BackgroundPrevious reports have observed differences only in infection rates between posterolateral fusion and posterior lumbar interbody fusion (PLIF). There have been no reports that describe the particular features of surgical site infection (SSI) in PLIF. In this study, we endeavor to identify the distinguishing characteristics and risk factors of SSI in PLIF.MethodsOur study undertook a review of a case series of an institute. Patients who had undergone PLIF consecutively in the author's hospital were reviewed. Two proactive procedures were introduced during the study period. One was irrigation of the autolocal bone, and the other was the intradiscal space irrigation with a nozzle. Infection rate and risk factors were analyzed. For subgroup analysis, the elapsed time to a diagnosis (ETD), clinical manifestations, hematologic findings, and causative bacteria were examined in patients with SSI.ResultsIn a total of 1,831 cases, there were 30 cases of SSI (1.6%). Long operation time was an independent risk factor (p = 0.008), and local bone irrigation was an independent protective factor (p = 0.001). Two cases of referred SSI were included in the subgroup analysis. There were 6/32 (19%) superficial incisional infections (SII), 6/32 (19%) deep incisional infections (DII), and 20/32 (62%) organ/space infections (O/SI). The difference of incidence among three groups was significant (p = 0.002).The most common bacteria encountered were methicillin-resistant Staphylococcus epidermidis followed by methicillin-resistant S. aureus in incisional infections, and no growth followed by S. epidermidis in O/SI. ETD was 8.5 ± 2.3 days in SII, 8.7 ± 2.3 days in DII and 164.5 ± 131.1 days in O/SI (p = 0.013).ConclusionsThe rate of SSI in PLIF was 1.6%, with the most common type being O/SI. The causative bacteria of O/SI was of lower virulence than in the incisional infection, and thus diagnosis was delayed due to its latent and insidious feature. Contamination of auto-local bone was presumed attributable to the progression of SSI. Irrigation of auto-local bone helped in the reduction of SSI.

Background Epidural hematoma is a rare but serious complication. According to previous studies, it is not prevented by suction drains. This study evaluated the following alternative hypothesis: the larger the diameter of a suction drain, the less the remaining epidural hematoma after spinal surgery. Methods This was a randomized prospective study. Patients who underwent posterior lumbar decompression and instrumented fusion were divided into two groups: the large drain (LD, 2.8-mm-diameter tube) and small drain (SD, 1.6-mm-diameter tube) groups according to the diameter of the suction drains. All patients were consecutive and allocated alternately according to the date of operations. Suction drains were removed on day 3 and magnetic resonance imaging was performed on day 7 postoperatively. The size of remaining hematomas was measured by the degree of thecal sac compression in cross section using the following 4-point numeric scale: G1, less than one quarter; G2, between one quarter and half; G3, more than half; and G4, more than subtotal obstruction. Results There were 39 patients with LDs and 38 with SDs. They did not differ significantly in terms of sex, number of fusion segments, revision or not, antiplatelet medication, intraoperative injection of tranexamic acid. However, patient age differed significantly between the two groups (LD, 63.3 years and < SD, 68.6 years; p = 0.007). The two groups did not differ significantly in terms of prothrombin time, activated partial thromboplastin time, platelet number, blood loss, or operation duration. However, platelet function analysis exhibited a significant difference (LD, 164.7 seconds and < SD, 222.3 seconds; p = 0.002). The two blinded readers showed high consistency (Kappa value = 0.740; p = 0.000). The results of reader 1 were as follows: LD and SD had 21 and 21 cases of G1, 9 and 11 cases of G2, 6 and 6 cases of G3, and 3 and 0 cases of G4, respectively. The results of reader 2 were as follows: LD and SD had 22 and 23 cases of G1, 7 and 9 cases of G2, 7 and 6 cases of G3, and 3 and 0 cases of G4, respectively. There was no difference between the two groups (reader 1, p = 0.636; reader 2, p = 0.466). Conclusions The alternative hypothesis was rejected. Therefore, postoperative spinal epidural hematoma would not be prevented by LD.

Spine surgery is increasing in frequency in the elderly population with osteoporosis along with the increased life expectancy. In addition to osteoporosis, deformities that demand rigid fixation are frequently observed in elderly patients. However, it is not easy to achieve enough fixation strength even with a pedicle screw system in such patients.

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