Six-pin halo fixation and the resulting prevalence of pin-site complications

In spite of the many advances in halo application technique, the prevalence of complications associated with the use of halo fixation remains high, particularly at the pin sites. Many practitioners do not use more than four pins for halo application in adults because they believe that it increases the risk of complications. The purpose of this study was to investigate the use of six pins in halo application, in order to determine if the extra pins increased fixation strength without increasing the overall pin-site complication rate.

The first part of our study consisted of force-deflection tests conducted on models of the skull fitted with either a four or a six-pin halo to determine if the six-pin halo provided greater fixation strength. Each skull model was placed in a servocontrolled hydraulic test machine; an axial distraction force was then applied until failure occurred. The second part of the study was a retrospective analysis of sixty-three patient records to document the prevalence of pin-site complications in patients treated with a six-pin halo system; these findings were then compared with established complication rates associated with four-pin halos.

In the force-deflection tests, the mean load to failure of the six-pin halo construct (2879 N [647 lb]) showed the system to be significantly stronger (p = 0.0033) than the four-pin halo construct (1681 N [378 lb]). Of the sixty-three patient records reviewed, five (8% [95% confidence interval, 1% to 15%]) revealed pin-loosening; no infection was recorded for these five patients. One of the sixty-three patients had redness and erythema at "multiple sites," but these areas healed well. Another presented with infection at all six sites; this was recorded as an allergic reaction.

Six-pin halo fixation results in greater halo strength and cervical spine stabilization without increasing the risk of pin-site complications.

Our findings are relevant for current clinical practice as the high complication rates associated with halo application have deterred some practitioners from using this type of fixation. The use of six pins, along with an improved protocol for halo application and care, may contribute to a more successful treatment outcome with fewer complications.