate to severe pain. Measurement of the Cobb angle showed a slight loss of correction without occurrence of a relevant kyphotic deformity. Our statistical analyses did not show any correlation between the data obtained from the SF-36 and the clinical results. Especially there was no correlation between the "bodily pain index" and the Cobb angle ( r=0.112, Spearman's rank order correlation). CONCLUSION: The patients studied here showed a reduced quality of life 2 years after dorsoventral stabilization of the thoracolumbar junction predominantly resulting in long-term pain symptoms. As these findings could not be related to the radiological results (i.e., the occurrence of a kyphotic deformation), other factors such as injury of the motion segment of the spine and the major surgical procedure have to be considered as the main reasons for the reduced quality of life. In summary, it can be concluded that the SF-36 is a suitable tool for the investigation of the postoperative outcome following dorsoventral stabilization of the thoracolumbar junction in trauma patients.

Adolescent↗
PubMed2002

[Long-term outcomes after using porous hydroxyapatite ceramics (Endobon) for surgical management of fractures of the head of the tibia].

Endobon is a porous hydroxyapatite ceramic which has been used as a bone replacement substitute since 1989. Currently there are no data available reflecting long-term effects of Endobon in human bone grafting. In order to assess such effects 35 patients with fractures of the proximal tibia were studied retrospectively over a period up to 91 months. The metaphyseal defects were filled by Endobon and fractures were stabilized by internal plate fixation subsequently. A secondary loss of reduction due to mechanical failure of the bone replacement material did not occur even after removal of metal implants. No histological signs of resorption or degradation could be found 18 months after application. Our data show that Endobon provides good mechanical properties during a long term follow-up and can be recommended as a suitable therapeutic option versus cancellous bone graft.

Bone Substitutes↗
PubMed2001

[Cervical spine trauma in patients with trisomy 21].

Atlantoaxial subluxation is predominantly found in trisomy 21. While neurological symptoms occur less frequently, fatal atlantoaxial instability with spinal cord compression has been described in trisomy 21 after minor trauma of the cervical spine. Presenting a special case we could demonstrate that atlantoaxial instability has to be ruled out in patients with trisomy 21 suffering from acute cervical spine trauma. We further recommend primary posterior fusion if the biomechanical stability of the atlantoaxial complex remains unclear after clinical and radiological exploration.

Atlanto-Axial Joint↗
PubMed2001

[Carpo-metacarpal dislocation injuries].

Carpometacarpal dislocations are rare. In most cases, the dislocation is caused by a violent injury, e.g. the crash of a motorcyclist or a fall from great height. A considerable swelling of the back of the hand may mask the characteristic lump at the root of the hand. The diagnosis can be easily missed due to serious associated injuries. The lesion is also often overlooked in the routine X-ray diagnostic. Lateral and oblique views are important for the recognition of the true extent of the lesion. Anatomical reposition is difficult if the dislocation is not fresh and open reposition is necessary. Between 1990 and 1999, altogether 16 patients who had suffered a carpometacarpal dislocation were treated. One patient had a rare dislocation of the III. to V. joints. Simultaneous dislocation of all five carpometacarpal joints was seen in three cases. The treatment mostly consists of closed reduction and temporary Kirschner wire transfixation. Fourteen patients were controlled (clinical examination and X-ray control) after an average follow-up time of three years. In addition, the DASH questionnaire was used. After an average time of 3 years the patients showed in 64% of the cases excellent and good results (eight excellent, one good). The subjective function of the hand was moderate in 29% (four patients), in one patient the subjective function was poor (7%). Five patients had a diminished range of motion of the hand. The average points in the DASH questionnaire were 24. We recommend as therapy of choice after primary closed repositioning, primary surgery by means of short Kirschner wires introduced from distal-dorsal to proximal-palmar. In cases of impossible closed reduction or in cases with local additional injuries, open treatment for fixation, is indicated.

Adult↗
PubMed1998

[Attempted suicide--a challenge for the trauma surgeon?].

The data from 767 patients after a suicide attempt or suicide were analyzed retrospectively. Skeletal damage was present in 52% of the patients. This was also the highest percentage in the breakdown of the injury patterns, followed by damage of the central nervous system (26.6%). Injuries to parenchymatous organs (20.1%) took third place. Extensive soft tissue injuries were diagnosed in 18.1% and relevant vascular lesions in 16% of suicide cases. At the same time, the high percentage of multiple trauma patients (22.9%) reflects the severity and the extent of injuries suffered in the application of "violent methods". Injuries of suicide cases involving violence often resemble those of serious road traffic accidents. In contrast to unselected patients, the injury pattern of suicide cases with multiple trauma is dominated by jumps from a great height and being run over by a train. However, when unusual suicide techniques are used, the surgeon's experience may soon become insufficient. To our knowledge, special traumatology wards provide the best available diagnosis and emergency care for these patients unless they have suffered purely trivial injuries.

Adolescent↗
PubMed1998

[Treatment of cartilage defects].

Articular surface defects will not heal spontaneously. Localized defects, e.g., in the knee joint, should be treated with transplantation of autologous cells containing material of different composition. For transplantation of osteochondral pegs they are grafted from minor loaded joint areas and implanted into highly loaded defect regions. For autologous cartilage cell transplantation they are proliferated in vitro and then implanted into the defect zone under an periostal flap, harvested from the proximal tibia and sutured into the cartilage level around the defect. Autologous paste of cartilage and cancellous bone is transplanted into aggressively prepared defects with the concept of regrowing articular cartilage out of the transplanted cells and the subchondral bone.

Adult↗
PubMed1997

[The impact factor--a reliable sciento-metric parameter?].

With shortage of research funds and increasing competition for medical posts, performance indicators and control instruments are being looked for in order to be able to allot research funds and make professorial appointments in relation to scientific performance. Incomprehensibly for many, the impact factor has become the decisive scientometric indicator at German universities despite of substantial systematic limitations. The impact factor is derived from the journal citation reports. Its basis of calculation entails the following problems: the editorial board of the private Institute of Scientific Information (ISI) decides on whether a journal is to be classified as a source journal. The citation index of all journals is calculated from their citations alone. Crucial means of influencing the impact factor result from self-citations and citation groups in these source journals. Languages other than English and other than Latin alphabets are appreciably disadvantaged by the citation index, which is why for example despite its international significance the rapid development of the osteosynthesis technique in German speaking countries went unnoticed by British and American orthopedic surgeons and scientists. The articles on postgraduate training necessarily published by clinicians in the respective language of their country are not cited because the addresses of such publications do not engage in research. Clinical disciplines (especially highly specialized disciplines such as trauma and hand surgery) thus attain appreciably lower impact factors for their journals than basic disciplines and interdisciplinary clinical sectors which lead the ranking of journals. The period covered in calculating the impact factor is only 2 years. Very modern and widely disseminated organs of publication with a short information halflife are favored. From the 10 objectively most often cited and most important journals for the scientific society, only 2 are to be found amongst those with the highest impact factor. The impact front-runner from 1995 has a very low absolute number of citations. The impact factor provides limited statistical information on a journal in its special field. Using it for this purpose presupposes knowledge of rules, limitations and constraints. Its uncritical use as a general currency of science is fundamentally unscientific. In addition, this leads to the specialists in the field knowledge of the universities being disregarded in favor of a pseudo-objective parameter determined elsewhere. At all events, correction factors for the impact factor have to be applied in respect to the different disciplines. The faculties should reach agreement on relevant (also on German language) organs of publication. The impact factor is not suitable as an indicator of the research activity and the quality of a researcher or an institution. Besides careful human judgement and other classical methods of decision making, the Science Citation Index can contribute to the individual evaluation.

Bibliometrics↗
PubMed1997

[Perioperative antibiotic prophylaxis in hip operations. Penetration into bone, capsule tissue and cartilage exemplified by cefuroxime].

The most serious complication of accident surgery is postoperative osteitis. At the same time, perioperative antibiotic prophylaxis is generally recommended in order to reduce the rate of infection in joint surgery. The criteria for the suitability of a substance as prophylaxis include inter alia the activity spectrum with respect to the expected microorganisms, its retention time in the body and its ability to penetrate the endangered tissue. In the present study, the systemic and local activity levels after a single i.v. dose of 1500 mg cefuroxime was investigated in relation to the time of administration in 30 patients who had to undergo total hip replacement owing to a medial fracture of the neck of the femur. The tissue and serum samples were analyzed by high pressure liquid chromatography (HPLC). The results show that the tissue levels of the intermediary cephalosporin after an i.v. single shot dose are on average still several times higher than the minimum inhibitory concentration (MIC) of the most frequent bacterium. Staphylococcus aureus, as late as 4 hours after application. The optimal time for the administration form selected was immediately prior to the operation and the concentrations measured suggest that several repeat doses of cefuroxime for short-term prophylaxis are not necessary.

Aged↗
PubMed1997

Isolated fracture of the posterolateral tibial lip (Volkmann's triangle).

PURPOSE: To retrospectively evaluate the underlying pathomechanism of isolated fracture of the posterolateral tibial lip (Volkmann's triangle), and to demonstrate associated radiographic methods. MATERIAL AND METHODS: Retrospective analysis of 2500 ankle lesions showed an isolated fracture of the dorsal tibial lip in 25 cases. Distal tibial lesions of growing individuals were not considered. All patients were examined by radiography in internal oblique and lateral views. RESULTS: Sixteen of 25 patients had had their accident during winter; 11 had slipped on ice or snow. All 25 patients showed a closed ankle lesion in the correct joint position with no clinical signs of instability. Evaluation of the standard images showed isolated fracture of the posterolateral tibial lip in 24 patients. The fracture was best recognized in the standard lateral view in 22 patients. In 2 patients the lateral stress projection demonstrated the fracture (20 degrees internal rotation). In one case the fracture was only seen on axial CT images. Twenty-two patients with small wedge fragments were treated conservatively; 3 with a displaced and large fragment had surgical revision and stabilization. Sixteen cases were examined by conventional radiography at follow-up examination and 5 of these showed radiological signs of arthrosis. CONCLUSION: Plain conventional radiography is still necessary in the primary diagnosis of ankle joint lesions. The isolated fracture of the dorsal tibial margin is best seen in the standard lateral view. Indication for CT in routine diagnostics is limited to cases showing clinical evidence of ankle injury without roentgenological signs of a fracture in the standard images. Differential diagnoses include the pilon lesion and the Maison-neuve-type fracture.

Accidental Falls↗
PubMed1997

[Pathologic humeral fracture in secondary osteosarcoma of the humerus: a rare complication of osteodystrophia deformans Paget].

Pathological fracture in histologically proven post-Paget osteosarcoma of the humerus is a rare complication. Due to individual requests as well as age and comorbidity, a course of primary palliative treatment was chosen in the present case. Survival time after diagnosis was 9 months and the patient died of a tumor-independent disease. Even in combined treatment, consisting of surgery and (neo-)adjuvant radio-/chemotherapy, prognosis of osteosarcomas secondary to Paget's disease remains very disappointing. Therefore, in treatment of this highly lethal tumor the patient's individual requests and personal situation often require more consideration than in many other malignancies.

Aged↗
PubMed1995

[Traumatic dislocations of the cranial spine in childhood. Clinical description of 2 cases].

Case reports are presented on 2 children who had suffered traumatic luxations in the region of the cranial cervical spine. In both children, there was interruption of spinal cord continuity by severance with respiratory arrest and tetraplegia. As a rule, death occurs immediately at the site of accident. With a well-developed emergency ambulance system in conurbations, however, such cases may be admitted to hospital after resuscitation. After 16 hours, a child admitted to hospital died of a progressive bradycardia with subsequent asystole in respiratory paralysis. The second child survived for 10 months until it died of pneumonia.

Atlanto-Axial Joint↗
PubMed1995

[Behavior of artificially-induced epiphyseal groove defects. 3: Transplantation of autologous and homologous rib cartilage in Göttingen minipigs. Findings after a 16 week interval].

Drillholes of 8 mm diameter were made through the epiphyseal cartilage of the distal femora in 20 6-week-old Göttingen minipigs. The defects were filled with autologous or with homologous cartilage. This was intended to prevent epi-metaphyseal osseous bridge formation. If of appropriate size and location, the latter would lead to subsequent misgrowth. In group A (autologous costal cartilage), at all drillholes the transplanted costal cartilage can prevent ossification of the defect. An epiphyseal boundary lamella was formed over the transplant which precluded penetration of vessels into the defect. In group B (homologous costal cartilage), the transplanted costal cartilage showed a tendency to mineralization in all preparations at the 20 drillholes available. The cartilage was integrated into the primary cancellous bone developing within the defect. An epiphyseal boundary lamella had not formed in the period of the experiment (in contrast to autogenous transplantation). These investigations show that autologous costal cartilage is superior to homologous costal cartilage in the potential clinical application of costal cartilage transplants in the treatment of Brodie abscesses or post-traumatic epiphyseodeses.

Animals↗
PubMed1995

[Experiences with plate osteosynthesis in treatment of peri- and sub-prosthetic femoral fractures].

Plate-osteosynthesis proves to be an established procedure in our department for treatment of fractures of the femur in patients older than 70 years with total hip replacement even when loosened. It offers the advantages of comparably low aggressive standard operation techniques and acceptable success rates. This treatment allows for short preoperative period of the patients with their typical multimorbidity in many traumatological departments. In younger patients with symptomatical loosening, simultaneous exchange of the hip prosthesis should always be considered. Thus, individual therapy concept including the specific fracture type, general condition and age must be followed for each patient.

Aged↗