Introduction
In recent years, good results of early surgery for pyogenic spondylitis have been reported. However, there are many unknowns regarding the insertion of screws into infected vertebrae. This study aimed to investigate the outcomes of posterior fusion surgery with and without screw insertion into the infected vertebrae.
Method
Thirty-seven patients (mean age 69.7 years) of pyogenic spondylitis treated in our hospital between 2017 and 2023, 27 patients (21 males and 6 females) were included. Ten patients of non-fusion procedures such as decompression and drainage were excluded. We examined various parameters, including operative time, blood loss, number of fixed vertebrae, preoperative C-reactive protein (CRP) levels, postoperative CRP levels at 2 weeks, days to initiate ambulation, follow-up period, and occurrences of screw removal and loosening. The study subjects were categorized into two groups: those with screw insertion (group A) and those without (group B). Statistical analysis was performed using a t-test, with p<0.05 considered as a significant difference.
Result
The mean follow-up period was 27.7 months in group A and 20.2 months in group B (p=0.582). A significant difference was observed in the mean number of fixed vertebrae (group A/group B: 3.7/5.2, p=0.013). The mean operative time was 155 minutes in group A and 201 minutes in group B (p=0.013), while the mean blood loss was 157 ml in group A and 219 ml in group B(p=0.074). Preoperative CRP and 2 week postoperative CRP ranged from 3.26 to 6.21 in group A and from 5.96 to 4.81 in group B (p=0.179, p=0.763). The number of days to start ambulation was 2.9 days in group A and 8.0 days in group B (p=0.089). Ultimately, 11 patients (6 in group A and 5 in group B) underwent screw removal. Among them, six patients had screws removed due to no loosening, while five patients had screws removed because of loosening, coupled with bone bridging.
Discussion
In the group with screw insertion into the infected vertebrae, the number of fixed vertebrae was significantly lower compared to the non-insertion group. Moreover, operation time, blood loss, and the time to initiate ambulation were also reduced, although there was no difference in the final follow-up between the two groups. Screw insertion into the infected vertebrae resulted in a shorter immobilization range compared to the non-insertion group, potentially contributing to a quicker initiation of bed rest. Considering the appropriate timing of surgery and the condition of the infected vertebrae when selecting cases, screw insertion may not adversely impact the treatment’s effectiveness.