The study was evaluated and approved by the ethics committee of Tehran University of Medical Sciences (IRB approval no., IR. TUMS. MEDICINE. REC. 1396.3080). A total of 110 patients with scoliosis were enrolled in this analytical cross-sectional study. Patients (n=2) with complex rotary component were excluded. The STROBE statement checklist was followed meticulously (appendage). All patients were referred to our institution’s neurosurgery clinic, which is a referral center for spinal deformities, between 2009 and 2017. A set of digital radiography and whole neuro-axis magnetic resonance imaging (MRI) was performed on all patients. In total, 76 patients were diagnosed with ISC and 34 with CSC. All scoliotic patients with a Cobb angle of 10° or more were included. The exclusion criteria for this study were as follows: patients aged less than 5 years; those with myelomeningocele or meningocele, prior history of spine surgery, any contraindication to MRI, neuromuscular or other degenerative diseases, psychologic illnesses that affect history taking and examination reliability, paralysis, and degenerative and reactive scoliosis; and those who are unable to perform UDS due to any reasonable cause.

All participants were informed about the different steps of the study and the advantages and disadvantages of the specific evaluations, and written informed consents were obtained from the patients or their parents. Demographic data were obtained using designed datasheets, and patients were assured about data confidentiality. Any signs or symptoms of urinary malfunctions during physical examination and in the process of obtaining a patient’s history were recorded.

Standard UDS was performed on each patient. Abnormal UDS finding was defined as the presence of impaired capacity/compliance (mild impairment) and overactivity of the bladder or dyssynergia (significant disorders).

Whole neuro-axis MRI with and without contrast enhancement was performed on all participants to assess the type of scoliosis, intracanal and cord anomalies, and position of the tip of the conus medullaris. The MRI images were obtained with the 1.5 Tesla Siemens MRI equipment. Furthermore, the presence of anomalies, such as syrinx, intradural lipoma, different types of split cord malformations (SCMs), and thick filum terminale, was cautiously evaluated and recorded. We also identified patients with cord tethering abnormality, which was defined as the presence of at least one of the following: a low-lying filum terminale at any place below the L2/L3 disk space, neurologic manifestations of cord tethering and placement of the tip of the filum at any level below L1/L2, SCM I, or any other tethering pathologies of the spine, including the dermal sinus tract or tumors, or a tight filum terminale on MRI. The presence of a tight filum terminale was further evaluated by performing MRI on all patients while in prone position. A forward movement of the canal width by at least 10% was considered normal, thereby ruling out the tightness of the filum terminale [13]. The presence of cord tethering or tightness of the filum terminale was further confirmed during surgery by two skilled neurosurgeon observers for each case. Examination of the tightness of the filum and stretch test were routinely performed during surgery; after a consensus was achieved between the observers, these patients were considered to have tethered cords. Furthermore, AP and lateral standing whole-spine radiography and bending X-ray images were obtained to evaluate for Cobb angle. Two neurosurgeons performed all physical examinations, and the imaging data were analyzed by two radiologists who are experienced in evaluating MRI and spine radiography findings. The UDS findings were reviewed by an expert urologist. All examiners were blinded to the other data of the cases during observation.

All statistical analyses were performed using the IBM SPSS software ver. 22.0 (IBM Corp., Armonk, NY, USA). Categorical variables were presented as absolute (numbers) and relative (percent) values and continuous variables as mean and standard deviation. The UDS results, known as a categorical variable, were tested for an association with demographic characteristics, type of scoliosis, sphincter problems, spine MRI anomalies, and other variables using chi-square analysis for categorical variables. Independent sample t-test was used for comparing continuous variables. A p-value <0.05 was considered statistically significant.

A total of 110 patients with scoliosis who met our criteria were assessed. Among the participants, 72 (65.5%) were women and 38 (34.5%) men with a ratio of 1.8:1 (p=0.053) (Table 1). Moreover, 34 patients (30.9%) presented with CSC and 76 (69.1%) with ISC. The mean ages were 11.55±5.7 years (range, 3–28 years) in the congenital group and 17.94±7.04 years (range, 8–40 years) in the idiopathic group (p<0.001).

UDS was performed on all participants. A total of 68 patients (61.8%) had normal UDS findings. Significant problems, such as dyssynergia and overactive bladder, were noted in 32 patients (29.1%), and milder problems, including low bladder capacity and compliance, were observed in 10 patients (9.1%) (Table 2). Moreover, 11 (10%) of 110 patients had subjective urinary sphincter problems. The presence of such symptoms was more common in patients with CSC than in those with ISC. However, the result was not significantly different (p=0.31) (Table 1). Among 99 patients (90%) without sphincteric symptoms, 64 (64.6%) had normal UDS finding; 8 (8.1%), mild problems (only changes in capacity/compliance); and 27 (27.3%), significant UDS disorders. Among the 27 patients with significant UDS abnormalities, 12 presented with CSC and 15 with ISC. No significant correlation was observed between the type of scoliosis and changes in UDS findings (p=0.098) (Table 3).

Standard AP digital radiograph images of the whole spine were used to determine the Cobb angle. The mean angle in the entire sample was 64.4°±27.3°, with 10° being the lowest and 160° the highest. The mean values for the Cobb angles were 55.3°±22.8° in the congenital group and 68.4°±28.3° in the idiopathic group (p=0.022) (Table 1). TCS or anomalies that could cause cord tethering were found on the MRI images of 26.3% and 38.2% of patients with ISC and CSC, respectively. Although TCS was more commonly found in the congenital group than in the idiopathic group, the result was not significantly different (p=0.571). This finding is important in this research (Table 4).

In the ISC group, a significantly abnormal UDS finding indicated that the risk of TCS increased from 26.3% to 50% (odds ratio [OR], 4.2). Meanwhile, in the congenital group, the risk was similar: 35.7% in patients with a significantly abnormal UDS finding and 38.2% in patients with CSC (OR, 0.8) (Table 5). The predictive power of a significantly abnormal UDS finding for the presence of TCS was statistically significant (p=0.009) in the idiopathic group. This value was high enough to be considered significant in all patients with scoliosis (p=0.04), although it was completely irrelevant in predicting TCS in the congenital group (p=0.8).

During follow-ups, the patients were re-evaluated by a multidisciplinary panel, which included neurosurgeons, ortho-spine surgeons, neuroradiologists, and urologists, to plan for further corrective spine surgery.