Retained Functional Antibiotic Hip Spacers Have High Rates of Stem Loosening, Subsidence, and Reoperation.

BACKGROUND: Functional antibiotic hip spacers for treatment of periprosthetic joint infection may be retained in patients deemed too sick for reimplantation, or who elect to forego additional surgery. Our aim was to characterize reoperations, modes of failure, and function outcomes in patients who have retained hip spacers. METHODS: We performed a retrospective review of 43 hips that underwent placement of an articulating hip spacer between January 1, 2014 and November 30, 2021. There were 28 hips that completed 2-stage exchange (TS group) and were reimplanted at mean 4 months (range, 2 to 10). The other 15 hips underwent planned spacer retention (RS group). Mean follow-up was 2.9 years (range, 1 to 6.1 years). The RS group was older (74 versus 66 years, P = .005) and had a higher age-adjusted Charlson Comorbidity Index (4.4 versus 3.3, P = .04) compared with the TS group. RESULTS: Overall survivorship free of reinfection was 91% at 1 year and 86% at 5 years. There were 6 RS hips that underwent reimplantation for spacer failure at a mean of 23 months (range, 6 to 71 months) and 8 had radiographic stem loosening/subsidence. Patients who had a retained spacer at final follow-up were more likely to require a walker (P = .005) or wheelchair (P = .049) compared with patients who underwent reimplantation. CONCLUSIONS: Retained hip spacers can decrease overall surgical burden, but are associated with high rates of stem loosening, subsidence, and unplanned reoperation. Planned spacer retention should be undertaken with caution in patients healthy enough to undergo reimplantation.

Progression of muscle loss and fat accumulation in a rabbit model of rotator cuff tear.

Rotator cuff (RC) tears present a treatment challenge due to muscle atrophy and degeneration, fatty infiltration, and fibrosis. The purpose of this study was to generate a high time-resolution model of RC tear in rabbits and to characterize the progression of architectural and histological changes. Thirty-five female New Zealand White rabbits (age: 6 months) underwent left supraspinatus tenotomy. Five rabbits were used to evaluate immediate muscle architectural changes. The remaining 30 rabbits underwent right shoulder sham surgery and sacrifice at 1, 2, 4, 8, or 16 weeks. Histology was used to quantify muscle fiber cross-sectional area (CSA), muscle degeneration and regeneration, and fat localized to inter- versus intrafascicular regions. Muscle fiber CSA decreased by 26.5% compared to sham at 16 weeks (effect of treatment, p < 0.0001). Muscle degeneration increased after tenotomy (effect of treatment, p = 0.0006) without any change in regeneration. Collagen and fat content increased by 4 weeks and persisted through 16 weeks. Interfascicular fat was increased at all time points, but intrafascicular fat was increased only at 1, 4, and 16 weeks posttenotomy. Intrafascicular fat adjacent to degenerating muscle fibers increased as well (effect of treatment, p < 0.0001; effect of time, p = 0.0102). Statement of clinical relevance: Rabbit supraspinatus tenotomy recapitulates key features of the pathophysiology of human RC tears, including muscle atrophy and degeneration, lack of regeneration, fat accumulation, and fibrosis.

Corrigendum: Transcriptional Time Course After Rotator Cuff Tear.

[This corrects the article DOI: 10.3389/fphys.2021.707116.].

Transcriptional Time Course After Rotator Cuff Tear.

Rotator cuff (RC) tears are prevalent in the population above the age of 60. The disease progression leads to muscle atrophy, fibrosis, and fatty infiltration in the chronic state, which is not improved with intervention or surgical repair. This highlights the need to better understand the underlying dysfunction in muscle after RC tendon tear. Contemporary studies aimed at understanding muscle pathobiology after RC tear have considered transcriptional data in mice, rats and sheep models at 2-3 time points (1 to 16 weeks post injury). However, none of these studies observed a transition or resurgence of gene expression after the initial acute time points. In this study, we collected rabbit supraspinatus muscle tissue with high temporal resolution (1, 2, 4, 8, and 16 weeks) post-tenotomy (n = 6/group), to determine if unique, time-dependent transcriptional changes occur. RNA sequencing and analyses were performed to identify a transcriptional timeline of RC muscle changes and related morphological sequelae. At 1-week post-tenotomy, the greatest number of differentially expressed genes was observed (1,069 up/873 down) which decreases through 2 (170/133), 4 (86/41), and 8 weeks (16/18), followed by a resurgence and transition of expression at 16 weeks (1,421/293), a behavior which previously has not been captured or reported. Broadly, 1-week post-tenotomy is an acute time point with expected immune system responses, catabolism, and changes in energy metabolism, which continues into 2 weeks with less intensity and greater contribution from mitochondrial effects. Expression shifts at 4 weeks post-tenotomy to fatty acid oxidation, lipolysis, and general upregulation of adipogenesis related genes. The effects of previous weeks' transcriptional dysfunction present themselves at 8 weeks post-tenotomy with enriched DNA damage binding, aggresome activity, extracellular matrix-receptor changes, and significant expression of genes known to induce apoptosis. At 16 weeks post-tenotomy, there is a range of enriched pathways including extracellular matrix constituent binding, mitophagy, neuronal activity, immune response, and more, highlighting the chaotic nature of this time point and possibility of a chronic classification. Transcriptional activity correlated significantly with histological changes and were enriched for biologically relevant pathways such as lipid metabolism. These data provide platform for understanding the biological mechanisms of chronic muscle degeneration after RC tears.

Anterior Glenohumeral Instability in the Adolescent Athlete.

Glenohumeral instability is multifactorial and has both static and dynamic elements. The initial management of first-time dislocations has become increasingly controversial, although recent evidence supports operative treatment for adolescents who participate in contact sports. Risk factors for recurrent glenohumeral instability include adolescent age, hyperlaxity, glenoid bone loss, off-track Hill-Sachs lesions, and fixation with <=3 anchors. High rates of return to sport can be expected when the surgical plan is tailored to individual pathology.

The Community Orthopaedic Surgeon Taking Trauma Call: Pediatric Midshaft Clavicle Fracture Pearls and Pitfalls.

Pediatric diaphyseal clavicle fractures are a common injury, particularly in the adolescent athlete. There are no consensus guidelines for operative versus nonoperative management of these injuries; however, there has been a dramatic increase in operative treatment over the past 15 years, primarily guided by literature pertaining to the adult population. Despite this trend, current literature suggests that the majority of these injuries can be treated nonoperatively with good functional outcomes, high rates of return to sport, and low incidence of complications such as nonunion, symptomatic malunion, and refracture. For the rare patient treated nonoperatively who develops a symptomatic nonunion or malunion, delayed corrective surgery remains a viable treatment option. When surgical fixation is pursued, good outcomes have been universally reported, but the optimal indication for surgery remains elusive in this adolescent population.

Volumetric blood flow in transjugular intrahepatic portosystemic shunt revision using 3-dimensional Doppler sonography.

OBJECTIVES: Three-dimensional (3D)/4-dimensional (4D) sonographic measurement of blood volume flow in transjugular intrahepatic porto systemic shunt revision with the intention of objective assessment of shunt patency. METHODS: A total of 17 patients were recruited (12 male and 5 female; mean age, 55 years; range, 30-69 years). An ultrasound system equipped with a 2.0-5.0-MHz probe was used to acquire multivolume 3D/4D color Doppler data sets to assess prerevision and postrevision shunt volume flow. Volume flow was computed offline based on the principle of surface integration of Doppler-measured velocity vectors in a lateral-elevational c-surface positioned at the color flow focal depth (range, 8.0-11.5 cm). Volume flow was compared to routine measurements of the prerevision and postrevision portosystemic pressure gradient. Prerevision volume flow was compared with the outcome to determine whether a flow threshold for revision could be defined. RESULTS: Linear regression of data from revised transjugular intrahepatic portosystemic shunt cases showed an inverse correlation between the mean-normalized change in prerevision and postrevision shunt volume flow and the mean-normalized change in the prerevision and postrevision portosystemic pressure gradient (r(2) = 0.51; P = .020). Increased shunt blood flow corresponded to a decreased pressure gradient. Comparison of prerevision flows showed preliminary threshold development at 1534 mL/min, below which a shunt revision may be recommended (P = .21; area under the receiver operating characteristic curve = 0.78). CONCLUSIONS: Shunt volume flow measurement with 3D/4D Doppler sonography provides a potential alternative to standard pulsed wave Doppler metrics as an indicator of shunt function and predictor of revision.

A prominent requirement for single-minded and the ventral midline in patterning the dorsoventral axis of the crustacean Parhyale hawaiensis.

In bilaterians, establishing the correct spatial positioning of structures along the dorsoventral (DV) axis is essential for proper embryonic development. Insects such as Drosophila rely on the Dorsal activity gradient and Bone morphogenetic protein (BMP) signaling to establish cell fates along the DV axis, leading to the distinction between tissues such as mesoderm, neurogenic ectoderm and dorsal ectoderm in the developing embryo. Subsequently, the ventral midline plays a more restricted role in DV patterning by establishing differential cell fates in adjacent regions of the neurogenic ectoderm. In this study, we examine the function of the ventral midline and the midline-associated gene single-minded (Ph-sim) in the amphipod crustacean Parhyale hawaiensis. Remarkably, we found that Ph-sim and the ventral midline play a central role in establishing proper fates along the entire DV axis in this animal; laser ablation of midline cells causes a failure to form neurogenic ectoderm and Ph-sim RNAi results in severely dorsalized embryos lacking both neurogenic ectoderm and the appendage-bearing lateral ectoderm. Furthermore, we hypothesize that this role of midline cells was present in the last common ancestor of crustaceans and insects. We predict that the transition to a Dorsal-dependent DV patterning system in the phylogenetically derived insect lineage leading to Drosophila has led to a more restricted role of the ventral midline in patterning the DV axis of these insects.

The crustacean Parhyale hawaiensis: a new model for arthropod development.

The great diversity of arthropod body plans, together with our detailed understanding of fruit fly development, makes arthropods a premier taxon for examining the evolutionary diversification of developmental patterns and hence the diversity of extant life. Crustaceans, in particular, show a remarkable range of morphologies and provide a useful outgroup to the insects. The amphipod crustacean Parhyale hawaiensis is becoming established as a model organism for developmental studies within the arthropods. In addition to its phylogenetically strategic position, P. hawaiensis has proven to be highly amenable to experimental manipulation, is straightforward to rear in the laboratory, and has large numbers of embryos that are available year-round. A detailed staging system has been developed to characterize P. hawaiensis embryogenesis. Robust protocols exist for the collection and fixation of all embryonic stages, in situ hybridization to study mRNA localization, and immunohistochemistry to study protein localization. Microinjection of blastomeres enables detailed cell-lineage analyses, transient and transgenic introduction of recombinant genetic material, and targeted knockdowns of gene function using either RNA interference (RNAi) or morpholino methods. Directed genome sequencing will generate important data for comparative studies aimed at understanding cis-regulatory evolution. Bacterial artificial chromosome (BAC) clones containing genes of interest to the developmental and evolutionary biology communities are being targeted for sequencing. An expressed sequence tag (EST) database will facilitate discovery of additional developmental genes and should broaden our understanding of the genetic controls of body patterning. A reference genome from the related amphipod crustacean Jassa slatteryi will shortly be available.

Fixation and dissection of Parhyale hawaiensis embryos.

The great diversity of arthropod body plans, together with our detailed understanding of fruit fly development, makes arthropods a premier taxon for examining the evolutionary diversification of developmental patterns and hence the diversity of extant life. Crustaceans, in particular, show a remarkable range of morphologies and provide a useful outgroup to the insects. The amphipod crustacean Parhyale hawaiensis is becoming established as a model organism for developmental studies within the arthropods. This protocol describes the dissection and fixation of P. hawaiensis embryos. Embryonic tissue fixed in the following manner is suitable for in situ hybridization experiments to study mRNA expression or for immunocytochemistry to study protein localization.

Injection of Parhyale hawaiensis blastomeres with fluorescently labeled tracers.

The great diversity of arthropod body plans, together with our detailed understanding of fruit fly development, makes arthropods a premier taxon for examining the evolutionary diversification of developmental patterns and hence the diversity of extant life. Crustaceans, in particular, show a remarkable range of morphologies and provide a useful outgroup to the insects. The amphipod crustacean Parhyale hawaiensis is becoming established as a model organism for developmental studies within the arthropods. This protocol describes the injection of P. hawaiensis blastomeres with fluorescently labeled tracers for the purpose of cell-lineage analysis. The total (holoblastic) cleavages that characterize early embryogenesis in P. hawaiensis generate an eight-cell embryo with a stereotypical arrangement of blastomeres, each of which already possesses an invariant cell fate. Fluorochrome-conjugated dextran solutions, mRNAs encoding fluorescent proteins, and biotin-dextran have all proven to be useful lineage markers. The relative merits of various tracers are considered.

Antibody staining of Parhyale hawaiensis embryos.

The great diversity of arthropod body plans, together with our detailed understanding of fruit fly development, makes arthropods a premier taxon for examining the evolutionary diversification of developmental patterns and hence the diversity of extant life. Crustaceans, in particular, show a remarkable range of morphologies and provide a useful outgroup to the insects. The amphipod crustacean Parhyale hawaiensis is becoming established as a model organism for developmental studies within the arthropods. This protocol provides a simplified protocol for antibody staining of P. hawaiensis embryos. The method also works well for other arthropods and phyla. Fixed embryos are rehydrated, washed, blocked with normal goat serum, and incubated overnight with primary antibody. Embryos are then washed and incubated with a peroxidase-conjugated secondary antibody that binds to the primary antibody. A subsequent histochemical reaction produces a black stain in those cells where antibodies have localized.

In situ hybridization of labeled RNA probes to fixed Parhyale hawaiensis embryos.

The great diversity of arthropod body plans, together with our detailed understanding of fruit fly development, makes arthropods a premier taxon for examining the evolutionary diversification of developmental patterns and hence the diversity of extant life. Crustaceans, in particular, show a remarkable range of morphologies and provide a useful outgroup to the insects. The amphipod crustacean Parhyale hawaiensis is becoming established as a model organism for developmental studies within the arthropods. This protocol describes in situ hybridization of fluorescein- or digoxigenin (DIG)-labeled RNA probes to fixed P. hawaiensis embryos. Standard techniques of molecular biology should be used to produce an appropriate template for generation of antisense RNA probes. RNA-labeling mixes designed to produce fluorescein- or DIG-labeled RNA probes using T3, T7, or SP6 RNA polymerases are commercially available. Probes should be purified using QIAGEN RNeasy columns or similar means. Considerations for double-labeling experiments using both fluorescein- and DIG-labeled RNA probes are included.