Thorsten Gehrke

Combination of reduced oxygen tension and intermittent hydrostatic pressure: a useful tool in articular cartilage tissue engineering

Cartilage cells are normally studied under atmospheric pressure conditions and without loading. However, since cartilage exists in a condition of reduced oxygen and intermittent hydrostatic pressure we hypothesized lower partial oxygen pressures (PO2) and different intermittent hydrostatic pressures (IHP) would increase articular chondrocyte proliferation and matrix production and to stabilize chondrocyte phenotype in vitro. Monolayers of adult bovine articular chondrocytes were cultured under 5% or 21% PO2 in combination with IHP (0.2 MPa amplitude, frequencies 5/5s = 0.1 Hz, 30/2 or 2/30 min on/off loading). We measured proliferation (3H-thymidine incorporation) and collagen secretion (protein-binding assay, collagen type II-ELISA and immunocytochemical staining of pericellular collagen types I, II and IX). Reduced PO2 stimulated proliferation and collagen type II and IX secretion of chondrocytes in comparison to 21% PO2. Additionally, collagen type I expression was delayed by low PO2, indicating a stabilization of the cell phenotype. IHP 5/5s and 30/2 min inhibited proliferation but increased collagen secretion (pericellular collagen type IX was decreased). IHP 30/2 min delayed first expression of collagen type I. In contrast, IHP 2/30 min increased proliferation, but lowered collagen expression. All stimulating or inhibiting effects of PO2 and IHP were additive and vice versa. Reduced PO2 and different settings of IHP increased proliferation, collagen secretion, and phenotype stability of chondrocytes. The oxygen- and IHP-induced effects were additive, suggesting that a combination of these parameters might be a useful tool in cartilage tissue engineering.

How Reliable Is the Alpha-defensin Immunoassay Test for Diagnosing Periprosthetic Joint Infection? A Prospective Study

BackgroundA key issue in the treatment of periprosthetic joint infection (PJI) is the correct diagnosis. The main problem is lack of diagnostic tools able to diagnose a PJI with high accuracy. Alpha-defensin has been proposed as a possible solution, but in the current literature, there is a lack of independent validation.Questions/purposesWe performed a prospective study to determine (1) what is the sensitivity, specificity, and positive and the negative predictive values of the alpha-defensin immunoassay test in diagnosing PJI; and (2) which clinical features may be responsible for false-positive and false-negative results?MethodsPreoperative aspiration was performed in all patients presenting with a painful hip/knee arthroplasty, including both primary and revision implants. Metallosis, other inflammatory comorbidities, and previous/concomitant antibiotic therapy were not considered as exclusion criteria. An inadequate amount of synovial fluid for culture was an exclusion criterion. A total of 156 patients (65 knees, 91 hips) were included in this prospective study. At the time of revision, synovial fluid samples were taken to perform the alpha-defensin assay. During surgical débridement of tissue, samples for cultures and histologic evaluation were taken, and samples were cultured until positive or until negative at 14 days. A diagnosis of PJI was confirmed in 29 patients according to the International Consensus Group on PJI.ResultsThe sensitivity of the alpha-defensin immunoassay was 97% (95% confidence interval [CI], 92%–99%), the specificity was 97% (95% CI, 92%–99%), the positive predictive value was 88% (95% CI, 81%–92%), and the negative predictive value was 99% (95% CI, 96%–99%). Among four false-positive patients, two had metallosis and one had polyethylene wear. The false-negative case presented with a draining sinus, and intraoperative cultures were also negative.ConclusionsAlpha-defensin assay appears to be a reliable test, but followup evaluation is needed to estimate longer term performance of the test. The authors believe that alpha-defensin has demonstrated itself to be sufficiently robust that PJI diagnostic criteria now should include this test. Future studies are needed to compare the differences among the diagnostic capability of the available tests, in particular when metallosis is present, because metallosis may predispose the test to a false-positive result.Level of EvidenceLevel I, diagnostic study.

Five-year Survival of 20,946 Unicondylar Knee Replacements and Patient Risk Factors for Failure: An Analysis of German Insurance Data

BACKGROUND Improvements in implant design and surgical technique of unicondylar knee arthroplasty have led to reduced revision rates, but patient selection seems to be crucial for success of such arthroplasties. The purpose of the present study was to analyze the 5-year implant survival rate of unicondylar knee replacements in Germany and to identify patient factors associated with an increased risk of revision, including >30 comorbid conditions. METHODS Using nationwide billing data of the largest German health-care insurance for inpatient hospital treatment, we identified patients who underwent unicondylar knee arthroplasty between 2006 and 2012. Kaplan-Meier survival curves with revision as the end point and log-rank tests were used to evaluate 5-year implant survival. A multivariable Cox regression model was used to determine factors associated with revision. The risk factors of age, sex, diagnosis, comorbidities, type of implant fixation, and hospital volume were analyzed. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated. RESULTS During the study period, a total of 20,946 unicondylar knee arthroplasties were included. The number of unicondylar knee arthroplasties per year increased during the study period from 2,527 in 2006 to 4,036 in 2012. The median patient age was 64 years (interquartile range, 56 to 72 years), and 60.4% of patients were female. During the time evaluated, the 1-year revision rate decreased from 14.3% in 2006 to 8.7% in 2011. The 5-year survival rate was 87.8% (95% CI, 87.3% to 88.3%). Significant risk factors (p < 0.05) for unicondylar knee arthroplasty revision were younger age (the HR was 2.93 [95% CI, 2.48 to 3.46] for patient age of <55 years, 1.86 [95% CI, 1.58 to 2.19] for 55 to 64 years, and 1.52 [95% CI, 1.29 to 1.79] for 65 to 74 years; patient age of >74 years was used as the reference); female sex (HR, 1.18 [95% CI, 1.07 to 1.29]); complicated diabetes (HR, 1.47 [95% CI, 1.03 to 2.12]); depression (HR, 1.29 [95% CI, 1.06 to 1.57]); obesity, defined as a body mass index of ≥30 kg/m2 (HR, 1.13 [95% CI, 1.02 to 1.26]); and low-volume hospitals, denoted as an annual hospital volume of ≤10 cases (HR, 1.60 [95% CI, 1.39 to 1.84]), 11 to 20 cases (HR, 1.47 [95% CI, 1.27 to 1.70]), and 21 to 40 cases (HR, 1.31 [95% CI, 1.14 to 1.51]) (>40 cases was used as the reference). CONCLUSIONS Apart from known risk factors, this study showed a significant negative influence of obesity, depression, and complicated diabetes on the 5-year unicondylar knee replacement survival rate. Surgical indications and preoperative patient counseling should consider these findings. LEVEL OF EVIDENCE Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

High bacterial contamination rate of electrocautery tips during total hip and knee arthroplasty

PurposeThe aim of the study was to quantify the bacterial contamination rate of electrocautery tips during primary total joint replacement (TJR), as well as during aseptic and septic revision TJR.MethodsA total of 150 electrocautery tips were collected between April and July 2017. TJR surgeries were divided into three groups: (1) primary, (2) aseptic and (3) septic revisions. In each group, a total of 50 electrocautery tips were collected. A monopolar electrocautery with a reusable stainless-steel blade tip was used in all cases. The rate of bacterial contamination was determined for all groups. Correlation of exposure time and type of surgery was analyzed.ResultsThe overall bacterial contamination rate was 14.7% (95% CI 9.4 to 21.4%). The highest contamination rate occurred in the septic revision group (30.0%; 95% CI 17.9 to 44.6%), followed by the primary cases group (10.0%; 95% CI 3.3 to 21.8%) and the aseptic revision group (4.0%; 95% CI 0.5 to 13.7%). Exposure time did not affect the bacterial contamination rate. In 12 out of 15 (80%) contaminations identified in the septic group, we found the same causative microorganism of the prosthetic joint infection on the electrocautery tip.ConclusionsThe bacterial contamination of the electrocautery tips is relatively high, especially during septic hip revision arthroplasty. Electrocautery tips should be changed after debridement of infected tissue.

Are TKAs Performed in High-volume Hospitals Less Likely to Undergo Revision Than TKAs Performed in Low-volume Hospitals?

BackgroundHigh-volume hospitals have achieved better outcomes for THAs and unicompartmental knee arthroplasties (UKAs). However, few studies have analyzed implant survival after primary TKA in high-volume centers.Questions/PurposesIs the risk of revision surgery higher when receiving a TKA in a low-volume hospital than in a high-volume hospital?MethodsUsing nationwide billing data of the largest German healthcare insurer for inpatient hospital treatment, we identified 45,165 TKAs in 44,465 patients insured by Allgemeine Ortskrankenkasse who had undergone knee replacement surgery between January 2012 and December 2012. Revision rates were calculated at 1 and 2 years in all knees. The hospital volume was calculated using volume quintiles of the number of all knee arthroplasties performed in each center. We used multiple logistic regression to model the odds of revision surgery as a function of hospital volume. Age, sex, 31 comorbidities, and variables for socioeconomic status were included as independent variables in the model.ResultsAfter controlling for socioeconomic factors, patient age, sex, and comorbidities, we found that having surgery in a high-volume hospital was associated with a decreased risk of having revision TKA within 2 years of the index procedure. The odds ratio for the 2-year revision was 1.6 (95% CI, 1.4–2.0; p < 0.001) for an annual hospital volume of 56 or fewer cases, 1.5 (95% CI, 1.3–1.7; p < 0.001) for 57 to 93 cases, 1.2 (95% CI, 1.0–1.3; p = 0.039) for 94 to 144 cases, and 1.1 (95% CI, 0.9–1.2; p = 0.319) for 145 to 251 cases compared with a hospital volume of 252 or more cases.ConclusionsWe found a clear association of higher risk for revision surgery when undergoing a TKA in a hospital where less than 145 arthroplasties per year were performed. The study results could help practitioners to guide potential patients in hospitals that perform more TKAs to reduce the overall revision and complication rates. Furthermore, this study underscores the importance of a minimum hospital threshold of arthroplasty cases per year to get permission to perform an arthroplasty.Level of EvidenceLevel III, therapeutic study.

Preliminary results of a 3D-printed acetabular component in the management of extensive defects

Introduction: The treatment of extensive bone loss and massive acetabular defects can be compounded by several challenges and pitfalls. The survivorship following acetabular revision with extensive bone loss is still unsatisfactory. The goal of the present study was to analyse the outcomes of 3D-printed patient-specific acetabular components in the management of extensive acetabular defects and combined pelvic discontinuity (PD). Methods: 9 patients underwent revision THA using 3D-printed custom acetabular components to reconstruct extensive acetabular defects. The Paprosky classifications were determined in all patients. The primary outcome measure was the implant-associated failure rate. Results: 1 out of 9 patients suffered an implant-associated complication (11%). The overall implant-associated survival rate was 89%. The overall complication rate was 56%. Conclusions: The patient-specific acetabular component technique shows promise for the treatment of patients with severe acetabular defects in revision THA. Further research aimed at reducing costs and improving the complication rate are warranted.

Spätfolgen – Diagnose und Therapie

In Deutschland werden pro Jahr ca. 190.000 Primarhuftendoprothesen implantiert (Veit C Qualitat sichtbar machen. BQS-Qualitatsreport 2006. BQS Bundesgesellschaft Qualitatssicherung gGmbH, Dusseldorf, 2007). Wenngleich durch die Verbesserung der Operationstechniken, die Weiterentwicklung der Implantate und die Optimierung der operativen Ausbildung die prozentuale Lockerungsrate abnimmt, resultiert aus der quantitativen Ausdehnung eine zahlenmasige Zunahme der Lockerungen. Gegenwartig wird in der Literatur eine Wechselrate von 0,5–5 % der Prothesen pro Jahr angegeben (J Bone Joint Surg Am 84-A:1788–1792, 2002; Clin Orthop Relat Res 429:188–192, 2004; Clin Orthop Relat Res 447:76–78, 2006; Ortop Traumatol Rehabil 3:34–37, 2001; Veit C Qualitat sichtbar machen. BQS-Qualitatsreport 2006. BQS Bundesgesellschaft Qualitatssicherung gGmbH, Dusseldorf, 2007). Diese Lockerungsrate liegt in den ersten Jahren an der unteren Grenze dieser Spanne, um dann nach 10–15 Jahren anzusteigen. Einschrankend ist dazu auszusagen, dass diese Zahlen weit uberwiegend anhand der Lockerung zementierter Prothesen bzw. heute kaum noch gebrauchlicher zementfreier Prothesen der ersten Generation ermittelt wurde (Clin Orthop Relat Res 447:76–78, 2006). Fur die meisten aktuellen Implantate liegen diese Daten noch nicht vor.

Management of the Infected Total Knee Arthroplasty

There are now several approaches to the infected knee, but complete eradication of infection seems to be near impossible. The treatment protocols include incision and drainage, immediate exchange, and two-stage reimplantation. There are multiple modifications to these approaches that do help to decrease the overall incidence of infection.

How Reliable Is the Cell Count Analysis in the Diagnosis of Prosthetic Joint Infection

BACKGROUND Synovial analysis of joint aspirates is a key diagnostic tool; all major diagnostic algorithms include cell count (CC) and polymorphonuclear percentage (PMN%) as important criteria to make the diagnosis. In this context, we conducted this study to analyze the overall accuracy of CC and PMN%. METHODS A single-center retrospective analysis was performed with clinical data of included patients, with a total of 524 preoperative joint aspirations (255 hips, 269 knees). From the aspirated synovial fluid, we tested the leukocyte esterase activity, leukocyte CC, and PMN%, and sent specimens for aerobic and anaerobic bacterial culture. Depending on the clinical results in accordance with the Musculoskeletal Infection Society criteria for prosthetic joint infection (PJI), 203 patients were then admitted for aseptic revision and 134 patients for septic exchange. RESULTS In 337 cases (64.3% of the study patients), it was possible to measure the CC. The best cutoff level for PJI of all study patients was 2582 leukocytes/μL (sensitivity [SE] 80.6%, specificity [SP] 85.2%) and a PMN% of 66.1% (SE 80.6%, SP 83.3%). The chosen cutoff levels for PJI of total knee and total hip arthroplasty were 1630 leukocytes/μL (SE 83.6%, SP 82.2%) and a PMN% of 60.5% (SE 80.3%, SP 77.1%) and 3063 leukocytes/μL (SE 78.1%, SP 80.0%) and a PMN% of 66.1% (SE 82.2%, SP 82.4%), respectively. CONCLUSIONS CC and PMN% are sensitive methods for diagnosing PJI of total hip and total knee arthroplasty. However, there are differences in cutoff levels between knees and hips. International guidelines and diagnostic criteria need revisions in terms of these parameters.

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.