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.

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.

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.