Background
Context: There are few reports of changes in global sagittal alignment and corresponding factors like hand grip strength (HGS) and muscle performance tests to detect changes in global sagittal alignment after surgery for lumbar spinal stenosis (LSS). Purpose: The purpose of the study was to determine whether HGS can be a useful predictive marker of global sagittal alignment changes after decompression with fusion surgery for LSS. Study Design: This is a retrospective observational study. Patient Sample: Patients who underwent spine surgery for LSS were included in the present study. Outcome Measures: Radiological spinopelvic parameters including sagittal vertical axis (SVA), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), global tilt (GT), and T1 pelvic angle (T1PA) were assessed. Clinical outcomes parameters like Oswestry Disability Index (ODI), Euro-QOL (EQ-5D), visual analog scale (VAS) scores for back or leg pain were assessed. To assess muscle performance, three functional mobility tests (6-meter walk test, timed up and go test, sit-to-stand test) and HGS were checked.
Materials and Methods
A total 91 consecutive patients who underwent spine fusion surgery for LSS were included. 1 year after posterior decompression and fusion surgery, the patients were further classified into four groups according to preoperative and postoperative SVA. We analyzed radiological parameters like SVA, LL, PT, PI, GT, and T1PA. The ODI, the EQ-5D and VAS scores for back or leg pain were recorded as clinical outcomes assessment. To assess muscle performance, SMT, TUGT, STS, and HGS were checked.
Results
HGS was significantly correlated with age, postoperative SVA, ODI, EQ-5D and muscle performance test. HGS was related with change of preoperative sagittal alignment 1yr after surgery. Using a receiver operating characteristic (ROC) curve to determine the cutoff values of HGS as predictors of postoperative balanced sagittal alignment according to SVA, cutoff value of HGS demonstrated 19.5 kg with a sensitivity of 82.1% and specificity of 66.7%.
Conclusion
Patients with non-balanced sagittal alignment in LSS demonstrated decreased muscle function and muscle strength. If the muscle strength was weak in the group in which the sagittal balance was maintained preoperatively, it could be converted to non-balanced sagittal alignment. Thus, preoperative HGS may be a good predictor of postoperative SVA change.

Purpose
Pull-out of pedicle screw in posterior pedicle fixation for thoracic and lumbar burst fractures causes delayed rehabilitation, persistant pain, and imblance of sagittal plane. In this study we try to analyse the factors that cause the pull-out of pedicle screw.
Materials and Methods
From March 01, 2006 to December 31, 2009, we assorted into two group; Group I for pullout pedicle, Group II for control. Plane lateral x-ray view film of thoracolumbar spine was taken on preoperation, postoperation, the first time when screw was pulled out and last follow up. we measure inserted angle for the upper endplate of screw, convergency angle and change of body height loss and kyphotic angle. We analysed corelation between these measuring values and pedicle screw pull-out by Mann-Whitney test and T-test.
Results
Pull-out of pedicle screw was found at mean 5weeks among nine cases. For inserted pedicle screws, which place in upper and lower vertebral body of fractured one, Value of inserted angle for upper end plate and convergency angle was found non-significant(p>0.05, Mann-Whitney test). Restoration of height loss and kyphotic angle of fractured vertebral body was statically significant(p<0.05, T-test).
Conclusion
In posterior pedicle fixation for thoracic and lumbar burst fractures, sufficient restoration of height loss and kyphotic angle is important factor for prevention of screw pull-out than inserted angle for upper end plate and convergency angle at a short period of time. Therefore we think that sufficient anterior fixation of vertebral body and restoration of kyphotic angle have a decisive effect on prognosis of patients.