Falls by subjects riding a ski lift while in transit are rare but can cause significant injury. Falls can occur at variable heights and can occur to small children through to adults of both genders. The current study was designed to investigate the mechanics associated with falls to elucidate this phenomenon. Five crash dummies served as surrogates for children (3-, 6-, and 10-year-old) and adults (5th percentile female and 50th percentile male). The subjects were seated in a simulated ski lift chair with a detailed seating procedure. The shorter length of the 3- and 6-year-old surrogates' thighs was associated with slouched posture while the remaining surrogates sat in an upright fashion. All subjects were fit with winter clothing, skis, boots, helmet, and goggles. The ski lift chair was slowly tilted forward to represent wind gusts, ski lift cable catenary, or activation of the lift emergency stop. As a worst-case scenario, a restraint bar was not used since field data suggests poor usage rates. The seat was covered with three different frictional interfaces to represent different seat designs and environmental conditions. The results showed that the 10-year-old and fifth percentile female surrogates required the greatest tilt angles to initiate a fall with increasing friction requiring greater tilt angles. The remaining surrogates exhibited significantly lower tilt angles with no significant effect observed for the different frictional interfaces. These data suggest that subject size and frictional interface create variable effects. As such, uniform use of restraint bars and footrests, where available, is recommended.

Modulator agents that restore cystic fibrosis transmembrane conductance regulator (CFTR) function have revolutionized outcomes in cystic fibrosis, an incurable multisystem disease. Barriers exist to modulator use, making local CFTR gene and cell therapies attractive, especially in the respiratory tract. We used CRISPR to gene-correct CFTR in upper airway basal stem cells (UABCs) and show durable local engraftment into recipient murine respiratory epithelium. Interestingly, the human cells recapitulate the in vivo organization and differentiation of human sinus epithelium, with little expansion or contraction of the engrafted population over time, while retaining expression of the CFTR transgene. Our results indicate that human airway stem cell transplantation with locoregional restoration of CFTR function is a feasible approach for treating CF and potentially other diseases of the respiratory tract.

Cochlear melanocytes are intermediate cells in the stria vascularis that generate endocochlear potentials required for auditory function. Human PAX3 mutations cause Waardenburg syndrome and abnormalities of skin and retinal melanocytes, manifested as congenital hearing loss (~ 70%) and hypopigmentation of skin, hair and eyes. However, the underlying mechanism of hearing loss remains unclear. Cochlear melanocytes in the stria vascularis originated from Pax3-traced melanoblasts and Plp1-traced Schwann cell precursors, both of which derive from neural crest cells. Here, using a Pax3-Cre knock-in mouse that allows lineage tracing of Pax3-expressing cells and disruption of Pax3, we found that Pax3 deficiency causes foreshortened cochlea, malformed vestibular apparatus, and neural tube defects. Lineage tracing and in situ hybridization show that Pax3+ derivatives contribute to S100+, Kir4.1+ and Dct+ melanocytes (intermediate cells) in the developing stria vascularis, all of which are significantly diminished in Pax3 mutant animals. Taken together, these results suggest that Pax3 is required for the development of neural crest cell-derived cochlear melanocytes, whose absence may contribute to congenital hearing loss of Waardenburg syndrome in humans.

A validated femoral neck fracture model stabilized with three inverted cannulated screws was used to consider different intraoperative scenarios when the inferior screw hole is inadvertently started too inferiorly. These scenarios were to: (1) abandon the misplaced inferior screw hole and restart this hole more proximally, or (2) accept the mispositioned placement of the inferior screw and insert the remaining superior screws parallel or convergent to the inferior screw. Utilizing the second option and accepting the errant hole was associated with the greatest interfragmentary motion and stresses in the bone and hardware. In contrast, the first option created an improved mechanical environment for healing.

Mammalian inner ear hair cell loss leads to permanent hearing and balance dysfunction. In contrast to the cochlea, vestibular hair cells of the murine utricle have some regenerative capacity. Whether human utricular hair cells regenerate in vivo remains unknown. Here we procured live, mature utricles from organ donors and vestibular schwannoma patients, and present a validated single-cell transcriptomic atlas at unprecedented resolution. We describe markers of 13 sensory and non-sensory cell types, with partial overlap and correlation between transcriptomes of human and mouse hair cells and supporting cells. We further uncover transcriptomes unique to hair cell precursors, which are unexpectedly 14-fold more abundant in vestibular schwannoma utricles, demonstrating the existence of ongoing regeneration in humans. Lastly, supporting cell-to-hair cell trajectory analysis revealed 5 distinct patterns of dynamic gene expression and associated pathways, including Wnt and IGF-1 signaling. Our dataset constitutes a foundational resource, accessible via a web-based interface, serving to advance knowledge of the normal and diseased human inner ear.

Background Osteoarthritis (OA) is one of the leading causes of hip pain in the United States, with over half a million total hip arthroplasties (THA) performed every year. In hip OA radiographic joint space narrowing in the superior region of the hip is typical, with narrowing in the medial region less frequently reported. As this form of OA is relatively rare, patient characteristics and prognosis are poorly understood. The goal of the current study is to provide a more complete description of medial pole OA patients. Methods The current study performed a retrospective review of prospectively collected cases of medial joint space narrowing identified by a single surgeon between 2015 and 2023. Patient characteristics, x-ray measures, and patient reported outcome measures were recorded before and after surgery (if performed). Results The total number of patients in this study was 54, with 22 having bilateral radiographic signs of OA and average pain at first presentation of 6.85, with 10 representing maximal pain. The cases were more frequently in women (71%) and most demonstrated an “eyebrow” sign on anterior-posterior (AP) x-rays, with all cases Kellgren-Lawrence ≥3 exhibiting the “eyebrow” feature. Center edge angle, femoral neck angle, Tonnis Angle, and abduction lever arm ratio all fell within previously published ranges. A new x-ray view (Flint View) showed posterior joint space narrowing. Conclusions Typically medial pole cases occurred in women with a characteristic radiographic presence of an “eyebrow sign”. Patient joint geometry measures and pain scores fall within typical ranges for hip OA patients.

In cases of cervical facet dislocations, traction is typically delivered in the acute setting with tongs attached to the skull via two pins. Although the pins are recommended to be inserted symmetrically in a neutral loading position, erroneous asymmetric pin placement has been documented in case reports, but its biomechanical implications are unknown. The current study utilized a human surrogate to evaluate the influence of asymmetrically placed pins in the axial or frontal planes. In addition, asymmetry of the cable that delivers the traction force to the tongs was also investigated. In the majority of the pin configuration experiments, pin asymmetry did not significantly affect cervical spine loading. One exception was if one pin was placed 1 cm anterior to neutral and the contralateral was in the neutral position. This configuration resulted in a significant increase in the cervical extension moment, which should typically be avoided because it can hinder reduction. (Journal of Surgical Orthopaedic Advances 33(4):233-239, 2024).

Recent advances in fate mapping and single-cell technologies have revealed how the dynamics and function of tissue-resident macrophages are shaped by their environment. However, macrophages in sensory organs such as the cochlea where the central nervous system and peripheral nervous system meet remain understudied. Combining single-cell transcriptomics, fate mapping, and parabiosis experiments, we show that five types of myeloid cells including three tissue-resident macrophage subpopulations, coexist in the mouse cochlea. The three macrophage subsets showed different potential functions in relationship with their specific topography across cochlear compartments. Further analysis revealed that they were partially derived from yolk sac progenitors during development, while in adulthood, most cochlear macrophages were long-term resident. Finally, we showed that cochlear macrophage morphology and density changed during aging. Our findings show that cochlea is a microenvironment with a unique heterogeneity of macrophages in terms of gene expression, spatial distribution, ontogeny, and function.

Adeno-associated virus (AAV)-mediated gene transfer has shown promise in rescuing mouse models of genetic hearing loss, but how viral capsid and promoter selection affects efficacy is poorly characterized. Here, we tested combinations of AAVs and promoters to deliver Tmprss3, mutations in which are associated with hearing loss in humans. Tmprss3tm1/tm1 mice display severe cochlear hair cell degeneration, loss of auditory brainstem responses, and delayed loss of spiral ganglion neurons. Under the ubiquitous CAG promoter and AAV-KP1 capsid, Tmprss3 overexpression caused striking cytotoxicity in vitro and in vivo and failed to rescue degeneration or dysfunction of the Tmprss3tm1/tm1 cochlea. Reducing the dosage or using AAV-DJ-CAG-Tmprss3 diminished cytotoxicity without rescue of the Tmprss3tm1/tm1 cochlea. Finally, the combination of AAV-KP1 capsid and the EF1α promoter prevented cytotoxicity and reduced hair cell degeneration, loss of spiral ganglion neurons, and improved hearing thresholds in Tmprss3tm1/tm1 mice. Together, our study illustrates toxicity of exogenous genes and factors governing rescue efficiency, and suggests that cochlear gene therapy likely requires precisely targeted transgene expression.

Background:Knee injuries induce swelling and resolution of swelling may be a useful factor in identifying states of healing and time to return to sports activities. Recent work has suggested that bioimpedance can provide an objective measure of swelling following total knee arthroplasty (TKA) and therefore may also provide guidance for clinical decision-making following knee injury. This study measures knee bioimpedance in young, active people to help define baseline variability and factors that influence limb to limb differences. Methods:Bioimpedance was measured via sensors placed at the foot/ankle and thigh, in positions similar to those suggested for monitoring post-TKA swelling. Initial tests were performed to verify method repeatability, then bioimpedance was measured in a convenience sample of 78 subjects (median age 21yrs). The influence of age, BMI, thigh circumference, and knee function (KOOS-JR) on the impedance measures and difference in impedance between the subject's knees were examined using a generalized multivariable linear regression. Results:The repeatability study measurements were highly consistent with a COV of 1.5% for resistance and an ICC of 97.9%. Women exhibited significantly larger dominant limb impedance and larger limb to limb difference in impedance than men. Regression analysis indicated that subject sex and BMI significantly influenced bioimpedance but joint score and age did not. The limb to limb differences in impedance were small on average (<5%), with larger magnitudes of difference associated with female sex, lower knee function scores, and larger limb to limb differences in thigh circumference. Conclusion:Bioimpedance measurements across right and left knees of healthy young people were similar, supporting use of bioimpedance measures from a patient's uninjured knee as a benchmark to monitor healing of a contralateral injured knee. Future work should focus on understanding how knee function scores and bioimpedance are related, and further explore how sex and side to side anatomic differences impact the measurement. Level of Evidence: IV.

Cochlear melanocytes are intermediate cells in the stria vascularis that generate endocochlear potentials required for auditory function. Human PAX3 mutations cause Waardenburg syndrome and abnormalities of melanocytes, manifested as congenital hearing loss and hypopigmentation of skin, hair and eyes. However, the underlying mechanism of hearing loss remains unclear. During development, cochlear melanocytes in the stria vascularis are dually derived from Pax3-Cre+ melanoblasts migrating from neuroepithelial cells including neural crest cells and Plp1+ Schwann cell precursors originated from also neural crest cells, differentiating in a basal-apical manner. Here, using a Pax3-Cre mouse line, we found that Pax3 deficiency causes foreshortened cochlea, malformed vestibular apparatus, and neural tube defects. Lineage tracing and in situ hybridization show that Pax3-Cre derivatives contribute to S100+ , Kir4.1+ and Dct+ melanocytes (intermediate cells) in the developing stria vascularis, all significantly diminished in Pax3 mutant animals. Taken together, these results suggest that Pax3 is required for the development of neural crest cell-derived cochlear melanocytes, whose absence may contribute to congenital hearing loss of Waardenburg syndrome in human.

The mammalian cochlea contains three rows of outer hair cells (OHCs) that amplify the basilar membrane traveling wave with high gain and exquisite tuning. The pattern of OHC loss caused by typical methods of producing hearing loss in animal models (noise, ototoxic exposure, or aging) is variable and not consistent along the length of the cochlea. Thus, it is difficult to use these approaches to understand how forces from multiple OHCs summate to create normal cochlear amplification. Here, we selectively removed the third row of OHCs and Deiters' cells in adult mice and measured cochlear amplification. In the mature cochlear epithelia, expression of the Wnt target gene Lgr5 is restricted to the third row of Deiters' cells, the supporting cells directly underneath the OHCs. Diphtheria toxin administration to Lgr5DTR-EGFP/+ mice selectively ablated the third row of Deiters' cells and the third row of OHCs. Basilar membrane vibration in vivo demonstrated disproportionately lower reduction in cochlear amplification by about 13.5 dB. On a linear scale, this means that the 33% reduction in OHC number led to a 79% reduction in gain. Thus, these experimental data describe the impact of reducing the force of cochlear amplification by a specific amount. Furthermore, these data argue that because OHC forces progressively and sequentially amplify the traveling wave as it travels to its peak, the loss of even a relatively small number of OHCs, when evenly distributed longitudinally, will cause a substantial reduction in cochlear amplification.NEW & NOTEWORTHY Normal cochlear physiology involves force production from three rows of outer hair cells to amplify and tune the traveling wave. Here, we used a genetic approach to target and ablate the third row of outer hair cells in the mouse cochlea and found it reduced cochlear amplification by 79%. This means that the loss of even a relatively small number of OHCs, when evenly distributed, causes a substantial reduction in cochlear amplification.

There is an increasing trend to provide cochlear implants for people with useful residual hearing, typically in the low frequency range (<2 kHz). These recipients typically use both electrical stimulation from their implant and acoustic stimulation that has been amplified with a hearing aid to access their residual hearing, so called electro-acoustic stimulation (EAS). However, a significant problem is the loss of residual hearing following implantation that can occur immediately following surgery or delayed over many months. One potential cause of the loss of residual hearing is the over stimulation of remaining hair cells due to the combination of an amplified acoustic input and direct electrical activation. This paper aims to test this hypothesis. Here, we have used a neonatal aminoglycoside-induced partial hearing cat model that resulted in a high frequency hearing loss (>4 kHz). Two separate cohorts of animals were implanted and received unilateral chronic electrical stimulation using clinical stimulators and speech processors over 5 months. To simulate potential over stimulation via a hearing aid, one cohort of animals were also exposed to an enhanced acoustic environment consisting of 80 dB SPL 4-talker babble presented 14 h per day. Hearing thresholds for both stimulated and unstimulated ears were measured throughout the implantation period. Cochleae were collected for histology to measure spiral ganglion neuron survival, hair cell survival and tissue response to chronic implantation and electrical stimulation. Consistent with clinical observations, cochlear implantation and stimulation resulted in an increase in threshold across the population. There was no significant effect of the enhanced acoustic environment on auditory thresholds or histological measures (hair cell survival, neuronal survival) of hearing, indicating that hair cell overstimulation was not a significant driver of loss of residual hearing.

Background: Motor vehicle crashes represent a significant cause of mortality and morbidity for young children. Safely restraining a child is typically more complicated for special cases such as children treated with a hip spica cast. In the current study, hip spica casts typical for treatment of a femoral fracture were applied to a crash dummy representing the size and weight of a 1-year-old child. This spica casted dummy was used to study the performance of 4 rear-facing car seats in a series of simulated frontal impacts. Methods: The restrained, rear-facing dummy was subjected to a frontal crash test at 30 mph (48 kph) per federal guidelines. Two of the tested car seats were specifically designed for transporting children with hip spica casts, while the other 2 were conventional seats capable of accommodating the cast. All seats were installed per the manufacturer’s instructions. As a control, tests were performed without a cast using the conventional/standard seats. Results: The lowest overall loading of the dummy’s head, neck, and chest occurred during tests with the standard seats. While it was easier to seat the casted child in the spica-specific seats, these designs led to greater loading on the dummy’s body. In a spica-specific seat, the chest acceleration values exceeded the federal limit in a test where the seat was installed in a reclined orientation that was within the manufacturer’s described positioning. Conclusions: Spica-specific seats more easily accommodate the cast, but conventional seats can provide similar levels of protection in a crash. As cast and seat designs continue to evolve, hospitals might consider having a range of seats available for patient use. It is important to help caregivers make informed decisions on how and when to transport children with hip spica casts.

Cochlear supporting cells (SCs) are glia-like cells critical for hearing function. In the neonatal cochlea, the greater epithelial ridge (GER) is a mitotically quiescent and transient organ, which has been shown to nonmitotically regenerate SCs. Here, we ablated Lgr5 + SCs using Lgr5-DTR mice and found mitotic regeneration of SCs by GER cells in vivo. With lineage tracing, we show that the GER houses progenitor cells that robustly divide and migrate into the organ of Corti to replenish ablated SCs. Regenerated SCs display coordinated calcium transients, markers of the SC subtype inner phalangeal cells, and survive in the mature cochlea. Via RiboTag, RNA-sequencing, and gene clustering algorithms, we reveal 11 distinct gene clusters comprising markers of the quiescent and damaged GER, and damage-responsive genes driving cell migration and mitotic regeneration. Together, our study characterizes GER cells as mitotic progenitors with regenerative potential and unveils their quiescent and damaged translatomes.

The G protein-coupled receptor (GPR) family critically regulates development and homeostasis of multiple organs. As a member of the GPR adhesion family, Gpr125 (Adgra3) modulates Wnt/PCP signaling and convergent extension in developing zebrafish, but whether it is essential for cochlear development in mammals is unknown. Here, we examined the Gpr125lacZ/+ knock-in mice and show that Gpr125 is dynamically expressed in the developing and mature cochleae. From embryonic day (E) 15.5 to postnatal day (P) 30, Gpr125-β-Gal is consistently expressed in the lesser epithelial ridge and its presumed progenies, the supporting cell subtypes Claudius cells and Hensen’s cells. In contrast, Gpr125-β-Gal is expressed transiently in outer hair cells, epithelial cells in the lateral cochlear wall, interdental cells, and spiral ganglion neurons in the late embryonic and early postnatal cochlea. In situ hybridization for Gpr125 mRNA confirmed Gpr125 expression and validated loss of expression in Gpr125lacZ/lacZ cochleae. Lastly, Gpr125lacZ/+ and Gpr125lacZ/lacZ cochleae displayed no detectable loss or disorganization of either sensory or non-sensory cells in the embryonic and postnatal ages and exhibited normal auditory physiology. Together, our study reveals that Gpr125 is dynamically expressed in multiple cell types in the developing and mature cochlea and is dispensable for cochlear development and hearing.

CELL BIOLOGY Correction for “Dissociating antibacterial from ototoxic effects of gentamicin C-subtypes,” by Mary E. O’Sullivan, Yohan Song, Robert Greenhouse, Randy Lin, Adela Perez, Patrick J. Atkinson, Jacob P. MacDonald, Zehra Siddiqui, Dennis Lagasca, Kate Comstock, Markus E. Huth, Alan G. Cheng, and Anthony J. Ricci, which was first published December 7, 2020; 10.1073/ pnas.2013065117 (Proc. Natl. Acad. Sci. U.S.A. 117, 32423–32432). The authors note that reference 14 is retracted and therefore should be removed from the references list. In addition, the authors note that there is an error in the “labeling of the chemical structures of gentamicin C-subtypes.” On page 32424, right column, second full paragraph, line 1, “The C-subtypes of gentamicin differ in the C5′ and C6′ positions on ring I (Fig. 1 A and B).” should instead appear as “The C-subtypes of gentamicin differ in the C6′ position on ring I (Fig. 1 A and B).” Due to the same error, Figs. 1 and 3 appeared incorrectly. The corrected figures and their legends appear below. Lastly, the authors note that Fig. S2 in the SI Appendix appeared incorrectly because the “labeling of rings I and III was reversed.” The online version has been updated to include the updated reference list, the corrected text described above, the corrected Figs. 1 and 3, and the corrected SI Appendix.

Hearing protection devices reduce cast-saw noise. It would be helpful to identify the devices that are both effective and economical. Prior studies have shown that expensive noise-reduction headphones significantly reduced the anxiety associated with cast removal with a powered oscillating saw. The cost of such headphones, however, is a drawback for some practices and hospitals. It would be helpful to determine whether lower cost ear protection can provide effective cast-saw noise reduction. In addition, it is unclear whether the noise reduction ratings (NRRs), the average sound-level reduction provided by a hearing protection device in a laboratory test, provided by manufacturers accurately characterize the effectiveness for reducing cast-saw noise. Note that noise-cancelling devices do not carry an NRR because they are not designed as hearing protectors. Five ear protection devices with different NNRs were tested. The devices varied greatly in cost and included earplugs, low-cost earmuffs, and noise-cancelling headphones. To standardize the evaluation, each device was fitted to an acoustic mannequin with high-fidelity ear microphones while a fiberglass spica cast was cut. An additional test was run without hearing protection as a control. The low-cost devices significantly reduced the saw noise, with the exception of earplugs, which had highly variable performance. The noise reduction was similar between low-cost earmuffs and the high-cost earphones when the noise-cancelling feature was not active. Active noise cancelling provided further reductions in the noise level. Patients can experience high anxiety during cast removal. The current study shows that low-cost earmuffs significantly reduce cast-saw noise. Patient care settings may be more likely to offer hearing protection that is one twenty-fifth the cost of noise-cancelling headphones. An NRR appears to be a reliable guide for selecting hearing protection that reduces cast-saw noise.

Surgical suits provide protection to orthopedic surgeons, but the suits and fan noise may interfere with communication between operative team members. The goal of this study was to quantify the fan sound and effect of the suit, fan, and N95 mask. Sound levels were measured using a specialized manikin and evaluated using preferred speech interference levels (PSILs), noise criterion (NC) ratings, and comparison with speech sound levels from the literature. Additionally, sound blocking due to the surgical suit was measured and combined effects of the fan and suit were described using a signal to noise ratio (SNR). The noise with the fan at medium and high speed was louder than average speech and the PSILs at these speeds were significantly higher than with the fan off. The fan NC rating of 50 to 60 exceeded the recommended range of 25 to 30 for operating rooms. The N95 mask, space suit, and distance between speaker and receiver all reduced the sound signal at the receiver's ear, with the worst case being full personal protective equipment on both and speaker distanced from receiver. The estimated SNR for the suit and fan system was negative for many frequency bands used in speech, indicating more noise than signal. Multiple measures indicated that the fan noises were at levels associated with speech interference. This noise combined with sound blocking provided by the suit produced SNRs commonly associated with noisy to very noisy environments. This study suggests the combined effects of the suit, fan, and distance may negatively impact operating room communication. [Orthopedics. 2021;44(4):208-214.].

Objective: There is little data defining safe transport protocols for spica-casted children. A single earlier study demonstrated the presence of a body cast alters kinematics and injury metrics during simulated side-impact crashes. Since then, the National Highway Transportation Safety Administration (NHTSA) proposed a new side-impact test protocol for evaluating child restraints. This test is more severe than the earlier tests, as it simulates an impact with a door intruding into the occupant space. As no currently available child restraint system (CRS) able to accommodate a spica-casted child has been evaluated using these updated testing criteria, the objective of this study was to evaluate current restraint options in simulated side-impact collisions using an anthropomorphic test device (ATD) modeled after a 3-year-old.Methods: Four commercially available CRSs able to accommodate a spica-casted Q3s side-impact ATD were selected for testing. Side-impact testing was performed using casted and uncasted ATDs in compliance with the NHTSA proposed side-impact test. High-speed photography and ATD instrumentation were used to measure selected injury criteria.Results: HIC15 values were highest in CRSs with less robust side wings, such as the Merritt WallenburgTM (HIC15 = 1,373), which allow for the occupant to interact with the intruding door panel. Head contact with the door panel was found to correspond with high resultant neck peak force. Pelvic acceleration magnitudes were greatest for the uncasted tests. Casted tests with a CRS that included an armrest were associated with greater torso rotation in the frontal plane with the left shoulder moving toward the door panel.Conclusions: The presence of a spica cast alters injury metrics in side-impact testing. Spica specific child safety seats are not yet optimized for side-impact with door intrusion. This is due to a lack of adequate side cushion wings, which may place both casted and uncasted occupants at increased likelihood for injury through head contact with an intruding door. Additional work is needed to improve the safety of CRSs for both casted and uncasted children in side-impact collisions.