Aims. The aim of this study was to compare the peak pull-out force
(PPF) of pedicle-lengthening screws (PLS) and traditional pedicle
screws (TPS) using instant and cyclic fatigue testing. Materials and Methods. A total of 60 lumbar vertebrae were divided into six groups:
PLS submitted to instant pull-out and fatigue-resistance testing
(groups A1 and A2, respectively), TPS submitted to instant pull-out
and fatigue-resistance testing (groups B1 and B2, respectively)
and PLS augmented with 2 ml polymethylmethacrylate, submitted to
instant pull-out and fatigue-resistance testing (groups C1 and C2,
respectively). The PPF and normalized PPF (PPFn) for bone mineral density
(BMD) were compared within and between all groups. Results. In all groups, BMD was significantly correlated with PPF (r =
0.83, p < 0.001). The PPFn in A1 was significantly less than
in B1 (p = 0.006) and C1 (p = 0.002). The PPFn of A2 was significantly
less than in B2 (p < 0.001) and C2 (p < 0.001). The PPFn in
A1, B1, and C1 was significantly greater than in A2 (p = 0.002),
B2 (p = 0.027), and C2 (p = 0.003). There were no significant differences
in PPFn between B1 and C1, or between B2 and C2. Conclusion.
Objectives. Pedicle-lengthening osteotomy is a novel surgery for lumbar spinal stenosis (LSS), which achieves substantial enlargement of the spinal canal by expansion of the bilateral pedicle osteotomy sites. Few studies have evaluated the impact of this new surgery on spinal canal volume (SCV) and neural foramen dimension (NFD) in three different types of LSS patients. Methods. CT scans were performed on 36 LSS patients (12 central canal stenosis (CCS), 12 lateral recess stenosis (LRS), and 12 foraminal stenosis (FS)) at L4-L5, and on 12 normal (control) subjects. Mimics 14.01 workstation was used to reconstruct 3D models of the L4-L5 vertebrae and discs. SCV and NFD were measured after 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm pedicle-lengthening osteotomies at L4 and/or L5. One-way analysis of variance was used to examine between-group differences. Results. In the intact state, SVC and NFD were significantly larger in the control group compared with the LSS groups (P<0.05). After lengthening at L4, the percentage increase in SCV (per millimetre) was LRS>CCS>FS>Control. After lengthening at L5 and L4-L5, the percentage increase in SCV (per millimetre) was LRS>FS>CCS>Control. After lengthening at L4 and L4-L5, the percentage increase in NFD (per millimetre) was FS>CCS>LRS>Control. After lengthening at L5, the percentage increase in NFD (per millimetre) was CCS>LRS>control>FS. Conclusions. LRS patients are the most suitable candidates for treatment with pedicle-lengthening osteotomy. Lengthening L4 pedicles produced larger percentage increases in NFD than
Aims. This study aimed to determine the relationship between pedicle-lengthening
distance and bulge-canal volume ratio in cases of lumbar spinal
stenosis, to provide a theoretical basis for the extent of lengthening
in pedicle-lengthening osteotomies. . Methods. Three-dimensional reconstructions of CT images were performed
for 69 patients (33 men and 36 women) (mean age 49.96 years; 24
to 81). Simulated pedicle-lengthening osteotomies and disc bulge
and spinal canal volume calculations were performed using Mimics
software. . Results. The mean spinal canal volume of the two groups, L4 and L5, were
14 646.81 mm. 3. (5918.60 to 22 717.77) and 16 408.47 mm. 3. (8678.21
to 31 204.79), respectively. The mean lengthening distance was 2.17
mm (0.5 to 4.8) and the mean bulge-canal volume ratio was 0.23 (0.05
to 0.48). The pedicle-lengthening distance of the two groups were very
strongly correlated with disc bulge volume and bulge-canal volume
ratio (p <
0.001); the predictive equation was established as
L = 0.06 + 9.06R (where L equals the pedicle-lengthening distance
and R represents the bulge-canal volume ratio). . Discussion. Our findings indicated that lumbar pedicle-lengthening distance
strongly correlates with bulge-canal volume ratio, which can be
estimated before surgery from CT images. Take home message: The predictive equation could help surgeons
to decide the
