A force-sensing device for assistance in soft-tissue balancing during knee arthroplasty

Nowadays, the large majority of the instrumentation for orthopaedic surgery consists of mechanical tools with varying degrees of complexity. To increase the accuracy and the safety of orthopaedic interventions, sensors and computers were recently introduced in the operating room. Computer Assisted Orthopaedic Surgery (CAOS) uses a navigation system that tracks the movements of surgical instruments in real-time and displays their exact location in relation to the operative area. Such technology improved the quality of orthopaedic arthroplasties, but it is still limited to the measurement of kinematic parameters such as axial alignments, position and angle measurements. In Total Knee Arthroplasty (TKA), the ligament balance, which is crucial for the stability and lifetime of implants, is currently only qualitatively assessed. The goal of this thesis was therefore to demonstrate the importance of intraoperative measurement of musculoskeletal forces through the development of a force-sensing device designed to improve the ligament balancing procedure during TKA. Three possible device designs were proposed and evaluated using finite element analysis in an iterative optimization process. The final design consists of two sensitive plates, one for each condyle, a tibial base plate and a set of spacers to adapt the device thickness to the patient-specific tibiofemoral gaps. Each sensitive plate is equipped with three deformable bridges instrumented with thick-film piezoresistive sensors, which allow accurate measurements of the amplitude and location of the tibiofemoral contact forces. The net varus-valgus moment is then computed to characterize the ligament imbalance. Laboratory experiments showed that the device has appropriate accuracy and dynamic range for the intended application. The first experimental trials on a plastic knee joint model and on a cadaver specimen demonstrated the proper in-situ functioning of the device. The performance and surgical advantages of the device were then evaluated in an in-vitro study including four different experiments: 1) Six knee joints were axially loaded. Comparing applied and measured compressive forces demonstrated the accuracy and reliability of in-situ measurements. 2) To estimate the importance of keeping the patella in its anatomical place during imbalance assessment, the effect of patellar eversion on the mediolateral distribution of tibiofemoral contact forces was measured. One fourth of the patellar load was shifted to the lateral compartment. 3) Assessment of knee stability based on condyle contact forces or varus-valgus moments were compared to the current surgical method (difference of varus-valgus loads causing condyle lift-off). The force-based assessment found to be equivalent to the surgical method while the moment-based technique, which is considered optimal, showed a tendency of lateral imbalance. 4) Finally the effect of minor and major medial collateral ligament releases was biomechanically quantified. Large variation among specimens reflected the difficulty of ligament release and the need for intraoperative force monitoring. Two clinical trials were carried out to evaluate the device performance in a surgical environment. After the tibial cut, the medial and lateral tibiofemoral gaps ensuring the knee stability were determined from the device measurements and compared to the femoral cuts performed on the basis of standard instrumentation. The agreement between the two approaches was generally good. The only significant difference was measured on the first patient at 90° flexion. At this point, the surgeon also estimated that the knee was not optimally balanced, thus demonstrating the consistency between his perception and the device measurements. In conclusion, the proposed force-sensing device for assistance in ligament balancing during TKA provides accurate, reliable and useful measurements. In addition to the precise imbalance assessment based on the measurement of forces and moments, important clinical advantages, such as the possibility to keep the patella in its anatomical place during the measurement or the real-time force monitoring during the delicate phase of ligament release, were demonstrated. The encouraging results of the in-vivo trial proved the usability of the device in a surgical environment and opens the way for larger clinical studies. The developed device has thus potential to improve the ligament balancing procedure, the consistency of surgery and the lifetime of TKA, illustrating thereby the clinical benefit of measuring forces during orthopaedic surgeries

Emotional labour in early childhood education: a labour of love

Despite a large body of international literature on emotional labour in various occupations, there is a paucity of research related to Early Childhood Education (ECE) teachers with not a single research study conducted in New Zealand. The purpose of this research thesis is to explore the role of emotional labour in the work of ECE teachers in Auckland. The research aims to understand how ECE teachers experience emotional labour in their work. A qualitative research methodology was applied to explore the research question and data collection was in the form of semi- structured interviews, narratives and reflections written by the ECE educators identified as participants in the study

Effect of protein kinase A activity on the association of ADP-ribosylation factor 1 to Golgi membranes

The small GTP-binding protein ADP-ribosylation factor 1 (ARF1) is an essential component of the molecular machinery that catalyzes the formation of membrane-bound transport intermediates. By using an in vitro assay that reproduces recruitment of cytosolic proteins onto purified, high salt-washed Golgi membranes, we have analyzed the role of cAMP-dependent protein kinase A (PKA) on ARF1 incorporation. Addition to this assay of either pure catalytic subunits of PKA (C-PKA) or cAMP increased ARF1 binding. By contrast, ARF1 association was inhibited following C-PKA inactivation with either PKA inhibitory peptide or RIIalpha as well as after cytosol depletion of C-PKA. C-PKA also stimulated recruitment and activation of a recombinant form of human ARF1 in the absence of additional cytosolic components. The binding step could be dissociated from the activation reaction and found to be independent of guanine nucleotides and saturable. This step was stimulated by C-PKA in an ATP-dependent manner. Dephosphorylated Golgi membranes exhibited a decreased ability to recruit ARF1, and this effect was reverted by addition of C-PKA. Following an increase in the intracellular level of cAMP, ARF proteins redistributed from cytosol to the perinuclear Golgi region of intact cells. Collectively, the results show that PKA exerts a key regulatory role in the recruitment of ARF1 onto Golgi membranes. In contrast, PKA modulators did not affect recruitment of beta-COP onto Golgi membranes containing prebound ARF1

"Don't add fuel to the fire"- Hyperhemolysis Syndrome in a pregnant woman with compound Sickle cell disease/ß0-thalassemia - Case report and review of the literature

Hyperhemolysis Syndrome (HHS) is a rare and severe post-transfusion complication characterized by the destruction of both recipient and donor red blood cells (RBC). The underlying mechanism of HHS is not fully understood and proper management can be difficult. Furthermore, there are few reports regarding HHS in pregnancy. We report on the development and management of HHS in a pregnant woman with known compound Sickle cell disease/ß-0-thalassemia after transfusion of not fully compatible packed red blood cells (PRBC). We aim to raise awareness on this diagnostically challenging and life-threatening type of hemolysis with this report, and to stress the need to consider the diagnosis of HHS in SCD patients with progressive anemia despite PRBC administration

Fetal RHD Screening in RH1 Negative Pregnant Women: Experience in Switzerland.

RH1 incompatibility between mother and fetus can cause hemolytic disease of the fetus and newborn. In Switzerland, fetal RHD genotyping from maternal blood has been recommended from gestational age 18 onwards since the year 2020. This facilitates tailored administration of RH immunoglobulin (RHIG) only to RH1 negative women carrying a RH1 positive fetus. Data from 30 months of noninvasive fetal RHD screening is presented. Cell-free DNA was extracted from 7192 plasma samples using a commercial kit, followed by an in-house qPCR to detect RHD exons 5 and 7, in addition to an amplification control. Valid results were obtained from 7072 samples, with 4515 (64%) fetuses typed RHD positive and 2556 (36%) fetuses being RHD negative. A total of 120 samples led to inconclusive results due to the presence of maternal or fetal RHD variants (46%), followed by women being serologically RH1 positive (37%), and technical issues (17%). One sample was typed false positive, possibly due to contamination. No false negative results were observed. We show that unnecessary administration of RHIG can be avoided for more than one third of RH1 negative pregnant women in Switzerland. This reduces the risks of exposure to a blood-derived product and conserves this limited resource to women in actual need

In-vitro validation of a device measuring the tibio-femoral contact forces and moments for efficient assistance during ligament balancing in total knee arthroplasty

Ligament balancing in total knee arthroplasty is believed to have an important influence on the joint stability and prosthesis lifetime. In order to provide quantitative information and assistance during the ligament balancing phase, a device that intraoperatively measures knee joint forces and moments has been developed