MECHANICAL EVALUATION OF 4-PIN VERSUS 8-PIN HALO FIXATION

Fixation of the halo device in the skulls of young children is sometim es compromised because of a thinner cortex and the increased jarring a nd trauma that small children experience during their everyday activit ies of life at that age. To assess the increased fixation that an eigh t-pin halo fixation would provide over the more standard four-pin fixa tion, the stiffness of fixation of a halo orthosis was evaluated in fo ur dried human cadaver skulls. Two different fixation systems were use d: the first one with four pins in the standard locations and the seco nd with four additional pins. A compressive force was applied to the h alo ring at a constant rate of 1.27 mm/min. Load and deflection data w ere recorded simultaneously until a force of 400 N was reached. Result s for the two-pin systems were analyzed and compared statistically by using paired t tests. Statistically significant differences were estab lished between the two sets of results with the 8-pin system providing an increase of 24.2% in the stiffness of fixation.