ObjectiveThis study aims to optimize iliolumbar fixation strategies for unilateral vertical sacral fractures via finite element analysis, by comparing stability, implant stress, and lumbar mobility to identify the optimal clinical option.MethodsA finite element model of the pelvis and L3-L5 lumbar spine was constructed to simulate four fixation models (L4L5IS, L5S1IS, L5IS, S1IS) under a 600 N vertical load. Sacral vertical displacement, implant stress, and fracture line separation were analyzed.ResultsDouble-segment fixation (L4 + L5 + iliac screw and L5 + S1 + iliac screw) demonstrated superior sacral stability compared to single-segment fixation (L5 + iliac screw and S1 + iliac screw). The L5 + S1 + iliac screw configuration achieved the best balance of stability and lumbar mobility. Stress concentrations were primarily observed at iliac screw connectors, but all models remained within safe mechanical limits.ConclusionsDouble-segment fixation, particularly the L5 + S1 + iliac screw model, is recommended for optimal sacral stability. For cases with compromised S1 pedicles, L4 + L5 + iliac screw fixation is a reliable alternative. Short-segment fixation is viable when prioritizing lumbar mobility.

Objective:To summarize the morphological characteristics of sagittal beak-like deformity of head-neck fragment in femoral intertrochanteric fractures and to investigate the technical skills in fracture reduction. Methods:A clinical data of 31 patients with femoral intertrochanteric fractures between May 2021 and April 2023 was retrospectively analyzed. The fractures had sagittal beak-like deformity of head-neck fragment in all patients. There were 13 males and 18 females, with an average age of 76.2 years (range, 68-83 years). The time from injury to operation was 36-76 hours (mean, 51.2 hours). Fractures were classified as type A1.2 in 10 cases, type A1.3 in 11 cases, type A2.2 in 6 cases, and type A2.3 in 4 cases according to the AO/Orthopaedic Trauma Association (AO/OTA)-2018 classification; and as type A1.3 in 10 cases, type A2.1 in 11 cases, type A2.2 in 6 cases, type A2.3 in 2 cases, and type A2.4 in 2 cases according to a novel comprehensive classification for femoral intertrochanteric fractures proposed by the "Elderly Hip Fracture" Research Group of the Reparative and Reconstructive Surgery Committee of the Chinese Rehabilitation Medical Association. Based on preoperative X-ray films, CT scan and three-dimensional reconstruction, the fractures were classified into two types: type 1 (14 cases), with uncomplicated fracture morphology, severe bone interlocking and (or) soft tissue incarceration; type 2 (17 cases), with severe fracture crushing, obvious dissociation between bone blocks, and severe soft tissue hinge destruction. After the failure of the closed reduction, all patients underwent fracture reduction assisted with instrument via anterior minimal incision and proximal femoral nail antirotation nails internal fixation. The operation time, intraoperative fluoroscopy, intraoperative visible blood loss, length of hospital stay, and incidence of complications were recorded. The fracture reduction quality and stability score were assessed at immediate after operation under fluoroscopy. The fracture healing was evaluated and healing time was recorded by X-ray films. The pain visual analogue scale (VAS) score was performed at 48 hours after operation and Parker-Palmer activity score at 3 months after operation for function evaluation. Results:The operation time was 39-58 minutes (mean, 46.3 minutes); fluoroscopy was performed 13-38 times (mean, 23.5 times) during operation; the intraoperative visible blood loss was 45-90 mL (mean, 65.3 mL). The fracture reduction quality and stability score were rated as good in 29 cases and acceptable in 2 cases. The pain VAS score was 2-6 (mean, 3.1) at 48 hours after operation. Eleven patients developed deep vein thrombosis of the lower limbs after operation. Patients were hospitalized for 6-10 days (mean, 7.3 days). All patients were followed up 5-8 months (mean, 6.5 months). All fractures healed at 3.5-8.0 months after operation (mean, 4.5 months). Parker-Palmer activity score at 3 months after operation was 9 in 28 cases and 6 in 3 cases. Conclusion:The femoral intertrochanteric fracture with sagittal beak-like deformity of head-neck fragment is difficult to manually reduce. The pin combined with cannulated screw insertion to the neck cortex can hold the fragment and assist fracture reduction, which is a simple and effective technique.

To compare the biomechanical properties of several anterior pelvic ring external fixators with two new configurations in the treatment of Tile C pelvic fractures, in order to evaluate the effectiveness of the new configurations and provide a reference for their clinical application. A finite element model of a Tile C pelvic ring injury (unilateral longitudinal sacral fracture and ipsilateral pubic fracture) was constructed. The pelvis was fixed with iliac crest external fixator (IC), anterior inferior iliac spine external fixator (AIIS), combination of IC and AIIS, combination of anterior superior iliac spine external fixator (ASIS) and AIIS, and S1 sacroiliac screw in 5 types of models. The stability indices of the anterior and posterior pelvic rings under vertical longitudinal load, left-right compression load and anterior-posterior shear load were quantified and compared. In the simulated bipedal standing position, the results of the vertical displacement of the midpoint on the upper surface of the sacrum are consistent with the displacement of the posterior rotation angle, and the order from largest to smallest is IC, AIIS, ASIS + AIIS, IC + AIIS and S1 screw. The longitudinal displacement of IC is greater than that of the other models. The displacements of ASIS + AIIS and IC + AIIS are similar and the latter is smaller. In the simulated semi-recumbent position, the vertical displacement and posterior rotation angle displacement of the midpoint on the upper surface of the sacrum are also consistent, ranking from large to small: IC, AIIS, ASIS + AIIS, IC + AIIS and S1 screw. Under the simulated left-right compression load state, the lateral displacements of the highest point of the lateral sacral fracture end are consistent with the highest point of the lateral pubic fracture end, and the order from large to small is S1 screw, IC, AIIS, ASIS + AIIS and IC + AIIS, among which the displacements of S1 screw and IC are larger, and the displacements of ASIS + AIIS and IC + AIIS are similar and smaller than those of other models. The displacements of IC + AIIS are smaller than those of ASIS + AIIS. Under the simulated anterior-posterior shear load condition, the posterior displacements of the highest point of the lateral sacral fracture end and the highest point of the lateral pubic fracture end are also consistent, ranking from large to small: IC, AIIS, ASIS + AIIS, IC + AIIS and S1 screw. Among them, the displacements of IC and AIIS are larger. The displacements of ASIS + AIIS and IC + AIIS are similar and the latter are smaller. For the unstable pelvic injury represented by Tile C pelvic fracture, the biomechanical various stabilities of the combination of IC and AIIS are superior to those of the external fixators of conventional configurations. The biomechanical stabilities of the combination of ASIS and AIIS are also better than those of the external fixators of conventional configurations, and slightly worse than those of the combination of IC and AIIS. Compared with sacroiliac screw and conventional external fixators, the lateral stabilities of IC + AIIS and ASIS + AIIS are particularly prominent.

To compare the stability and biomechanical characteristics of four commonly used triangular osteosynthesis techniques to treat unilateral vertical sacral fractures and provide a clinical application reference. Finite element models of Tile C-type pelvic ring injury (unilateral Denis II sacral fracture) were produced. In four models, sacral fractures were fixed with a combination of unilateral L5, unilateral L4, and L5 iliac lumbar fixation with lengthened or normal sacroiliac screws. The biomechanical properties of the four fixation models were measured and compared under bipedal stance and lumbar rotation. The fixation stability of the model with the lengthened sacroiliac screw was excellent, and the fracture end was stable. The stability of fixation using unilateral L4 and L5 segments was close to that of unilateral L5 segment fixation. Triangular osteosynthesis transverse stabilization devices using lengthened sacroiliac screws can increase the vertical stability of the sacrum after internal fixation and increase the stability of the fracture. When triangular osteosynthesis lumbar fixation segments were selected, simultaneous fixation of L4 and L5 segments versus only L5 segments did not significantly enhance the vertical stability of the sacrum or the stability of the fracture end.

[Objective] To examine the impact of altering the sacroiliac screw's position and length on the biomechanical properties of the triangle osteosynthesis used to treat unilateral vertical sacral fractures and serve as a clinical reference. [Methods] Unilateral sacral fractures of the Denis II type were modeled using finite elements to represent Tile C pelvic ring injuries. Six sacroiliac screws combined with lumbar-iliac fixation patterns were used to fix the sacral fracture. To compare sacral stability, maximum pressure, and stress distribution after fixation of sacral fractures with each internal fixation modality. [Results] The best vertical stability of the internal fixation model was achieved when the S1 segment was fixed with lengthened sacroiliac screws. This was followed by using normal sacroiliac screws for the S1 segment. There was no statistical difference between the vertical stability of the S1 plus S2 dual-segment fixation model and the S1-segment fixation model.The maximum pressures under a vertical force of 600 N, L5LS1 <L5NS1<L5S1S2<L5LS2<L5NS2<L5NS1S2. [Conclusions] In unilateral vertical fracture of the sacrum (AO C3.1 DENISS II) treated with triangular osteosynthesis, using triangular jointing combined with unilateral iliolumbar fixation + sacroiliac screw fixation, it is recommended that the best vertical stability of the sacrum is obtained with a single lengthened sacroiliac screw for the S1 segment, with less maximum compression on the internal fixation. If it is not possible to apply a lengthened sacroiliac screw, it is recommended to use a plain sacroiliac screw for the S1 segment. Adding an S2 segment screw does not significantly increase the vertical stability of the sacrum.

Abstract [Objective] To examine the impact of altering the sacroiliac screw's position and length on the biomechanical properties of the triangle osteosynthesis used to treat unilateral vertical sacral fractures and serve as a clinical reference. [Methods] Unilateral sacral fractures of the Denis II type were modeled using finite elements to represent Tile C pelvic ring injuries. Six sacroiliac screws combined with lumbar-iliac fixation patterns were used to fix the sacral fracture. To compare sacral stability, maximum pressure, and stress distribution after fixation of sacral fractures with each internal fixation modality. [Results] The best vertical stability of the internal fixation model was achieved when the S1 segment was fixed with lengthened sacroiliac screws. This was followed by using normal sacroiliac screws for the S1 segment. There was no statistical difference between the vertical stability of the S1 plus S2 dual-segment fixation model and the S1-segment fixation model.The maximum pressures under a vertical force of 600 N, L5LS1 [Conclusions] In unilateral vertical fracture of the sacrum (AO C3.1 DENISS II) treated with triangular osteosynthesis, using triangular jointing combined with unilateral iliolumbar fixation + sacroiliac screw fixation, it is recommended that the best vertical stability of the sacrum is obtained with a single lengthened sacroiliac screw for the S1 segment, with less maximum compression on the internal fixation. If it is not possible to apply a lengthened sacroiliac screw, it is recommended to use a plain sacroiliac screw for the S1 segment. Adding an S2 segment screw does not significantly increase the vertical stability of the sacrum.

Objective To examine the impact of sacroiliac screw position and length on the biomechanical properties of triangular osteosynthesis in treating unilateral vertical sacral fractures and provide a clinical reference. Methods Unilateral Denis type II sacral fractures were modelled using finite elements to represent Tile C pelvic ring injuries. Six sacroiliac screws were used with iliolumbar fixation patterns to fix the sacral fractures, and the sacral stability, maximum pressure, and stress distribution were compared among the internal fixation modalities. Results The best vertical stability of the internal fixation model was achieved when the S1 segment was fixed with lengthened sacroiliac screws, followed by when the S1 segment was fixed using normal sacroiliac screws. There was no significant difference in vertical stability between the S1 + S2 dual-segment fixation model and the S1-segment fixation model. The maximum pressure under a vertical force of 600 N showed a trend of L5LS1 < L5NS1 < L5LS12 < L5LS2 < L5NS2 < L5NS12. Conclusions In unilateral vertical sacral fractures (Denis II) treated with triangular osteosynthesis using triangular jointing combined with unilateral iliolumbar + sacroiliac screw fixation, the use of a single lengthened sacroiliac screw for the S1 segment is recommended to achieve the best vertical stability of the sacrum with less maximum compression on the internal fixation components. If it is not possible to apply a lengthened sacroiliac screw, the use of a normal sacroiliac screw for the S1 segment is recommended. Adding an S2 screw does not significantly increase the vertical stability of the sacrum.

The present study aimed to evaluate the clinical efficacy of the bilateral pedicle cement anchoring technique combined with the postural reduction in percutaneous vertebroplasty (PVP) for Kümmell disease. For this purpose, a retrospective study was performed on 18 patients with Kümmell disease who between January 2018 and June 2021 underwent bilateral pedicle cement anchoring combined with postural reduction in PVP. Pre- and post-operative bone mineral density, injected cement volume, visual analogue scale (VAS) values, Oswestry disability index (ODI) scores, Cobb angle measurements and anterior vertebral height (AVH) were recorded and assessed. The mean follow-up duration was 8.4±1.2 months. The average VAS score decreased from 8.17±0.71 pre-operatively to 1.56±0.62 post-operatively and remained at 2.00±0.91 at the final follow-up visit (P<0.05). The average ODI improved from 86.44±5.5 pre-operatively to 24.33±7.82 post-operatively. Until the last follow-up, the ODI remained at 27.11±8.76 (P<0.05). Similarly, the changes in the Cobb angle and AVH before and after surgery were also statistically significant in the radiological evaluation (P<0.05). During the follow-up, two patients experienced adjacent vertebral fractures. The loosening of cement was not found. Overall, the present study demonstrated that during the treatment of Kümmell disease with PVP, the bilateral pedicle cement anchoring technique combined with postural reduction can achieve good clinical outcomes.

Objective To compare the breakage risk of lengthened sacroiliac screws and ordinary sacroiliac screws to treat unilateral vertical sacral fractures and provide a reference for clinical application. Methods A finite element model of Tile C pelvic ring injury (unilateral type Denis II fracture of the sacrum) was produced. The sacral fractures were fixed with a lengthened sacroiliac screw and ordinary sacroiliac screw in 6 types of models. The maximal von Mises stresses and stress distributions of the two kinds of screws when standing on both feet were measured and compared. Results The maximal von Mises stress of the lengthened screw was less than that of the ordinary screw. Compared with ordinary screw, the stress distribution in the lengthened screw was more homogeneous. Conclusions The breakage risk of screws fixed in double segments is lower than that of screws fixed in single segments, the breakage risk of lengthened screws is lower than that of ordinary screws, and the breakage risk of screws fixed in S2 segments is lower than that of screws fixed in S1 segments.

Abstract [Objective] To examine the impact of altering the sacroiliac screw's position and length on the biomechanical properties of the triangle osteosynthesis used to treat unilateral vertical sacral fractures and serve as a clinical reference. [Methods] Unilateral sacral fracture of type Denis II was modeled using finite elements to represent the Tile C pelvic ring damage. Fixation of sacral fractures using six triangular osteosynthesis patterns. To compare sacral stability, fracture separation values and maximum von Misses stress of internal fixation after fixation of sacral fractures by each internal fixation mode. [Results] The best vertical stability occurs with lengthened sacroiliac screws for simultaneous fixation of S1S2 segments. Moreover, the fracture separation value was the smallest, the internal fixation stress distribution was uniform, and the maximum von Mills stress of internal fixation was the minimum. [Conclusions] In unilateral vertical fracture of the sacrum (AO C3.1 DENISS II) treated with triangular osteosynthesis, S1-segment + S2-segment extended sacroiliac screw fixation results in optimal vertical sacral stability, fracture end stability, uniform internal fixation stress, and a lower risk of screw fracture. If only single-segment sacroiliac screws can be used, S1-segment extended sacroiliac screw fixation performs better.

OBJECTIVE:To study the relationship between the pelvic external branches of the superior gluteal artery and the entry area of the S2 sacroiliac screw to provide the anatomical basis and technical reference for avoiding the superior gluteal artery injury during the clinical screw placement.METHODS:CTA imaging of superior gluteal artery of 74 healthy adults (37 males and 37 females) was randomly selected. The safe bony entry area ('safe area' for abbreviation) of S2 sacroiliac screw in the standard lateral view of the pelvis three-dimensional reconstruction CT image was determined by the CT auxiliary measurement software. The relationship between the pelvic external branches of the superior gluteal artery and the safe area of S2 sacroiliac screw was observed, and the cases in which the artery intersected the safe area were counted. The distance between the safe area and the superior gluteal artery branches closest to it was measured for the cases in which the artery and the safe area did not intersect.RESULTS:21 of the 74 cases did not have a bone channel of horizontal S2 sacroiliac screw, so they were excluded from this study. In the remaining 53 cases, 12 cases had the deep superior branch of the superior gluteal artery through the safe area of S2 screw (22.6%), and 16 cases had the superficial branch of the superior gluteal artery through the safe area of S2 screw (30.2%). There was no obvious overlap feature and law between the safe area and the superficial and deep superior branches. In 20 cases of the 53 cases, the safe area of S2 screw was located between the deep superior branch and the superficial branch of superior gluteal artery (37.7%), and in 5 cases, the safe area of S2 screw was located behind the superficial branch of superior gluteal artery (9.4%). In the cases where the superior gluteal artery did not intersect the screw entry bony safe area, the part of superior gluteal artery closest to the safe area was located in front or back of the widest part of the safe area.CONCLUSION:The risk of accidental injury of the deep superior branch and superficial branch of the superior gluteal artery is high during the process of S2 sacroiliac screw placement. Even if the screw entry point is located in the bony safe area, the absolute safety of screw placement cannot be guaranteed. We strongly suggest that a careful and thorough plan is needed before surgery.

Objective:To investigate the clinical efficacy of hyperbaric oxygen(HBO) combined with vacuum sealing drainage (VSD) in the treatment of 46 patients with early osteofascial compartment syndrome (OCS), and to analyze the value of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) for prognostic prediction.Methods:A total of 46 patients with early OCS admitted to the Department of Orthopedics of Yantai Mountain Hospital from September 2015 to March 2020 were retrospectively analyzed. According to the treatment methods, they were divided into observation group ( n=46) and control group ( n=43). The control group was treated with VSD and conventional symptomatic treatment, while the observation group was treated with HBO on the basis of the treatments of the control group. The clinical efficacy was compared after 3 courses of treatment. The pain was graded before and after treatment by visual analogue scale (VAS); the time of swelling subsiding and length of hospital stay were respectively recorded; the freshness and infection of granulation tissue at the incision site of the affected limb were observed, and primary suture or secondary skin grafting was conducted based on evaluation; enzyme linked immunosorbent assay (ELISA) was applied to measure the levels of serum TNF-α and IL-6 at different time points for the prediction of the development of the disease. Results:After 3 courses of treatment, the effective rate of the observation group (97.8%) was significantly higher than that of the control group (81.4%) ( P<0.05). The secondary skin grafting rate in the observation group (53.5%) was significantly lower than that in the control group (21.7%), and the rate of granulation tissue without infection (80.4%) was significantly higher than that of the control group (51.2%) ( P<0.05). The time of swelling subsiding [(13.14 ±3.42)d] and length of hospital stay [(16.55±3.52)d] in the observation group were significantly lower than those in the control group [time of swelling subsiding: (22.39 ±4.48)d; length of hospital stay: (26.87±5.51)d] ( P<0.05). The VAS scores of the observation group were significantly lower than those of the control group on the 7th, 14th, and 21st days after operation ( P<0.05). The levels of serum TNF-α and IL-6 in the observation group were significantly lower than those in the control group on the 7th and 14th days after operation ( P<0.05), but no significant difference was observed on the 21st day ( P>0.05). Conclusion:HBO combined with VSD in the treatment of early OCS can improve the blood circulation of the affected limb, reduce the incidence of incision infection, promote wound healing, and reduce limb pain, so as to improve the curative effect.

Background To compare the mechanical characteristics of a percutaneous superior pubic intramedullary screw, percutaneous bridging plate and percutaneous screw-rod system of the anterior ring for the treatment of unilateral vertical pubic fractures to provide a reference for clinical application. Methods A finite element model of pelvic anterior ring injury (unilateral vertical pubic fracture) was produced. The fractures were fixed with a percutaneous superior pubic intramedullary screw, percutaneous bridging plate and percutaneous screw-rod system of the anterior ring and their combinations in 5 types of models. The fracture stabilities under vertical, bilateral and anterior-posterior load were quantified and compared based on the displacement of the hip joints' midpoint as quantificational index of fracture stability. Results In the condition of bilateral and anterior-posterior load, the vertical, bilateral and anterior-posterior displacements of the hip joints' midpoint of different models were significantly different respectively. In general, the displacements of the 5 pelvic anterior ring fixations were ranked from maximum to minimum as follows: bridging plate, pelvic anterior screw-rod system, combination of bridging plate and pelvic anterior screw-rod system, superior pubic intramedullary screw and combination of superior pubic intramedullary screw and pelvic anterior screw-rod system. Conclusion For the fixation in unilateral pubic fractures of pelvic ring injury, the percutaneous superior pubic intramedullary screw is optimal, the percutaneous pelvic anterior screw-rod system is the second choice, and percutaneous bridging plate ranks the third. The percutaneous pelvic anterior screw-rod system can significantly increase fixation stability of the percutaneous superior pubic intramedullary screw and the percutaneous bridging plate.

[Objective] To compare the mechanical characteristics of percutaneous long plate, percutaneous pubic superioris intramedullary screw and percutaneous pelvic anterior screw-rod system for the treatment of bilateral vertical pubic fractures to provide reference for clinical application. [Methods] A finite element model of pelvic anterior ring injury (bilateral vertical pubic fracture) was produced. The fractures were fixed with percutaneous long plate, percutaneous pubic superioris intramedullary screw, percutaneous pelvic anterior screw-rod system and their combination in 5 types of models. The fracture stability under vertical, bilateral and anterior-posterior load were quantified and compared based on the displacement of the hip joints’ midpoint as quantificational index of fracture stability. [Results] In condition of bilateral and anterior-posterior load, the vertical, bilateral and anterior-posterior displacement of the hip joints’ midpoint of different models were significantly different respectively. In general, the displacement of the 5 pelvic anterior ring fixation models were ranked from maximum to minimum as follows: long plate, pelvic anterior screw-rod system, combination of long plate and pelvic anterior screw-rod system, pubic superioris intramedullary screw and combination of pubic superioris intramedullary screw and pelvic anterior screw-rod system. [Conclusion] For the fixation in bilateral pubic fractures of pelvic injury, the percutaneous pubic superioris intramedullary screw was optimal, percutaneous pelvic anterior screw-rod system was the second choice, and percutaneous long plate ranked the third. The percutaneous pelvic anterior screw-rod system can significantly increase fixation stability of the percutaneous pubic superioris intramedullary screw and the percutaneous long plate.

Objective: To evaluate the precision of the robot-assisted sacroiliac screw placement for posterior pelvis injury and the impacting factors. Methods: The clinical data of twenty-four cases of posterior pelvic fractures treated by percutaneous sacroiliac screw placement in Yantai shan Hospital from August 2016 to May 2018 were studied retrospectively. There were 17 males and 7 females with a mean age of 44.1 years (ranged from 17 to 71 years). According to AO classification, 17 cases were type B fractures (9 cases of type B1 and 8 type B2), and 7 cases were type C factures (3 cases of type C1, 2 type C2 and 2 type C3). All cases were treated by robot-assisted percutaneous sacroiliac screw placement (AO cannulated screws with a diameter of 7.3 mm). In the posterior pelvic surgeries for the 24 cases, 26 S(1) sacroiliac screws fixations and 18 S(2) sacroiliac screw fixations were placed in total, with single S(1) segmental fixation in 8 cases, single S(2) segmental fixation in 3 cases, S(1) and S(2) combined fixation in 13 cases, S(1) unidirectional one-sided fixation in 18 cases, S(1) bidirectional two-sided fixation in 3 cases, S(2) unidirectional one-sided fixation in 14 cases, S(2) bidirectional two-sided fixation in 2 cases and S(1) unidirectional double screws fixation in 2 cases. X-ray and CT examinations were taken for all 24 cases after operation. The visual analogue scale (VAS) of pain were performed before and after the operation. Results: All the sacroiliac screws were successfully implanted at once as planned with the assistance of the robot. The postoperative X-ray films and CT showed that none of the sacroiliac screws broke through the sacral body and the contralateral sacral wing's frontal cortex nor did they stray into the sacral canal and the intervertebral space. In 3 cases, the sacroiliac screws went closely against and wore out the front edge of iliac cortical density line and sacral alar slope and finally re-entered the sacral body. In 3 cases, sacroiliac screws touched upon the sacral nerve canals but did not break through the nerve canals. The mean VAS of pain was improved from 7.1 points (4-10 points) before the operation to 1.9 points (0-3 points) after. Conclusions: The robot-assisted sacroiliac screw placement shows high precision, and hence is worthy of clinical promotion; however the primary role of the surgeon could not be replaced.

To compare the risk of breakage of lengthened sacroiliac screw and ordinary sacroiliac screw for the treatment of unilateral vertical sacral fractures to provide reference for clinical application. A finite element model of Tile C pelvic ring injury (unilateral type Denis Ⅱ fracture of sacrum) was produced. The sacral fractures were fixed with lengthened sacroiliac screw and ordinary sacroiliac screw in 6 types of models respectively. The maximal Von Mises stresses and stress distribution of the two kinds of screws in the case of standing on both feet were measured and compared. The maximal Von Mises stress of lengthened screw is less than that of ordinary screw. Compared with ordinary screw, the stress distribution in lengthened screw is more homogeneous. In conclusion, the breakage risk of screws fixed in double-segment is lower than that of screws fixed in single-segment, and the breakage risk of lengthened screws is lower than that of ordinary screw, and the breakage risk of screws fixed in S2 segment is lower than that of screws fixed in S1 segment.

Objective: To introduce a robot-assisted modified method of sacroiliac screw path planning in order to reduce the incidence of screw misplacement. Methods: The study involved 13 patients suffering from posterior pelvic injuries treated by percutaneous sacroiliac screw in Yantai Shan Hospital from August 2016 to May 2018. The patients included 9 males and 4 females, aged from 18 to 70 years (mean age 46.2 years). Causes of injury were traffic accidents (n=7), crushing injury (n=4) and fall from height (n=2). According to AO classification, 8 cases were classified with type B fractures (3 with type B1 and 5 with type B2), and 5 cases with type C fractures (2 with type C1, 1 with type C2, 2 with type C3). All the patients were treated by robot-assisted percutaneous sacroiliac screws (AO cannulated screws with a diameter of 7.3 mm) with an improved method of screw path planning. The screw placement time, blood loss, postoperative neurological, vascular and visceral function etc were observed. X-ray and CT were checked in the follow-up after the operation. Visual analogue scale (VAS) score was used to assess the pain degree of patients one week after the surgery. Results: All the sacroiliac screws were successfully implanted once with the robot-assisted improved method of screw path planning. The mean placement time of single screw was 15.9 min and the mean blood loss for single screw placement was less than 1 ml. No clinical manifestations of injuries of blood vessels, internal organs and lumbosacral nerve was found after the operation. The postoperative X-ray films and CT showed that none of the sacroiliac screws wore out the sacral body or the sacral wing's frontal cortex. Also, it was found that none of the sacroiliac screws strayed into the sacral canal and the intervertebral space. The mean VAS score decreased from preoperative 6.9 (4-10) to postoperative 1.8(0-3). Conclusion: The robot-assisted improved method of screw path planning contributes to safe and accurate sacroiliac screw placement.

To conduct radiologic anatomical study on the relation between S1 sacroiliac screws’ entry points and the route of the pelvic outer superior gluteal artery branches with the aim to provide the anatomical basis and technical reference for the avoidance of damage to the superior gluteal artery during the horizontal sacroiliac screw placement.

As a novel discovered myokine, irisin is considered to be a promising candidate for the treatment of metabolic disorders and cancer. However, little is known about the anti-metastasic effect of irisin on osteosarcoma cells and its underlying mechanisms. In the present study, we aimed to explore the effect of irisin on the migration and invasion of osteosarcoma cells and the underlying mechanisms involved. Viability and proliferation of osteosarcoma cells were examined by MTT assay. Then, by using scratch wound healing assay and Transwell assays, we evaluated migratory and invasive ability of the cells, respectively. Moreover, the expression of epithelial-to-mesenchymal transition (EMT) markers were determined by qPCR, western blot and immunofluorescence staining after treatment with IL-6 and irisin. Furthermore, the expression of ERK, p38, STAT3 and Snail were detected by western blot analysis. Finally, an inhibitor of STAT3, WP1066 was applied to testify the effect of irisin on the expression of EMT markers and Snail. It was found that irisin treatment significantly suppressed the proliferation, migration and invasion of osteosarcoma cells. Furthermore, irisin reversed the IL-6-induced epithelial-mesenchymal transition (EMT) in osteosarcoma cells by regulating the expression of E-cadherin, N-cadherin, vimentin, fibronectin, MMP-2, MMP-7 and MMP-9. In addition, irisin suppressed the IL-6-activated phosphorylation of STAT3 and the expression of Snail in osteosarcoma cells. Finally, blockade of STAT3 by WP1066 (a STAT3 inhibitor) further enhanced the effect of irisin on the EMT and Snail expression in osteosarcoma cells. Collectively, our findings revealed that irisin may play a critical role in the IL-6-induced EMT of osteosarcoma cells via the STAT3/Snail signaling pathway.