Multicenter external validation of prediction models for clinical outcomes after spinal fusion for lumbar degenerative disease.

BACKGROUND: Clinical prediction models (CPM), such as the SCOAP-CERTAIN tool, can be utilized to enhance decision-making for lumbar spinal fusion surgery by providing quantitative estimates of outcomes, aiding surgeons in assessing potential benefits and risks for each individual patient. External validation is crucial in CPM to assess generalizability beyond the initial dataset. This ensures performance in diverse populations, reliability and real-world applicability of the results. Therefore, we externally validated the tool for predictability of improvement in oswestry disability index (ODI), back and leg pain (BP, LP). METHODS: Prospective and retrospective data from multicenter registry was obtained. As outcome measure minimum clinically important change was chosen for ODI with ≥ 15-point and ≥ 2-point reduction for numeric rating scales (NRS) for BP and LP 12 months after lumbar fusion for degenerative disease. We externally validate this tool by calculating discrimination and calibration metrics such as intercept, slope, Brier Score, expected/observed ratio, Hosmer-Lemeshow (HL), AUC, sensitivity and specificity. RESULTS: We included 1115 patients, average age 60.8 ± 12.5 years. For 12-month ODI, area-under-the-curve (AUC) was 0.70, the calibration intercept and slope were 1.01 and 0.84, respectively. For NRS BP, AUC was 0.72, with calibration intercept of 0.97 and slope of 0.87. For NRS LP, AUC was 0.70, with calibration intercept of 0.04 and slope of 0.72. Sensitivity ranged from 0.63 to 0.96, while specificity ranged from 0.15 to 0.68. Lack of fit was found for all three models based on HL testing. CONCLUSIONS: Utilizing data from a multinational registry, we externally validate the SCOAP-CERTAIN prediction tool. The model demonstrated fair discrimination and calibration of predicted probabilities, necessitating caution in applying it in clinical practice. We suggest that future CPMs focus on predicting longer-term prognosis for this patient population, emphasizing the significance of robust calibration and thorough reporting.

Coccygectomy for refractory coccydynia, old-fashioned but effective procedure: A retrospective analysis.

PURPOSE: Coccydynia, characterized by persistent pain in the coccygeal region, significantly impacts patients' quality of life. While various treatment modalities exist, including conservative measures and surgical interventions like coccygectomy, optimal management remains unclear. This retrospective cohort study aimed to compare the clinical outcomes, functional improvements, and quality of life in patients with chronic coccydynia undergoing either infiltrative treatment or coccygectomy. METHODS: Data from patients treated at our institution from January 2018 to December 2022 were analyzed. Participants meeting inclusion criteria were divided into two groups: Group A underwent coccygectomy, while Group B received conservative therapy. Clinical assessments, radiographic evaluations, and patient-reported outcomes were collected preoperatively and at follow-up intervals. RESULTS: Of the 223 initially examined patients, 55 met inclusion criteria. Group A (n = 21) underwent coccygectomy, while Group B (n = 34) received conservative therapy. Both groups showed significant pain reduction post-intervention, with sustained improvement in Group A. Functional outcomes favoured Group A, with significant improvements in disability and quality of life measures. Complications were minimal, with only one case of superficial wound infection in Group A. CONCLUSION: Our findings suggest that coccygectomy provides superior and lasting pain relief, functional improvement, and quality of life improvement compared to conservative therapy. While complications were minimal, further research with larger cohorts is warranted to validate these results and explore long-term outcomes. Despite its historical association with complications, advancements in surgical techniques and perioperative care have led to improved outcomes and reduced complication rates. Thus, coccygectomy should be considered in the treatment algorithm for patients with debilitating coccydynia.

Vertebral Candidiasis, the State of the Art: A Systematic Literature Review.

OBJECTIVE: In recent years, Candida spondylodiscitis has represented an increasingly emerging disease in clinical practice. This condition requires long-term antibiotic therapy and sometimes surgical treatments. The main purpose of this study is to investigate the epidemiology, clinical and radiological aspects, treatment protocols, and outcomes of Candida-mediated vertebral osteomyelitis. METHODS: A systematic review of the English literature was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.The research was conducted on Medline, Cochrane library, PubMed, and Scopus using as search terms "vertebral"; "spinal"; "infection"; "spondylodiscitis"; "discitis"; "osteomyelitis"; "Candida"; and "Candidosis." A case of vertebral candidiasis that was surgically managed was also reported. RESULTS: In total, 88 articles were included in our systematic review. Including the reported case, our analysis covered 113 cases of vertebral candidiasis. Candida albicans was isolated in 64 cases (56.1%), Candida tropicalis in 21 (18.4%), Candida glabrata in 14 (12.3%), and Candida parapsilosis in five (4.4%). The mean duration of the follow-up was 395 days. Finally, 87 (82%) patients completely recovered, ten (9.4%) died, and nine (8.5%) reported sequelae. CONCLUSION: This systematic review summarized the state of the art on vertebral candidiasis, describing data on its clinical features, diagnostic criteria and current limitations, and treatment alternatives and their outcomes.

Long-Term Clinical and Radiographic Outcomes After Bryan Cervical Disk Arthroplasty: A Systematic Literature Review.

Introductionː Cervical disk arthroplasty is a potential alternative procedure to anterior cervical decompression and fusion for the treatment of cervical disk disease. The aim of the study was to perform a systematic literature review on long-term clinical and radiological outcomes after Bryan cervical disk arthroplasty.Material and Methodsː A systematic literature review was performed according to PRISMA guidelines via PubMed and Embase, Scopus, and the Cochrane Library database by using the following keywords: "Bryan prosthesis"; "cervical disk arthroplasty"; "outcomes"; and "long-term follow-up." Eight articles with at least 10 years of follow-up were considered for eligibility.Resultsː In total, 481 patients were enrolled in the studies. Because of the occurrence of multiple treated levels, 588 arthroplasties were performed, divided as follows: 12 C3/4 cervical disk arthroplasties (2.01%), 63 C4/5 (10.71%), 325 C5/6 (55.27%), and 188 C6/7 (31.97%). The mean preoperative cervical lordosis was 13.6 ± 9.3°, whereas the last follow-up value was 12.8 ± 8.7°. In the last follow-up, the mean segmental range of motion was 8.2 ± 3.3°.Discussion: Recent studies have suggested that cervical disk arthroplasty should be safely performed in healthy young patients with disk degeneration who may need future revision surgery. The results suggest that this procedure preserves native cervical spinal biomechanics at long-term follow-up with acceptable adjacent segments disease and periprosthetic ossifications.Conclusionsː Cervical disk arthroplasty has good long-term device survival, motility, adjacent segment degeneration, and clinical outcomes. Therefore, it represents a valid alternative for the treatment of cervical spine degenerative pathologies, especially in young patients.

Extreme Lateral Interbody Fusion (XLIF) with Lateral Modular Plate Fixation: Preliminary Report on Clinical and Radiological Outcomes.

The lateral transpsoas approach (extreme lateral interbody fusion, or XLIF) allows surgeons to use various lordotic cage sizes to help restore intervertebral disk height, correct sagittal alignment, and improve fusion rates. The use of standalone devices has consistently raised doubts due to the high risk of complications and inadequate functional recovery that a circumferential arthrodesis can support. The recent introduction of a novel XLIF cage with adapted lateral plate fixation (XLPF) may further enhance the structural rigidity, consolidating the cage and plate into a singular modular entity. Nine patients from our surgical centers underwent a procedure of 1-level XLIF with XLPF in selected cases. We observed that XLPF does not extend the intraoperative footprint and provides immediate rigidity to the anterior column without any additional risk of complications and with minimal increased time compared to the traditional cage implant procedure. Although it has been shown that the use of interbody fusion cages with supplemental posterior fixation improves stabilization in all directions, the technique of standalone lateral cages may also have a place in spine surgery in that the stability may be sufficient in selected cases, such as junctional syndrome and in some forms of degenerative scoliosis.

Correlation between traumatic pelvic ring injuries and sexual dysfunctions: a multicentric retrospective study.

PURPOSE: Among the functional impairments associated with pelvic ring injuries (PRI), sexual dysfunction (SD) is a common clinical issue. The aim of this study is to investigate correlations between traumatic PRI, genitourinary, and sexual dysfunctions, for a proper multidisciplinary treatment. METHODS: We performed an observational, multicentric study, from January 2020 to 2022. We conducted a follow-up after surgery at three, six, 12, and 24 months by measuring the Female Sexual Functioning Index (FSFI), the International Index of Erectile Function (IIEF), the Arizona Sexual Experience Scale (ASEX), the Majeed Score, and the SF-12. Descriptive statistics was conducted on T-test, Whelc's test, and one-way ANOVA which were performed when appropriate. RESULTS: A total of 76 patients (mean age 42.17 ± 15 years) were included in the study and allocated into three groups (A, B, and C). Tile A group revealed good sexual outcomes, similar to that of healthy patients. Tile B group demonstrated worsen SD than the previous group. In Tile C group, there was a longer average duration of the orthopaedic surgery when compared to group B. However, in terms of SDs, statistical significance could not be demonstrated between groups C and B. CONCLUSIONS: We observed a progressive spontaneous recovery of sexual function, corresponding to each PRI group. Moreover, men classified as B2 had milder SDs than B1 male patients.

FUSE-ML: development and external validation of a clinical prediction model for mid-term outcomes after lumbar spinal fusion for degenerative disease.

BACKGROUND: Indications and outcomes in lumbar spinal fusion for degenerative disease are notoriously heterogenous. Selected subsets of patients show remarkable benefit. However, their objective identification is often difficult. Decision-making may be improved with reliable prediction of long-term outcomes for each individual patient, improving patient selection and avoiding ineffective procedures. METHODS: Clinical prediction models for long-term functional impairment [Oswestry Disability Index (ODI) or Core Outcome Measures Index (COMI)], back pain, and leg pain after lumbar fusion for degenerative disease were developed. Achievement of the minimum clinically important difference at 12 months postoperatively was defined as a reduction from baseline of at least 15 points for ODI, 2.2 points for COMI, or 2 points for pain severity. RESULTS: Models were developed and integrated into a web-app ( https://neurosurgery.shinyapps.io/fuseml/ ) based on a multinational cohort [N = 817; 42.7% male; mean (SD) age: 61.19 (12.36) years]. At external validation [N = 298; 35.6% male; mean (SD) age: 59.73 (12.64) years], areas under the curves for functional impairment [0.67, 95% confidence interval (CI): 0.59-0.74], back pain (0.72, 95%CI: 0.64-0.79), and leg pain (0.64, 95%CI: 0.54-0.73) demonstrated moderate ability to identify patients who are likely to benefit from surgery. Models demonstrated fair calibration of the predicted probabilities. CONCLUSIONS: Outcomes after lumbar spinal fusion for degenerative disease remain difficult to predict. Although assistive clinical prediction models can help in quantifying potential benefits of surgery and the externally validated FUSE-ML tool may aid in individualized risk-benefit estimation, truly impacting clinical practice in the era of "personalized medicine" necessitates more robust tools in this patient population.

Gibson approach and surgical hip dislocation according to Ganz in the treatment of femoral head fractures.

BACKGROUND: The purpose of the study is to evaluate clinical and radiological outcomes in those patients with femoral head fracture, treated with open reduction and internal fixation through Gibson approach and Ganz flip trochanter osteotomy. The treatment of Pipkin fractures is very challenging, especially for small trauma centers, because of the unusual fracture patterns and high-level surgical skills required. CASE PRESENTATION: Between 2017 and 2020, nine cases of Pipkin fractures came to the Emergency Department at the Trauma Center of our Hospital in Rome. Inclusion criteria were the diagnosis of femoral head fracture, the open reduction and internal fixation as surgical choice and at least 24 months follow-up. Patients older than 65 years and those treated through total hip replacement or combined hip procedure (CHP) were excluded. Thus, five patients were included in our case series. The clinical outcome was evaluated according to Western Ontario and McMaster Universities Arthritis Index, Vail Hip score, modified Harris Hip score and Merle D'Aubignè Postel score. Radiographic assessment was scored according to Epstein-Thompson classification and heterotopic ossification was assessed through Brooker classification. The mean follow-up was 24 months (range 12-24). Average modified Harris Hip score was 92.1 points (range 75.9-100), and the average Vail score was 81.8 (range 55-95). WOMAC score was assessed in three different subscales, pain (A), stiffness (B) and physical condition (C), with the following results: 1.4 A (range 0-7), 1.2 B (range 0-6) and 6.4 C (range 0-22). Merle d'Aubignè Postel score resulted excellent for four patients and good for one patient. According to Epstein-Thompson score of the radiological outcome, four patients showed a good result and one a fair result. No mechanical or infective complications occurred in the five patients. CONCLUSIONS: Gibson's approach and surgical hip dislocation through Ganz trochanteric flip osteotomy allow a good exposure of the femoral head and acetabulum, giving us the possibility to perform an anatomical reduction of the fracture. In our case series, satisfactory clinical and radiological short-term results were obtained without significant complications.

The role of femoral obliquity angle and T1 pelvic angle in predicting quality of life after spinal surgery in adult spinal deformities.

BACKGROUND: Adult spinal deformities (ASD) represent a growing clinical condition related to chronic pain, disability and reduction in quality of life (QoL). A strong correlation among spinal alignment, spinopelvic parameters and QoL after spinal fusion surgery in ASD patients was thoroughly investigated over the last decade, However, only few studies focused on the relationship between lumbo-pelvic-femoral parameters - such as Femoral Obliquity Angle (FOA), T1 Pelvic Angle (TPA) and QoL. METHODS: Radiological and clinical data from 43 patients surgically treated with thoracolumbar posterior spinal fusion for ASD between 2015 and 2018 were retrospectively analyzed. The primary outcomes were the correlation between preoperative spino-pelvic-femoral parameters and postoperative clinical, functional outcomes and QoL. Secondary outcomes were: changes in sagittal radiographic parameters spino-pelvic-femoral, clinical and functional outcomes and the rate of complications after surgery. RESULTS: Using Spearman's rank correlation coefficients, spinopelvic femoral parameters (FOA, TPA, pre and post-operative) are directly statistically correlated to the quality of life (ODI, SRS-22, pre and post-operative; > 0,6 strong correlation, p <  0.05). Stratifying the patients according pre preoperative FOA value (High FOA ≥ 10 and Normal/Low FOA <  10), those belonging to the first group showed worse clinical (VAS: 5.2 +/- 1.4 vs 2.9 +/- 0.8) and functional outcomes (ODI: 35.6+/- 6.8 vs 23.2 +/- 6.5) after 2 years of follow-up and a greater number of mechanical complications (57.9% vs 8.3% p <  0.0021). CONCLUSION: Based on our results, preoperative FOA and TPA could be important prognostic parameters for predicting disability and quality of life after spinal surgery in ASD patients and early indicators of possible spinal sagittal malalignment. FOA and TPA, like other and better known spinopelvic parameters, should always be considered when planning corrective surgery in ASD patients.

Radiological evaluation of fusion patterns after lateral lumbar interbody fusion: institutional case series.

INTRODUCTION: There is no consensus on how to evaluate segmental fusion after lateral lumbar interbody fusion (LLIF). Bone bridges (BB) between two contiguous vertebra are reported as pathognomonic criteria for anterior fusion. However, to the best of our knowledge, there are no radiological investigations on zygapophyseal joints (ZJ) status after LLIF. The aim of this radiological study was to investigate the different fusion patterns after LLIF. MATERIALS AND METHODS: This is a retrospective single-centre radiological study. Patients who underwent LLIF and posterior percutaneous screw fixation for degenerative spondylolisthesis, on a single lumbar level, were considered for eligibility. Complete radiological data and a minimum follow-up of 1 year were the inclusion criteria. Intervertebral BB were investigated for evaluating anterior fusion and ZJ ankylotic degeneration was evaluated according Pathria et al., as a matter of proof of posterior fusion and segmental immobilization. RESULTS: Seventy-four patients were finally included in the present study. Twelve months after surgery, intervertebral BB were recognized in 58 segments (78.3%), whereas ZJ Pathria grade was I in 8 (10.8%) patients, II in 15 (20.3%) and III in 51 (68.9%) that were considered posteriorly fused. The overlapping rate between anteriorly and posteriorly fused segments was 72.4% (42 segments), whereas 10 (13.5%) did not achieve any fusion, anterior or posterior, and 6 (8.1%) were posteriorly fused only. CONCLUSIONS: Our results seem to suggest that anterior fusion is not sufficient to achieve segmental immobilization. Further properly designed investigations are needed to investigate eventual clinical-radiological correlations.

Epidemiology and aetiology of male and female sexual dysfunctions related to pelvic ring injuries: a systematic review.

INTRODUCTION: Pelvic ring injuries, frequently caused by high energy trauma, are associated with high rates of morbidity and mortality (5-33%), often due to significant blood loss and disruption of the lumbosacral plexus, genitourinary system, and gastrointestinal system. The aim of the present study is to perform a systematic literature review on male and female sexual dysfunctions related to traumatic lesions of the pelvic ring. METHODS: Scopus, Cochrane Library MEDLINE via PubMed, and Embase were searched using the keywords: "Pelvic fracture," "Pelvic Ring Fracture," "Pelvic Ring Trauma," "Pelvic Ring injury," "Sexual dysfunction," "Erectile dysfunction," "dyspareunia," and their MeSH terms in any possible combination. The following questions were formulated according to the PICO (population (P), intervention (I), comparison (C), and outcome (O)) scheme: Do patients suffering from pelvic fracture (P) report worse clinical outcomes (C), in terms of sexual function (O), when urological injury occurs (I)? Is the sexual function (O) influenced by the type of fracture (I)? RESULTS: After screening 268 articles by title and abstract, 77 were considered eligible for the full-text analysis. Finally 17 studies that met inclusion criteria were included in the review. Overall, 1364 patients (902 males and 462 females, M/F ratio: 1.9) suffering from pelvic fractures were collected. DISCUSSION: Pelvic fractures represent challenging entities, often concomitant with systemic injuries and subsequent morbidity. Anatomical consideration, etiology, correlation between sexual dysfunction and genitourinary lesions, or pelvic fracture type were investigated. CONCLUSION: There are evidences in the literature that the gravity and frequency of SD are related with the pelvic ring fracture type. In fact, patients with APC, VS (according Young-Burgess), or C (according Tile) fracture pattern reported higher incidence and gravity of SD. Only a week association could be found between GUI and incidence and gravity of SD, and relationship between surgical treatment and SD. Electrophysiological tests should be routinely used in patient suffering from SD after pelvic ring injuries.

The effect of nest topology on spatial organization and recruitment in the red ant Myrmica rubra.

Nests of social insects are an important area for the exchange of food and information among workers. We investigated how the topology of nest chambers (as opposed to nest size or environmental factors) affects the spatial distribution of nestmates and the foraging behavior of Myrmica rubra ant colonies. Colonies were housed in artificial nests, each with same-sized chambers differing in the spatial arrangement of galleries. A highly connected central chamber favored higher occupancy rates and a more homogeneous distribution of ants across chambers. In contrast, a chain of successive chambers led to a more heterogeneous distribution of ants, with the occupancy of a chamber chiefly mediated by its distance to the entrance. Irrespective of nest topology, the entrance chamber housed the largest proportion of ants, often including the queen, which exhibited a preference for staying in densely populated chambers. Finally, we investigated how nest topology influenced nestmate recruitment. Surprisingly, a highly connected chamber in the center of the nest did not promote greater recruitment nor activation of ants. At the onset of foraging, the largest number of moving ants was reached in the topology where the most connected chamber was the nest entrance. Later in the process, we found that a chain of successive chambers was the best topology for promoting ant's mobilization. Our work demonstrates that nest topology can shape the spatial organization and the collective response of ant colonies, thereby taking part in their adaptative strategies to exploit environmental resources.

Single-level Bryan cervical disc arthroplasty: evaluation of radiological and clinical outcomes after 18 years of follow-up.

PURPOSE: Many studies reported mid-term clinical and radiological outcomes after cervical disc arthroplasty. Only a few studies analysed the long-term results. The aim of the study was to evaluate the clinical and radiological outcomes in patients treated with single-level Bryan cervical disc arthroplasty after 18 years of follow-up. METHODS: This study was a retrospective analysis of institutional databases concerning patients treated with Bryan cervical disc arthroplasty. SF36 PCS, NDI and VAS were used to evaluate clinical and functional outcomes. Standard, flexion-extension X-ray and MRI were used to evaluate the radiological results. RESULTS: Fifty-seven patients treated with single-level Bryan cervical disc arthroplasty completed the 18-year follow-up. At the final follow-up, a residual movement was observed in 32 patients (56%). The treated level range of motion decreased from 10.1° pre-operatively to 6.1° at the last follow-up (p = 0.0021). The range of motion of the adjacent segments and of the cervical spine had no significant change. Disc degeneration of the adjacent segment after 18-year follow-up was observed in 77.1% of treated patients. CONCLUSION: The clinical and radiographic outcomes 18 years after surgery are acceptable. The treated level range of motion reduction and the adjacent segment degeneration seems not to affect the clinical results after 18 years of follow-up.

Extraphyseal distal radius fracture in children: is the cast always needed? A retrospective analysis comparing Epibloc system and K-wire pinning.

INTRODUCTION: Closed reduction and internal fixation are a widespread surgical treatment for pediatrics displaced extraphyseal distal radius fractures. Post-surgical cast immobilization is usually needed. Epibloc system (ES) is a device used to fix Colles fractures in adults, not requiring post-surgical immobilization. The aim of the study is to investigate the effectiveness of ES in a pediatric population suffering from displaced extraphyseal distal radius fractures. METHODS: We retrospectively analyzed 52 patients (age 8-12 years) who underwent CRIF. Patients were divided into two groups. Group A (25 patients): ES osteosynthesis. Group B (27 patients): K-wires and short arm cast osteosynthesis. The primary outcome is the maintenance of reduction in radiographs (displacement on frontal and lateral view). The secondary outcome is the reaching of the complete active range of motion recovery (compared with the contralateral side) and the time needed to obtain it. The need of further additional treatment (physiotherapy) and the presence of complication were also assessed. RESULTS: Reduction was equally maintained in both groups (p > 0.05). Physiotherapy was mandatory for 11 patients in group B; only for 3 patients in group A, the difference was statistically significant (p = 0.03) according to Fisher test. Otherwise, the difference was not statistically significant regarding complications. (p > 0.05). At the last follow-up, complete functional recovery was reached in all patients. CONCLUSIONS: Functional recovery is faster, and postoperative physiotherapy is rarely required with ES. This device allows us to go beyond the traditional concept of mandatory postoperative immobilization after pediatric wrist fractures surgery.

Regression dilution in energy management patterns.

Analysis of some experimental biology data involves linear regression and interpretation of the resulting slope value. Usually, the x-axis measurements include noise. Noise in the x-variable can create regression dilution, and many biologists are not aware of the implications: regression dilution results in an underestimation of the true slope value. This is particularly problematic when the slope value is diagnostic. For example, energy management strategies of animals can be determined from the regression slope estimate of mean energy expenditure against resting energy expenditure. Typically, energy expenditure is represented by a proxy such as heart rate, which adds substantive measurement error. With simulations and analysis of empirical data, we explore the possible effect of regression dilution on interpretations of energy management strategies. We conclude that unless the coefficient of determination r2 is very high, there is a good possibility that regression dilution will affect qualitative interpretation. We recommend some ways to contend with regression dilution, including the application of alternative available regression approaches under certain circumstances.

Stigmergic construction and topochemical information shape ant nest architecture.

The nests of social insects are not only impressive because of their sheer complexity but also because they are built from individuals whose work is not centrally coordinated. A key question is how groups of insects coordinate their building actions. Here, we use a combination of experimental and modeling approaches to investigate nest construction in the ant Lasius niger. We quantify the construction dynamics and the 3D structures built by ants. Then, we characterize individual behaviors and the interactions of ants with the structures they build. We show that two main interactions are involved in the coordination of building actions: (i) a stigmergic-based interaction that controls the amplification of depositions at some locations and is attributable to a pheromone added by ants to the building material; and (ii) a template-based interaction in which ants use their body size as a cue to control the height at which they start to build a roof from existing pillars. We then develop a 3D stochastic model based on these individual behaviors to analyze the effect of pheromone presence and strength on construction dynamics. We show that the model can quantitatively reproduce key features of construction dynamics, including a large-scale pattern of regularly spaced pillars, the formation and merging of caps over the pillars, and the remodeling of built structures. Finally, our model suggests that the lifetime of the pheromone is a highly influential parameter that controls the growth and form of nest architecture.

Extensive Spinal Epidural Abscesses Resolved with Minimally Invasive Surgery: Two Case Reports and Review of the Recent Literature.

PURPOSE: An extensive spinal epidural abscess is a rare condition and causes significant morbidity and mortality. Few authors have described this uncommon entity, which requires early diagnosis and optimal treatment to avoid devastating complications. The purpose of this study was to evaluate a minimally invasive technique for treatment of an extensive spinal epidural abscess by describing two cases. Furthermore, we conducted a review of the recent literature on the management of this rare condition. METHODS: We report two cases of spinal abscesses extending to the whole epidural space, successfully treated by use of a minimally invasive technique consisting of multilevel laminotomy and catheter irrigation to decompress and drain the epidural space. RESULTS: This technique is able to decompress the spinal cord, isolate the pathogen and evacuate the abscess. No complications, late spine deformity or dura penetration were observed in our patients. CONCLUSION: Urgent surgical decompression, in combination with long-term antibiotic treatment, is generally considered the treatment of choice for an extensive spinal epidural abscess. A minimally invasive technique can be very useful as a surgical option.

Identifying influential neighbors in animal flocking.

Schools of fish and flocks of birds can move together in synchrony and decide on new directions of movement in a seamless way. This is possible because group members constantly share directional information with their neighbors. Although detecting the directionality of other group members is known to be important to maintain cohesion, it is not clear how many neighbors each individual can simultaneously track and pay attention to, and what the spatial distribution of these influential neighbors is. Here, we address these questions on shoals of Hemigrammus rhodostomus, a species of fish exhibiting strong schooling behavior. We adopt a data-driven analysis technique based on the study of short-term directional correlations to identify which neighbors have the strongest influence over the participation of an individual in a collective U-turn event. We find that fish mainly react to one or two neighbors at a time. Moreover, we find no correlation between the distance rank of a neighbor and its likelihood to be influential. We interpret our results in terms of fish allocating sequential and selective attention to their neighbors.

Minimally invasive surgery procedure in isthmic spondylolisthesis.

PURPOSE: The aim of the study was to evaluate the efficacy and safety of the direct lateral approach to the lumbar spine in the treatment of painful isthmic spondylolisthesis in adults. METHODS: Twenty-one patients affected by isthmic spondylolisthesis and treated with extreme lateral interbody fusion and posterior percutaneous pedicle screw fixation were enrolled. All included patients were clinically evaluated with Oswestry Disability Index, SF36 and Visual Scale Anatomy (VAS) for back pain at 1, 3 months and at 1 year. RESULTS: The mean correction of vertebral slippage measured on lateral lumbar X-ray was 56.3% (p = 0.002). The average preoperative VAS score was 7.1, at 1 year decreasing to 2.2 (p = 0.001). The patients had an average preoperative "Oswestry Disability Index" of 36.8 and 24.1% after 1 year (p = 0.02). The preoperative Short-Form 36 Physical Health was equal to 33.8, 72.1% after 1 month, to 76.3% after 3 months and to 83.2% (p = 0.001) after 1 year of follow-up. There were no signs of implant loosening at 1-year CT scan examination in any of the patients. CONCLUSION: The study showed that the extreme lateral approach to the lumbar spine in case of isthmic spondylolisthesis is a reliable and safe option to the most common open procedures. In the authors' opinion, XLIF procedures allow a good correction of the listhesis associated with good clinical and radiographic results. These slides can be retrieved under Electronic supplementary material.

How predation shapes the social interaction rules of shoaling fish.

Predation is thought to shape the macroscopic properties of animal groups, making moving groups more cohesive and coordinated. Precisely how predation has shaped individuals' fine-scale social interactions in natural populations, however, is unknown. Using high-resolution tracking data of shoaling fish (Poecilia reticulata) from populations differing in natural predation pressure, we show how predation adapts individuals' social interaction rules. Fish originating from high predation environments formed larger, more cohesive, but not more polarized groups than fish from low predation environments. Using a new approach to detect the discrete points in time when individuals decide to update their movements based on the available social cues, we determine how these collective properties emerge from individuals' microscopic social interactions. We first confirm predictions that predation shapes the attraction-repulsion dynamic of these fish, reducing the critical distance at which neighbours move apart, or come back together. While we find strong evidence that fish align with their near neighbours, we do not find that predation shapes the strength or likelihood of these alignment tendencies. We also find that predation sharpens individuals' acceleration and deceleration responses, implying key perceptual and energetic differences associated with how individuals move in different predation regimes. Our results reveal how predation can shape the social interactions of individuals in groups, ultimately driving differences in groups' collective behaviour.