Solving condensed-matter ground-state problems by semidefinite relaxations

We present a generic approach to the condensed-matter ground-state problem which is complementary to variational techniques and works directly in the thermodynamic limit. Relaxing the ground-state problem, we obtain semidefinite programs (SDP). These can be solved efficiently, yielding strict lower bounds to the ground-state energy and approximations to the few-particle Green's functions. As the method is applicable for all particle statistics, it represents, in particular, a novel route for the study of strongly correlated fermionic and frustrated spin systems in D>1 spatial dimensions. It is demonstrated for the XXZ model and the Hubbard model of spinless fermions. The results are compared against exact solutions, quantum Monte Carlo calculations, and Anderson bounds, showing the competitiveness of the SDP method.

[Minimally invasive retrograde drilling of osteochondral lesions of the femur using an arthroscopic drill guide]

OBJECTIVE

Retrograde drilling for penetration of subchondral sclerotic bone in osteochondrosis dissecans (OCD) of the femoral condyle with preserved cartilage integrity. Hereby, revascularization of the OCD and immigration of bone marrow cells to achieve stable reintegration of the OCD into the surrounding subchondral bone.

INDICATIONS

Stable juvenile and adult osteochondrosis dissecans (stage I-II of the International Cartilage Repair Society (ICRS) classification) of the medial and lateral femoral condyle with an intact articular surface and surrounding sclerosis zone, which is visible in the x-ray.

CONTRAINDICATIONS

OCD stage III-IV of the ICRS grading scale. Relative contraindication: preceding retrograde drilling.

SURGICAL TECHNIQUE

Arthroscopic inspection and palpation of the cartilage defect. Minimal incision over the M. vastus medialis (when the defect is located in the medial condyle) or the M. vastus lateralis (when the defect is located in the medial condyle). Preparation and dissection of the fascia of the vastus muscle. Insertion of retractors underneath the vastus muscle to expose the metaphysis of the distal femur. Intraarticular positioning of the arthroscopic drill guide, placement of the wire guide and a Kirschner(K) wire on the femur metaphysis and retrograde drilling with a 2.0-2.2 mm K wire under radiographic visualization. Length measurement of the intraosseous wire distance. Switch the guide mechanism to a multiple hole drill guide and, depending on the defect size, insertion of a further 7-10 K wires of same thickness and defined length.

POSTOPERATIVE MANAGEMENT

Sterile bandage and slightly compressive dressing. Continuous active and passive knee motion. Weight bearing of 20 kg for 6 weeks, with subsequent transition to continuous weight bearing. Radiographic controls at 6 and 12 weeks postoperatively. In case of a persistent sclerosis zone in the control x-ray or clinical abnormalities, control MRI is indicated.

RESULTS

A total of 55 patients with a mean age of 19.6 years were treated using the described technique: 49 patients (89.1%), and 54 knees respectively (35 juvenile OCD, 19 adult OCD), were seen with a mean follow-up of 37.9 months. An improvement was observed in 81.6% of the knees using the radiographic score, i.e., a mean improvement of 1.13 of the radiographic score published by Rodegerdts and Gleissner (preoperative 3.04 vs. postoperative 1.91). Juvenile OCD showed better radiographic results overall (88.2% healing) than adult OCD (66.7% healing).

A prospective multicenter study on the outcome of type I collagen hydrogel-based autologous chondrocyte implantation (CaReS) for the repair of articular cartilage defects in the knee

BACKGROUND

The Cartilage Regeneration System (CaReS) is a novel matrix-associated autologous chondrocyte implantation (ACI) technique for the treatment of chondral and osteochondral lesions (Outerbridge grades III and IV). For this technology, no expansion of the chondrocytes in a monolayer culture is needed, and a homogeneous cell distribution within the gel is guaranteed.

PURPOSE

To report a prospective multicenter study of matrix-associated ACI of the knee using a new type I collagen hydrogel (CaReS).

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

From 2003 to 2008, 116 patients (49 women and 67 men; mean age, 32.5 ± 8.9 years) had CaReS implantation of the knee in 9 different centers. On the basis of the International Cartilage Repair Society (ICRS) Cartilage Injury Evaluation Package 2000, the International Knee Documentation Committee (IKDC) score, pain score (visual analog scale [VAS]), SF-36 score, overall treatment satisfaction and the IKDC functional status were evaluated. Patient follow-up was performed at 3, 6, and 12 months after surgery and annually thereafter. Mean follow-up was 30.2 ± 17.4 months (range, 12-60 months). There were 67 defects of the medial condyle, 14 of the lateral, 22 of the patella/trochlea, and 3 of the tibial plateau, and 10 patients had 2 lesions. The mean defect size was 5.4 ± 2.4 cm(2). Thirty percent of the defects were <4 cm(2) and 70% were >4 cm(2).

RESULTS

The IKDC score improved significantly from 42.4 ± 13.8 preoperatively to 70.5 ± 18.7 (P < .001) at latest follow-up. Global pain level significantly decreased (P < .001) from 6.7 ± 2.2 preoperatively to 3.2 ± 3.1 at latest follow-up. There also was a significant increase of both components of the SF-36 score. The overall treatment satisfaction was judged as very good or good in 88% by the surgeon and 80% by the patient. The IKDC functional knee status was grade I in 23.4%, II in 56.3%, III in 17.2%, and IV in 3.1% of the patients.

CONCLUSION

Matrix-associated ACI employing the CaReS technology for the treatment of chondral or osteochondral defects of the knee is a safe and clinically effective treatment that yields significant functional improvement and improvement in pain level. However, further investigation is necessary to determine the long-term viability and clinical outcome of this procedure.

Dissipative quantum Church-Turing theorem

We show that the time evolution of an open quantum system, described by a possibly time dependent Liouvillian, can be simulated by a unitary quantum circuit of a size scaling polynomially in the simulation time and the size of the system. An immediate consequence is that dissipative quantum computing is no more powerful than the unitary circuit model. Our result can be seen as a dissipative Church-Turing theorem, since it implies that under natural assumptions, such as weak coupling to an environment, the dynamics of an open quantum system can be simulated efficiently on a quantum computer. Formally, we introduce a Trotter decomposition for Liouvillian dynamics and give explicit error bounds. This constitutes a practical tool for numerical simulations, e.g., using matrix-product operators. We also demonstrate that most quantum states cannot be prepared efficiently.

Mesenchymal stem cell characteristics of human anterior cruciate ligament outgrowth cells

When ruptured, the anterior cruciate ligament (ACL) of the human knee has limited regenerative potential. However, the goal of this report was to show that the cells that migrate out of the human ACL constitute a rich population of progenitor cells and we hypothesize that they display mesenchymal stem cell (MSC) characteristics when compared with adherent cells derived from bone marrow or collagenase digests from ACL. We show that ACL outgrowth cells are adherent, fibroblastic cells with a surface immunophenotype strongly positive for cluster of differentiation (CD)29, CD44, CD49c, CD73, CD90, CD97, CD105, CD146, and CD166, weakly positive for CD106 and CD14, but negative for CD11c, CD31, CD34, CD40, CD45, CD53, CD74, CD133, CD144, and CD163. Staining for STRO-1 was seen by immunohistochemistry but not flow cytometry. Under suitable culture conditions, the ACL outgrowth-derived MSCs differentiated into chondrocytes, osteoblasts, and adipocytes and showed capacity to self-renew in an in vitro assay of ligamentogenesis. MSCs derived from collagenase digests of ACL tissue and human bone marrow were analyzed in parallel and displayed similar, but not identical, properties. In situ staining of the ACL suggests that the MSCs reside both aligned with the collagenous matrix of the ligament and adjacent to small blood vessels. We conclude that the cells that emigrate from damaged ACLs are MSCs and that they have the potential to provide the basis for a superior, biological repair of this ligament.

Real-space renormalization yields finite correlations

Real-space renormalization approaches for quantum lattice systems generate certain hierarchical classes of states that are subsumed by the multiscale entanglement renormalization Ansatz (MERA). It is shown that, with the exception of one spatial dimension, MERA states are actually states with finite correlations, i.e., projected entangled pair states (PEPS) with a bond dimension independent of the system size. Hence, real-space renormalization generates states which can be encoded with local effective degrees of freedom, and MERA states form an efficiently contractible class of PEPS that obey the area law for the entanglement entropy. It is further pointed out that there exist other efficiently contractible schemes violating the area law.

Snapping elbow caused by hypertrophic synovial plica in the radiohumeral joint: a report of three cases and review of literature

The snapping elbow caused by hypertrophic synovial radiohumeral plica is a rare form of lateral elbow impingement. In this article we report on hypertrophic radiohumeral synovial folds in three male patients, aged 54, 65 and 27 years. All three patients suffered isolated lateral elbow pain, painful snapping and unsuccessful conservative treatment over at least 5 months (range 5-9 months, mean 7.7 months) prior to surgical treatment. None of the patients had lateral epicondylitis, instability, osteochondrosis dissecans, loose bodies, arthritis or neurological disorders. Upon clinical examination the range of motion in the respective painful elbows was found to be normal in all three cases, but a painful snapping occurred between 80 degrees and 100 degrees of flexion with the forearm in pronation. While there were no pathologic findings in standard radiographs, magnetic resonance imaging (MRI) revealed hypertrophic synovial plicae in the radiohumeral joints associated with effusion in each of the diseased elbows. Arthroscopic examinations confirmed the presence of a hypertrophic synovial plica in all three radiocapitellar joints, and revealed a transient interposition and compression of the folds in the articulation from extension until 90 degrees -100 degrees elbow flexion, with replacement beyond 90 degrees elbow flexion with a visible jump. Surgical management in all three cases comprised arthroscopic diagnosis confirmation and removal of the synovial plicae, leading to excellent outcomes at 6-12 months follow-up.

Predictive formula for the length of tibial tunnel in anterior crucitate ligament reconstruction

BACKGROUND

The anterior cruciate ligament (ACL) reconstruction using bone-patellar tendon bone graft is a common procedure in orthopedics. One challenging problem found is a graft-tunnel mismatch. Previous studies have reported the mathematic formula to predict the tibial angle length and angle to avoid graft-tunnel mismatch but these formulas have shown limited predictability.

OBJECTIVE

To propose a predictive formula for the length of tibial tunnel and to examine its predictability.

MATERIAL AND METHOD

Thirty six patients (26 males, 14 females) with ACL injury were included in this study. The preoperativemedial proximal tibial angle was measured. Intraoperatively, the tibial tunnel length and tibial entry point were measured. The postoperative coronal and saggital angle of tibial tunnel were measured from knee radiograph. The data were analysed by using trigonometry correlation and formulate the predictive formula of tibial tunnel length.

RESULTS

We found that tibial tunnel length (T) has trigonometric correlation between the location of tibial tunnel entry point (w), coronal angle of tibial tunnel (b), saggital angle of tibial tunnel (a) and the medial proximal tibial slope (c) by using this formula T = Wcos(c)tan(b)/sin(a)

CONCLUSION

This proposed predictive formula can well predict the length of the tibial tunnel at preoperative period to avoid graft-tunnel mismatch.

Influence of phosphatidylserine on cognitive performance and cortical activity after induced stress

The aim of this study was to investigate the effect of phosphatidylserine (PS) on cognition and cortical activity after mental stress. After familiarization, 16 healthy subjects completed cognitive tasks after induced stress in a test-re-test design (T1 and T2). Directly after T1, subjects were assigned double-blind to either PS or placebo groups followed by T2 after 42 days. At T1 and T2, cortical activity was measured at baseline and immediately after stress with cognitive tasks using electro-encephalography (EEG). EEG was recorded at 17 electrode positions and fast Fourier transforms (FFT) determined power at Theta, Alpha-1, Alpha-2, Beta-1 and Beta-2. Statistics were calculated using ANOVA (group x trial x time). The main finding of the study was that chronic supplementation of phosphatidylserine significantly decreases Beta-1 power in right hemispheric frontal brain regions (F8; P < 0.05) before and after induced stress. The results for Beta-1 power in the PS group were connected to a more relaxed state compared to the controls.

Dephasing and the steady state in quantum many-particle systems

We discuss relaxation in bosonic and fermionic many-particle systems. For integrable systems, time evolution can cause a dephasing effect, leading for finite subsystems to steady states. We explicitly derive those steady subsystem states and devise sufficient prerequisites for the dephasing to occur. We also find simple scenarios, in which dephasing is ineffective and discuss the dependence on dimensionality and criticality. It follows further that, after a quench of system parameters, entanglement entropy will become extensive. This provides a way of creating strong entanglement in a controlled fashion.

VAP-1, Eotaxin3 and MIG as potential atherosclerotic triggers of severe calcified and stenotic human aortic valves: Effects of statins

Sclerotic calcification of the aortic valve is a common disease in advanced age. Its pathophysiology is unclear. However, pathobiological similarities to atherosclerosis have been shown in several studies. The current study assesses gene profiling of severe calcified stenotic human aortic valves identifying transforming growth factor (TGF)-beta, Eotaxin3, vascular adhesion protein-1 (VAP-1) and monokine induced by interferon-gamma (MIG) as potential atherosclerotic target genes in severe calcified and stenotic aortic valves, and analyzes the effects of statins on their expression as part of an anti-inflammatory treatment strategy. We collected human severe calcified and stenotic aortic valves with (CSAV+) or without (CSAV-) statin pre-treatment prior to valve replacement and investigated gene profiling by using micro-array technique and real-time PCR for the TGF-beta, Eotaxin3, VAP-1 and MIG expression. In comparison to atherosclerotic plaques of carotid arteries, immunohistochemical staining was investigated. Results were contrasted to human normal non-calcified aortic valves as controls (C). As compared to C, TGF-beta, Eotaxin3, MIG or VAP-1 was significantly upregulated in CSAV-. In CSAV+ no significant change in gene expression was found for Eotaxin3 and MIG. In contrast, VAP-1 and TGF-beta were still upregulated. Corresponding gene expression was confirmed on atherosclerotic plaque formations of carotid arteries. Monocyte/Macrophage infiltration (presence of CD68) on aortic valves (CSAV+, CSAV-, or C) confirmed inflammatory nature of the disease. Our data support further evidence for atherosclerotic inflammation as a trigger for sclerosis in end-stage calcified stenotic aortic valves by showing upregulation of gene expression for TGF-beta, VAP-1, MIG and Eotaxin3, which is only partially inhibited by previous statin therapy. Potent benefits of statin treatment on early stages of valve disease are still propagated.

9- to 11-year results of cemented titanium mueller straight stem in total hip arthroplasty

This retrospective study reviewed 9- to 11-year results after total hip arthroplasty (THA) with cemented titanium stems (Mueller-Straight-Stem). Ninety-one patients (110 hips) were examined clinically and radiologically at an average 9.5-year follow-up. Revisions for aseptic loosening were performed in 4 (4%) patients. Subsidence or varus position could only be observed in one of these patients. Radiolucent lines were found in 37 patients, mainly located around the proximal zones of the stem (zone 1, 7, 8, and 14). Harris scores were good or excellent in 78% and satisfactory in 20% of patients. The 9.5-year survival rate of the cemented titanium stem with regard to aseptic loosening was 96.4%. Body weight was significantly higher (88 +/- 5.4 kg) in the 4 patients with aseptic loosening, compared to patients without radiolucent lines (75 +/- 15 kg). The body weight to stem surface ratio showed a significant difference (1.5 kg/cm2 versus 1 kg/cm2; P < .05). No significant differences were found in other factors, including sex, size or type of stem, Harris score, heterotopic ossification, or body mass index. Good long-term results can be achieved with cemented titanium stem implants. This titanium implant is recommended for patients with hypersensitivity to chrome, cobalt, and nickel. mplanting the biggest possible stem seems to be most beneficial.

Entanglement entropy beyond the free case

We present a perturbative method to compute the ground state entanglement entropy for interacting systems. We apply it to a collective model of mutually interacting spins in a magnetic field. At the quantum critical point, the entanglement entropy scales logarithmically with the subsystem size, the system size, and the anisotropy parameter. We determine the corresponding scaling prefactors and evaluate the leading finite-size correction to the entropy. Our analytical predictions are in perfect agreement with numerical results.

Anterior cruciate ligament constructs fabricated from human mesenchymal stem cells in a collagen type I hydrogel

BACKGROUND

Disruptions of the anterior cruciate ligament (ACL) of the knee joint are common and are currently treated using ligament or tendon grafts. In this study, we tested the hypothesis that it is possible to fabricate an ACL construct in vitro using mesenchymal stem cells (MSC) in combination with an optimized collagen type I hydrogel, which is in clinical use for autologous chondrocyte transplantation (ACT).

METHODS

ACL constructs were molded using a collagen type I hydrogel containing 5 x 10(5) MSC/mL and non-demineralized bone cylinders at each end of the constructs. The constructs were kept in a horizontal position for 10 days to allow the cells and the gel to remodel and attach to the bone cylinders. Thereafter, cyclic stretching with 1 Hz was performed for 14 days (continuously for 8 h/day) in a specially designed bioreactor.

RESULTS

Histochemical analysis for H and E, Masson-Goldner and Azan and immunohistochemical analysis for collagen types I and III, fibronectin and elastin showed elongated fibroblast-like cells embedded in a wavy orientated collagenous tissue, together with a ligament-like extracellular matrix in the cyclic stretched constructs. No orientation of collagen fibers and cells, and no formation of a ligament-like matrix, could be seen in the non-stretched control group cultured in a horizontal position without tension. RT-PCR analysis revealed an increased gene expression of collagen types I and III, fibronectin and elastin in the stretched constructs compared with the non-stretched controls.

DISCUSSION

In conclusion, ACL-like constructs from a collagen type I hydrogel, optimized for the reconstruction of ligaments, and MSC have been fabricated. As shown by other investigators, who analyzed the influence of cyclic stretching on the differentiation of MSC, our results indicate a ligament-specific increased protein and gene expression and the formation of a ligament-like extracellular matrix. The fabricated constructs are still too weak for animal experiments or clinical application and current investigations are focusing on the development of a construct with an internal augmentation using biodegradable fibers.

Ultrasonography for intraoperative control of the amount of bone resection in arthroscopic acromioclavicular joint resection

Remaining superior osteophytes or osseous spurs after arthroscopic lateral clavicle resection can cause persistent pain and could lead to revision surgery. A new method of intraoperative ultrasonographic imaging of the result of the operation during arthroscopic lateral clavicle resection is presented. In 10 patients with acromioclavicular arthritis, standardized arthroscopic lateral clavicle resection was performed. Intraoperatively, the space between the clavicle and the acromion was measured before and after arthroscopic acromioclavicular resection using a Sonosite 180 plus (SonoSite, Bothell, WA) with a 10-MHz broadband linear array in a sterile bag. The width of the joint space between the clavicle and the acromion was between 0.38 and 0.56 cm before operation and 0.92 cm and 1.28 cm after operation (nine cases). In one case, the anticipated minimum resection of 0.5 cm was not achieved at the sonographic measurement and further resection was required. Real-time ultrasonography allows exact measurement of the amount of resected bone during arthroscopic lateral clavicle resection. This could avoid revision surgery resulting from persisting disability caused by insufficient or extensive bone resection.

[Anatomy of the glenoid labrum]

Most instabilities or pain syndromes are associated with injuries or morphologic changes in the glenoid labrum complex or long head of the biceps tendon origin. The first anatomic descriptions go back to Fick in 1910 and since then many authors have described the anatomy of these structures. It was Snyder who introduced the term SLAP lesions, classifying superior, anterior, posterior labrum changes into four grades. It is still unclear whether all of the described and arthroscopically observed changes are due to a post-traumatic, acquired lesion or whether anatomic variations can be present as well. In order to elucidate this problem, 36 cadaver shoulder joints were inspected macroscopically and sectioned for microscopic evaluation. Here the glenoid could be divided into an superior and an anterior- superior area demonstrating a wide variety of morphologic labral glenoid changes, while the dorsal and inferior sectors of the glenoid showed a relatively uniform anatomy of a firm labrum-glenoid bond. Four types of biceps tendon attachments could be identified similar to the description given by Vangsness. In addition, a variety of anterior-superior changes could be found. The sublabral hole as described by Esch in the clinical setting was found to be a physiologic variant. Precise knowledge of the anatomic morphology of the normal glenoid in its variations seems to be necessary to understand variants and allow for distinguishing between physiologic anatomic variants and pathoanatomic changes in imaging and the clinical setting.

Prophylaxis of heterotopic ossification after total hip arthroplasty: a prospective randomized study comparing indomethacin and meloxicam

We performed a randomized, prospective study on the prophylaxis of heterotopic ossification (HO) after total hip arthroplasty (THR), comparing indomethacin and the selective COX-2 inhibitor meloxicam. From the day after surgery, 272 patients were treated with 7.5 mg meloxicam, 15 mg meloxicam, or 2 x 50 mg indomethacin a day, for 14 days. After 6 months, radiographs of patients treated with 7.5 mg meloxicam showed that HO had occurred in one third. This treatment was therefore stopped after 26 patients have been assigned to this group. According to the intention-to-treat principle, patients given 15 mg meloxicam developed HO in 25% (20% Brooker grade I, 4% grade II and 1% grade III) and those given indomethacin in 10% (7% Brooker grade I, 1% grade II and 2% grade III), a statistically significant difference.

Biomechanical evaluation of braces used for the treatment of epicondylitis

The purpose of the study was to investigate the biomechanical effects of different types of braces that are used in the treatment of patients with epicondylitis radialis. Vibration and acceleration of the forearm and the elbow were measured with sensors taped to defined anatomic points on the skin surface. The impact-induced vibration of the racket-arm system was analyzed while the subjects were playing tennis. Different designed brace systems were investigated with respect to acceleration amplitudes and acceleration integrals. Clasp-based brace systems showed a slight reduction of acceleration amplitudes (-6%) and acceleration integrals (-8%). Braces with pads at the lateral epicondyle reduced acceleration amplitudes by 20% and acceleration integrals by 22%. Braces with pads placed at the forearm showed the highest reduction of acceleration amplitudes (-46%) and acceleration integrals (-42%). Overload of the wrist extensors, which is considered to be a major pathogenic factor in lateral epicondylitis, can be reduced by braces. There is a significant difference in the effects among different biomechanical principles of braces.

Arthroscopic treatment of septic joints: prognostic factors

From 1987 to 1993, 88 patients (average age 48 years, range 3 months to 83 years) with septic arthritis were treated at the orthopaedic clinic König Ludwig Haus of the University of Würzburg by arthroscopic means consisting of joint debridement and application of suction drains, combined with appropriate antibiotics and early functional treatment. The series consisted of 78 knees, 8 shoulders and 3 ankles. At the first visit to our clinic, patients typically presented with fever, leucocytosis, elevated sedimentation rate and localized findings in almost every joint involved (generalized tenderness, swelling, effusion, painful and limited range of motion). All the patients were taken to the operating room on an emergency basis. Broad-spectrum antibiotics were given before the initial culture was evaluated, and its sensitivity was determined. Recovery from arthritis by elimination of joint effusion and disappearance of the inflammatory syndrome occurred in all the joints except for 3 (1 knee joint and 2 shoulders). The number of arthroscopic procedures needed to become free from infection depended on the one hand on the time between onset of symptoms and arthroscopic surgery and on the other on the kind of microorganism discovered. At the average follow-up evaluation after 2.5 years (range 6 months to 5 years), the functional results were excellent or good in 61% of the patients, satisfactory in 20% and poor in 19% from our series. This functional outcome depends on the degenerative changes of the joint before infection, patient's age, and the time interval between onset of symptoms and surgical intervention; indirectly, the time lapse between the onset of infection and surgical intervention also had an influence on the intraoperative macroscopic appearance.

Readiness potential in different states of physical activation and after ingestion of taurine and/or caffeine containing drinks

To investigate the influence of taurine and caffeine containing drinks and physical stress on the cortical movement-preparation, the readiness potentials or "Bereitschaftspotentiale" (BPs), preceding voluntary self-placed pedalling movements, were examined after different states of exhaustion on an ergometer. 15 (13 right-handed) healthy men, aged between 22-30, participated in a randomised, cross over, double-blind, placebo controlled study. BPs were averaged out of artefact free EEG-segments from more than 90 triggered events, measured at 17 electrodes of the 10:20 system. With increasing effort the BPs were enlarged differently depending on the drink consumed. In placebo trials after exhaustive exercise premovement negative potential curves could be seen even in frontal areas. With caffeine the BPs increased after lower workload, achieving a level, which was reached in the placebo trials only after submaximal physical activation. Furthermore a significant shortening of premovement-brain-potentials in frontal and parietal regions could be seen in the caffeine trials at rest. Taurine admixture seems to inhibit this effects.