Sécurité de l’injection à travers la peau dorsale dans le traitement du doigt et du pouce à ressaut: étude anatomique

Corticosteroid injection is an effective treatment for trigger digits but the pain during the injection is an always-present side effect. Our purpose was to assess if a dorsal technique through the web space is safe for extra-sheath injection of trigger fingers and thumb. Twelve fresh-frozen cadaveric upper extremities were used in this study consisting in six white males and six white females. The mean age was 83 years (range: 70–96). Specimens had no history of trauma, surgery or regional pathology that could affect the results obtained in the study. An injection through the dorsal web was performed on each digit. After a 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. The mean distance from the needle to the neurovascular bundle was 1.63 millimeters and it was over one millimeter in all digits. Two major injuries in 84 injections were observed, one nerve and one artery. The safest digit was the thumb while the most dangerous was the index finger. At the middle and fourth fingers, the technique was safer when it was carried out from the dorso-ulnar side. The palmar midline injection into the synovial sheath is the most widely used technique but, according to several authors, the palmar skin has a high density of sensitive receptors than the dorsal skin so it tends to create more patient discomfort. An intra-sheath technique through the dorsal skin has been previously published in one paper (Buch-Jaeger and Foucher, 1992) reporting similar results to those described for other techniques. Some studies have demonstrated that injecting into the flexor tendon sheath is not necessary, since similar outcomes have been achieved with a palmar subcutaneous injection. Therefore, a technique through the dorsal skin could be an effective and less painful alternative in the treatment of trigger digits. To the best of our knowledge, no studies have been published reporting a dorsal extra-sheath technique. A subcutaneous injection near the flexor tendon sheath can be carried out through the dorsal web with an acceptable risk of neurovascular injury and it could be useful for injection in the treatment of trigger fingers and trigger thumb but it should be assessed in a clinical study.