Good accuracy of the alpha-defensin lateral flow test for hip periprosthetic joint infection: A pilot study in a retrospective cohort of 52 patients.

BACKGROUND: The alpha-defensin lateral flow (ADLF) test is a new diagnostic tool for periprosthetic joint infection (PJI). Test accuracy for combined cohorts of hip and knee PJI has been reported to be good. AIM: To assess the accuracy of the ADLF test for hip PJI, and to compare three different diagnostic criteria for PJI. METHODS: A cohort of 52 patients was identified, with a painful or poorly functioning total hip- or hemi-arthroplasty, that underwent aspiration and a subsequent ADLF test. PJI was diagnosed with Musculoskeletal Infection Society (MSIS) criteria, and sensitivity, specificity, overall accuracy, positive predictive value and negative predictive value were calculated. Furthermore, test specifics were compared with the European Bone and Joint Infection Society (EBJIS) and 2018 International Consensus Meeting (ICM) criteria for PJI. RESULTS: Using MSIS criteria, sensitivity was 100% (CI: 54%-100%) and specificity was 89% (CI: 76%-96%). Six true positives and 5 false positives were found, including one case of metallosis. Using EBJIS criteria, more PJIs were found (11 vs 6), sensitivity was lower (71%, CI: 42%-92%) and specificity was higher (97%, CI: 86%-100%), with 4 false negatives and one false positive result. Using 2018 ICM criteria, sensitivity was 91% (62%-100%) and specificity 100% (91%-100%). The results in this cohort are comparable to previous studies. CONCLUSION: Overall test accuracy of the ADLF test was good in this cohort, with a sensitivity of 100% and specificity of 89%. Using different PJI definition criteria, sensitivity and specificity changed slightly but overall accuracy remained around 90%. Using the ADLF test in metallosis cases can result in false positive results and should be performed with caution.

Pinnacle® modular metal-on-metal articulation in primary total hip arthroplasty: mid-term results of 195 cases.

Studies concerning Pinnacle® modular metal-on- metal (MoM) total hip arthroplasty (THA) show better results than for most other MoM THAs. The goal of this study was to report on the revision rate, clinical outcome and metal ion levels regarding this specific prosthesis. Retrospectively selected patients were evaluated clinically, and Visual Analogue Score for pain (VAS), Harris Hip Score (HHS) and Hip disability and Osteoarthritis Outcome Score (HOOS) were determined. Blood metal ion levels were measured. 195 patients were included (mean follow-up 6.4 years). MoM related revision was performed in 5.1%. Clinical outcome was good, with a mean VAS of 6.7 out of 100, HHS of 88.9 and HOOS of 80.7. Five year survival was 96.6%, eight year survival decreased to 90.0%. No correlation could be found between metal ion levels and outcome. Although clinical outcome was good, overall survival of the Pinnacle® MoM is unacceptably low compared to MoP survival.

Hair thread tourniquet syndrome in a toe of an 18 mo old girl.

Hair thread tourniquet syndrome is rare and usually affects little children. If the tourniquet is not incised, the affected body part becomes ischemic or even necrotic. An 18 mo old girl was seen in the emergency ward with a painful, red and swollen third toe of the left foot. The toe appeared to be strangulated with a hair, and the diagnosis hair thread tourniquet syndrome was made. After incision of the hair tourniquet the symptoms soon subsided. The diagnosis is easily made if the clinical features are recognized. However, if the tourniquet is not cut through, the affected body part may become ischemic and even necrotic.

Treatment of acute periprosthetic infections with prosthesis retention: Review of current concepts.

Periprosthetic joint infection (PJI) is a devastating complication after total joint arthroplasty, occurring in approximately 1%-2% of all cases. With growing populations and increasing age, PJI will have a growing effect on health care costs. Many risk factors have been identified that increase the risk of developing PJI, including obesity, immune system deficiencies, malignancy, previous surgery of the same joint and longer operating time. Acute PJI occurs either postoperatively (4 wk to 3 mo after initial arthroplasty, depending on the classification system), or via hematogenous spreading after a period in which the prosthesis had functioned properly. Diagnosis and the choice of treatment are the cornerstones to success. Although different definitions for PJI have been used in the past, most are more or less similar and include the presence of a sinus tract, blood infection values, synovial white blood cell count, signs of infection on histopathological analysis and one or more positive culture results. Debridement, antibiotics and implant retention (DAIR) is the primary treatment for acute PJI, and should be performed as soon as possible after the development of symptoms. Success rates differ, but most studies report success rates of around 60%-80%. Whether single or multiple debridement procedures are more successful remains unclear. The use of local antibiotics in addition to the administration of systemic antibiotic agents is also subject to debate, and its pro's and con's should be carefully considered. Systemic treatment, based on culture results, is of importance for all PJI treatments. Additionally, rifampin should be given in Staphylococcal PJIs, unless all foreign material is removed. The most important factors contributing to treatment failure are longer duration of symptoms, a longer time after initial arthroplasty, the need for more debridement procedures, the retention of exchangeable components, and PJI caused by Staphylococcus (aureus or coagulase negative). If DAIR treatment is unsuccessful, the following treatment option should be based on the patient health status and his or her expectations. For the best functional outcome, one- or two-stage revision should be performed after DAIR failure. In conclusion, DAIR is the obvious choice for treatment of acute PJI, with good success rates in selected patients.

One-stage revision in two cases of Salmonella prosthetic hip infection.

We describe two cases of prosthetic joint infection (PJI) of the hip due to Salmonella. The first patient presented with an early infection 5 d after being discharged following a total hip replacement and the second patient presented at the emergency ward with a late infection, thirteen years following a total hip replacement. Both cases occurred within one month of each other at our institution and both were successfully treated with a one-stage revision. PJI caused by Salmonella species is very rare: so far only 20 Salmonella PJIs of the hip have been described. Therefore, full consensus on the best treatment approach has not yet been reached. An aggressive two-stage approach is advised because of the virulence of Salmonella, although a limited number of successful one-stage approaches have been described as well. According to the latest guidelines, one-stage revision has comparable success rates and less morbidity compared to two-stage treatment, when selecting the right patients. In our opinion, PJI caused by Salmonella should be treated just as PJI caused by other bacteria, with consideration of the selection criteria as mentioned in several treatment guidelines. As illustrated by these two cases, one-stage revision can be successful in both early and late Salmonella PJI of the hip.