Quasi-exact solutions for guided modes in two-dimensional materials with tilted Dirac cones

We show that if the solutions to the (2+1)-dimensional massless Dirac equation for a given one-dimensional (1D) potential are known, then they can be used to obtain the eigenvalues and eigenfunctions for the same potential, orientated at an arbitrary angle, in a 2D Dirac material possessing tilted, anisotropic Dirac cones. This simple set of transformations enables all the exact and quasi-exact solutions associated with 1D quantum wells in graphene to be applied to the confinement problem in tilted Dirac materials such as 8-Pmmn borophene. We also show that smooth electron waveguides in tilted Dirac materials can be used to manipulate the degree of valley polarization of quasiparticles travelling along a particular direction of the channel. We examine the particular case of the hyperbolic secant potential to model realistic top-gated structures for valleytronic applications.

Ribulose-1,5-bisphosphate Carboxylase-Oxygenase: New Aspects Respective the pH-Dependance of the Carboxylation Reaction

The investigation was directed towards the effects of reaction conditions, substrates and pH on the carboxylation reaction of ribulose-1 ,5-bisphosphate carboxylase-oxygenase in the crude enzyme extracts from several plants. Optimal substrate concentrations (HCO3 - and RubP) were determined. The highest carboxylase activity was attained with Tris/HCl buffer. The pH activity profile was quite sharp with an optimum at pH 7.8. Purified and crystallized carboxylase yielded a broad optimum curve under the same reaction conditions

Effect of Phosphinothricin (Glufosinate) on Photosynthesis and Photorespiration

Phosphinothricin (PPT) causes a rapid inhibition of photosynthesis under atmospheric conditions (400 ppm CO2, 21% O2). However, under conditions (1000 ppm CO2, 2% O2) under which photorespiration cannot occur, there is no or only a very low rate of photosynthesis inhibition by phosphinothricin. Under both conditions, a strong NH4 +-accumulation is apparent caused through the inhibition of glutamine synthetase by phosphinothricin. This indicates, that NH4 +-accumulation cannot be the primary cause for photosynthesis inhibition by phosphinothricin, but a process in connexion with photorespiration plays a central role. Through the lack of amino donors, the transamination of glyoxylate to glycine in photorespiration cannot take place. PPT causes a great decrease in glutamine, glutamate, aspartate, serine, and glycine. Following addition of these amino acids to PPT, there is a decrease in photosynthesis inhibition by PPT. With the addition of glutamine or glutamate to PPT no decrease in serine and glycine is detected, because the transamination of glyoxylate to glycine in photorespiration can occur.

Piloting education days for patients with early rheumatoid arthritis and their partners: a multidisciplinary approach

OBJECTIVES

To develop, pilot, refine and reassess an education day presented by a rheumatology multidisciplinary team (MDT) for recently diagnosed (less than six months) rheumatoid arthritis (RA) patients and their partners/carers.

METHODS

A patient education day was developed drawing on an assessment of local patient educational needs and preferences and input from a rheumatology MDT. Feedback from the first education day (2004) (Day 1; 12 patients; age range 19-63 years (median 46); 10 of whom were accompanied by a partner) informed the development of a second education day (2005) (Day 2; 19 patients; age range 36-75 years (median 57.5); 13 of whom were accompanied by a partner). Participants completed evaluation forms on both days and at follow-up between six and seven weeks later, rating each session on a 5-point scale on dimensions of 'informative', 'useful', 'interesting' and 'enjoyable'. A global rating of the day's 'usefulness' was completed at the end of each day on a 10-point scale. Participants were asked to write comments on each session and on aspects of the entire day. RA knowledge, and general and RA-specific self-efficacy were also measured on day 2 (and at follow-up) using the 12-item Patient Knowledge Questionnaire, the 10-item generalized self-efficacy scale and a four-item RA-specific self-efficacy scale. Both qualitative and quantitative methodologies were used in the analysis.

RESULTS

Ratings for individual sessions were all high, with no session being rated below 4 out of 5 (1 = 'totally disagree' to 5 = 'totally agree') on both days. The majority of patients (84%) and their partners (57%) responded to the follow-up. Many had used the information package distributed on the day. Some patients and their partners reported positive changes in RA management. Although patient knowledge did not increase significantly (medians 11 at both time points, p = 0.054) (Day 2), RA self-efficacy improved (baseline 11 and 14, respectively), suggesting that patients were more confident in managing their condition (p = 0.010).

CONCLUSIONS

The development of this 'local' education and information intervention was carried out in line with Medical Research Council guidelines, and the lessons learned from Day 1 informed further development for Day 2. A one-day format for education of early RA involving the rheumatology MDT was rated highly by participants and warrants further examination. Although this study was a small 'local' intervention, its strengths are that it informs the possibility of wider developments of this kind using a MDT.

[Additional treatment in chronic pain syndrome due to hip and knee arthritis with the selective serotonin reuptake inhibitor fluvoxamine (Fevarin]

OBJECTIVE

The aim of this study was to investigate the effectiveness and safety of the selective serotonin reuptake inhibitor fluvoxamine (Flevarin) in patients with a chronic pain syndrome due to hip and knee arthritis.

METHODS

We prospectively investigated 60 patients in a single-centre double-blind study. The group was divided into two groups (M1 fluvoxamine; M2 placebo) each containing 30 patients, age ranging from 30 to 80 years. During treatment results were evaluated using several scales once at the beginning (V1) followed by weekly evaluations (V1-V8) and one final investigation at the end of treatment (V9). The investigated medication consisted of 50-150 mg fluvoxamine. In addition other drugs such as NSAID were administered (diclofenac, piroxicam, ibuprofen).

RESULTS

Both groups (M1 and M2) showed a reduction of pain during treatment using the visual analogue scale (VAS). However, no statistical difference was found between both groups concerning pain reduction at any time. A significant pain relief was monitored in the patients of the M1 group towards the end of treatment. Concerning the daily impairment because of pain measured by the Griss scale an improvement was seen in 70 % of the patients receiving fluvoxamine versus 44 % in patients receiving placebo. Additionally, an improvement in the M1 group was seen in the WOMAC scale and in factors such as pain, stiffness and mobility compared to the M2 group. Using the CGI scale, 56.6 % of the M1 group compared to 37.9 % of the M2 group were stating that their overall status had improved "much" or "very much" at the end of the treatment (V9). A depression had been excluded in all patients. No statistical differences were seen in the Bf scale (von Zerssen) during all evaluations (V1 to V9). During the whole study 127 side effects were registered in 49 patients. None of the 5 severe events were related to the investigated drug.

CONCLUSION

Considering the good effects in combination with very few side effects, a positive cost-effectiveness relation for the usage of fluvoxamine can be stated in patients with chronic pain syndrome due to hip and knee arthritis.

[Therapeutic efficiency in multisegmental fusions of the lumbar spine]

AIM

The aim of this study was to evaluate of the efficiency of an internal fixateur used since 1998 in multisegmental spondylodesis of the lumbar spine.

METHOD

The prospective study included 105 patients with degenerative changes or instabilities of the lumbar spine, who underwent an anterior and posterior stabilisation of more than two segments. The minimum period of follow-up was more than 6 months. There were several objective scores used for the evaluation of the efficiency (Oswestry score/visual analogue scale [VAS]). In addition, the quality of the new internal implant was assessed concerning the rate of loosening and failure of the implant. This new internal fixateur, produced as a titanium alloy, consists of pedicle screws and longitudinal rods with 5 mm diameter and connection elements. Upon pulling the nut a square stabilised situation is created. Altogether the three-segmental stabilisations predominated (n=77), 23 patients received a four-segmental, four patients a five-segmental stabilisation and one received a stabilisation of six levels, mainly involving the segments L3/4 to L5/S1. Because of severe deformities in 14 cases the pedicle screws were applied by computer-assisted navigation (Navitrak).

RESULTS

In 12 patients (11.4%) radiological signs of loosening of the inserted pedicle screws in the vertebra were diagnosed. The radiological analysis resulted in pseudarthrosis of 4 (1.2%) of the 349 amalgamated segments. There were no cases of material failure. The average value of the pain score preoperatively (VAS) was 7.7 (5-10, SA 1.3) and postoperatively 4.6 (1-10, SA 1.8). With regard to the Oswestry disability index the preoperative average value amounted to 51.9% (30-91, SA 11.8) and postoperatively 35% (12-74, SA 11.8). In all 98 (93.3%) patients were satisfied, 7 (6.7%) patients reported a decline of the subjective outcome.

CONCLUSION

This system achieved a high degree of patient satisfaction and showed a low rate of pseudarthrosis. Furthermore, it can be inserted for short and long fusions, as well in deformities.

Clinical outcome after transfixation of the epiphysis with Kirschner wires in unstable slipped capital femoral epiphysis

Treatment of slipped capital femoral epiphysis (SCFE) is still controversial. Agreement has not yet been reached on the appropriate time to perform surgery, the necessity of repositioning manoeuvres, the type of implants for stabilisation, or the need for prophylactic treatment of the contralateral side. In this retrospective study, we present 29 patients with unstable (acute and acute-on-chronic) SCFE treated by internal fixation of the epiphysis with three or four Kirschner wires both therapeutically on the affected side and prophylactically on the not (yet) affected side. After hardware removal and mean follow-up of 3.5 years, radiological and clinical examination of hip function was carried out. X-ray in two planes showed no incidence of any slip progression. Applying the score used by Heyman and Herndon, 18 results (62.1%) were classified as excellent, nine (31.1%) as good, one (3.4%) as fair, and one (3.4%) as poor. The rate of severe complications such as chondrolysis and avascular necrosis of the femoral head was low in our series (0% and 6.8%, respectively). This form of therapeutic management shows good clinical results with low complication rates. The slip can be efficiently stabilised, progression is reliably prevented, and remodelling of the joint gives the patient good overall hip function. We see no indication for emergency surgery.

[Retransfusion of unwashed drainage blood after total hip and knee arthroplasty]

The method of retransfusion of drainage blood as known from the literature was investigated in a prospectiv study regarding effectivness and rate of side effects. 200 patients who underwent total hip and knee arthroplasty were investigated concerning hemoglobin, hematocrit, amount and quality of the retransfused drainage blood, the amount of autologous and homologous transfusions as well as complications and costs. 100 of these patients were selected as the control group. The amount of the retransfused drainage blood after hip arthroplasty amounted an average of 387 +/- 194 ml and after knee arthroplasty 595 +/- 250 ml. The retransfused blood had an average hemoglobin of 5,2 +/- 0,9mmol/l with a hematocrit of 0,24 0,05. No complications directly associated to the retransfusion were found. The need of transfusion was reduced for patients with knee arthroplasty about 30% and for hip arthroplasty about 25%. The retransfusion of unwashed drainage blood is a sufficient method to reduce perioperative homologous blood transfusion in patients with arthroplasty of hip and knee. Substantial complications were not observed, so that this method seems to be save enough for clinical usage. The method is easy to handle and usable without special technical devices. The autologous retransfusion of drainage blood can contribute to lower costs in patients treatement.

[Bone harvesting from the iliac crest]

BACKGROUND

Autogenous bone grafts from the iliac crest are frequently harvested for autologous bone transplantation. Although an autologous bone transplant does improve the local bone healing potency, significant donor site morbidity must be considered.

METHODS

In this study we elucidate special bone harvesting techniques from the iliac crest and review the literature related to clinical significance of donor site morbidity. Furthermore, our own experiences are compared and discussed critically with relevant data of other investigators.

RESULTS

The increasing number of scientific publications which focus on bone harvesting techniques and related complications in recent years indicate the high interest and relevance of this issue. There is a tendency to alternatives such as biomaterials as bone substitutes, whereas the role of growth factors and cell therapeutics in the treatment of bony defects are still being evaluated in clinical studies.

CONCLUSION

Although autologous, heterotopic bone transplantation is still the gold standard in the treatment of bony defects, there is a tendency towards the application of biomaterials, stem cells, and growth factors. Conscientious observation of relevant anatomic considerations during bone harvesting procedures may help to avoid complications.

[Preoperative halo-traction in severe paralytic scoliosis]

AIM

During the past decades the treatment of severe paralytic scoliosis has developed towards surgical treatment. However there is controversial discussion about the need of pre-operative Halo-traction. The aim of this study was to built two groups of patients -- one group with and another one without pre-operative Halo-traction -- and to compare the results after surgical correction of scoliotic deformity with data from literature.

METHOD

Between 2000-2003 twenty-five patients with severe neuromuscular spine deformity were treated surgically. Eight patients had preoperative Halo-traction, seventeen patients underwent directly operative correction and instrumentation. The evaluation included the pre- and postoperative X-rays as well those after Halo-traction before surgery.

RESULTS

In the group without Halo-traction the scoliotic angle according to Cobb was reduced from 77 degrees to 33 degrees on average (mean correction of 44 degrees [57 %]). In the group with Halo-traction scoliosis was reduced from 85 degrees to 33 degrees on average (mean correction of 52 degrees [61 %]).

CONCLUSION

The preoperative Halo-traction in patients with severe neuromuscular scoliosis indeed leads to radiologically higher correction, but this is not significant (p = 0.19) and only in single cases clinically relevant. In our point of view except from specific indications Halo-traction should not be applied in general as a standard procedure.

Operative Therapie bei Spondylolyse und Spondylolisthese

The therapy for spondylolysis and spondylolisthesis is challenging in view of the large variety of treatment options. A general, standardized therapeutic concept has still not been established. Adequate therapy depends on different parameters and personal experience. Beside direct repair surgery of spondylolysis and low grade spondylolisthesis, dorsal, ventral and combined dorsoventral surgery, with or without instrumentation, are indicated depending on patients age and severity of the slip. Complications such as pseudarthrosis and progression of the slip develop in a given percentage of cases, but these are not significantly correlated with clinical symptoms. Decompression is necessary in high grade slippage with neurologic impairment, especially paresis. Reposition is associated with a higher risk of neurologic complications. Fusion in situ without instrumentation, even in moderate and severe spondylolisthesis, shows good clinical results with high fusion rates and without the increased risk of progression and pseudarthrosis. In many cases, it is an effective, safe and economic therapeutic option.

Deformitätenkorrektur am Unterarm bei Kindern mit multipler kartilaginärer Exostosenkrankheit

AIM

Deformity of the forearm with shortening and bowing is common in children with multiple cartilaginous osteochondromas. The objective of this study was to evaluate the benefit of ulnar lengthening using an external fixateur in these patients.

METHOD

9 patients (10 cases) underwent surgery of the forearm between 1995 and 2001 and were evaluated using a standard protocol. The mean follow-up was 33.6 months, the mean age at operation 8.9 years. All patients were treated with ulnar lengthening, in 6 cases combined with an excision of the osteochondromas.

RESULTS

Four out of ten patients did show an improvement in postoperative forearm rotation, two deteriorated and 4 presented unchanged. Wrist motion improved in 7 patients and remained unchanged in 3. The postoperative radial articular angle showed an improvement in 6, the carpal slip in 9 of the patients. The preoperative radial head dislocation in one patient remained unchanged postoperatively.

CONCLUSION

The authors advocate this therapeutic concept for the correction of forearm deformity in multiple hereditary osteochondromas to prevent a progression of the deformity and to establish carpal stability. A significant improvement of forearm and wrist function could not be reached.

Surgical treatment of congenital pseudarthrosis of the clavicle: a report of three cases and review of the literature

Congenital pseudarthrosis of the clavicle is a rare entity of unknown aetiology with predominance of the right side. Our therapeutic concept is discussed with special reference to surgical therapy, histopathological findings and the most recent literature. Two girls and one boy, aged 4, 6, and 8 years, presenting with congenital pseudarthrosis of the clavicle were surgically treated between 1994 and 2000. A resection of the pseudarthrosis and internal fixation with a small reconstruction plate was performed. A bone graft from the iliac crest was used for restoration of clavicular length. Histological examination revealed a false joint with the ends of the clavicle covered by hyaline cartilage. The patients showed radiographic healing after 12 weeks. At follow-up (mean 44 months), all patients showed excellent clinical and radiological results without functional impairment. The clinical features and histological examination of the resected pseudarthroses clearly proved the diagnosis of a true congenital pseudarthrosis of the clavicle. According to our clinical and radiological results and considering the recent literature, we recommend surgical therapy with resection, bone grafting, and osteosynthesis with a reconstruction plate around the age of 4 - 6 years.

[Multiple endocrine neoplasia type 1. Surgical therapy of primary hyperparathyroidism]

Primary hyperparathyroidism (pHPT) occurs in about 90% of patients with multiple endocrine neoplasia type 1 (MEN1). In contrast to sporadic pHPT, multiple gland disease is most common in MEN1. The appropriate surgical approach is still controversial. The aim of this study was to analyze the results of surgical therapy of pHPT in patients with genetically confirmed MEN1. In an observational study, preoperative data, operative procedures, long-term results, and a possible genotype-phenotype correlation were analyzed in patients with pHPT and genetically confirmed MEN1. According to our results, tPTX+T (total parathyroidectomy+thymectomy+autotransplantation) seems to be a more favorable surgical approach in patients with MEN1 pHPT than sDE (selective gland exstirpation) and stPTX (subtotal parathyroidectromy) without cervical thymectomy, because recurrences or persistence of the disease are rare. A prospective randomized trial is needed to compare stPTX including cervical thymectomy vs tPTX+T. A genotype-phenotype correlation could not be identified.

Prospektive Schraubenfehllagenanalyse nach konventioneller und navigierter Pedikelschraubenimplantation / Computer Assisted Orthopedic Surgery (CAOS)

BACKGROUND

[corrected] The aim of this prospective study was (1) to evaluate the accuracy of pedicle screw placement using Computer - Assisted Orthopedic - Surgery (CAOS) in comparison to conventionelly image intensifier controlled pedicle screw instrumentation, (2) to compare our results with data from literature and (3) report our experiences with this technique.

PATIENTS AND METHODS

Between 11/00 and 11/01 sixteen patients planned for spine surgery were subsequently recruited. Pedicle screw instrumentation was done in each patient as well with computer aided surgery (CAOS, SurgiGate-System, Medivision, Stratec Medical, Swiss) as also with image intensifier control, allowing for intraindividual comparison. Evaluation of pedicle screw placement was carried out with postoperative computed tomography (CT) or magnetic resonance imaging (MRI).

RESULTS

33 of altogether 36 pedicle screws inserted with Computer-Assistance (CAOS) were correctly placed (91,7%), however only 17 of altogether 24 pedicle screws inserted under image intensifier control (70,8%). The difference of frequency of screw misplacement between Computer-aided and image intensifier controlled instrumentation was statistically significant (p<0.05; chi-square test).

CONCLUSION

Computer assisted surgery reduces significantly the misplacement rate of pedicle screws and remains for experienced spine surgeons an important support in the operative treatment of complex spinal deformities in future. Additionally it can be expected that Computer-Navigation will also spread out in the field of minimal-invasive spinal surgery, e.g. the kyphoplasty. The use of this technique supports beside the medical-technical knowledge an improved three-dimensional orientation in the education of spine surgeons.

[Variations of superficial nerves at the pelvis considering orthopaedic surgical approaches]

PROBLEM

Intraoperative injuries of vessels and nerves are common risks and repeatedly described in orthopaedic pelvic surgery. Especially in pelvic osteotomies or bone harvesting procedures subcutaneous nerves are at risk for damage. In this study we elucidated the variations of subcutaneous nerves by anatomic preparation exposure with regard to the anterior and posterior spines.

METHODS

To investigate the different anatomic variations the iliohypogastrical, lateral cutaneous, subcostal and the cluneal nerves of 10 human cadavers were prepared and exposed bilaterally at the anterior, lateral and posterior pelvic region. For determination of anatomically important reference points the distance of these structures to the anterior superior spine was measured and compared with present datas in literature with respect to the ilioinguinal (Letournel) and iliofemoral (Smith- Petersen) approach.

RESULTS

We found a high variability of superficial pelvic nerves. Our findings differ somehow with datas of recent papers.

CONCLUSION

The findings of our study stress the importance of basic knowledge and thorough preparation in surgical procedures at the pelvis including harvesting bone grafts to minimize donor site morbidity.

[How reliable are data from 3d-gait analysis]

AIM

The aim of the present study was to collect preliminary data to determine the test-retest reliability in healthy subjects using 3-dimensional computerised gait analysis.

METHOD

Ten healthy subjects (6 females, 4 males) were tested using a 3-dimensional computerized gait analysis system (VICON 512, Oxford Metrics). There were two trials within a 2-hour period in which kinetic, kinematic and time-distance data were collected. Markers were removed after the first trial and reapplied for the second trial and Pearson's correlation coefficients were calculated.

RESULTS

The correlation coefficients were all positive and high for time-distance (r = 0.86-0.99), sagittal plane kinematics (r = 0.86-0.98) and power (r = 0.90-0.98) parameters, indicating excellent reliability of these measures. Correlation coefficients for frontal and transverse plane kinematics were lower (r = 0.59-0.89). The lowest correlation coefficient values were obtained for transverse plane measures at the hip joint indicating poor reliability of this measure in healthy subjects.

CONCLUSION

The results suggest excellent test-retest reliability using 3-dimensional computerized gait analysis, especially in the sagittal plane. Therefore this method is a very valuable tool in the analysis as well as in the outcome evaluation of conservative and operative procedures in movement disorders

[Computer-assisted periacetabular triple osteotomy for treatment of dysplasia of the hip]

AIM

Besides general risks, reorienting periacetabular osteotomies include the risks of over- or under-correction. Therefore, intraoperative computer-assisted control of the pelvic fragment may allow for precise reorientation of the acetabulum in all planes.

METHODS

The advantages and problems of a computer assisted periacetabular osteotomy are demonstrated in a 19 year old female with spastic paresis and severe secondary dysplasia of the hip over a postoperative follow up period of 2 years. Because of progressive subluxation of the left femoral head with initial degenerative changes of the hip joint a pelvic triple osteotomy as described by Tönnis and an intertrochanteric derotation-varus osteotomy were performed. The intraoperative control of the acetabular position was optimized by CT based navigation. To compare and evaluate the pre- and postoperative clinical and functional outcome, X-rays, CT scans and a gait analysis were applied.

RESULTS

The computer assisted orthopedic surgery (CAOS) technique allows for precise intraoperative control following reorientation of the acetabular fragment in all three planes. The pre- and postoperative clinical and radiological findings were compared and the result was classified as good.

CONCLUSION

Although the costs and logistics for pelvic osteotomies are increased by CAOS technology, the authors favor this technique for corrective surgery of complex acetabular deformities, although individual parameters need to be considered in each patient.

Die Entwicklung einer segmentalen Kyphose nach Resektion des Wirbelbogens C2 bei aneurysmatischer Knochenzyste - Krankheitsverlauf und Behandlungsstrategien

HISTORY

A 9-year-old girl suffered from an enlarging tumor in the lamina of the axis. After resection of the aneurysmatic bone cyst via laminectomy of C2 an anterior plate-fusion of C2/3 was done. Instead of a correctly placed ventral cervical plate, an adjacent instability of the level C3/4 with kyphosis and subluxation of the facet joints was seen at follow-up.

COURSE OF TREATMENT

After reposition over a hypomochlion retention was achieved with a halo body-jacket. Two weeks later the level C3/4 was stabilized by posterior instrumentation. After almost two years the patient has no complaints and the radiological controls show correctly placed instrumentation and increasing bony fusion at the levels C2/3 and C3/4.

CONCLUSION

Especially in children and adolescents laminectomy of a cervical vertebra often leads to kyphotic deformities. When using a posterior approach for surgery of intraspinal lesions or in case of tumors of the dorsal elements of the spine, the laminae and posterior structures should be preserved or, respectively, reconstructed for restoration of traction and tension mechanisms. This is of essential relevance for biomechanical stability and maintenance of the sagittal profile of the spine.

Influence of different culture solutions on osteoblastic differentiation in cord blood and bone marrow derived progenitor cells

Mesenchymal progenitor cells derived from cord blood (unrestringated somatic stem cells, USSC) and bone marrow (mesenchymal stem cells, MSC) are able to differentiate under defined culture conditions into at least bone, cartilage, adipose and muscle cells in vitro. The culture media and other in vitro conditions influence the osteogenic differentiation potency of both cell types. To increase and expand the number of osteoblasts in vitro an optimization of culture conditions is required. The aim of this study was to evaluate different culture media toward their osteogenic promoting capacity on human USSCs and MSCs in vitro. Immunohistochemical stainings against osteonectin (ON), osteopontin (OP) served as markers for an osteoblastic differentiation. Cellular morphology was analysed by light microscopy technique. We found significant differences between bone marrow and cord blood derived stem cells towards an osteoblastic differentiation. Considering the number of osteoblasts MesenCult seems to have advantages in bone marrow progenitor cells, whereas low glucose DMEM and HAMS-F12 promoted an osteoblastic differentiation in cord blood derived cells more than other tested media.