The Microbiome of Osteoarthritic Hip and Knee Joints: A Prospective Multicenter Investigation.

BACKGROUND: Recent advances in high-throughput DNA sequencing technologies have made it possible to characterize the microbial profile in anatomical sites previously assumed to be sterile. We used this approach to explore the microbial composition within joints of osteoarthritic patients. METHODS: This prospective multicenter study recruited 113 patients undergoing hip or knee arthroplasty between 2017 and 2019. Demographics and prior intra-articular injections were noted. Matched synovial fluid, tissue, and swab specimens were obtained and shipped to a centralized laboratory for testing. Following DNA extraction, microbial 16S-rRNA sequencing was performed. RESULTS: Comparisons of paired specimens indicated that each was a comparable measure for microbiological sampling of the joint. Swab specimens were modestly different in bacterial composition from synovial fluid and tissue. The 5 most abundant genera were Escherichia, Cutibacterium, Staphylococcus, Acinetobacter, and Pseudomonas. Although sample size varied, the hospital of origin explained a significant portion (18.5%) of the variance in the microbial composition of the joint, and corticosteroid injection within 6 months before arthroplasty was associated with elevated abundance of several lineages. CONCLUSIONS: The findings revealed that prior intra-articular injection and the operative hospital environment may influence the microbial composition of the joint. Furthermore, the most common species observed in this study were not among the most common in previous skin microbiome studies, suggesting that the microbial profiles detected are not likely explained solely by skin contamination. Further research is needed to determine the relationship between the hospital and a "closed" microbiome environment. These findings contribute to establishing the baseline microbial signal and identifying contributing variables in the osteoarthritic joint, which will be valuable as a comparator in the contexts of infection and long-term arthroplasty success. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

An Enhanced Understanding of Culture-Negative Periprosthetic Joint Infection with Next-Generation Sequencing: A Multicenter Study.

BACKGROUND: The challenges of culture-negative periprosthetic joint infection (PJI) have led to the emergence of molecular methods of pathogen identification, including next-generation sequencing (NGS). While its increased sensitivity compared with traditional culture techniques is well documented, it is not fully known which organisms could be expected to be detected with use of NGS. The aim of this study was to describe the NGS profile of culture-negative PJI. METHODS: Patients undergoing revision hip or knee arthroplasty from June 2016 to August 2020 at 14 institutions were prospectively recruited. Patients meeting International Consensus Meeting (ICM) criteria for PJI were included in this study. Intraoperative samples were obtained and concurrently sent for both routine culture and NGS. Patients for whom NGS was positive and standard culture was negative were included in our analysis. RESULTS: The overall cohort included 301 patients who met the ICM criteria for PJI. Of these patients, 85 (28.2%) were culture-negative. A pathogen could be identified by NGS in 56 (65.9%) of these culture-negative patients. Seventeen species were identified as common based on a study-wide incidence threshold of 5%. NGS revealed a polymicrobial infection in 91.1% of culture-negative PJI cases, with the set of common species contributing to 82.4% of polymicrobial profiles. Escherichia coli, Cutibacterium acnes, Staphylococcus epidermidis, and Staphylococcus aureus ranked highest in terms of incidence and study-wide mean relative abundance and were most frequently the dominant organism when occurring in polymicrobial infections. CONCLUSIONS: NGS provides a more comprehensive picture of the microbial profile of infection that is often missed by traditional culture. Examining the profile of PJI in a multicenter cohort using NGS, this study demonstrated that approximately two-thirds of culture-negative PJIs had identifiable opportunistically pathogenic organisms, and furthermore, the majority of infections were polymicrobial. LEVEL OF EVIDENCE: Diagnostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Survivorship and Radiographic Analysis of Highly Porous Acetabular Cups Designed for Improved Osseointegration Potential.

INTRODUCTION: A variety of highly porous materials have been used to obtain biological acetabular fixation after total hip arthroplasty (THA). Due to their improved surface-coated properties, new highly porous titanium metal implants have shown potential to promote prosthesis osseointegration. Therefore, the purpose of this multicenter study was to evaluate: 1) overall acetabular cup survivorship; 2) postoperative complications; and 3) radiographic signs of loosening and radiolucencies in patients who received a new highly porous titanium metal cup. MATERIALS AND METHODS: A total of 81 patients who underwent primary THA and received a new porous acetabular cup between May 16, 2013 and January 27, 2016 at three academic centers were included for analysis. There were 40 women (49%) and 41 men (51%) who had a mean age of 65 years (range, 38 to 95 years) and a mean body mass index (BMI) of 28 kg/m2 (range, 16 to 43 kg/m2). The minimum follow up time was two years and seven months (range, 2 to 4 years). The cup was engineered with fully interconnected porosity designed for potential long-term biologic fixation. Medical records were reviewed to assess for any revision surgeries and postoperative complications, and the most recent radiographs were reviewed for signs of loosening or radiolucencies. RESULTS: Overall, acetabular component survivorship, free of fixation failure or aseptic loosening, was 100%. Two patients underwent revision due to dislocations; however, revisions were performed because no constrained or dual mobility liners were available for the shell at the time. Both patients had successful outcomes and were doing well at final follow up with no further episodes of dislocation. There was one open reduction internal fixation for a periprosthetic femoral fracture, and three polyethylene revisions were performed for instability. In all of these cases, the acetabular cup was retained. On radiographic evaluation of antero-posterior pelvis radiographs, there was one patient who had radiolucencies of <1mm in Zone 1 and Zone 2 at 15 months after surgery, and another patient demonstrated radiolucencies of <1mm in Zone 2 and 3 at one-year follow up. At a minimum of two-year follow up, both patients had non-progressive and stable findings. CONCLUSION: The results of this study demonstrated excellent survivorship, and there were no radiographic failures of this acetabular cup in primary total hip arthroplasty patients. Although two patients were found to have minimal (<1mm) radiolucencies, these were not progressive. Longer follow-up studies are needed to further assess the survivorship and outcomes of this new acetabular cup; however, based on the results of this study, these are expected to be favorable.

Evaluation of Antibiotic-Releasing Triphasic Bone Void Filler In-Vitro.

Bone void fillers (BVFs) containing calcium sulfate, tricalcium phosphate (TCP), and hydroxyapatite can be loaded with antibiotics for infection treatment or prevention under surgeon-directed use. The aim of this study was to characterize the handling and elution properties of a triphasic BVF loaded with common antibiotics. BVF was mixed with vancomycin and/or tobramycin to form pellets, and the set time was recorded. A partial refreshment elution study was conducted with time points at 4, 8, and 24 h, as well as 2, 7, 14, 28, and 42 days. Effects on dissolution were evaluated in a 14-day dissolution study. Set time increased to over 1 h for groups containing tobramycin, although vancomycin had a minimal effect. Pellets continued to elute antibiotics throughout the 42-day elution study, suggesting efficacy for the treatment or prevention of orthopedic infections. BVF containing vancomycin or tobramycin showed similar dissolution at 14 days compared to BVF without antibiotics; however, BVF containing both antibiotics showed significantly more dissolution.

Limb salvage and abductor reattachment using a custom prosthesis with porous tantalum components.

Segmental bone loss secondary to trauma and infection often requires prosthetic components to provide for limb salvage and functional restoration. Current limb salvage techniques and implants are associated with up to a 46% rate of loosening and eventual failure [Clin Orthop Rel Res 1999;358:8]. This case report describes the use of a custom prosthesis for salvage total hip arthroplasty after a proximal femoral resection, for a patient with a history of a comminuted hip fracture and subsequent postoperative infection. Two component parts of the salvage prosthesis were a modular porous tantalum sleeve (Trabecular Metal, Zimmer TMT, Allendale, NJ) and a porous tantalum inset and washer intended for reattachment of the abductors. Throughout the 3-year follow-up of this patient, functional recovery and pain relief were obtained with few limitations.

MRI diagnosis of tears of the hip abductor tendons (gluteus medius and gluteus minimus).

OBJECTIVE: The purpose of our study was to determine the accuracy of MRI for diagnosing tears of the hip abductor tendons (gluteus medius and gluteus minimus) and to evaluate various signs of tendon disruption. MATERIALS AND METHODS: We retrospectively evaluated MRIs of 74 hips (in 45 patients) that were obtained using 35- to 42-cm fields of view and interpreted using primary and secondary signs of tendon disruption. Fifteen hips had surgically proven abductor tendon tears, and 59 hips were either asymptomatic or had surgically confirmed intact tendons. MRI findings were scored by two radiologists through consensus and then again independently by a third radiologist to determine interobserver agreement. RESULTS: The accuracy of MRI for the diagnosis of tears of the abductor tendons was 91%. Statistically significant associations were found between tears of the abductor tendons and areas of high signal intensity superior to the greater trochanter on T2-weighted images (p < 0.0001), tendon elongation in the gluteus medius (p = 0.0028), tendon discontinuity (p = 0.016), and areas of high signal intensity lateral to the greater trochanter on T2-weighted images (p = 0.0213). Interobserver agreement was good to fair. CONCLUSION: MRI showed good accuracy for the diagnosis of tears of the gluteus medius and gluteus minimus tendons. The identification of an area of T2 hyperintensity superior to the greater trochanter had the highest sensitivity and specificity for tears at 73% and 95%, respectively.

Use of the AO femoral distractor in revision total hip arthroplasty.

Use of the femoral distractor in trauma settings is well documented in the orthopedic literature. Use of the device extends into adult reconstructive surgery; surgeons use this distractor as an aid in performing difficult revision total hip arthroplasties (THAs). Patients with associated soft-tissue contractures secondary to subacute or chronic dislocation of a THA may present a clinical picture that might make consideration of simple open reduction only a remote possibility. Patients with long-standing Girdlestone resection arthroplasty usually present with soft-tissue deficiencies that render the hip unstable (unless it is at maximal length), or these patients have severe contractures that make reduction difficult after all components are implanted. We present a distractor technique for reduction of prosthetic components in such clinical situations. The femoral distractor is easily applied, and, because of its mechanical effectiveness, it can assist in reducing the "irreducible" hip.