Minimally invasive total knee replacement: techniques and results

In this review, we outlined the definition of minimally invasive surgery (MIS) in total knee replacement (TKR) and described the different surgical approaches reported in the literature. Afterwards, we went through the most recent studies assessing MIS TKR. Next, we searched for potential limitations of MIS knee replacement and tried to answer the following questions: Are there selective criteria and specific patient selection for MIS knee surgery? If there are, then what are they? After all, a discussion and conclusion completed this article. There is certainly room for MIS or at least less invasive surgery for appropriate selected patients. Nonetheless, there are differences between approaches. Mini-medial parapatellar is easy to master, quick to perform and potentially extendable, whereas mini-subvastus and mini-midvastus are trickier and require more caution related to risk of haematoma and vastus medialis oblique (VMO) nerve damage. Current evidence on the safety and efficacy of mini-incision surgery for TKR does not appear fully adequate for the procedure to be used without special arrangements for consent and for audit or continuing research. There is an argument that a sudden jump from standard TKR to MIS TKR, especially without computer assistance such as navigation, patient-specific instrumentation or robotic, may breach a surgeon's duty of care towards patients because it exposes patients to unnecessary risks. As a final point, more evidence is required on the long-term safety and efficacy of this procedure which will give objective shed light on real benefits of MIS TKR.

Characterisation of a K390R ITK kinase dead transgenic mouse--implications for ITK as a therapeutic target

Interleukin-2 inducible tyrosine kinase (ITK) is expressed in T cells and plays a critical role in signalling through the T cell receptor. Evidence, mainly from knockout mice, has suggested that ITK plays a particularly important function in Th2 cells and this has prompted significant efforts to discover ITK inhibitors for the treatment of allergic disease. However, ITK is known to have functions outside of its kinase domain and in general kinase knockouts are often not good models for the behaviour of small molecule inhibitors. Consequently we have developed a transgenic mouse where the wild type Itk allele has been replaced by a kinase dead Itk allele containing an inactivating K390R point mutation (Itk-KD mice). We have characterised the immune phenotype of these naive mice and their responses to airway inflammation. Unlike Itk knockout (Itk^−/−) mice, T-cells from Itk-KD mice can polymerise actin in response to CD3 activation. The lymph nodes from Itk-KD mice showed more prominent germinal centres than wild type mice and serum antibody levels were significantly abnormal. Unlike the Itk^−/−, γδ T cells in the spleens of the Itk-KD mice had an impaired ability to secrete Th2 cytokines in response to anti-CD3 stimulation whilst the expression of ICOS was not significantly different to wild type. However ICOS expression is markedly increased on αβCD3⁺ cells from the spleens of naïve Itk-KD compared to WT mice. The Itk-KD mice were largely protected from inflammatory symptoms in an Ovalbumin model of airway inflammation. Consequently, our studies have revealed many similarities but some differences between Itk^−/−and Itk-KD transgenic mice. The abnormal antibody response and enhanced ICOS expression on CD3+ cells has implications for the consideration of ITK as a therapeutic target.

Non-invasive quantification of lower limb mechanical alignment in flexion

OBJECTIVE

Non-invasive navigation techniques have recently been developed to determine mechanical femorotibial alignment (MFTA) in extension. The primary aim of this study was to evaluate the precision and accuracy of an image-free navigation system with new software designed to provide multiple kinematic measurements of the knee. The secondary aim was to test two types of strap material used to attach optical trackers to the lower limb.

METHODS

Seventy-two registrations were carried out on 6 intact embalmed cadaveric specimens (mean age: 77.8 ± 12 years). A validated fabric strap, bone screws and novel rubber strap were used to secure the passive tracker baseplate for four full experiments with each knee. The MFTA angle was measured under the conditions of no applied stress, valgus stress, and varus stress. These measurements were carried out at full extension and at 30°, 40°, 50° and 60° of flexion. Intraclass correlation coefficients, repeatability coefficients, and limits of agreement (LOA) were used to convey precision and agreement in measuring MFTA with respect to each of the independent variables, i.e., degree of flexion, applied coronal stress, and method of tracker fixation. Based on the current literature, a repeatability coefficient and LOA of ≤ 3° were deemed acceptable.

RESULTS

The mean fixed flexion for the 6 specimens was 12.8° (range: 6-20°). The mean repeatability coefficient measuring MFTA in extension with screws or fabric strapping of the baseplate was ≤ 2°, compared to 2.3° using rubber strapping. When flexing the knee, MFTA measurements taken using screws or fabric straps remained precise (repeatability coefficient ≤ 3°) throughout the tested range of flexion (12.8-60°); however, using rubber straps, the repeatability coefficient was >3° beyond 50° flexion. In general, applying a varus/valgus stress while measuring MFTA decreased precision beyond 40° flexion. Using fabric strapping, excellent repeatability (coefficient ≤ 2°) was observed until 40° flexion; however, beyond 50° flexion, the repeatability coefficient was >3°. As was the case with precision, agreement between the invasive and non-invasive systems was satisfactory in extension and worsened with flexion. Mean limits of agreement between the invasive and non-invasive system using fabric strapping to assess MFTA were 3° (range: 2.3-3.8°) with no stress applied and 3.9° (range: 2.8-5.2°) with varus and valgus stress. Using rubber strapping, the corresponding values were 4.4° (range: 2.8-8.5°) with no stress applied, 5.5° (range: 3.3-9.0°) with varus stress, and 5.6° (range: 3.3-11.9°) with valgus stress.

DISCUSSION

Acceptable precision and accuracy may be possible when measuring knee kinematics in early flexion using a non-invasive system; however, we do not believe passive trackers should be mounted with rubber strapping such as was used in this study. Flexing the knee appears to decrease the precision and accuracy of the system. The functions of this new software using image-free navigation technology have many potential clinical applications, including assessment of bony and soft tissue deformity, pre-operative planning, and post-operative evaluation, as well as in further pure research comparing kinematics of the normal and pathological knee.

An integrated framework for safety, quality and risk management: an information and incident management system based on a universal patient safety classification

More needs to be done to improve safety and quality and to manage risks in health care. Existing processes are fragmented and there is no single comprehensive source of information about what goes wrong. An integrated framework for the management of safety, quality and risk is needed, with an information and incident management system based on a universal patient safety classification. The World Alliance for Patient Safety provides a platform for the development of a coherent approach; 43 desirable attributes for such an approach are discussed. An example of an incident management and information system serving a patient safety classification is presented, with a brief account of how and where it is currently used. Any such system is valueless unless it improves safety and quality. Quadruple-loop learning (personal, local, national and international) is proposed with examples of how an exemplar system has been successfully used at the various levels. There is currently an opportunity to "get it right" by international cooperation via the World Health Organization to develop an integrated framework incorporating systems that can accommodate information from all sources, manage and monitor things that go wrong, and allow the worldwide sharing of information and the dissemination of tools for the implementation of strategies which have been shown to work.

The generation and characterization of antagonist RNA aptamers to human oncostatin M

Oncostatin M (OSM) is a multifunctional member of the interleukin-6 cytokine family. OSM has been implicated as a powerful proinflammatory mediator and may represent a potentially important, novel therapeutic opportunity for treatment of established rheumatoid arthritis. To further investigate the role of OSM in inflammatory disorders, we have isolated a series of RNA aptamers that bind specifically to human OSM. The highest affinity aptamer, designated ADR58, has been characterized in a series of in vitro and cell based assays. ADR58 has an affinity of 7 nm for human OSM, and it can antagonize OSM binding to the gp130 receptor and specifically antagonize OSM mediated signaling. The aptamer has been truncated in length to 33 bases, all pyrimidine positions are substituted with 2' fluorine, and 14 of 18 purine positions have been substituted with 2' O-methyl to increase stability toward nucleases. This truncated, modified form of ADR58 retains complete affinity and functional activity for OSM. This aptamer may be used as a tool to further investigate the role of OSM in inflammatory disorders and may also have role as a therapeutic agent.

Discovery of novel ansamycins possessing potent inhibitory activity in a cell-based oncostatin M signalling assay

We describe the isolation and characterisation of novel non-benzoquinone ansamycin metabolites related to geldanamycin from a culture of Streptomyces sp. S6699. The compounds possess potent inhibitory activity in a cell-based assay measuring inhibition of oncostatin M signalling in a reporter cell line utilising a secreted placental alkaline phosphatase (sPAP) readout. In this paper we report the isolation and structure elucidation of the compounds and describe some of their biological properties.

An interdisciplinary approach to a day-long palliative care course for undergraduate students

Although it is desirable that students in the health sciences be educated together to prepare them for interdisciplinary practice, many educational programs remain discipline specific. An undergraduate course in palliative care, originally designed for medical students at McMaster University, Hamilton, Ont., was expanded in 1993 to include students from various health sciences programs in the region. The course introduces students to the components of palliative care and its interdisciplinary nature in a problem-based way and directs students to additional educational resources. The authors describe the planning, content and evaluation of the course material. The observed decline in attendance by medical students, which coincided with the introduction of the interdisciplinary format, warrants further investigation. Future directions of the course are discussed.

Measurement of naloxone in plasma using high-performance liquid chromatography with electrochemical detection

A new sample preparation technique, solid-phase extraction employing the ion-pair reagent octyl sodium sulfate (OSS), was developed for the selective isolation of nanogram quantities of naloxone from human plasma. Plasma samples containing naloxone, OSS, buffer, and naltrexone (internal standard) were applied to octyldecylsilane (C18) cartridges, and the opiates were eluted with 100% methanol. An extraction efficiency of 90% was achieved. Extracts were then examined by reversed-phase high-performance liquid chromatography with electrochemical detection, with mobile phase composition adjusted to optimize separation and quantitation. An oxidizing potential of +0.93 V resulted in an assay sensitivity of 1.0 ng. Thus, plasma naloxone levels of ca. 20 ng/ml could be readily detected and quantified. The intra-assay coefficient of variation at plasma levels of 80 ng/ml was 7.2%. Plasma naloxone values obtained during a 5-h infusion of the drug (0.24 mg/min) in two normal human subjects were stable and reproducible. Thus, the method herein described is applicable to human studies employing naloxone infusion.

Naloxone increases water and electrolyte excretion after water loading in patients with cirrhosis and ascites

Endogenous opioids may be involved in the pathogenesis of ascites and edema in patients with liver cirrhosis. We administered the opioid antagonist naloxone (5 mg bolus followed by a 0.06 mg/min infusion) to eight male patients with alcoholic cirrhosis and ascites and to five healthy age- and sex-matched control subjects and determined the effects of naloxone on water and electrolyte excretion after a nonsustained water load (20 ml/kg). In comparison with saline vehicle infusion carried out in the same subjects, naloxone administration resulted in a 50% increase in urine output and creatinine clearance and twofold increases in sodium and potassium excretion in patients with cirrhosis. Fractional sodium and potassium excretion, minimal urinary osmolality, plasma vasopressin and aldosterone levels, arterial blood pressure, and heart rate were not affected by naloxone treatment. The diuretic effect of naloxone was not observed in control subjects. Plasma naloxone levels were about six times higher in patients with cirrhosis than in control subjects (probably because of impaired metabolism of the drug) but only a weak correlation was found between drug levels and the degree of diuresis observed. The diuretic effect of naloxone may be related to an increase in glomerular filtration rate, possibly in conjunction with altered tubular reabsorption.