Use of the margin of stability to quantify stability in pathologic gait - a qualitative systematic review.

BACKGROUND: The Margin of Stability (MoS) is a widely used objective measure of dynamic stability during gait. Increasingly, researchers are using the MoS to assess the stability of pathological populations to gauge their stability capabilities and coping strategies, or as an objective marker of outcome, response to treatment or disease progression. The objectives are; to describe the types of pathological gait that are assessed using the MoS, to examine the methods used to assess MoS and to examine the way the MoS data is presented and interpreted. METHODS: A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines (PRISMA) in the following databases: Web of Science, PubMed, UCL Library Explore, Cochrane Library, Scopus. All articles measured the MoS of a pathologically affected adult human population whilst walking in a straight line. Extracted data were collected per a prospectively defined list, which included: population type, method of data analysis and model building, walking tasks undertaken, and interpretation of the MoS. RESULTS: Thirty-one studies were included in the final review. More than 15 different clinical populations were studied, most commonly post-stroke and unilateral transtibial amputee populations. Most participants were assessed in a gait laboratory using motion capture technology, whilst 2 studies used instrumented shoes. A variety of centre of mass, base of support and MoS definitions and calculations were described. CONCLUSIONS: This is the first systematic review to assess use of the MoS and the first to consider its clinical application. Findings suggest the MoS has potential to be a helpful, objective measurement in a variety of clinically affected populations. Unfortunately, the methodology and interpretation varies, which hinders subsequent study comparisons. A lack of baseline results from large studies mean direct comparison between studies is difficult and strong conclusions are hard to make. Further work from the biomechanics community to develop reporting guidelines for MoS calculation methodology and a commitment to larger baseline studies for each pathology is welcomed.

Analysing a mechanism of failure in retrieved magnetically controlled spinal rods.

PURPOSE: We aim to describe a mechanism of failure in magnetically controlled growth rods which are used for the correction of the early onset scoliosis. METHODS: This retrieval study involved nine magnetically controlled growth rods, of a single design, revised from five patients for metal staining, progression of scoliosis, swelling, fractured actuator pin, and final fusion. All the retrieved rods were radiographed and assessed macroscopically and microscopically for material loss. Two implants were further analysed using micro-CT scanning and then sectioned to allow examination of the internal mechanism. No funding was obtained to analyse these implants. There were no potential conflicts interests. RESULTS: Plain radiographs revealed that three out of nine retrieved rods had a fractured pin. All had evidence of surface degradation on the extendable telescopic rod. There was considerable corrosion along the internal mechanism. CONCLUSIONS: We found that a third of the retrieved magnetically controlled growth rods had failed due to pin fracture secondary to corrosion of the internal mechanism. We recommend that surgeons consider that any inability of magnetically controlled growth rods to distract may be due to corrosive debris building up inside the mechanism, thereby preventing normal function.

A UK-based pilot study of current surgical practice and implant preferences in lumbar fusion surgery.

Lumbar fusion surgery is an established procedure for the treatment of low back pain. Despite the wide set of alternative fusion techniques and existing devices, uniform guidelines are not available yet and common surgical trends are scarcely investigated.The purpose of this UK-based study was to provide a descriptive portrait of current surgeons' practice and implant preferences in lumbar fusion surgery.A UK-based in-person survey was designed for this study and submitted to a group of consultant spinal surgeons (n = 32). Fifteeen queries were addressed based on different aspects of surgeons' practice: lumbar fusion techniques, implant preferences, and bone grafting procedures. Answers were analyzed by means of descriptive statistics.Thirty-two consultant spinal surgeons completed the survey. There was clear consistency on the relevance of a patient-centered management (82.3%), along with a considerable variability of practice on the preferred fusion approach. Fixation surgery was found to be largely adopted (96.0%) and favored over stand-alone cages. With regards to the materials, titanium cages were the most used (54.3%). The geometry of the implants influenced the choice of lumbar cages (81.3%). Specifically, parallel-shape cages were mostly avoided (89.2%) and hyperlordotic cages were preferred at the lower lumbar levels. However, there was no design for lumbar cages which was consistently favored. Autograft bone graft surgeries were the most common (60.0%). Amongst the synthetic options, hydroxyapatite-based bone graft substitutes (76.7%) in injectable paste form (80.8%) were preferred.Current lumbar fusion practice is variable and patient-oriented. Findings from this study highlight the need for large-scale investigative surveys and clinical studies aimed to set specific guidelines for certain pathologies or patient categories.

HMM assessment of quality of movement trajectory in laparoscopic surgery.

Laparoscopic surgery poses many different constraints for the operating surgeon, resulting in a slow uptake of advanced laparoscopic procedures. Traditional approaches to the assessment of surgical performance rely on prior classification of a cohort of surgeons' technical skills for validation, which may introduce subjective bias to the outcome. In this study, Hidden Markov Models (HMMs) are used to learn surgical maneuvers from 11 subjects with mixed abilities. By using the leave-one-out method, the HMMs are trained without prior clustering of subjects into different skill levels, and the output likelihood indicates the similarity of a particular subject's motion trajectories to those of the group. The results show that after a short period of training, the novices become more similar to the group when compared to the initial pre-training assessment. The study demonstrates the strength of the proposed method in ranking the quality of trajectories of the subjects, highlighting its value in minimizing the subjective bias in skills assessment for minimally invasive surgery.

Applications of 3D printing in the management of severe spinal conditions.

The latest and fastest-growing innovation in the medical field has been the advent of three-dimensional printing technologies, which have recently seen applications in the production of low-cost, patient-specific medical implants. While a wide range of three-dimensional printing systems has been explored in manufacturing anatomical models and devices for the medical setting, their applications are cutting-edge in the field of spinal surgery. This review aims to provide a comprehensive overview and classification of the current applications of three-dimensional printing technologies in spine care. Although three-dimensional printing technology has been widely used for the construction of patient-specific anatomical models of the spine and intraoperative guide templates to provide personalized surgical planning and increase pedicle screw placement accuracy, only few studies have been focused on the manufacturing of spinal implants. Therefore, three-dimensional printed custom-designed intervertebral fusion devices, artificial vertebral bodies and disc substitutes for total disc replacement, along with tissue engineering strategies focused on scaffold constructs for bone and cartilage regeneration, represent a set of promising applications towards the trend of individualized patient care.

Risk of Neurological Injuries in Spinal Deformity Surgery.

STUDY DESIGN: A retrospective study. OBJECTIVE: Rate of neurological injuries is widely reported for spinal deformity surgery. However, few have included the influence of the subtypes and severity of the deformity, or anterior versus posterior corrections. The purpose of this study is to quantify these risks. SUMMARY OF BACKGROUND DATA: The risk of neurological injuries was examined in a single institution. Quantification of risk was made between operations, and for different subtypes of spinal deformity. METHODS: Prospectively entered neuromonitoring database between 2006 and 2012 was interrogated, including all deformity cases under 21 years of age. Tumor, fracture, infection, and revision cases were excluded. All major changes in monitoring ("red alerts") were identified and detailed examinations of the neuromonitoring records, clinical notes, and radiographs were made. Diagnosis, deformity severity, and operative details were recorded. RESULTS: Of 2291 deformity operations, there were 2068 scoliosis (1636 idiopathic, 204 neuromuscular, 216 syndromic, 12 others), 89 kyphosis, 54 growing rod procedures, and 80 operations for hemivertebra. Six hundred ninety-six anterior and 1363 posterior operations were performed for scoliosis (nine not recorded), and 38 anterior and 51 posterior kyphosis corrections. Sixty-seven "red alerts" were identified (62 posterior, five anterior). Average Cobb angle was 88°. There were 14 transient and six permanent neurological injuries. One permanent injury was sustained during kyphosis correction and five during scoliosis correction. Common surgeon reactions after "red alerts" were surgical pause with anesthetic interventions (n = 39) and the Stagnara wake-up test (n = 22). Metalwork was partially removed in 20, revised in 12, and completely removed in nine. Thirteen procedures were abandoned. CONCLUSION: The overall risk of permanent neurological injury was 0.2%. The highest risk groups were posterior corrections for kyphosis, and scoliosis associated with a syndrome. Four percent of all posterior deformity corrections had "red alerts," and 0.3% resulted in permanent injuries compared with 0.6% "red alerts" and 0.3% permanent injuries for anterior surgery. The overall risk for idiopathic scoliosis was 0.06%. LEVEL OF EVIDENCE: 3.

A wearable mobility assessment device for total knee replacement: A longitudinal feasibility study.

BACKGROUND: Total knee replacement currently lacks robust indications and objective follow-up metrics. Patients and healthcare staff are under-equipped to optimise outcomes. This study aims to investigate the feasibility of using an ear-worn motion sensor (e-AR, Imperial College London) to conduct objective, home-based mobility assessments in the peri-operative setting. METHODS: Fourteen patients on the waiting list for knee replacement, and 15 healthy subjects, were recruited. Pre-operatively, and at 1, 3, 6, 12 and 24 weeks post-operatively, patients underwent functional mobility testing (Timed Up and Go), knee examination (including range of motion), and an activity protocol whilst wearing the e-AR sensor. Features extracted from sensor motion data were used to assess patient performance and predict patients' recovery phase. RESULTS: Sensor-derived peri-operative mobility trends correlated with clinical measures in several activities, allowing functional recovery of individual subjects to be profiled and compared, including the detection of a complication. Sensor data features enabled classification of subjects into normal, pre-operative and 24-week post-operative groups with 89% (median) accuracy. Classification accuracy was reduced to 69% when including all time intervals. DISCUSSION: This study demonstrates a novel, objective method of assessing peri-operative mobility, which could be used to supplement surgical decision-making and facilitate community-based follow-up.

Energy expenditure prediction using a miniaturized ear-worn sensor.

PURPOSE: This study aimed to predict human energy expenditure and activity type using a miniature lightweight ear-worn inertia sensor and a novel pattern recognition algorithm for activity detection. METHODS: This study used a protocol of 11 activities of daily living: lying down, standing, computer work, vacuuming, stairs, slow walking, brisk walking, slow running, fast running, cycling, and rowing. Subjects included 25 healthy randomized subjects (18 males and 7 females). Each participant wore the ear sensor to record posture and linear acceleration, as well as the Cosmed K4b system for indirect calorimetry. The main outcome measure was the continuous energy expenditure per minute prediction for both task-known and task-blind estimation. RESULTS: The values for METs predicted using the proposed algorithm and the measured METs using the K4b showed good agreement with low values for the systematic bias (lying down=0.01, standing=-0.02, computer work=-0.04, vacuuming=-0.17, stairs=-0.02, slow walking=0.01, fast walking=0.04, slow running=0.14, fast running=-0.35, cycling=0.32, and rowing=0.10). For task-blind prediction, the agreement between predicted and measured METs is also good with low values of the systematic bias (lying down=0.11, standing=0.14, computer work=-0.06, vacuuming=0.47, stairs=-0.47, slow walking=0.53, fast walking=-0.11, slow running=0.83, fast running=-1.18, cycling=0.31, and rowing=-0.67). Activity is also well predicted (for task-blind prediction) with an overall success rate of 88.99% and individual correct classification rates of lying down=89.62%, standing/computer work=99.10%, vacuuming=76.60%, stairs=89.13%, walking=85.11%, running=98.96%, and cycling=79.79%. CONCLUSIONS: The ear-worn sensor presented in this work is a novel lightweight device that can be used to predict energy expenditure for a range of activities without behavior interference or modification.

Could variations in technical skills acquisition in surgery be explained by differences in cortical plasticity?

SUMMARY/BACKGROUND: Variations in technical performance in surgery are known to exist but are poorly understood. Gaining an appreciation of these differences may have implications for technical skills training, assessment, and selection. Investigators attempting to correlate technical skill with visuospatial or perceptual tests have failed to identify surrogate markers of surgical aptitude. Evidence from unrelated fields suggests that studying brain function may advance our understanding of disparate technical performance in surgery. METHODS: A literature search was conducted to identify relevant studies assessing both motor skills learning and changes in brain function. RESULTS: The brain is dynamic and patterns of activation vary with experience and training, a property referred to as "neuroplasticity." Functional neuroimaging studies of complex nonsurgical skills have demonstrated smaller, more refined neuronal networks in experts compared with novices. Novel unrefined performance places a significant burden on generic areas of attention and control such as the anterior cingulate cortex and the prefrontal cortex (PFC). These regions are recruited less as skills are performed with increasing automaticity. Persistent PFC activation has been shown to herald poor bimanual coordination learning in studies involving nonsurgical tasks. CONCLUDING HYPOTHESIS: It is suspected that alterations in brain activation foci accompany a transition through phases of surgical skills learning and that those patterns of activation may vary according to technical ability. Validating this hypothesis is challenging because it requires studying brain function in ambulant subjects performing complex motor skills. In a surgical knot-tying study involving over 60 subjects of varying expertise, PFC activation was identified in novices but not in trained surgeons. Further work should aim to determine whether PFC activation attenuates in the context of learning success in surgery.

Functional prefrontal reorganization accompanies learning-associated refinements in surgery: a manifold embedding approach.

The prefrontal cortex (PFC) is known to be vital for acquisition of visuomotor skills, but its role in the attainment of complex technical skills which comprise both perceptual and motor components, such as those associated with surgery, remains poorly understood. We hypothesized that the prefrontal response to a surgical knot-tying task would be highly dependent on technical expertise, and that activation would wane in the context of learning success following extended practice. The present series of experiments investigated this issue, using functional Near Infrared Spectroscopy (fNIRS) and dexterity analysis to compare the PFC responses and technical skill of expert and novice surgeons performing a surgical knot-tying task in a block design experiment. Applying a data-embedding technique known as Isomap and Earth Mover's Distance (EMD) analysis, marked differences in cortical hemodynamic responses between expert and novice surgeons have been found. To determine whether refinement in technical skill was associated with reduced PFC demands, a second experiment assessed the impact of pre- and post-training on the PFC responses in novices. Significant improvements (p < 0.01) were observed in all performance parameters following training. Smaller EMD distances were observed between expert surgeons and novices following training, suggesting an evolving pattern of cortical responses. A random effect model demonstrated a statistically significant decrease in relative changes of total hemoglobin (Delta HbT) [coefficient = -3.825, standard error (s.e.) = 0.8353, z = -4.58, p < 0.001] and oxygenated hemoglobin (Delta HbO(2)) [coefficient = -4.6815, s.e = 0.6781, z = -6.90, p < 0.001] and a significant increase in deoxygenated hemoglobin (Delta HHb) [coefficient = 0.8192, s.e = 0.3034, z = 2.66, p < 0.01] across training. The results indicate that learning-related refinements in technical performance are mediated by temporal reductions in prefrontal activation.

HMM assessment of quality of movement trajectory in laparoscopic surgery.

Laparoscopic surgery poses many different constraints to the operating surgeon, this has resulted in a slow uptake of advanced laparoscopic procedures. Traditional approaches to the assessment of surgical performance rely on prior classification of a cohort of surgeons' technical skills for validation, which may introduce subjective bias to the outcome. In this study, Hidden Markov Models (HMMs) are used to learn surgical maneuvers from 11 subjects with mixed abilities. By using the leave-one-out method, the HMMs are trained without prior clustering subjects into different skills levels, and the output likelihood indicates the similarity of a particular subject's motion trajectories to the group. The experimental results demonstrate the strength of the method in ranking the quality of trajectories of the subjects, highlighting its value in minimizing the subjective bias in skills assessment for minimally invasive surgery.