Twelve patients (54.5 %) presented acutely, while ten patients (45.5 %) had chronic infection (Table 1). Marked weight loss was reported by two patients (9.1 %). At time of admission, coinciding infection was found in 11 cases (50 %), of which 6 cases were spondylodiscitis and 1 case was epidural abscess. Eight patients had received antimicrobial therapy.
Radiographs were done preoperatively in all patients. In the acute stage of non-specific infections it appeared to be normal, while in chronic cases it showed blurring of the outlines of the sacroiliac joint, widening of the joint space, periarticular osteopaenia, sclerosis and erosion of the joint margins. MRI was done preoperatively for all patients. It demonstrated abscess formation in the piriformis, iliacus, gluteus or iliopsoas muscle as well as inflammatory signal changes in the surrounding soft tissues. Anterior capsule may be stretched or damaged. Other findings included: bone oedema, soft tissue infiltration and myositis. CT was done preoperatively in nine cases with chronic infection and showed joint space widening, sclerosis of the margins of the joint, cavitations and sequestrum formation (Tables 2, 3).
In tuberculous infection, mean values were as follows: C-reactive protein (CRP) of 57.44 ± 38.39 mg/dL, erythrocyte sedimentation rate (ESR) of 72 ± 31.17 mm/h and white blood cell (WBC) count of 7,440 ± 3,729/mm3. Postoperatively, the mean CRP was 22.86 ± 16.54 mg/dL, ESR was 48.2 ± 19.24 mm/h and WBC was 7,600 ± 3,410/mm3 (Table 3). In non-specific infection, the mean CRP was 122.52 ± 84.74 mg/dL, ESR was 81.12 ± 24.32 mm/h and WBC was 10,329.4 ± 4,343/mm3, while postoperatively CRP was 22.69 ± 19.92 mg/dL, ESR was 46.65 ± 24.29 mm/h and WBC was 8,552.9 ± 5,012/mm3 (Table 2). The change was statistically significant for CRP and ESR (p < 0.001 and = 0.001, respectively), while in WBC the difference was nonsignificant (p = 0.082).
Eleven cases (50 %) were subjected to debridement only, while debridement and arthrodesis was needed in the other 11 cases. Two patients required revision because of recurrent infection (after complete healing); one was posteriorly debrided for the second time, and one had attempted fusion through anterior approach and was reoperated with a stand-alone cage; i.e. this study included 24 surgeries in the 22 reviewed patients (Table 4). The mean operative time for debridement without fusion was 35 min for posterior approach, 62.5 min for anterior approach and 83.33 min for combined anterior and posterior approaches, while in debridement and fusion it was 85, 131 and 160 min, respectively (Fig. 1).
The causative organism was Mycobacterium tuberculosis in 5 cases (22.7 %), Staphylococcus aureus in 12 cases (54.5 %) and Enterococcus faecalis in 1 case. In four cases, no organism was isolated (Table 4).
The postoperative immobilisation period depended on the general condition of the patient and the operative technique. Postoperative treatment included culture-based antimicrobial therapy or broad-spectrum antibiotic therapy when no organism was isolated (Table 4).
Functionally, eight patients had excellent results (40 %), five good (25 %), three fair (15 %) and four poor (20 %) (Table 4).
Sound fusion was achieved in ten cases (50 %) within the first year after surgery; in the other ten cases, no signs of fusion were found in final radiographs.
Complications included recurrence of infection in two cases, delayed wound healing in three cases and chronic pain in three cases.