Reattachment of avulsed ligaments with AO screw and toothed washer. A, Fixation of avulsed ligament, with or without bony fragment. B, Washer is designed so that it grips ligament and bone over broad area with its peripherally arranged teeth, compressing and fixing them within limits designed by a stop on each tooth. Little pressure is exerted on tissue next to and between teeth. Microcirculation in these areas of ligament is normal; it is compromised only in compressed area represented by solid trapezoids.