Abstract

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.

• Keywords: Hand grip strength, Spinopelvic alignment, Lumbar spinal stenosis, Surgery