Rotational positioning of the tibial tray in total knee arthroplasty: A CT evaluation

SummaryIntroductionVarious surgical techniques have been described to set the rotational alignment of the tibial baseplate during total knee arthroplasty. The self-positioning method (“self-adjustment”) aligns the tibial implant according to the rotational alignment of the femoral component which is used as a reference after performing repeated knee flexion/extension cycles. Postoperative computed tomography scanning produces accurate measurements of the tibial baseplate rotational alignment with respect to the femoral component.HypothesisThe rotational positioning of the tibial baseplate matches the rotation of the femoral component with parallel alignment to the prosthetic posterior bicondylar axis.Patients and methodsA 3-month follow-up CT scan was carried out after primary total knee arthroplasty implanted in osteoarthritic patients with a mean 7.8° varus deformity of the knee in 50 cases and a mean 8.7° valgus deformity of the knee in 44 cases. The NexGen LPS Flex (Zimmer) fixed-bearing knee prosthesis was used in all cases. An independant examiner (not part of the operating team) measured different variables: the angle between the anatomic transepicondylar axis and the posterior bicondylar axis of the femoral prosthesis (prosthetic posterior condylar angle), the angle between the posterior bicondylar axis and the posterior marginal axis of the tibial prosthesis, the angle between the posterior marginal axis of the tibial prosthesis and the posterior marginal axis of the tibial bone and finally the angle between the anatomic transepicondylar axis and the posterior marginal axis of the tibial prosthesis.ResultsFor the genu varum and genu valgum subgroups, the mean posterior condylar axis of the femoral prosthesis was 3.1° (SD: 1.91; extremes 0° to 17.5°) and 4.7° (SD: 2.7; extremes 0° to 11°) respectively. The tibial baseplate was placed in external rotation with respect to the femoral component: 0.7° (SD : 4.45; extremes –9.5° to 9.8°) and 0.9° (SD: 4.53; extremes –10.8° to 9.5°), but also to the native tibia: 6.1° (SD: 5.85; extremes –4.6° to 22.5°) and 12.5° (SD: 8.6; extremes –10° to 28.9°). The tibial component was placed in internal rotation relative to the anatomic transepicondylar axis: 1.9° (SD : 4.93; extremes –13.6° to 7°) and 3° (SD : 4.38; extremes –16.2° to 4.8°).DiscussionThe tibial component is aligned parallel to the femoral component whatever the initial frontal deformity (P≅0.7). However, a difference was observed between the rotational alignment of the tibial baseplate and the native tibia depending on the initial deformity and could be attributed to the morphological variations of the bony tibial plateau in case of genu valgum.ConclusionThe self-positioning method is a reproducible option when using this type of implant since it allows the tibial component to be positioned parallel to the posterior border of the femur.Level of evidenceLevel III. Observational prospective study

Effects of the humeral tray component positioning for onlay reverse shoulder arthroplasty design: a biomechanical analysis

BACKGROUND: Recent shoulder prostheses have introduced a concept of a universal humeral stem component platform that has an onlay humeral tray for the reverse total shoulder arthroplasty (RTSA). No studies have reported how humeral tray positioning can affect the biomechanics of RTSA. MATERIALS AND METHODS: The Newcastle Shoulder Model was used to investigate the biomechanical effect of humeral tray positioning in the Biomet Comprehensive Total Shoulder System (Biomet, Warsaw, IN, USA) RTSA. Five humeral tray configuration positions were tested: no offset, and 5 mm offset in the anterior, posterior, medial, and lateral positions. Superior and inferior impingement were evaluated for abduction, scapular plane elevation, forward flexion, and external/internal rotation with the elbow at the side (adduction) and at 90 degrees of shoulder abduction. Muscle lengths and moment arms (elevating and rotational) were calculated for the deltoid, the infraspinatus, the teres minor, and the subscapularis. RESULTS: Inferior impingement was not affected by the humeral tray position. There was less superior impingement during abduction, scapular plane elevation, and rotation with the shoulder when the tray was placed laterally or posteriorly. The subscapularis rotational moment arm was increased with a posterior offset, whereas infraspinatus and teres minor rotational moment arms were increased with an anterior offset. Very little change was observed for the deltoid elevating moment arm or for its muscle length. CONCLUSION: Positioning the humeral tray with posterior offset offers a biomechanical advantage for patients needing RTSA by decreasing superior impingement and increasing the internal rotational moment arm of the subscapularis, without creating inferior impingement

Shoulder patient-specific guide: First experience in 10 patients indicates room for improvement

International audienceThe Bees Algorithm (BA) is a recent and powerful foraging algorithm which imitates the natural behaviour of bees. However, it suffers from certain limitations, essentially in the initialization step of the research areas, which is generally random and depends on the individuals' number in the population. In order to solve this problem, this paper proposes a novel hybrid optimisation approach, namely a Hybrid Firefly Bee Algorithm (HFBA), by using the Bees Algorithm (BA) and the Firefly Algorithm (FA). The FA is a swarm intelligence technique based upon the communication behaviour and the idealized flashing features of tropical fireflies. The proposed approach uses a FA in initialization step for a best exploration and detection of promising areas in research space. The performance of HFBA was investigated on a set of benchmark functions and compared with BA, and other well-knows methods. The results show that the HFBA has improved the computational time. It is also very efficient in finding optimal or near optimal solutions, and outperforms the other algorithms in terms of accuracy and speed

[Conduction defects as the presenting feature of sarcoidosis or observed during the course of the disease: regression with corticoid steroid therapy].

International audienceCardiac sarcoidosis is often unrecognised because of the absence of specific clinical and electrical signs. The consequences are serious, the main risk being sudden death due to conduction defects (24 to 31% of cases) or ventricular arrhythmias. Any conduction defect without an obvious cause in a young patient should suggest a possible diagnosis of sarcoidosis. The confirmation is histological when giant cell non-caseuting epithelioid granuloma is demonstrated but myocardial biopsies are only positive in 20% of cases. Therefore, biopsy of accessible organs such as salivary glands is recommended. Diagnostic strategy consists in searching for signs of systemic sarcoidosis, and, when the diagnosis has been established, perform a complete work-up with echocardiography, dipyridamole myocardial scintigraphy, cardiac MRI and 24 hour ambulatory ECG recordings (Holter). The only proven treatment is steroid therapy with occasional spectacular observations of reversibility of arrhythmias or conduction defects

Multiplex PCR/liquid chromatography assay for detection of gene rearrangements: application to RB1 gene

Screening for large gene rearrangements is established as an important part of molecular medicine but is also challenging. A variety of robust methods can detect whole-gene deletions, but will fail to detect more subtle rearrangements that may involve a single exon. In this paper, we describe a new, versatile and robust method to assess exon copy number, called multiplex PCR/liquid chromatography assay (MP/LC). Multiple exons are amplified using unlabeled primers, then separated by ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC), and quantitated by fluorescent detection using a post-column intercalation dye. The relative peak intensities for each target directly reflect exon copy number. This novel technique was used to screen a panel of 121 unrelated retinoblastoma patients who were tested previously using a reference strategy. MP/LC correctly scored all deletions and demonstrated a previously undetected RB1 duplication, the first to be described. MP/LC appears to be an easy, versatile, and cost-effective method, which is particularly relevant to denaturing HPLC (DHPLC) users since it broadens the spectrum of available applications on a DHPLC system