Human antibody-secreting cells (ASC) in peripheral blood are found after vaccination or infection but rapidly apoptose unless they migrate to the bone marrow (BM). Yet, elements of the BM microenvironment required to sustain long-lived plasma cells (LLPC) remain elusive. Here, we identify BM factors that maintain human ASC > 50 days in vitro. The critical components of the cell-free in vitro BM mimic consist of products from primary BM mesenchymal stromal cells (MSC), a proliferation-inducing ligand (APRIL), and hypoxic conditions. Comparative analysis of protein–protein interactions between BM-MSC proteomics with differential RNA transcriptomics of blood ASC and BM LLPC identify two major survival factors, fibronectin and YWHAZ. The MSC secretome proteins and hypoxic conditions play a role in LLPC survival utilizing mechanisms that downregulate mTORC1 signaling and upregulate hypoxia signatures. In summary, we identify elements of the BM survival niche critical for maturation of blood ASC to BM LLPC.

Introduction. Historically, a majority of prosthetic joint infections (PJIs) grew Gram-positive bacteria. While previous studies stratified PJI risk with specific organisms by patient comorbidities, we compared infection rates and microbiologic characteristics of PJIs by hospital setting: a dedicated orthopaedic hospital versus a general hospital serving multiple surgical specialties. Methods. A retrospective review of prospectively collected data on 11,842 consecutive primary hip and knee arthroplasty patients was performed. Arthroplasty cases performed between April 2006 and August 2008 at the general university hospital serving multiple surgical specialties were compared to cases at a single orthopaedic specialty hospital from September 2008 to August 2016. Results. The general university hospital PJI incidence rate was 1.43%, with 5.3% of infections from Gram-negative species. In comparison, at the dedicated orthopaedic hospital, the overall PJI incidence rate was substantially reduced to 0.75% over the 8-year timeframe. Comparing the final two years of practice at the general university facility to the most recent two years at the dedicated orthopaedics hospital, the PJI incidence was significantly reduced (1.43% vs 0.61%). Though the overall number of infections was reduced, there was a significantly higher proportion of Gram-negative infections over the 8-year timeframe at 25.3%. Conclusion. In transitioning from a multispecialty university hospital to a dedicated orthopaedic hospital, the PJI incidence has been significantly reduced despite a greater Gram-negative proportion (25.3% versus 5.3%). These results suggest a change in the microbiologic profile of PJI when transitioning to a dedicated orthopaedic facility and that greater Gram-negative antibiotic coverage could be considered.

CASE: Two patients presented with chronic knee extensor mechanism disruption after failed primary repairs. Both patients had minimal ambulatory knee function prior to surgical intervention and were treated with a synthetic mesh reconstruction of their extensor mechanism. Our technique has been modified from previously described techniques used in revision knee arthroplasty. At the one-year follow-up, both patients had improvement in their active range of motion and had returned to their previous activity. CONCLUSION: Synthetic mesh reconstruction of chronic extensor mechanism disruption is a viable technique that can be utilized as salvage for the persistently dysfunctional native knee.

Distal radius fractures (DRFs) are common geriatric fractures with the overall incidence expected to increase as the population continues to age. The purpose of this investigation was to compare the short-term complication rates in geriatric versus nongeriatric cohorts following osteosynthesis of DRFs. METHODS: The American Board of Orthopaedic Surgery (ABOS) part II database was queried for adult DRF cases performed from 2007 to 2013. Current Procedural Terminology codes were used to identify cases treated via osteosynthesis. Patient demographic information and reported complication data were analyzed. Comparisons between geriatric (age ≥65 years) and nongeriatric (age <65 years) patients were performed. RESULTS: From 2007 to 2013, a total of 9867 adult DRFs were treated via osteosynthesis by ABOS part II candidates. Geriatric patients comprised 28% of the study cohort. Mean age of the geriatric and nongeriatric cohorts was 74 ± 7 and 46 ± 13 years, respectively. There was a greater proportion of female patients (P< .001) in the geriatric cohort as compared with the nongeriatric cohort. The geriatric cohort demonstrated higher rates of anesthetic complications (P= .021), iatrogenic bone fracture (P= .021), implant failure (P= .031), loss of reduction (P= .001), unspecified medical complications (P= .007), and death (P= .017) than the nongeriatric cohort. The geriatric cohort also showed lower rates of nerve palsy (P= .028) when compared with the nongeriatric cohort, though no differences in rates of secondary surgery were noted between the two cohorts. CONCLUSION: Increased rates of complications related to poor bone quality and poor health status may be expected among geriatric patients following osteosynthesis of DRFs. However, geriatric and nongeriatric patients have similarly low rates of secondary surgery. Future studies are needed to delineate the economic, functional, and societal impact of geriatric DRFs treated via osteosynthesis.