Development of a robust crystallization platform for immune receptor TREM2 using a crystallization chaperone strategy.

TREM2 has been identified by genomic analysis as a potential and novel target for the treatment of Alzheimer's disease. To enable structure-based screening of potential small molecule therapeutics, we sought to develop a robust crystallization platform for the TREM2 Ig-like domain. A systematic set of constructs containing the structural chaperone, maltose binding protein (MBP), fused to the Ig domain of TREM2, were evaluated in parallel expression and purification, followed by crystallization studies. Using protein crystallization and high-resolution diffraction as a readout, a MBP-TREM2 Ig fusion construct was identified that generates reproducible protein crystals diffracting at 2.0 Å, which makes it suitable for soaking of potential ligands. Importantly, analysis of crystal packing interfaces indicates that most of the surface of the TREM2 Ig domain is available for small molecule binding. A proof of concept co-crystallization study with a small library of fragments validated potential utility of this system for the discovery of new TREM2 therapeutics.

Introduction of clerking pro forma for surgical spinal patients at the Royal National Orthopaedic Hospital NHS Trust (London): an audit cycle.

As a tertiary referral centre of spinal surgery, the Royal National Orthopaedic Hospital (RNOH) handles hundreds of spinal cases a year, often with complex pathology and complex care needs. Despite this, issues were raised at the RNOH following lack of sufficient documentation of preoperative and postoperative clinical findings in spinal patients undergoing major surgery. This is not in keeping with guidelines provided by the Royal College of Surgeons. The authors believe that a standardised clerking pro forma for surgical spinal patients admitted to RNOH would improve the quality of care provided. Therefore, the use of a standard clerking pro forma for all surgical spinal patients could be a useful tool enabling improvements in patients care and safety in keeping with General Medical Council/National Institute for Health and Care Excellence guidelines. An audit (with closure of loop) looking into the quality of the preoperative and postoperative clinical documentation for surgical spinal patients was carried out at the RNOH in 2016 (retrospective case note audit comparing preintervention and postintervention documentation standards). Our standardised pro forma allows clinicians to best utilise their time and standardises examination to be compared in a temporal manner during the patients admission and care. It is the authors understanding that this work is a unique study looking at the quality of the admission clerking for surgical spinal patients. Evidently, there remains work to be done for the widespread utilisation of the pro forma. Early results suggest that such a pro forma can significantly improve the documentation in admission clerking with improvements in the quality of care for patients.

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 multicentre retrospective review of muscle necrosis of the leg following spinal surgery with motor evoked potential monitoring: a cause for concern?

PURPOSE: There are very few reported cases of compartment syndrome of the leg following spinal surgery via a posterior approach. An association between compartment syndrome and muscle over-activity via nerve stimulation during evoked potential monitoring was first suggested in 2003. No further reports have suggested this link. We present a multicentre retrospective review of a series of five patients who developed compartment syndrome of the leg following spinal surgery via a posterior approach, whilst un-paralysed and with combined sensory (SSEP)/motor evoked potential (MEP) monitoring with an aim of highlighting this possible causative factor. METHODS: All data were collected contemporaneously and retrospective analysis was performed. We then arranged for a multidisciplinary review of the cases including surgeons, anaesthetists, radiologists, neurophysiologists and theatre and ward nursing staff. Finally, the literature was reviewed. RESULTS: All patients were operated on by three different surgeons, on different operating tables/mattresses in the prone position. The common factors were un-paralysed patients having motor/sensory monitoring, mechanical calf pumps and total intravenous anaesthesia. Three patients underwent surgical decompression of their compartments and two were treated expectantly. Three patients had confirmed intra-compartmental changes on MRI consistent with compartment syndrome and one had intra-compartmental pressure monitoring which confirmed the diagnosis. CONCLUSIONS: Previous cases in the literature have related to mal-positioning on the Jackson table or use of the knee-chest position for surgery. This was not the case for our patients; therefore, we suspect an association between overactive muscle stimulation and muscle necrosis. Further experimental studies investigating this link are required.

Intraoperative nerve monitoring during total shoulder arthroplasty surgery.

BACKGROUND: Nerve injury is an acknowledged complication of total shoulder arthroplasty (TSA). Although the incidence of postoperative neurological deficit has been reported to be between 1% and 16%, the true incidence of nerve damage is considered to be higher. The present study aimed to identify the rate of intraoperative nerve injury during total shoulder arthroplasty and to determine potential risk factors. METHODS: A prospective study of nerve conduction in 21 patients who underwent primary or revision TSA was carried out over a 12-month period. Nerve conduction was monitored by measuring intraoperative sensory evoked potentials (SEP). A significant neurophysiological signal change was defined as either a unilateral or bilateral decrease in SEP signal of ≥50%, a latency increase of ≥10% or a change in waveform morphology, not caused by operative or anaesthetic technique. RESULTS: Seven (33%) patients had a SEP signal change. The only significant risk factor identified for signal change was male sex (odds ratio 15.00, 95% confidence interval). The median nerve was the most affected nerve in the operated arm. All but one signal change returned to normal before completion of the operation and no patient had a persisting postoperative clinical neurological deficit. CONCLUSIONS: The incidence of intraoperative nerve damage may be more common than previously reported. However, the loss of SEP signal is reversible and does not correlate with persisting clinical neurological deficits. The median nerve appears to be most at risk. Monitoring SEPs in the operated limb during TSA may be a valuable tool during TSA.

Muscle activation patterns in patients with recurrent shoulder instability.

PURPOSE: The aim of this study is to present muscle patterns observed with the direction of instability in a series of patients presenting with recurrent shoulder instability. MATERIALS AND METHODS: A retrospective review was carried out on shoulder instability cases referred for fine wire dynamic electromyography (DEMG) studies at a specialist upper limb centre between 1981 and 2003. An experienced consultant clinical neurophysiologist performed dual needle insertion into four muscles (pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS)) in shoulders that were suspected to have increased or suppressed activation of muscles that could be contributing to the instability. Raw EMG signals were obtained while subjects performed simple uniplanar movements of the shoulder. The presence or absence of muscle activation was noted and compared to clinical diagnosis and direction of instability. RESULTS: A total of 140 (26.6%) shoulders were referred for fine wire EMG, and 131 studies were completed. Of the shoulders tested, 122 shoulders (93%) were identified as having abnormal patterns and nine had normal patterns. PM was found to be more active in 60% of shoulders presenting with anterior instability. LD was found to be more active in 81% of shoulders with anterior instability and 80% with posterior instability. AD was found to be more active in 22% of shoulders with anterior instability and 18% with posterior instability. IS was found to be inappropriately inactive in only 3% of shoulders with anterior instability but in 25% with posterior instability. Clinical assessment identified 93% of cases suspected to have muscle patterning, but the specificity of the clinical assessment was only correct in 11% of cases. CONCLUSION: The DEMG results suggest that increased activation of LD may play a role in both anterior and posterior shoulder instability; increased activation of PM may play a role in anterior instability.

Prospective blinded comparison of surface versus wire electromyographic analysis of muscle recruitment in shoulder instability.

BACKGROUND: This pilot study assesses level of agreement between surface and fine-wire electromyography (EMG), in order to establish if surface is as reliable as fine wire in the diagnosis and treatment of abnormal muscle patterning in the shoulder. METHOD: Eighteen participants (11 female) with unstable shoulders were recruited after written consent and ethical approval. Anthropometric information and mean skinfold size for triceps, subscapular, biceps and suprailiac sites were obtained. Triple-stud self-adhesive surface electrodes ('Triode'; Thermo Scientific, Physio Med Services, Glossop, Derbyshire, England) were placed over pectoralis major (PM), latissimus dorsi (LD), anterior deltoid (AD) and infraspinatus (IS) at standardized locations. Participants performed five identical uniplanar standard movements (flexion, abduction, external rotation, extension and cross-body adduction). After a 20-minute rest period, a dual-needle technique for fine-wire insertion was performed and the standard movements were repeated. An experienced examiner in each technique reported if muscle activation patterns differed from agreed normal during any movement and were blinded to the other test results. Sensitivity, specificity and Kappa values for level of agreement between methods were calculated for each muscle according to the method of Altman (1991). RESULTS: Fifteen participants were successfully tested. Sensitivity, specificity and Kappa values between techniques for each muscle were PM (57%, 50%, 0.07), LD (38%, 85%, 0.22), AD (0%, 76%, -0.19) and IS (85%, 75%, 0.6). Only IS demonstrated high sensitivity and specificity and a moderate level of agreement between the two techniques. There was no correlation between skinfold size and agreement levels. CONCLUSION: The use of surface EMG may help to classify types of shoulder instability and recognize abnormal muscle patterns. It may allow physiotherapists to direct specific rehabilitation strategies, avoiding strengthening of inappropriate muscles. It has a reasonable degree of confidence to evaluate IS but may have poor sensitivity in detecting abnormal patterns in PM, LD and AD. Further work is required to see if investigator interpretation may have been a factor for the poor level of agreement.

Characterization of radiochromic film scanning techniques used in short-pulse-laser ion acceleration.

Radiochromic film (RCF) is increasingly being used as a detector for proton beams from short-pulse laser-matter interaction experiments using the RCF imaging spectroscope technique. The community has traditionally used inexpensive flatbed scanners to digitize and analyze the data, as opposed to more expensive and time-consuming microdensitometers (MicroDs). Often, the RCF densities in some regions exceed an optical density (OD) of 3. Flatbed scanners are generally limited to a maximum OD of approximately 3. Because of the high exposure density, flatbed scanners may yield data that are not reliable due to light scatter and light diffusion from areas of low density to areas of high density. This happens even when the OD is slightly above 1. We will demonstrate the limitations of using flatbed scanners for this type of radiographic media and characterize them compared to measurements made using a MicroD. A technique for cross characterizing both systems using a diffuse densitometer with a NIST wedge will also be presented.

An investigation into EMG activity in the upper and lower portions of the subscapularis muscle during normal shoulder motion.

BACKGROUND AND PURPOSE: The subscapularis (SSc) muscle is considered to perform a variety of roles during normal shoulder movement. The SSc is innervated by two or more discrete motor nerves and previous studies have indicated some difference in electromyographic (EMG) activity between the upper and lower portions of the muscle. The purpose of the present study was to compare EMG activity between the upper and lower portions of the SSc muscle during voluntary shoulder movements in normal healthy subjects. METHOD: Eight subjects were evaluated. A pair of intramuscular electrodes was inserted into each portion of the muscle. EMG data were recorded during the following movements: sagittal flexion; abduction in the coronal plane; and abduction in the scapular plane. RESULTS: EMG onset of the upper portion of subscapularis occurred significantly earlier compared to the lower portion. Differences were also seen in the level and pattern of activation between the two portions, with upper SSc demonstrating higher levels of activation than the lower portion. CONCLUSIONS: These findings suggest that the upper and lower portions of SSc are differentially active during voluntary shoulder movements.

Does the removal of pectoralis minor impair the function of pectoralis major?

The treatment of long-standing unilateral facial palsy with cross-facial nerve graft and free pectoralis minor muscle flap to the face has been the elective choice for more than 300 patients during the last 20 years at Mount Vernon Hospital in Northwood, United Kingdom. In this study, the authors assessed the residual donor-site morbidity in the chest after the procedure. During the second stage of the operation, the medial and the lateral pectoral nerves are divided at a proximal level from the plexus. Due to the common innervation shared by the two pectoral muscles, a consequent change in pectoralis major muscle function can be expected, but so far no study has been carried out to find out whether or not this occurs. The authors have performed a subjective and an objective study on a voluntary sample of 38 patients previously operated on for facial palsy with pectoralis minor muscle transfer. Cosmetic and functional outcomes were recorded. The subjective evaluation was obtained through a questionnaire. The objective evaluation was obtained through physical examination (inspection and palpation). The following quantitative parameters were determined: thickness of the muscle, arm muscle circumference, power produced at contraction, and muscle fiber activity. Subjectively, six patients (15.8 percent) reported a reduction in the force of the muscle, and 10 patients (26.3 percent) noticed a change in muscular thickness at the site of the operation. Objectively, the results of the electromyogram were almost normal in all of the muscles sampled (17 patients). Occasionally, minor changes from the normal pattern were seen in the lower half of pectoralis major. The dynamometer adduction test showed a significant reduction in the force developed on the operated side when it was the dominant side (p = 0.02), whereas no difference was shown in the group of patients who underwent operations on the nondominant sides (p = 0.18). The pectoral fold and the arm muscle circumference did not show any difference between the side operated on and the nonoperated side. This clinical study confirms that the use of the pectoralis minor muscle as a neurovascular free flap for face reanimation is associated with a low morbidity at the donor site. The authors believe that the medial pectoral nerve has a marginal role in pectoralis major muscle innervation in contrast to the classic anatomic descriptions and some of the positions of the official surgical literature regarding the actual function of this nerve.