I went through a phase where I was really interested in indocyanine green (ICG) angiography. Doesn't everybody?
What I learned today
This paper in CORR actually won the Chitranjan Ranawat award at the 2015 Knee Society meeting. The fundamental question is, what is the best skin closure method for TKA?
The study design was a prospective RCT. The authors randomized patients to 3 commonly used methods: running subcuticular, vertical mattress, and skin staples (n=15 per group). Exclusion criteria included previous knee surgery, smoking within one year, diabetes, PAD, long-term steroids, long-term anticoagulant use, chronic infection, and iodine allergy.
Right after closing the midline primary TKA incision, they assessed perfusion intra-operatively using laser-assisted indocyanine green angiography (LA-ICGA).
LA-ICGA involves injecting a fluorescent dye intravenously. As the ICG is carried in the blood, it emits a frequency of light which is recognized by the LA-ICGA camera. The software records a real-time video of these signals. Then the brightness is quantified.
Specifically, in this study, they analyzed the “peak perfusion” at 15-20 seconds and the “baseline perfusion” at 70 seconds in. Also, 27 points were measured along the incision. It makes more sense in an image:
The lighter areas represent more blood flow than the darker ones. So you may already be guessing that the running subcuticular leaves the most blood flow to the incision, followed by vertical mattress and then staples.
Indeed, that’s what the authors found. With or without multivariate adjustment for age, sex, and BMI. Just look at this graph:
Anyway, this study isn't the end-all-be-all, but I think it's an extremely clinically relevant application of this newer (to orthopedics, at least) technology. And it does support other studies which have shown that staples are inferior — see paper discussion for more details.
Finally, one interesting comment by the authors is that the vertical mattress technique had a bimodal distribution of perfusion levels. Their thought was that this technique is more operator-dependent. Since tension is applied perpendicular to the wound, perfusion can vary more from patient to patient or even stitch to stitch.
Now on to book 3 of the Stormlight Archive…
Sources
Wyles CC, Jacobson SR, Houdek MT, Larson DR, Taunton MJ, Sim FH, Sierra RJ, Trousdale RT. The Chitranjan Ranawat Award: Running Subcuticular Closure Enables the Most Robust Perfusion After TKA: A Randomized Clinical Trial. Clin Orthop Relat Res. 2016 Jan;474(1):47-56. doi: 10.1007/s11999-015-4209-x. PMID: 25733009; PMCID: PMC4686502.