Dorsal web injection technique in the treatment of trigger finger and trigger thumb. Anatomical study

Background Corticosteroid injection is an effective treatment for trigger digits but the pain during the injection is an ever-present side effect. Since the palmar skin has a high density of sensitive receptors, injecting through dorsal skin could be less painful. Our aim was to assess whether a dorsal technique through the dorsal web is safe for extra-sheath injection of trigger fingers and thumb. Material and method This is an anatomical study in sixteen cadaveric hands. An injection through the dorsal web was performed on each digit. After careful resection of the palmar skin, the distance between the needle and the main anatomical structures was measured. The risk of major injury was considered high when the mean distance from the needle to the neurovascular bundle was below one millimeter. Results The mean distance from the needle to the neurovascular bundle was 1.77 mm. Two neurovascular injuries in 112 injections were observed, one nerve and one artery. The safest digit was the thumb while the most dangerous was the index finger. At the ring finger, the technique was safer when it was carried out from the dorso-radial. Conclusions A subcutaneous injection near the flexor tendon sheath can be carried out through the dorsal web with a low, but present, risk of neurovascular injury. It could be useful for injection in the treatment of trigger finger and trigger thumb but it should be assessed in a clinical study.