In general, it is not easy to treat pyogenic lumbar discitis. The basic principle of the treatment is to conduct a non-surgical treatment where a conservative treatment based on the appropriate administration of antibiotics is conducted. However, based on the fact that providing stability to osteomyelitis (which occurred in the long bone), using metal was effective in inflammation control [15
], studies have been conducted to provide stability to the treatment of pyogenic spondylitis, and to achieve early ambulation via a posterior approach. As a result, some studies [16,17
] have reported good outcomes.
As the direct insertion of a metal implant into the infected site may cause deterioration or recurrence of the infection in the treatment of musculoskeletal infectious disease, it has been contraindicated to date. Bacteria have been known to attach to the surface of an artificial implant located at the inflammatory tissues, and form a biofilm [18
]. Such biofilm formation has been known to cause the persistence of the infection by blocking the antibiotic approach. However, in recent years, direct fixation following the complete debridement of the lesions of tuberculous spondylitis and pyogenic discitis has been conducted and this method was reported to be effective and did not increase the risk of infection recurrence in the treatment of vertebral inflammation [2,19
]. As internal fixation is located at the cancellous bone with abundant blood flow, bacterial growth is expected to be inhibited if the drainage of common bacteria including Staphylococcus aureus
via complete debridement prior to biofilm formation is performed together with an antibiotic approach.
In general, pyogenic and tuberculous spinal infection invade the anterior vertebral region [20
]. Accordingly, if a conservative treatment does not work, anterior fusion using the tricortical autograft following anterior drainage of the infected site and necrotic tissue debridement has been used as a common surgical treatment [21,22
]. Safran et al. [19
] and Krödel et al. [23
] reported that anterior debridement and posterior fixation were effective in the treatment of lumbar osteomyelitis. Park et al. [21
] reported the result of the treatment of tuberculous spondylitis via anterior debridement, anterior fusion and anterior fixation.
If debridement without internal fixation is conducted in an anterior approach, long-term bed rest or a body cast, or a surgery via an additional posterior approach are required. If anterior metal fixation is conducted via an anterior approach, it has a risk of recurrence due to the metal present in the lesion [6
]. In addition, the anterior approach may cause complications such as injuries of gastrointestinal or urinary tissues due to neurogenic injury, hernia, and the adhesion of infected perispinal tissues [6
]. Furthermore, it is difficult to access the lower lumbar inflammation that occurred in L5-S1 via the anterior approach. If an abscess or spinal deformity is observed in the posterior dura, a posterior surgery is additionally required.
Posterior pedicle screw fixation has advantages of early ambulation and early rehabilitation due to rigid fixation, and the partial correction of lumbar lordotic angle loss caused by bony destruction due to inflammation into the normal lordotic angle [6,16,17,24
]. In addition, as pyogenic discitis frequently occurs in elderly patients with decreased immunity, concurrent spinal stenosis frequently occurs. In such cases, spinal stenosis can be surgically treated via posterior debridement [6
]. Although relatively fewer studies on lumbar interbody fusion and pedicle screw fixation in the treatment of lumbar osteomyelitis have been conducted, Przybylski and Sharan [16
], Rath et al. [17
], and Park et al. [6
] conducted autologous bone graft following posterior debridement via posterior approach alone, and then conducted posterior pedicle screw fixation in the treatment of pyogenci discitis via posterior approach alone, and reported that good outcomes were obtained.
Among the patients with pyogenic lumbar discitis who were not treated with 3-week or more antibiotic administration, 15 patients who had a relatively smaller amount of abscess present in the anterior vertebral body, who had concurrent spinal stenosis, or who had a posterior epidural abscess, were selected as subjects for posterior lumbar interbody fusion.
In conventional pyogenic and tuberculous discitis, surgery using the autologous bone has been mainly conducted. In the case of fusion using the autologous bone, it has an advantage of an increased ratio of bony fusion, but has disadvantages of the occurrence of pain and hemorrhage of the donor site after harvesting the autologous bone [25,26
]. Accordingly, unlike conventional treatments of pyogenic discitis that focus on autologous bone graft, in this study, allograft transplantation alone or bone graft with both the allogenic bone and the autologous bone were conducted on the intervertebral disc space formed after debridement. Previous studies have reported that the allogenic bone was used instead of the autologous bone in the treatment of osteomyelitis that occurred in the long bone [27
]. O'Brien et al. reported that a good outcome was obtained when the femoral cortical allogenic bone was used with the autologous bone in lumbar interbody fusion, and that it could be an ideal method for bone graft [9,10
]. Bendo et al. [28
] conducted anterior lumbar interbody fusion where the femoral head was used as the allogenic bone, and reported that easy revascularization promoted creeping substitution, a straightforward change of the intervertebral disc type, and the maintenance of the height of the disc interval.
Raut et al. [29
] reported that a high treatment rate of 86% was obtained from artificial joint replacement conducted again after the complete removal of the infected soft and bony tissues, following the complete removal of internal structures such as metal and polyethylene via a single re-surgery in artificial joint replacement conducted on the deeply infected tissues. They emphasized that the complete removal of the infected tissues rather than the number of surgeries was critical for the successful treatment of infection. Thus, this factor should be considered in the treatment of pyogenic discitis.
As allograft transplantation does not require an additional surgery to harvest the autograft in elderly patients with decreased level of immunity, particularly those with poor general conditions, it can help to shorten operation time, reduce the amount of bleeding, and avoid complications occurring in the donor site. Despite the superiority of the autograft in inflammation treatment, the complete removal of dead tissues via debridement is considered a more important factor determining prognosis.