The difference of surgical site infection according to the methods of lumbar fusion surgery.

J Spinal Disord Tech. 2012 Dec;25(8):E230-4.

Ahn DK, Park HS, Choi DJ, Kim TW, Chun TH, Yang JH, Kim DG.

Department of Orthopedic Surgery, Seoul Sacred Heart General Hospital, Seoul, Korea.

 

Abstract

STUDY DESIGN: Retrospective analysis.

OBJECTIVE: To compare the rates and types of a surgical site infection according to the surgical options in spine surgeries.

SUMMARY OF BACKGROUND DATA: Scant literatures exist on the difference of surgical site infection according to the surgical methods. We presumed that the incidence of infection after posterior lumbar interbody fusion (PLIF) was higher than posterior or posterolateral fusion (PF, PLF) due to several reasons.

METHODS: A retrospective analysis was made on the patients who received instrumented spinal fusion surgeries from 2000 to 2009. The differences of surgical site infection rates and characteristics were compared between the patients who received PF or PLF (group I) and PLIF (group II). In addition, the infection rate according to the graft options and number of cages was compared in group II.

RESULTS: A significant difference (P = 0.003) of infection rate between group I (0.3%, 3 cases out of 974) and group II (1.37%, 29 cases out of 2110) was observed. In group I, 67% of infections were wound infections and 33% were osteomyelitis. In group II, 23% were wound infections, 73% were osteomyelitis, and 4% were osteomyelitis combined with wound infection. Significant increase of infection rate was observed in the single cage group (P = 0.001) and mainly local bone grafted group (P = 0.030).

CONCLUSIONS: The infection rate of PLIF was higher than that of PF or PLF. Considering the increased infection rate in local bone grafted group and 52% of the infection cases after interbody fusion was osteomyelitis around interbody space, contaminated local bones and interbody space were suspected as major routes of contamination. The higher infection rate in single cage group than that of double cage group was attributed to vulnerability of remained avascular disk materials to infection.

PMID: 22576721

 

Supplements

The incisional surgical site infection of spinal fusion surgeries can be detected easily because definite symptoms and signs like pus drainage, heating and pain. But, organ/space surgical site infection rarely detected easily, thus results in the osteomyelitis. We recognized the fact that osteomyelitis without wound infection occurred more often in cases of PLIF than PF or PLF and most of them occurred around an interbody space. Most cases of PLIF used local bone as graft material, therefore has longer exposure time to room air than auto iliac bone that is grafted shortly after being harvested. And while removing soft tissues it can be easily contaminated by foreign bodies. Also it is presumed that the contaminated interbody space is not easily irrigated during surgery and avascular disc tissues are vulnerable to infection.

We did a retrospective analysis that the differences of surgical site infection rates and characteristics were compared between the patients who received PF or PLF (Group I) and PLIF (Group II). Additionally the infection rate according to the graft options and number of cages was compared in Group II. The characteristics of organ/space surgical site infections are devided into two catagories. One is osteomyelitis around pedicle screws (Figure 1). The other is osteomyelitis around interbody space (Figure 2).

Both the PLF group and PLIF group showed osteomyelitis around pedicle screws. It could be attributable to contamination of pedicle screws. PLIF group showed more osteomyelitis around interbody space. The authors presumed several factors that are as follows; addition of implants like metal cage, contaminated grafted chip bone, and vulnerability to bacterial proliferation and ineffective irrigation of avascular disc space.

Based on the above evidence and presumptions, a bundle of precautions were devised to prevent a surgical site infection. First, remove as much disc material as possible ensuring no  avascular tissue is left behind. Second, irrigate the interbody space with a nozzle which can be inserted into the space. Third, irrigate the local chip bones before being grafted to reduce the number of contaminated bacteria. Fourth, do not open the implants until just before instrumentation to avoid prolonged room air exposure.

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Figure 1. The lateral radiograph shows bone resorption and cut-out of pedicle screws(A). MRI T2-weighted image shows low intensity change in L4 body around pedicle screw(B).

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Figure. 2 The lateral radiograph shows bone resorption around interbody cage(A). Coronal reconstructed CT and axial CT image show both end plates destruction and resorption as typically swiss cheese like pattern(B),(C).

 

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