Patient selection. Patients included in the study were selected from among patients with PD who visited the outpatient rehabilitation department of Noborito Neurology Clinic regularly for at least 1 year, starting sometime between March 2018 and March 2019. The LTF angle had been measured on initial examination and at 1 year following the initial examination in all patients included in the study. Patients chosen for inclusion also met the following criteria: a definitive diagnosis of PD, based on the Movement Disorder Society Clinical Diagnostic Criteria for Parkinson’s disease (21); judgment that the patient will be able to complete a 1-year evaluation; age ≥ 20 years; no change in oral medications within 1 week of the initial or 1-year evaluation; “on” status at the time of initial or 1-year evaluation if the patient was suffering from the “wearing-off” phenomenon; ability to understanding instructions; and ability to stand upright. Exclusion criteria were as follows: diagnosis of a PD-related disorder other than PD itself; presences of any psychiatric symptoms, such as visual or other hallucinations at the time of initial or 1-year evaluation; signs of the wearing-off phenomenon during the drug administration period; restricted range of motion that rendered passive guidance of the patient into a vertical position impossible; dramatic worsening of the PD symptoms within 1 week prior to evaluation; and rapid onset of postural abnormalities, i.e., onset within 1 month prior to evaluation.
Informed consent
was obtained from all patients and/or their family. Patients had been informed that they could decide not to approve use of their clinical data for study purposes and were given directions on how to “opt out” of the study. They were told that they would incur no disadvantages if they did not consent to the use of their data. Furthermore, patient data were anonymized to ensure that no personal identifying information was disclosed. The study was conducted with our university’s study guidelines and regulations with the approval of the St. Marianna University School of Medicine ethics committee (approval number: 5004).
Clinical evaluation and data collection. Clinical evaluations included standing posture at rest and determination of the SPV angle. Patients’ medical records were accessed for collection of the following information: age, sex, disease duration, PD severity and outcomes of neuropsychological examinations. PD severity had been evaluated on the basis of mH&Y stages (22) and UPDRS (23) scores. The Mini-Mental State Examination (MMSE) (24) and Japanese version of the Montreal Cognitive Assessment (MoCA-J) (25), as well as the Frontal Assessment Battery (FAB) (26), were used for neuropsychological testing. Patients’ LEDD and LEDDDA were also obtained (27).
Rehabilitation program. The study patients had undergone 60 min of rehabilitation therapy once a week or more. The rehabilitation program was designed with three objectives in mind (15, 28). The first was to appropriately correct the patient’s posture, the second was to enable the patient to perform? various physical exercises, including maintaining control of the corrected trunk, and the third was to increase the patient’s endurance. Each session was of three separate components: a 20-min period that entailed the patient focusing on somatic sensations while the physical therapist made adjustments to correct for the difference between the patient’s actual posture and the vertical axis, a 20-min period designed to help the patient maintain control of the trunk while adopting various positions and performing various exercises, and a 10-min period of aerobic exercise performed on an ergometer or treadmill.
Postural evaluation. As noted above, patients’ LTF had been evaluated at the initial examination and then at 1 year. Patients’ SPV had been evaluated at the initial examination. Standing posture at rest and the SPV were taken as the postural endpoints. In accordance with preceding studies (11), the landmark points for postural evaluation were the spinous processes of the seventh cervical (C7) and fifth lumbar (L5) vertebrae, and reflective markers for three-dimensional (3D) motion analysis (Nobbyteck VNS-BL-MC-190) were attached to these sites. Image analysis software Image J (https://imagej.nih.gov/ij/index.html) was used to measure the relevant angles. Images were captured at rest using a digital camera (Panasonic DMC-LZ10), after which it was possible to use the software to calculate the angle between the vertical axis and an arbitrary second axis.
Standing evaluation at rest. Patients’ LTF and FTF angles had been measured at the time of initial evaluation and at 1 year. The patient’s position on opening his/her eyes immediately after standing up was evaluated three times, and the mean value was taken as the patient’s standing position. A digital camera was aimed at the center point of Jacoby’s line and at the high point of each iliac crest for measurement of the LTF angle and at a point in the sagittal plane for measurement of the FTF angle. Photographs were taken at rest and included both C7 and L5. The standard axis was a vertical line crossing L5 and descending to the floor. The axis of forward flexion was defined as the line connecting C7 and L5 observed along the sagittal plane, while the axis of lateral flexion was defined as a line connecting C7 and L5 observed along the coronal plane (11, 12).
SPV evaluation. SPV was evaluated in the coronal plane, and the SPV angle and SPV ratio were recorded. The SPV angle was defined as the angle between the vertical axis and the axis of lateral flexion. As described previously, the vertical axis was defined as the vertical line passing through L5 and descending to the floor, and was used as the reference, while the axis of lateral flexion was defined as the line connecting C7 and L5 at the point in time when the patient perceived himself/herself to be in a vertical position (Fig. 4) (10). The SPV angle was measured by first establishing the starting position, which entailed the patient closing their eyes in a standing position, and being passively guided into maximum lateral trunk flexion. The investigator then guided the patient towards the vertical axis. The patient then notified the investigator when they perceived their trunk to be a vertical position, and the images at rest were taken in this position at the height of the Jacoby’s line and along the posterior midline. This sequence was performed three times each on the left and right, giving a total of six measurements. The mean value of these measurements was used as the SPV angle. The SPV ratio was the SPV measured with reference to the axis of lateral flexion, and in accordance with preceding studies, was calculated by dividing the SPV angle by the LTF angle (SPV ratio = SPV angle/LTF angle) (11).
Statistical analysis. Relations between the baseline LTF angle, change in the LTF angle at 1 year and each of the postural evaluation endpoints were analyzed by means of Spearman's rank correlation coefficient. Change in LTF angle was used to divide the patients into two groups: those for whom LTF improved (LTF improved group) and those for whom LTF did not improve (LTF non-improved group), based on whether or not improvement was observed once or more from the time of initial evaluation to 1 year. The improvement in the LTF angle and items observed to have significant correlation were defined as independent variables and used to create receiver operating characteristic (ROC) curves for performance of significant variables as predictors of improvement, and the areas under the ROC curves (AUCs) were calculated to measure the ability of the variables to predict improvement. Cut off values were derived on the basis of Youden’s Index (Youden's J statistic) (29). All statistical analyses were performed with SPSS version 27 (IBM SPSS Statistics for Windows; IBM Corp, Armonk, NY), and p < 0.05 was considered significant.