The incidence and risk factors of surgical site infection in micro endoscope-assisted posterior lumbar interbody
fusionAyako Itoh1, Ayako Kudo2, Kazumi Kawakami2, Keita Nishimura3, Yuichi Takano1, Hirohiko Inanami4
Iwai Orthopaedic Medical Hospital, Tokyo, Japan, 2Juntendo University Graduate School of Health Care and Nursing, Chiba, Japan,
3
Department of Orthpaedic Surgery, Teikyo University School of Medicine, Tokyo, Japan, 4Inanami Spine and Joint Hospital, Tokyo, Japan,
1Disclosures: A. Itoh (N), A. Kudo (N), K. Kawakami (N), K. Nishimura (N), Y. Takano (N), H. Inanami (N)Introduction:
Consistent with the aging of our society, lumbar interbody fusion surgeries using endoscopes are becoming popular because their minimal
invasiveness is suitable for aged patients. Nevertheless, risk factors for surgical site infection (SSI) after such minimally invasive surgeries have been
unknown. Based on these backgrounds, we focused on micro endoscope-assisted posterior lumbar interbody fusion (ME-PLIF) surgery. Namely, the aimof the present study was to clarify the SSI rate and the risk factors after ME-PLIF surgery.
Materials and methods:
The study design was a retrospective cohort study with quantitative analysis, which set SSI event as an endpoint. The study was approved by the localethics committees.
Enrolled in this study were 1,128 cases which underwent ME-PLIF in a hospital from November in 2008 to May in 2015 (M/F: 595/533, age:64.0±12.5 years). SSI surveillance was performed in each case. And the rate of SSI incidence and the risk factors for SSI were investigated. For statisticalanalysis, the data were divided into 2 groups with incidence of SSI (SSI (+) and SSI (-) groups). Comparison between the continuous variables was carriedout using Mann-Whitney U test or Fisher’s exact test. To select the variables that were relevant to SSI incidence, a stepwise regression analysis wasperformed. Statistical significance was set at p <0.05.
Results:
SSI were observed in 9 cases (0.79%), of which all were categorized in organ/space SSI (Table). Univariate analysis demonstrated the risk factors as
follows: age, gender, diabetes complication, ASA-PS classification, preoperative C-reactive protein (CRP) level, percentage of lymphocyte(%lymphocyte) at day 7 after the surgery, and white blood cell (WBC) count, CRP, %lymphocyte and serum albumin level at first visit to the hospital afterdischarge. Multivariate analysis, subsequently, demonstrated the details: age (OR 6.69; 95％CI 1.37–32.81; p<0.05), diabetes (OR 4.12; 95％CI1.06–15.93; p<0.05), and CRP at first visit after discharge (OR 2.22; 95％CI 1.54–3.20; p <0.001). In cases aged more than 70 years old by stratification,
univariate analysis in 436 cases showed the risk factors were gender, diabetes, smoking history, past surgical history in the same vertebral body, ASA-PS
classification, and WBC and CRP levels at first visit after discharge. And multivariate analysis showed diabetes (OR 7.24; 95％CI 1.24–42.33; p<0.05),
smoking history (OR 17.63; 95％CI 2.89–107.60; p<0.01), past surgical history in the same vertebral body (OR 9.41; 95％CI, 1.48–60.02; p<0.05), andASA-PS classification (OR 8.61; 95％CI 1.47–50.37; p<0.05).
Discussion:
SSI rates, 0.7-11.9%, have been reported in previous studies on open lumbar interbody fusion surgeries [1]. The SSI rate obtained from this study was0.79%, which might be considered to be relatively lower than those in open surgeries. In addition, elder patient, male patient, patient who was complicatedwith diabetes, and patient with high score in ASA-PS classification were pointed as risky characteristics for SSI in this surgery. And as far as cases aged
more than 70 years old, patients who had smoking history or surgical history in the same vertebral body would be added to the above lists. However, all ofthese characteristics had been already reported as risk factors of SSI in any spine surgeries other than ME-PLIF [2]. Hence it was considered that noparticular risky characteristics confined to ME-PLIF would exist.
On the other hand, for the prospective factors to SSI on data in laboratory examinations, their changes at first visit after discharge were indicated tobe significant: i.e., increases of WBC and CRP, and decreases of %lymphocyte and serum albumin level. In the hospital which carried out this study, thetiming of first visit after discharge usually corresponded with day 28 after the surgery. In previous reports on open spine surgeries, positive findings inlaboratory examinations could appear by postoperative 4 days [3]. Thus, in ME-PLIF, timing of changes on laboratory data would be much delayed. Thismight be caused by peculiarity of this surgery. Namely, even if infection occurs, because of the minimal surgical wound of endoscope technique, theinfectious focus may be localized in deep tissues and can hardly expand.
Significance:
At ME-PLIF, points to be noted in the perioperative period were clearly recognized in this study. Especially, laboratory results must continue to bechecked, at least, until 1 month after the surgery, even if there are no positive findings just after surgery.
References:
1. Gerometta A,, et al.Int Orthopaedics,(36),457-464,2012.
2. Fang A, et al. Spine,(30),1460-1465,2015.
3. Takahashi J, et al. Spine,(26),1698-1704,2001

ORS 2017 Annual Meeting Poster No.1215