Introduction
A spondylitis developed after a surgery has been usually treated with drainage and curettage through anterior approach and autoiliac strut bone graft. However, anterior support with titanium cage combined with posterior pedicle screw fixation has been attempted. Implanting a foreign material is usually prohibited at an active pyogenic infection site. We tried to prove the usefulness of chip bone graft with metal cages in surgical treatment of spondylitis developed in posterior lumbar intebody fusion cases.
Materials and Methods
This is a retrospective study. The patients who received posterior lumbar interbody fusion (PLIF) between Jan. 2007 and Dec 2017 and had a spondylitis around the cage were reviewed. There were 1,831 PLIFs during the study period. There were 32 cases of surgical site infection and 20 of them were spondylitis around the cage. Ten out of the 20 cases had a revision surgery. All implants removal, drainage and curettage were done and interbody bone graft and pedicle screw re-fixation was done simultaneously. Five cases used autoiliac strut bone (Group I) and the other 5 cases used titanium cage and autoiliac chip bone (Group II) as interbody graft materials. The demographic, diagnostic and microbiological characteristics were investigated and the results of treatment were compared between the two groups.
Results
The diagnosis of infection was made at 282.0±106.1 (180~410) days in group I and 209±118.4 (75~335) days in group II after the PLIF. All cases had neither general fever nor local manifestations like heating and redness etc. All patients had back pain, however, only 2 cases of group II had neurological symptoms. C-reactive protein (CRP) level was elevated at 2 weeks from the PLIF in all cases (p<0.001). All cases had implant loosening at the time of their diagnosis. There was no failure of infection control. All cases showed normalization of CRP and radiological interbody fusion. The final Oswestry disability index (ODI) showed no difference between the two groups. ODI improved from 54.6±11.5 to 42.2±6.8 in group I (p=0.095) and from 63.6±6.9 to 44.8±11.7 in group II (p=0.025).
Conclusion
For the surgical treatment of spondylitis that were developed in PLIF, a comprehensive one stage operation that comprised all implants removal, drainage and curettage followed by simultaneous intebody bone graft with metal cages and pedicle screw re-fixation was useful to control the infection.

Purpose
To assess the volume of fusion mass after posterior lumbar interbody fusion (PLIF) using Hounsfield units methods.
Methods
The present study was within the frame work about a prospective observational cohort study to compare the surgical outcomes of a single-level PLIF for LSS between the local bone (LbG) and local bone plus hydroxyapatite groups (LbHa). The fusion material for each case was determined by the amount of available local bone. After the fusion material was chosen, patients were assigned to either the LbG group (n=20) or the LbHa group (n=20). The primary outcome was the assessment of fusion mass volume in each group.
Results
We used the new method using Hounsfield units for volumetric assessments of interbody fusion mass. There was no difference in fusion rates or volume of the fusion mass between the 2 groups.
Conclusions
Hounsfield unit method, that is the CT-based summation method using a cross-sectional slice, can be applied usefully to other areas of orthopaedics.

Objectives
The aim of this study was to monitor the quality control of pedicle screw fixation using a cumulative summation test (CUSUM). Overview of Literature: CUSUM test has already been used in several different surgical settings including the assessment of outcomes in transplant, laparoscopic, and total hip replacement surgeries. However, there has been no data regarding CUSUM analysis for spine surgery.
Methods
Patients with lumbar spinal stenosis who underwent lumbar fusion surgery were included in this study. The primary outcome was the CUSUM analysis for monitoring the quality control of the accuracy of pedicle screw insertion.
Results
Seven screws of the 100 pedicle screw insertions were considered to have failed in the lumbar fusion surgery, respectively. Throughout the monitoring period, there was no indication by the CUSUM test that the quality of performance of the pedicle screw fixation procedure was inadequate.
Conclusions
Thisstudy demonstrates the CUSUM test can be a useful tool for monitoring of the quality of procedures related with spine surgery.