Unexpected positive cultures in revision total knee arthroplasty after unicompartmental knee arthroplasty.

PURPOSE: Unexpected positive cultures are defined as a single positive culture in intraoperative samples taken during revision surgery after prosthetic joint infection was preoperatively ruled out. This study aims to determine the prevalence of unexpected positive cultures (UPC) in revision total knee arthroplasty (TKA) after unicompartmental knee arthroplasty (UKA). As a secondary objective, this study aims to compare the re-intervention rate in this specific group, between UPC and non-UPC patients. The hypothesis is that the UPC prevalence in patients who undergo a revision TKA after UKA is not higher than in other TKA revision cases and this does not increase the risk of re-intervention. METHODS: This is a retrospective study where all patients who underwent a UKA revision from January 2016 to February 2023 in a high-volume arthroplasty centre, were analyzed. Unexpected positive culture prevalence in this group of patients was obtained. RESULTS: During the included period, 270 UKA revision surgeries were performed. Eight cases had at least two positive cultures and were therefore excluded. The final analysis included 262 patients. Of these, 8 (3.05%) patients presented UPCs and the isolated microorganisms were low-virulence organisms. None of the UPC patients received any treatment. No statistical differences were found between UPC and non-UPC groups in the analyzed variables. CONCLUSION: The prevalence of unexpected positive cultures in patients following revision of unicompartmental knee arthroplasty is lower than in patients who undergo a revision of total knee arthroplasty. In UKA patients a UPC does not seem to increase the risk of a re-intervention, so it can be safely ignored if ICM criteria are not met.

Cemented vs cementless stems for revision arthroplasties due to Vancouver B2 periprosthetic hip fracture.

PURPOSE: According to Vancouver classification, B2 type fractures are most often treated with removal of the loose stem and implantation of a long stem that bypasses the fracture site. However, there is a controversy about the stem fixation that should be used: cemented or cementless. Hence, this study aims to compare cemented and cementless stems in prosthetic revision due to Vancouver B2 (VB2) periprosthetic hip fracture. METHODS: A retrospective study was done including all the patients treated with stem exchange due to VB2 periprosthetic hip fracture in a tertiary hospital between 2015 and 2022. Patients were divided into two groups according to the stem fixation used: cemented or cementless. Functional outcomes, hospital stay, surgical time, complication rate, and mortality were compared between the two groups of patients. RESULTS: Of the 30 included patients, 13 (43.4%) were treated with cementless stems and 17 (56.7%) with cemented stems. There were no statistically significant differences in age, gender, anesthesia risk scale (ASA) or functional capacity prior to the intervention. Patients treated with cementless stems had a higher complication and reintervention rate than those treated with cemented stems: 62 and 45% versus 34 and 6% (p = 0.035; p = 0.010), respectively. Furthermore, in the group of cementless stems a higher proportion of non-union was found (53.8% vs. 17.6%; p = 0.037). Also, the hospital stay (33 vs. 24 days; p = 0.037) and the time to full weight-bearing (21 days vs. 9 days; p < 0.001) were longer in the cementless stem group. CONCLUSION: Cemented fixation in stem revision due to Vancouver B2 periprosthetic hip fracture could be an optimal option with faster recovery which could decrease the rate of complications and reintervention, without compromising the fracture healing and patient mortality. Thus, this option can be considered when an anatomical reduction can be obtained, especially in elderly patients with multiple comorbidities in which a less aggressive surgical option should be considered.

Vancouver B2 periprosthetic hip fractures treatment: fix or replace? A retrospective study comparing both techniques.

INTRODUCTION: Vancouver B2 periprosthetic hip fractures involve stem stability and they have been classically treated with revision surgery. Crucial factors such as age, clinical comorbidities and functional status are often neglected. The current study aims to compare clinical outcomes between patients treated with open reduction and internal fixation (ORIF) or femoral stem exchange. METHODS: This is a retrospective study that includes all Vancouver B2 periprosthetic hip fractures in a tertiary referral hospital from 2016 to 2020. Patients were divided into two groups: Group 1. Patients treated with an ORIF and Group 2. Patients treated with stem replacement. The outcomes that were compared between groups included demographic data, functional capacity, complications and mortality. RESULTS: 29 periprosthetic Vancouver B2 fractures were finally analyzed. 11 (37.9%) were treated with ORIF (Group 1) and 18 (62.1%) by stem replacement (Group 2). Surgery time (143 vs. 160 min), hemoglobin drop (1.8 vs. 2.5 g/dL) and hospital stance (25.5 vs. 29.6 days) were shorter in Group 1. According to complications, 18.2% of patients in the ORIF group had orthopedic complications compared with 44.4% in the revision group. In the revision group, 3 cases needed a two-stage revision and one of these revisions ended up with a resection arthroplasty (Girdlestone). The first-year mortality rate was 27% in Group 1 and 11% in Group 2. DISCUSSION: ORIF treatment seems to be a less aggressive and complex procedure which can lead to a faster general recovery. Revision surgery can imply a higher risk of orthopedic complications which can be severe and may require further aggressive solutions. The ORIF group mortality was similar to the proximal femur fracture rate (20-30%). In conclusion, ORIF treatment seems to be a good option especially in fragile patients with low functional demand when anatomical reduction is possible.

Unexpected positive cultures in patients with arthrofibrosis following total hip and total knee arthroplasty.

PURPOSE: It has been suggested that low-grade infections could be the cause of arthrofibrosis. However, this hypothesis has not been conclusively proven. The aim of this study is to assess the incidence of unexpected positive cultures (UPC) in patients undergoing revision total joint arthroplasty for a diagnosis of arthrofibrosis. METHODS: A retrospective single-centre review was performed. All patients who underwent an aseptic revision due to histologically confirmed arthrofibrosis (based on the synovial-like interface membrane (SLIM) criteria) were included. The incidence of UPC was then calculated. RESULTS: A total of 147 patients were included. Of these, 100 underwent a total knee arthroplasty (TKA) procedure and 46 a total hip arthroplasty (THA) surgery. One patient had a periprosthetic joint infection and was therefore excluded. Of the 146 included patients, 6 had confirmed UPC (4.08%). The following bacteria were identified: Anaerococcus octavius, Staphylococcus epidermidis, Enterobacter cloacae, Staphylococcus hominis, Streptococcus pluranimalium, Staphylococcus pettenkoferi. CONCLUSIONS: Our results suggest that the incidence of UPC in patients with arthrofibrosis is low. It is lower than that of UPC in patients that undergo a revision for other causes. There is no proven relationship between histologically confirmed arthrofibrosis following total joint arthroplasty and prosthetic joint infection.

Prosthetic joint infection caused by an atypical gram-negative bacilli: Odoribactersplanchnicus.

Prosthetic joint infection (PJI) is a devastating complication after total hip arthroplasty. Its management consists of both: a radical debridement and implant retention or exchange (depending on the timing of symptoms) and directed antibiotic therapy. Thus, the isolation of atypical microorganisms implies a challenge, where anaerobes are responsible for only 4% of cases. However, Odoribacter splanchnicus has not been reported as a cause of PJI yet. We present an 82 year-old woman who was diagnosed with hip PJI. A radical debridement, prosthetic withdrawal, and spacer introduction was performed. Despite the directed antibiotic therapy against E. coli which was first isolated, the patient persisted clinically febrile. An anaerobic Gram-negative rod was isolated and finally, Odoribacter splanchnicus was identified and confirmed by 16S rRNA gene sequencing. Then, antibiotic bitherapy with ciprofloxacin and metronidazole was started until 6 weeks after surgery. The patient had no signs of infection recurrence after then. This case report also shows the importance of genomic identification of rare microorganisms causing PJI, and also allows setting a directed antibiotic therapy which is crucial for infection eradication.