The accuracy of an injection technique for Flexor hallucis longus tendon sheath: A cadaveric study

Background: Corticosteroid injections are used in the conservative treatment of Flexor hallucis longus (FHL) tendinopathy. Studies for imaging guided injection are done, however, the accuracy of blind injection has not yet been studied. Purpose: The aim of this study was to determine the accuracy of a blind injection technique into the FHL tendon sheath. Hypothesis: We hypothesize that a blind injections technique into the FHL tendon sheath based on clinical examination has a high accuracy. Study design: Descriptive cadaveric study. Methods: Ten ankles of human cadavers were blindly injected with radiologic contrast mixed with methylene blue into the FHL tendon sheath. After injection, a CT scan of each ankle was performed to evaluate the location of contrast material. CT scans were reviewed by an experienced musculoskeletal radiologist blinded to the procedure. Anatomic dissection was undertaken to assess the location of the injection fluid. Results: In nine ankles the radiological contrast was injected in the FHL tendon sheath. In one cadaver there was a technical problem and was therefore excluded. Conclusion: This study shows that the FHL tendon sheath can be blindly injected based on only clinical examination with high accuracy. Level of evidence: Descriptive cadaveric study.