Association of Total Hip Arthroplasty Flexural Rigidity With Magnetic Resonance Imaging and Histological Findings.

BACKGROUND: Modular connections in total hip arthroplasty (THA) offer surgical advantages, but can contribute to implant fretting and corrosion due to micromotion at the head-stem interface. Previous studies implicated lower flexural rigidity as a key contributing factor to THA corrosion and fretting, but none associated flexural rigidity with direct histological evaluation or magnetic resonance imaging (MRI) outcomes. The purpose of this study was to determine how implant flexural rigidity is associated with MRI imaging metrics and histopathological outcomes in patients who have a failed THA. METHODS: Patients requiring revision THA surgery underwent preoperative MRIs with 3-dimensional multispectral imaging techniques to suppress metal artifacts. The MRI images were graded for adverse local tissue reactions. For each hip, trunnion flexural rigidity was measured from the retrieved femoral stem, and a periprosthetic tissue sample was retrieved and evaluated using semiquantitative histology. Generalized linear models and analyses of variance were used to assess associations between flexural rigidity and MRI and histology outcomes. RESULTS: A total of 106 THA stems were retrieved (46 women and 60 men, age: 68 years (range, 60 to 73 years). After adjustment for length of implantation, flexural rigidity was negatively correlated with histologic aseptic lymphocyte-dominant vasculitis-associated lesion severity (ß = -26.27, P = .018), Fujishiro lymphocyte grading (ß = -13.4, P = .039), perivascular lymphocyte layers (ß = -17.8, P = .022), the grade of tissue organization (ß = -22.5, P = .009), the presence of diffuse synovitis (ß = -66.5, P = .003), and the presence of lymphoid aggregates (ß = -75.9, P = .022). No association was found between MRI metrics and flexural rigidity. CONCLUSIONS: Among these implants, decreased trunnion stiffness was associated with increased histologic features of adverse host-mediated soft tissue reactions.

Update on the role of pathology and laboratory medicine in diagnosing periprosthetic infection.

Technological and implant design advances have helped reduce the frequency of aseptic total joint arthroplasty failure, but periprosthetic joint infections (PJI) remain a clinical important problem with high patient morbidity. Misinterpreting PJI as aseptic mechanical loosening commonly leads to unsatisfactory revision arthroplasty, persistent infection, and poor long-term results. While there is no single "gold standard" diagnostic test for PJI, recent collaborative efforts by Orthopaedic and Infectious Disease Societies have developed algorithms for diagnosing PJI. However, the efficacy of individual tests as well as diagnostic thresholds are controversial. We review the recommended thresholds for commonly used screening tests as well as tissue histopathology and confirmatory tests to diagnose periprosthetic infection. We also update lesser-known laboratory tests, and we briefly summarize rapidly evolving molecular tests to diagnose periprosthetic infection. Pathologists hold a critical role in assisting with PJI diagnosis, maintaining laboratory test quality and interpreting test results. Collaboration between clinicians and pathologists is essential to provide optimal patient care and reduce the burden of PJI.

Multicenter evaluation of the BIOFIRE Joint Infection Panel for the detection of bacteria, yeast, and AMR genes in synovial fluid samples.

The bioMérieux BIOFIRE Joint Infection (JI) Panel is a multiplex in vitro diagnostic test for the simultaneous and rapid (~1 h) detection of 39 potential pathogens and antimicrobial resistance (AMR) genes directly from synovial fluid (SF) samples. Thirty-one species or groups of microorganisms are included in the kit, as well as several AMR genes. This study, performed to evaluate the BIOFIRE JI Panel for regulatory clearance, provides data from a multicenter evaluation of 1,544 prospectively collected residual SF samples with performance compared to standard-of-care (SOC) culture for organisms or polymerase chain reaction (PCR) and sequencing for AMR genes. The BIOFIRE JI Panel demonstrated a sensitivity of 90.9% or greater for all but six organisms and a positive percent agreement (PPA) of 100% for all AMR genes. The BIOFIRE JI Panel demonstrated a specificity of 98.5% or greater for detection of all organisms and a negative percent agreement (NPA) of 95.7% or greater for all AMR genes. The BIOFIRE JI Panel provides an improvement over SOC culture, with a substantially shorter time to result for both organisms and AMR genes with excellent sensitivity/PPA and specificity/NPA, and is anticipated to provide timely and actionable diagnostic information for joint infections in a variety of clinical scenarios.

Rice-Body Synovitis, Foreign Body Reaction, and Rotator Cuff Failure After Subacromial Balloon Spacer Augmentation of a Rotator Cuff Repair: A Case Report.

CASE: A 66-year-old woman presented with shoulder pain and weakness 4 months after augmentation of a rotator cuff repair with a Stryker InSpace subacromial balloon spacer. A magnetic resonance imaging (MRI) demonstrated a failed rotator cuff repair, large effusion with rice bodies, synovitis, axillary lymphadenopathy, loose anchors, and erosive changes to the greater tuberosity. Arthroscopy revealed balloon fragmentation surrounded by diffusely hyperemic synovium without repairable cuff tissue. Final cultures proved negative for infection. Histologic evaluation revealed ulcerated synovium with diffuse chronic and focal acute inflammation. CONCLUSION: Despite promising early results, augmentation of a rotator cuff repair with a subacromial balloon spacer introduces a risk of inflammatory reaction that may mimic a deep infection and compromise rotator cuff healing.

Delayed Failure of M6-C Cervical Disc Arthroplasty After Conversion of Adjacent Cervical Disc Arthroplasty to Fusion: A Case Report.

CASE: We present a delayed failure of an M6-C cervical disc arthroplasty after conversion of a subjacent failed cervical disc arthroplasty to fusion. The annular component had failed, and the core had been ejected. Histology demonstrated a giant cell reaction to polyethylene debris, and tissue cultures were positive for Cutibacterium acnes. CONCLUSION: This is the first report of M6-C failure after conversion of an adjacent arthroplasty to fusion. A growing number of reports surrounding the M6-C failure rate and mechanisms raise concern about the device's durability and underscore the importance of routine clinical and radiographic surveillance for these patients.

Exuberant Rice Body Formation Associated with Adverse Local Tissue Reaction After Hip Resurfacing Arthroplasty: A Case Report and Review of the Literature.

CASE: A 65-year-old man with osteoarthritis of the hip developed a soft-tissue mass of the inferior gluteal region 3 years after metal-on-metal resurfacing hip arthroplasty. Clinical and imaging findings suggested an adverse local tissue reaction. Intraoperatively, nearly 1 liter of intra-articular fibrinous loose bodies (rice bodies) was removed, and histology showed features of an adaptive immune response. The patient had no evidence of an autoimmune disease or mycobacterial infection. CONCLUSION: To our knowledge, this is the first reported case of florid rice bodies associated with a metal-on-metal hip arthroplasty and adverse local tissue reaction.

Allergy Testing Has No Correlation with Intraoperative Histopathology from Revision Total Knee Arthroplasty for Implant-Related Metal Allergy.

Lymphocyte transformation testing (LTT) is often used in the workup for possible metal allergy after total knee arthroplasty (TKA) but the correlation of this test with other diagnostic metal-allergy findings in patients undergoing revision TKA for suspected metal allergy has not been established. A single-center, single-surgeon cohort of 19 TKAs in which both components were revised for presumed implant-related metal allergy based on history, physical, and LTT testing, to nonnickel-containing implants were retrospectively identified. Histopathologic samples obtained intraoperatively were semiquantitatively analyzed using both the Hospital for Special Surgery (HSS) synovial pathology score and the Campbell aseptic lymphocyte-dominant vasculitis-associated lesion (ALVAL) score. As histopathology control group, we included in the study an additional cohort of 17 patients who received aseptic revision TKA and had no history of reported or tested metal sensitivity. All preoperative LTT results were highly reactive to nickel. However, this did not correlate with local periarticular tissue response in 18 of 19 cases which demonstrated a low HSS synovial score (mean: 3.8 ± 2.8, of a maximum score of 28) and the low Campbell ALVAL scores (mean: 2.5/10 ± 1.3, of a maximum score of 10). There were not any significant differences between the study group (suspected implant-related metal allergy) and the control group (nonsuspected implant-related metal allergy) in regard to (1) the Campbell score and (2) the HSS synovial inflammatory score. Knee Society Clinical Rating System (KSCRS) function score improved significantly after revision (mean postoperative increase: 34.0 ± 17. 2; p < 0.001), as well as mean visual analog scale (VAS) pain (mean postoperative decrease: 33.3 ± 26.4; p < 0.01) score. The short-term survival rate (at mean follow-up of 26.1 months) of this patient cohort was 100%. In this cohort of revised TKA patients with suspected nickel allergy based on clinical presentation and LTT positive results, intraoperative histopathology was essentially normal. However, all patients with suspected nickel allergy showed a significant clinical and functional improvement with excellent short-term survival rates. The clinical significance of a positive LTT needs further study.

Diagnosis of Prostate Adenocarcinoma on Routine Pathology After a Primary Total Hip Arthroplasty.

We present a 67-year-old male patient who presented with insidious worsening of right hip pain over a 6-month period with clinical and radiographic evidence of severe osteoarthritis. The patient underwent a primary total hip arthroplasty where the femoral head specimen was sent to pathology as a routine specimen. Pathology results demonstrated metastatic adenocarcinoma of prostate origin. The present case emphasizes the importance of routine pathologic examination of femoral head specimens retrieved during total hip arthroplasty, particularly since this was a clinically unsuspected finding. Although cases like these are rare and the process of routine pathologic examination raises a concern for economic implications, a timely diagnosis of adenocarcinoma provides benefits for the patient, for which cost-benefit ratios are difficult to quantify.

A Postmortem Analysis of Polyethylene Damage and Periprosthetic Tissue in Rotating Platform and Fixed Bearing Tibial Inserts.

BACKGROUND: Mobile bearing designs are intended to reduce wear, but mixed results were reported from retrieval analyses. Postmortem evaluation (PM) provides the opportunity to assess polyethylene damage in successful implants. We compared damage patterns, MRI presentation, and histology between mobile-bearing and fixed tibial inserts retrieved postmortem and compared these results to our prior findings from implants retrieved at revision. METHODS: Eleven postmortem knees with rotating platform (RP) implants and 13 with fixed bearing (FB) implants were examined. All were MRI scanned, and tissue samples were collected from standardized regions for histology. Polyethylene inserts were subjectively scored to assess articular, backside, and PS post surfaces for damage modes and severity. RESULTS: Average duration of implantation was 9.3 years (1.7-19.6 years). Surface burnishing was the most common polyethylene damage mode. Average damage scores were higher for RP (53.4) compared to FB inserts (34.4) due to greater backside damage (13.4 for RP vs 1.4 for FB). A minimal difference in damage was observed on the articular surfaces (37.4 RP vs 30.0 FB). Mild innate macrophage reactions were seen in 8 (72.7%) RP and 5 (45.5%) FB specimens. Polyethylene particles were identified in 7 (63.6%) RP and 3 (27.7%) FB specimens. CONCLUSIONS: Postmortem inserts showed low damage levels and mild tissue reactions compared to those reported for implants removed at revision arthroplasty. Nonetheless, trends in comparing RP and FB inserts were consistent with those seen in retrieval analyses, demonstrating the usefulness of retrieval studies in capturing performance differences among TKA designs.

Reproducibility of pathologic scoring systems for periprosthetic adverse local tissue reactions: A cross-sectional study.

BACKGROUND: Several previous studies have described broad histologic classifications of peri-prosthetic reactions that likely reflect the underlying mechanism of arthroplasty failure; however, a consensus has not yet been reached about the relative importance of individual observations. QUESTION/PURPOSE: The purpose of this study was to evaluate the inter-examiner repeatability of commonly used histopathologic grading methods, and to determine the utility of assigning a more simple, global categorization in patients undergoing revision THA surgery of implants with a variety of bearing combinations. METHODS: Between March 2013 and February 2020, a total of 2131 patients underwent revision hip arthroplasty surgery at a one center, of which 12% (248 of 2131) of patients were enrolled. Two pathologists independently reviewed microscope slides of periprosthetic tissue from these patients, of which 425 slides (229 hips, 222 subjects) were reviewed by both pathologists. Separate slides were used for a priori training of the pathologists. Slides were evaluated with the Campbell Aseptic Lymphocyte-dominant Vasculitis-Associated Lesion (ALVAL) score, the Oxford ALVAL score as modified by Grammatopolous, the Fujishiro and Natu scores, and a proposed simplified pattern classification, similar to that of Krenn et al., that incorporates individual factors of these existing scoring methods and was previously shown to correspond to Magnetic Resonance Imaging findings. Inter-rater agreement was assessed using Gwet's AC1 and AC2 coefficients and correspondence analysis was used to examine associations between individual factors of prior scoring methods with the proposed major pattern. RESULTS: Almost perfect inter-rater repeatability (Gwet's AC2 > 0.8) was found for 71% (15/21) of the individual factors, and substantial interrater agreement was found for the proposed major overall pattern (Gwet's AC1: 0.80, 95%CI: 0.72-0.85). Correspondence analysis was able to explain 89-91% of data variability and was able to identify individual features not commonly associated with a major pattern, but discriminatory of the major pattern, such as "Lymph Cuff Thickness 0.25-0.5″ with ALVAL. CONCLUSION: In contrast to prior examinations, excellent interrater agreement was found that may be attributable to a priori training of raters with a test set of slides or difficulty of interpreting grading criteria. The proposed simplified major pattern classification may facilitate evaluation of histopathologic tissue samples.

Adaptive Immune Response Associated with a Zirconium-Containing, Cemented, Total Knee Arthroplasty: A Case Report.

CASE: A 69-year-old woman underwent revision total knee arthroplasty for patellar component aseptic loosening. The periprosthetic tissue demonstrated histologic features of an adaptive immune response (aseptic lymphocyte-dominant vasculitis-associated lesion [ALVAL]). No particles of corrosion debris were identified. The inflammation seemed to be associated with zirconium oxide (ZrO2) particles added as a bone cement radio-opacifier. CONCLUSION: The factors responsible for the adaptive immune response cannot be determined with certainty; however, this is the first reported case of ALVAL associated with ZrO2-containing bone cement. Previous reports describing ALVAL around failed total knee prostheses have not included observations about the type of contrast material added to cement.

Fretting and corrosion of metal liners from modular dual mobility constructs : a retrieval analysis.

AIMS: Dual mobility implants in total hip arthroplasty are designed to increase the functional head size, thus decreasing the potential for dislocation. Modular dual mobility (MDM) implants incorporate a metal liner (e.g. cobalt-chromium alloy) in a metal shell (e.g. titanium alloy), raising concern for mechanically assisted crevice corrosion at the modular liner-shell connection. We sought to examine fretting and corrosion on MDM liners, to analyze the corrosion products, and to examine histologically the periprosthetic tissues. METHODS: A total of 60 retrieved liners were subjectively scored for fretting and corrosion. The corrosion products from the three most severely corroded implants were removed from the implant surface, imaged using scanning electron microscopy, and analyzed using Fourier-transform infrared spectroscopy. RESULTS: Fretting was present on 88% (53/60) of the retrieved liners, and corrosion was present on 97% (58/60). Fretting was most often found on the lip of the taper at the transition between the lip and the dome regions. Macrophages and particles reflecting an innate inflammatory reaction to corrosion debris were noted in six of the 48 cases for which periprosthetic tissues were examined, and all were associated with retrieved components that had high corrosion scores. CONCLUSION: Our results show that corrosion occurs at the interface between MDM liners and shells and that it can be associated with reactions in the local tissues, suggesting continued concern that this problem may become clinically important with longer-term use of these implants. Cite this article: Bone Joint J 2021;103-B(7):1238-1246.

Sequencing of Circulating Microbial Cell-Free DNA Can Identify Pathogens in Periprosthetic Joint Infections.

BACKGROUND: Over 1 million Americans undergo joint replacement each year, and approximately 1 in 75 will incur a periprosthetic joint infection. Effective treatment necessitates pathogen identification, yet standard-of-care cultures fail to detect organisms in 10% to 20% of cases and require invasive sampling. We hypothesized that cell-free DNA (cfDNA) fragments from microorganisms in a periprosthetic joint infection can be found in the bloodstream and utilized to accurately identify pathogens via next-generation sequencing. METHODS: In this prospective observational study performed at a musculoskeletal specialty hospital in the U.S., we enrolled 53 adults with validated hip or knee periprosthetic joint infections. Participants had peripheral blood drawn immediately prior to surgical treatment. Microbial cfDNA from plasma was sequenced and aligned to a genome database with >1,000 microbial species. Intraoperative tissue and synovial fluid cultures were performed per the standard of care. The primary outcome was accuracy in organism identification with use of blood cfDNA sequencing, as measured by agreement with tissue-culture results. RESULTS: Intraoperative and preoperative joint cultures identified an organism in 46 (87%) of 53 patients. Microbial cfDNA sequencing identified the joint pathogen in 35 cases, including 4 of 7 culture-negative cases (57%). Thus, as an adjunct to cultures, cfDNA sequencing increased pathogen detection from 87% to 94%. The median time to species identification for cases with genus-only culture results was 3 days less than standard-of-care methods. Circulating cfDNA sequencing in 14 cases detected additional microorganisms not grown in cultures. At postoperative encounters, cfDNA sequencing demonstrated no detection or reduced levels of the infectious pathogen. CONCLUSIONS: Microbial cfDNA from pathogens causing local periprosthetic joint infections can be detected in peripheral blood. These circulating biomarkers can be sequenced from noninvasive venipuncture, providing a novel source for joint pathogen identification. Further development as an adjunct to tissue cultures holds promise to increase the number of cases with accurate pathogen identification and improve time-to-speciation. This test may also offer a novel method to monitor infection clearance during the treatment period. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Inferior Articular Process Fracture in a Collegiate Athlete Causing Back Pain: A Case Report of Surgical Treatment.

CASE: A 20-year-old male athlete presented with 8 months of low back pain. Conservative management had been unsuccessful. He noted lumbar spine pain with extension, and imaging showed features of an L4-5 inferior articular facet tip fracture. The fragment was excised, he returned to college lacrosse and is without symptoms at the 9-month follow-up. CONCLUSION: In similar cases with facet fragments, we would recommend a full workup and attempt nonoperative therapy. If not improved and a diagnostic injection provides near-complete relief, then resection of the facet fragment can be discussed as a potentially effective and conservative surgical option.

Sister, Sister! Siblings With Simultaneous Early Femoral Insufficiency Fractures After Total Knee Arthroplasty.

Early periprosthetic fractures after total knee arthroplasty are rare but devastating complications which require revision surgery and lead to poor patient satisfaction. We present 2 siblings who underwent primary total knee arthroplasty on the same day and then both presented 2 weeks after surgery with atraumatic periprosthetic femur fractures. The first patient underwent revision for a cemented distal femoral replacement with stemmed tibial fixation. The second patient underwent an isolated femoral component revision with a stemmed femoral component and distal augment. Histological evaluation identified significant peri-implant osteoporosis. The variation in complexity associated with early periprosthetic femoral insufficiency fractures is highlighted by these 2 cases. Surgeons may consider using stemmed femoral components in similar patients if poor distal femoral bone stock is encountered intraoperatively.

Bacterial toxins in musculoskeletal infections.

Musculoskeletal infections (MSKIs) remain a major health burden in orthopaedics. Bacterial toxins are foundational to pathogenesis in MSKI, but poorly understood by the community of providers that care for patients with MSKI, inducing an international group of microbiologists, infectious diseases specialists, orthopaedic surgeons and biofilm scientists to review the literature in this field to identify key topics and compile the current knowledge on the role of toxins in MSKI, with the goal of illuminating potential impact on biofilm formation and dispersal as well as therapeutic strategies. The group concluded that further research is needed to maximize our understanding of the effect of toxins on MSKIs, including: (i) further research to identify the roles of bacterial toxins in MSKIs, (ii) establish the understanding of the importance of environmental and host factors and in vivo expression of toxins throughout the course of an infection, (iii) establish the principles of drug-ability of antitoxins as antimicrobial agents in MSKIs, (iv) have well-defined metrics of success for antitoxins as antiinfective drugs, (v) design a cocktail of antitoxins against specific pathogens to (a) inhibit biofilm formation and (b) inhibit toxin release. The applicability of antitoxins as potential antimicrobials in the era of rising antibiotic resistance could meet the needs of day-to-day clinicians.