Philipp Dworschak

The influence of polyethylene bearing thickness on the tibiofemoral kinematics of a bicruciate retaining total knee arthroplasty

BACKGROUND The recently reintroduced bicruciate retaining Total Knee Arthroplasty (BCR TKA) is an effort to reproduce kinematics closer to the native knee. However, there is no data on appropriate balancing with this implant. Balancing is crucial and challenging as medial and lateral polyethylene (PE) inlays are modular, which allows for placement of different thicknesses in the medial and lateral compartments. This study aimed at providing a detailed kinematic view on balancing BCR TKA. METHODS Seven fresh frozen cadaver legs were mounted in a kinematic rig that applied squatting under application of physiologic quadriceps and hamstring forces. Additionally, specimen laxity was assessed using Lachman tests and varus/valgus stress tests. Following testing on the native knee, a BCR TKA was implanted in each specimen and all trials were repeated. Using one millimeter increments, five inlay thicknesses were tested to simulate optimal balancing, symmetric under-, and overstuffing, valgus constellation, and varus constellation. RESULTS Overall, knee kinematics following BCR TKA seem to be very close to the native knee. The changes as introduced to tibiofemoral kinematics through over- or understuffing the polyethylene inserts are affecting the system only to a minor degree and generally lack statistical significance. Reproduction of the tibial varus via PE-Inlays did not lead to kinematics much closer to the native knee. CONCLUSIONS The changes introduced to tibiofemoral kinematics by removal of the conforming meniscus and cartilage and replacement with a flat PE insert and femoral component are of more impact than different inlay sizes and their combinations for a BCR TKA.

COPD as a risk factor of the complications in lower limb arthroplasty: a patient-matched study

Purpose A relevant proportion of patients undergoing joint replacement surgery for the treatment of osteoarthritis exhibit COPD. This coincidence may result from an increased prevalence of both the diseases in elderly patients. In this study, COPD, which is known to be associated with a variety of comorbidities, and its potential interactions, eg, mediated via systemic inflammation, are discussed. The purpose of the present study was to identify the role of COPD as an independent risk factor for complications after total knee and hip arthroplasty. Patients and methods In a monocentric patient cohort of 2,760 arthoplasties, propensity score matching was done using the following factors: sex, age, replaced joint, American Society of Anesthesiologists’ score, body mass index, hypertension, chronic heart disease, anticoagulation, diabetes mellitus, chronic renal deficiency, and actual smoking status to create 224 pairs. Both the pre-matched differences and the results after propensity score matching were statistically analyzed with p≤0.05 being defined as statistically significant. Results All confounders were eliminated after matching. Preoperatively measured C-reactive protein and leukocytes were higher in the COPD group (p<0.001; p=0.01, respectively). Intensive care unit admission was higher for COPD patients (p=0.023). Pneumonia occurred in patients with COPD only (p=0.024). There was a trend (not significant) toward a higher rate of wound infections, increased transfusion of red blood cells, and a prolonged hospital stay in patients with COPD. Conclusion COPD was associated with an increased length of hospital stay, a higher risk of pneumonia and wound infection, higher general complications, and an increased need for red blood cell transfusion. It is thus recommended to enhance the implementation of pneumonia prevention programs on surgical wards.