Objective To investigate the transiliac-transsacral screw insertion pathway (TSIP) so as to provide an anatomical basis for clinical surgical practice.Methods CT scanning data of normal pelvis in 90 Chinese adults were selected by random number table.There were 45 males and 45 females,aged from 21 to 82 years (mean,53.88 years).After computed tomography scan,pelvic data of the 90 subjects were entered into Mimics software 16.0 for three-dimensional reconstruction.The outer frames of sacrum and ilium at sagittal plane were depicted.Maximum inscribed circle method was applied to determine the screw insertion pathways which traversed 1st (S1) and 2nd (S2) sacral segments,respectively.The diameters and lengths of screw pathways,the distances from screw insertion points to both anterior superior iliac spine and posterior superior iliac spine,as well as the angles between pathways and anatomic surface were measured.Results Most subjects had the condition of a trans-S1 TSIP (male 78％,female 76％),and all the tested pelvis had the condition of trans-S2 TSIP.There was no statistically significant difference between the left and right side parameters in male group,and so was in female group (P ＞0.05).TSIP radius:there was no statistically significant difference among male S1 [(5.52 ± 1.91)mm],male S2 [(5.35 ± 1.05)mm],and female S1 [(5.49± 1.34)mm] (P＞0.05),but each of them was greater than female S2 [(4.79 ± 1.40) mm] (P ＜ 0.05).TSIP length:male S1 [(158.25 ±9.84) mm] was larger than male S2 [(138.94 ± 9.75) mm],and female S1 [(154.91 ± 9.40) mm] was larger than female S2 [(141.01 ±8.60)mm].The screw insertion point was located at the outer ilium side.The distances from S1 to anterior superior iliac spine and to posterior superior iliac spine were (96.49 ±6.91)mm and (68.22 ±6.35)mm in males but (100.48 ±8.15)mm and (61.57 ±6.84) mm in females.The distances from S2 to anterior superior iliac spine and to posterior superior iliac spine were (114.43 ±8.77)mm and (49.62 ±8.54)mm in males but (114.75 ± 10.19)mm and (44.52 ±8.36)mm in females.Compared with those with a condition of TSIP in S1,a pelvis without a condition of an S1 TSIP had larger S2 TSIP radius.The S2 TSIP radius in one with such condition in male was (5.10 ±0.84)mm and that in one without such condition in male was (6.22 ± 1.27) mm.The corresponding female data was (4.37 ± 0.92)mm and (6.11 ± 1.84)mm (P ＜ 0.05).Both S1 and S2 TSIP were almost vertical to sagittal plane and parallel to coronal plane.Conclusions Anatomically,a S1 or S2 transiliactranssacral screw is available in most Chinese adults for sacroiliac joint fixation on both sides.Mimics software can be helpful to ensure the pathway of screw fixation,which provides reference for transiliactranssacral screw fixation technique.

Objective: To explore the association among clinical features, electromyography (EMG) and magnetic resonance neurography (MRN) in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Methods: A cross-sectional survey was conducted to enroll consecutively typical CIDP patients in Renmin Hospital of Wuhan University from May 2017 to May 2019. The Hughes Disability Scale (HDS) was used to evaluate the illness severity of the patients. The electrodiagnostic parameters including motor conduction velocity (MCV), compound muscle action potential (CMAP), F-wave latency, sensory nerve conduction velocity (SCV) and sensory nerve action potential (SNAP) of upper and lower limbs were analyzed. The patients whose response waveform can be elicited in all nerves were defined as group A, and those without response in one or more nerves as group B. MRN quantitative technique was used to calculate the cross-sectional area of nerves roots (nr-CSA) of brachial plexus and lumbosacral plexus. The linear regression method was used to analyze the correlation among clinical features, EMG and nr-CSA. Results: A total of 32 patients with typical CIDP met the criteria, 75% (24/32) of whom were males. There were 16 patients in the mild group (group A) and 16 in the severe one (group B). The abnormal rate of F-wave latency was the highest. Cerebrospinal fluid (CSF) protein, HDS score were correlated significantly with the nr-CSA of brachial plexus and lumbosacral plexus in the two groups (group A: CSF protein and brachial plexus nr-CSA: r=0.498, P=0.004; CSF protein and lumbosacral plexus nr-CSA: r=0.479, P=0.007; HDS score and brachial plexus nr-CSA: r=0.650, P=0.000; HDS score and lumbosacral plexus nr-CSA: r=0.625, P=0.000. group B: CSF protein and brachial plexus nr-CSA: r=0.497, P=0.049; CSF protein and lumbosacral plexus nr-CSA: r=0.503, P=0.047; HDS score and brachial plexus nr-CSA: r=0.605, P=0.001; HDS score and lumbosacral plexus nr-CSA: r=0.648, P=0.000). MCV of median nerve and ulnar nerve was negatively correlated with nr-CSA of brachial plexus in the two groups (group A: MCV of median nerve and nr-CSA of brachial plexus: r=-0.309, P=0.019; MCV of ulnar nerve and nr-CSA of brachial plexus: r=-0.286, P=0.027. group B: MCV of median nerve and nr-CSA of brachial plexus: r=-0.660, P=0.000; MCV of ulnar nerve and nr-CSA of brachial plexus: r=-0.581, P=0.001). The F-wave latencies of median and ulnar nerves were positively correlated with nr-CSA of brachial plexus, and the CMAP amplitude of tibial nerve and SNAP amplitude of sural nerve were positively correlated with nr-CSA of lumbosacral plexus in group B. Conclusions Male patients with CIDP are predominant. The higher the nr-CSA in brachial plexus and lumbosacral plexus, the higher the CSF protein and disability score, and the larger the nr-CSA in brachial plexus, the slower the MCV in the median and ulnar nerve. For group B patients with more severe nerve injury, the larger nr-CSA of brachial plexus was, the longer F-wave latency of median and ulnar nerve was, and the larger nr-CSA of lumbosacral plexus was, the lower CMAP amplitude of tibial nerve and SNAP amplitude of sural nerve were. As a non-invasive test, MRN can be used to assist in the diagnosis of CIDP and to assess the severity of the disease.