Radiographic Landmarks for Ideal Port Placement in Wrist Arthroscopy

Background  The placement of wrist arthroscopy portals is traditionally performed using distances from anatomic landmarks. We sought to evaluate the safety of traditional portal placement and determine if radiographic landmarks could provide an additional method of identifying tendon intervals. Methods  Six cadaveric specimens were used to evaluate the accuracy of portal placement based on anatomic and radiographic landmarks. Fluoroscopic images were used to document the location of previously described surface landmarks. Soft tissue was dissected away to identify the relationship between the transcutaneously placed portals and the extensor tendons. With soft tissue removed, tendon intervals were identified in relationship to anatomic carpal bone landmarks, and interval distances measured. Portals were then placed under radiographic imaging on the final three specimens and accuracy was examined by the removal of overlying soft tissue to confirm accurate interval placement Results  The 3,4 portal was safely placed using only surface anatomic landmarks, however the 4,5 and midcarpal ulnar (MCU) portal sites were not consistently placed in the intended tendon interval, especially in larger wrists. Radiographic interval targets for the 3,4 portal were identified at the ulnar aspect of the scaphoid and the 4,5 portal at the ulnar one-third of the lunate. The radiographic site for the MCR was located at the inferior radial one-third of the capitate and the MCU portal was located at the radial aspect of the hamate. The 6R portal radiographic landmark is at the radial aspect of the triquetrum and 6U at the ulnar aspect of the triquetrum. Conclusion  Portal placement in wrist arthroscopy based on anatomic landmarks alone can be unreliable in larger wrists. Radiographic imaging based on carpal bone landmarks provides an additional tool for consistent placement of portals in wrist arthroscopy and may limit unintended injury to extensor tendons. Level of Evidence  This is a Level VI study.