Background: 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.
Methods: 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.
Results: 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.
Conclusions: Six-pin halo fixation results in greater
halo strength and cervical spine stabilization without increasing
the risk of pin-site complications.
Clinical Relevance: 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.