UNASSIGNED: Traditional pedicle screws (TPSs) and cortical based trajectory pedicle screws each apply stability with fusions of the lumbar spine and have shown good success. However, the technical considerations of each technique imply complications of loosening and failure that either technique is uniquely prone to having. The current study proposes a new pedicle screw technique through the articular surface of the vertebral superior facet. It is hypothesized that this path will allow utilization of a larger screw that rivals that of the TPS technique, while also maintaining the high-density bone encountered in the cortical based trajectory technique.
UNASSIGNED: Retrospective review of 50 consecutive trauma patients that underwent lumbar computed tomography (CT) scans at a Level 1 Trauma Center in the age range 18-45. These scans were uploaded to Brainlab software for ideal starting point and trajectory mapping of pedicle screws coursing through each superior facet and pedicle of vertebral levels L1-S1 without cortical breach. Satisfactory pedicle screw variables consisted of a medial angle <10 degrees, screw length at least 30 mm, screw width at least 5.0 mm, and starting point measurements such as distance to the inferior articular surface and distance to the lateral articular surface.
UNASSIGNED: A total of 600 virtual pedicle screws were placed, in which 525 were satisfactory and measured with the above variables. The pedicle widths were shown to significantly widen with lower-level vertebra in the lumbar spine. Approximately 72% of unsuccessful pedicle screws were placed in levels L1 and L2 allowing wider pedicle screws to be placed more further down the vertebral column.
UNASSIGNED: The articular surface technique (AST) for pedicle screw placement is a viable alternative in lumbar spinal fusions that offers decreased soft tissue dissection. However, the technique is likely better suited for lower lumbar fusions in L3 to S1.

Clinical fixation screws are common in clinical practices to fix mandibular condyle fractures. Evidence suggests significance of \'working length\' that is, distance between proximal and distal fixation screws in proximity to the fracture in orthopaedic implant design. In pursuit of stable implant-bone construct, this study aims to investigate the biomechanical performance of each configuration considered in the study and provide an optimal working length between the screws for clinical reference. Finite element models of virtually designed broken condyle as type \'B\' were simulated and analysed in ANSYS Workbench. Screws are implanted according to previous literature at five varied distances \'d\' maintaining five different ratios with the fracture length \'D\'. Based on a literature review, boundary conditions, muscle traction forces and non-linear contacts were assigned to obtain precise results. Each case is considered an individual configuration and von Mises distribution, microstrain in bone, screw-bone interface micromotion and fracture dislocation were evaluated for all these configurations. Stress-shielding phenomenon is observed for maximum von Mises stresses in bone. Microstrain concentration was significant in cancellous bone in the vicinity of the screw around the fracture line. Configurations were compared based on the stress-strain along with micromotion to support the required amount of osseointegration between implant and bone. Presented data from all five conditions supported the assumption that under physiological loading conditions, the D3 configuration provided stability for fracture healing. Further research on screw shapes, diameters and material properties, or investigating the direction of forces within the screws could provide further insight into this topic.

Second-generation headless compression screws (HCSs) are commonly used for the fixation of small bones and articular fractures. However, there is a lack of biomechanical data regarding the application of such screws to radial head fractures. This study evaluated the mechanical properties of the fixation of radial head fractures using a single oblique HCS compared with those obtained using a standard locking radial head plate (LRHP) construct and a double cortical screw (DCS) construct. Radial synbone models were used for biomechanical tests of HCS, LRHP, and DCS constructs. All specimens were first cyclically loaded and then loaded to failure. The stiffness for the LRHP group was significantly higher than that for the other two groups, and that for the HCS group was significantly higher than that for the DCS group. The LRHP group had the greatest strength, followed by the HCS group and then the DCS group. The HCS construct demonstrated greater fixation strength than that of the commonly used cortical screws, although the plate group was the most stable. The present study revealed the feasibility of using a single oblique HCS, which has the advantages of being buried, requiring limited wound exposure, and having relatively easy operation, for treating simple radial head fractures.

OBJECTIVE: The purpose of this study was to introduce the surgical method of K-wire combined with screw in the treatment of Arbeitsgemeinschaftfür Osteosynthesefragen (AO) type B3.1 phalangeal fractures and to compare its clinical, radiological and functional outcomes with K-wire fixation.
METHODS: This was a retrospective comparative study. From January 2015 to February 2022, we treated 86 patients with AO type B3.1 phalangeal fractures. A total of 71 patients were finally included in the statistical analysis. Thirty-nine patients received K-wires combined with screw, and 32 patients received simple K-wires. The follow-up time was at least 6 months. Outcome measures included general information, operative time, total active motion (TAM), pinch strength, radiological union time, pain assessed by visual analog scale (VAS), Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) score, cost, and complications.
RESULTS: The follow-up time was 6-12 months, with an average of 7.9 months. All patients achieved clinical and radiological union. Compared with the K-wire fixation group, the TAM, radiological union time and VAS score of the K-wire combined with screw group had obvious advantages. Compared with the opposite healthy hand, the grip strength of the two groups was similar, and there was no significant difference in the QuickDASH score. The incidence rate of complications in the K-wire combined with screw group (2/39) was lower than that in the K-wire fixation group (7/32).
CONCLUSIONS: Compared with simple K-wire fixation, K-wire combined with screw in the treatment of AO type B3.1 phalangeal fractures is a safer and reliable surgical method. K-wire controls the rotation and plays a role similar to a \"lock\". The screw can exert pressure and fix it more firmly. It shortens the time of fracture healing and has a higher TAM and fewer postoperative complications.

Background: The effects of cannulated screws made of polyetheretherketone (PEEK) on the biomechanical properties of the vertebral body during vertebra-pediculoplasty remain unclear. This study aimed to investigate whether PEEK screws have the potential to replace titanium alloy screws. Methods: The surgical model of two different materials of screws was constructed using the finite element method. The biomechanical effects of the two models on the vertebral body under different working conditions were compared. Results: ① The peak von Mises stress of PEEK screws was significantly lower than that of titanium screws, with a reduction ranging from 52% to 80%. ② The von Mises stress values for the injured T12 spine were similar for both materials. Additionally, the segmental range of motion and intervertebral disc pressure showed no significant difference between the two materials. Conclusion: PEEK screws demonstrated advantages over titanium screws and may serve as a viable alternative for screw materials in vertebra-pediculoplasty.

BACKGROUND: Previous studies mainly reported perpendicular and medial inclination insertion methods for C1 transpedicular screw insertion (TSI). Our recent study showed the ideal C1 transpedicular screw trajectory (TST) can be achieved by medial inclination, perpendicular or even lateral inclination insertion, and Axis C can be a reliable trajectory. The purpose of this study is to confirm Axis C is an ideal C1 TST by comparing the cortical perforation differences between actual C1 TSI and virtual C1 transpedicular screw insertion along Axis C (Virtual C1 Axis C TSI).
METHODS: Firstly, the cortical perforations of the transverse foramen and vertebral canal caused by C1 TSIs in twelve randomly selected patients were evaluated based on their postoperative CT data. Secondly, Virtual C1 Axis C TSIs were performed based on same patients\' preoperative CT data. Thirdly, the cortical perforation differences between actual and virtual screws were compared.
RESULTS: In actual C1 TSI group, there were thirteen locations of cortical perforation in the axial plane, with five sides in transverse foramen and eight sides in vertebral canal, the cortical perforation rate was 54.2%; the degree of perforation was mild in twelve locations and medium in one location. In contrast, there was no cortical perforation in Virtual C1 Axis C TSI group.
CONCLUSIONS: Axis C is an ideal trajectory for C1 TSI, it can be utilized as a navigation route for computer assisted surgery system.

Pedicle screw fixation provides one of the most stable spinal constructs. Their designs together with osseous characteristics have been known to influence the screw-bone interplay during surgical maneuvers and thereafter the fusion process. Various technical modifications to enhance screw performance have been suggested. This study evaluated the pull-out strength and axial stiffness of a novel pedicle screw design with variable thread geometry and pitch.
The newly designed triple threaded pedicle screw is tapered, and has unique out-turned flanges to hold the cancellous bone and a finer pitch at its distal and proximal end to engage the cortical bone. Five lumbar and 4 lower thoracic cadaveric vertebrae were divided into hemivertebrae. A standard cancellous pedicle screw and the newly designed pedicle screw were inserted into each hemivertebra. Axial stiffness and peak pull-out force between the screw types were compared; a finite element analysis was also performed to additionally compare the pull out under toggle forces.
In cadaveric study, the axial stiffness of the new screw was significantly better than that of the standard screw. However, the peak load between the screws was not statistically different. Finite element analyses suggested lesser stress at bone-implant interface for the new screw along with better axial stiffness under both co-axial and toggle forces.
Our novel pedicle screw design with variable thread geometry demonstrates greater axial stiffness compared with the standard screws, and therefore is likely to withstand a greater surgical manipulation.

UNASSIGNED: The conventional lateral approach is widely used to treat radial head fractures with screws. However, the traditional incision may have shortcomings, including excessive exposure and significant scarring. We propose an innovative method - a mini-open lateral approach of less than 2.5 cm for surgical treatment of radial head fractures with screws.
UNASSIGNED: From Jan 2017 to Dec 2020, 34 patients diagnosed with closed radial head fracture were treated with open reduction and internal fixation (ORIF) in this study. The novel group (mini-open group) included 15 patients, and the other 19 patients were in the traditional group. The time of operation and the blood loss during operation were recorded. Postoperative clinical outcomes and radiographic results were recorded and compared between the two groups. The range of motion (ROM) in the elbow, the Visual Analogue Scale (VAS), the Mayo Elbow Performance Score (MEPS), Rating Scale of the American Shoulder and Elbow Surgeons (ASES), and the Shortened Disabilities of the Arm, Shoulder and Hand Questionnaire (Q-DASH) score and complications, such as wound infection, vascular and nerve damage, and fragment redisplacement were observed in the two groups.
UNASSIGNED: In the comparison between the two groups, there was no significant difference in age, sex, cause of radial head fracture, or other basic information. The operation time, intraoperative blood loss, and VAS score at 3 days postoperation were significantly reduced in the novel group (p < 0.05). The follow-up results showed that there was no significant difference in MEPS, ASES, or Q-DASH scores between the two groups.
UNASSIGNED: The mini-open approach reduced intraoperative blood loss, shortened operation time, relieved patient pain, and achieved a satisfactory postoperative clinical result, which demonstrates that the novel approach is a safe and effective option for treating radial head fractures.

OBJECTIVE: Osteoporosis-related proximal femur fractures continue to increase significantly due to demographic change. This study was designed to evaluate the biomechanical stability of two different fixation methods (cerclage vs. screw) for refixation of a trochanter minor fragment in the pertrochanteric fractures in cadaveric bones.
METHODS: Artificial bones (n = 14) and human bones (n = 16) were treated with a DHS and the trochanter minor fragment was reduced by cerclage wiring or direct screw fixation. After preloading the simulated iliopsoas with 10 N, a tensile test was performed, ending with either a 70% loss of strength or avulsion of the fragment. The mean values of the avulsion force and the surface strain were recorded.
RESULTS: All tensile tests showed no significant differences between refixation using a direct screw or wire cerclage, for both artificial bones and human specimens. Absolute values showed higher avulsion forces after direct screw fixation than refixation with a wire cerclage. The surface tension of specimens treated with direct screw fixation was lower than that of specimens treated with wire cerclage. An opposite effect was seen in artificial bones. Both effects were not statistically significant.
CONCLUSIONS: Based on the equal stability after lag screw placement compared to cerclage wiring, we promote the placement of a lag screw into the lesser trochanter fragment in pertrochanteric femur fractures when using a dynamic hip screw.
METHODS: Level III.

BACKGROUND: Bridging bone defects in revision total hip arthroplasty is a challenge to orthopedic surgeons. The eccentric revision cup is a progression of jumbo cup. Our aim is to confirm the optimal screw-hole positions of the eccentric revision cup by morphological measurements of three-dimensional pelvic reconstruction.
METHODS: Eighty CT images were converted to virtual three-dimensional bones. After simulating the surgery procedure, all available screw holes were inserted with the screws in virtual. By measuring the length of the screw in the pelvic bone, we determined the rich bone stock area. Then the screw holes were designed according to the characteristics of bone stock distribution. The peripheral screw-hole cluster and inner screw-hole cluster were studied respectively.
RESULTS: For peripheral screw-hole cluster, five screw holes were evenly distributed between point A and point B in the thicker rim. For inner screw-hole cluster, screw hole 1 and screw hole 2 are the recommended inner screw holes.
CONCLUSIONS: The eccentric revision cup has inherited the strengths of jumbo cup besides several unique advantages, including using the peripheral screws enhancing primary stability; decreasing the shift of hip rotation center and restoring biomechanical function; reducing the risk of dislocation because of the smaller head-cup differences; increasing the contact area between the outer cup and the host bone while maintaining a normal inclination of the inner cup. In this study, we confirmed the optimal screw-hole positions of the eccentric revision cup by surgical simulation and morphological measurement. However, biomechanical tests are still being further explored.