Tilman Calliess

Circulating Biomarkers for Discrimination Between Aseptic Joint Failure, Low-Grade Infection And High-Grade Septic Failure

BACKGROUND Late-onset chronic (low-grade) periprosthetic joint infections are often accompanied by unspecific symptoms, false-negative cultures or nonspecific low values of serum biomarkers. This may lead to the unintended implantation of a revision prosthesis into an infected surgical site with the risk of short-term failure developing again. Conversely, false diagnosis of joint infection may result in multistage revision procedures, which expose the patient to unnecessary surgical procedures and inappropriate antibiotic treatment. Here, we investigated whether circulating biomarkers can preoperatively distinguish between aseptic prosthesis loosening and low-grade joint infection, and which biomarker combinations are most accurate. METHODS Inclusion criteria for the study were indication for revision arthroplasty due to aseptic implant failure, acute high-grade infection, or (suspected) low-grade infection. C-reactive protein (CRP), procalcitonin, tumor necrosis factor α, interleukin 6 (IL-6), interleukin 10, and lipopolysaccharide binding protein were assessed preoperatively in the serum of 98 adult patients. RESULTS The classification tree method revealed IL-6 and CRP as the most suitable biomarker combination for the discrimination of aseptic loosening vs low-grade joint infection. The combination of IL-6 >5.12 pg/mL and CRP >0.3 mg/dL correctly identified 15 of 16 patients as having low-grade infection (94%) whereas just one patient was aseptic (6%). CONCLUSIONS This is the first comprehensive prospective clinical study to our knowledge investigating the significance of a combined biomarker approach in differentiating between aseptic prosthesis loosening and low-grade joint infection. CRP plus IL-6 seems to be the most helpful combination for preoperative discrimination of aseptic loosening vs low-grade joint infection.

Unobtrusive ambulatory estimation of knee joint angles during walking using gyroscope and accelerometer data - a preliminary evaluation study

Osteoarthritis has the highest prevalence in the elderly population, with a rising tendency. Currently often special gait labs are used for objective diagnostic assessment of functional motion deficits or treatment outcome, e.g in patients suffering from gonarthrosis. The artificial lab setting and short measurement periods affect the explanatory power of this method. Inertial multi-sensor systems in contrast allow for monitoring human gait independent of a lab setting. However, recent approaches concerning important knee function parameter analyses have not been validated for long-term monitoring yet.The aim of our research for this paper is to evaluate our wearable joint kinematics measurement system (KINEMATIC-WEAR) for assessing maximum knee joint angles during extended periods of normal walking. Our prototype consists of small multi-sensor nodes with combined tri-axial accelerometer, gyroscope and magnetometer which were attached with kinesiotape to the thigh and shank of a subject while walking at different speeds on a treadmill. The computed maximum knee joint angles were compared with reference measurements performed by a physician on video frames captured during walking, as was the correlation between both value sets. Our results show an excellent correlation of 0.96 between clinical reference measurements and our computed angles. While the accuracy is good for slow walking speeds of 0.28 m/s (lkm/h, mean error: 2.6 deg±1.5) and 0.56 m/s (2km/h, mean error: 2.0 deg±1.6), our algorithm over-estimates the angles by 6.3±3.6 degrees at 0.83 m/s (3 km/h), likely induced by soft tissue motion during heel-strike. Our preliminary results show that our system allows for unobtrusive, long-term out-of-Iab monitoring of knee joint motion parameters. Further studies are necessary to evaluate the system for arthritis patients.

Kinematisches Alignment in der Knieendoprothetik

ZusammenfassungHintergrundVor dem Hintergrund weiterhin rund 20 % unzufriedener Patienten nach endoprothetischem Kniegelenkersatz ist eine neue Diskussion um das optimale Alignment in der Knieendoprothetik entfacht. Ein vielversprechender Ansatz ist dabei das kinematische Alignment (KA), das eine Prothesenpositionierung streng anhand der Drehachsen des natürlichen Knies vorsieht.MethodikIn dieser Arbeit wird anhand eines eingehenden Literaturreviews und eigener Forschungsergebnisse das Konzept des KA, einschließlich der Limitationen und der vorhandenen klinische Evidenz erläutert.Ergebnisse und DiskussionErste klinische Studien zeigen eine schnellere Patientenrehabilitation, eine verbesserte Kniefunktion und höhere Patientenzufriedenheit. Allerdings muss auf die noch dünne Evidenzlage hingewiesen werden. Die aus der Technik resultierenden Achsabweichungen zur mechanischen Achse scheinen zumindest kurzfristig keinen negativen Einfluss zu haben, Langzeitergebnisse liegen allerdings noch nicht vor. Dennoch scheint das KA nicht für jeden Patienten geeignet und weitere Untersuchungen für die Formulierung von Ein- und Ausschlusskriterien scheinen sinnvoll.AbstractBackgroundAgainst the background that 20 % of patients are dissatisfied after total knee arthroplasty, there is ongoing controversy about optimal alignment. In this context, orientating the prosthetic components to the natural kinematic axes of the knee appears to be an interesting new concept.MethodsThe objective of this paper is to provide a critical review of the current literature and our own research data regarding the concept of kinematically aligned total knee arthroplasty with the current evidence base and potential limitations.Results and discussionIn the recent literature faster rehabilitation, better knee function, and higher patient satisfaction are described compared to conventional alignment, even if the postoperative alignment deviates more than 3° from the mechanical axis. However, the technique may not be suitable for every patient and pathology, and further research is necessary to set the correct indication.BACKGROUND Against the background that 20 % of patients are dissatisfied after total knee arthroplasty, there is ongoing controversy about optimal alignment. In this context, orientating the prosthetic components to the natural kinematic axes of the knee appears to be an interesting new concept. METHODS The objective of this paper is to provide a critical review of the current literature and our own research data regarding the concept of kinematically aligned total knee arthroplasty with the current evidence base and potential limitations. RESULTS AND DISCUSSION In the recent literature faster rehabilitation, better knee function, and higher patient satisfaction are described compared to conventional alignment, even if the postoperative alignment deviates more than 3° from the mechanical axis. However, the technique may not be suitable for every patient and pathology, and further research is necessary to set the correct indication.

Antimicrobial surface coatings for a permanent percutaneous passage in the concept of osseointegrated extremity prosthesis

Abstract The clinical implementation of percutaneous implants is still limited owing to infections at the side of the stoma. In our concept, this issue is addressed by designing copolymer surface coatings possessing biocompatibility and antimicrobial activity to improve the maintenance of a physiological skin seal at the skin-implant interface. Different copolymers with surface-active phosphonate and antimicrobial cationic groups were designed. Thus, coated titanium samples were cultured with bacterial strains or fibroblasts, respectively. Antimicrobial impact was evaluated by imaging the reduction of bacterial adherence. Biocompatibility was displayed by fibroblast proliferation and morphology. A variety of copolymers of 4-vinylpyridine with vinylbenzylphosphonate or dimethyl(2-methacryloyloxy-ethyl) phosphonate were prepared by free radical polymerization. The optimized polymer coating (copolymer D) showed a reduction of adherent bacteria up to 95%, with only a slight reduction in the adherence of human fibroblasts compared with blank titanium controls. In this study, we demonstrate in vitro that polymer surface coatings can be simultaneously antimicrobial and biocompatible. We consider this to be a promising technology for the realization of a permanent aseptic percutaneous passage as needed for the advancement of osseointegrated limb prosthesis.

Computerassistenzsysteme in der Knieendoprothetik

BACKGROUND The primary goal of computer-assisted surgery (CAS) in total knee arthroplasty is to increase the accuracy in terms of prosthesis positioning. In theory, this would lead to longer implant survival and a reduction of malpositioning. Thus, a better clinical outcome and lower revision rates would be expected. However, the necessary technical equipment represents significant additional effort and cost factors which are not included in the current diagnosis-related groups (DRG) system. OBJECTIVE The objective of this article is a critical review of the current literature to examine whether these costs are reasonable by taking the additional benefits of the technology into account. METHODS This review is based on a selective PubMed search on CAS and navigation in primary total knee arthroplasty. RESULTS The current evidence base on CAS suggests that at least the primary outcome parameter, the improvement of the radiological alignment, is achieved by the technique. However, the claimed secondary effects are not yet proven. In particular, an improvement of clinical outcome and patient satisfaction has not been demonstrated so far. Furthermore, there is some evidence of increased complication rates by the use of CAS. CONCLUSION Against this background and with respect to further cost-benefit analyses, the technology has to be reviewed critically. In particular, low-volume units do not seem to benefit from the use of CAS. However, the assessment of long-term effects is still pending.ZusammenfassungHintergrundDas primäre Ziel der Verwendung von Computerassistenzsystemen (CAS) in der Knieendoprothetik ist die Erhöhung der Implantationsgenauigkeit in Bezug auf die Prothesenpositionierung. In der Theorie verspricht man sich hierdurch eine längere Implantatstandzeit und durch Reduzierung von Fehlpositionierungen letzten Endes auch ein besseres Patientenoutcome sowie geringere Komplikations- und Revisionsraten. Allerdings stellt die erforderliche technische Ausstattung einen Mehraufwand dar, der im aktuellen DRG-System (Diagnosis-Related Groups) nicht abgebildet ist.FragestellungIn dieser Arbeit soll durch ein eingehendes Literaturreview kritisch der Frage nachgegangen werden, ob dieser Mehraufwand durch den zusätzlichen Nutzen der Technik gerechtfertigt ist.Material und MethodeDiese Arbeit basiert auf einer selektiven Literaturrecherche in der Datenbank PubMed zu CAS und Navigationssystemen in der primären Endoprothetik des Kniegelenks.ErgebnisseAus der verfügbaren Evidenz zu den CAS lässt sich schließen, dass zumindest der genannte primäre Zielparameter – die Verbesserung des radiologischen Outcomes – durch die Technik erreicht wird. Allerdings lassen sich die genannten sekundären Effekte in der aktuellen Literatur nicht sicher nachweisen. Insbesondere eine Verbesserung von klinischem Patientenoutcome und -zufriedenheit kann nicht belegt werden. Weiterhin gibt es Hinweise auf erhöhte Komplikationsraten bei der Verwendung von CAS.SchlussfolgerungVor diesem Hintergrund und auch hinsichtlich der Kosten-Nutzen-Analyse muss die Technik entsprechend kritisch betrachtet werden. Insbesondere Kliniken mit kleinen Fallzahlen scheinen nicht von den CAS zu profitieren. Allerdings steht die Bewertung von Langzeiteffekten noch aus.AbstractBackgroundThe primary goal of computer-assisted surgery (CAS) in total knee arthroplasty is to increase the accuracy in terms of prosthesis positioning. In theory, this would lead to longer implant survival and a reduction of malpositioning. Thus, a better clinical outcome and lower revision rates would be expected. However, the necessary technical equipment represents significant additional effort and cost factors which are not included in the current diagnosis-related groups (DRG) system.ObjectiveThe objective of this article is a critical review of the current literature to examine whether these costs are reasonable by taking the additional benefits of the technology into account.MethodsThis review is based on a selective PubMed search on CAS and navigation in primary total knee arthroplasty.ResultsThe current evidence base on CAS suggests that at least the primary outcome parameter, the improvement of the radiological alignment, is achieved by the technique. However, the claimed secondary effects are not yet proven. In particular, an improvement of clinical outcome and patient satisfaction has not been demonstrated so far. Furthermore, there is some evidence of increased complication rates by the use of CAS.ConclusionAgainst this background and with respect to further cost-benefit analyses, the technology has to be reviewed critically. In particular, low-volume units do not seem to benefit from the use of CAS. However, the assessment of long-term effects is still pending.

Knieprothesendesign und Kinematik: Unterschiede in Radien, Konformität und Rotation/Pivot

Today, there is an almost endless variety of knee prosthesis models on the market from which the surgeon can choose. Although the designs appear closer and closer to one another, the industry makes a great effort to emphasise different features as beneficial and a stand-alone. It is increasingly difficult to keep an overview and to assess the clinical relevance of the diverse features. There is a clear lack of independent comparative studies and evidence is low. Nevertheless, different design philosophies require special surgical techniques, so that the surgeon must be familiar with the peculiarity of his/her prosthesis. Also, a differentiated indication for different designs appears to be an interesting concept. The aim of this essay is to give a brief overview of the major design concepts of current unconstrained knee prosthesis designs and their differences regarding biomechanics and kinematics.