Questions about Using the Induced Membrane Technique to Manage Cases of Congenital Tibial Pseudarthrosis.

The induced membrane technique is an innovative approach for repairing critical bone defects and has been applied recently in patients with congenital pseudarthrosis of the tibia (CPT). CPT is frequently associated with neurofibromatosis type 1 (NF1). Here, we briefly describe the clinical results of the induced membrane technique in NF1-deficient patients with CPT and in an animal model of CPT. Furthermore, we discuss the hypotheses used to explain inconsistent outcomes for the induced membrane technique in CPT-especially when associated with NF1.

MQM1, a bacteriophage infecting strains of Aeromonas salmonicida subspecies salmonicida carrying Prophage 3.

Aeromonas salmonicida subsp. salmonicida is a Gam-negative bacterium responsible for furunculosis in fish. Because this aquatic bacterial pathogen has a rich reservoir of antibiotic-resistant genes, it is essential to investigate antibacterial alternatives, including the use of phages. Yet, we have previously demonstrated the inefficiency of a phage cocktail designed against A. salmonicida subsp. salmonicida strains due to a phage resistance phenotype associated to a prophage, namely Prophage 3. To bypass this resistance, one of the solutions is to isolate novel phages capable of infecting Prophage 3-bearing strains. Here we report on the isolation and characterization of the new virulent phage vB_AsaP_MQM1 (or MQM1), which is highly specific to A. salmonicida subsp. salmonicida strains. Phage MQM1 inhibited the growth of 01-B516, a strain carrying Prophage 3, including when combined to the previous phage cocktail. MQM1 infected 26 out of the 30 (87%) Prophage 3-bearing strains tested. Its linear dsDNA genome contains 63,343 bp, with a GC content of 50.2%. MQM1 genome can encode 88 proteins and 8 tRNAs, while no integrase or transposase-encoding genes were found. This podophage has an icosahedral capsid and a non-contractile short tail. We suggest that MQM1 may be a good addition to future phage cocktails against furunculosis to resolve the Prophage 3-resistance issue.

Anatomical variations in the sensory innervation of the dorsal surface of the first digit space, a cadaveric study with clinical consequences.

INTRODUCTION: Radial nerve palsy is a classical complication of a humeral shaft fracture. In clinical practice, motor palsy of the radial nerve is sometimes observed without an abnormality felt in the sensory territory. HYPOTHESIS: We hypothesised that this dissociation between sensory and motor involvement is related to anatomical variations of the sensory innervation of the dorsal surface of the first digit space, thus, we decided to study the nature and frequency of these variations. MATERIAL AND METHOD: A cadaveric study was conducted on 24 upper limbs to analyse the truncal origin of the sensory branches innervating the dorsal surface of the first digit space. RESULTS: The sensory branch of the radial nerve (SBRN) participated in the innervation of the dorsal surface of the first digit space in 22 limbs, an anatomical variation was present in 2 cases with a mixed innervation by the SBRN and the lateral cutaneous nerve of forearm (LCNF) in 1 case and singular innervation by LCNF, with no SBRN involvement, in 1 case. Communications between SBRN and LCNF were found in 7 cases. DISCUSSION: Pure motor radial damage, without a sensory deficit of the dorsal surface of the first digit space, does not preclude a complete traumatic injury of the radial nerve. The sensory innervation of this region can be relayed by a branch of the LCNF. LEVEL OF EVIDENCE: IV; cadaveric study.

Learning curve and influencing factors of performing microsurgical anastomosis: a laboratory prospective study.

Despite being a critical component of any cerebrovascular procedure, acquiring skills in microsurgical anastomosis is challenging for trainees. In this context, simulation models, especially laboratory training, enable trainees to master microsurgical techniques before performing real surgeries. The objective of this study was to identify the factors influencing the learning curve of microsurgical training. A prospective observational study was conducted during a 7-month diploma in microsurgical techniques carried out in the anatomy laboratory of the school of surgery. Training focused on end-to-end (ETE) and end-to-side (ETS) anastomoses performed on the abdominal aorta, vena cava, internal carotid and jugular vein, femoral artery and vein, caudal artery, etc. of Wistar strain rats under supervision of 2 expert anatomical trainers. Objective and subjective data were collected after each training session. The 44 microsurgical trainees enrolled in the course performed 1792 anastomoses (1577 ETE, 88%, vs. 215 ETS, 12%). The patency rate of 41% was independent from the trainees' surgical background and previous experience. The dissection and the temporary clamping time both significantly decreased over the months (p < 0.001). Technical mistakes were independently associated with thrombosis of the anastomoses, as assessed by the technical mistakes score (p < 0.01). The training duration (in weeks) at time of each anastomosis was the only significant predictor of permeability (p < 0.001). Training duration and technical mistakes constituted the two major factors driving the learning curve. Future studies should try and investigate other factors (such as access to wet laboratory, dedicated fellowships, mentoring during early years as junior consultant/attending) influencing the retention of surgical skills for our difficult and challenging discipline.

Corrigendum: Safety of Bottle-Feeding Under Nasal Respiratory Support in Preterm Lambs With and Without Tachypnoea.

[This corrects the article DOI: 10.3389/fphys.2021.785086.].

Conventional vs high-frequency ventilation for weaning from total liquid ventilation in lambs.

OBJECTIVE: To compare conventional gas ventilation (GV) and high-frequency oscillatory ventilation (HFOV) for weaning from total liquid ventilation (TLV). METHODS: Sixteen lambs were anesthetized. After 1 h of TLV with perflubron (PFOB), they were assigned to either GV or HFOV for 2 h. Oxygen requirements, electrical impedance tomography and videofluoroscopic sequences, and respiratory system compliance were recorded. RESULTS: The lambs under GV needed less oxygen at 20 min following TLV (40 [25, 45] and 83 [63, 98]%, p = 0.001 under GV and HFOV, respectively). During weaning, tidal volume distribution was increased in the nondependent regions in the GV group compared to baseline (p = 0.046). Furthermore, residual PFOB was observed in the most dependent region. No air was detected by fluoroscopy in that region at the end of expiration in the GV group. CONCLUSION: GV offers a transient advantage over HFOV with regards to oxygenation for TLV weaning.

Induced membrane technique applied to the forearm: Technical refinement, indications and results of 13 cases.

INTRODUCTION: The unique anatomical characteristics of the forearm bones makes their reconstruction challenging. The aim of this study was to report the surgical methods and results of the induced membrane technique applied to traumatic forearm bone defects. MATERIAL AND METHODS: We evaluated retrospectively a case series of 13 patients operated between 2010 and 2017. The first surgical step consisted of debridement of the fracture site and implantation of a cement spacer with appropriate fixation. The anatomy of the forearm skeleton had to be restored. The second step, done 6 weeks later, consisted of removing the cement spacer and applying cancellous bone autograft harvested from the iliac crest. The outcome measures were radiological bone union, need for surgical revision, and postoperative wrist range of motion. RESULTS: All 13 patients were men, with a mean age of 39 years (18-67). The average follow-up was 2.5 years. Eleven patients were suffering from a nonunion and two from a post-traumatic bone defect. Six patients had an identified preoperative infection. Three patients had previously undergone an unsuccessful treatment for their nonunion with bone addition. The maximum length of bone reconstruction was 12 cm. Union was achieved in 12 of 13 patients in a mean of 5 months (3-8). The other patient died during the postoperative course. Two patients needed revision surgery: ulnar shortening osteotomy (1 case) and additional tendon reconstruction (1 case). The mean pronosupination range was 123° on average (55-180°). The mean flexion-extension range was 106° (90-130°). CONCLUSION: The induced membrane technique is a reliable reconstruction technique that is well suited to reconstruction of the forearm skeleton. LEVEL OF EVIDENCE: IV, retrospective study.

Paclitaxel and mortality in patients with claudication and de novo femoropopliteal lesions: a historical cohort study.

OBJECTIVE: To compare the mortality rates of patients with claudication and de novo femoropopliteal lesions treated with and without paclitaxel coated devices (PCD). BACKGROUND: A recent meta-analysis, mostly including patients with claudication and de novo femoropopliteal lesions but also with recurrent stenoses and critical limb ischemia, has shown a significant excess mortality in patients treated with PCD. METHODS: Comparison of two historical cohorts of patients presenting with claudication and de novo femoropopliteal lesions treated with and without PCD between 2008 and 2018. RESULTS: After review of 5219 arteriograms in patients presenting with peripheral artery disease, 700 consecutive patients were included consisting in 72.6% of male (n = 508). Mean age was 68.1 ± 8.5 years. 45.7% of the patients (n = 320) had a treatment including a PCD. Mean femoropopliteal lesion length was 123 ± 91 mm including 44.6% of occlusions. Patients of the control group were censored at crossover to paclitaxel when applicable. Mortality rates at 1, 2 and 5 years were 4.6%, 7.5%, 19.4% and 1.6%, 6.2%, 16.6% in the non-PCD and PCD groups respectively. The relative risks of death when using PCD were 0.35 (p = 0.03), 0.83 (p = NS) and 0.86 (p = NS) at 1, 2 and 5 years respectively. CONCLUSION: There was no excess mortality in patients with claudication and de novo femoropopliteal lesions treated with paclitaxel coated devices at 1, 2 and 5 years of follow-up in this cohort. The current study suggests that additional prospective randomized studies properly powered to study mortality are necessary.

Modified Masquelet Technique Using Allogeneic Graft for a Gustilo-Anderson Type III-A Open Fracture of the Femur with an 8 cm Bone Defect.

The induced membrane technique was initially described by Masquelet et al. in 1986 as a treatment for tibia nonunion; then, it became one of the established methods in the management of bone defects. Several changes have been made to this technique and have been used in different contexts and different methodologies. We present the case of a 16-year-old girl admitted to our department for a polytrauma after a motorcycle accident. She presented a Gustilo III-A open fracture of the right femoral shaft with a large bone defect of 8 centimeters that we treated with a modified Masquelet technique. In the first stage, an Open Reduction and Internal Fixation of the fracture was made using a 4,5 mm Dynamic Compression Plate and a PMMA cement was inserted at the bone defect area. The second stage was done after 11 weeks, and the defect area was filled exclusively with bone allograft from a bone bank. Complete bony union was seen at 60 weeks of follow-up. After the removal of the implants by another surgeon, the patient presented an atraumatic fracture of the neoformed bone that we treated with intramedullary femoral nailing associated with a local autograft using reaming debris. A complete bony union was achieved after 12 weeks with a complete range of motion of the hip and knee. The stability given to the fracture is essential because it influences the quality of the induced membrane and Masquelet has recommended high initial fixation rigidity to promote incorporation of the graft. It is recommended to delay the second stage of this technique after 8 weeks, especially in femoral reconstruction, to optimize the quality of the induced membrane. Several studies used a modified induced membrane technique to recreate a traumatic large bone defect, and all of them used an autologous bone graft alone or an enriched bone graft. In this case, the use of allograft exclusively seems to be as successful as an autologous or enriched bone graft. Now, with the advent of bone banks, it is possible to get an unlimited amount of allograft, so additional research and large studies are necessary before giving recommendations.

Nasal respiratory support and tachypnea and oral feeding in full-term newborn lambs.

Newborn infants with respiratory difficulties frequently require nasal respiratory support such as nasal continuous positive airway pressure (nCPAP) or high-flow nasal cannulae (HFNC). Oral feeding of these infants under nasal respiratory support remains controversial out of fear of aspiration and cardiorespiratory events. The main objective of this study was to evaluate the safety of oral feeding under different types of nasal respiratory support in newborn lambs without or with tachypnea. Eight lambs aged 4-5 days were instrumented to record sucking, swallowing, respiration, ECG, oxygen saturation, and arterial blood gases. Each lamb was given two bottles of 30 mL of milk with a pause of 30 s under videofluoroscopy in four conditions [no respiratory support, nCPAP 6 cmH2O, HFNC 7 L/min, HFNCCPAP (= HFNC 7 L/min + CPAP 6 cmH2O)] administered in random order. The study was conducted in random order over 2 days, with or without standardized tachypnea induced by thoracic compression with a blood pressure cuff. Generalized linear mixed models were used to compare the four nasal respiratory supports in terms of safety (cardiorespiratory events and aspiration), sucking-swallowing-breathing coordination, and efficacy of oral feeding. Results reveal that no nasal respiratory support impaired the safety of oral feeding. Most of the few laryngeal penetrations we observed occurred with HFNCCPAP. Nasal CPAP modified sucking-swallowing-breathing coordination, whereas the efficiency of oral feeding decreased under HFNCCPAP. Results were similar with or without tachypnea. In conclusion, oral feeding under nasal respiratory support is generally safe in a term lamb, even with tachypnea.NEW & NOTEWORTHY The practice of orally feeding newborns suffering from respiratory problems while on nCPAP or HFNC remains controversial for fear of triggering cardiorespiratory events or aspiration pneumonia, or aggravating chronic lung disease. The present results show that bottle-feeding is generally safe in full-term lambs under nasal respiratory support, both without and with tachypnea.

Safety of Bottle-Feeding Under Nasal Respiratory Support in Preterm Lambs With and Without Tachypnoea.

Aim: Convalescing preterm infants often require non-invasive respiratory support, such as nasal continuous positive airway pressure or high-flow nasal cannulas. One challenging milestone for preterm infants is achieving full oral feeding. Some teams fear nasal respiratory support might disrupt sucking-swallowing-breathing coordination and induce severe cardiorespiratory events. The main objective of this study was to assess the safety of oral feeding of preterm lambs on nasal respiratory support, with or without tachypnoea. Methods: Sucking, swallowing and breathing functions, as well as electrocardiogram, oxygen haemoglobin saturation, arterial blood gases and videofluoroscopic swallowing study were recorded in 15 preterm lambs during bottle-feeding. Four randomly ordered conditions were studied: control, nasal continuous positive airway pressure (6 cmH2O), high-flow nasal cannulas (7 L•min-1), and high-flow nasal cannulas at 7 L•min-1 at a tracheal pressure of 6 cmH2O. The recordings were repeated on days 7-8 and 13-14 to assess the effect of maturation. Results: None of the respiratory support impaired the safety or efficiency of oral feeding, even with tachypnoea. No respiratory support systematically impacted sucking-swallowing-breathing coordination, with or without tachypnoea. No effect of maturation was found. Conclusion: This translational physiology study, uniquely conducted in a relevant animal model of preterm infant with respiratory impairment, shows that nasal respiratory support does not impact the safety or efficiency of bottle-feeding or sucking-swallowing-breathing coordination. These results suggest that clinical studies on bottle-feeding in preterm infants under nasal continuous positive airway pressure and/or high-flow nasal cannulas can be safely undertaken.

Induced membrane technique: a critical literature analysis and proposal for a failure classification scheme.

The reconstruction of long-bone segmental defects remains challenging, with the three common methods of treatment being bone transport, vascularized bone transfer, and the induced membrane technique (IMT). Because of its simplicity, replicability, and reliability, usage of IMT has spread all over the world in the last decade, with more than 300 papers published in the PubMed literature database on this subject so far. Most of the clinical studies have reported high rates of bone union, yet some also include more controversial results with frequent complications and revision surgeries. At the same time, various experimental research efforts have been designed to understand and improve the biological properties of the induced membrane. This literature review aims to provide an overview of IMT clinical results in terms of bone union and complications and to compare them with those of other reconstructive procedures. In light of our findings, we then propose an original classification scheme of IMT failures distinguishing between preventable and nonpreventable failures.

Repeated Induced-Membrane Technique Failure without Infection: A Series of Three Consecutive Procedures Performed for a Single Femur Defect.

A 40-year-old male was treated using the induced-membrane technique (IMT) for a noninfected, 9 cm long femoral bone defect complicating a lengthening procedure. The interesting case feature lies in the three consecutive IMT procedures that were necessary to achieve complete bone repair in this unusual clinical situation. The first procedure failed because of the lack of graft revascularization likely related to an induced-membrane (IM) alteration demonstrated by histological observations. The second IMT procedure led to partial graft integration interrupted by the elongation nail breakage. At last, the third procedure fully succeeded after nail exchange and iterative iliac bone grafting. Complete bone union was achieved with a poor functional recovery one year after the last procedure and four years following the first cement spacer implantation. By means of clinical and histological observations, we demonstrated that the first and the second IMT failures had two distinct origins, namely, biological and mechanical causes, respectively. Although simple, a successful IMT procedure is not so easy to complete.

Induced membrane technique with sequential internal fixation: use of a reinforced spacer for reconstruction of infected bone defects.

PURPOSE: To evaluate a novel sequential internal fixation strategy using a reinforced spacer for infected bone defect reconstruction by the induced membrane technique (IMT). METHODS: A retrospective case study was performed among patients treated for infected bone defects by applying this strategy. Following radical debridement, temporary stabilization was provided by a massive cement spacer combined with minimal intramedullary fixation during step 1. Definitive internal fixation was performed together with bone grafting at step 2. RESULTS: Eight patients with a mean age of 58 years were reviewed. The mean bone defect length was 8.8 cm. The spacer armature mostly consisted of elastic nails and Steinmann pins. Iterative debridement was required in one case after step 1. The mean interval between steps was 12 weeks. Definitive internal fixation was performed by intramedullary nailing (n = 4) or plating (n = 4). At a mean follow-up of 21 months, bone union was achieved in seven cases without additional bone grafting or infection recurrence. CONCLUSIONS: Sequential internal fixation using a reinforced cement spacer seems to be a valuable option for avoiding external fixation between IMT steps and limiting the recurrence of infection.

The Masquelet technique: Current concepts, animal models, and perspectives.

Bone reconstruction within a critical-sized defect remains a real challenge in orthopedic surgery. The Masquelet technique is an innovative, two-step therapeutic approach for bone reconstruction in which the placement of a poly (methylmethacrylate) spacer into the bone defect induces the neo-formation of a tissue called "induced membrane." This surgical technique has many advantages and is often preferred to a vascularized bone flap or Ilizarov's technique. Although the Masquelet technique has achieved high clinical success rates since its development by Alain-Charles Masquelet in the early 2000s, very little is known about how the process works, and few animal models of membrane induction have been developed. Our successful use of this technique in the clinic and our interest in the mechanisms of tissue regeneration (notably bone regeneration) prompted us to develop a surgical model of the Masquelet technique in rats. Here, we provide a comprehensive review of the literature on animal models of membrane induction, encompassing the defect site, the surgical procedure, and the histologic and osteogenic properties of the induced membrane. We also discuss the advantages and disadvantages of those models to facilitate efforts in characterizing the complex biological mechanisms that underlie membrane induction.

Anatomy of the posterior branch of the medial antebrachial cutaneous nerve: A cadaveric study.

PURPOSE: The posterior branch of the medial antebrachial cutaneous nerve (MACN) is at risk to be damaged during cubital tunnel surgery. The purpose of this study was to identify the location of the posterior branch of the MACN (PBMACN) in relation to surgical landmarks pertinent in cubital tunnel surgery. METHODS: We performed an anatomical study on 20 limbs from 13 fresh cadavers. The nerve was dissected from 10cm proximal to 10cm distal of the medial epicondyle. We measured the distance between the nerve and the medial epicondyle, and also the distance separating the PBMACN from the ulnar nerve passage between the two heads of the flexor carpi ulnaris. Measurements were performed with the elbow at 45° and 90° of flexion, as well as in full pronation and supination. RESULTS: After its emergence from the main trunk of the MACN, the posterior branch ran anteriorly to the medial epicondyle, taking an oblique direction toward the ulnar shaft. The PBMACN was in average 2.53cm under the medial epicondyle when the elbow was flexed at 45°, and 2.96cm when the elbow was flexed at 90°. Average distance between the PBMACN and the penetrating point of the ulnar nerve within the flexor carpi ulnaris was 1.54cm when the elbow was flexed at 45°, and 1.62cm when the elbow was flexed at 90°. Pronation and supination positions of the forearm did not significantly modify our measurements. CONCLUSIONS: Understanding the position of MACN posterior branch during ulnar nerve release surgery at the elbow may help in preventing iatrogenic injury. According to our measurements, incision and superficial dissection anterior to the medial epicondyle or distal to the ulnar nerve penetrating point between the two heads of the flexor carpi ulnaris should be avoided or done with an elbow flexed at 90°.

Induced-membrane treatment of refractory humeral non-union with or without bone defect.

INTRODUCTION: Treatment of humeral non-union with or without bone defect is complex, with non-negligible rates of complication and failure. Few reports focused on management of treatment failure. OBJECTIVE: The study hypothesis was that the induced-membrane technique associated in a 2-stage strategy to internal fixation provides systematic bone healing in refractory humeral non-union. MATERIAL AND METHODS: The study included 15 patients, with a median age of 46.6 years, with humeral non-union of a mean 24 months' progression and mean history of 3 attempted revision surgeries. Seven patients showed bone defect, exceeding 5cm in 2 cases. Six had history of radial palsy. RESULTS: Consolidation was achieved in all cases, at a mean 4.6 months. Ten patients underwent radial nerve transposition, 6 of whom had shown radial motor nerve palsy; all recovered within 2 to 5 months. There was 1 case of superficial infection, and 1 of seroma. DISCUSSION: The induced-membrane technique ensures bone healing due to the biological properties of the membrane; the main drawback is the need for 2-stage surgery. When bone defect exceeds 5cm, a multi-perforated fibula segment can be placed inside the membrane to increase primary stability and enhance bone integration. CONCLUSION: The induced-membrane technique is suited to humeral non-union, with or without bone defect. The 2-stage strategy is mandatory in case of suspected latent infection. In the 2-stage procedure, anteromedial radial nerve transposition facilitates the bone-graft stage. LEVEL OF EVIDENCE: IV, retrospective study.

A tumor-specific neoepitope expressed in homologous/self or heterologous/viral antigens induced comparable effector CD8+ T-cell responses by DNA vaccination.

Somatic mutations in tumors often generate neoproteins that contain MHC-I-binding neoepitopes. Little is known if and how efficient tumor-specific neoantigens activate CD8+ T cells. Here, we asked whether a de novo generated neoepitope, encoded either within an otherwise conserved and ubiquitously expressed self-antigen or in a chimeric HBV core antigen expression platform, providing heterologous helper functions, induces CD8+ T cells in C57Bl/6J mice by DNA immunization. For it, we chose an established Db/Sp244-252/R251H neoepitope generated in the murine Endophilin-B2/SH3GLB2 (EndoB2-Sp) protein by a single amino acid exchange. We showed that a single injection of EndoB2-Sp expression vectors efficiently primed dimer/pentamer+, IFN-γ+ and cytolytic Db/Sp244-252/R251H-specific effector CD8+ T cells in C57Bl/6J mice. Priming of Db/Sp244-252/R251H-specific CD8+ T cells proceeded independent from CD4+ T-cell help in MHC-II-deficient Aα-/- mice. As compared to the homologous EndoB2-Sp vaccine, the selective expression of the Db/Sp244-252/R251H neoepitope in chimeric particle-forming and assembly-deficient HBV core antigens induced comparable frequencies Db/Sp244-252/R251H-specific CD8+ T cells with the same cytolytic effector phenotype. The homologous EndoB2 carrier, but not the nine-residue neoepitope presented on chimeric HBV core particles, induced EndoB2-specific IgG antibody responses. The HBV core expression platform is thus an attractive option to selectively induce neoepitope-specific effector CD8+ T cells by DNA vaccination. These novel findings have practical implications for the design of heterologous/self and heterologous/viral cancer vaccines that prime and/or activate neoepitope-specific CD8+ T cells.

Towards Understanding Therapeutic Failures in Masquelet Surgery: First Evidence that Defective Induced Membrane Properties are Associated with Clinical Failures.

The two-stage Masquelet induced-membrane technique (IMT) consists of cement spacer-driven membrane induction followed by an autologous cancellous bone implantation in this membrane to promote large bone defect repairs. For the first time, this study aims at correlating IMT failures with physiological alterations of the induced membrane (IM) in patients. For this purpose, we compared various histological, immunohistochemical and gene expression parameters obtained from IM collected in patients categorized lately as successfully (Responders; n = 8) or unsuccessfully (Non-responders; n = 3) treated with the Masquelet technique (6 month clinical and radiologic post-surgery follow-up). While angiogenesis or macrophage distribution pattern remained unmodified in non-responder IM as compared to responder IM, we evidenced an absence of mesenchymal stem cells and reduced density of fibroblast-like cells in non-responder IM. Furthermore, non-responder IM exhibited altered extracellular matrix (ECM) remodeling parameters such as a lower expression ratio of metalloproteinase-9 (MMP-9)/tissue inhibitor of metalloproteinases (TIMP-1) mRNA as well as an important collagen overexpression as shown by picrosirius red staining. In summary, this study is the first to report evidence that IMT failure can be related to defective IM properties while underlining the importance of ECM remodeling parameters, particularly the MMP-9/TIMP-1 gene expression ratio, as early predictive biomarkers of the IMT outcome regardless of the type of bone, fracture or patient characteristics.