Techniques for Injection of the Scaphotrapezium-Trapezoid Joint Without Image Guidance

Purpose Scaphotrapezium-trapezoid (STT) joint arthritis is one of the most common forms of wrist arthritis. Conservative management often involves corticosteroid injection. Despite this, there is a scarcity of literature on palpation-guided injection techniques for the STT joint. We aimed to determine a standardized palpation-guided injection method that is easily reproducible and poses minimal risk to local anatomic structures. Methods Six fresh-frozen cadaveric upper extremity specimens were tested. Access to the STT joint was attempted with dorsal, volar, and radial approaches. Fluoroscopy was used to confirm accurate placement within the joint. Needle placement was documented in relation to the surrounding soft tissue and bony landmarks were measured with a ruler, and the angle of the needle entry was recorded using a goniometer. The cadavers were carefully dissected to identify the surrounding neurovascular structures at risk of injury. Results To access the STT joint with the dorsal approach, the needle was angled at 90o and inserted one-third of the distance from the prominence of the base of the second metacarpal to Lister tubercle. No neurovascular structures were found in the immediate vicinity of the needle. For the volar approach, the needle was angled at 65o and inserted at the distal wrist crease, 1 cm ulnar to the radial border of the wrist, in line with the second metacarpal. The volar branch of the radial artery was at risk with this approach. For the radial approach, the needle was angled at 60o and inserted immediately dorsal to the extensor pollicis brevis tendon, midway between the radial styloid and the prominence of the thumb metacarpal base. The dorsal branch of the radial artery was at risk with this approach. Conclusions In a clinical setting where fluoroscopy or ultrasound is not readily available, the dorsal approach may allow for safe and accurate placement of the injectate into the STT joint. Type of study/level of evidence Therapeutic IV.