Investigation on the dust migration behavior and safety zone in the fully mechanized mining face

High dust concentration produced in the fully mechanized longwall mining face is a significant threat to the front-line workers. It is critical to discover the potential safety zone to ensure routine personnel operation. Fluent 2020 R1 is employed to reappear the spatial dust distribution based on the gas-solid coupling theory. The dust migration behavior and safety regional division are illuminated in the spatial longwall mining face. The formation of dust concentration trigonum is introduced with the particle diffusion force analyzed. The YZ plane safety zone area shows an increasing trend at X = 70-95 m. The respirable dust concentration decreases from the peak value to the safe value at sidewalk 4.0-4.6 m. The safety zone area and length both pose a linear growth with the increasing wind velocity. In the XY plane, the safety zone area and length extend by 1.26 times and 1.33 times, respectively. The horizontal plane creates a greater growth rate of safety zone than the vertical plane. The drum rotation creates a wind circumfluence that exerts an obvious effect on the dust distribution around the coal cutter. The sidewalk region mainly situates in the safety zone for the personal squat down, while it is gradually exposed to the dangerous dust pollution situation as the breathing height rises.

Anterior intermeniscal ligament: frequency in MRI studies and spatial relationship to the entry point for intramedullary tibial nailing related to the risk of iatrogenic violation

BACKGROUND

Anterior knee pain is the most common complication after intramedullary tibial nailing. Often, the cause is multifactorial and individually different. Violation of the anterior intermeniscal ligament (AIL) during intramedullary tibial nailing might be a possible origin of postsurgical anterior knee pain. Both the importance and function of the AIL remain somewhat ambivalent, and even the figures quoted in the literature for its existence in the population vary drastically. Our aim was to verify the estimated frequency of the AIL in the literature by retrospectively analysing the data of MRI studies conducted at our hospital. In addition, we attempted to assess the potential risk of AIL violation during intramedullary tibial nailing, based on the spatial arrangement.

METHODS

Two independent examiners analysed the images generated in 351 MRI studies conducted at our hospital between June 2013 and May 2014. All cases who did not reveal any previous knee-joint injury or osteoarthritis of the knee were allocated to group I. All other cases were included in group II. To estimate the potential risk of AIL injury during the nailing procedure, the distance between the AIL and the theoretical entry point for intramedullary nailing was measured.

RESULTS

We identified the AIL on the images of nearly all patients (96.5%) in group I. In group II, the presence of the AIL was confirmed in only 51.4% of cases (p < 0.001). The average distance between the AIL and theoretical entry point for intramedullary tibial nailing was 10.1 mm (range 3.48-18.88 mm).

CONCLUSIONS

Because we were able to confirm the presence of the AIL in nearly all patients without a history of knee joint injuries or osteoarthrosis, we presume that the AIL may play a role in knee joint function. Violation of the AIL during intramedullary nailing appears likely due to the close position of the AIL in relation to the entry point for the inserted nail. As a result and due to its rich sensory innervation, a connection between AIL violation during tibial nailing and postoperative onset of anterior knee pain seems likely. To eliminate one risk factor of anterior knee pain development and in view of the unresolved issues of AIL function, violation of the ligament during any operative procedure should be avoided.

An arthroscopic safety zone for the medial compartment of the hip joint

The purpose of this study was to investigate the safety zone without any neurovascular injury to the medial compartment of hip joint through an anatomical method and describe the relationship of the extra-articular anatomic structures from the surface of the hip joint. Thirty-two fresh specimens from 17 adult Korean cadavers (8 males and 9 females, age range 54-79 years at death) were used for this study. For the measurements, the most superolateral point of the pubic symphysis (PS) and prominent point of the anterior superior iliac spine (ASIS) were identified before dissection. The line connecting the PS and ASIS was defined as a reference line and the PS was a starting point for measurements. All 19 variables measured in this study were related to the femoral head, neck, and surrounding neurovascular structures. The variables were measured according to the x- and y-coordinates in relation to the reference line. The femoral head was generally located 39.5-71.0 mm on the x-coordinate and located 33.5-34.6 mm on the y-coordinate. The junction of the femoral neck and body was located at 52.8 mm on the x-coordinate, and 65.3 mm on the y-coordinate. The junction of the femoral head and neck was located at 47.1 mm on the x-coordinate, and 51.4 mm on the y-coordinate. The location of the medial compartment of the hip joint was located from 38.0 to 43.0 % on the x-coordinate and located from 5.1 to 6.5 cm. These results of this study provide detailed anatomy for arthroscopic hip surgeons.

Analyzing road design risk factors for run-off-road crashes in The Netherlands with crash prediction models

PROBLEM

About 50% of all road traffic fatalities and 30% of all traffic injuries in the Netherlands take place on rural roads with a speed limit of 80 km/h. About 50% of these crashes are run-off-road (ROR) crashes. To reduce the number of crashes on this road type, attention should be put on improving the safety of the infrastructure of this road type. With the development of a crash prediction model for ROR crashes on rural roads with a speed limit of 80 km/h, this study aims at making a start in providing the necessary new tools for a proactive road safety policy to road administrators in the Netherlands.

METHOD

The paper presents a basic framework of the model development, comprising a problem description, the data used, and the method for developing the model. The model is developed with the utilization of generalized linear modeling in SAS, using the Negative Binomial probability distribution. A stepwise approach is used by adding one variable at a time, which forms the basis for striving for a parsimonious model and the evaluation of the model. The likelihood ratio test and the Akaike information criterion are used to assess the model fit, and parameter estimations are compared with literature findings to check for consistency.

RESULTS

The results comprise two important outcomes. One is a crash prediction model (CPM) to estimate the relative safety of rural roads with a speed limit of 80 km/h in a network. The other is a small set of estimated effects of traffic volume and road characteristics on ROR crash frequencies.

PRACTICAL APPLICATIONS

The results may lead to adjustments of the road design guidelines in the Netherlands and to further research on the quantification of risk factors with crash prediction models.

The influence of sacral morphology on the existence of secure S1 and S2 transverse bone corridors for iliosacroiliac screw fixation

Sacroiliac (SI) screw fixation for unstable pelvic fractures stands out as the only minimally invasive method among all other ORIF procedures. A strictly transverse screw trajectory is needed for central or bilateral fracture patterns up to a complete iliosacroiliac fixation. However, secure screw insertion is aggravated by a narrow sacroiliac bone stock. This study investigates the influence of a highly variable sacral morphology to the existence of S1 and S2 transverse corridors. The analysis contained in this study is based on 125 CT datasets of intact human pelvises. First, sacral dysplasia was identified using the "lateral sacral triangle" method in a lateral 3-D semi-transparent pelvic view. Second, 3-D corridors for a 7.3mm screw in the upper two sacral levels were visualised using a proprietary IT workflow of custom-made programme scripts based on the Amira(®)-software. Shape-describing measurement variables were calculated as output variables. The results show a significant linear correlation between ratioT and the screw-limiting S1 isthmus height (Pearson coefficient of 0.84). A boundary ratio of 1.5 represented a positive predictive value of 96% for the existence of a transverse S1-corridor for at least one 7.3mm screw. In 100 out of 125 pelvises (80%), a sufficient S1 corridor existed, whereas in 124 specimens (99%), an S2 corridor was found. Statistics revealed significantly larger S1 and S2 corridors in males compared to females (p<0.05). However, no gender-related differences were observed for clinically relevant numbers of up to 3 screws in S1 and 1 screw in S2. The expanse of the S1 corridor is highly influenced by the dimensions of the dysplastic elevated upper sacrum, whereas the S2 corridor is not affected. Hence, in dysplastic pelvises, sacroiliac screw insertion should be recommended into the 2nd sacral segment. Our IT workflow for the automatic computation of 3-D corridors may assist in surgical pre-operative planning. Furthermore, the workflow could be implemented in computer-assisted surgery applications involving pelvic trauma.

Pedicle morphometry for thoracic screw fixation in ethnic koreans : radiological assessment using computed tomographic myelography

OBJECTIVE

In the thoracic spine, insertion of a pedicle screw is annoying due to small pedicle size and wide morphological variation between different levels of the spine and between individuals. The aim of our study was to analyze radiologic parameters of the pedicle morphometry from T1 to T8 using computed tomographic myelography (CTM) in Korean population.

METHODS

For evaluation of the thoracic pedicle morphometry, the authors prospectively analyzed a consecutive series of 26 patients with stable thoracic spines. With the consent of patients, thoracic CTM were performed, from T1 to T8. We calculated the transverse outer diameters and the transverse angles of the pedicle, distance from the cord to the inner cortical wall of the pedicle, and distance from the cord to the dura.

RESULTS

Transverse outer pedicle diameter was widest at T1 (7.66 +/- 2.14 mm) and narrowest at T4 (4.38 +/- 1.55 mm). Transverse pedicle angle was widest at T1 (30.2 +/- 12.0 degrees ) and it became less than 9.0 degrees below T6 level. Theoretical safety zone of the medial perforation of the pedicle screw, namely, distance from the cord to inner cortical wall of the pedicle was more than 4.5 mm.

CONCLUSION

Based on this study, we suggest that the current pedicle screw system is not always suitable for Korean patients. Computed tomography is required before performing a transpedicular screw fixation at the thoracic levels.