The crystal structure of bacteriophage λ RexA provides novel insights into the DNA binding properties of Rex-like phage exclusion proteins

RexA and RexB function as an exclusion system that prevents bacteriophage T4rII mutants from growing on Escherichia coli λ phage lysogens. Recent data established that RexA is a non-specific DNA binding protein that can act independently of RexB to bias the λ bistable switch toward the lytic state, preventing conversion back to lysogeny. The molecular interactions underlying these activities are unknown, owing in part to a dearth of structural information. Here, we present the 2.05-Å crystal structure of the λ RexA dimer, which reveals a two-domain architecture with unexpected structural homology to the recombination-associated protein RdgC. Modelling suggests that our structure adopts a closed conformation and would require significant domain rearrangements to facilitate DNA binding. Mutagenesis coupled with electromobility shift assays, limited proteolysis, and double electron-electron spin resonance spectroscopy support a DNA-dependent conformational change. In vivo phenotypes of RexA mutants suggest that DNA binding is not a strict requirement for phage exclusion but may directly contribute to modulation of the bistable switch. We further demonstrate that RexA homologs from other temperate phages also dimerize and bind DNA in vitro. Collectively, these findings advance our mechanistic understanding of Rex functions and provide new evolutionary insights into different aspects of phage biology.

Bacteriophage λ RexA and RexB Functions Assist the Transition from Lysogeny to Lytic Growth

The CI and Cro repressors of bacteriophage λ create a bistable switch between lysogenic and lytic growth. In λ lysogens, CI repressor expressed from the P_RM promoter blocks expression of the lytic promoters P_L and P_R to allow stable maintenance of the lysogenic state. When lysogens are induced, CI repressor is inactivated and Cro repressor is expressed from the lytic P_R promoter. Cro repressor blocks P_RM transcription and CI repressor synthesis to ensure that the lytic state proceeds. RexA and RexB proteins, like CI, are expressed from the P_RM promoter in λ lysogens; RexB is also expressed from a second promoter, P_LIT , embedded in rexA. Here we show that RexA binds CI repressor and assists the transition from lysogenic to lytic growth, using both intact lysogens and defective prophages with reporter genes under control of the lytic P_L and P_R promoters. Once lytic growth begins, if the bistable switch does return to the immune state, RexA expression lessens the probability that it will remain there, thus stabilizing the lytic state and activation of the lytic P_L  and P_R  promoters. RexB modulates the effect of RexA and may also help establish phage DNA replication as lytic growth ensues.

French recommendations for the management of patients with spinal cord injury or at risk of spinal cord injury

OBJECTIVES

To update the French guidelines on the management of trauma patients with spinal cord injury or suspected spinal cord injury.

DESIGN

A consensus committee of 27 experts was formed. A formal conflict-of-interest (COI) policy was developed at the outset of the process and enforced throughout. The entire guidelines process was conducted independently of any industrial funding (i.e. pharmaceutical, medical devices). The authors were advised to follow the rules of the Grading of Recommendations Assessment, Development and Evaluation (GRADE®) system to guide assessment of quality of evidence. The potential drawbacks of making strong recommendations in the presence of low-quality evidence were emphasised.

METHODS

The committee studied twelve questions: (1) What are the indications and arrangements for spinal immobilisation? (2) What are the arrangements for pre-hospital orotracheal intubation? (3) What are the objectives of haemodynamic resuscitation during the lesion assessment, and during the first few days in hospital? (4) What is the best way to manage these patients to improve their long-term prognosis? (5) What is the place of corticosteroid therapy in the initial phase? (6) What are the indications for magnetic resonance imaging in the lesion assessment phase? (7) What is the optimal time for surgical management? (8) What are the best arrangements for orotracheal intubation in the hospital environment? (9) What are the specific conditions for weaning these patients from mechanical ventilation for? (10) What are the procedures for analgesic treatment of these patients? (11) What are the specific arrangements for installing and mobilising these patients? (12) What is the place of early intermittent bladder sampling in these patients? Each question was formulated in a PICO (Patients, Intervention, Comparison, Outcome) format and the evidence profiles were produced. The literature review and recommendations were made according to the GRADE® Methodology.

RESULTS

The experts' work synthesis and the application of the GRADE method resulted in 19 recommendations. Among the recommendations formalised, 2 have a high level of evidence (GRADE 1+/-) and 12 have a low level of evidence (GRADE 2+/-). For 5 recommendations, the GRADE method could not be applied, resulting in expert advice. After two rounds of scoring and one amendment, strong agreement was reached on all the recommendations.

CONCLUSIONS

There was significant agreement among experts on strong recommendations to improve practices for the management of patients with spinal cord injury.

Correction to: Outcomes of surgical treatments of spinal metastases: a prospective study

The correct name of F. Saihlan should be F. Sailhan.

Elements in the λ immunity region regulate phage development: beyond the 'Genetic Switch'

Genetic elements in the bacteriophage λ immunity region contribute to stable maintenance and synchronous induction of the integrated Escherichia coli prophage. There is a bistable switch between lysogenic and lytic growth that is orchestrated by the CI and Cro repressors acting on the lytic (P_L and P_R ) and lysogenic (P_RM ) promoters, referred to as the Genetic Switch. Other less well-characterized elements in the phage immunity region include the P_LIT promoter and the immunity terminator, T_IMM . The P_LIT promoter is repressed by the bacterial LexA protein in λ lysogens. LexA repressor, like the λ CI repressor, is inactivated during the SOS response to DNA damage, and this regulation ensures that the P_LIT promoter and the lytic P_L and P_R promoters are synchronously activated. Proper RexA and RexB protein levels are critical for the switch from lysogeny to lytic growth. Mutation of P_LIT reduces RexB levels relative to RexA, compromising cellular energetics and causing a 10-fold reduction in lytic phage yield. The RexA and RexB proteins interact with themselves and each other in a bacterial two-hybrid system. We also find that the transcription terminator, T_IMM , is a Rho-independent, intrinsic terminator. Inactivation of T_IMM has minimal effect on λ lysogenization or prophage induction.

Outcomes of surgical treatments of spinal metastases: a prospective study

BACKGROUND

Owing to recent advances in cancer therapy, updated data are required for clinicians counselling patients on treatment of spinal metastases.

OBJECTIVE

To analyse the outcomes of surgical treatments of spinal metastases.

METHODS

Prospective and multicentric study that included consecutively patients operated on for spinal metastases between January 2016 and January 2017. Overall survival was calculated with the Kaplan-Meier method. Cox proportional hazard model was used to calculate hazard ratio (HR) analysing mortality risk according to preoperative Karnofsky performance status (KPS), mobility level and neurological status.

RESULTS

A total of 252 patients were included (145 males, 107 females) aged a mean 63.3 years. Median survival was 450 days. Primary cancer sites were lung (21%) and breast (19%). Multiple spinal metastases involved 122 patients (48%). Concomitant skeletal and visceral metastases were noted in 90 patients (36%). Main procedure was laminectomy and posterior fixation (57%). Overall, pain and mobility level were improved postoperatively. Most patients had normal preoperative motor function (50%) and remained so postoperatively. Patients "bedbound" on admission were the less likely to recover. In-hospital death rate was 2.4% (three disease progression, one septic shock, one pneumonia, one pulmonary embolism). Complication rate was 33%, deep wound infection was the most frequent aetiology. Higher mortality was observed in patients with poorest preoperative KPS (KPS 0-40%, HR = 3.1, p < 0.001) and mobility level ("bedbound", HR = 2.16, p < 0.001). Survival seemed also to be linked to preoperative neurological function.

CONCLUSION

Surgical treatments helped maintain reasonable condition for patients with spinal metastases. Intervention should be offered before patients' condition worsen to ensure better outcomes.

Thoracic disc herniation: Surgical treatment

Thoracic disc herniation is rare and mainly occurs between T8 and L1. The herniation is calcified in 40% of cases and is labeled as giant when it occupies more than 40% of the spinal canal. A surgical procedure is indicated when the patient has severe back pain, stubborn intercostal neuralgia or neurological deficits. Selection of the surgical approach is essential. Mid-line calcified hernias are approached from a transthoracic incision, while lateralized soft hernias can be approached from a posterolateral incision. The complication rate for transthoracic approaches is higher than that of posterolateral approaches; however, the former are performed in more complex herniation cases. The thoracoscopic approach is less invasive but has a lengthy learning curve. Retropleural mini-thoracotomy is a potential compromise solution. Fusion is recommended in cases of multilevel herniation, herniation in the context of Scheuermann's disease, when more than 50% bone is resected from the vertebral body, in patients with preoperative back pain or herniation at the thoracolumbar junction. Along with complications specific to the surgical approach, the surgical risks are neurological worsening, dural breach and subarachnoid-pleural fistulas. Giant calcified herniated discs are the largest contributor to myelopathy, intradural extension and postoperative complications. Some of the technical means that can be used to prevent complications are explored, along with how to address these complications.

Percutaneous posterior fixation for unstable pelvic ring fractures

Several posterior fixation techniques for unstable pelvic ring fractures have been described. Here, we present a minimally invasive, percutaneous technique to fix the two posterior iliac crests using spinal instrumentation. Between September 2008 and March 2012, 11 patients with a mean age of 36.4 years were operated because of a vertically unstable Tile C pelvic ring fracture. Posterior fixation was performed using two polyaxial screws in each iliac crest with two subfascial connector rods. At the final follow-up, all patients were evaluated clinically and radiologically. The mean surgery time was 45 minutes; there were no intraoperative complications. At a mean follow-up of four years, the functional Majeed score was excellent in eight patients and good in three patients. The radiological results were excellent in eight patients and good in three patients. Percutaneous posterior fixation of vertically unstable pelvic fractures leads to good functional and radiological outcomes.

TYPE OF STUDY

Technical note, retrospective.

LEVEL OF EVIDENCE

IV.

Developments in ambulatory surgery in orthopedics in France in 2016

Under the new categorization introduced by the Health Authorities, ambulatory surgery (AS) in France now accounts for 50% of procedures, taking all surgical specialties together. The replacement of full hospital admission by AS is now well established and recognized. Health-care centers have learned, in coordination with the medico-surgical and paramedical teams, how to set up AS units and the corresponding clinical pathways. There is no single model handed down from above. The authorities have encouraged these developments, partly by regulations but also by means of financial incentives. Patient eligibility and psychosocial criteria are crucial determining factors for the success of the AS strategy. The surgeons involved are strongly committed. Feedback from many orthopedic subspecialties (shoulder, foot, knee, spine, hand, large joints, emergency and pediatric surgery) testify to the rise of AS, which now accounts for 41% of all orthopedic procedures. Questions remain, however, concerning the role of the GP in the continuity of care, the role of innovation and teaching, the creation of new jobs, and the attractiveness of AS for surgeons. More than ever, it is the patient who is "ambulatory", within an organized structure in which surgical technique and pain management are well controlled. Not all patients can be eligible, but the AS concept is becoming standard, and overnight stay will become a matter for medical and surgical prescription.

Late local recurrence, at 19 and 17 years, of sacral chordoma treated by en bloc resection

Sacral chordoma (SC) is a malignant bone tumor with high risk of local recurrence (LR) even after en bloc resection, generally in the first 10 years after resection. We report two cases of late LR, at 17 and 19 years. Two male patients, aged 45 and 53 years, presented with large SC needing a combined approach for en bloc resection. Surgical margins were safe for the first patient and borderline for the second. The patients had yearly follow-up. The first patient developed LR on the posterior wall of the right acetabulum and the second developed LR in the right sciatic notch, at 17 and 19 years, respectively. These two cases of very late LR of SC advocate for yearly screening of patients even more than 20 years after resection.

LEVEL OF EVIDENCE

IV (case report).

Abstract 2219: Development of an assay to detect transcription misincorporation errors in Escherichia coli

In contrast to errors in DNA replication which can product heritable mutations, errors in transcription cause only transient alterations. The temporary nature of these transcription mistakes has made them difficult to detect and genetic screens to identify mutations that lower the fidelity of transcription have been problematic. We addressed this problem by developing methods to turn transient transcription errors into permanent genetic changes. The principle is based on suppression of a mutation in the active site of the cre recombinase. This assay is based on two parts: a source of Cre, which is actually the transcription misincorporation substrate, and a genetic reporter with a phenotypic change created by Cre-mediated recombination between lox sites. To develop a substrate for E. coli we chose the galactokinase gene (galK) as our reporter. From an alignment of the galK protein from E.coli, H. sapiens and L. lactis we identified sites that might be able to accept a 12aa insertion encoded by the LoxP sequence without disrupting its function. We selected four different sites that were away from the GalK active site and on the surface of the protein. We started our project using the strain MG1655, which is galK (+), able to grow in galactose as a carbon source and red on a MacConkey galactose plate (MAcGal). Using oligo recombineering, we first inserted a 7 base sequence, which caused a frame-shift mutation, the cells became galK (-) and, therefore white on MacGal. To put it back in frame, we next replaced the 7 bases with a 36 base loxP site, which, if it does not disrupt the function of galK will make the cells galK (+) again. To our surprise, the insertion of this LoxP site was completely successful, putting the gene back in frame and making the cells galK (+) and, therefore, red at each of the four sites we chose. A derivative of this reporter was made with the a portion of the galK gene inverted at one of the loxP sites. Active Cre recombinase can be detected by flipping the inversion to restore galK function. The active site mutant cre-Y324C exhibits a very low inversion rate. Mutations that reduce the accuracy of transcription, such as cells defective in greA, exhibit an elevated frequency of galK (+) inversions. This system will be used to identify additional mutations that reduce the fidelity of transcription in E. coli.

Citation Format: Jorge A. Irizarry-Caro, Mary Ernst, Carolyn Court, Alison Rattray, Mikhail Bubunenko, Ding Jin, Donald Court, Jeffrey Strathern. Development of an assay to detect transcription misincorporation errors in Escherichia coli. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2219. doi:10.1158/1538-7445.AM2015-2219

Unicondylar fractures of the distal femur

BACKGROUND

Unicondylar fractures of the distal femur are rare, complex, intra-articular fractures. The objective of this multicentre study was to assess the reduction and fixation of unicondylar fractures.

HYPOTHESIS

Anatomic reduction followed by strong fixation allows early rehabilitation therapy and provides good long-term outcomes.

MATERIAL AND METHODS

We studied 163 fractures included in two multicentre studies, of which one was retrospective (n=134) and the other prospective (n=29). Follow-up of at least 1 year was required for inclusion. The treatment was at the discretion of the surgeon. Outcome measures were the clinical results assessed using the International Knee Society (IKS) scores and presence after fracture healing of malunion with angulation, an articular surface step-off, and/or tibio-femoral malalignment.

RESULTS

Mean age of the study patients was 50.9 ± 24 years, and most patients were males with no previous history of knee disorders. The fracture was due to a high-energy trauma in 51% of cases; 17% of patients had compound fractures and 44% multiple fractures or injuries. The lateral and medial condyles were equally affected. The fracture line was sagittal in 82% of cases and coronal (Hoffa fracture) in 18% of cases. Non-operative treatment was used in 5% of cases and internal fixation in 95% of cases, with either direct screw or buttress-plate fixation for the sagittal fractures and either direct or indirect screw fixation for the coronal fractures. After treatment of the fracture, 15% of patients had articular malunion due to insufficient reduction, with either valgus-varus (10%) or flexion-recurvatum (5%) deformity; and 12% of patients had an articular step-off visible on the antero-posterior or lateral radiograph. Rehabilitation therapy was started immediately in 65% of patients. Time to full weight bearing was 90 days and time to fracture healing 120 days. Complications consisted of disassembly of the construct (2%), avascular necrosis of the condyle (2%), and arthrolysis (5%). The material was removed in 11% of patients. At last follow-up, the IKS knee score was 71 ± 20 and the IKS function score 64 ± 7; flexion range was 106 ± 28° (<90° in 27% of patients); and 12% of patients had knee osteoarthritis.

CONCLUSION

Anatomic reduction of unicondylar distal femoral fractures via an appropriate surgical approach, followed by stable internal fixation using either multiple large-diameter screws or a buttress-plate, allows immediate mobilisation, which in turn ensures good long-term outcomes.

LEVEL OF EVIDENCE

IV, cohort study.

Bacteriophage λ N protein inhibits transcription slippage by Escherichia coli RNA polymerase

Transcriptional slippage is a class of error in which ribonucleic acid (RNA) polymerase incorporates nucleotides out of register, with respect to the deoxyribonucleic acid (DNA) template. This phenomenon is involved in gene regulation mechanisms and in the development of diverse diseases. The bacteriophage λ N protein reduces transcriptional slippage within actively growing cells and in vitro. N appears to stabilize the RNA/DNA hybrid, particularly at the 5′ end, preventing loss of register between transcript and template. This report provides the first evidence of a protein that directly influences transcriptional slippage, and provides a clue about the molecular mechanism of transcription termination and N-mediated antitermination.

Isolation and characterization of RNA polymerase rpoB mutations that alter transcription slippage during elongation in Escherichia coli

Transcription fidelity is critical for maintaining the accurate flow of genetic information. The study of transcription fidelity has been limited because the intrinsic error rate of transcription is obscured by the higher error rate of translation, making identification of phenotypes associated with transcription infidelity challenging. Slippage of elongating RNA polymerase (RNAP) on homopolymeric A/T tracts in DNA represents a special type of transcription error leading to disruption of open reading frames in Escherichia coli mRNA. However, the regions in RNAP involved in elongation slippage and its molecular mechanism are unknown. We constructed an A/T tract that is out of frame relative to a downstream lacZ gene on the chromosome to examine transcriptional slippage during elongation. Further, we developed a genetic system that enabled us for the first time to isolate and characterize E. coli RNAP mutants with altered transcriptional slippage in vivo. We identified several amino acid residues in the β subunit of RNAP that affect slippage in vivo and in vitro. Interestingly, these highly clustered residues are located near the RNA strand of the RNA-DNA hybrid in the elongation complex. Our E. coli study complements an accompanying study of slippage by yeast RNAP II and provides the basis for future studies on the mechanism of transcription fidelity.

Percutaneous fixation of thoracolumbar fractures: current concepts

Numerous improvements in minimally invasive spine surgery (MISS) have been made during the last decade. MISS in thoracolumbar spine trauma management must achieve the same results as conventional treatment but with less morbidity. The increased use of MISS technologies in spine trauma has been correlated to the availability of more versatile instrumentation, which makes the fixation of all thoracic and lumbar levels possible. Balloon-assisted techniques have been used to support the anterior column in a stand-alone manner or in combination with open or percutaneous pedicle screw fixation. Fluoroscopy-assisted pedicle screw insertion is associated with less pedicle wall violation when compared to open surgery, but with increased radiation exposure for the surgeon and patient. Surgeons must be aware of this issue and new technologies are available to decrease irradiation. The advantages of percutaneous pedicle screw fixation relative to open surgery are discussed: preservation of posterior musculature, less blood loss, shorter operative time, lower infection risk, less postoperative pain, shorter rehabilitation time as well as shorter hospital stay. Limitations of percutaneous fixation include the inability to achieve direct spinal canal decompression and not having the option to perform a fusion. Nevertheless, these limitations can be addressed by combining MISS with open techniques. Indications for percutaneous spine fixation alone or in combination with MISS or open techniques are discussed based on the AO classification. The benefits of percutaneous spinal fixation for unstable spine fractures in polytrauma patients are also discussed. Posterior instrumentation can be easily removed after bone union to allow young patients to regain their mobility. Large well-controlled prospective studies are needed to draw up guidelines for less invasive procedures in spine trauma. In the future, development of new technologies can expand the scope of indications and treatment possibilities using MISS techniques in spine trauma.

Kyphoplasty versus vertebroplasty in osteoporotic thoracolumbar spine fractures. Short-term retrospective review of a multicentre cohort of 127 consecutive patients

BACKGROUND

Osteoporotic spine fractures induce a heavy burden in terms of both general health and healthcare costs. The objective of this multicentre study by the French Society for Spine Surgery (SFCR) was to compare outcomes after vertebroplasty and kyphoplasty in the treatment of osteoporotic thoracolumbar vertebral fractures.

HYPOTHESIS

We hypothesised that differences existed between vertebroplasty and kyphoplasty, notably regarding operative time and reduction efficacy, from which criteria for patient selection might be inferred.

MATERIAL AND METHODS

We conducted a retrospective multicentre review of 127 patients with Magerl Type A low-energy fractures after a fall from standing height between 2007 and 2010; 85 were managed with vertebroplasty and 42 with kyphoplasty. Age was not a selection criterion. We recorded pain intensity, time to management, operative time, kyphosis angle, wedge angle, cement leakage rate, and degree of cement filling.

RESULTS

Operative time was 43 minutes with kyphoplasty and 24 minutes with vertebroplasty (P=0.0002). Both techniques relieved pain, with no significant difference. Kyphoplasty significantly improved the wedge angle, by +6°, versus +2° with vertebroplasty (P=0.002). With kyphoplasty, the volume injected was larger and cement distribution was less favourable. Leakage rates were similar.

DISCUSSION

Despite the heterogeneity of our study, our data confirm the effectiveness of kyphoplasty in alleviating pain and decreasing deformities due to osteoporotic vertebral fractures. Vertebroplasty is a faster and less costly procedure that remains useful; no detectable clinical complications occur with vertebroplasty, which ensures better anchoring of the cement in the cancellous bone.

Minimally invasive management of thoraco-lumbar fractures: combined percutaneous fixation and balloon kyphoplasty

STUDY DESIGN

Retrospective review of prospectively collected data.

BACKGROUND

There is no consensus regarding the ideal treatment of thoraco-lumbar spine fractures without neurological compromise. Many surgical techniques have been described but none has proved its definite superiority. The main drawback of these procedures is directly related to the morbidity of the approach. As minimally invasive fixation combined with balloon kyphoplasty for treatment of thoraco-lumbar fractures is gaining popularity, its efficacy has yet to be established.

PURPOSE

The purpose of this study is to report operative data, clinical and radiological outcomes of patients undergoing minimally invasive management of thoraco-lumbar fracture at our institutions.

METHODS

Forty-one patients underwent percutaneous kyphoplasty and stabilization for treatment of single-level fracture of the thoracic or lumbar spine. All patients were neurologically intact. There were 20 males and 21 females with an average age of 50 years.

RESULTS

The mean follow-up was 15 months (3-90 months). The mean operative time was 102 minutes (range 35-240 minutes) and the mean blood loss was <100mL. VAS was significantly improved from 6.7 to 0.7 at last follow-up. Vertebral kyphosis decreased by 16° to 7.8° postoperatively (P<0.001). Local kyphosis and percentage of collapse were also significantly improved from 8° to 5.6° and from 35% to 16% at last follow-up. Fifteen leaks have been identified, three of which were posterior; all remained asymptomatic. No patient worsened his or her neurological condition postoperatively.

CONCLUSION

Percutaneous stabilization plus balloon kyphoplasty seems to be a safe and effective technique to manage thoraco-lumbar fractures without neurological impairment.

Probing cellular processes with oligo-mediated recombination and using the knowledge gained to optimize recombineering

Recombination with single-strand DNA oligonucleotides (oligos) in Escherichia coli is an efficient and rapid way to modify replicons in vivo. The generation of nucleotide alteration by oligo recombination provides novel assays for studying cellular processes. Single-strand exonucleases inhibit oligo recombination, and recombination is increased by mutating all four known exonucleases. Increasing oligo concentration or adding nonspecific carrier oligo titrates out the exonucleases. In a model for oligo recombination, λ Beta protein anneals the oligo to complementary single-strand DNA at the replication fork. Mismatches are created, and the methyl-directed mismatch repair (MMR) system acts to eliminate the mismatches inhibiting recombination. Three ways to evade MMR through oligo design include, in addition to the desired change (1) a C·C mismatch 6 bp from that change; (2) four or more adjacent mismatches; or (3) mismatches at four or more consecutive wobble positions. The latter proves useful for making high-frequency changes that alter only the target amino acid sequence and even allows modification of essential genes. Efficient uptake of DNA is important for oligo-mediated recombination. Uptake of oligos or plasmids is dependent on media and is 10,000-fold reduced for cells grown in minimal versus rich medium. Genomewide engineering technologies utilizing recombineering will benefit from both optimized recombination frequencies and a greater understanding of how biological processes such as DNA replication and cell division impact recombinants formed at multiple chromosomal loci. Recombination events at multiple loci in individual cells are described here.

An original knee arthrodesis technique combining external fixator with Steinman pins direct fixation

INTRODUCTION

Knee arthrodesis may be the last possible option for infected total knee arthroplasty (TKA) patients and in revision cases involving severe bone loss and/or extensor mechanism damages. Success in these situations depends on achieving good fixation assembly stability. We report bone fusion results using a fixation technique combining cross-pinning by two Steinman pins with a single-frame external fixator. Remission of infection at long-term follow-up was an additional criteria assessed for those cases initially treated for sepsis.

HYPOTHESIS

This fixation modality improves fusion rates.

PATIENTS AND METHODS

In six of this series of eight patients (mean age: 59 years), surgery was performed in a context of infection: five cases of infected TKA, and one case of septic arthritis. In the other two cases, arthrodesis was respectively indicated for a severe post-traumatic stiffness compounded by extensor system rupture and for a fracture combined to a complete mechanical implant loosening. In three of the six infection cases, arthrodesis was performed as a single-stage procedure. All patients were operated on using the same technique: primary arthrodesis site stabilization by frontal cross-pinning with two Steinman pins, followed by installation of a sagittal external fixator frame. Results were assessed at a mean 8 year follow-up.

RESULTS

All the arthrodeses showed fusion at a mean 3.5 months (range: 2.5 to 6 months) postoperative delay without reintervention. Weight-bearing was resumed at 2 to 3 months. The external fixator was removed at a mean 5.2 months. No recurrence of infection was observed over a mean follow-up of 8.2 years (range: 1 to 15 years). Three complications occurred: one hematoma, managed surgically; one supracondylar fracture treated orthopedically; and one osteitis, managed by surgical curettage.

DISCUSSION

This knee arthrodesis technique proved effective, with no failures in this short series, especially in cases of primary infection. It is a reproducible means of osteosynthesis, with little subsequent morbidity. Fixation in two orthogonal planes seemed to provide the stability required to achieve bone fusion. This assembly avoids internal fixation, which is never risk-free in a context of primary sepsis.

LEVEL OF EVIDENCE

Level IV. Retrospective study.

Surgical excision of bone sarcomas involving the sacroiliac joint

Adequate (wide or marginal and uncontaminated) margins and reconstruction are difficult to achieve when performing an internal hemipelvectomy for bone sarcomas involving the sacroiliac joint. We evaluated whether adequate surgical margins could be achieved and if functional outcomes could be predicted based on the type of resection and reconstruction. Forty patients had resections of the sacroiliac joint. Vertical sacral osteotomies were through the sacral wing (n = 2), ipsilateral sacral foramina (n = 27), sacral midline (n = 9), or contralateral foramina (n = 2). Iliac resections were Type I, Type I-II with partial or total acetabular re-section, or Type I-II-III. Surgical margins were adequate in 28 of 38 patients (74%), two (7%) of whom experienced local recurrence, compared with seven of 10 (70%) patients with inadequate margins. Reconstruction consisted of restoring continuity between the spine and pelvis. Resection of the entire acetabulum and removal of the lumbosacral trunk were the two main determinants of function, as assessed using the Musculoskeletal Tumor Society score. There were no life-threatening or function-threatening complications. Internal hemipelvectomy with a limb salvage procedure can be achieved with adequate surgical margins in selected patients. Functional outcomes can be predicted based on the type of resection and reconstruction, which helps the surgeon plan the procedure and inform the patient.

Multiple lumbar plexus neurotizations of the ninth, tenth, and eleventh intercostal nerves

The topographic anatomy of the lower intercostal nerves is less known than the upper ones except for the twelfth intercostal nerve. It is possible to use the lower intercostal nerves to carry out a neurotization of the lumbar roots. We studied the anatomy of the ninth, tenth, and eleventh intercostal nerves in order to specify the data of descriptive and topographic anatomy allowing to carry out their harvesting under good conditions. Ninth, tenth, and eleventh intercostal nerves of 50 cadavers were dissected. The proximal part of the nerve in the posterior intercostal space was exposed through a posterior approach. The lateral intercostal space was exposed through a lateral approach, under the latissimus dorsi, which made it possible to harvest the intercostals nerve. The proximal course of the nerve in posterior intercostals space was the same in all the cases. The nerve moves obliquely towards the outside to reach the lower border of the rib. The exit of posterior intercostal space is a fibrous strait that marks the entry of a channel between two muscular layers. We describe an aponevrotic channel in which the nerve and the vessels are, immediately at the lower border of the cranial rib. The mean total length of intercostal nerve harvested by our technique was 17.96 cm for the ninth intercostal nerve, 17.14 cm for the tenth intercostal nerve, and 15.94 cm for the eleventh intercostal nerve. The bifurcation of the intercostal nerve in a deep branch and the ramus cutaneus lateralis was found in the majority of the cases, from 9.5 to 21 cm of the emergence of the intercostal nerve in posterior intercostal space. This anatomical study of the ninth, tenth, and eleventh intercostal nerves in posterior intercostal space and lateral intercostal space appears to us to allow the realization of a reliable surgical harvesting.

Anatomical study of the paraspinal approach to the lumbar spine

The original description of the paraspinal posterior approach to the lumbar spine was for spinal fusion, especially regarding lumbosacral spondylolisthesis treatment. In spite of the technical details described by Wiltse, exact location of the area where the sacrospinalis muscle has to be split remains somewhat unclear. The goal of this study was to provide topographic landmarks to facilitate this surgical approach. Thirty cadavers were dissected in order to precisely describe the anatomy of the trans-muscular paraspinal approach. The level of the natural cleavage plane between the multifidus and the longissimus part of the sacrospinalis muscle was noted and measurements were done between this level and the midline at the level of the spinous process of L4. A natural cleavage plane between the multifidus and the longissimus part of the sacrospinalis muscle was present in all cases. There was a fibrous separation between the two muscular parts in 55 out of 60 cases. The mean distance between the level of the cleavage plane and the midline was 4 cm (2.4-5.5 cm). In all cases, small arteries and veins were present, precisely at the level of the cleavage plane. We found it possible to easily localize the anatomical cleavage plane between the multifidus part and the longissimus part of the sacrospinalis muscle. First the superficial muscular fascia is opened near the midline, exposing the posterior aspect of the sacrospinalis muscle. Then, the location of the muscular cleft can be found by identifying the perforating vessels leaving the anatomical inter-muscular space.

The thoracoabdominal intercostal nerves: an anatomical study for their use in neurotization

The topographic anatomy of the lower intercostal nerves is less known than that of the upper ones, except for the subcostal nerve (twelfth intercostal nerve). It is possible to use the lower intercostal nerves to neurotize the lumbar roots. We studied the anatomy of the ninth, tenth and eleventh intercostal nerves in order to specify the descriptive and topographical anatomical data that will allow their harvest in good condition. The ninth, tenth and eleventh intercostal nerves of 30 cadavers were dissected. The proximal part of the nerves in the posterior intercostal space was exposed through a posterior approach. The lateral intercostal space was exposed through a lateral approach, deep to the latissimus dorsi, that made it possible to harvest the intercostal nerve. The proximal course of the nerves in the posterior intercostal space was the same in all cases. The nerves move obliquely towards the outside to reach the lower border of the rib. The exit of the posterior intercostal space is a fibrous strait, which marks the entry of a channel between two muscular layers. We describe an aponeurotic channel in which the nerve and vessels run, immediately at the lower border of the cranial rib. The mean total length of intercostal nerve harvested by our technique was 17.86 cm for the ninth intercostal nerve, 16.95 cm for the tenth and 15.75 cm for the eleventh. Bifurcation of the intercostal nerve into a deep branch and the lateral cutaneous branch was found in the majority of the cases, 9.5-21 cm from the emergence of the intercostal nerve in the posterior intercostal space. This anatomical study of the ninth, tenth and eleventh intercostal nerves in the posterior intercostal and lateral intercostal spaces appears to us to allow reliable surgical harvesting.

[Contribution of systematic culture of drainage fluids in Altemeier class 1 and 2 procedures]

PURPOSE OF THE STUDY

We conducted a prospective study to determine the therapeutic impact of systematic culture of suction drainage collections in Altemeier class I and II procedures.

MATERIALS AND METHODS

We examined the following questions: how many microbiologically positive samples and infections of the operative site were present in the included patients? for positive cases, what was the antibiotic prescription (excluding antibiotic prophylaxy protocols planned before surgery for cleaning)? if the sample was positive in a patient with no clinical infection, what antibiotics were prescribed?

RESULTS

A total of 1039 samples were collected in 470 patients undergoing Altemeier class I and II procedures. One hundred five cultures were positive in 34 patients who had undergone major surgery. There were 11 postoperative infections during the study period. Mean delay to diagnosis of infection was 19.5 days. Only one infected patient with positive drainage samples developed an infection on the 7(th) day; the causal germ was different from that identified in the drainage collection. Only one of the patients with a positive drainage sample was given antibiotics, but this treatment was initiated at peroperative reception of the laboratory results.

DISCUSSION

Our findings demonstrate that systematic samples of drainage collections make no contribution to therapeutic decision making in patients undergoing class I and II surgery.

[Complex fractures of the proximal end of the radius and ulna in adults: a retrospective study of 38 cases]

PURPOSE OF THE STUDY

Complex lesions of the proximal end of the radius and ulna are uncommon and generally associate a fracture of the proximal ulna and a dislocation of the radial head, which also may be fractured. We assessed the effect of the type of fracture and treatment on functional outcome and complications.

MATERIAL AND METHODS

Thirty-eight adults (25 men and 13 women) were treated for complex fractures of the proximal end of the radius and ulna. For 25 of them, mean follow-up was 2.4 years. For the ulna, there was an epiphyseal fracture in 10 cases, a metaphyseal-epiphyseal fracture in 16 and a diaphyseal fracture in 12. The coronoid process was fractured in 20 cases and the proximal radius in 19. There was an anterior displacement in 24 cases. There were 9 open fractures and 13 patients had another injury of the upper limb. Functional outcome was assessed with a 100 point scale using subjective (pain) and objective (active motion, muscle force, stability) criteria.

RESULTS

For the 25 fractures with more than 1 year follow-up, outcome was very good in 8, good in 6, fair in 8 and poor in 3. The pain and muscle force scores followed a similar pattern. Motion appeared as the determining factor for good outcome. Seven early revisions (2 for deep infections, 2 for disassembly of the fixation system, 3 for insufficient fixation) were required among the 38 patients. Among the late complications, there were 3 nonunions, 5 misalignments, and 4 proximal radio-ulnar synostoses. Six elbows required revision to restore motion.

DISCUSSION

Certain characteristics of the fractures were predictive of poor outcome: skin opening, association with a lesion of the homolateral upper limb, mirror lesion of the lateral condyle, metaphyseal-epiphyseal fractures, communitive fractures, presence of a fracture of the radial head or the coronoid process.

CONCLUSION

Complex proximal fractures of both bones of the forearm threaten the functional prognosis of the upper limb due to the risk of stiffness. Successful treatment depends on three factors: stable anatomic reconstruction of the ulnar articulation, and reconstruction of the lateral column and the coronoid process, necessary for a stable elbow. In addition, early mobilization, possible with a stable osteosynthesis, is indispensable for recovering useful joint movement.

[Complex fractures of the proximal end of the radius and ulna in adults: a new classification]

Unlike injuries involving only one of the forearm bones, complex lesions of the proximal end of the radius and the ulna are particularly unstable. Various situations-Monteggia fracture, transolecraneal dislocation, or fracture-dislocation-are encountered. The classification systems proposed to date and recalled here are insufficient, making it difficult to provide optimal therapy and also hindering comparison between published series. We propose a descriptive classification including all the anatomic varieties of complex fractures of the proximal end of the radius and the ulna. This classification is based on our experience with 38 cases and takes into account 4 basic elements: the height of the ulnar fracture line, the direction of the displacement of the proximal radius, the association of a fracture of the proximal radius and/or of the coronoid process.

[Pelvic and spinal giant metastases from thyroid carcinomas: report of 8 cases]

PURPOSE OF THE STUDY

We report 8 cases of giant metastases in 7 patients with a pelvis or spinal localization in patients with differentiated carcinoma of the thyroid gland.

MATERIAL AND METHOD

Surgery was indicated for major functional disorders: pathological fracture, neurological complications. All patients were treated by embolization, tumor resection and reconstruction. All patients were given suppressive doses of thyroid hormones and 6 received complementary radiotherapy. Radioactive iodine, 100 mCu was also given in 5 cases. Outcome was analyzed retrospectively.

RESULTS

Two postoperative infections were successfully treated by surgical cleaning in one operation. There were no surgery-related neurological complications. One patient died in the immediate postoperative period due to the cancer. Mean follow-up in the other patients was 4 years. Functional outcome was excellent without local recurrence or mechanical complications.

DISCUSSION

These results suggest that surgical resection of giant bone metastases from thyroid carcinomas can provide favorable functional outcome similar to that achieved for small-sized metastases.

The effect of static in vivo bending on the murine intervertebral disc

BACKGROUND CONTEXT

Intervertebral disc cell function in vitro has been linked to features of the local environment that can be related to deformation of the extracellular matrix. Epidemiologic data suggest that certain regimens of spinal loading accelerate disc degeneration in vivo. Yet, the direct association between disc cell function, spinal loading and ultimately tissue degeneration is poorly characterized.

PURPOSE

To examine the relationships between tensile and compressive matrix strains, cell activity and annular degradation.

STUDY DESIGN/SETTING

An in vivo study of the biologic, morphologic and biomechanical consequences of static bending applied to the murine intervertebral disc. SUBJECT SAMPLE: Twenty-five skeletally mature Swiss Webster mice (12-week-old males) were used in this study.

OUTCOME MEASURES

Bending neutral zone, bending stiffness, yield point in bending, number of apoptotic cells, annular matrix organization, cell shape, aggrecan gene expression, and collagen II gene expression.

METHODS

Mouse tail discs were loaded for 1 week in vivo with an external device that applied bending stresses. Mid-sagittal sections of the discs were analyzed for cell death, collagen II and aggrecan gene expression, and tissue organization. Biomechanical testing was also performed to measure the bending stiffness and strength.

RESULTS

Forceful disc bending induced increased cell death, decreased aggrecan gene expression and decreased tissue organization preferentially on the concave side. By contrast, collagen II gene expression was symmetrically reduced. Asymmetric loading did not alter bending mechanical behavior of the discs.

CONCLUSIONS

In this model, annular cell death was related to excessive matrix compression (as opposed to tension). Collagen II gene expression was most negatively influenced by the static nature of the loading (immobilization), rather than the specific state of stress (tension or compression).

[Revision arthroplasty of the shoulder for painful glenoid loosening: a series of 14 cases with acromial prostheses reviewed at four year follow up]

PURPOSE OF THE STUDY

We present the results of a continuous series of 14 patients who underwent revision arthroplasty of the shoulder for painful major loosening of the glenoid component.

MATERIAL AND METHODS

Mean follow-up was four years after revision. Loosening was diagnosed seven and a half years after the primary arthroplasty. The diagnosis of loosening was based on the association of a painful impairment of the shoulder with increasing radiolucency or migration of the component. The degree of pain alone guided the surgical decision. The posterior approach provided wide exposure. A glenoid component with an acromial fixation was used in all cases.

RESULTS

The loosening was confirmed in all cases at surgery. Two were early failures of the fixation. The glenoid required a bone graft in all cases. The acromion was a useful landmark for proper positioning of the prosthesis. Fixation with cement and screws provided a strong fixation allowing immediate rehabilitation exercises. Good fixation of the glenoid component was achieved in all cases. After seven years follow-up there has been evidence of iterative loosening in one patient. In another case, one screw broke, suggesting forthcoming loosening. Twelve cases had no or very little pain. Two painful cases were associated with anterior migration of the humeral head.

DISCUSSION

Even when the local conditions are unfavorable, good implant fixation can be achieved by grafting the glenoid bone loss. Functional improvement is essentially due to pain relief.

CONCLUSION

This series, the largest published to date on revision surgery of painful loosening of total shoulder arthroplasty, demonstrated that iterative fixation is technically possible and can provide highly significant pain relief.

Loss of sagittal plane correction after removal of spinal implants

STUDY DESIGN

A retrospective review of a clinical series was performed.

OBJECTIVES

To evaluate the incidence of adult patients who experienced spinal collapse after spinal implant removal after a long spinal arthrodesis, and to assess the various factors that may influence the likelihood of collapse after implant removal.

SUMMARY OF BACKGROUND DATA

Published reports describing the benefits or complications of spinal implant removal do not exist. Spinal implant removal, often considered a benign procedure, is even required by the Food and Drug Administration (FDA) for certain implants.

METHODS

The medical records and radiographs of 116 consecutive adult patients with long posterior instrumented fusions (>5 segments) were reviewed. The information obtained included original diagnosis, patient age, number of previous surgeries before implant removal, levels of anterior and posterior fusion, time from fusion to implant removal, time from implant removal to failure, and reason for hardware removal. Radiographs also were assessed including scoliosis, lordosis, and kyphosis measurements before implant removal, after hardware removal, after failure, and after revision surgery.

RESULTS

Of 116 patients, 14 underwent spinal implant removal. Most of these patients reported prominent implants either proximally in the thoracic spine or distally in the ilium (Galveston technique). Of these 14 patients, 4 experienced increased pain and collapse after implant removal despite thorough intraoperative explorations demonstrating solid fusion.

CONCLUSIONS

Spinal implant removal after long posterior fusion in adults may lead to spinal collapse and further surgery. Removal of instrumentation should be avoided or should involve partial removal of the prominent implant.

[Surgical treatment of metastases from thyroid cancer in the axial skeleton. A retrospective study of 18 cases]

Between 1990 and 1997, 18 patients with a mean age of 55.5 years (11 females, 7 males) underwent surgical treatment for a metastasis from thyroid cancer involving the axial skeleton. At the time of surgery all patients had a poor prognosis: 7 metastases revealed the thyroid cancer, all 18 patients had a neurological or mechanical complication, 9 had multiple metastases, all were over 40 years of age. After arteriography with embolization, the surgical procedure consisted of curettage of the tumor and reconstruction, followed by treatment with iodine 131. The survival rate 3 years after surgery was 50%. At the last review, the functional outcome was good and 17 patients had total neurological recovery. Four complications occurred: 1 operative hemorrhage, 3 postoperative infections. Four patients had local recurrence of the metastasis with a one-year survival rate of 20%. When the thyroid cancer was revealed by the axial metastasis, the 3-year-survival rate was 42%. In cases with huge metastases, the 3-year-survival rate was 71%. It appears from these data that surgical treatment of metastases from thyroid cancer in the axial skeleton still achieves a good functional outcome even in cases where neurological or mechanical complications had occurred before surgery.

[Technical aspects of arthroscopic arthrolysis after total knee replacement]

Arthroscopic arthrolysis is a reliable technique for the treatment of knee stiffness due to arthrofibrosis following ligament replacement or following the treatment of knee fracture. However, its use is uncommon for this indication in total knee arthroplasty (TKA). In this study, we questioned whether or not arthroscopy is a reliable technique for treatment of knee stiffness following TKA, due to arthrofibrosis.

MATERIALS AND METHODS

Four men mean aged 54 (38-70) underwent knee arthroscopy for a history of arthrofibrosis following TKA. In two cases the arthrofibrosis had appeared after a primary TKA done for limited range of motion and in two other cases had followed a revision arthroplasty. The mean knee flexion before the TKA was 80 degrees (40-110) and it was 105 degrees (100-120) after performing the TKA. The knees were not mobilized under anesthesia though the mean flexion was 75 degrees (60-80) 15 days after the TKA. The indication for arthroscopy was a painless limited range of motion of the knee. The arthroscopy was performed 6 months (2.5-12) after the TKA and at this time the flexion was limited to 65 degrees (60-80). The extension was limited in 2 cases to 10 degrees and 30 degrees. Patients were evaluated an average of 20 months (8-36) after the arthroscopy. With 2 peripatellar portals we sectioned the adhesions in the suprapatellar pouch, the 2 retinaculars and the adhesive bands in the 2 gutters. Two anterior additional portals were used in case of extension lag. A suction drain was placed and the portals were sutured. A continuous passive motion machine was started in the recovery room.

RESULTS

The mean operating time for arthroscopic arthrolysis was 38 minutes (30-60). The mean knee flexion was 116 degrees (100-130) at the end of arthroscopy and was 93 degrees (75-110) at the last review. The mean flexion improved by 31 degrees (15-50). The mean flexion improved by 45% (25-83). The 2 extension lags decreased respectively from 30 degrees to 10 degrees and from 10 degrees to 0 degree. For these 2 patients the increase in range of motion was 70 degrees and 40 degrees respectively. The average amount of bleeding was 200 ml (86-520). There were no complications.

DISCUSSION

Few surgeons are experienced in arthroscopy for knee stiffness after TKA. Our results are similar to those reported by most authors. Regarding the technique, the section of the two retinaculars is necessary for the mobility of the patellar and most of the mobility is gained after the release of the gutters. The use of only two portals avoids damaging the TKA component and decreases the theoretical risk of infection. The major loss of motion after arthrolysis occurred during the first days following the arthroscopy. This is why we recommend using a regional anesthesia for the arthroscopy and during the following days to allow intensive mobilization of the knee. The arthrolysis should be done from 3 to 6 months after the TKA for better results.

CONCLUSION

Arthroscopy for the treatment of knee stiffness, due to arthrofibrosis, following TKA is a useful, reliable and safe technique.

[Knee fractures in the adult]

In the adult, fractures of the knee are joint fractures. The knee is a weight-bearing joint, and its mobility and stability must be recovered quickly for good functional recuperation. Aside from X-ray investigations, the initial examinations seek vascular, nerve and cutaneous lesions. The existence of a bruise or a cutaneous break decides the therapeutic choice and timing. Fractures of the lower extremity of the femur (sub-, inter-, supra- or unicondyle) most often require open surgery for better restitution of the joint surfaces; for fractures of the tibial plate, whether uni-, spino- or bituberous, a graft must be associated in case of crushing fracture. Fractures of the patella require surgery in case of rupture of the extensor.

Cytokine release from marrow mononuclear cells is negatively correlated to cortical elasticity in non-osteoporotic postmenopausal women

Activation of bone remodeling is likely to be under the control of mechanical factors acting, in part, through soluble local factors. We therefore investigated a relationship between cytokine production by marrow cells and bone elasticity. We studied 36 non-osteoporotic postmenopausal women undergoing hip arthroplasty for hip arthrosis (mean age: 68 +/- 8 years; lumbar BMD Z-score: +0.54 +/- 0.33 SD). Adherent marrow mononuclear cells were cultured for 48 hours with autologous plasma, and supernatants were harvested for PGE2, IL-1, TNF-alpha, and IL-6 measurements. Femoral neck cortical bones were removed during surgery for cortical histomorphometric evaluation and determination of elasticity indices (C33) using ultrasonic transmission method. In this nonosteoporotic population, femoral neck longitudinal elasticity indices were inversely correlated to both cortical thickness (r = -0.58, P < 0.01) and cortical porosity (r = -0.33, P < 0.01). The longitudinal elasticity indices were also negatively correlated to basal IL-1 and TNF-alpha release by adherent mononuclear marrow cells (r = -0.59, P < 0.01; r = -0.60, P < 0.01, respectively). However, no relationship was found between the three cytokines tested and either cortical thickness or porosity. These data show a link between cortical biomechanical properties and local factors involved in bone remodeling. We suggest that increased bone elasticity decreases transmission of strain, which in turn decreases cytokine release from marrow cells. However, whether cytokines influence bone elasticity or vice versa remains to be demonstrated.

Radiological study of severe proximal femoral focal deficiency

Twenty-two hips in 20 children, all classified as Amstutz type 3 proximal femoral focal deficiency, were studied by means of plain radiographs, arthrograms (30), ultrasound examination (six), computed tomography (CT) scans (including five arthrographies with CT) and magnetic resonance imaging (MRI; nine). These investigations demonstrated that in 15 hips, the superior femoral epiphysis was mobile in the acetabulum, whereas in six others, it was fixed and fused to the acetabulum. In one case, it was impossible to prove whether the epiphysis was mobile or fixed. The key radiologic and other image features that allow these conclusions to be drawn are described. The therapeutic implications are important, as it would be pointless or harmful to attempt to consolidate the femoral neck or put it into valgus when the epiphysis is spontaneously fixed to the acetabulum.

Britain's over-60s are still getting around

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