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.