Probing the Architecture of Multisubunit Protein Complexes with In-line Disulfide Reduction and Native MS Analysis.

Native mass spectrometry (MS) continues to enjoy growing popularity as a means of providing a wealth of information on noncovalent biopolymer assemblies ranging from composition and binding stoichiometry to characterization of the topology of these assemblies. The latter frequently relies on supplementing MS measurements with limited fragmentation of the noncovalent complexes in the gas phase to identify the pairs of neighboring subunits. While this approach has met with much success in the past two decades, its implementation remains difficult (and the success record relatively modest) within one class of noncovalent assemblies: protein complexes in which at least one binding partner has multiple subunits cross-linked by disulfide bonds. We approach this problem by inducing chemical reduction of disulfide bonds under nondenaturing conditions in solution followed by native MS analysis with online buffer exchange to remove unconsumed reagents that are incompatible with the electrospray ionization process. While this approach works well with systems comprised of thiol-linked subunits that remain stable upon reduction of the disulfide bridges (such as immunoglobulins), chemical reduction frequently gives rise to species that are unstable (prone to aggregation). This problem is circumvented by taking advantage of the recently introduced cross-path reactive chromatography platform (XPRC), which allows the disulfide reduction to be carried out in-line, thereby minimizing the loss of metastable protein subunits and their noncovalent complexes with the binding partners prior to MS analysis. The feasibility of this approach is demonstrated using hemoglobin complexes with haptoglobin 1-1, a glycoprotein consisting of four polypeptide chains cross-linked by disulfide bonds.

Presence of anomalous flexor carpi radialis brevis (FCRB) in Madelung's deformity.

An anomalous flexor carpi radialis brevis (FCRB) muscle was present in four of nine patients undergoing surgery for Madelung's deformity. This disproportionately frequent finding suggests an embryologic dysgenesis of forearm formation rather than a developmental tethering of Vicker's ligament.Level of evidence: IV (case series).

Predictors of True Scaphoid Fractures in Children.

BACKGROUND: The scaphoid is the most commonly fractured carpal bone in children. True scaphoid fractures have proven to be difficult to diagnose, as they may not be apparent on initial imaging. Children with clinical suspicion of a scaphoid fracture may be treated with continued immobilization, even in the absence of radiographic evidence of a fracture. The purpose of this study is to identify predictors of true scaphoid fractures in children to help guide management. METHODS: This study is a retrospective cohort study of children presenting to a tertiary pediatric hospital with hand or wrist injuries. Patients were grouped based on the presence of a true scaphoid fractures (confirmed on imaging) or those with clinical suspicion of a scaphoid fracture alone (no radiographic evidence of fracture). Demographic and clinical characteristics were compared with univariate and multivariate statistics to identify fracture predictors. RESULTS: One hundred and thirty patients were included in the study: 57 in the true scaphoid fracture group and 73 in the clinical scaphoid fracture group. Patients with a true scaphoid fracture were older than those with a clinical scaphoid fracture (median age [interquartile range], 14.2 [13.0-15.4] vs 12.9 [11.9-14.4], P = .01). Men were more likely to sustain a true scaphoid fracture (65.0% vs 35.0%, P = .01). Older age and male sex were shown to be independent predictors of true scaphoid fractures (odds ratio [95% confidence interval], 1.25 [1.03-1.50] and 2.93 [1.39-6.17], respectively). CONCLUSIONS: In the pediatric population, older age and male children may be at increased risk of true scaphoid fractures. This may help guide decisions surrounding further imaging and treatment.

Effect of vertical central plication on vertical deviations.

PURPOSE: To evaluate the surgical effect of the Wright central plication on vertical rectus muscles to correct vertical strabismus. METHODS: In this multicenter, retrospective, observational outcomes study, data were collected from two surgeons in different practice settings (2017-22). All patients who underwent vertical rectus central plication were included; those undergoing any concurrent strabismus surgery for vertical strabismus were excluded. Primary outcome was amount of strabismus correction in prism diopters per vertical rectus central plication. Secondary outcome was to determine factors associated with better or worse surgical outcomes and patient and patient responses. Data were analyzed using descriptive and bivariate statistics. RESULTS: A total of 36 patients were included. Mean age was 60 years. Mean follow-up was 8.4 months. Of the 36 patients, 11 (31%) had idiopathic strabismus, and 7 (19%) had congenital superior oblique palsy. The remainder had a history that included prior ocular surgery, trauma, and Brown syndrome; 16 (44 %) had prior strabismus surgery. Of 31 patients with preoperative diplopia, 23 (74%) had postoperative resolution of diplopia, and 10 of 16 patients with preoperative prisms (63%) no longer required prisms postoperatively. Mean vertical deviation change was 4.7Δ. Subgroup analysis removing patients with congenital superior oblique palsy showed a larger response of 5.5Δ. 78% of patients had a final deviation <5Δ. No complications or induced postoperative diplopia was reported. CONCLUSIONS: In our study cohort, vertical rectus central plication corrected approximately 5Δ (range, 4.5Δ-5.5Δ) of vertical strabismus due to a variety of causes.

Inter-Rater and Intrarater Reliability of Radiographs in the Diagnosis of Pediatric Scaphoid Fractures.

BACKGROUND: Pediatric scaphoid fractures can be challenging to diagnose on plain radiograph. Rates of missed scaphoid fractures can be as high as 30% to 37% on initial imaging and overall sensitivity ranging from 21% to 97%. Few studies, however, have examined the reliability of radiographs in the diagnosis of scaphoid fractures, and none are specific to the pediatric population. Reliability, both between different specialists and for individual raters, may elucidate some of the diagnostic challenges. METHODS: We conducted a 2-iteration survey of pediatric orthopedic surgeons, plastic surgeons, radiologists, and emergency physicians at a tertiary children's hospital. Participants were asked to assess 10 series of pediatric wrist radiographs for evidence of scaphoid fracture. Inter-rater and intrarater reliability was calculated using the intraclass correlation coefficient of 2.1. RESULTS: Forty-two respondents were included in the first iteration analysis. Inter-rater reliability between surgeons (0.66; 95% confidence interval, 0.43-0.87), radiologists (0.76; 0.55-0.92), and emergency physicians (0.65; 0.46-0.86) was "good" to "excellent." Twenty-six respondents participated in the second iteration for intrarater reliability (0.73; 0.67-0.78). Sensitivity (0.75; 0.69-0.81) and specificity (0.78; 0.71-0.83) of wrist radiographs for diagnosing scaphoid fractures were consistent with results in other studies. CONCLUSIONS: Both inter-rater and intrarater reliability for diagnosing pediatric scaphoid fractures on radiographs was good to excellent. No significant difference was found between specialists. Plain radiographs, while useful for obvious scaphoid fractures, are unable to reliably rule out subtle fractures routinely. Our study demonstrates that poor sensitivity stems from the test itself, and not rater variability.