Monthly Archives: May 2013

Getting to the point – an alternative to the bezier arrow

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An alternative bezier arrow to the regular grid-bezier. Apart from a cool gradient it has the advantages of: exact width, exact start/end points and axis alignment.

An alternative bezier arrow to the regular grid-bezier. Apart from a cool gradient it has the advantages of: exact width, exact start/end points and axis alignment.

About two weeks ago I got frustrated with the bezierGrob function in the grid package. The lwd parameter is interpreted differently depending on device, the arrow at the end does not follow the line but is perpendicular (probably following the spline control), and the line parameter makes it difficult to control exactly where the line starts/ends. Thus I decided to make my own fancy line with an arrow at the end – at the time I thought: How hard can it be? In retrospect, I wish I never thought of the thing… This article is about the painful process of creating of an alternative to the bezierGrob. Continue reading →

Extracting comorbidities from a database in SPSS

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Using large databases for extracting data can be cumbersome, fortunately it's more reliable than sifting for gold. The image is CC by Won-Tolla.

Using large databases for extracting data can be cumbersome, fortunately it’s more reliable than sifting for gold. The image is CC by Won-Tolla.

I put a lot of effort in to my first article to calculate the comorbidities of a patient according to the Charlson & Elixhauser scores. The available scripts were in SAS and Stata, as I started out using SPSS I decided to implement the code in the neat Python plugin that SPSS provides. In this post I’ll provide you with a detailed walk through of my code, and hopefully it will save you some time. Continue reading →

Age before beauty

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Sticking to the old, proven concepts have often turned out to be a good strategy in orthopaedics. Switching hip implants can be both cumbersome and hazardous. The image is CC by Trey Ratcliff.

Sticking to the old, proven concepts have often turned out to be a good strategy in orthopaedics. Switching hip implants can be both cumbersome and hazardous. The image is CC by Trey Ratcliff.

In my research I focus on patient factors and their impact on re-operation rates after total hip arthroplasties. While they do matter, the implant itself seems to be even more important. One of the most successful implant in the Swedish Hip Arthroplasty Registry is the Link Lubinus SP II implant, while some may argue that it’s an awesome design, I would argue that the tools that it comes with are awesome, thus limiting surgeon’s mistakes. This importance of skill is nicely illustrated in Peltola et al’s recent study, where they found an increased risk for revision during the first 3 years when introducing new implants, hazard ratio was 1.3 (95% CI 1.1 to 1.5) for the first 15 arthroplasties. This increased risk early on is commonly referred to as the learning curve, and may vary between implants. Continue reading →