Orthopedic Surgery Residents: How Much Do They Know About Occupational Therapy?

Background Orthopedic hand surgeons rely on occupational therapy (OT) as a crucial part of rehabilitation following injury or surgery. Therefore, orthopedic surgeons should understand the full range of OT services. There is limited prior research on orthopedic residents' understanding of OT in the United States. The main goal of this study is to examine how well orthopedic surgery residents grasp and perceive the role of OT, particularly in hand surgery, as integrated into their educational curriculum. Methods The study included all orthopedic surgery residents from a single institution (Columbia University, New York) during 2022-2023. We obtained permission from the Institutional Review Board, Department Chair, and Program Director to recruit participants. Eligible residents who agreed to participate completed questionnaires regarding their understanding of the role of OT in orthopedic surgery. Results Thirty subjects met the inclusion criteria. The total response rate from the residents was 14/30 (47%). The residents reported a mediocre level of familiarity with OT while also rating 4.5/5 the importance of OT in hand surgery without significant difference between postgraduate year groups. 11/14 residents reported no formal training concerning the role of OT in hand surgery. 12/14 residents reported that it would be helpful to spend time with an occupational therapist. Conclusions This study revealed the lack of confidence residents expressed regarding occupational therapists' roles. All residents recognized the importance of OT in hand surgery and expressed interest in shadowing occupational therapists. Residents of all levels acknowledge the crucial partnership between orthopedists and occupational therapists but lack formal education about the therapist's scope and role.

Extra-Articular Base Fractures of the Proximal Phalanx in Adults: A Systematic Review.

Background: Extra-articular proximal phalanx base fractures are common in adults and can lead to permanent finger stiffness and joint contractures. The purpose of this review is to summarise the evidence for operative and non-operative management of this fracture type. Methods: The MedLine, Embase, PubMed, Scopus and Cochrane Library databases were searched using the following key terms: 'proximal phalanx', 'base', 'fracture', 'repair' and 'fixation'. A total of 2,889 unique records were extracted. All studies with primary data on the management of extra-articular proximal phalangeal base fractures in adults were included for initial review. Results: Eleven studies met inclusion criteria with a total of 441 extra-articular proximal phalanx base fractures. Outcomes were determined by final total active range of motion. 182 extra-articular proximal phalangeal base fractures were treated non-operatively, with excellent or good outcomes attained in 80% of cases. Another 259 extra-articular proximal phalangeal base fractures were treated operatively, including 236 with Kirschner wires (K-wires), 18 with plates, and five with intramedullary screws. Case-level data were available in 186 fractures managed by K-wire fixation, with excellent or good outcomes achieved in 79% of cases. Excellent or good outcomes were achieved in 35% of cases treated by plates, and 80% of five cases treated by intramedullary screw fixation. Three (1.6%) patients managed conservatively required surgery after reduction loss. No patients managed with K-wires required re-operation for reduction loss; tenolysis/capsulotomy was required in 11 (4.5%) cases for stiffness, and pin site infections occurred in eight (3.5%) cases. Complex regional pain syndrome occurred in five cases (28%) of plate fixation. Conclusions: In summary, excellent or good results may be achieved by K-wire pinning or conservative management. Current evidence is limited for plate or intramedullary screw fixation. Prospective trials and outcomes standardisation are needed to improve the evidence base. Level of Evidence: Level III (Therapeutic).

Flexor Tendon Zone II Repair.

Background: Flexor-tendon injury is a historically challenging problem for orthopaedic surgeons. Much research has been dedicated to finding solutions that offer balance in terms of the strength and ease of the repair versus the rate of complications such as adhesions. The number of core sutures, distance from the tendon edge, and use of an epitendinous stitch have been shown to affect repair strength1-4. A number of configurations have been described for the placement of the suture; however, none has been identified as a clear gold standard5. This article will highlight the preferred tendon repair technique of the senior author (R.J.S.), the Strickland repair with a simple running epitendinous stitch. Relevant anatomy, indications, operative technique, and postoperative management will be discussed. Description: The flexor tendon is typically accessed via extension of the laceration that caused the initial injury. After the neurovascular structures and pulleys are assessed, the tendon is cleaned and prepared for repair. A 3-0 braided nylon suture is utilized for the 4-core strand repair and placed in the Strickland fashion. A 5-0 polypropylene suture is then utilized for the simple running epitendinous stitch. Alternatives: Multiple alternative techniques have been described. These vary in the number of core strands, the repair configuration, the suture caliber, and the use of an epitendinous or other suture. Nonoperative treatment is typically reserved for partial flexor-tendon laceration, as complete tendon discontinuity will not heal and requires surgical intervention. Rationale: The 4-core strand configuration has been well established to increase the strength of the repair as compared with 2-core strand configurations, while also being easier to accomplish and with less suture burden than other techniques1. The presently described technique has excellent repair strength and can allow for early active range of motion, which is critical to reduce the risk of postoperative adhesions and stiffness. Expected Outcomes: Excellent outcomes have been demonstrated for primary flexor-tendon repair if performed soon after the injury1,2,6,7. Delayed repair may lead to adhesions and poor tendon healing8. Early postoperative rehabilitation is vital for success9. There are advocates for either active or passive protocols10-12. The protocol at our institution is to begin early active place-and-hold therapy at 3 to 5 days postoperatively, which has been shown in the literature to provide improved finger motion as compared with passive-motion therapy13-16.Important Tips:: The proximal end of the tendon may need to be retrieved via a separate incision if it is not accessible through the flexor-tendon sheath.The proximal end of the tendon may be held in place with a 25-gauge needle in order to best place sutures into both ends of the tendon.The epitendinous suture is run around the back wall before the core sutures are tied down, in order to prevent the tendon and repair from bunching up and becoming overly bulky.The entire A4 pulley and the distal A2 pulley can be divided for exposure if necessary.Up to 2 cm of the flexor-tendon sheath can be divided.If there are concomitant digital nerve injuries, repair these after the tendon, in order to avoid damaging the more delicate nerve repair while manipulating the tendon for repair.The most common major complications following tendon repair are formation of adhesions and rerupture. Acronyms and Abbreviations:: FDS = flexor digitorum superficialisFDP = flexor digitorum profundusMCP = metacarpophalangealPIP = proximal interphalangealDIP = distal interphalangeal.

Anatomic Risks with Overpenetration of the Volar Locking Plates' Proximal Holes.

Background Volar locking plate fixation (VLP) is commonly used to treat distal radius fractures (DRF). Risk of dorsal compartment injury with distal screw hole fixation has been studied; however, the risk with proximal screw hole fixation is not well studied. Purpose The goal of this study was to investigate the risk of dorsal structure injury from the screw holes proximal to the two distal rows. Methods Nine cadaveric forearms were used. After volar distal radius exposure, a long VLP was applied. Kirschner wires were placed through the most proximal holes into the dorsal compartments. The extensor structures penetrated were noted and tagged with hemoclips. The distance from the dorsal cortex to the structures was measured. Results The abductor pollicis longus (APL) and extensor pollicis brevis (EPB) muscle bodies were only penetrated; no tendons were penetrated. Proportion of muscle penetration increased with the more proximal screw holes. EPB was more likely to be penetrated distally and APL proximally; both were injured at holes 2 and 3. The extensors were 2 mm from the dorsal cortex of the radius on average; this did not decrease with compression of the forearm. Conclusions This is the first study to examine the anatomic risk of extensor structure injury with VLP proximal screw hole penetration. No extensor tendons were penetrated by these proximal screw holes; first dorsal compartment muscle bellies may be irritated with overpenetration. Our findings suggest that proximal VLP screws do not need to be downsized if they are not over 2 mm prominent.

Extensor Tendon Injury After Volar Locking Plating for Distal Radius Fractures: A Systematic Review.

Distal radius fractures are common orthopedic injuries. Treatment has varied historically, but volar locking plating currently predominates. Although flexor tendon injury is a well-studied complication of this operation, extensor tendon injury is less well studied. The purpose of this review is to search the literature and present the epidemiology, presentation, and treatment of this complication. The Cochrane, EMBASE, PubMed, and SCOPUS databases were searched for the terms "volar" + "radius" + ("plate" OR "plating") + "extensor." Ninety final studies were included for analysis in this review. The incidence of extensor tendon rupture varies from 0% to 12.5%; the extensor pollicis longus is most commonly ruptured. The presentation and management of extensor tendon injury after injury, intraoperatively, and postoperatively are summarized. Radiographic views are described to detect screw prominence and minimize intraoperative risk. Extensor tendon injury after volar locking plate for distal radius fractures is an uncommon injury with several risk factors including dorsal screw prominence and fracture fragments. Removal of hardware and tendon transfers or reconstruction may be necessary to prevent loss of extensor mechanism.

Ring finger metacarpal fracture iatrogenic rotation using an ulnar gutter splint: A cadaveric study.

STUDY DESIGN: Cohort cadaveric study. INTRODUCTION: Ring finger metacarpal fractures are often treated with ulnar gutter orthoses incorporating the ring and small fingers. Iatrogenic pronation of the distal metacarpal fragment may occur from overzealous orthotic "molding", resulting in a crossover deformity of the ring finger over the small finger. PURPOSE OF THE STUDY: The goal of this cadaveric study is to determine whether including the middle finger in an ulnar gutter orthotic could lessen the chances of iatrogenic ring finger metacarpal fracture rotation. METHODS: Transverse ring finger metacarpal shaft fractures were created in 24 cadaver hands. The ring and small fingers were then placed into an intrinsic plus position, simulating the application of an ulnar gutter orthotic. Weights of 2.5, 5, and 10 pounds were applied to the ring and small fingers to simulate iatrogenic-induced fracture pronation. The amount of rotational displacement at the fracture was measured, and the protocol was repeated, including the middle finger in the intrinsic plus position. Mann-Whitney-Wilcoxon test was used for statistical analysis. RESULTS: There was an increase in distal fragment rotation with increasing weight. Fracture displacement was greater with the 2-finger position than the 3-finger at all weight levels; this reached statistical significance at 10 lbs (2.8 vs 1.8 mm). CONCLUSIONS: Application of an ulnar gutter orthotic including only ring and small fingers can rotate the distal fragment of a ring finger metacarpal shaft fracture such that overlap could occur with the small finger. Including the middle finger in ulnar gutter splints will mitigate against the rotation of the ring finger metacarpal shaft fracture.

Minimum 2-Year Analysis of S2-Alar-Iliac Screw Fixation for Adult Spinal Deformity.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: Determine the rate and risk factors for S2AI screw-related pain after adult spinal deformity surgery with a minimum 2-year follow-up. METHODS: A consecutive 83 spinal deformity patients undergoing surgical treatment between August 2015 and December 2017 with minimum 2-year follow-up for S2AI screw complication and screw-related pain were included. Linear regression was performed on various risk factors and postoperative S2AI screw-related pain. Subset analysis of 53 patients was performed on preoperative and postoperative SRS and ODI scores, operative data, and radiographic data. RESULTS: The overall proportion of S2AI screw-related pain was 9.6%. An S2AI screw complication was identified radiographically in 10.8% of patients; among these, 22.2% experienced S2AI screw-related pain. 3.4% of all patients underwent S2A1 screw removal. The SRS, ODI, sagittal vertical axis (SVA), and coronal alignment scores/measurements improved following treatment in all patients. However, the mean difference for the pre and postoperative SRS function score (1.2 ± 0.5 vs 0.9 ± 0.8) and SVA (4.0 ± 4.9 cm vs 2.1 ± 4.8 cm) were higher for the pain group. CONCLUSIONS: A minimum 2-year analysis of S2AI screw fixation in adult spinal deformity patients showed that 9.6% of patients experienced S2AI screw-related pain and 3.4% of patients had S2A1 screws removed. The size and the number of S2AI screws did not predict postoperative pain, nor were radiographic findings correlated with clinical outcomes. The patient outcome scores, coronal alignment, and SVA improved for all patients, but within the pain group there was an overall larger change in the SVA and SRS function score.

Isolated Radial Nerve Palsy After Glenohumeral Dislocation in a Collegiate Athlete: A Review of the Literature.

Isolated mononeuropathies are uncommon complications after shoulder dislocations. Of these, injuries to the radial nerve are the rarest. Here, we present a case of an isolated radial nerve palsy after a collegiate athlete was hit during a football game and sustained a glenohumeral dislocation. After reduction of the shoulder, he went on to full recovery of motor and sensory function of the radial nerve 1 year after the injury. This case report is further unique given the long-term follow-up in a young, active patient. We review the sparse literature behind the epidemiology and management of these complications.

Biomechanical Evaluation of a Dynamic Stabilization System for the Prevention of Proximal Junctional Failure in Adult Deformity Surgery.

STUDY DESIGN: Biomechanical spine model. Comparison of stress in the implant and the adjacent cranial segment was done with conventional rigid versus dynamic stabilization system (DS) fixation. OBJECTIVE: The aim of this study was to study stress at the proximal end of spinal fixation with a novel DS. SUMMARY OF BACKGROUND DATA: High stress at the implant bone junction may cause proximal junctional failure (PJF) in adult deformity surgery. METHODS: Five life-size spine models were instrumented with pedicle screws and a 5.5-mm Titanium rod from T8-S1. The same models were subsequently instrumented with a similar rod and DS between T8-9 pedicle screws. The spine model was loaded with 25 Nm static load cranial to the proximal fixation in six directions. Strains were measured from the proximal screws. Disc pressure was measured from the proximal instrumented segment (T8-9) and cranial adjacent segment (T7-8). RESULTS: Rigid fixation produced highest strain at T8, followed by T10 then T9. In contrast, DS fixation produced highest strain at T10, followed by T9 then T8. Strain at T8 was significantly less with DS fixation than rigid fixation (P = 0.019). The T10 screw strain was not significantly higher with DS stabilization compared to rigid fixation (P = 0.091). Rigid fixation allowed no load-sharing or pressure rise at T8-9 but an abrupt rise at T7-8. DS system permitted load-sharing and pressure rise in T8-9; the difference compared to rigid fixation was significant in flexion loading (P = 0.04) and similar trend but not significant in extension (P = 0.09). DS system produced a rise in the adjacent segment disc pressure (T7-8), which was smaller than rigid fixation but not significant. CONCLUSION: Long spinal fixation using rigid rods produces maximum stress at the proximal end screw and increases adjacent disc pressure, possibly leading to PJF. Dynamic stabilization at the cranial end segment may prevent PJF by reducing these factors.Level of Evidence: N/A.

Cervical Spinal Fusion in Adult Patients With Rheumatoid Arthritis: A National Analysis of Complications and 90-day Readmissions.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The purpose of this study was to utilize the National Readmission Database to determine the national estimates of complication and 90-day readmission rates associated with cervical spinal fusion in adult patients with rheumatoid arthritis (RA). SUMMARY OF BACKGROUND: RA patients who undergo cervical spine surgery are known to be at high risk for readmissions, which are costly and may not be reimbursed by Medicare. METHODS: The National Readmission Database was queried for adults (>18 years) diagnosed with RA undergoing cervical spine fusion. Patient, operative, and hospital factors were assessed in bivariate analyses. Independent risk factors for readmissions were identified using stepwise multivariate logistic regression. RESULTS: From 2013 to 2014, a total of 5597 RA patients (average age: 61.5 ±â€Š11.2 years, 70.9% female) underwent cervical spine fusion. A total of 691 (12.3%) patients were readmitted within 90 days (). Index inpatient complications included dysphagia (readmitted: 7.9% vs. non-readmitted: 5.1%; P = 0.003), urinary tract infection (UTI) (8.8% vs. 3.7%; P < 0.001), respiratory-related complications (7.6% vs. 3.4%; P < 0.001), and implant-related complications (5.4% vs. 2.7%; P < 0.001). Multivariate logistic regression demonstrated the following as the strongest independent predictors for 90-day readmission: intraoperative bleeding (odds ratio [OR]: 3.6, P = 0.001), inpatient Deep Vein Thrombosis (DVT) (OR 4.1, P = 0.004), and patient discharge against medical advice (OR 33.5, P = 0.001). CONCLUSION: Readmission rates for RA patients undergoing cervical spine surgery are high and most often due to postoperative infection (septicemia, UTI, pneumonia, wound). Potential modifiable factors which may improve outcomes include minimizing intraoperative blood loses, postoperative DVT prophylaxis, and discharge disposition. LEVEL OF EVIDENCE: 3.

Partial Intraoperative Global Alignment and Proportion Scores Do Not Reliably Predict Postoperative Mechanical Failure in Adult Spinal Deformity Surgery.

STUDY DESIGN: Retrospective radiographic review. OBJECTIVES: The Global Alignment and Proportion (GAP) score allows sagittal plane analysis for deformity patients and may be predictive of mechanical complications. This study aims to assess the effectiveness of predicting mechanical failure based on partial intraoperative GAP (iGAP) scores. METHODS: A retrospective radiographic review was performed on 48 deformity patients between July 2015 to January 2017 with a 2-year follow-up. Using the same methodology as the original GAP study, the partial iGAP score was calculated with the sum of the scores for age, relative lumbar lordosis (RLL), and lordosis distribution index (LDI). Therefore, the iGAP score (0-7) was grouped into proportional (0-2), mildly disproportionate (3-5), and severely disproportionate (6-7). Logistic regression was performed to assess the ability of the partial iGAP score to predict postoperative mechanical failure. RESULTS: The mean iGAP for patients with a mechanical failure was 3.54, whereas the iGAP for those without a mechanical failure was 3.46 (P = .90). The overall mechanical failure rate was 27.1%. The mechanical failures included 8 proximal junctional kyphosis, 7 rod fractures, and 1 rod slippage from the distal end of the construct. Logistic regression analysis revealed that the partial iGAP score was not able to predict postoperative mechanical failure (χ2 = 1.4; P = .49). CONCLUSION: The iGAP scores for RLL or LDI did not show any significant correlation to postoperative mechanical failure. Ultimately, the proposed partial iGAP score did not predict postoperative mechanical failure and thus, cannot be used as an intraoperative alignment assessment to avoid postoperative mechanical complications.

Radiographic Evaluation of the Tibial Intramedullary Nail Entry Point.

INTRODUCTION: Tibia fractures are common injuries that can often be effectively treated with intramedullary nail (IMN) fixation. The ideal starting point for IMN reaming and nail placement is well described and regarded as a crucial aspect in the technique. The purpose of this study is to determine the accuracy and precision with which the starting point is established and if this is maintained after nail insertion during fracture fixation. METHODS: Fifty consecutive tibia fractures treated by IMN fixation sized 9 to 13 mm through an infrapatellar or medial parapatellar approach and 50 treated with a suprapatellar approach were evaluated. The starting point for reaming and IMN placement was measured using intraoperative fluoroscopy. Postoperative radiographs were used to determine the center of the IMN after placement. The distance between the measured points and the ideal starting point was measured. RESULTS: Deviation from the ideal entry point on intraoperative fluoroscopy averaged 4.6 ± 4.0 mm medially, 2.9 ± 3.7 mm anteriorly, and 2.7 ± 3.3 mm distally. In 30% of cases, the final IMN position varied from the entry point by greater than one SD in the coronal or sagittal plane. No difference between approaches was appreciated. DISCUSSION: Although the ideal starting point for tibial IMN fixation is known, this is frequently not the starting point accepted in practice. Final position of the IMN is independent of IMN size or approach and is not markedly different than the obtained starting point. LEVEL OF EVIDENCE: Therapeutic level III.

Non-operative Management of Adult Both Bone Forearm Fractures - A Case Report and Literature Review.

INTRODUCTION: Adult both bone forearm fractures (BBFF) are common injuries that are typically treated with operative fixation given their instability. Non-displaced fractures can be theoretically treated non-operatively, but there is no literature demonstrating treatment outcomes of such fractures. CASE REPORT: We present a case of non-displaced BBFF in a 23-year-old Caucasian male adult who was treated with cast immobilization and concomitant ultrasound stimulator use; this patient went on to have solid fracture healing without complication. CONCLUSION: Based on this case, we demonstrate that non-operative management of non-displaced BBFF in adult patients is an option if close follow-up is available. This is significant for the fields of both orthopedic and plastic surgery, as there is little concrete evidence of outcomes of such non-displaced fractures in hand surgery literature.

Metabolic and Endocrine Disorders in Pseudarthrosis.

STUDY DESIGN: Retrospective Cohort. OBJECTIVE: Establish 1-year patient-reported outcomes after spine surgery for symptomatic pseudarthrosis compared with other indications. In the subgroup of pseudarthrosis patients, describe preexisting metabolic and endocrine-related disorders, and identify any new diagnoses or treatments initiated by an endocrine specialist. SUMMARY OF BACKGROUND: Despite surgical advances in recent decades, pseudarthrosis remains among the most common complications and indications for revision after fusion spine surgery. A better understanding of the outcomes after revision surgery for pseudarthrosis and risk factors for pseudarthrosis are needed. METHODS: Using data from our institutional spine registry, we retrospectively reviewed patients undergoing elective spine surgery between October 2010 and November 2016. Patients were stratified by surgical indication (pseudarthrosis vs. not pseudarthrosis), and 1-year outcomes for satisfaction, disability, quality of life, and pain were compared. In a descriptive subgroup analysis of pseudarthrosis patients, we identified preexisting endocrine-related disorders, frequency of endocrinology referral, and any new diagnoses and treatments initiated through the referral. RESULTS: Of 2721 patients included, 169 patients underwent surgery for pseudarthrosis. No significant difference was found in 1-year satisfaction between pseudarthrosis and nonpseudarthrosis groups (77.5% vs. 83.6%, respectively). A preexisting endocrine-related disorder was identified in 82% of pseudarthrosis patients. Endocrinology referral resulted in a new diagnosis or treatment modification in 58 of 59 patients referred. The most common diagnoses identified included osteoporosis, vitamin D deficiency, diabetes, hyperlipidemia, sex-hormone deficiency, and hypothyroidism. The most common treatments initiated through endocrinology were anabolic agents (teriparatide and abaloparatide), calcium, and vitamin D supplementation. CONCLUSIONS: Patients undergoing revision spine surgery for pseudarthrosis had similar 1-year satisfaction rates to other surgical indications. In conjunction with a bone metabolic specialist, our descriptive analysis of endocrine-related disorders among patients with a pseudarthrosis can guide protocols for workup, indications for endocrine referral, and guide prospective studies in this field.

Immediate Use of Uncuffed Tracheostomy after Free Flap Reconstruction of the Head and Neck.

Objective To determine if immediate postoperative uncuffed tracheostomy placement following oral cavity or oropharyngeal head and neck free flap reconstruction is associated with shorter hospital length of stay and higher inpatient decannulation rates without an increase in respiratory complications, as compared with immediate placement of cuffed tracheostomy. Study Design Retrospective cohort. Setting Tertiary referral center. Subjects and Methods Patients were included if they underwent free flap reconstruction for oral cavity or oropharyngeal squamous cell carcinoma and had an intraoperative tracheostomy placed between 2005 and 2016. In 2012, head and neck surgeons changed from routine placement of cuffed to uncuffed tracheostomy tubes immediately after free flap reconstruction. This study compares length of hospital stay, inpatient decannulation rates, and respiratory complications between patients who had cuffed and uncuffed tracheostomies. Analysis of variance and chi-square test were used to examine continuous and categorical variables, respectively. Multivariable regression analyses were performed to determine whether cuff status was independently associated with primary outcomes of length of hospital stay, decannulation, and respiratory complications. Results Of 752 patients who underwent free flap reconstruction, 493 patients met inclusion criteria (cuffed, n = 366; uncuffed, n = 127). Patient variables (ie, age, sex, body mass index, prior chemoradiation) and tumor characteristics (ie, location, stage) did not differ significantly between groups. Adjusted analysis showed that an uncuffed tracheostomy (vs a cuffed tracheostomy) was associated with shorter length of stay (7.7 vs 9.7 days, P < .001) and did not increase the rate of respiratory complications. Conclusion Immediate placement of a uncuffed tracheostomy after oral cavity or oropharyngeal free flap reconstruction is associated with shorter hospital stays without an increase in respiratory complications.

Wireless Optofluidic Systems for Programmable In Vivo Pharmacology and Optogenetics.

In vivo pharmacology and optogenetics hold tremendous promise for dissection of neural circuits, cellular signaling, and manipulating neurophysiological systems in awake, behaving animals. Existing neural interface technologies, such as metal cannulas connected to external drug supplies for pharmacological infusions and tethered fiber optics for optogenetics, are not ideal for minimally invasive, untethered studies on freely behaving animals. Here, we introduce wireless optofluidic neural probes that combine ultrathin, soft microfluidic drug delivery with cellular-scale inorganic light-emitting diode (µ-ILED) arrays. These probes are orders of magnitude smaller than cannulas and allow wireless, programmed spatiotemporal control of fluid delivery and photostimulation. We demonstrate these devices in freely moving animals to modify gene expression, deliver peptide ligands, and provide concurrent photostimulation with antagonist drug delivery to manipulate mesoaccumbens reward-related behavior. The minimally invasive operation of these probes forecasts utility in other organ systems and species, with potential for broad application in biomedical science, engineering, and medicine.

CRH Engagement of the Locus Coeruleus Noradrenergic System Mediates Stress-Induced Anxiety.

The locus coeruleus noradrenergic (LC-NE) system is one of the first systems engaged following a stressful event. While numerous groups have demonstrated that LC-NE neurons are activated by many different stressors, the underlying neural circuitry and the role of this activity in generating stress-induced anxiety has not been elucidated. Using a combination of in vivo chemogenetics, optogenetics, and retrograde tracing, we determine that increased tonic activity of the LC-NE system is necessary and sufficient for stress-induced anxiety and aversion. Selective inhibition of LC-NE neurons during stress prevents subsequent anxiety-like behavior. Exogenously increasing tonic, but not phasic, activity of LC-NE neurons is alone sufficient for anxiety-like and aversive behavior. Furthermore, endogenous corticotropin-releasing hormone(+) (CRH(+)) LC inputs from the amygdala increase tonic LC activity, inducing anxiety-like behaviors. These studies position the LC-NE system as a critical mediator of acute stress-induced anxiety and offer a potential intervention for preventing stress-related affective disorders.