Accuracy of a patient-specific instrumentation for coronal plane alignment of an anatomic alignment total knee arthroplasty system: A radiographic study.

BACKGROUND: Patient-individualised anatomic alignment in total knee arthroplasty (TKA) requires exact positioning of the tibial and femoral components. Patient-specific instrumentation (PSI) may be advantageous for implantation. However, the role of PSI in the instrumentation of such knee designs has not been investigated. OBJECTIVE: The aim of this study was to investigate the accuracy of a PSI system designed for patient-individualised anatomic alignment. METHODS: Fifty-four patients from a single centre were consecutively enrolled in this study. Patient-specific femoral and tibial cutting guides were manufactured using 3D models from computed tomography (CT) scans. All patients received an anatomic TKA implant design through an extension gap first technique. Postoperative radiography was taken, and implant component alignment and leg alignment were compared to the preoperative planning. RESULTS: Thirty-four patients were evaluable. Mean differences between planned angles values obtained from CT scans and the measured radiographic values were small and not significantly different from zero. CONCLUSIONS: Implantation of an anatomic knee design that allows individual component alignment using PSI is feasible. The percentage of component misalignment in the coronal plane was remarkably low. Whether this leads to clinical benefits requires further verification.

Investigation of Radial Shaft Seal Swelling Using a Special Tribometer and Magnetic Resonance Imaging.

Compatibility between the rubber material of radial shaft seals and the lubricants to be sealed is an important requirement that customers demand of their lubricant suppliers. Among other effects that may result from incompatibility, the penetration of lubricant components into the rubber (swelling) can impair the seal's functionality due to changes in its geometry and mechanical behavior. Typically, the penetration of a lubricant into an elastomer is evaluated after an immersion test using volumetric, gravimetric, and extraction measurements. Due to the small changes that need to be detected, such methods may not be sufficient to obtain meaningful results. In this contribution, we use magnetic resonance imaging (MRI) to investigate swelling on special tribometer samples as well as a radial shaft seal that were previously used in component tests. Several combinations of rubbers and lubricants that have proven to be compatible were tested in addition to combinations with expected incompatibilities in real applications. The results indicate that MRI measurements can be used to quantify the penetration depth and potentially also the velocity with which the lubricant diffuses into the rubber, thereby yielding detailed insights into the swelling process of the seal.

Oesophageal temperature monitoring and incidence of oesophageal lesions after pulmonary vein isolation using a remote robotic navigation system.

AIMS: Oesophageal lesions (EL), a potential complication after pulmonary vein isolation (PVI), have been described recently. A new remote robotic navigation system (RNS; Hansen Medical) provides enhanced catheter stability along with more effective lesion placement. The aim of this prospective study was to evaluate temperature monitoring and incidence of EL when using RNS with an irrigated tip radiofrequency catheter for PVI. METHODS AND RESULTS: Circumferential PVI using RNS was performed in 73 patients (pts) with paroxysmal (n = 46, 63%) and persistent atrial fibrillation. An oesophageal temperature probe was placed in 58 (79.5%) pts and was integrated in the 3D-map (NavX). Power was limited to 25 W at the posterior wall, and in the case of an increase in temperature power was limited to 20 W. Endoscopy was performed in 42 pts within 24 h after PVI. In 44 of 58 (75.9%) pts, a significant rise in temperature (>39 degrees C) was observed. In 6 of 42 (14.3%) pts, an EL was found during endoscopy. In patients with EL, the body mass index (BMI) was significantly lower than in pts without EL (24.1 +/- 2.0 vs. 29.0 +/- 5.8, P = 0.047). The BMI of all patients with EL was <26, whereas all patients without EL had a BMI above 26. The EL showed brisk healing after re-endoscopy within 2 weeks in all pts. CONCLUSION: In patients undergoing PVI using the RNS, the incidence of EL is 14.3% when using power settings comparable to settings used in manual ablation. Patients with lower BMI (<26) are at higher risk for EL.