Safety of dorsal screw penetration at the proximal holes of volar locking plates

Tendon-related complications comprise a significant portion of overall complications following volar locked plating of distal radius fractures. While much is known about the effect of prominent hardware in the volar and dorsal metaepiphyseal region of the distal radius, less is known about the effect of hardware prominence in the dorsal meta-diaphyseal region. The purpose of this anatomic study was to evaluate the safety of dorsal screw penetration at the proximal holes of volar locking plates. We applied a 7-hole volar locking plate to the distal radius of 10 cadaver forearms. Screws were intentionally protruding on the dorsal side. Measurements were taken from each protruding dorsal screw-tip to the nearest point on the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor digitorum communis, noting whether the nearest point was on the tendon or muscle belly. Results indicated that the muscle bellies of the abductor pollicis longus and extensor pollicis brevis were the structures most at risk from dorsal screw prominence, and that there was a smooth transition from the extensor pollicis brevis to abductor pollicis longus being the focus of risk as one moves from distal to proximal along the plate. The extensor pollicis brevis was most at risk at hole 3, and the abductor pollicis longus was most at risk at hole 6. All cases of direct contact between a protruding screw and the abductor pollicis longus or extensor pollicis brevis consisted of contact with the muscle belly, not the tendon. Average anteroposterior distal radius thickness ranged from 13.9 mm at the most distal proximal screw hole to 11.5 mm at the most proximal screw hole. We also found that the extensor pollicis longus tendon was at risk of contact with a protruding screw, but only at the most distal proximal screw hole. Overall, dorsal screw penetration at the proximal holes of volar locking plates appeared to be safe, particularly as one moves proximally along the plate.