How to Distinguish Correlation From Causation in Orthopaedic Research

Correlations in observational studies are commonly misinterpreted as causation. Although correlation is necessary to establish a causal relationship between two variables, correlations may also arise due to chance, reverse causality, or confounding. There are several methods available to orthopaedic researchers to determine whether the observed correlations are causal. These methods depend on the key components of the study including, but not limited to, study design and data availability on confounders. In this article, we illustrate the main concepts surrounding correlation and causation using intuitive real-world examples from the orthopaedic literature. Please visit the following https://www.youtube.com/watch?v=WW7pFudZbHA&t=52s for a video that explains the highlights of the paper in practical terms.     

Current concepts in tourniquet uses

Tourniquets have been around for many years, providing surgeons with a bloodless operative field and saving lives in the pre-hospital care of major limb trauma. However, their use does come with risk. It is therefore extremely important that we, as surgeons, fully understand the physiological influence they impose on patients, the complications associated with their use and, moreover, how to minimize the incidence of these complications. Most tourniquets are now electronically controlled pneumatic devices with built-in pressure sensors and timers. Classically, inflation to 250 mmHg in the upper limb and 300 mmHg in the lower limb is used, but a move towards patient-specific limb occlusion pressures is suggested, although it is more difficult due to the requirement of more time-consuming set-up. Complications from tourniquets can occur, such as nerve injury, pain, venous thromboembolism or even cardiac overload and reperfusion injury. Limiting use to key parts of an operation or using alternatives such as adrenaline infiltration and tranexamic acid can be of benefit. As such, any use of a tourniquet during an operation must be treated with caution and be deployed taking into account the specific characteristics of that particular patient.