Screw Holes Research Articles

Research on Multistage Rotor Assembly Optimization Methods for Aeroengine Based on the Genetic Algorithm

The coaxiality and unbalance are the two important indexes to evaluate the assembly quality of an aeroengine. It often needs to be tested and disassembled repeatedly to meet the double-objective requirements at the same time. Therefore, an intelligent assembly method is urgently needed to directly predict the optimal assembly orientations of the rotors at each stage to meet the double-objective requirements simultaneously. In this study, an assembly optimization method for the multistage rotor of an aeroengine is proposed based on the genetic algorithm. Firstly, a spatial location propagation model is developed to accurately predict the spatial position of each rotor after assembly. The alignment process of the assembly screw holes of the adjacent rotors is considered for the first time. Secondly, a new assembly optimization strategy is proposed to select different assembly data for the specific values of the coaxiality and unbalance, respectively. Finally, a double-objective fitness function is constructed based on the coaxiality and unbalance. The simulation and experimental results show that the assembly optimization method proposed in this study can be utilized to achieve synchronous optimization of the coaxiality and unbalance of an aeroengine during preassembly.

Removal of cement-augmented screws in distal femoral fractures and the effect of retained screws and cement on total knee arthroplasty: a biomechanical investigation

BackgroundGiven the increasing number of osteoporotic fractures of the distal femur, screw augmentation with bone cement is an option to enhance implant anchorage. However, in implant removal or revision surgeries, the cement cannot be removed from the distal femur without an extended surgical procedure. Therefore, the aims of this study were to investigate (1) whether cement augmentation has any influence on screw removal and removal torque, and (2) whether the implantation of a femoral component of a knee arthroplasty and its initial interface stability are affected by the remaining screws/cement.Material and methodsEight pairs of fresh-frozen human female cadaveric distal femurs (mean age, 86 years) with a simulated AO/OTA 33 A3 fracture were randomized in paired fashion to two groups and fixed with a distal femoral locking plate using cannulated perforated locking screws. Screw augmentation with bone cement was performed in one of the groups, while the other group received no screw augmentation. Following biomechanical testing until failure (results published separately), the screws were removed and the removal torque was measured. A femoral component of a knee arthroplasty was then implanted, and pull-out tests were performed after cement curing. Interference from broken screws/cement was assessed, and the maximum pull-out force was measured.ResultsThe mean screw removal torque was not significantly different between the augmented (4.9 Nm, SD 0.9) and nonaugmented (4.6 Nm, SD 1.3, p = 0.65) screw groups. However, there were significantly more broken screws in in the augmented screw group (17 versus 9; p < 0.001). There was no significant difference in the pull-out force of the femoral component between the augmented (2625 N, SD 603) and nonaugmented (2653 N, SD 542, p = 0.94) screw groups.ConclusionThe screw removal torque during implant removal surgery does not significantly differ between augmented and nonaugmented screws. In the augmented screw group, significantly more screws failed. To overcome this, the use of solid screws in holes B, C, and G can be considered. Additionally, it is possible to implant a femoral component for knee arthroplasty that retains the initial anchorage and does not suffer from interference with broken screws and/or residual cement.Level of Evidence 5

Local bone quality measure and construct failure prediction: a biomechanical study on distal femur fractures

IntroductionThe aim of this investigation was to better understand the differences in local bone quality at the distal femur and their correlation with biomechanical construct failure, with the intention to identify regions of importance to optimize implant anchorage.Materials and methodsSeven fresh–frozen female femurs underwent high-resolution peripheral quantitative computed tomography (HR-pQCT) to determine bone mineral density (BMD) within three different regions of interest (distal, intermedium, and proximal) at the distal femur. In addition, local bone quality was assessed by measuring the peak torque necessary to break out the trabecular bone along each separate hole of a locking compression plate (LCP) during its instrumentation. Finally, biomechanical testing was performed using cyclic axial loading until failure in an AO/OTA 33 A3 fracture model.ResultsLocal BMD was highest in the distal region. This was confirmed by the measurement of local bone quality using DensiProbe™. The most distal holes represented locations with the highest breakaway torque resistance, with the holes on the posterior side of the plate indicating higher values than those on its anterior side. We demonstrated strong correlation between the cycles to failure and local bone strength (measured with DensiProbe™) in the most distal posterior screw hole, having the highest peak torque.ConclusionThe local bone quality at the distal femur indicates that in plated distal femur fractures the distal posterior screw holes seem to be the key ones and should be occupied. Measurement of the local bone strength with DensiProbe™ is one possibility to determine the risk of construct failure, therefore, thresholds need to be defined.

Monocortical fixation for locking plate distal screws does not impair mechanical properties in open-wedge high tibial osteotomy

BackgroundThe neurovascular bundle containing the deep peroneal nerve has a potential risk of injury during open-wedge high tibial osteotomy (OWHTO), particularly due to drilling for bicortical fixation at distal screw holes. Therefore, monocortical fixation is recommended for distal fixation of a long locking plate as long as good stability is ensured. The purpose of this study was to analyse the biomechanical properties of monocortical fixation of distal locking screws for OWHTO.MethodsThree-dimensional models of bone and fixation materials simulating OWHTO were created using computed tomographic data of patients and material data of a T-shaped long locking plate and screws. Three of the four distal screws of the locking plate were chosen for a bicortical fixation or monocortical fixation procedure. In addition, loss of correction was assessed by measuring the medial proximal tibial angle (MPTA) in patients who underwent OWHTO with two bicortical and two monocortical distal fixation screws at 1 month and 1 year after surgery.ResultsNo significant differences in stress were observed in either the normal or osteoporotic bone model between the monocortical and bicortical fixation models, including in the area of the lateral hinge at the osteotomy site.Furthermore, there were no significant differences in MPTA between the early post-operative period and 1-year follow-up.ConclusionsThe monocortical fixation method for three distal screws of the locking plate did not worsen the mechanical properties of fixation for OWHTO using a long locking plate with four proximal and four distal screws. In actual surgery, the number of distal bicortical screws should be reduced based on the patient’s condition, taking into account the risk of lateral hinge fracture and unexpected surgical complications. Using at least two bicortical screws would be practical considering the various factors related to reduced fixing ability.

Augmented Reality Navigated Sacral-Alar-Iliac Screw Insertion

Sacral-alar-iliac (SAI) screws are increasingly used for lumbo-pelvic fixation procedures. Insertion of SAI screws is technically challenging, and surgeons often rely on costly and time-consuming navigation systems. We investigated the accuracy and precision of an augmented reality (AR)-based and commercially available head-mounted device requiring minimal infrastructure. A pelvic sawbone model served to drill pilot holes of 80 SAI screw trajectories by 2 surgeons, randomly either freehand (FH) without any kind of navigation or with AR navigation. The number of primary pilot hole perforations, simulated screw perforation, minimal axis/outer cortical wall distance, true sagittal cranio-caudal inclination angle (tSCCIA), true axial medio-lateral angle, and maximal screw length (MSL) were measured and compared to predefined optimal values. In total, 1/40 (2.5%) of AR-navigated screw hole trajectories showed a perforation before passing the inferior gluteal line compared to 24/40 (60%) of FH screw hole trajectories (P < .05). The differences between FH- and AR-guided holes compared to optimal values were significant for tSCCIA with -10.8° ± 11.77° and MSL -65.29 ± 15 mm vs 55.04 ± 6.76 mm (P = .001). In this study, the additional anatomical information provided by the AR headset and the superimposed operative plan improved the precision of drilling pilot holes for SAI screws in a laboratory setting compared to the conventional FH technique. Further technical development and validation studies are currently being performed to investigate potential clinical benefits of the AR-based navigation approach described here. 4.

Visualization of Fluoroscopic Imaging in Orthopedic Surgery: Head-Mounted Display vs Conventional Monitor.

Purpose. See-through head-mounted displays (HMDs) can be used to view fluoroscopic imaging during orthopedic surgical procedures. The goals of this study were to determine whether HMDs reduce procedure time, number of fluoroscopic images required, or number of head turns by the surgeon compared with standard monitors. Methods. Sixteen orthopedic surgery residents each performed fluoroscopy-guided drilling of 8 holes for placement of tibial nail distal interlocking screws in an anatomical model, with 4 holes drilled while using HMD and 4 holes drilled while using a standard monitor. Procedure time, number of fluoroscopic images needed, and number of head turns by the resident during the procedure were compared between the 2 modalities. Statistical significance was set at P < .05. Results. Mean (SD) procedure time did not differ significantly between attempts using the standard monitor (55 [37] seconds) vs the HMD (56 [31] seconds) (P = .73). Neither did mean number of fluoroscopic images differ significantly between attempts using the standard monitor vs the HMD (9 [5] images for each) (P = .84). Residents turned their heads significantly more times when using the standard monitor (9 [5] times) vs the HMD (1 [2] times) (P < .001). Conclusions. Head-mounted displays lessened the need for residents to turn their heads away from the surgical field while drilling holes for tibial nail distal interlocking screws in an anatomical model; however, there was no difference in terms of procedure time or number of fluoroscopic images needed using the HMD compared with the standard monitor.

An Unbalance Optimization Method for a Multi-Stage Rotor Based on an Assembly Error Propagation Model

For the assembly of a multi-stage rotor, such as an aero-engine or gas turbine, the parts need to be assembled optimally to avoid excessive unbalance. We propose a method to optimize the unbalance of a multi-stage rotor during assembly. First, we developed an assembly error propagation model for a multi-stage rotor. The alignment process and distribution of the screw holes of the adjacent rotors was considered for the first time. Secondly, we propose a new assembly datum for unbalance optimization to ensure consistency with the actual conditions of a dynamic balance test. Finally, the unbalance optimization of a multi-stage rotor was achieved using a genetic algorithm, and the corresponding optimal assembly orientations of rotors at different stages were also identified. The results of the simulations showed that the assembly error propagation model had high accuracy and that the genetic optimization process had good convergence. The effect of unbalance optimization was also proven with experiments.

What’s New in Hand and Wrist Surgery

What’s New in Hand and Wrist Surgery

Fatigue implications for bending orthopaedic plates

Objectives- We aimed to investigate how pre-bending affects the mechanical properties, specifically fatigue, of stainless-steel plates. Methods- 3.5mm LCP 10-hole plates were pre-bent in 1, 2 and 3 locations to the same overall degree and fatigue testing performed. Finite Element Analysis (FEA) was performed in Strand7 (version 2.4.6) to better understand the failure point of the plates in four-point bending. Results- Six different plate pre-bending conditions were tested for resistance to fatigue failure. Increasing the number of pre-bends improved the fatigue resistance with two pre-bends having a mean 509,304 cycles to failure and three pre-bends 491,378 cycles to failure. The region of highest stress and the point of fatigue failure were at the plate's minimum cross-sectional area, which was predicted by the FEA and confirmed with mechanical testing. For plates pre-bent in two locations, the fatigue failure always occurred in the screw hole not in between the positions of the two pre-bends. Non-linear FEA simulation confirmed that work hardening occurs around pre-bend locations, conferring increased fatigue resistance to the holes next to, or between, pre-bend locations. ConclusionsWe found that contrary to orthopaedic folklore, pre-bending of plates is not detrimental to fatigue resistance of the stainless-steel plates we tested. Pre-bending plates in a single plane increased the fatigue properties of the 10-hole stainless-steel plate tested.

The Effect on the Fracture Healing following Femoral Neck Shortening after Osteoporotic Femoral Neck Fracture Treated with Internal Fixation: Finite Element Analysis.

Objective To evaluate the stress status of fracture site caused by femoral neck shortening and to analyze the stress of fracture site and the implants from the finite element point of view. Methods CT scan data of hip of a normal adult female were collected. Three-dimensional reconstruction MICs and related module function simulation was used to establish the postoperative shortening model of femoral neck fracture with Pauwels angle > 50°, which was treated with cannulated screws. The models were divided into four groups: normal femoral neck, shortening in 2.5 mm, shortening in 7.5 mm, and shortening in 12.5 mm. The finite element analysis software msc.nastran2012 was used, and the data of maximum stress and stress nephogram of fracture site and implants were carried out. Results From normal femoral neck to shortening in 12.5 mm of the femoral neck, the maximum tensile stress increased gradually in the fracture site above the cannulated screws while compressive stress decreased gradually in the fracture site below the cannulated screws, and the maximum stress of the cannulated screws increased gradually with obvious stress concentration at the screw holes in the fracture site, and the peak value of stress concentration was about 179 MPa. Conclusion The biomechanical environment of the fracture site changed by femoral neck shortening. With the increasing of femoral neck shortening, the stress of the fracture site and implants would be uneven; then, the stability of fracture site would become worse, and the possibility of implant sliding or even breakage would be increased.

Biomechanical Evaluation of Extramedullary Versus Intramedullary Reduction in Unstable Femoral Trochanteric Fractures.

Introduction:The failure rate of operations involving the cephalomedullary nail technique for unstable femoral trochanteric fractures is 3-12%. Changing the reduction strategy may improve the stability. This study aimed to confirm whether reducing the proximal fragment with the medial calcar contact, as opposed to utilizing an intramedullary reduction, would improve the stability of such fractures.Materials and Methods:The unstable femoral trochanteric fracture model was created with fixation by cephalomedullary nails in 22 imitation bones. The 2 reduction patterns were as follows: one was with the proximal head-neck fragment external to the distal bone in the frontal plane and anterior in the sagittal plane as “Extramedullary,” while the other was the opposite reduction position, that is, bone in the frontal plane and sagittal plane as “Intramedullary.” We evaluated the tip-apex distance, compression stiffness, change in femoral neck-shaft angle, amount of blade telescoping, and diameter of the distal screw hole after the compression test. Statistical analysis was conducted using the Mann-Whitney U test.Results:No significant differences were seen in compression stiffness (p = 0.804) and femoral neck-shaft angle change (p = 0.644). Although the “Extramedullary” tip-apex distance was larger than the “Intramedullary” distance (p = 0.001), it indicated clinically acceptable lengths. The amount of blade telescoping and the distal screw hole diameter were significantly larger in “Intramedullary” than in “Extramedullary” (p < 0.001, p = 0.019, respectively). Our results showed that “Intramedullary” had significantly larger blade telescoping and distal screw hole diameters than “Extramedullary,” and contrary to our hypothesis, no significant differences were seen in compression stiffness and femoral neck-shaft angle change.Conclusions:As opposed to the “Intramedullary” reduction pattern, the biomechanical properties of the “Extramedullary” reduction pattern improved stability during testing and decreased sliding.

Effect of fluid contamination on reverse torque values in implant-abutment connections under oral conditions.

PURPOSEImplant mechanical complications, including screw loosening, can influence dental implant success. It has been shown that torque values are affected by contamination occurred in implant-abutment (I/A) interface. This study aimed to examine the effects of blood, saliva, fluoride and chlorhexidine contamination on reverse torque values (RTVs) of abutment screws in oral conditions.MATERIALS AND METHODS50 fixtures were mounted into the stainless-steel holders and divided into five groups (n = 10). Except control group (NC), fixture screw holes in other groups were contaminated with chlorhexidine (CG), saliva (SG), blood (BG), or fluoride (FG). Abutment screws were tightened with a digital torque meter. I/A assemblies were subjected to thermocycling and cyclic loading. The mean RTVs were recorded and data were analyzed with one-way ANOVA and Tukey test.RESULTSExcept for specimens in SG (20.56 ± 1.33), other specimens in BG (21.11 ± 1.54), CG (22.89 ± 1.1) and FG (24.00 ± 1.12) displayed significantly higher RTVs compared to NC (19.00 ± 1.87). The highest RTVs were detected in CG and FG.CONCLUSIONThe obtained data robustly suggest that RTVs were significantly affected by fluid contaminations. Specimens in FG and CG displayed the highest RTVs. Therefore, clinicians should have enough knowledge about probable contaminations in I/A interface in order to manage them during clinical procedure and to inform patients about using oral care products.

Biomechanical Comparison of Polymethylmethacrylate Augmentation Methods in Failed Pedicle Screw Revision.

To compare biomechanical results between different polymethylmethacrylate (PMMA) augmentation methods on failed lumbar pedicle screw models of animal vertebrae. Thirty lumbar vertebrae were harvested from six calves, and their bone mineral density was measured. 60 Polyaxial pedicle screws were inserted to all vertebrae. Pull-out tests were performed to all specimens on an Instron machine. The specimens were randomly divided into four groups. The same screws used in primary screwing process were labeled and used in revision. Screws in the first group were augmented by injecting PMMA into the failed screw hole with a syringe; screws in the second group by inserting bone graft and roll-shaped PMMA, screws in the third group by inserting bone graft and injecting PMMA with a syringe; and the fourth group by inserting bone graft and injecting PMMA through a fenestrated pedicle screw. The pull-out strength (POS) results of all specimens were recorded and compared with statistical analyses. The mean BMD of the vertebrae was 1.31 ± 0.225 g/cm < sup > 2 < /sup > and no significant difference was found between the groups (p > 0.05). The mean POS of the primary screws in the first, second, third, and fourth groups were 2166,5 N/m < sup > 2 < /sup > , 2183,5 N/m2, 2508,5 N/m < sup > 2 < /sup > , and 2005c N/m < sup > 2 < /sup > respectively. After the augmentation, the mean POS in the first, second, third and fourth groups were 3839 N/m < sup > 2 < /sup > , 2874 N/m < sup > 2 < /sup > , 2929 N/m < sup > 2 < /sup > and 3826 N/m < sup > 2 < /sup > respectively. No statistical difference was found between the groups in post-revision POS values (p > 0.05). There was no significant statistical difference found in POS between the augmentation methods.

Retention force and stress distribution analysis of the cementless double crown–type implant-supported prosthesis

Statement of problemImplant-supported fixed dental prostheses have been classified into screw-retained and cement-retained types, and each retaining type has complications. A novel retentive cementless double crown (CLD) type of the implant-supported fixed prosthesis has been developed. CLD has air pockets in the intaglio surface of the crown and does not require cement or a screw hole. However, studies on the retention force and stress distribution of the system are lacking. PurposeThe purpose of this in vitro study was to evaluate the retention force and stress distribution in the CLD system. Material and methodsThe specimen comprised an implant, a titanium abutment, and a zirconia crown. Retention forces of 10 specimens of the CLD type were measured at no loading and after cyclic loading for 50, 100, 200, 600, 10 000, and 1 000 000 cycles by using a universal testing machine with a custom attachment device. Forty specimens of the stress distribution test were divided into 4 groups based on the retention type (cement-retained or CLD type) and load direction (vertical or oblique). Strain gauges were attached onto the buccal and lingual sides of the implant, and microstrain values were measured. One-way analysis of variance with the post hoc Tukey honestly significant difference test was performed on the retention force data, and the t test was performed to analyze the microstrain value data (α=.05). ResultsRetention forces after 0, 50, 100, 200, 600, 10 000, and 1 000 000 load cycles were 18.12 ±6.16 N, 20.47 ±5.78 N, 19.79 ±6.61 N, 18.46 ±5.23 N, 19.60 ±6.93 N, 21.75 ±5.03 N, and 40.91 ±9.32 N, respectively, and after 1 000 000 cycles, the retention force was significantly higher than that of other load cycles (P<.05). The mean of maximum microstrain values under the vertical load were similar in the cement-retained type (buccal side, 834.96 ±53.69 μm/m; lingual side, 490.76 ±34.12 μm/m) and the CLD type (buccal side, 814.28 ±71.20 μm/m; lingual side, 479.10 ±30.74) (P>.05), and the mean of maximum microstrain values under the oblique load was also similar in the cement-retained type (buccal side, 1991.04 ±109.89 μm/m; lingual side, -2232.41 ±189.88) and the CLD type (buccal side, 1932.47 ±152.51 μm/m; lingual side, -2097.47 ±130.69 μm/m) (P>.05). ConclusionsThe CLD type had clinically acceptable retention during 1 000 000 load cycles and had a similar or better stress distribution capability than the cement-retained type.

Treatment of patellar fractures using bioresorbable forged composites of raw particulate unsintered hydroxyapatite/poly-L-lactide cannulated screws and nonabsorbable sutures

Forged composites of raw particulate unsintered hydroxyapatite/poly-L-lactide (F-u-HA/PLLA) implants are widely used in surgeries because they possess high mechanical strength, bioactivity, and radio-opacity. We previously reported that F-u-HA/PLLA implants were useful for treating lateral tibial condylar, lateral humeral condylar, and ankle fractures. The study aim was to investigate the efficacy of F-u-HA/PLLA cannulated screws and FiberLoop® for treating transverse patellar fractures. From April 2013 to February 2019, 15 patients with transverse patellar fractures were treated with F-u-HA/PLLA cannulated screws and FiberLoop® as follows: Open reduction and internal fixation (ORIF) were performed with two F-u-HA/PLLA cannulated screws and a temporary fixation Kirshner wire (K-wire). Three No. 2 FiberLoops® were inserted into these two screw holes and the K-wire hole for temporary fixation. All patients were allowed to full weight-bearing gaits using a knee brace. Knee range of motion exercise was initiated on postoperative day 1. Knee flexion was restricted to ≤90° for 1 month postoperatively. Radiograph was performed to evaluate fracture healing, screw breakage, reduction loss, and screw radio-opacity. Clinical outcomes and postoperative complications were assessed. The average follow-up was 16.0 months. All fractures were successfully united. Screw breakage, reduction loss, osteolysis, and radiolucent zones around the screws were not observed at the final radiographic follow-up. All F-u-HA/PLLA screw shadows were observed during the follow-up. The average range of flexion and extension were 132.0° and -2.7°, respectively. No patients experienced deep infection episodes, late aseptic tissue reactions, or foreign body reactions postoperatively. No patients complained of pain at the final follow-up. All patients returned to their pre-injury work level and activities of daily living. Our results strongly suggest that ORIF with F-u-HA/PLLA screws and FiberLoop® could be an alternative treatment option for transverse patellar fractures.

Development and Testing of a Novel Locking Pin Cap to Create a Fixed-Angle K-Wire Plate Construct

To test the effectiveness of a novel locking pin cap to attach a K-wire rigidly to a volar locking plate and resist fracture displacement compared with commercially available alternatives. Two different methods of fracture fixation were tested on a total of 12 Sawbones models with volar shear distal radius fracture (6/group). The fragments were fixed with either 2 commercially available pin plates (industry standard) or a volar plate with 2 locking screws fixing the scaphoid facet and 2 pins locked to the plate with a novel locking pin cap in the lunate facet. Axial load conditioning was performed followed by sinusoidal loading to 250 N at 50 mm/s. A motion capture system was used to assess the relative movement of the fracture fragments relative to the intact shaft. The strength of the fixation construct was quantified by (1) the force required to achieve a 2-mm gap between the shaft and fracture fragments and (2) ultimate load to failure. One industry standard pin plate demonstrated disassociation of the pin from the plate after fatigue conditioning. This did not occur in the locking pin cap group. The locking pin cap construct group was able to sustain a significantly higher load compared with the industry standard when the construct was displaced to the 2-mm gap. The locking pin cap also significantly increased the ultimate load to failure compared with the industry standard. The novel locking pin cap creates a fixed-angle attachment of a K-wire to an existing locking screw hole in a plate. This fixed-angle K-wire is significantly stronger in preventing gap formation and resisting ultimate failure than commercially available plates that use bent K-wires. The development of novel techniques to secure small articular fragments may ultimately improve clinical outcomes.

Role of aspanning plate as an internal fixator in complex distal radius fractures.

Minimally invasive temporary internal wrist arthrodesis as an alternative treatment method in complex distal radius fractures. Complex distal radius fractures with dorsal and/or palmar comminution and little to no reconstruction possibilities, radiocarpal ligamentous injury, need for early weight bearing through the affected wrist (walking aids). Complex hand injuries limiting the possibility to safely secure the plate at either the metacarpal or the radial shaft. Percutaneous or open reduction and fixation of the distal radius fracture. Determine the location for the two stab incisions under fluoroscopy; one over the distal radial diaphysis and one over the second or third metacarpal. Athird incision over Lister's tubercle allows transposition of the extensor pollicis longus (EPL) tendon, excision of the posterior interosseous nerve and dorsal arthrotomy. Retrograde insertion of the spanning plate. Placement of afirst nonlocking screw through the glide hole into the metacarpal shaft. Under traction, aproximal screw hole is filled with anonlocking screw into the radial diaphysis. Tightening of the cortical screws under lateral fluoroscopic view. The remaining screw holes at both the distal and proximal ends of the plate are filled with locking screws. Layered wound closure. A removable wrist splint is worn during 2weeks. Weight bearing through the injured wrist is immediately allowed. Removal of the spanning plate is scheduled at 3months after radiographic evidence of fracture consolidation. In total, twelve distal radius fractures were treated by dorsal spanning plate fixation between January 2018 and January 2019. Average age was 53.3 ± 24.5years (range 22-95years). Both 3.5 mm and 2.4/2.7 mm plates were used. All twelve fractures were healed after 3months. The mean Disabilities of Arm, Shoulder and Hand (DASH) score was 36.4 (range 8.3-70.0). There was one EPL tendon rupture, one case with extensor tendon adhesions, one periosteosynthetic fracture of the radial shaft and one complex regional pain syndrome. There was no implant failure and no infection.

Risk factors for implant-related fractures after proximal femoral osteotomy in children with developmental dysplasia of the hip: a case-control study

Background and purpose — Proximal femoral osteotomy (PFO) is commonly performed to treat children with developmental dysplasia of the hip (DDH). Implant-related femoral fractures after osteotomy are sometimes reported, but the potential risk factors for these fractures remain unclear. We investigated the association of implant-related fractures with PFO and potential risk factors for these fractures. Patients and methods — We retrospectively reviewed 1,385 children undergoing PFO for DDH in our institution from 2009 to 2016 after obtaining institutional review board (IRB) approval and identified 27 children (28 hips, fracture group) with implant-related femoral fractures after PFO. We selected 137 children (218 hips, control group) without fractures who matched the children in the fracture group by age, weight, surgeon, and surgical period. Relevant clinical data were collected and compared between the 2 groups. Multiple analyses of risk factors for implant-related fractures were conducted by logistic regression with the stepwise regression method. Results — The occurrence rate of implant-related fractures was 1.9% (27/1,385). Compared with the control group, the fracture group more commonly exhibited bilateral involvement (74% vs. 53%, p = 0.04), used a spica orthosis for immobilization after osteotomy (43% vs 21%, p = 0.01) and exhibited mild remodeling at the osteotomy site (46% vs. 19%, p = 0.003), and less commonly required capsulotomy during osteotomy (61% vs. 79%, p = 0.03). According to the multiple regression analysis, the only factor identified as an independent risk factor for implant-related fractures was mild remodeling at the osteotomy site (OR = 3.2, 95% CI 1.4–7.5). Remodeling at the osteotomy site was significantly associated with varus osteotomy (coefficient = 1.4, CI 1.03–1.8). The fracture occurred at a mean of 12 months (2.2–25) after osteotomy or 3.3 months (0–12) after implant removal. In children undergoing implant removal, the fractures mostly occurred at the osteotomy site (n = 13/15), while in those with the implant remaining, the fractures mostly occurred in the screw hole (n = 8/13). Interpretation — The type of PFO performed is not associated with implant-related fractures in children with DDH. Children with mild remodeling at the osteotomy site should be closely followed up, regardless of whether the hardware is removed, and high-intensity activity should not be permitted until moderate or extensive remodeling is confirmed. After PFO, the implants should be removed when solid union is achieved at the osteotomy site.

Tests of the resistance to pull-out fasteners from top sandwich panel

This paper presents the results of tests of the resistance of fasteners to pull-out from the top face skin of a roofing sandwich panel. The full-scale tests were carried out in the Wroclaw University of Science and Technology Civil Engineering Faculty Laboratory. During the tests the pulling out force and the displacements of the substrate near the screw hole were recorded. On the basis of the test results the current knowledge on determining the strength limit of such connections was verified. Moreover, a theoretical discussion of the investigated problem was carried out. The paper ends with conclusions which can serve as advice for designers and contractors using the discussed fastening solution.

FRACTURE RESISTANCE OF CEMENTED AND INTEGRATED CERAMIC CROWNS SUPPORTED ON ZIRCONIA IMPLANT ABUTMENTS (IN VITRO STUDY)

Introduction: Even-though the demand for esthetics amplified the popularity of all-ceramic restorations, failures are reported at the interface between zirconia core and ceramic-veneer. Objectives: Comparing fracture resistance and mode of failure of cemented and integrated ceramic crowns supported on zirconia implant abutments. Materials and Methods: Cast having missing upper first premolar; was chosen. Silicone mold was made to duplicate fifteen polyurethane models. Clear surgical guide was fabricated for precise insertion of implant analogue. Models were divided into three groups (n=5). Group I (cemented crowns) Group II(integrated crowns with composite plug) Group III(integrated crowns with ceramic plug). Group I: Optical impression of zironia abutment was made then crowns were designed, milled, crystallized, and glazed. Then crowns were cemented using resin cement. Group II and III crowns were constructed using same technique as Group I but with 2 mm occlusal hole. CAD-on was used to join crowns onto abutments. Group II screw-holes were closed using composite resin, while Group III screw holes were scanned, designed, milled using Emax-CAD, then cemented using resin cement. Specimens were subjected to cyclic loading machine for 120,000 cycles, then attached to universal testing machine by cross-head speed (0.5mm/min). Specimens were examined using stereomicroscope and scanning electron microscope. Results: Highest mean fracture load value was GroupI (901.4±54.90)N followed by Group II (790.7±187.4)N then Group III (621.5±97.42)N. Only Group I and III showed significant difference.(P2*=0.011) Conclusions: Cemented crowns showed significant superior fracture resistance than integrated crowns with ceramic plug, and no significant difference with integrated crowns with composite plug.