Citations

ABSTRACTThe current method of measuring arthrofibrosis in live rabbits is critically limited. Specifically, this method involves radioactive fluoroscopy, error‐prone goniometric measurements, and static joint angle outcomes that fail to approximate the compliance of tissues surrounding the joint. This study aims to validate a novel method of capturing the compliance of contracted tissues surrounding the joint without the use of fluoroscopy or animal sacrifice. Surgically induced contractures of one‐hundred and eight rabbits were measured using the current standard of contracture measurement (a pulley system) as well as a newly designed dynamic load cell (DLC) device. The DLC device was highly reliable when compared to the pulley system (r = 0.907, p < 0.001). Finally, the DLC device produced joint stiffness hysteresis curves capable of approximating the compliance of stiff joint tissues, ultimately calculating a mean joint stiffness of 1.57 ± 1.31 N · m · rad−1 (range, 0.33–6.37 N · m · rad−1). In conclusion, the DLC device represents a valid method for measuring joint contractures. Further, the DLC device notably improves current techniques by introducing the capacity to approximate the compliance of contracted tissues in living rabbits. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2186–2192, 2018.

Abstract Background Long-term mortality after primary THA is lower than in the general population, but it is unknown whether this is also true after revision THA. Questions/Purposes We examined (1) long-term mortality according to reasons for revision after revision THA, and (2) relative mortality trends by age at surgery, years since surgery, and calendar year of surgery. Methods This retrospective study included 5417 revision THAs performed in 4532 patients at a tertiary center between 1969 and 2011. Revision THAs were grouped by surgical indication in three categories: periprosthetic joint infections (938; 17%); fractures (646; 12%); and loosening, bearing wear, or dislocation (3833; 71%). Patients were followed up until death or December 31, 2016. The observed number of deaths in the revision THA cohort was compared with the expected number of deaths using standardized mortality ratios (SMRs) and Poisson regression models. The expected number of deaths was calculated assuming that the study cohort had the same calendar year, age, and sex-specific mortality rates as the United States general population. Results The overall age- and sex-adjusted mortality was slightly higher than the general population mortality (SMR, 1.09; 95% CI, 1.05-1.13; p < 0.001). There were significant differences across the three surgical indication subgroups. Compared with the general population mortality, patients who underwent revision THA for infection (SMR, 1.35; 95% CI, 1.24-1.48; p < 0.001) and fractures (SMR, 1.23; 95% CI, 1.11-1.37; p < 0.001) had significantly increased risk of death. Patients who underwent revision THA for aseptic loosening, wear, or dislocation had a mortality risk similar to that of the general population (SMR, 1.01; 95% CI, 0.96-1.06; p = 0.647). The relative mortality risk was highest in younger patients and declined with increasing age at surgery. Although the relative mortality risk among patients with aseptic indications was lower than that of the general population during the first year of surgery, the risk increased with time and got worse than that of the general population after approximately 8 to 10 years after surgery. Relative mortality risk improved with time after revision THA for aseptic loosening, wear, or dislocation. Conclusions Shifting mortality patterns several years after surgery and the excess mortality after revision THA for periprosthetic joint infections and fractures reinforce the need for long-term followup, not only for implant survival but overall health of patients having THA. Level of Evidence Level III, therapeutic study

AimsReconstruction of the acetabulum after resection of a periacetabular malignancy is technically challenging and many different techniques have been used with varying success. Our aim was to prepare a systematic review of the literature dealing with these techniques in order to clarify the management, the rate of complications and the outcomes.Patients and MethodsA search of PubMed and MEDLINE was conducted for English language articles published between January 1990 and February 2017 with combinations of key search terms to identify studies dealing with periacetabular resection with reconstruction in patients with a malignancy. Studies in English that reported radiographic or clinical outcomes were included. Data collected from each study included: the number and type of reconstructions, the pathological diagnosis of the lesions, the mean age and follow-up, gender distribution, implant survivorship, complications, functional outcome, and mortality. The results from individual studies were combined for the general analysis, and then grouped according to the type of reconstruction.ResultsA total of 57 studies met the inclusion criteria and included 1700 patients. Most lesions were metastatic (41%), followed by chondrosarcoma (29%), osteosarcoma (10%), Ewing’s sarcoma (7%), and multiple myeloma (2%). The techniques of reconstruction were divided into seven types for analysis: those involving a Harrington reconstruction, a saddle prosthesis, an allograft and allograft prosthesis composite, a pasteurised autograft, a porous tantalum implant, a custom-made prosthesis and a modular hemipelvic reconstruction. The rate of complications was 50%, with infection (14%) and instability (8%) being the most common. Mortality data were available for 1427 patients (84%); 50% had died of disease progression, 23% were alive with disease, and 27% had no evidence of disease at a mean follow-up of 3.4 years (0 to 34).ConclusionBoth the rate of complications and mortality are high following resection of oncological periacetabular lesions and reconstruction. Many types of reconstruction have been used with unique challenges and complications for each technique. Newer prostheses, including custom-made prostheses and porous tantalum implants and augments, have shown promising early functional and radiographic outcomes. Cite this article: Bone Joint J 2018;100-B(1 Supple A):22–30.

ABSTRACTDegenerative disk disease of the spine is a major cause of back pain and disability. Optimization of regenerative medical therapies for degenerative disk disease requires a deep mechanistic understanding of the factors controlling the structural integrity of spinal tissues. In this investigation, we sought to identify candidate regulatory genes controlling extracellular matrix synthesis in spinal tissues. To achieve this goal we performed high throughput next generation RNA sequencing on 39 annulus fibrosus and 21 nucleus pulposus human tissue samples. Specimens were collected from patients undergoing surgical discectomy for the treatment of degenerative disk disease. Our studies identified associations between extracellular matrix genes, growth factors, and other important regulatory molecules. The fibrous matrix characteristic of annulus fibrosus was associated with expression of the growth factors platelet derived growth factor beta (PDGFB), vascular endothelial growth factor C (VEGFC), and fibroblast growth factor 9 (FGF9). Additionally we observed high expression of multiple signaling proteins involved in the NOTCH and WNT signaling cascades. Nucleus pulposus extracellular matrix related genes were associated with the expression of numerous diffusible growth factors largely associated with the transforming growth signaling cascade, including transforming factor alpha (TGFA), inhibin alpha (INHA), inhibin beta A (INHBA), bone morphogenetic proteins (BMP2, BMP6), and others. Clinical significance: this investigation provides important data on extracellular matrix gene regulatory networks in disk tissues. This information can be used to optimize pharmacologic, stem cell, and tissue engineering strategies for regeneration of the intervertebral disk and the treatment of back pain. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1356–1369, 2018.

Background: There are conflicting data on the results of irrigation and debridement with component retention in patients with acute periprosthetic hip infections. The goals of this study were to examine contemporary results of irrigation and debridement with component retention for acute infection after primary hip arthroplasty and to identify host, organism, antibiotic, or implant factors that predict success or failure. Methods: Ninety hips (57 total hip arthroplasties and 33 hemiarthroplasties) were diagnosed with acute periprosthetic hip infection (using strict criteria) and were treated with irrigation and debridement and component retention between 2000 and 2012. The mean follow-up was 6 years. Patients were stratified on the basis of McPherson criteria. Hips were managed with irrigation and debridement and retention of well-fixed implants with modular head and liner exchange (70%) or irrigation and debridement alone (30%). Seventy-seven percent of patients were treated with chronic antibiotic suppression. Failure was defined as failure to eradicate infection, characterized by a wound fistula, drainage, intolerable pain, or infection recurrence caused by the same organism strain; subsequent removal of any component for infection; unplanned second wound debridement for ongoing deep infection; and/or occurrence of periprosthetic joint infection-related mortality. Results: Treatment failure occurred in 17% (15 of 90 hips), with component removal secondary to recurrent infection in 10% (9 of 90 hips). Treatment failure occurred in 15% (10 of 66 hips) after early postoperative infection and 21% (5 of 24 hips) after acute hematogenous infection (p = 0.7). Patients with McPherson host grade A had a treatment failure rate of 8%, compared with 16% (p = 0.04) in host grade B and 44% in host grade C (p = 0.006). Most treatment failures (12 of 15 failures) occurred within the initial 6 weeks of treatment; failures subsequent to 6 weeks occurred in 3% of those treated with chronic antibiotic suppression compared with 11% of those who were not treated with suppression (hazard ratio, 4.0; p = 0.3). Conclusions: The success rate was higher in this contemporary series than in many previous series. Systemic host grade A was predictive of treatment success. Level of Evidence: Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.

AimsPatients with flexion instability after total knee arthroplasty (TKA) often present with a recurrent effusion, which may be a haemarthrosis. While the radiographic factors contributing to flexion instability have been elucidated, the clinical diagnosis remains challenging. Our aim, in this study, was to determine the mean white cell count and differential profile in pre-operative aspirations of synovial fluid in a consecutive series of patients undergoing revision TKA for flexion instability.Patients and MethodsBetween 2000 and 2010, 60 patients undergoing aseptic revision TKA for flexion instability were identified. The results of the pre-operative aspiration of synovial fluid were available for 53 patients (88%). These patients were 1:2 matched to 106 patients who underwent aseptic TKA for indications other than flexion instability. The mean age of the patients at revision TKA was 65 years (44 to 82) and 55% were women. The mean follow-up was 4.3 years (2 to 10.2).ResultsIn the flexion instability group, the median total cell count was 312 cells/µL (interquartile range (IQR) 104 to 624), with a mean distribution of 45% macrophages (2% to 90%), 30% lymphocytes (1% to 69%), 18% neutrophils (0% to 80%), 0.5% eosinophils (0% to 6%) and 7% other cells (0% to 42%; mainly synovial cells). There was no significant difference in the median total cell count (p = 0.14) or mean distribution of macrophages (p = 0.42), lymphocytes (p = 0.38), neutrophils (p = 0.19) and eosinophils (p = 0.89) between the flexion instability and control groups. There was a significant difference in the percentage of bloody serosanguineous aspirations which was 58% in the flexion instability group and 18% in the control group (odds ratio = 6.5; p = 0.0001).ConclusionsIn the group of patients who underwent revision TKA for flexion instability, most had a mean cell count and differential similar to those who underwent revision for other aseptic indications. However, bloody serosanguineous aspirations were 6.5 times more common in those with flexion instability confirming that many of the recurrent effusions seen in this condition are haemarthroses. Cite this article: Bone Joint J 2017;99-B:1477–81.

Abstract Background Detection and identification of microorganism(s) involved in periprosthetic joint infection (PJI) can inform surgical management and directed antibiotic therapy. Metagenomic shotgun sequencing is a powerful tool with the potential to change how many PJIs are diagnosed as it allows direct detection and identification of pathogens in clinical specimens. In the largest series to date, we utilized a metagenomics-based approach applied to SF to define potential microbial etiologies of failed total knee arthroplasties (TKAs). Methods Synovial fluid was collected from 112 failed TKAs [74 PJI and 38 aseptic implant failure (AF)] via preoperative arthrocentesis. Cell count and differential, standardized culture and DNA-based metagenomic shotgun sequencing were performed. Human DNA was depleted using the MolYsis basic kit prior to DNA extraction, whole genome amplification, and sequencing. Taxonomic assignment of reads and pathogen identification was achieved using a pipeline incorporating k-mer- and marker gene-based classification software. A scheme for analysis and filtration of false-positives was created and applied, incorporating cut-offs for the number of reads, quality scores, and coverage across a reference genome. Patients were classified as having PJI using the IDSA criteria and expert review. Analyses were recorded as percent agreement, with 95% confidence intervals (CI), of metagenomics to SF culture. Results Metagenomic analysis identified the known pathogen in 54 (90%) (CI, 79.5%–96.2%) of the 60 culture-positive PJIs analyzed and one (2%) (CI, 0.0%–8.9%) potential polymicrobial infection not detected by culture. For the 14 culture-negative PJIs tested, metagenomics showed 79% (CI, 49.2%–95.3%) agreement for negative findings; potential pathogens were identified in three (21%) (CI, 4.7%–50.8%) culture-negative PJI cases, with one being polymicrobial. Of the 37 culture-negative AF cases, metagenomics showed 97% (CI, 85.8%–99.9%) agreement with negative culture and identified one (3%) (CI, 0.0%–14.2%) potential pathogen. For the one culture-positive AF case, metagenomic results were negative, suggesting possible culture contamination. Conclusion Metagenomic shotgun sequencing performed on SF can be used to diagnose PJI and may be particularly useful for culture-negative PJI. Disclosures R. Patel, ASM: Board Member, None; CD Diagnostics, BioFire, Curetis, Merck, Hutchison Biofilm Medical Solutions, Accelerate Diagnostics, Allergan, and The Medicines Company: Grant Investigator, Grant recipient; Curetis: Consultant, Monies paid to my employer; A patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic, and a patent on an anti-biofilm substance issued: Patents, Patents, any money is paid to my employer; Actelion: DSMB, Money paid to my employer; ASM and IDSA: Editor’s stipends, Editor’s stipends; NBME, Up-to-Date and the Infectious Diseases Board Review Course: NBME, Up-to-Date and the Infectious Diseases Board Review Course, Honoraria; Roche, ASM, and IDSA: Travel reimbursement, Travel reimbursement

Advances in polyethylene (PE) in total hip arthroplasty have led to interest and increased use of highly crosslinked PE (HXLPE) in total knee arthroplasty (TKA). Biomechanical data suggest improved wear characteristics for HXLPE inserts over conventional PE in TKA. Short-term results from registry data and few clinical trials are promising. Our aim is to present a review of the history of HXLPEs, the use of HXLPE inserts in TKA, concerns regarding potential mechanical complications, and a thorough review of the available biomechanical and clinical data.Cite this article: Bone Joint J 2017;99-B:996–1002.