Unrecognized chondral penetration by a Herbert screw in the scaphoid.

The Herbert bone screw as developed by T. Herbert in the early 1980s has been used in the treatment of scaphoid fractures and nonunions. Reports on clinical efficacy have been accompanied by discussions of technical difficulties. This study determines if the curvilinear surface of the proximal pole of the scaphoid leads to errors in screw length and penetration into the joint. The screw was inserted in cadaveric wrists using the technique described by Herbert. Plain x-ray films were taken in the anteroposterior and lateral planes and fluoroscopy was used through 360 degrees. From the imaging studies, we decided whether subchondral penetration of the screw had occurred. The scaphoids were then dissected and the dorsal poles inspected. In our six specimens, two screws were found to be penetrating subchondral bone. The plain x-ray films were accurate in five of six specimens. Fluoroscopy was accurate in all six. Fluoroscopy during placement of the Herbert screw may decrease the rate of subchondral penetration.