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BACKGROUND: In acetabular fracture surgery, an infra-acetabular screw (IAS) is inserted from the anterior to the posterior column through the infra-acetabular corridor to stabilize both columns. Although the IAS is useful for increasing fixation strength, proper placement requires proficiency and often results in extraosseous screw penetration. The complex anatomy of the infra-acetabular corridor and difficult intraoperative detection of the ideal insertion point and angle make proper placement of the IAS challenging. This study aimed to detect the ideal insertion point and angle of the IAS based on anatomical landmarks that can be directly identified intraoperatively. METHODS: We retrospectively reviewed the pelvic CT of 50 adults who underwent serial slice CT imaging. The pelvic inlet plane (PIP), which contains the anterior border of both the sacroiliac joint and posterior superior edge of the pubic symphysis, was used as the reference plane for the pelvic coordinate system to simulate the ideal insertion of IAS. The distance from the posterior superior edge of the pubic symphysis to the ideal insertion point of the IAS (IAS distance) and the angle and length of the IAS that could be inserted from the ideal insertion point were measured. RESULTS: The mean IAS distance was 61.0 ± 5.7 mm (57.6 ± 4.3 mm in men and 64.4 ± 4.9 mm in women). The mean angle between ideal IAS and yz-plane on the outlet view (α-angle) was 8.4 ± 6.6 ° (6.4 ± 5.6° in men and 10.5 ± 7.0° in women). The mean angle between ideal IAS and y-axis on the yz-plane (ß-angle) was 86.5 ± 10.6 ° (86.0 ± 10.3° in men and 87.0 ± 10.9° in women). The length of IAS was 97.1 ± 4.7 mm in men and 89.2 ± 3.6 mm in women. CONCLUSION: The IAS ideal insertion point detected as a distance from the pubic symphysis may aid in the proper insertion of the IAS during surgery. The insertion angle was parallel or tilted 10 ° laterally to the longitudinal axis in the pelvic outlet plane and almost perpendicular to the PIP in the sagittal plane when inserted from the ideal insertion point.

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BACKGROUND: Counter-nutation movement is deemed crucial during the management of the birth process. It is a combination of lateral ilia expansion and backward displacement of the promontory resulting from the external rotations of the femurs producing an enlargement of the pelvic inlet. However, since its description by Farabeuf, this mechanism has never been challenged and analyzed in a dynamic finite element study. METHODS: Based on a female pelvic mesh and sacroiliac ligaments, we simulated external rotations of both femurs with imposed rotation of the two acetabulum centers. We hypothesize that lateral ilia expansion generates a sacrum movement resulting in a backward displacement of the promontory and a pelvic inlet enlargement. RESULTS: Finite element simulation confirms our hypothesis and reveals that ilio-sacro-transverse and axile ligaments play an essential role in this mechanism. Indeed, the increase in stiffness (ranging from 500 MPa to 750 MPa) of these ligaments accentuates the counter-nutation movement and the opening of the inlet. Instead of the anatomic congruence between the ilium and the sacrum, the sacroiliac ligaments may explain the counter-nutation. After a 6° of femur rotation, the inlet area increases to 11 cm2 (141 cm2 vs. 130 cm2). This enlargement could be noteworthy in case of obstructed labor or shoulder dystocia. Moreover, the association between external rotation and flexion of the femurs could be more efficient for opening the pelvic inlet. CONCLUSIONS: Our result did not support the original assumption of Farabeuf. By revealing how postural adjustment increases the bony birth canal, this study provides essential information for the clinical management of the delivery.

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BACKGROUND: Intersphincteric resection (ISR) has been increasingly used as the ultimate sphincter-preserving procedure in extremely low rectal cancer. The most critical complication of this technique is anastomotic leakage. The incidence rate of anastomotic leakage after ISR has been reported to range from 5.1% to 20%. AIM: To investigate risk factors for anastomotic leakage after ISR based on clinicopathological variables and pelvimetry. METHODS: This study was conducted at Department of Colorectal Surgery, Japanese Red Cross Medical Center, Tokyo, Japan, with a total of 117 patients. We enrolled 117 patients with extremely low rectal cancer who underwent laparotomic and laparoscopic ISRs at our hospital. We conducted retrospective univariate and multivariate regression analyses on 33 items to elucidate the risk factors for anastomotic leakage after ISR. Pelvic dimensions were measured using three-dimensional reconstruction of computed tomography images. The optimal cutoff value of the pelvic inlet plane area that predicts anastomotic leakage was determined using a receiver operating characteristic (ROC) curve. RESULTS: We observed anastomotic leakage in 10 (8.5%) of the 117 patients. In the multivariate analysis, we identified high body mass index (odds ratio 1.674; 95% confidence interval: 1.087-2.58; P = 0.019) and smaller pelvic inlet plane area (odds ratio 0.998; 95% confidence interval: 0.997-0.999; P = 0.012) as statistically significant risk factors for anastomotic leakage. According to the receiver operating characteristic curves, the optimal cutoff value of the pelvic inlet plane area was 10074 mm2. Narrow pelvic inlet plane area (≤ 10074 mm2) predicted anastomotic leakage with a sensitivity of 90%, a specificity of 85.9%, and an accuracy of 86.3%. CONCLUSION: Narrow pelvic inlet and obesity were independent risk factors for anastomotic leakage after ISR. Anastomotic leakage after ISR may be predicted from a narrow pelvic inlet plane area (≤ 10074 mm2).

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BACKGROUND: The squatting birth position is widely used for "natural" birth or in countries where childbirth occurs in non-medical facilities. Squatting birth positions, like others, are roughly defined so a biomechanical assessment is required with the availability of noninvasive technology in pregnant women. In practice, we can observe spontaneously two kinds of squatting birth position: on tiptoes and with feet flat. OBJECTIVE: To compare the impact of foot posture on biomechanical parameters considered essential in obstetrical biomechanics during a squatting birth position: on tiptoes versus with feet flat on the floor. STUDY DESIGN: Thirteen pregnant women beyond 32 weeks of gestational age who were not in labor were assessed during squatting birth position firstly spontaneously and secondly with the foot posture that was not taken spontaneously (on the tiptoes vs with feet flat). For each position, ANGle of flexion on the spine of the plane of the pelvis external conjugate (ANGec), hip flexion and abduction, and lumbar curve were assessed using an optoelectronic motion capture system and a biomechanical model adapted from the conventional gait model as well as a measuring system of the lumbar curve. RESULTS: Spontaneously, 11 out of 13 women squatted on tiptoe at the first test. On tiptoes the hip flexion was lower than with feet flat (p < 0.02), whereas hip abduction was not significantly different (p = 0.28). A lower ANGec angle (p = 0.003) was noticed for the tiptoe position than feet flat. The lumbar curve (lordosis) was more marked for the squatting position on tiptoes than for the position with feet flat (p < 0.001). On tiptoes no woman had a pelvic inlet plane perpendicular to the spine and none had a flat back or kyphosis. No woman on tiptoes fulfilled the two conditions necessary for the position that we consider optimal. CONCLUSION: In squatting birth position, foot posture has a biomechanical impact on lumbar curve and pelvic orientation. When comparing squatting positions (on tiptoes vs feet flat), feet flat on the ground is closer to optimal birth conditions than on tiptoes.

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