Light-Triggered Reversible Open-Close Motion of a Chiral Molecular Plier to Modulate Guest Binding.

A chiral molecular plier's design, synthesis, characterisation and operations are presented. The molecular plier encompasses three units: a BINOL unit which acts as a pivot as well as a chiral inducer, an azobenzene unit, which acts as a photo-switchable component and two zinc porphyrin, acting as a reporter. E to Z isomerisation persuaded by irradiating with 370 nm light alters the dihedral angle of the pivot BINOL unit, which adjusts the distance between two porphyrin units. The plier can be switched to its initial state by exposure to 456 nm light or heating at 50 °C. NMR, CD and molecular modelling supported the reversible switching and change in dihedral angle and distance between reporter moiety, which was further exploited for binding with several ditopic guests. The longest guest was found to form the strongest complex, R,R-isomer formed a stronger complex than S,S-isomer, Z-isomer of the plier formed stronger complex than the E-isomer with the guest. Moreover, complexation also increased the E-to-Z switching efficiency and decreased the thermal back isomerisation of the azobenzene unit.

Bias in Hand Surgical Randomized Controlled Trials: Systematic Review and Meta-Epidemiological Study.

PURPOSE: Inappropriately reported or conducted studies may decrease the quality of care due to under- or overestimation of the benefits or harms of interventions. Our aim was to evaluate how often hand surgical randomized controlled trials (RCTs) use and report adequate methods to ensure internal validity, and whether inadequate reporting or methods are associated with the magnitude of treatment effect estimates. METHODS: Data Sources were the Cochrane Central Register of Controlled Trials, MEDLINE, and Embase databases until November 2020. We included published RCTs investigating the effects of any surgical intervention in the hand and wrist region. We assessed internal validity using the Cochrane Risk of Bias (RoB) tool for 6 domains: selection, performance, detection, attrition, selective reporting, and "other" bias. We extracted the primary outcome and calculated the effect size for each study. We used mixed-effect meta-regression to assess whether the RoB modified the magnitude of the effects. RESULTS: For 207 assessed trials, the RoB was unclear or high for 72% in selection, 93% in performance, 88% in detection, 25% in attrition, 22% in selective reporting, and 34% in the "other" bias domain. Trials with a high or unclear risk of selection bias yielded 0.28 standardized mean difference (95% confidence interval, 0.02-0.55) larger effect sizes compared to studies with a low risk. Risks of bias for other domains did not modify the intervention effects. The risk for selection bias declined over time: the odds ratio for a high or unclear RoB was 0.90 (95% confidence interval, 0.85-0.95) per additional year of publication CONCLUSIONS: The internal validity and credibility of hand surgical RCTs can be improved by using established methods to achieve true randomization, blinding of the participants and study personnel, publishing the trial protocol and avoiding selective reporting of the outcomes, and reporting the trial as recommended in the Consolidated Standards of Reporting Trials statement. CLINICAL RELEVANCE: Clinicians should be aware that RCTs that do not use or report proper randomization and allocation concealment may overestimate the treatment effects.

Differential Diagnoses of Pediatric Upper Limb Masses.

PURPOSE: Upper limb masses are one of the most common presentations in the outpatient setting. However, there is a paucity of information in the literature regarding the epidemiology of upper-extremity masses in the pediatric population. The aim of this study was to determine the differential diagnoses and clinical characteristics in children aged ≤18 years presenting with upper limb masses. METHODS: A retrospective review of patients aged ≤18 years managed at our institution over a 5-year period was performed. We obtained information on patient demographics, clinical features, radiological investigations, intraoperative features, and histology. We also evaluated the correlation between the clinical and histopathological diagnoses in patients who underwent surgery. RESULTS: There were 141 upper limb masses in our series. The mean age at presentation was 12 years (SD, 5 years). The most common presenting complaints were asymptomatic swelling, pain, and paresthesia. The majority (128; 91%) of tumors were benign; there were 5 locally aggressive tumors and 6 malignant tumors. The dominant hand was involved in 60 patients. Of 140 patients, 43 (31%) patients had surgery. The procedures included incisional biopsy, excisional biopsy, wide resection, and reconstruction. One patient required a below elbow amputation for an osteosarcoma. CONCLUSIONS: Ten percent of cases represented malignant or locally aggressive disease. We have used our observations to develop a clinical algorithm that can assist clinicians in evaluating and managing children and adolescents presenting with upper-extremity masses. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic IV.

Pigmented Nail Lesions: When to Observe, When to Biopsy, When to Widely Excise, and When to Amputate?

Pigmented nail lesions are challenging problems. The differential diagnosis is broad and ranges from common self-limiting conditions, such as subungual hematoma and infection, to potentially fatal conditions, such as subungual melanoma. Clinical assessment and adjuncts, such as dermoscopy and imaging, are usually insufficient to establish a diagnosis, and a nail bed biopsy is often required. However, this is not an innocuous procedure and may result in permanent nail deformity. In addition, subjecting every patient with nail pigmentation to a biopsy will result in an unacceptably high rate of negative test results. Furthermore, histopathologic diagnosis of subungual melanoma remains challenging for several reasons. Once the diagnosis of subungual melanoma is established, the definitive treatment is controversial because the existing guidelines have largely been adapted from those for cutaneous melanoma. This review presents an approach to the diagnosis and management of pigmented subungual lesions and subungual melanoma, in particular, on the basis of the latest available evidence.

A Cadaveric Study on the Utility of the Levator Scapulae Motor Nerve as a Donor for Brachial Plexus Reconstruction.

PURPOSE: The purpose of the study was to evaluate the utility of the levator scapulae motor nerve (LSN) as a donor nerve for brachial plexus nerve transfer. We hypothesized that the LSN could be transferred to the suprascapular nerve (SSN) or long thoracic nerve (LTN) with a reliable tension-free coaptation and appropriate donor-to-recipient axon count ratio. METHODS: Twelve brachial plexus dissections were performed on 6 adult cadavers, bilaterally. We identified the LSN, spinal accessory nerve (SAN), SSN, and LTN. Each nerve was prepared for transfer and nerve redundancies were calculated. Cross-sections of each nerve were examined histologically, and axons counted. We transferred the LSN to target first the SSN and then the LTN, in a tension-free coaptation. For reference, we transferred the distal SAN to target the SSN and LTN and compared transfer parameters. RESULTS: Three cadavers demonstrated 2 LSN branches supplying the levator scapulae. The axon count ratio of donor-to-recipient nerve was 1:4.0 (LSN:SSN) and 1:2.1 (LSN:LTN) for a single LSN branch and 1:3.0 (LSN:SSN) and 1:1.6 (LSN:LTN) when 2 LSN branches were available. Comparatively, the axon count ratio of donor-to-recipient nerve was 1:2.5 and 1:1.3 for the SAN to the SSN and the LTN, respectively. The mean redundancy from the LSN to the SSN and the LTN was 1.7 cm (SD, 3.1 cm) and 2.9 cm (SD, 2.8 cm), and the redundancy from the SAN to the SSN and the LTN was 4.5 (SD, 0.7 cm) and 0.75 cm (SD, 1.0 cm). CONCLUSIONS: These data support the use of the LSN as a potential donor for direct nerve transfer to the SSN and LTN, given its adequate redundancy and size match. CLINICAL RELEVANCE: The LSN should be considered as an alternative nerve donor source for brachial plexus reconstruction, especially in 5-level injuries with scarce donor nerves. If used in lieu of the SAN during primary nerve reconstruction, trapezius tendon transfer for improved external rotation would be enabled.

A Comparison of Casting Versus Splinting for Nonoperative Treatment of Pediatric Phalangeal Neck Fractures.

BACKGROUND: Phalangeal neck fractures account for 13% of pediatric finger fractures. Al Qattan type I (undisplaced) fractures are treated nonoperatively. There is increasing evidence that Type 2 (displaced) fractures achieve remarkable fracture remodeling with nonoperative treatment and patients frequently make a full functional recovery. The options available for nonoperative management of these fractures are either a plaster cast or a removable splint. We hypothesized that there would be no significant difference in radiologic outcome in pediatric phalangeal neck fractures (Types I and II) treated with splint or cast immobilization. METHODS: This is a retrospective study of patients aged 18 and below with phalangeal neck fractures treated nonoperatively from 2008 to 2017. Radiographs were compared at <1 week and >3 weeks after injury. Translation and angulation in coronal and sagittal planes were measured and compared using Student t tests. Baseline variables were compared using χ or Fisher exact tests. RESULTS: There were 47 patients with phalangeal neck fractures treated nonoperatively during the study period. There were 9 type I and 38 type II fractures. The mean age was 10 years with 40 males and 7 females. Fractures occurred in 33 dominant and 14 nondominant hands and involved 29 proximal and 18 middle phalanges. Nineteen children were treated in casts and 28 with removable splints. The mean duration of follow-up was similar between the 2 groups. The most affected phalanx was the proximal phalanx of the small finger and the most common fracture pattern was type IIA. There was no significant difference in clinical and radiologic outcomes between children who were treated in casts and those treated in removable splints. CONCLUSION: There was no difference in the clinical and radiologic outcomes in pediatric phalangeal neck fractures treated with cast or splint immobilization. Splinting has the added benefits of increased comfort and hygiene and we routinely offer splinting as a viable alternative in the nonoperative treatment of Al Qattan type I and type II phalangeal fractures. TYPE OF STUDY/LEVEL OF EVIDENCE: Level III-therapeutic studies.

Emergency Hand and Reconstructive Microsurgery in the COVID-19-Positive Patient.

The case spectrum in hand surgery is one of extremes-purely elective day surgery cases under local anesthesia to mangling limb injuries that require immediate, and frequently, lengthy, surgery. Despite the cancellation of most elective orthopedic and plastic surgical procedures, hand surgeons around the world continue to see a steady stream of limb-threatening cases such as severe trauma and infections that require emergent surgical care. With the increase in community-spread, an increasing number of COVID-19-infected patients may be asymptomatic or have mild, nonspecific or atypical symptoms. Some of them may already have an ongoing, severe infection. The time-sensitive nature of some of these cases means that hand surgeons may need to operate urgently on patients who may be suspected of COVID-19 infections, often before confirmatory test results are available. General guidelines for perioperative care of the COVID-19-positive patient have been published. However, our practices differ from those of general orthopedic and plastic surgery, primarily because of the focus on trauma. This article discusses the perioperative and technical considerations that are essential to manage the COVID-19 patient requiring emergency care, without compromising clinical outcomes and while ensuring the safety of the attending staff.

Parallel Homochiral and Anti-Parallel Heterochiral Hydrogen-Bonding Interfaces in Multi-Helical Abiotic Foldamers.

A hydrogen-bonding interface between helical aromatic oligoamide foldamers has been designed to promote the folding of a helix-turn-helix motif with a head-to-tail arrangement of two helices of opposite handedness. This design complements an earlier helix-turn-helix motif with a head-to-head arrangement of two helices of identical handedness interface. The two motifs were shown to have comparable stability and were combined in a unimolecular tetra-helix fold constituting the largest abiotic tertiary structure to date.

Catch-Release System for Dosing and Recycling Silver(I) Catalyst with Status of Catalytic Activity Reported by Fluorescence.

The silver(I) catch-release system composed of nanoswitch 1 and the anthracene-appended crown ether 2 is infallibly driven by chemical triggers and ion transfer. Any state of the silver(I) translocation is self-reported by a ratiometric emission signature at 472 and 554 nm. In the self-sorted networked state I, the silver(I) ions are tightly shielded inside nanoswitch [Ag(1)]+ ("catch") so that their catalytic activity is zero while emission at 554 nm is maximum. Addition of zinc(II) releases silver(I) from [Ag(1)]+ and generates the catalytically active and fluorescent complex [Ag(2)]+. In this networked state II ("release") both catalytic activity and emission at 472 nm are maximum. Removal of the original trigger regenerates networked state I. ON/OFF control and recycling of catalyst was demonstrated over three in situ cycles.

Supramolecular Control of Azobenzene Switching on Nanoparticles.

The reversible photoisomerization of azobenzene has been utilized to construct a plethora of systems in which optical, electronic, catalytic, and other properties can be controlled by light. However, owing to azobenzene's hydrophobic nature, most of these examples have been realized only in organic solvents, and systems operating in water are relatively scarce. Here, we show that by coadsorbing the inherently hydrophobic azobenzenes with water-solubilizing ligands on the same nanoparticulate platforms, it is possible to render them essentially water-soluble. To this end, we developed a modified nanoparticle functionalization procedure allowing us to precisely fine-tune the amount of azobenzene on the functionalized nanoparticles. Molecular dynamics simulations helped us to identify two distinct supramolecular architectures (depending on the length of the background ligand) on these nanoparticles, which can explain their excellent aqueous solubilities. Azobenzenes adsorbed on these water-soluble nanoparticles exhibit highly reversible photoisomerization upon exposure to UV and visible light. Importantly, the mixed-monolayer approach allowed us to systematically investigate how the background ligand affects the switching properties of azobenzene. We found that the nature of the background ligand has a profound effect on the kinetics of azobenzene switching. For example, a hydroxy-terminated background ligand is capable of accelerating the back-isomerization reaction by more than 6000-fold. These results pave the way toward the development of novel light-responsive nanomaterials operating in aqueous media and, in the long run, in biological environments.

Structural Adaptations of the Primate Flexor Carpi Ulnaris After Tendon Transfer.

PURPOSE: Muscle remodeling occurs after tendon transfer. However, it is not known whether these adaptations are permanent and clinically significant. This study examined the early and late structural adaptations following a standard tendon transfer in a primate model. METHODS: A flexor carpi ulnaris (FCU) to extensor digitorum communis (EDC) transfer was performed in 8 adult monkeys. A sham operation was performed in the contralateral forearm. Four animals were sacrificed at 5 months (early cohort) and 4 at 16 months (late cohort). The transferred FCU, contralateral FCU, and EDC muscles were removed for analysis. Fiber length (FL), physiological cross-sectional area (PCSA), and gross morphology of the transferred FCU were compared with the contralateral EDC and FCU. RESULTS: In the early cohort, the FL of the transferred FCU was longer than the control FCU and similar to the contralateral EDC. The PCSA of the transferred FCU was lower than that of the control FCU but greater than the control EDC. In the late cohort, the difference in FL and PCSA between the transferred FCU and the control FCU persisted. The PCSA of the transferred FCU was similar to that of the control EDC. The bipennate transferred FCU had also undergone gross morphological changes to resemble the multipennate EDC. CONCLUSIONS: This study demonstrates, in a primate model, that the FCU undergoes structural adaptations to resemble the EDC following an FCU-to-EDC transfer. However, these adaptations are incomplete and not sustained over time. CLINICAL RELEVANCE: This study demonstrates that there is muscle plasticity in tendon transfers in a primate model. However, it is important to match potential donor muscles to the recipient during tendon transfer.

Reversible switching of arylazopyrazole within a metal-organic cage.

Arylazopyrazoles represent a new family of molecular photoswitches characterized by a near-quantitative conversion between two states and long thermal half-lives of the metastable state. Here, we investigated the behavior of a model arylazopyrazole in the presence of a self-assembled cage based on Pd-imidazole coordination. Owing to its high water solubility, the cage can solubilize the E isomer of arylazopyrazole, which, by itself, is not soluble in water. NMR spectroscopy and X-ray crystallography have independently demonstrated that each cage can encapsulate two molecules of E-arylazopyrazole. UV-induced switching to the Z isomer was accompanied by the release of one of the two guests from the cage and the formation of a 1:1 cage/Z-arylazopyrazole inclusion complex. DFT calculations suggest that this process involves a dramatic change in the conformation of the cage. Back-isomerization was induced with green light and resulted in the initial 1:2 cage/E-arylazopyrazole complex. This back-isomerization reaction also proceeded in the dark, with a rate significantly higher than in the absence of the cage.

Networking Nanoswitches for ON/OFF Control of Catalysis.

The nanoswitches 1 and 2 are interdependently linked in so-called network states (NetStates). In NetState I, defined by presence of [Cu(1)]+ and 2, the organocatalyst N-methylpyrrolidine catalyzes a conjugate addition. Addition of iron(II) ions as an external chemical trigger to NetState I discharges Cu+ from [Cu(1)]+. The liberated copper(I) ion acts as a second messenger and changes the toggling state at nanoswitch 2. The resulting nanoswitch [Cu(2)]+ captures the catalytically active species from solution and the conjugate addition is turned OFF. Removal of the original trigger reverses the sequence and turns catalysis ON. The ON/OFF catalytic cycle was run three times in situ.

The Effect of Capitate Position on Coronal Plane Wrist Motion After Simulated 4-Corner Arthrodesis.

PURPOSE: The objective of this study was to examine the effect of altering the capitolunate relationship on coronal-plane wrist motion after scaphoidectomy and simulated 4-corner arthrodesis. Two positions of different capitolunate alignments were compared: "anatomic" (unchanged from pre-fusion) and "lunate-covered" (capitate translated to cover the lunate). We hypothesized that wrist resting posture would be altered and radial-ulnar motion would diminish after 4-corner arthrodesis in the lunate-covered position when compared with normal wrists. METHODS: Six human cadaveric limbs were disarticulated at the elbow and mounted on a custom jig. The resting position of the wrist was recorded with no load applied, followed by a load of 44 N applied to the flexor carpi radialis, extensor carpi radialis longus, and extensor carpi radialis brevis tendons to simulate radial deviation and to the flexor carpi ulnaris and extensor carpi ulnaris tendons to simulate ulnar deviation. Scaphoidectomy was performed and 2 methods of 4-corner arthrodesis with different capitolunate coronal alignments were studied in random order. Range of motion was compared using one-way analysis of variance and Bonferroni correction. RESULTS: The "lunate covered" wrist demonstrated significantly greater radial resting posture than that of the preoperative wrist. Under a 44 N load, the lunate-covered position had significantly greater radial motion than the preoperative radial motion. Wrists fused in the "anatomic" position did not differ significantly from the preoperative wrists in posture or range of motion. CONCLUSIONS: In this cadaveric model, complete covering of the capitate head by the lunate placed the wrist in increased radial deviation compared with the anatomic posture. Changes induced in the resting tension of the extrinsic wrist ligaments serve as a reasonable explanation for the increased radial posture and motion. In a clinical setting, these changes may affect postoperative wrist posture and function. CLINICAL RELEVANCE: Maintaining anatomic lunate position leads to preservation of greater wrist motion and anatomic alignment in a patient undergoing 4-corner arthrodesis.

A Metalloregulated Four-State Nanoswitch Controls Two-Step Sequential Catalysis in an Eleven-Component System.

The nanomechanical switch 1 with its three orthogonal binding motifs-the zinc(II) porphyrin, azaterpyridine, and shielded phenanthroline binding station-is quantitatively and reversibly toggled back and forth between four different switching states by means of addition and removal of appropriate metal-ion inputs. Two of the four switching stages are able to initiate catalytic transformations (ON1, ON2), while the two others shut down any reaction (OFF1, OFF2). Thus, in a cyclic four-state switching process the sequential transformation A+B+C→AB+C→ABC can be controlled, which proceeds stepwise along the switching states OFF1→ON1 (click reaction: A+B→AB)→OFF2→ON2 (Michael addition: AB+C→ABC)→OFF1. Two consecutive cycles of the sequential catalysis were realized without loss in activity in a reaction system with eleven different components.

Redox-dependent self-sorting toggles a rotary nanoswitch.

The pyridine-pyrimidine (py-pym) arm as the moving part of the two-state nanomechanical rotary switch [Cu(1)](+) is toggled reversibly between two stations using one-electron oxidation/reduction. In state I, the arm is attached via Cu(+) complexation to a sterically encumbered phenanthroline and in state II to a zinc porphyrin station. Toggling is realised by charging and discharging an external input signal, the ferrocene-appended diimine ligand 2. Addition of 2 leads to formation of the intermolecular complex [Cu(1)(2)](+) paralleled by a move of the py-pym arm to the zinc porphyrin station. Upon oxidation at the ferrocenyl unit, 2(+) detaches from [Cu(1)(2)](2+) so that [Cu(1)](+) is formed in state I. Switching was ascertained by NMR, UV-Vis spectroscopy and cyclic voltammetry.

Soft tissue complications of dorsal versus volar plating for ulnar shortening osteotomy.

PURPOSE: To compare the results and complications of fixed-angle dorsal locking plate fixation for ulnar shortening osteotomy (USO) with the conventional technique of volar plating. METHODS: We performed a retrospective review of 32 patients undergoing USO on 34 wrists and compared the outcomes of 16 consecutive cases with dorsal 2.4/2.7-mm fixed-angle plating and 18 consecutive cases with volar 3.5-mm plating. A minimum of 12 months' follow-up was used to assess outcomes. Primary outcomes were painful hardware and removal of symptomatic implants. Secondary outcomes were pain, Patient-Rated Wrist Evaluation, range of motion, time to union, grip strength, and complications. RESULTS: There were no significant differences in Patient-Rated Wrist Evaluation, pain score, range of motion, or time to union. Relative grip strength compared with the contralateral upper extremity in the dorsal group was higher than the volar group. After adjusting for hand dominance, dorsal plating was significantly associated with higher relative grip strength. There were 2 complications in the dorsal group, including one case with painful hardware. This was significantly lower than in the volar group, which had 10 complications including 2 nonunions and 6 cases of hardware-related soft tissue irritation. CONCLUSIONS: Both volar and dorsal plating techniques for USO yielded good functional outcomes. There was a higher incidence of painful hardware requiring removal of implants in the volar group. Based on these findings, we advocate dorsal plate position using a smaller fixed-angle plate for USO in ulnar impaction syndrome. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic III.

Thoracic outlet syndrome caused by synostosis of the first and second thoracic ribs: 2 case reports and review of the literature.

We present 2 cases of combined arterial and neurogenic thoracic outlet syndrome triggered by trauma in patients with congenital synostoses of the first and second ribs. These patients were successfully treated with supraclavicular resection of the first and second ribs and scalenectomy. We review these cases and the associated literature on thoracic outlet syndrome and rib synostosis.

Surgical treatment of osteochondroma of the proximal humerus: radiographic and early clinical results.

BACKGROUND: Symptomatic osteochondromas (OCEs) of the proximal humerus present a number of challenges, based upon their location and proximity to neurovascular structures. The purpose of this investigation was to evaluate the characteristics of these lesions and report the early results of surgical excision in children. METHODS: This is a retrospective case series of 31 pediatric patients with proximal humeral OCE treated with surgical excision. Radiographs and medical records were reviewed to evaluate tumor characteristics, treatment, and clinical results. The mean patient age was 13 (SD, 4) years, and the median follow-up was 11 months (range, 1 to 78 mo). RESULTS: From 1995 to 2009, 31 patients with proximal humeral OCE underwent surgical excision. Indications for surgery included pain in 25 (81%) and limited range of motion in 8 (26%). The OCE were most commonly posterolateral (23%) and posteromedial (16%). The site of OCE significantly influenced the extent of mass excision. OCEs located anteriorly, laterally, and posterolaterally had an average of 92% of mass excised (range, 69% to 100%), whereas those located posteromedially had an average of 68% of mass removed (range, 30% to 82%; P=0.02). Two patients (6%) had persistent postoperative pain, and 2 had recurrence. The deltopectoral approach was most commonly utilized (61%). For the posteromedial lesions, the direct medial approach led to more complete excision (79% vs. 51%). There were no neurovascular complications. CONCLUSIONS: Surgical excision of proximal humerus OCE led to favorable results, though persistent postoperative pain was seen with inadequate excision. Despite risks of neurovascular injury, a direct medial approach should be considered for posteromedial lesions. LEVEL OF EVIDENCE: Level IV-retrospective study.