Fractionalized Z_{2} Classical Heisenberg Spin Liquids.

Quantum spin systems are by now known to exhibit a large number of different classes of spin liquid phases. By contrast, for classical Heisenberg models, only one kind of fractionalized spin liquid phase, the so-called Coulomb or U(1) spin liquid, has until recently been identified: This exhibits algebraic spin correlations and impurity moments, "orphan spins," whose size is a fraction of that of the underlying microscopic degrees of freedom. Here, we present two Heisenberg models exhibiting fractionalization in combination with exponentially decaying correlations. These can be thought of as a classical continuous spin version of a Z_{2} spin liquid. Our work suggests a systematic search and classification of classical spin liquids as a worthwhile endeavor.

Classical Spin Liquid on the Maximally Frustrated Honeycomb Lattice.

We show that the honeycomb Heisenberg antiferromagnet with J_{1}/2=J_{2}=J_{3}, where J_{1}, J_{2}, and J_{3} are first-, second-, and third-neighbor couplings, respectively, forms a classical spin liquid with pinch-point singularities in the structure factor at the Brillouin zone corners. Upon dilution with nonmagnetic ions, fractionalized degrees of freedom carrying 1/3 of the free moment emerge. Their effective description in the limit of low temperature is that of spins randomly located on a triangular lattice, with a frustrated sublattice-sensitive interaction of long-ranged logarithmic form. The XY version of this magnet exhibits nematic thermal order by disorder. This comes with a clear experimental diagnostic in neutron scattering, which turns out to apply also to the case of the celebrated planar order by disorder of the kagome Heisenberg antiferromagnet.

Spin glass behavior in a random Coulomb antiferromagnet.

We study spin glass behavior in a random Ising Coulomb antiferromagnet in two and three dimensions using Monte Carlo simulations. In two dimensions, we find a transition at zero temperature with critical exponents consistent with those of the Edwards-Anderson model, though with large uncertainties. In three dimensions, evidence for a finite-temperature transition, as occurs in the Edwards-Anderson model, is rather weak. This may indicate that the sizes are too small to probe the asymptotic critical behavior, or possibly that the universality class is different from that of the Edwards-Anderson model and has a lower critical dimension equal to three.

Maxwell electromagnetism as an emergent phenomenon in condensed matter.

The formulation of a complete theory of classical electromagnetism by Maxwell is one of the milestones of science. The capacity of many-body systems to provide emergent mini-universes with vacua quite distinct from the one we inhabit was only recognized much later. Here, we provide an account of how simple systems of localized spins manage to emulate Maxwell electromagnetism in their low-energy behaviour. They are much less constrained by symmetry considerations than the relativistically invariant electromagnetic vacuum, as their substrate provides a non-relativistic background with even translational invariance broken. They can exhibit rich behaviour not encountered in conventional electromagnetism. This includes the existence of magnetic monopole excitations arising from fractionalization of magnetic dipoles; as well as the capacity of disorder, by generating defects on the lattice scale, to produce novel physics, as exemplified by topological spin glassiness or random Coulomb magnetism.This article is part of the themed issue 'Unifying physics and technology in light of Maxwell's equations'.

[Bilateral hip joint endoprosthesis: the time interval as a prognostic parameter?]. / Doppelseitige Hüftgelenkendoprothesen: das Zeitintervall als prognostischer Parameter?

In 10-20% of patients undergoing total hip replacement bilateral replacement is necessary. This is usually done in two stages. The aim of our study was to investigate the influence of the interoperative period in bilateral hip replacement. We performed a retrospective study of 96 patients in whom bilateral hip replacement had been performed between 1974 and 1984; 72 of these patients were followed up. Assessment on follow up was based on a mobility scale, the survival time of the first prosthesis implanted was elicited from all patients. Consideration of mobility of the patients and survival time of the first prosthesis implanted revealed that the best results were obtained with an interoperative interval of between 1 and 3 years. When the interval had been shorter the mobility was less good, while patients with an interoperative period of more than 3 years had progressively less good mobility and shorter survival times of the first prosthesis. Although the range of indications for total hip replacement is not influenced by these results, the indications for replacement of the contralateral hip must be reconsidered in view of the importance of the interoperative interval.

[Conservative or surgical treatment of metacarpal fractures]. / Konservative oder operative Behandlung von Mittelhandfrakturen.

A total of 146 patients with 150 closed metacarpal fractures were treated between 1980 and 1981, and 109 patients with 113 metacarpal fractures (75%) were followed up (follow up 7.3 years). After conservative treatment, the functional results were good to excellent in 92.7%, while 5.8% had satisfactory and 1.5% poor functional results. After operative treatment 81.5% had good or excellent functional results, 14.8% satisfactory results and 3.7%, poor functional results. The radiological result did not correspond with the functional result. Angulation of the Ist-IVth metacarpal bones by up to 20 degrees of the Vth metacarpal bone by up to 50 degrees, and even shortening by up to 8 mm had no detrimental influence on the functional results. Axial rotational deviation of the Vth metacarpal bone by up to 15 degrees was tolerated. Joint fractures with a 1 mm step could also be treated by conservatively means.

[What modifies the outcome of abdominal trauma? An analysis of 558 patients]. / Was beeinflusst das Resultat von Abdominaltraumen? Eine Analyse von 558 Patienten.

A consecutive series of 558 patients with abdominal trauma were treated at "Bergmannsheil" Trauma Center in Bochum between 1974 and 1989. The most common patient group was traffic casualties with an age of up to 30 years a total of 218 (31.1%) patients underwent surgery, in which can the diagnosis was made only by surgeons. Isolated injuries were predominantly in the spleen (33%), liver (29%), mesenterium (16.1%), bowel (14.2%), and bladder and urethra (10.1%). Eighty-three of the patients who were operated on had multiple intra-abdominal injuries; 208 (37.3%) patients were included with polytrauma. Despite the increasing number of patients with multiple injuries mortality decreased from 27.1% between 1974 and 1979 to 19.7% between 1980 and 1989. This emphasizes the progress that has been made in diagnostic methods, surgical intensive care and the improved education of trauma surgeons.

[Post-traumatic correction osteotomy of the distal forearm. Which factors modify the results?]. / Posttraumatische Korrekturosteotomien am distalen Unterarm. Welche Faktoren beeinflussen das Ergebnis?

Post-traumatic deformities are a typical complication of fractures of the distal radius, occurring in about 20% of cases. They are associated with ulno-carpal pain and malfunction of the wrist. Different indications for surgery are given and various operative techniques are recommended. Between 1972 and 1987 a total of 108 patients with post-traumatic disorders following fractures of the distal radius underwent surgical treatment by one of three different procedures: isolated correction of the distal radius, combined correction of the radius und ulna, isolated correction of the ulna (distal resection, shortening osteotomy, hemiresection arthroplasty). 92 (85.2%) followed-up for an average of 9 years postoperatively was possible in 92 (85.2%) of the patients. The functional results were evaluated according to Lidström's system. Excellent and good results were found in 64 (69.6%), fair results in 22 (23.9%), and poor results in 6 (6.5%) of the patients studied. The best results were seen mainly in cases with a short time lapse between trauma and corrective surgery. Distal resection of the ulna has not been performed since 1986 because of poor results and wrist instability. Following isolated correction of radius or ulna, in some patients axial malalignment of the distal radius by about 10 degrees and/or length differences of 2-3 mm with persisting pain or malfunction were seen. In summary, we recommend the combined correction procedure in patients with painful deformities, not more than 6-9 months after the injury. The range of indications should be determined by individual aspects, such as profession, age, activity, discomfort and radiological findings.(ABSTRACT TRUNCATED AT 250 WORDS)

[Arthrolysis of post-traumatic stiff elbow. Which factors influence the end result]. / Die Arthrolyse posttraumatischer Ellenbogensteifen. Welche Faktoren beeinflussen das Endergebnis?

In a retrospective study of 59 patients the results obtained with elbow arthrolysis performed for the treatment of posttraumatic stiffness were analyzed. The intraoperative functional result was classified as excellent in all cases, while an average of 27 months after the operation the range of movement was decreased again to varying extents. This deficit correlated with the type of injury, timing of arthrolysis, duration of metal implants and timing and type of postoperative rehabilitation program. The relative increase in function was better after simple fractures, with 47%, than after fracture dislocations, with 35%. After arthrolysis within 3 months of onset of posttraumatic stiffness the range of improvement was 55%, compared with an increase of only 30% after 10 months' stiffness. When arthrolysis was combined with metal removal and the implants had been in place for longer than 9 months the increase achieved was only 15%. Patients mobilized on the 1st day postoperatively lost only 15% of their intraoperative function. If mobilization was delayed to between the 2nd and 5th days, 30% was lost. Changing splints for maximal joint flexion and extension at 4-h intervals resulted in a 35% loss of range of movement postoperatively. In contrast there was a loss of only 17% in the group with combined additional physiotherapy and continuous passive motion. The results show that the prognosis of elbow arthrolysis is determined by optimal operative planning and a meticulous rehabilitation program. The time to arthrolysis should be as short as possible, as should the time to removal of metal implants. The aim of the rehabilitation program is immediate postoperative mobilization.(ABSTRACT TRUNCATED AT 250 WORDS)

["Prognostic" analysis of late results of trochanteric femoral osteotomy following post-traumatic malalignment]. / "Prognostische" Analyse aus Spätergebnissen trochantärer Femurosteotomien nach posttraumatischen Fehlstellungen.

Post-traumatic axial malalignment of the lower limbs causes osteoarthrosis of the adjacent joints. Whether or not correction osteotomy is indicated depends upon the degree and the location of the deformity. Malalignment of the proximal femur should be corrected if the axis of the leg does not pass through the knee joint. If the axis is outside the central half of the tibial head, the indication for correction osteotomy is a relative one: varus deformities are more difficult to compensate and it is more urgent that these be corrected. Of 103 patients who underwent osteotomies of the proximal femur during the period 1973-1981, there were 73 in whom it was possible to follow up an average of 7 years after the realignment procedure. In nearly two-thirds of these patients the clinical symptoms noted before surgery had improved. In 10 cases of pseudarthrosis of the femoral neck, necrosis of the femoral head could not be avoided in spite of the surgical correction; nonetheless, the prognosis is better if the correction is done within the first 3 months after the trauma.

[Perfectionism or practicability in osteosyntheses--limits of the carefulness responsibility]. / Perfektionismus oder Praktikabilität bei Osteosynthesen--Grenzen der Sorgfaltspflicht.

The discussion of these complex themas can only partially try to show the way to successful osteosynthesis for not only the patient as also for traumatologists and orthopedic surgeons. "Perfection or practicability"-this question is to be answered so that exaggerated perfection, as seen overall in surgery, is not foundation of the successful result. On the contrary, osteosynthesis procedures conceived so that they are generally practicable and employable for those colleagues who are experienced and have confidence with the material. Perfection should not be isolated as bare organ surgery. At the same time it is clearer that it is not possible to stop the specialization in bone surgery. In its place arises the necessity of an interdisciplinary cooperation of all surgical specialties. These demands will justify our current concept of treatment under the condition that the surgeon realizes his limitations in difficult situations and behaves accordingly. Practicable and even to perfection is however the relationship of the bone surgeon to the patient who is injured in an accident. The professional assessment of the true or the apparent failures after osteosynthesis must observe the written laws. Mistakes, which reveal the ignorance and which grossly contradict the limiting prerequisites of the guidelines for the execution of osteosynthesis are to be appraised as such. The professional consultant, himself, must be so confident with the practice of osteosynthesis so that he can implement an objective and critical estimation of the situation.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pathologic fractures of the hip joint]. / Pathologische Frakturen am Hüftgelenk.

28 patients underwent surgical treatment because of pathological fractures of the hip joint. 13 patients suffered from fractures of the femur because of benign tumours, whereas surgical treatment became necessary because of malignant tumours or because of fractures caused by metastases in 15 patients. Special attention is drawn to six patients out of the latter group. In these cases, spontaneous femoral fracture was caused by weakness subsequent to irradiation of malignant genital tumours. The results of our treatment were generally good in the first group. Poor results or even failure of treatment occurred comparatively often in the patients of the second group. The patients of the second group underwent surgical treatment mainly to reduce or eliminate pain, to regain mobility, to facilitate care and, last but not least, to shorten the hospitalisation period. Whenever possible, we tried to carry out complete surgery in both groups in respect of stability and function, because we believe that combined surgical and chemotherapeutical treatment can relieve the effects and arrest the progress of malignant disease and may exercise an influence on the survival time.

Morphologic aspects of bone healing after third-degree open fractures. An experimental study.

The morphologic aspects of undisturbed and disturbed bone healing following third-degree open fractures is demonstrated by means of experimental investigations using animals. As an experimental model we used a canine thigh fractured by a shot. The data was obtained as part of bioballistic investigations of the effect of highvelocity bullets in living tubular bones. The shot fracture was immobilized by external fixation. Progressive radiological controls, as well as microangiographic, microradiographic and histological findings are used to show bone healing. Bone healing following shot fractures follows the basic pattern of secondary bone healing, which is manifested in an X-ray by the formation of periosteal callus. The periosteal callus tissue has its own vascular system and receives blood from the extraosseous vessels of the adjacent soft tissue surrounding it. It not only fulfills the function of the biological stabilizer of the fragments, but also contributes decisively to their revascularization through transcortical anastomosis. The morphologic appearance and the causes for the disruption of bone healing are demonstrated using individual examples. Predominant are insufficient stability and above all circulatory disturbances. In the case of fractures with considerable soft-tissue damage, not only is the intramedullary vascular system destroyed, but the blood supply to the periosteal vessels is also disrupted. The resulting delay to or absence of callus formation leads on the one hand to insufficient biological stabilization, and on the other hand to an impairment of fragment revascularization. The morphologic appearance is dominated by the fragment necroses and related complications, such as pseudarthrosis induced by bone necrosis and infected pseudarthrosis.

[Corrective measures following imperfectly healed fractures]. / Korrektureingriffe nach fehlverheilten Frakturen.

An overview of forms and localization of falsely healed fractures and possibilities for their correction is presented. In contrast to statically loaded lower limbs, posttraumatic arthrosis due to false position of the upper limbs is less common. In these cases indication for corrective osteotomy is aimed above all at improving the limb function. Central restorative measures are corrective osteotomy following falsely healed supracondylar humerus fractures in childhood and open wedge osteotomy of distal radius fractures. Even minimal axial deviations in the lower limbs will lead to false loading of joint surfaces and to early arthrosis, thus corrective osteotomy is indicated at a much earlier stage.