Double Screws Research Articles

Simplifying the Orientation of S1 Iliosacral Screws for Placement in the Dysmorphic Sacrum.

Determining the proper iliosacral screw orientation in a dysmorphic S1 sacral segment using a C-arm is difficult, and pelvic computed tomography (CT) is often necessary for the preoperative planning. On the preoperative pelvic axial CT section, the intended screw trajectory can be delineated intraosseously along the axis of the oblique osseous corridor. An inherently accurate orientation would be determined by 2 factors: (1) the trajectory is in the pelvic transverse plane, and (2) it is oriented relative to the coronal plane at a patient-specific angle, which should be measured preoperatively. Based on the above reasoning, we aimed to simplify and verify the orientation. After establishing the starting point on the sacral lateral view, we tested a method of simplifying the guidewire orientation: placing the guidewire in the pelvic transverse plane and then manipulating it to be angled relative to the coronal plane at the preoperatively measured patient-specific angle. The guidewire orientation should then be reproducibly accurate on the pelvic outlet and inlet views. The feasibility and safety of our method were verified through computer-simulated virtual surgical procedures in 95 dysmorphic sacra and clinical surgical procedures in 12 patients. The primary outcome parameters were the guidewire orientation and screw placement accuracy. Using our method, the S1 guidewire orientation was reproducibly accurate on the pelvic outlet and inlet views in all of the virtual and clinical surgical procedures. Ninety-five virtual S1 screws (1 screw in each left hemipelvis) were placed intraosseously in the pelvic transverse plane. Fourteen unilateral S1 screws were placed intraosseously in the pelvic transverse plane in the 12 patients (2 patients had double screws) without iatrogenic injuries. The guidewire orientation can be simplified by placing the guidewire in the pelvic transverse plane and replicating the preoperatively measured patient-specific angle between the guidewire and the coronal plane. After establishing the starting point on the sacral lateral view, our simplified manipulation yields a reproducibly accurate orientation on the pelvic outlet and inlet views. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Double Screws technique for management of unstable transverse humeral fractures: A comparative study

Abstract Background Plate osteosynthesis is considered the gold standard treatment for unstable humeral shaft fracture. During the surgery, it is usually advisable to achieve a preliminary reduction while applying compression on the fracture site before the plate application. While this can be easily achieved in oblique and spiral fractures using the interfragmentary screws, it is almost impossible to achieve in the transverse fractures. As a result, we introduce the Double Screws (DS) technique as a reliable solution for this problem comparing it with the traditional indirect reduction by the plate itself. Materials and methods: Patients with unstable transverse humeral shaft fractures admitted at Mansoura Trauma and Emergency Hospital during the period from July 2020 to July 2021 were collected. They were divided into two groups: one for DS reduction technique and the other for the traditional indirect reduction by the plate. Results regarding operative time, intra-operative blood loss, healing, and other complications were reported. Results: the mean operative time was significantly lower in DS group being 101.3 ± 2.3 min compared to 120.4 ± 11.2 min in the traditional group (P=0.0015). Similarly, the mean blood loss was significantly lower in DS group being 320.9 ± 15.7 ml compared to 344.16 ± 15.6 ml in the traditional group (P=0.0035). Time to union was comparable being 14.8 ± 0.8weeks and 14.3 ± 1.6weeks in the DS and traditional groups respectively (P=0.46). Conclusion DS technique is considered a reliable, time efficient and less bloody method for reduction of unstable transverse fracture pattern of humeral diaphysis.

Anatomical and Biomechanical Stability of Single/Double Screw-Cancellous Bone Fixations of Regan-Morry Type III Ulnar Coronoid Fractures in Adults: CT Measurement and Finite Element Analysis.

At present, it is still uncertain whether single screw has the same stability as double screws in the treatment of ulnar coronal process basal fracture (Regan-Morry type III). So, we aimed to compare the pull-out force and anti-rotation torque of anterior single/double screw-cancellous bone fixation (aSSBF, aDSBF) in this fracture, and further study the influencing factors on anatomical and biomechanical stability of smart screw internal fixations. A total of 63 adult volunteers with no history of elbow injury underwent elbow CT scanning with associated three-dimensional reconstruction that enabled the measurements of bone density and fixed length of the proximal ulna and coronoid. The models of coronal process basal fracture, aSSBF and aDSBF, were developed and validated. Using the finite element model test, the sensitivity analysis of pull-out force and rotational torque was carried out. The pull-out force of aSSBF model was positively correlated with the density of the cancellous bone and linearly related to the fixed depth of the screw. The load pattern of pull-out force of aDSBF model was similar to that of aSSBF model. The ultimate torque of aDSBF model was higher than that of aSSBF model, but the load pattern of ultimate torque of both models was similar to each other when the fracture reset was satisfactory, and the screw nut attaches closely to coronoid process. Moreover, with enhancement of initial pre-tightening force, the increase of ultimate torque of both models was small. In addition to three pull-out stability factors of smart screw fixations, fracture surface fitting degree and nut fitting degree are the other two important anatomical and biomechanical stability factors of smart screw fixations both for rotational stability. When all pull-out stability and rotational stability factors meet reasonable conditions simultaneously, single or double screw fixation methods are stable for the treatments of ulnar coronoid basal fractures.

Clinical Analysis of Single and Double Sacroiliac Screws in the Treatment of Tile C1 Pelvic Fracture.

We investigated the difference between fixation of single and double sacroiliac screws in the treatment of Tile C1 pelvic fractures. The data of 54 patients with Tile C1 pelvic fractures who were admitted to the trauma center of the Red Society Hospital Affiliated to Xi'an Jiaotong University between August 2016 and August 2020 were retrospectively analyzed. All patients with posterior pelvic ring injuries underwent fixation with sacroiliac screws assisted by a percutaneous robotic navigation system. The operative time, amount of intraoperative blood loss, and postoperative follow-up time between the two groups (single sacroiliac and double sacroiliac screw groups) were compared. The Matta and Majeed scores at the last follow-up were compared between the groups to evaluate fracture reduction and functional recovery. Forty-nine patients were followed up for 17.2 (±4.5) months and 16.2 (±3.4) months in the single and double sacroiliac screw groups, respectively. All patients had excellent fracture reduction immediately after surgery, according to the Matta score. All fractures healed without complications. There was no statistically significant difference in preoperative general information, amount intraoperative blood loss, intraoperative anterior ring fixation method, and postoperative follow-up time between the two groups (P > 0.05). The operative time of the single sacroiliac screw group was shorter than that of the double sacroiliac screw group (P < 0.05). At the last follow-up, the Matta score of the double sacroiliac screw group was significantly better than that of the single sacroiliac screw group (P < 0.05), and there was no statistically significant difference in the Majeed functional scores (P > 0.05). For Tile C1 pelvic fractures, double sacroiliac screw fixation of posterior ring injuries can provide a more stable treatment with no statistically significant difference in functional recovery.

Double-Screw Osteosynthesis in an Unstable Scaphoid Fracture Model: A Biomechanical Comparison of Two Screw Configurations

Although there is evidence that a single headless compression screw is sufficient for fixation of most scaphoid fractures, double-screw osteosynthesis has been shown to result in higher failure strength and stiffness than a single screw. However, the biomechanical effect of different screw configurations has not been determined. A standardized unstable fracture model was produced in 28 cadaveric scaphoids. Specimens were randomly allocated to 1 of 2 fixation groups using 2 internal compression screws positioned in either the sagittal or coronal plane. A specimen-specific 3-dimensionally-printed customized screw placement and osteotomy device was developed using computer-aided design-generated models derived from computed tomography scan data of each individual scaphoid. Load to failure and stiffness of the repair constructs were evaluated using a mechanical testing system. There were no significant differences in size, weight, and density between the scaphoid specimens. The average distance between screws was significantly greater in the sagittal group than in the coronal group. There were no significant differences between the coronal and sagittal aligned double screws in load to 2 mm displacement (mean coronal 180.9 ± 109.7 N; mean sagittal 156.0 ± 85.8 N), load to failure (mean coronal 275.9 ± 150.6 N; mean sagittal 248.0 ± 109.5 N), stiffness (mean coronal 111.7 ± 67.3 N/mm; mean sagittal 101.2 ± 45.1 N/mm), and energy absorption (mean coronal 472.6 ± 261.4 mJ; mean sagittal 443.5 ± 272.7 mJ). There are no significant biomechanical differences between the sagittal or coronal aligned double headless compression screws in a scaphoid fracture model with bone loss. In cases where double-screw fixation of the scaphoid is being considered, the placement of double screws can be at the discretion of the surgeon, and can be dictated by ease of access, surgical preference, and fracture orientation.

Poly(vinylidene fluoride) with zinc oxide and carbon nanotubes applied to pressure sheath layers in oil and gas pipelines

AbstractIn this work, PVDF composites containing 0.2% (m/m) of carbon nanotubes (MWCNTs), PVDF with 5.0% (m/m) of zinc oxide (ZnO), and composites containing both particles in the same contents in the matrix were melt processed in a mini‐extruder machine with double screws, using the counter‐rotation mode. Composites were characterized by scanning electron microscopy (SEM), Fourier‐transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), dynamic‐mechanical analysis (DMA), and contact angle tests (CA). The samples presented the predominance of the α phase, with an increased degree of crystallinity as well as an increase in dimensional stability by incorporating both fillers, showing a synergistic effect between these particles, as shown on FTIR, DSC, and XRD results. SEM images showed a good dispersion of high aspect ratio particles. In general, DMA and TGA analysis showed that composites had not decreased their thermal and mechanical performance when compared to neat PVDF. Results of CA analysis showed an increase in the hydrophobicity of the sample containing MWCNTs. Permeability tests were also performed using a differential pressure system, combining high temperature and pressure, obtaining permeability measures and time lag. This work presents an alternative of composite materials, suggesting its application in the internal pressure sheath layers of oil and gas flexible pipes.

Double-screw and quadruple-button fixation for the glenoid: Latarjet versus bone block applications.

BackgroundThe Latarjet and bone block procedures can be secured with screws or cortical buttons. The purpose of this biomechanical study was to compare quadruple buttons vs. double screws for fixation of anterior glenoid bone grafts.MethodsTwelve cadaveric scapulae (6 pairs) were denuded, resected, and potted. Pairs were randomized to quadruple-button or double-screw fixation after creation of a 15% anterior glenoid defect. The specimens underwent cyclic uniaxial compressive glenoid loading between 50 and 200 N for 1000 cycles at 1 Hz. Testing was repeated for conjoint tendon loads of 0 N (simulating a bone block procedure), 10 N, and 20 N (simulating a Latarjet procedure). Peak resultant relative coracoid graft displacement was optically tracked at 3 points (superior, central, and inferior) on the edge of the coracoid.ResultsNo significant differences were found between buttons and screws for bone block applications or with 10 N of conjoint tendon loading (P ≥ .095). At 20 N of conjoint tendon loading, however, the screws were significantly more stable than the buttons (P ≤ .023). During the initial 20-N conjoint load application, all 3 points displaced significantly more with the button reconstruction than with the screws (P ≤ .01). Overall, mean displacements did not exceed 1 mm at any position on the coracoid, regardless of testing condition.ConclusionsThe quadruple-button technique is comparable to screws when the coracoid is used as a bone block or when conjoint tendon loading is minimized. However, at higher conjoint tendon loads, the screws produced a more stable coracoid graft than the buttons.

Study on the precision of the robot-assisted sacroiliac screw placement

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.

Robot-assisted double screw fixation of minimally displaced scaphoid waist fracture nonunions or delayed unions without bone graft.

We retrospectively reviewed 12 minimally displaced fractures of the scaphoid waist in 12 patients who developed delayed or nonunions with or without conservative treatment. Mean time between injury and surgery was 6 months (range 3-12). The fractures were stabilized with double screws, which were percutaneously inserted with robot assistance, and without bone grafting. All fractures united at a mean of 8 weeks (range 6-10) after surgery. The patients were followed-up at 6 months and 1 year. The patients recovered good wrist function. No major postoperative complications were reported, and the patients returned to their usual level of activity. Robot assistance gave a high degree of accuracy when placing the cannulated screws since only two attempts were needed for correct placement of the guide wires. We explain the high union incidence by patient selection, good stabilization and not disturbing the vascular supply.Level of evidence: IV.

Digital anatomical study and clinical application of screw placement for quadrilateral plate fractures in the danger zone

BackgroundDirect screw placement for quadrilateral plate fractures in the danger zone of the acetabulum is very difficult. This study was performed to simulate the surgical procedure and try to obtain effective and safe screw angles through the middle window of the ilioinguinal approach in Chinese patients.MethodsWe randomly collected the pelvic computed tomography (CT) scans of 100 adults. DICOM-formatted CT-scan images were imported into Mimics software. The three-dimensional reconstruction (3D) digital model of the semi-pelvis was established. A 3.5 mm cylinder was used to simulate the pathway of the screw from the designated insertion point. The angles of insertion and intersex differences were explored by statistical analyses.ResultsThe screws could be inserted via three angles: medial inclination, anterior inclination and posterior inclination. The mean minimum medial inclination angle (MIMIA) of insertion point A was 4.96° ± 1.11° in males and 8.66° ± 3.40° in females, and the intersex difference was significant. The mean minimum medial inclination angle (MIMIA) of insertion point B was − 5.31° ± 3.69° in males and 1.75° ± 8.95° in females, and the intersex difference was significant. There were no differences between any of the angles for males and females at insertion point O.ConclusionsPreoperative measurement and calculation by digital tools before screw placement for quadrilateral plate fractures of the acetabulum are feasible. Double cortical screws could be placed safely in the danger zone through the middle window of the ilioinguinal approach to increase the stability of the acetabulum.

Biomechanical efficacy of four different dual screws fixations in treatment of talus neck fracture: a three-dimensional finite element analysis

BackgroundCurrent there are different screws fixation methods used for fixation of the talar neck fracture. However, the best method of screws internal fixation is still controversial. Few relevant studies have focused on this issue, especially by finite element analysis. The purpose of this study was to explore the mechanical stability of dual screws internal fixation methods with different approaches and the best biomechanical environment of the fracture section, so as to provide reliable mechanical evidence for the selection of clinical internal fixation.MethodsThe computed tomography (CT) image of the healthy adult male ankle joint was used for three-dimensional reconstruction of the ankle model. Talus neck fracture and screws were constructed by computer-aided design (CAD). Then, 3D model of talar neck fracture which fixed with antero-posterior (AP) parallel dual screws, antero-posterior (AP) cross dual screws, postero-anterior (PA) parallel dual screws, and postero-anterior (PA) cross dual screws were simulated. Finally, under the condition of 2400N vertical load, finite element analysis (FEA) were carried out to compare the outcome of the four different internal fixation methods. The results of Von Mises stress, displacement of four groups which contain talus fracture fragments and screws internal fixations were analyzed.ResultsCompared with the other three groups, postero-anterior (PA) parallel dual screws had better results in the stress peak, stress distribution, and displacement of talus and internal fixation.ConclusionsTo sum up, the Von Mises stress of fracture section was the smallest, the stress distribution of screws were the most scattered, and the peak value was the smallest in posterior to anterior parallel double screws fixation, which was obviously better than that in the other three groups. When using screws internal fixation, the method of posterior to anterior screws fixation is better than that of anterior to posterior screws fixation, and the peak value and stress distribution of parallel double screws fixation is better than that of cross double screws fixation. Thus, for the talar neck fracture, the use of posterior to anterior parallel double screws fixation is recommended in clinical surgery.

Feasibility of Double Anterior Odontoid Screw: A CT-Based Morphometric Analysis of the Axis in Adult Indian Population

The fractures of the odontoid process constitute 10% of all cervical spine injuries. Odontoid screw placement, although technically challenging, in indicated cases is the ideal treatment. Hence, a thorough knowledge of the odontoid dimensions is necessary prior to the surgical endeavor, more so for planning double odontoid screws. A prospective morphometric analysis of retrospective data of 250 patients was acquired at our institute using Somatom Definition edge 128 slice 64-row detector Siemens CT scanner. The dimensions of the odontoid process were measured at the waist (narrowest portion), widest diameter both in anteroposterior and transverse diameters. The dimensions of the C2 vertebra were measured at the level of the superior and inferior endplate in both the planes. A total of 250 patients were evaluated with age ranging from 1 to 80 years. Males constituted 174 (69.6%) and 76 (30.4%) were females. The mean transverse diameter (TD) at the odontoid waist (narrowest diameter) was 8.66 mm. The mean TD at the widest point of odontoid was 9.68 mm. Mean anteroposterior (AP) diameter 2.5 mm away from the midline on the left side at the level of the waist was 9.51 mm and 2.5 mm on the right of midline was 9.01 mm. The mean AP diameter at the C2 base was 15.824 mm in males and 14.833 mm in females (P < 0.001). Double odontoid screw insertion is feasible in only 36% of Indians in the transverse plane, whereas 98.4% of the odontoids can accommodate double screws in the sagittal plane.

Efficacy and Safety of Minimally Invasive Percutaneous Ilio-Sacral Fixation Technique for Sacral Fractures in The Initial Twenty Cases at Department of Neurosurgery in Alexandria University

Background Data: Sacral fractures constitute a major entity of pelvic fractures. 50% of these sacral fractures are not recognized on initial physical examination of the traumatized patients. The most important prognostic factor in management of sacral fractures is the presence or absence of neurological deficit. Some studies adopt the concern regarding fixation of sacral fractures in poly-traumatized patients to avoid systemic effects and complications of recumbency. Purpose: Evaluation of the efficacy and safety of the minimally invasive percutaneous ilio-sacral fixation technique in management of initial twenty cases of sacral fractures at department of Neurosurgery in Alexandria University. Study Design: Retrospective clinical case cohort study. Patients and Methods: Between March 2017 and January 2019; 20 patients were presented at Neurosurgery Department in Alexandria University hospitals with traumatic sacral fractures. They were 13 males and 7 females with the mean of 34 years (ranged from 18-55 years). Plain X ray of pelvis including antero-posterior, inlet and outlet views of pelvis, CT scan with 3D reconstructions were done. We used Dennis classification and Roy-Camille classification in our study. Stabilization of sacral fracture was done percutaneously using 7 mm cannulated partially threaded ilio-sacral screws. Clinical, neurologic and radiographic examinations were performed in the follow up period (6 months) to assess healing, evaluate clinical improvement and to detect any implant changes. Results: Total 39 percutaneous ilio-sacral screws were placed in 20 patients. Partially threaded cancellous 7.0-millimeter cannulated screws were used. Fifteen patients had unilateral double screws; one patient had unilateral triple screws; two patients had bilateral single screws for bilateral sacral fracture and two patients had unilateral single screw. Two Misplaced screws out of thirty-nine screws were found in the post-operative CT. One patient developed post-operative foot drop. All fractures healed clinically and radio-graphically except one case fixed by single screw and did not show radiological healing. Conclusion: Percutaneous ilio-sacral fixation for sacral fractures is a safe minimally invasive method for management of sacral fractures. It is effective regarding pain relief with high fusion rate. It needs a long learning curve. Single screw fixation is not a rigid fixation and may lead to hardware failure. (2019ESJ193)

双螺钉与三螺钉固定方式治疗胫骨平台Schatzker I型骨折的效果比较

双螺钉与三螺钉固定方式治疗胫骨平台Schatzker I型骨折的效果比较

Preparation of super-toughened PA6 with submicron-sized ABS by in situ reactive extrusion method

To improve the toughness of polyamide 6, ABS/PA6 blends were prepared by reactive extrusion via anionic ring opening polymerization of ε-caprolactam. The morphology and mechanical properties showed that ABS played a critical role in the compatibility, morphology, and toughness of reactive blends. Submicron-sized ABS was evenly dispersed in PA6 by in situ compatibilizing and strong shearing of double screws. By optimizing ABS contents, super toughened PA6 can be obtained, as evidenced by the significant improvement in the impact strength. This indicated the in situ reactive extrusion method should be useful for production of ABS/PA6 blends.

Pilot experiment of oily cuttings thermal desorption and heating characteristics study

Thermal desorption disposal of oily drilling cuttings was tested on the developed medium sized experimental system. The thermal desorption unit adopted electromagnetic induction heating during continuous conveying of materials by double screws, and the handling capability was 250 L/h. Thermal desorption test at different temperatures (300–550 °C) were carried out in conditions of residence times of 7 min and 12 min respectively. Total petroleum hydrocarbon (TPH) content of samples after treatment reduced to less than 1% when heating temperature up to 450 °C, and the oil removal rate was about 95%. The residual content of TPH dropped to 0.3% when heating temperature at 550 °C and residence time reached to 12 min. The temperature distribution of the material in heating bed obtained by numerical simulation based on test operating conditions. A temperature rising lag area of materials in filling section of barrel was found when heating. The material temperature in this area was only about 55–65% of the setting value when residence time reach to 12 min, while the other areas temperatures could up to above 90%, and the deviation between the material temperature and the setting value became obvious when the temperature is higher.

P.139 Fixation of Type II Odontoid fractures with anterior single screw

Background: More than 60% of spinal injuries affect the cervical spine,and approximately 20% of all cervical spine injuries involve the axis.The most common axis injury is odontoid fracture.The management of odontoid fractures became less controversial than before. Methods: Thirty consecutive patients(25 males and 5 females)who underwent anterior single screw fixation for recent Type II odontoid fractures at King Fahd Hospital,Al-Madina Al-Munawarah,in Saudi Arabia(SA) between January 2004 and December 2007 were included in this study.Data including clinical examination,imaging studies and operative technique were used to analyze the results of this surgical technique. Results: Single screw for fixation of type II odontoid fracture was found easier and simpler than double screws with the same advantages.This method resulted in immediate spinal stability and preserves normal rotation at C1–2 in all patients.Radiological evidence of bone union achieved in 22 patients(73% of cases);and nonunion in 8 patients(27% of cases).Complications related to surgical procedure and hardware failure were recorded in 4 patients(13% of cases). Conclusions: Direct anterior single screw fixation is an effective,simple,and safe method for treating type II odontoid fractures.It is associated with rapid patient mobilization,minimal postoperative pain,and shorter hospital stay.By this technique,the required anatomical and functional outcome can be obtained through immediate stability of the axis,preserves C1–2 rotatory motion,and achieved high union rate.

A Biomechanical Study of 3 Types of Scaphoid Fixation in a Fracture Non-union Model: N/A - Not a clinical study

Grant received from: AOA (Australian) Research Foundation Grant There is no financial information to disclose. Scaphoid fracture healing is related to inter-fragmentary displacement. In cases of non-union with bone resorption, this becomes more challenging to achieve. The null hypothesis of this study states there is no difference in the biomechanical stability of 3 different types of scaphoid fixation in a fracture non-union model. Thirty scaphoid cadaveric specimens were assigned to 3 different fixation groups: (1) Single 3.0mm cannulated compression screw, (2) 2 x 2.2mm cannulated compression screws and (3) scaphoid plate fixation. Standardized 3mm volar wedge osteotomies were used to create a scaphoid waist non-union model. All specimens were loaded using a servohydraulic axial force testing system at a rate of approximately 10N/s, from a dorsal to volar cantilever direction, oriented at 45 degrees to simulate physiologic loading. The primary outcome measure was load to failure. Secondary outcome measures were load to 2mm displacement, energy absorbed, construct stiffness and mode of failure, recorded by video and retrieval analysis. One-way ANOVA tests were used to analyze for differences between groups for parametric data and Kruskal-Wallis tests were used for non-parametric data. There was a significantly lower load to failure, in the single screw group compared to double screw fixation (mean difference: 187.2N, P = 0.005) and also in the single screw group compared to plate fixation (mean difference: 150.7N, P = 0.04). The mean load to 2mm displacement in the single screw group (91.5N) showed a trend towards being weaker than the double screw (181.8N, P = 0.08) and plate (197.2N, P = 0.06) fixation groups. There was a significantly lower stiffness in single screw compared with double screw (mean difference: 85.4N/mm, 95% CI [60.1,110.6], P = 0.03) and lower energy absorbed in single screw compared with double screw groups (mean 386.5mJ, P = 0.0042) and in single screw compared with plate fixation (mean difference: 270.8mJ, P = 0.02). The most common mode of failure was rotational failure (7/10), screw cut-out (7/10) and plate bending (6/10) in the single screw, double screw and plate fixation groups, respectively. •The null hypothesis is rejected: there is a difference in the biomechanical stability of 3 different types of scaphoid fixation in a fracture non-union model.•Double screw and plate fixation provides greater stability.•Single screw fixation is weakest due to rotational failure.•No significant differences between double-screws and plate groups.•The use of double screws or plate fixation in a non-union setting may allow accelerated rehabilitation without compromise to fracture stability and union.

Double opposing lag screws for internal fixation of talar neck fracture

Objective To report the process and clinical efficacy of internal fixation with double opposing lag screws for talar neck fractures. Methods From October 2005 to October 2012, we treated 13 patients with talar neck fracture. They were 8 males and 5 females, with a mean age of 37.9 years (range, from 26 to 56 years). According to the Hawkins classification of talar neck fractures, 2 had type I, 9 type Ⅱ, and 2 type Ⅲ. The right foot was involved in 9 of them. None of them sustained bilateral talar neck fractures. A concomitant medial malleolar fracture occurred in 4 of them. All the fractures were closed injury. All the patients received internal fixation with 2 opposing hollow screws of 3.5 mm in diameter which were inserted via the talus anterior or posterior approach and antegradely or retrogradely, respectively. Postoperative outcomes were evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale and visual analogue scale (VAS). Results The mean follow-up duration was 43.3 months (range, from 12 to 84 months). The mean interval required to achieve radiographic evidence of talar neck fracture healing was 10.2 weeks (range, from 9 to 12 weeks). No nonunion or malunion of the talar neck fracture or medial malleolar fracture occurred. The preoperative AOFAS ankle-hindfoot scale (5.4±4.1, from 0 to 12) was significantly improved to postoperative 89.7±8.1 (from 72 to 98) (t = 54.984, P < 0.001). Nine cases were rated as excellent, 3 as good and one as fair. The VAS pain score was significantly improved from 9.4±0.8 (from 8 to 10) preoperatively to 1.1±0.8 (from 0 to 3) postoperatively (t = 20.679, P <0.001). Conclusion Internal fixation with double opposing lag screws which are placed perpendicular to the oblique fracture line in the neck of the talus is a good operative treatment for talar neck fractures because it can provide satisfactory biomechanical stability and protect blood supply of the talus. Key words: Talus; Fractures, bone; Fracture fixation, internal; Bone screw

CERVICAL SPINOLAMINOPLASTY WITH NEWLY DESIGNED TITANIUM MINI-PLATES

One of the complication of cervical laminoplasty is the restenosis of the opened laminae. Weakness of the screws placed on laminae may cause restenosis. Here, we describe a new technic ‘spinolaminoplasty (Turkish Open-door laminoplasty)’ with newly designed titanium mini plate that placed one side to lateral mass, and the other on spinous process to keep the laminae opened. Two different fixation materials were used for axial compression tests. One was Ultra high molecular weight polyethylene block with cervical vertebrae geometry and fresh ovine cervical vertebrae. In the first group, mini plates were fixed on laminae as in the conventional method described by Hirabayashi. In the second group, mini plates were fixed on spinous process to perform spinolaminoplasty with single and double screws. New fixation method with double screw provides 26% higher stiffness than the closest group, namely new fixation on polyethylene block. And new fixation method with double screw was exhibited significantly higher ([Formula: see text]) performance between the Ovine groups. As in the spinolaminoplasty technic fixing the mini plates to spinous process with longer screws instead of laminae, strengthens the system compared to the conventional method. This proves that rigidity of new construction model is more stable than the conventional method. Tight fixed laminae may prevent restenosis. Also applying the screw through spinous process instead of laminae may prevent the possible cord injuries.