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.
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
