Paper focuses on biomechanics, specifically on locking cortical bone screws in angularly stable plates used for the treatment of bone fractures in the medical fields of traumatology and orthopaedics. During extraction of titanium-alloy implants, problems are encountered in an effort to loosen some locking bone screws from the locking holes of an angularly stable plate and the subsequent stripping of the internal hexagon of the screw head. The self-locking of the screw-plate threaded joint was verified by calculation and the effect of the angle of the thread on the head of the locking cortical bone screw on self-locking was evaluated. The magnitude of the torque, causing the stripping of the internal hexagon (the Inbus type head) of a locking cortical bone screw with a shank diameter of 3.5 mm from Ti6Al4 V titanium alloy to ISO 5832-3, was determined experimentally. Also, it was experimentally found that the rotation of the screwdriver end with a hexagonal tip inside the locking cortical bone screw head during stripping of the internal hexagon causes strain of the screw head perimeter and thereby an increase of thread friction. The effect of tightening torque on the possibility of loosening of the locking cortical bone screw from the locking hole of an angularly stable plate was assessed experimentally. From the evaluation of five alternative shapes of locking cortical bone screw heads in terms of the acting stress and generated strains, it follows that the best screw is the screw with the Torx type head, which demonstrates the lowest values of reduced stress and equivalent plastic strain. Based on experiments and simulations the authors recommend that all global producers of locking cortical bone screws for locking holes of angularly stable plates use the Torx type heads, and not heads of the Inbus type or the Square, PH, PZ types.

Background: A Jones fracture is a transverse fracture of the V. metatarsal bone, without significant dislocation in the diaphysis junction and metaphyseal metaphysis. This type of fracture is usually associated with a minimal injury mechanism, and is characterized with minimal swelling, absence of hematoma and prolonged healing. The aim of the presented study was to compare the surgical and conservative therapy of Jones fracture. The study was registered in the www.clinicaltrials.gov database, under the ClinicalTrials.gov ID: NCT04037540 on 27th July 2019. Methods: A total of 27 study subjects were randomized into two groups – Conservative (K): 12, and Operational (O): 15. The study subjects were followed after 6 and 12 weeks using X-ray and the American Orthopedic Foot and Ankle Score (AOFAS). In the absence of X-ray signs of healing and low AOFAS score in Group K, treatment was considered unsuccessful and the patient was indicated for surgical treatment. Results: Five patients in Group K showed no signs of healing on X-ray after 12 to 6 weeks. These patients also manifested poor AOFAS scores and were indicated for surgical treatment and excluded from the study. Fracture failure was observed in seven patients. Their AOFAS scores were at the least satisfactory and, the patients continued in conservative therapy. After 12 weeks, 6 patients manifested fracture healing on X-ray and the AOFAS score of 100. In one patient who refused surgery, the fracture was not healed after 12 weeks. In Group O, seven patients achieved fracture healing on X-ray after 6 weeks, 8 patients did not show fracture healing. The average AOFAS score after 6 weeks was 97 (excellent). After 12 months, 13 patients showed findings of fracture healing on X-ray. The average AOFAS score was 100 points (maximum). Conclusions: The results of the study show that 1) Surgical treatment leads to significantly faster signs of healing on X-ray than the conservative one 2) After six weeks of surgery, 93% (14 out of 15) of patients are able to fully load the limb. Keywords: Jones - Fracture - AOFAS - Herbert screw Unique protocol ID: FNO-KUCH-01-Jones

Background: The standard ATLS protocol calls for chest drain insertion in patients with hemothorax before performing further diagnostic steps. However, if trauma-induced thoracic aortic rupture is the underlying cause, such drainage can lead to massive bleeding and death of the patient. Case report: This report describes a case of a polytrauma patient (car accident), aged 21, with symmetrical chest and decreased breath sounds dorsally on the left. An urgent CT scan revealed subadventitial Grade III thoracic aortic transection with mediastinal hematoma, a massive left-sided hemothorax with mediastinal shift to the right, and other injuries. Stent-graft implantation with subsequent left hemithorax drainage was urgently performed, during which the patient became increasingly unstable from the circulatory point of view. This traumatic hemorrhagic shock was successfully managed at the ICU. Conclusion: Although hemothorax is a serious condition requiring rapid treatment, the knowledge of its origin is of utmost importance; performing chest drainage without bleeding control can lead to circulatory instability and death of the patient. Hence, where aortic injury can be suspected based on the mechanism of the injury, it is beneficial to perform spiral CT angiography for accurate diagnosis first and, in cases of aortic injury, to control the bleeding prior to drainage.

PURPOSE OF THE STUDYFifth metatarsal fractures, in particular so-called Jones fractures, are relatively common injuries both in the general population and athletes. Although discussions about whether the surgical or conservative solution should be preferred are ongoing for decades, there is no clear consensus. Here, we aimed to prospectively compare the results of osteosynthesis using the Herbert screw with the conservative solution in patients from our department. MATERIAL AND METHODSPatients 18-50 years presenting to our department with Jones fracture and meeting further inclusion/exclusion criteria were offered participation in the study. Those willing to participate signed informed consent and were randomized by flipping the coin into surgically and conservatively treated groups. After six and twelve weeks, X-ray was performed in each patient and AOFAS score was determined. Conservatively treated patients who showed no signs of healing and whose AOFAS was below 80 after six weeks were offered surgery again. RESULTSOf 24 patients in total, 15 were assigned to the surgically treated group and nine were treated conservatively. After six weeks, AOFAS score of all but two patients (86%) in the surgically treated group ranged between 97 and 100, while this score exceeded 90 points only in three patients (33%) from the conservatively treated group. On X-ray, successful healing after six weeks was observed in seven patients (47%) from the surgically treated group but in none of the patients from the conservatively treated group. Three out of five patients in the conservative group whose AOFAS was below 80 after six weeks opted for surgery at that time and all improved significantly by the twelfth week. DISCUSSIONAlthough studies on surgical treatment of Jones fracture using various screws or plates are not rare, we present an uncommon method of surgical treatment of this injury -the use of the Herbert screw. The results of this method are excellent and even on a relatively small sample yielded statistically significantly better results than conservative treatment. Moreover, the surgical treatment facilitated early loading of the injured limb, which allows an earlier return of the patients to normal life. CONCLUSIONSOsteosynthesis using Herbert screw in Jones fracture yielded significantly better results than conservative treatment.