Cadaveric study comparing the stability of upper distraction hooks used in Harrington instrumentation

Many different designs of upper distraction hooks for use in Harrington instrumentation are available. There is no published evidence to date to support the use of one hook in preference to another. This study compares the distraction force required to dislodge the three most commonly used designs of Harrington upper distraction hook. In cadavers the force required for failure of the plain, ribbed, and bifid hooks was compared as were the modest of vertebral fracture at the time of cut out. The bifid hook required a significantly greater distraction force to fracture the lamina, and the pattern of fracture was more extensive than it was with the plain or ribbed hooks.