BACKGROUND: Injections around the Achilles tendon (AT) are commonly performed in clinical practice to manage non-insertional Achilles tendinopathy, but the presence/distribution of the injectate with relation to its sheath has not been assessed specifically. Accordingly, the aim of this cadaveric investigation was to demonstrate the feasibility of Achilles paratenon injection under ultrasound guidance - by confirming the exact needle positioning as well as the dye distribution inside the paratenon lumen. METHODS: A descriptive laboratory study with three human cadaveric specimens (one fresh cadaver and two cadavers embalmed using the Fix for Life (F4L) method) was performed in a tertiary-care academic institution. The interventional technique and the related anatomical findings were illustrated. During the injection, the needle was advanced inside the Achilles paratenon under ultrasound guidance i.e. in-plane medial-to-lateral approach. With the objective to confirm its correct placement, the needle was kept in situ on the right AT of the fresh cadaver. Likewise, to demonstrate the location of the dye inside the lumen of Achilles paratenon, the other five ATs - four on the embalmed cadavers and one on the fresh cadaver - were injected with 5 mL of green color dye. After removal of the needle, a layer-by-layer anatomical dissection was performed on all three cadavers. RESULTS: On the right AT of the fresh cadaver, the position of the needle's tip within the Achilles paratenon was confirmed. Accurate placement of the dye inside the paratenon lumen was confirmed in four (80%) ATs, one of the fresh and three of the embalmed cadavers. No spread inside the crural fascia compartment or between the AT and the Kager's fat pad was observed. Herewith, unintentional spilling of the dye within the superficial soft tissues of the posterior leg was reported in the left AT of one of the two embalmed cadavers (20%). CONCLUSIONS: Ultrasound-guided injection using the in-plane, medial-to-lateral approach can accurately target the lumen of Achilles paratenon.

Department of Physical Medicine and Rehabilitation and Community and Geriatric Research Center National Taiwan University Hospital Bei Hu Branch Taiwan

Department of Rehabilitation and Sports Medicine 2nd Faculty of Medicine Charles University and University Hospital Motol Prague Czech Republic

Department of Rehabilitation Medicine 1st Faculty of Medicine and General University Hospital Charles University Prague Prague Czech Republic

Hacettepe University Medical School Department of Physical and Rehabilitation Medicine Ankara Turkey

Institute of Anatomy 1st Faculty of Medicine Charles University Prague Czech Republic

Physical and Rehabilitation Medicine Unit Luigi Sacco University Hospital ASST Fatebenefratelli Sacco Milan Italy

UZR Ultraschallzentrum und Institut für Rheumatologie Basel Switzerland; Rheumatology Clinic University Hospital of Basel Basel Switzerland

References provided by Crossref.org

Anatomy of the Achilles tendon-A pictorial review