The spread of Injectate after ultrasound-guided lateral elbow injection – a cadaveric study

Background Injections into the tendinous portion of the common extensor origin are a common intervention in the treatment of Lateral Elbow Tendinopathy (LET). Clinical trials report a heterogeneous selection of injectate volumes and delivery techniques, with systematic reviews finding no clear consensus. The aim of this study was to assess the intratendinous distribution and surrounding tissue contamination of ultrasound-guided injections into the Common Extensor Tendon (CET) of the elbow. Methods Twenty cadaveric elbows were injected by a Consultant Radiologist under Ultrasound guidance. Elbows were randomised to equal groups of 1 or 3 mls of methylene blue injection, delivered using single shot or fenestrated techniques. Following injection, each cadaver underwent a dry arthroscopy and dissection of superficial tissues. The CET was excised, set and divided into 1 mm sections using microtome. Each slice was photographed and analysed to assess spread and pixel density of injectate in four colour graduations. The cross-sectional area of distribution was calculated and compared between groups. Results In all 20 cadaveric samples, contamination of the joint was noted on arthroscopy and dissection. Injectate spread through over 97% of the cross-sectional area. No differences were found in intratendinous spread of injectate between differing volumes or techniques. Conclusion This study found that commonly used injection volumes and techniques distribute widely throughout cadaveric CETs. There was no improvement when the volume was increased from 1 to 3 mls or between single shot of fenestrated injection techniques. It should be noted that joint contamination using these techniques and volumes may be inevitable.