Background: Since high incidences of serious complications like death and pneumonia during halo vest immobilization (HVI) have been reported in recent literature, a tendency of restraint in using the halo vest is rising. Nevertheless, most of these studies were small-scale retrospective reports. The real incidence of complications in a highvolume center with sufficient experience is unknown. It was our objective to determine incidence and risk factors associated with complications during HVI prospectively.

Methods: During a 5-year period a prospective cohort study was performed in a single level-I trauma and spinal disorders center. Data of all traumatic and non-traumatic patients who underwent HVI were prospectively collected. Every complication during follow-up, i.e. the period of HVI, was recorded. Primary outcome was presence or absence of complications. Statistical significance of relations between 30 covariates and primary outcome was determined with Chi-square analysis.

Results: In 239 patients treated with HVI 26 major, 59 intermediate and 132 minor complications were observed. Fourteen patients (6%) died during the treatment, although only three were possibly related directly to the immobilization. Increasing age (p=0.005) was the only risk factor significantly related to mortality during HVI. Patients over the age of 70 were especially at risk (p=0.002). Twelve patients (5%) acquired pneumonia during HVI. Halo related complications ranged from 3 patients (1%) with incorrect initial assembly of the halo vest to 29 patients (12%) with pin site infections. Both pin site infection (p=0.003) and pin loosening (p=0.021) have been identified as significant risk factors in development of pin site penetration.

Conclusions: Compared to previous retrospective reports, we found a lower percentage of mortality and pneumonia during HVI. Nevertheless, the numbers of minor complications remain substantial. This study confirms that awareness and responsiveness to minor complications can prevent subsequent development of serious morbidities and reduce mortality, while it is the first prospective report to identify risk factors for the development of complications during HVI.