K-Line Tilt is a Predictor of Postoperative Kyphotic Deformity After Laminoplasty for Cervical Myelopathy Caused by Ossification of the Posterior Longitudinal Ligament

Study Design: Retrospective single-center study. Objectives: K-line is a decision-making tool to determine the appropriate surgical procedures for patients with cervical ossification of the posterior longitudinal ligament (C-OPLL). Laminoplasty (LAMP) is one of the standard surgical procedures indicated on the basis of K-line measurements (+: OPLL does not cross the K-line). We investigated the impact of K-line tilt, a radiographic parameter of cervical sagittal balance measured using the K-line, on surgical outcomes after LAMP. Methods: The study included 62 consecutive patients with K-line (+) C-OPLL who underwent LAMP. The following preoperative and postoperative radiographic measurements were evaluated: (1) the K-line, (2) K-line tilt (an angle between the K-line and vertical line), (3) center of gravity of the head –C7 sagittal vertical axis, (4) C2–C7 lordotic angle, (5) C7 slope, and (6) C2–C7 range of motion. Clinical results were evaluated using the Japanese Orthopedic Association scoring system for cervical myelopathy (C-JOA score). Results: All the patients had non-kyphotic cervical alignment (CL ≥ 0°) preoperatively; however, kyphotic deformity (CL < 0°) was observed in 6 patients (9.7%) postoperatively. The recovery rate of the C-JOA scores was poor in the kyphotic deformity (+) group (7.8%) than in the kyphotic deformity (−) group (47.5%). The K-line tilt was identified to be a preoperative risk factor in the multivariate analysis, and the cutoff K-line tilt for predicting the postoperative kyphotic deformity was 20°. Conclusions: LAMP is not suitable for K-line (+) C-OPLL patients with K-line tilts >20°.

Upper instrumented vertebra to the right of the lowest instrumented vertebra as a predictor of an increase in the main thoracic curve after selective posterior fusion for the thoracolumbar/lumbar curve in Lenke type 5C adolescent idiopathic scoliosis: multicenter study on the relationship between fusion area and surgical outcome

OBJECTIVEUnfused main thoracic (MT) curvatures occasionally increase after selective thoracolumbar/lumbar (TL/L) fusion. This study sought to identify the predictors of an unacceptable increase in MT curve (UIMT) after selective posterior fusion (SPF) of the TL/L curve in patients with Lenke type 5C adolescent idiopathic scoliosis (AIS).METHODSForty-eight consecutive patients (44 females and 4 males, mean age 15.7 ± 2.5 years, range 13–24 years) with Lenke type 5C AIS who underwent SPF of the TL/L curve were analyzed. The novel “Shinshu line” (S-line) was defined as a line connecting the centers of the concave-side pedicles of the upper instrumented vertebra (UIV) and lowest instrumented vertebra (LIV) on preoperative radiographs. The authors established an S-line tilt to the right as S-line positive (S-line+, i.e., the UIV being to the right of the LIV) and compared S-line+ and S-line− groups for thoracic apical vertebral translation (T-AVT) and MT Cobb angle preoperatively, early postoperatively, and at final follow-up. The predictors for T-AVT > 20 mm at final follow-up were evaluated as well. T-AVT > 20 mm was defined as a UIMT.RESULTSAmong the 48 consecutively treated patients, 26 were S-line+ and 22 were S-line−. At preoperative, early postoperative, and final follow-up a minimum of 2 years later, the mean T-AVT was 12.8 mm (range −9.3 to 32.8 mm), 19.6 mm (range −13.0 to 41.0 mm), and 22.8 mm (range −1.9 to 68.7 mm) in the S-line+ group, and 10.8 mm (range −5.1 to 27.3 mm), 16.2 mm (range −11.7 to 42.1 mm), and 11.0 mm (range −6.3 to 26.9 mm) in the S-line− group, respectively. T-AVT in S-line+ patients was significantly larger than that in S-line− patients at the final follow-up. Multivariate analysis revealed S-line+ (odds ratio [OR] 23.8, p = 0.003) and preoperative MT Cobb angle (OR 7.9, p = 0.001) to be predictors of a UIMT.CONCLUSIONSS-line+ was defined as the UIV being to the right of the LIV. T-AVT in the S-line+ group was significantly larger than in the S-line− group at the final follow-up. S-line+ status and larger preoperative MT Cobb angle were independent predictors of a UIMT after SPF for the TL/L curve in patients with Lenke type 5C AIS. Surgeons should consider changing the UIV and/or LIV in patients exhibiting S-line+ during preoperative planning to avoid a possible increase in MT curve and revision surgery.

Study on Tilt Model and Finite-Element Simulations on Roller Leveler

According to the adjustment process of wide plate roller leveler of the cross cut shearing line, tilt model during leveling was established with ANSYS/LS_DYNA, which is one of the dynamic FE analysis software. The leveling effect on plate shape quality with or no with tilt model was analyzed respectively. The simulation results indicated the tilt model can get the more equivalent stress distribution and reduce the residual stress, which improve the straightness quality of the plate. In addition, the leveling force of each work roll can be decreased with tilt model. This is very beneficial to increase the production output of the leveler.

Spatiotemporal Dynamics of Attention-Induced Distortions and Illusions

Selective attention induces perceptual distortions, ranging from repulsion of objects located near the attended area (Suzuki and Cavanagh, 1994 Investigative Ophthalmology and Visual Science35 2081) to magnification of inattended objects (Tsal and Shalev, 1996 Journal of Experimental Psychology: Human Perception and Performance22 233 – 243). Two hypothetical mechanisms have been postulated: a shift of receptive field positions away from the locus of attention (receptive-field shift hypothesis) or the enlargement of perceived space around the attended location (spatial-enlargement hypothesis). The aim of the present study was to distinguish between these two hypotheses, by investigating the spatial and temporal properties of attention-induced distortions. Perceptual judgments on Vernier alignment, line tilt, line length, and size of outlined figures were used to measure attention-induced changes in perception. Attention was induced exogenously (by blinking a specific set of dots around the test stimuli) or endogenously (by instructing the subject to selectively attend the dots). After inducing attention, the test stimuli were briefly flashed. A staircase method was used to measure the attentional effect. The experiment was performed with 3 Korean and 3 German subjects. A vertical line was perceived as repelled from the locus of attention, and a line segment appeared longer when attention was given to its vicinity. In addition, several well-known illusions (eg the Ponzo and the Gibson illusions) were produced by having the subjects merely attend a set of inducing dots. The effects decreased as the distance between the locus of attention or the time between the onset of attention and the stimulus presentation increased. The results imply that the space-enlargement hypothesis provides a better explanation for the attention-induced changes in perception than the receptive-field-shift hypothesis.