Purpose
The biplanar whole body imaging system (EOS) is a new tool for measuring whole body sagittal alignment in a limited space. This tool may affect the sagittal balance of patients compared to conventional whole spine radiography (WSX). This study is to investigate the difference in sagittal alignment between WSX and EOS.
Materials and Methods
We compared spinal and pelvic sagittal parameters in 80 patients who underwent EOS and WSX within one month between July 2018 and September 2019.The patients were divided based on sagittally balanced and imbalanced groups according to pelvic tilt (PT) >20˚, pelvic incidence-lumbar lordosis >10°, C7-sagittal vertical axis (SVA) > 50 mm in WSX.
Results
In sagitally imbalanced group, for WSX versus EOS, the pelvic parameters demonstrated compensation in EOS with smaller PT (27.4±11.6° vs. 24.9±10.9°, p=0.003), greater sacral slope (SS), and patients tended to stand more upright with smaller C7-SVA (58.4±17 mm vs. 48.9±57.3 mm, p=0.003), T1-pelvic angle (TPA), T5-T12, and T2-T12. However, in sagitally balanced group, these differences were less pronounced only with smaller PT (10.8±6.9° vs. 9.4±4.7°, p=0.04), TPA and T2-T12 angle, but SS and C7-SVA were similar (p>0.05).
Conclusions
EOS shows a negative SVA shift and lesser pelvic tilt than WSX especially in patients with sagittal imbalance. When making a surgical plan, surgeon should consider these differences between EOS and WSX.

Objective
To evaluate the efficacy and safety of anorganic bone matrix (ABM)/P-15 compared with local autograft bone in posterior lumbar interbody fusion (PLIF) with pedicle screws for degenerative lumbar diseases.
Methods
This is a retrospective analysis of consecutive series of 138 patients undergoing 1 or 2 levels PLIF from 2015 to 2020 in our single institute. Local autograft bone or ABM/P-15 (i-factor, Cerapedics Inc., Westminster, Colorado USA) were used for interbody fusion. The successful fusion was defined as the segmental cobb angle of less than 5 degrees of in flexion/extension X-rays and continuity of the trabecular bony bridging in computed tomography (CT) images.
Results
Among a total of 138 patients, total levels of fusion were 202, of which 74 were in 1 level fusion and 128 were in 2 level fusion. And 93 used ABM/P-15 and 109 used local autograft bone. The evaluation time of fusion status was 1 year after surgery. Successful fusion based on X-ray images was achieved 84.1% (90/107) for local autograft bone and 91.3% (84/92) for ABM/P-15 (p=0.127). Based on CT images, 86.9% (93/107) of autograft group and 95.6%(87/91) of AMP/P-15 group showed successful fusion respectively (p=0.034). Occurrence rate of autolysis was 14% (15/107) for local autograft bone and 17.6% (16/91) for ABM/P-15. Subsidence rates were 11.2% (12/107) for local autograft bone and 9.99% (9/91) for ABM/P-15. Hollow formation around pedicle screw was noted in 9.3% (10/107) for local autograft bone and 2.2% (2/91) for ABM/P-15.
Conclusions
The use of AMP/P-15 for lumbar interbody fusion surgery can be a good substitute for local autograft bone in terms of better fusion rate and similar complication rate on radiologically.