Adjacent End Research Articles

Lateral Lumbar Interbody Fusion

A retrospective review of patients' radiographs and charts. The various methods of lumbar interbody fusion have been described in the literature. With the development of the lateral lumbar interbody fusion (LLIF) approach, a wider cage can be inserted in the intervertebral space without disrupting the anterior-posterior annulus or longitudinal ligament, with minimal danger to the retroperitoneal structures and the great vessels. There is a paucity of the literature on the radiographic and clinical outcome of this approach. The purpose of this study is to assess the radiographic change in the coronal and sagittal plane alignment of the lumbar spine after the LLIF approach using XLIF cages (Nuvasive, Inc, San Diego, CA). Radiographic and clinical outcomes, and complications associated with the approach are also described. A retrospective review of 43 consecutive patients' preoperative, immediate postoperative, and 1-year follow-up radiographs was done. All patients had LLIF procedure performed for lumbar degenerative disc disease, spondylolisthesis, or de novo scoliosis. The radiographic measurements were taken to assess change in the sagittal and coronal plane alignment of the individual instrumented disc level, overall lumbar spine, and lumbar scoliotic curves. The radiographs were also analyzed for fusion at 1 year, end-plate fracture, and other complications. The patients' hospital and clinic charts were reviewed to identify the complications and patient outcomes. There was a mean correction of 3.7 degrees (P≤0.001) at each instrumented disc level in coronal plane in 87 instrumented levels. Similarly, there was a mean gain of 2.8 degrees (P≤0.001) of lordosis at each level. In 25 patients with lumbar scoliosis (>10 degrees), mean scoliosis angle correction was 10.4 degrees (P=0.001, 43%). There was no significant change in the overall coronal or sagittal plane alignment of the lumbar spine. The most common postoperative complication (25%) was anterior thigh pain, which was transitory in the majority of cases. End-plate breach was common at the instrumented disc levels; however, it was nonprogressive in most of the cases, and did not affect the fusion or alignment at the instrumented levels. The outcome scores were improved significantly at the final follow-up. The LLIF approach is effective in correcting the coronal plane deformity and in gaining lordosis at individual instrumented levels. They parallelize adjacent end plates to correct the lumbar scoliotic curves. The complications are mostly approach-related and transitory. A larger cohort with long-term follow-up is required to establish the advantages and shortcomings of the procedure.

Strengthening multiple span simply-supported girder bridges using post-tensioned negative moment connection technique

A post-tensioned negative moment connection technique is proposed to strengthen old multiple span simply-supported T-section reinforced concrete (RC) girders. In this technique, old concrete is removed from girder ends and flanges, a diaphragm is placed between the two adjacent girder ends over the interior support and negative moment steel strands are installed in new cast-in-place concrete and post-tensioned to make continuity. A total of six two-span simply-supported T-section RC girders were cast and five of them strengthened using the provision of the proposed post-tensioned negative moment connections. Both laboratory tests and nonlinear finite element (FE) analysis were conducted to investigate the structural performance of the strengthened RC girders. The moment redistribution in the strengthened continuous RC girders was also measured and is discussed. It is shown that the proposed post-tensioned moment connection technique can reliably transfer the negative moment over the support and markedly increase member stiffness and the load-carrying capacity of existing multiple span simply-supported RC girders. The validity of the FE analysis was also demonstrated through comparisons with experimental results.

Vertebral Osteomyelitis

Vertebral osteomyelitis can be caused by a variety of microorganisms. The hematogenous pyogenic form is characteristically a disease of people over age 50, predominantly in the male population, and most frequently caused by S. aureus. In IVDAs, however, younger patients and a heavier predominance of males are seen, and P. aeruginosa is one of the most commonly seen pathogens. The disease is generally monomicrobial, unless it is secondary to a contiguous process such as a pressure sore, in which polymicrobial infection with participation of anaerobes is the general rule. Lumbar, greater than thoracic, greater than cervical involvement is the rule in the general population, but cervical spine involvement is frequently seen more often than thoracic involvement in IVDAs. Diabetic patients are over-represented among patients with vertebral osteomyelitis, and they also have a tendency for higher morbidity and mortality. Simultaneous involvement of adjacent vertebral end plates and the intervening disk is the general rule. The vertebrae are generally involved, and the posterior elements of the spine are involved infrequently. Posterior element involvement is seen more commonly in actinomycosis, coccidioidomycosis, and neoplasms. Newer diagnostic modalities, such as CT, MRI, and radionuclide scans, may detect the disease earlier than conventional radiographs. Immunobilization by bed rest and appropriate antimicrobial therapy are generally sufficient in the therapy of pyogenic, as well as tuberculous, vertebral osteomyelitis. In selected circumstances, such as in the presence of marked instability of the spine, the presence of new neurologic deficits, or with progression of previous neurologic deficits, surgical intervention may be necessary. With prompt diagnosis and proper management, the prognosis should generally be good.

In vitro biomechanics of an expandable vertebral body replacement with self-adjusting end plates

Background context Unstable burst fractures of the thoracolumbar spine may be treated surgically. Vertebral body replacements (VBRs) give anterior column support and, when used with supplemental fixation, impart rigidity to the injured segments. Although some VBRs are expandable, device congruity to the vertebral end plates is imprecise and may lead to stress risers and device subsidence. Purpose The objective of this study was to compare the rigidity of a VBR that self-adjusts to the adjacent vertebral end plates versus structural bone allograft and with an unsupported anterior column in a traumatic burst fracture reconstruction model. Study design Biomechanical flexibility testing with rod strain measurement. Patient sample Twelve T11–L3 human spine segments. Outcome measures Range of motion, neutral zone, and posterior fixation rod stress (moments). Methods Flexibility testing was performed to±6 Nm in flexion-extension, lateral bending, and axial rotation on 12 intact human T11–L3 specimens. Burst fractures were created in L1, and flexibility testing was repeated in three additional states: subtotal corpectomy with posterior instrumentation (PI) only from T12 to L2, reconstruction with a femoral strut allograft and PI, and reconstruction with a VBR (with self-adjusting end plates) and PI. The PI consisted of pedicle screws and strain gage instrumented rods that were calibrated to measure rod stress via flexion-extension bending moments. Results There was no statistical difference in range of motion or neutral zone between the strut graft and VBR constructs, which both had less motion than the PI-only construct in flexion/extension and torsion and were both less than the intact values in flexion/extension and lateral bending (p<.05). Posterior rod moments were significantly greater for the PI-only construct in flexion/extension relative to the strut graft and VBR states (p=.03). Conclusions This study, which simulated the immediate postoperative state, suggests that a VBR with self-adjusting end plate components has rigidity similar to the standard strut graft when combined with PI. Posterior rod stress was not significantly increased with this type of VBR compared with the strut graft reconstruction. The benefits of burst fracture stabilization using a self-adjusting VBR ultimately will not be known until long-term clinical studies are performed.

The carboxyterminal EF domain of erythroid α-spectrin is necessary for optimal spectrin-actin binding

AbstractSpectrin and protein 4.1R crosslink F-actin, forming the membrane skeleton. Actin and 4.1R bind to one end of β-spectrin. The adjacent end of α-spectrin, called the EF domain, is calmodulin-like, with calcium-dependent and calcium-independent EF hands. The severely anemic sph1J/sph1J mouse has very fragile red cells and lacks the last 13 amino acids in the EF domain, implying that the domain is critical for skeletal integrity. To test this, we constructed a minispectrin heterodimer from the actin-binding domain, the EF domain, and 4 adjacent spectrin repeats in each chain. The minispectrin bound to F-actin in the presence of native human protein 4.1R. Formation of the spectrin-actin-4.1R complex was markedly attenuated when the minispectrin contained the shortened sph1J α-spectrin. The α-spectrin deletion did not interfere with spectrin heterodimer assembly or 4.1R binding but abolished the binary interaction between spectrin and F-actin. The data show that the α-spectrin EF domain greatly amplifies the function of the β-spectrin actin-binding domain (ABD) in forming the spectrin-actin-4.1R complex. A model, based on the structure of α-actinin, suggests that the EF domain modulates the function of the ABD and that the C-terminal EF hands (EF34) may bind to the linker that connects the ABD to the first spectrin repeat.

A modified fluorescence in situ hybridization protocol for Plasmodium falciparum greatly improves nuclear architecture conservation

Fluorescence in situ hybridization (FISH) has been used extensively in the study of nuclear organization and gene positioning in Plasmodium falciparum. While performing FISH with published protocols, we observed large variations in parasite nuclear morphology. We hypothesized that these inconsistencies might be due to the type of parasite preparation prior to FISH, which commonly involves air-drying, prompting us to develop a new fixation protocol. Here we show both qualitatively and quantitatively that compared to air-dried and briefly fixed parasites, longer fixation in suspension leads to improved conservation of nuclear structure and lower intra-population variation of nuclear shape as well as area after FISH development. While the fixation protocol per se does not cause detectable disruptions in nuclear morphology, it greatly influences the conservation of nuclear shape and size during the most stringent steps of FISH. The type of fixation used also influences the detection of telomeric clusters, and we show that the new fixation protocol permits improved conservation of the chromosome end cluster perinuclear distribution and higher colocalization indexes for two adjacent chromosome end probes, Rep20 and telomere. Overall, the results indicate that our alternative protocol dramatically improves conservation of the nuclear architecture compared to previously reported Plasmodium DNA-FISH protocols and highlights the necessity of carefully choosing the fixation protocol for FISH.

Protein 4.2 Binds to the Carboxyl-terminal EF-hands of Erythroid α-Spectrin in a Calcium- and Calmodulin-dependent Manner

Spectrin and protein 4.1 cross-link F-actin protofilaments into a network called the membrane skeleton. Actin and 4.1 bind to one end of beta-spectrin. The adjacent end of alpha-spectrin, called the EF-domain, is calmodulin-like, with calcium-dependent and calcium-independent EF-hands. It has no known function. However, the sph(1J)/sph(1J) mouse has very fragile red cells and lacks the last 13 amino acids in the EF-domain, suggesting the domain is critical for skeletal integrity. Using pulldown binding assays, we find the alpha-spectrin EF-domain either alone or incorporated into a mini-spectrin binds native and recombinant protein 4.2 at a previously identified region of 4.2 (G(3) peptide). Native 4.2 binds with an affinity comparable with other membrane skeletal interactions (K(d) = 0.30 microM). EF-domains bearing the sph(1J) mutation are inactive. Binding of protein 4.2 to band 3 (K(d) = 0.45 microM) does not interfere with the spectrin-4.2 interaction. Spectrin-4.2 binding is amplified by micromolar concentrations of Ca(2+) (but not Mg(2+)) by three to five times. Calmodulin also binds to the EF-domain (K(d) = 17 microM), and Ca(2+)-calmodulin blocks Ca(2+)-dependent binding of protein 4.2 but not Ca(2+)-independent binding. The data suggest that protein 4.2 is located near protein 4.1 at the spectrin-actin junctions. Because proteins 4.1 and 4.2 also bind to band 3, the erythrocyte anion channel, we suggest that one or both of these proteins cause a portion of band 3 to localize near the spectrin-actin junctions and provide another point of attachment between the membrane skeleton and the lipid bilayer.

Digital Design of the Ocean Casing Pipes Centering Equipment

An Ocean Casing Pipes Centering Equipment is designed and implemented. Utilizing the equipment, two casing pipes can be fastened together by means of welding. The equipment can automatically carry out clamping and centering two casing pipes, and then the butt welding is conducted at their adjacent ends. In the development of this equipment, some advanced means, such as digital modelling and FEA (Finite Element Analysis), are taken full advantage of. First, all the parts’ 3D models are built with Pro/Engineer. Then, those digital parts is assembled in Pro/E assembly environments. Meanwhile, assembly interference detection is executed. Furthermore, by means of universal finite-element software，the finite element model is constructed. The strength and stiffness of the structure is calculated and analyzed so that the faults of the equipment can be found out in design stage. Through repeating this designing and verifying course, the structure of the equipment can be improved.

A Comparative MRI Study of Upper and Lower Lumbar Motion Segments in Patients With Low Back Pain

The study is a prospective cross-sectional study of 514 patients with low back pain and sciatica. The aim of this study was to assess the relation of various risk factors on upper and lower lumbar levels. Various risk factors such as aging, job (physical habits), obesity, and cigarette smoking have been reported to accelerate lumbar degenerative process, possibly to a different extent in upper and lower lumbar spine. Lumbar spine motion segment degenerative process has been radiologically assessed by severity of nucleus pulposus (NP) dislodgement, annular tears, and Modic changes in adjacent end plates. Five hundred and fourteen patients with low back pain of at least 4 weeks duration, aged 18 to 70 years were prospectively enrolled. All underwent thorough neurological assessment and lumbar 1.5 T high-resolution magnetic resonance imaging, being evaluated by independent neurosurgeon and neuroradiologists. NP dislodgement and Modic changes as well as neurological findings were graded. Statistical analysis was performed by analysis of variance, t test, chi, and Fisher exact test. There were 244 men and 270 women. Sixty-six percent of lower lumbar levels showed NP dislodgement at least in 1 level. Aging had significant association with NP dislodgement, and patients with lower lumbar NP dislodgement had a mean age, 10 years younger than those with upper lumbar NP dislodgement. There was no significant association between sex, body mass index >25 kg/m, and vibratory job either in upper or lower lumbar levels and NP degeneration. Heavy lifting was associated with upper lumbar NP dislodgement while, sedentary and housework were associated with NP dislodgement only in lower lumbar levels. Also cigarette smoking (> or =10 pack/y) and older age (>50 y) were associated only with upper lumbar NP dislodgement. Modic changes correlated only with advanced age (>50 y), and there was no association with body mass index >25, smoking, job habits and sex. The study revealed that pathological alteration in vertebral end plates is the same in upper and lower lumbar bony tissues as detected by Modic's criteria, whereas those of intervertebral discs is different regarding spinal level and risk factor.

P75. Correction of Anterior Sagittal Imbalance by Posterior-Only Discectomy, Wedge Osteotomy of Adjacent Vertebral End Plates and Interbody Fusion. Technical Aspects, Clinical and Radiological Outcome

BACKGROUND CONTEXT: Different surgical techniques have been proposed for correction of anterior sagittal imbalance (SI) such as Smith-Petersen osteotomy, vertebral column resection and pedicle substration osteotomy. All they have a limited ability for correction and are related to frequent complications.

The influence of extended posterior instrumentatiоn on the vertebral growth after surgical correction of severe kyphosis in children

Objective. To study the effect of modern methods of spinal instrumentation for treatment of tuberculous spondylitis on growth of vertebrae after deformity correction in extensively growing children. Material and Methods. A total of 28 preschool age children were operated on for tuberculous spondylitis complicated by kyphosis exceeding 50°. Eight patients were operated on without posterior instrumentation, 20 patients - with additional posterior compressive implants. More than one year follow-up included assessment of the following metric parameters: anterior and posterior vertical size of fusion, anterior and posterior vertical size of the intact vertebra caudal to the anterior fusion inside and outside the instrumented zone. Results. Degenerative changes in the initially intact spinal motion segments within fixation zone were observed for 2 years after surgery in 17 out of 20 patients operated on with posterior instrumented fixation. These changes were presented by a sharp decrease in the intervertebral disc height and by a sclerosis of adjacent end plates. Conclusion. Children operated on with application of modern implants have not still reach the age of the growth stop, though follow-up periods are sufficiently long. This does not allow predicting the spine development in the adolescence.

Rif1 and Rif2 Inhibit Localization of Tel1 to DNA Ends

Chromosome ends, known as telomeres, have to be distinguished from DNA double-strand breaks (DSBs) that activate the DNA-damage checkpoint. In budding yeast, the ATM homolog Tel1 associates preferentially with short telomeres and promotes telomere addition. Here, we show that the telomeric proteins Rif1 and Rif2 attenuate Tel1 recruitment to DNA ends through distinct mechanisms. Both Rif1 and Rif2 inhibit the localization of Tel1, but not the Mre11-Rad50-Xrs2 (MRX) complex, to adjacent DNA ends. Rif1 function is weaker at short telomeric repeats compared with Rif2 function and is partly dependent on Rif2. Rif2 competes with Tel1 for binding to the C terminus of Xrs2. Once Tel1 is delocalized, MRX does not associate efficiently with Rap1-covered DNA ends. These results reveal a mechanism by which telomeric DNA sequences mask DNA ends from Tel1 recognition for the regulation of telomere length.

Numerical modelling of strain localisation and fluid flow during extensional fault reactivation: Implications for hydrocarbon preservation

A numerical modelling approach is used to investigate the main controls of strain localisation on faults and fluid flow in fault-bound reservoir rocks during extensional reactivation. A series of 3D coupled mechanical deformation and fluid flow models were performed to simulate the response of simple fault and reservoir-seal geometries to extensional reactivation. The model results demonstrate that initial fault length is a primary control on strain distribution between faults and on fluid transport from the reservoir through the top seal. During extensional reactivation, longer faults in the population tended to accommodate greater shear strain and accumulate greater throw than smaller faults. With greater length contrast, there is an increased throw contrast for the same amount of extension. This behaviour can be attributed to the mechanism of strain sharing among fault elements. Spacing between adjacent faults is a secondary factor affecting strain partitioning. For a given fault length contrast, increasing the spacing increases the freedom of adjacent faults to move and leads to a more even distribution of strain. Fault strike overlap styles also affect strain distribution along faults. This is mainly expressed as the reduction of throws in the overlapping fault segments and partially overlapped or adjacent fault ends. Our models further demonstrate that fault lengths are likely to control fluid flow during extensional reactivation. Large faults in the models are the main conduit for fluid transport, expressed as strong upward fluid flow along these faults from the sandstone reservoir horizon through the shale seal.

Prosthetic replacement of elbow in postburn bony ankylosis: long-term results

Fifteen patients with 17 post-burn bony ankylosed elbows (two bilateral) fixed at a mean of 72.5 degrees +/- 27.5 degrees flexion were treated with Baksi sloppy hinge elbow arthroplasty. All patients agreed to avoid strenuous use of their replaced elbows. There were four males and 11 females whose ages varied from 21 to 48 years (average 31.6 years). One of the five patients who had severe anterior skin contracture required release. One patient died during the early follow-up period. During the follow-up studies which ranged from 11 to 23 years (average 14.1), eleven patients (68.7%) regained painless stable motion with mean recovery of arc of flexion from 20 degrees +/-10 degrees to 107.5 degrees +/-17.5 degrees with mean range of flexion 90 degrees +/-20 degrees . Good forearm motion was retained in all cases. According to the assessment score (Morrey BF, The elbow and it's disorder, 2nd edn. W.B. Saunders, Philadelphia, 1993), nine (56.2%) patients were recorded as excellent, two (12.5%) as good, and five (31.5%) as poor who were considered as failures. The five failures required removal of the prosthesis but retained acceptable elbow function due to periprosthetic fibrosis connecting the adjacent bone ends.

Tuberculous Tenosynovitis of Flexor Digitorum Longus Tendon

Extrapulmonary tuberculous involvement of musculoskeletal system accounts for approximately 1% to 5% of cases. Tuberculous involvement of the feet tendon is even rarer. We are reporting an extremely rare case of tuberculous tenosynovitis of flexor digitorum longus tendon in a 68-year-old man. A 68-year-old farmer from India presented with a painless swelling over medial aspect of left ankle for 3 months. Examination of left ankle and foot revealed non-tender, fluctuant swelling, anteroinferior to medial malleolus. Plain radiographs of the ankle and foot revealed no abnormality. Laboratory findings, including erythrocyte sedimentation rate, were within normal limits. When excision was attempted, purulent material came out on incising the subcutaneous tissue. Gram staining, acid fast bacilli staining and pyogenic culture detected no organism. Histopathological examination of the granulation tissue showed non-specific inflammation. The wound healed well with secondary intention over a 15-day period. Two months postoperatively, swelling recurred at the same site. Magnetic resonance imaging showed small hypointense collection in the tendon sheath of left flexor digitorum longus behind the left ankle joint and adjacent lower end of tibia on the T2-weighted, STIR, and gradient (T2 with fat saturation) images, which appeared hypointense on T1-weighted images, suggestive of tenosynovitis. Tenosynovectomy was performed. Mycobacterium tuberculosis was isolated on culture. Histopathological examination, this time revealed epitheloid granuloma. Patient recovered uneventfully after 5-drug antituberculous regime.

Mutation of a single residue, β‐glutamate‐20, alters protein–lipid interactions of light harvesting complex II

It is well established that assembly of the peripheral antenna complex, LH2, is required for proper photosynthetic membrane biogenesis in the purple bacterium Rhodobacter sphaeroides. The underlying interactions are, as yet, not understood. Here we examined the relationship between the morphology of the photosynthetic membrane and the lipid–protein interactions at the LH2–lipid interface. The non-bilayer lipid, phosphatidylethanolamine, is shown to be highly enriched in the boundary lipid phase of LH2. Sequence alignments indicate a putative lipid binding site, which includes β-glutamate-20 and the adjacent carotenoid end group. Replacement of β-glutamate-20 with alanine results in significant reduction of phosphatidylethanolamine and concomitant raise in phosphatidylcholine in the boundary lipid phase of LH2 without altering the lipid composition of the bulk phase. The morphology of the LH2 housing membrane is, however, unaffected by the amino acid replacement. In contrast, simultaneous modification of glutamate-20 and exchange of the carotenoid sphaeroidenone with neurosporene results in significant enlargement of the vesicular membrane invaginations. These findings suggest that the LH2 complex, specifically β-glutamate-20 and the carotenoids' polar head group, contribute to the shaping of the photosynthetic membrane by specific interactions with surrounding lipid molecules.

Progressive non-infectious anterior vertebral fusion, split cord malformation and situs inversus visceralis

BackgroundProgressive non-infectious anterior vertebral fusion is a unique spinal disorder with distinctive radiological features. Early radiographic findings consist of narrowing of the anterior aspect of the intervertebral disk with adjacent end plate erosions. There is a specific pattern of progression. The management needs a multi-disciplinary approach with major input from the orthopaedic surgeon.Case reportWe report a 12-year-old-female with progressive anterior vertebral fusion. This occurred at three vertebral levels. In the cervical spine there was progressive fusion of the lateral masses of the Axis with C3. Secondly, at the cervico-thoracic level, a severe, progressive, anterior thoracic vertebral fusion (C7-T5) and (T6-T7) resulted in the development of a thick anterior bony ridge and massive sclerosis and thirdly; progressive anterior fusion at L5-S1. Whereas at the level of the upper lumbar spines (L1) a split cord malformation was encountered. Situs inversus visceralis was an additional malformation. The role of the CT scan in detecting the details of the vertebral malformations was important. To our knowledge, neither this malformation complex and nor the role of the CT scan in evaluating these patients, have previously been described.ConclusionThe constellations of the skeletal abnormalities in our patient do not resemble any previously reported conditions with progressive anterior vertebral fusion. We also emphasise the important role of computerized tomography in the investigation of these patients in order to improve our understanding of the underlying pathology, and to comprehend the various stages of the progressive fusion process. 3D-CT scan was performed to improve assessment of the spinal changes and to further evaluate the catastrophic complications if fracture of the ankylosed vertebrae does occur. We believe that prompt management cannot be accomplished, unless the nature of these bony malformations is clarified.

Measurement and analyses of the effects of adjacent end plate curvatures on vertebral stresses

Background Vertebral end plates of the lumbosacral spine have various degrees of concavity and convexity. It is believed that the shape of the end plates alters the distribution of loads transferred along the spine, between the vertebrae. Animal models have been regularly used in the design and development of vertebral disc implants and cages; to date, very little information is known about the animal vertebral end plate curvature. Purpose The purpose was to measure and analyze the end plate curvature in the cadaver human male-female, chimpanzee, and canine lumbar vertebral bones. Study design/setting Nondestructive and nontouching scanning method was designed to obtain curvature in anterior-posterior and medial-lateral directions in the cadaver bones. Statistical analysis was performed on the data collected, and this data was then used to create a biomechanical model to evaluate the load transmission. Method Measurements in anterior-posterior and medial-lateral directions were performed on human, canine, and chimpanzee cadaver lumbar bones to obtain accurate data for the end plate curvatures. Six sets of measurements (on human male-female L4 lower to S1 upper end plates) were performed. A parametric vertebral motion segment model (with and without posterior elements) that includes the experimental curvature information was developed. The characteristic kidney-shaped cross-sectional model was created using a parametric equation. This model was used to perform finite element analyses investigating the effects of the location of maximum curvature on the stress distributions. Results The measurements for different species showed that the canine and chimpanzees, the quadrupeds, have entirely different curvature of their upper end plates compared with those in humans, the bipeds. Also, the curvatures of the human S1 upper end plates are significantly different from the rest of the vertebrae. This is a very useful piece of information in the comparison of these species. The stress distribution varied as the location of the maximum curvature shifted from the center to a more posterior position. The stresses in the vertebral core were found to decrease, with the shell taking more loads. Conclusions This provides essential information for rehabilitation and surgical techniques, including designs for various interbody devices such as fusion cages, bone grafts, and disc prosthesis.

Surgery in Hemophilia. The General View: Patient Selection, Timing, and Preoperative Assessment

Although often overlooked, the life of the patient with severe hemophilia is characterized by both intermittent and chronic pain. Bleeds into joints and muscles cause extensive pressure on sensory nerves and, following recurrent bleeds, joint destruction, and synovial reaction is accompanied by constant pains that are frequently mistaken for further bleeding. The orthopedic surgeon may break the vicious cycle of chronic synovitis by excising inflamed and hypertrophic synovium or severely damaged cartilage and adjacent bone ends, and implanting an artificial joint. Numerous technical solutions are now available and orthopedic surgery is increasingly on offer to those hemophilia patients who, since childhood, have been victims of insufficiently treated bleeds because no or limited treatment was available, and because the concept of prophylaxis had not yet been developed. Nonetheless, orthopedic surgery in patients with hemophilia requires much more effort and planning than surgery in non-hemophilic patients. In this overview, we will address issues related to surgery in hemophilic patients, as well as some practical issues related to the timing of surgery, preoperative testing, perioperative hemostasis, and patient rehabilitation.

Transposition of reversed Ac element ends generates chromosome rearrangements in maize.

In classical "cut-and-paste" transposition, transposons are excised from donor sites and inserted at new locations. We have identified an alternative pathway in which transposition involves the 5' end of an intact Ac element and the 3' end of a nearby terminally deleted fAc (fractured Ac). The Ac and fAc elements are inserted at the maize p1 locus on chromosome 1s in the same orientation; the adjacent ends of the separate elements are thus in reversed orientation with respect to each other and are separated by a distance of approximately 13 kb. Transposition involving the two ends in reversed orientation generates inversions, deletions, and a novel type of local rearrangement. The rearrangement breakpoints are bounded by the characteristic footprint or target site duplications typical of Ac transposition reactions. These results demonstrate a new intramolecular transposition mechanism by which transposons can greatly impact genome evolution.