The authors present the results of the first retrospective study investigating the differences between primary and postoperatively acquired spondylodiscitis. Survival rate was significantly higher in patients with postoperative spondylodiscitis. MRI remains the most sensitive and specific imaging modality to detect spondylodiscitis and the infection of the adjacent tissue . Epidural and paraspinal abscess and vertebral bone destruction was more severe in primary spondylodiscitis. Surgical treatment accompanied by broad-spectrum antibiotics resulted in significant reduction of overall pain and inflammatory blood values 12 months after surgery. No significant pain decrease could be detected in conservatively treated patients 3 months after the first diagnosis.
Infective spondylodiscitis can result in disc destruction, pathological fractures and abscess formations. A spinal epidural abscess is an infection involving the epidural space and has a high mortality rate . Once a rare diagnosis carrying a poor prognosis, its incidence is rising dramatically. The development of an epidural abscess may be associated with various risk factors, such as advanced age over 65 years, immunocompromized state, smoking or diabetes mellitus. Furthermore, intravenous drug abuse has been associated with a high prevalence of epidural abscess commonly due to hematogeneous bacterial spread [6–9]. Drug abuse was more common in the patients who developed a primary spondylodiscitis. This could be a fundamental reason for the higher occurrence of epidural abscess in these patients and particularly for the higher mortality rate that is closely associated to infections with abscess formation [3, 10].
An epidural abscess may be associated with significant bone destruction resulting in instability and deformity of the spine . In our study group, a significant correlation could not be shown, whereas a paraspinal abscess may induce vertebral bone loss. Instability establishes a major risk factor for developing a potentially neurological impairment. Then early surgical stabilization is insistently recommended to preserve neurological function . Furthermore, vertebral bone destruction was more severe in primary spondylodiscitis, whereas differences in disc destruction did not occur between the two groups .
The most common causative organism in spondylodiscitis is Staphylococcus aureus which is responsible for widespread bone loss and bone destruction [13, 14]. Additionally, an increased long-term mortality rate, mainly due to sepsis, is reported in adult patients suffering from Staphylococcus aureus spondylodiscitis . Thus, early surgical debridement is obtained to reduce the bacterial load and improve the antibiotic efficacy, especially in multiresistant Staphylococcus aureus infection . Further causative organisms have been described and increased over the last few years, especially gram-negative bacteria. An important cause is the use of routine use of prophylactic antibiotics after spinal surgery . Nevertheless, the pathogen that is responsible for spondylodiscitis can only be identified in approximately 35 to 50% of cases [17, 18]. In our retrospective series the pathogen could only be detected in 26% of blood culture and 39% of intraoperative smear test samples. This may be due to the fact that broad spectrum antibiotics have been applied in our outpatient clinics before a spondylodiscitis could be diagnosed accurately.
Surgery is indicated for neurological impairment, deformity, instability, medical intractable pain, and disease progression [19, 20]. The surgical goals are the debridement of infection, identification of pathogens, decompression of neuronal structures, and stabilization of deformed and instable segments. Depending on the location and extent of infection, various treatment options for spondylodiscitis are available. There is still controversy regarding the most adequate surgical approach [20–24]. Nevertheless, fusion is recommended in discitis with involvement of endplates of the vertebral body, whereas in intraspinal empyema dorsal decompression and evacuation alone may be sufficient . Significant differences occurred in the extent of operative procedures in our study group. A higher spread of infection resulted in a more aggressive surgery. Cervical and thoracal corpectomy was performed more frequently in patients with primary spondylodiscitis. A minor part of patients were treated with debridement only because spondylodiscitis with liquefaction of endplates was present in over 90% of patients. Furthermore, patients who already had surgery were presumably screened earlier for spondylodiscitis as their counterparts. This may due to the fact that these patients are followed up routinely after their surgical treatment and therefore infection may be detected earlier in the infectious cascade.
In conclusion spondylodiscitis is a life-threatening and serious disease and requires long-term treatment. Our retrospective analysis demonstrates a significantly higher mortality rate in patients with primary spondylodiscitis. Primary spondylodiscitis is frequently associated with epidural and paraspinal abscesses and vertebral bone destruction. Thus, it seems that primary spondylodiscitis shows a more severe course than spondylodiscitis following spine surgery. Nevertheless, with current standards, prospective clinical trials will be mandatory to better understand the pathogenesis of spondylodiscitis and furthermore develop evidence-based treatment recommendations for these patients.