[Flucloxacillin-induced hypokalemia]. / Door flucloxacilline geïnduceerde hypokaliëmie.

Flucloxacillin-induced hypokalaemia can be progressive and life-threatening, despite of potassium supplementation. In this case description, a high dose of intravenous flucloxacillin was started after a 68-year-old patient presented with an infected knee replacement. After two days, hypokalaemia was noted with an inadequate response to potassium supplementation. It was decided to change antibiotics and increase potassium supplementation, with good results. It is advisable to include monitoring of potassium levels in local treatment protocols when flucloxacillin is prescribed.

Debridement, Antibiotics and Implant Retention: A Systematic Review of Strategies for Treatment of Early Infections after Revision Total Knee Arthroplasty.

GOAL: The purpose of this review is to provide a systematic and comprehensive overview of the available literature on the treatment of an early prosthetic joint infection (PJI) after revision total knee arthroplasty (TKA) and provide treatment guidelines. METHODS: This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The search was conducted using the electronic databases of PubMed, Trip, Cochrane, Embase, LILACS and SciElo. After the inclusion of the relevant articles, we extracted the data and results to compose a treatment algorithm for early and acute PJI after revision TKA. RESULTS: After applying the in- and exclusion criteria, seven articles were included in this systematic review focusing on debridement, antibiotics and implant retention (DAIR) for PJI following revision TKA, of which one was prospective and six were retrospective. All studies were qualified as level IV evidence. CONCLUSIONS: The current literature suggests that DAIR is a valid treatment option for early infections after revision TKA with success rates of 50-70%. Repeat DAIR shows success rates of around 50%. Further research should be aimed at predicting successful (repeat/two-stage) DAIRs in larger study populations, antibiotic regimes and the cost effectiveness of a second DAIR after revision TKA.

The diagnostic potential of low-field MRI in problematic total knee arthroplasties - a feasibility study.

PURPOSE: Low-field MRI, allowing imaging in supine and weight-bearing position, may be utilized as a non-invasive and affordable tool to differentiate between causes of dissatisfaction after TKA ('problematic TKA'). However, it remains unclear whether low-field MRI results in sufficient image quality with limited metal artefacts. Therefore, this feasibility study explored the diagnostic value of low-field MRI concerning pathologies associated with problematic TKA's' by comparing low-field MRI findings with CT and surgical findings. Secondly, differences in patellofemoral parameters between supine and weight-bearing low-field MRI were evaluated. METHODS: Eight patients with a problematic TKA were scanned using low-field MRI in weight-bearing and supine conditions. Six of these patients underwent revision surgery. Scans were analysed by a radiologist for pathologies associated with a problematic TKA. Additional patellofemoral and alignment parameters were measured by an imaging expert. MRI observations were compared to those obtained with CT, the diagnosis based on the clinical work-up, and findings during revision surgery. RESULTS: MRI observations of rotational malalignment, component loosening and patellofemoral arthrosis were comparable with the clinical diagnosis (six out of eight) and were confirmed during surgery (four out of six). All MRI observations were in line with CT findings (seven out of seven). Clinical diagnosis and surgical findings of collateral excessive laxity could not be confirmed with MRI (two out of eight). CONCLUSION: Low-field MRI shows comparable diagnostic value as CT and might be a future low cost and ionizing radiation free alternative. Differences between supine and weight-bearing MRI did not yield clinically relevant information. The study was approved by the Medical Research Ethics Committees of Twente (Netherlands Trial Register: Trial NL7009 (NTR7207). Registered 5 March 2018, https://www.trialregister.nl/trial/7009 ).

MRI as Diagnostic Modality for Analyzing the Problematic Knee Arthroplasty: A Systematic Review.

BACKGROUND: Various diagnostic modalities are available to assess the problematic knee arthroplasty. Visualization of soft-tissue structures in relation to the arthroplasty and bone remains difficult. Recent developments in MRI sequences could make MRI a viable addition to the diagnostic arsenal. PURPOSE: To review the diagnostic properties of MRI, to identify certain causes of complaints that may be directly related to implant failure of total (TKA) or unicompartmental knee arthroplasty (UKA); infection, loosening and wear, instability, malalignment, arthrofibrosis, or patellofemoral problems. STUDY TYPE: Systematic review. POPULATION: Twenty-three studies were included: 16 TKA, four UKA, and three cadaveric studies. Causes of knee arthroplasty complaints analyzed were; infection (three), loosening and wear (11), malalignment (five) and instability (four). FIELD STRENGTH AND SEQUENCES: No field strength or sequence restrictions. ASSESSMENT: PubMed, SCOPUS, and EMBASE were searched. Risk of bias was assessed using the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) and the QUality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2). STATISTICAL TESTS: The results of the original research articles are stated. RESULTS: Fifteen studies assessed the reproducibility of analyzing infection, loosening and wear, and malalignment. Fourteen of 15 studies were deemed as adequate to good quality. Results showed a moderate to excellent agreement (ICC/K 0.55-0.97). Fourteen studies addressed the accuracy. For infection and loosening and wear the sensitivity and specificity estimates varied between 0.85-0.97 and 0.70-1.00, respectively. The accuracy for malalignment was excellent (r ≥ 0.81). For these studies QUADAS-2 analysis suggested few risks of bias. A meta-analysis was not possible due to the heterogeneity of the data. DATA CONCLUSION: This study supports that MRI can be used with overall reproducible and accurate results for diagnosing infection, loosening and wear, and malalignment after knee arthroplasty. Nonetheless, studies regarding the diagnosis of instability, arthrofibrosis or patellofemoral complaints using MRI are limited and inconclusive. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:446-458.

Persistent Wound Drainage After Total Joint Arthroplasty: A Narrative Review.

BACKGROUND: Persistent wound drainage after total joint arthroplasty (TJA) is an important complication with potential substantial adverse consequences, in particular periprosthetic joint infection. METHODS: This review evaluated the available literature regarding several issues in the field of persistent wound drainage after TJA and offers a classification of persistent wound drainage and an algorithmic approach to the decision-making process. RESULTS: Available literature addressing the diagnosis and treatment of persistent wound drainage after TJA is scarce and an evidence-based clinical guideline is lacking. This is partially caused by the absence of a universally accepted definition of persistent wound drainage. In patients with persistent wound drainage, clinical signs and serological tests can be helpful in the diagnosis of a developing infection. Regarding the treatment of persistent wound drainage, nonsurgical treatment consists of absorbent dressings, pressure bandages, and temporary joint immobilization. Surgical treatment is advised when wound drainage persists for more than 5-7 days and consists of open debridement with irrigation and exchange of modular components and antimicrobial treatment. CONCLUSION: Based on this literature review, we proposed a classification and algorithmic approach for the management of patients with persistent wound drainage after TJA. Hopefully, this offers the orthopedic surgeon a practical clinical guideline by finding the right balance between overtreatment and undertreatment, weighing the risks and benefits. However, this classification and algorithmic approach should first be evaluated in a prospective trial.

[Diagnostic image. A woman with a growth at a toe nail]. / Een vrouw met een woekering aan de teennagel.

A 34-year-old woman presented with a progressive subungual swelling of the hallux caused by subungual exostosis.

Posterior tibial tendon transfer: results of fixation to the dorsiflexors proximal to the ankle joint.

BACKGROUND: Most techniques for posterior tibial tendon transfer attach the posterior tibial tendon somewhere at the dorsum of the foot. Inadequate tendon length and difficulties in securing the tendon to bone or tendon can complicate these procedures. Performing the tenodesis proximal to the ankle joint can prevent these problems. The present study is the first to describe the results of posterior tibial tendon transfer through the interosseous membrane attaching only the posterior tibial tendon to the extensor tendons proximal to the ankle joint. METHODS: We examined 13 feet in 12 patients with a foot-drop, equinovarus deformity, or both. The median (range) followup was 3.7 years (9 to 81 months) and the median age at surgery as 30 (13 to 59) years. Evaluation included recording patient satisfaction, use of ankle-foot orthoses (AFO), video-assisted gait analysis, physical examination, the Stanmore system, modified Ninkovic method, and complications. RESULTS: At followup, patient satisfaction was excellent to good in nine feet. Ten of the 11 feet that needed an AFO preoperatively did not need one after surgery. Gait analysis demonstrated a good to fair gait in 10 patients. Median dorsiflexion was 0 (-25 to 12) degrees, with dorsiflexion to a neutral position or beyond in nine feet. The Stanmore system and modified Ninkovic method showed excellent to good results in 10 feet. Three complications were recorded including one failed tendon transfer. CONCLUSIONS: Attachment of a split posterior tibial tendon to the extensor tendons proximal to the ankle joint provides results equivalent to other procedures and can be considered a viable operative alternative because it is less difficult and more straightforward than other techniques.

A new CT scan method for measuring the tibial tubercle trochlear groove distance in patellar instability.

Patellar malalignment leading to objective or potential patella instability can be caused by tibial tuberosity lateralisation. This can be treated with a tuberosity medialisation. CT scan measurements are needed to assess the tibial tubercle trochlear groove distance. When using the previously described methods to determine this distance it can be difficult to determine the anatomical structures on the maximum intensity projection images, and this can lead to measurement error. This study was designed to compare the reliability of a new computer based CT measurement to the previously described method to determine the tibial tubercle trochlear groove distance. For each method, four observers measured each of 50 knees twice. The inter- and intra-observer variability for the conventional method and a new method were determined. Using the conventional method, the number of knees for which the difference between the aggregate mean of all eight measurements and the mean of duplicate measurements per observer greater than 2 mm varied among the observers between 7 and 24 for the 50 knees, while this variation between four and seven for the same 50 knees using the new method. The limits of reproducibility based on measurements from the four different observers improved by 25%, indicating that the measurement error is considerably smaller with the new method. We advise using this more accurate method to improve the selection of patients for a tuberosity medialisation.

Conventional radiography cannot replace CT scanning in detecting tibial tubercle lateralisation.

Patellar instability can be caused by an excessive lateral distance between the anterior tibial tubercle and the trochlear groove (TT-TG). This study was designed to compare the TT-TG in reformatted computed tomography to the TT-TG on a 30 degrees axial conventional radiograph (CR) using lead markers to visualize the tibial tubercle and epicondyles. This is the first report on the use of lead markers for determining the TT-TG. Seven symptomatic knees in five patients (mean age 25 years, standard deviation 8.0 years) were investigated. Results showed that the tibial tubercle could be detected on 30 degrees axial CR by a lead marker. Determining the TT-TG however proved to be difficult. A good intra- and interobserver reliability (ICC >0.86) but large measurement error for the axial CR compared to CT was measured (Limits of Reproducibility as quantification of the measurement error was 18 mm for axial CR and 4 mm for CT). Because of the large measurement error for axial CR, the study was terminated after seven symptomatic knees. Positioning of the patient and markers, especially the tibial tubercle marker, probably are important factors leading to the large measurement error. Therefore, axial CR cannot replace CT to detect a pathological tubercle trochlear groove distance.