Standard Screw Research Articles

Pedicle screw anchorage of carbon fiber-reinforced PEEK screws under cyclic loading

PurposePedicle screw loosening is a common and significant complication after posterior spinal instrumentation, particularly in osteoporosis. Radiolucent carbon fiber-reinforced polyetheretherketone (CF/PEEK) pedicle screws have been developed recently to overcome drawbacks of conventional metallic screws, such as metal-induced imaging artifacts and interference with postoperative radiotherapy. Beyond radiolucency, CF/PEEK may also be advantageous over standard titanium in terms of pedicle screw loosening due to its unique material properties. However, screw anchorage and loosening of CF/PEEK pedicle screws have not been evaluated yet. The aim of this biomechanical study therefore was to evaluate whether the use of this alternative nonmetallic pedicle screw material affects screw loosening. The hypotheses tested were that (1) nonmetallic CF/PEEK pedicle screws resist an equal or higher number of load cycles until loosening than standard titanium screws and that (2) PMMA cement augmentation further increases the number of load cycles until loosening of CF/PEEK screws.MethodsIn the first part of the study, left and right pedicles of ten cadaveric lumbar vertebrae (BMD 70.8 mg/cm3 ± 14.5) were randomly instrumented with either CF/PEEK or standard titanium pedicle screws. In the second part, left and right pedicles of ten vertebrae (BMD 56.3 mg/cm3 ± 15.8) were randomly instrumented with either PMMA-augmented or nonaugmented CF/PEEK pedicle screws. Each pedicle screw was subjected to cyclic cranio-caudal loading (initial load ranging from − 50 N to + 50 N) with stepwise increasing compressive loads (5 N every 100 cycles) until loosening or a maximum of 10,000 cycles. Angular screw motion (“screw toggling”) within the vertebra was measured with a 3D motion analysis system every 100 cycles and by stress fluoroscopy every 500 cycles.ResultsThe nonmetallic CF/PEEK pedicle screws resisted a similar number of load cycles until loosening as the contralateral standard titanium screws (3701 ± 1228 vs. 3751 ± 1614 load cycles, p = 0.89). PMMA cement augmentation of CF/PEEK pedicle screws furthermore significantly increased the mean number of load cycles until loosening by 1.63-fold (5100 ± 1933 in augmented vs. 3130 ± 2132 in nonaugmented CF/PEEK screws, p = 0.015). In addition, angular screw motion assessed by stress fluoroscopy was significantly smaller in augmented than in nonaugmented CF/PEEK screws before as well as after failure.ConclusionsUsing nonmetallic CF/PEEK instead of standard titanium as pedicle screw material did not affect screw loosening in the chosen test setup, whereas cement augmentation enhanced screw anchorage of CF/PEEK screws. While comparable to titanium screws in terms of screw loosening, radiolucent CF/PEEK pedicle screws offer the significant advantage of not interfering with postoperative imaging and radiotherapy.Graphical abstractThese slides can be retrieved under Electronic Supplementary Material.

The Ponticulus Posticus as Risk Factor for Screw Insertion into the First Cervical Lateral Mass.

Awareness of the osseous anomaly of ponticulus posticus (PP) is crucial in avoiding vertebral artery (VA) injuries during C1 instrumentation. The aim of this study was to investigate PP and its relationship with the VA with three-dimensional computed tomography angiography. PP and the VA were investigated as intraoperative landmarks. The intersection of the VA to the posterior arch of C1 and the medial line and the posterior arch and VA curve around lateral masses were measured as intraoperative references. PP was identified in 14.3% of samples. The anomaly was more common in women and on the right side. Of cases, 48.2% had PP bilaterally. In PP cases, the VA had variable courses through C2 before it passed under its bony bridges on the posterior arch of C1. Mean distances were found at the intersection of the VA to the posterior arch of C1 and the medial line to be larger and the posterior arch of C1 and the VA curve around lateral masses to be narrower than normal cases. Dual computed tomography scan data from C1 with PP were used to create three-dimensional patient-specific life-sized cervical spine models. Models revealed how the bone bridge affected the VA. The feasibility (>4 mm) of a safe lateral mass screw fixation was not influenced by PP anomalies. The presence of the PP loop can limit space available for placement of the screw through the bony elements of C1. Standard screw techniques are contraindicated owing to the unacceptable high risk of VA injury.

Comparison of the Pullout Strength of Different Pedicle Screw Designs and Augmentation Techniques in an Osteoporotic Bone Model.

Study DesignMechanical study.PurposeTo compare the pullout strength of different screw designs and augmentation techniques in an osteoporotic bone model.Overview of LiteratureAdequate bone screw pullout strength is a common problem among osteoporotic patients. Various screw designs and augmentation techniques have been developed to improve the biomechanical characteristics of the bone–screw interface.MethodsPolyurethane blocks were used to mimic human osteoporotic cancellous bone, and six different screw designs were tested. Five standard and expandable screws without augmentation, eight expandable screws with polymethylmethacrylate (PMMA) or calcium phosphate augmentation, and distal cannulated screws with PMMA and calcium phosphate augmentation were tested. Mechanical tests were performed on 10 unused new screws of each group. Screws with or without augmentation were inserted in a block that was held in a fixture frame, and a longitudinal extraction force was applied to the screw head at a loading rate of 5 mm/min. Maximum load was recorded in a load displacement curve.ResultsThe peak pullout force of all tested screws with or without augmentation was significantly greater than that of the standard pedicle screw. The greatest pullout force was observed with 40-mm expandable pedicle screws with four fins and PMMA augmentation. Augmented distal cannulated screws did not have a greater peak pullout force than nonaugmented expandable screws. PMMA augmentation provided a greater peak pullout force than calcium phosphate augmentation.ConclusionsExpandable pedicle screws had greater peak pullout forces than standard pedicle screws and had the advantage of augmentation with either PMMA or calcium phosphate cement. Although calcium phosphate cement is biodegradable, osteoconductive, and nonexothermic, PMMA provided a significantly greater peak pullout force. PMMA-augmented expandable 40-mm four-fin pedicle screws had the greatest peak pullout force.

Wine yeast phenomics: A standardized fermentation method for assessing quantitative traits of Saccharomyces cerevisiae strains in enological conditions.

This work describes the set up of a small scale fermentation methodology for measuring quantitative traits of hundreds of samples in an enological context. By using standardized screw cap vessels, the alcoholic fermentation kinetics of Saccharomyces cerevisiae strains were measured by following their weight loss over the time. This dispositive was coupled with robotized enzymatic assays for measuring metabolites of enological interest in natural grape juices. Despite the small volume used, kinetic parameters and fermentation end products measured are similar with those observed in larger scale vats. The vessel used also offers the possibility to assay 32 volatiles compounds using a headspace solid-phase micro-extraction coupled to gas chromatography and mass spectrometry. The vessel shaking applied strongly impacted most of the phenotypes investigated due to oxygen transfer occuring in the first hours of the alcoholic fermentation. The impact of grape must and micro-oxygenation was investigated illustrating some relevant genetic x environmental interactions. By phenotyping a wide panel of commercial wine starters in five grape juices, broad phenotypic correlations between kinetics and metabolic end products were evidentiated. Moreover, a multivariate analysis illustrates that some grape musts are more able than others to discriminate commercial strains since some are less robust to environmental changes.

Management of distal femoral diaphyseal fractures with string of pearls locking plate in dogs

Distal femoral diaphyseal fractures in six dogs about 10-22 months old with body weight ranging from 12-25 kg were stabilized with String of Pearls (SOP) (Orthomed, UK) locking plates along with standard cortical and cancellous screws following standard AO/ASIF principles. Selection of appropriate size of plate and screws was according to body weight and type of fracture (2.7mm plate for dogs below 12 kg body weight and 3.5 mm plate for dogs above 12 kg body weight) which provided good fracture stability. The outcome of fracture stabilization and healing was evaluated with lameness grading and radiography. Postoperatively, all the animals showed weight bearing with early functional limb usage of grade I lameness and good joint mobility in an average of 7 weeks. Functional outcome was excellent in good in four cases and excellent in two cases. The average overall healing time in all the cases was 7-11 weeks. The fractures showed radiographically excellent postoperative healing of cortical union, absence of fracture lines with limited and also bridging callus. Based on present study, it was concluded that, String of Pearls (SOP) locking plates were good for stabilization of distal femoral diaphyseal fractures for early limb ambulance and healing.

Technique for the removal of a locking screw from a broken locking plate following cold welding

The advent of locking plates has brought new problems in implant removal. Difficulties include cold welding between the screw head and locking screw hole, stripping of the recess of the screw head for the screwdriver, and cross-threading between threads in the screw head and screw hole. We are describing a technique which allowed us to remove such cold-welded, jammed single screw with simple instruments at hand and complete the prescribed operation smoothly. A 32-year-old female patient reported to us with a broken clavicle locking plate, who was operated 3 years back for fracture clavicle right side. The patient had complaints of pain and deformity in the right clavicle region for 3 months following lifting heavy weight. X-ray showed broken implant with nonunion of clavicle. The patient was planned for implant removal, freshening of edges, and fixation with anatomical clavicle plate with bone grafting. All the screws were removed with standard screw driver when it was found that the second screw of medial broken plate was jammed, round headed, and cold welded. We bent both ends of broken medial plate around screw and removed screw by just rotating bent plate anticlockwise. Fracture ends were freshened and fixation was done with anatomical clavicle locking plate and bone grafting. The patient did not develop any postoperative complication. This technique is very quick, easy to perform, and inexpensive without the use of plate cutting blade, burr, hollow mill, and other instrumentation. This technique can be used in peripheral hospitals in India where advanced gadgetries may not be available. There is no problem of thermal necrosis to the bone or the surrounding soft tissue. Osteoporotic bone is a limitation of the above method as the bone may break while bending the plate and is possible only with a single locking screw.

The morphology of proximal pole scaphoid fractures: implications for optimal screw placement.

The purpose of this study was to measure the radiographic parameters of proximal pole scaphoid fractures, and calculate the ideal starting points and trajectories for antegrade screw insertion. Computed tomography scans of 19 consecutive patients with proximal pole fractures were studied using open source digital imaging and communications in medicine (DICOM) imaging measurement software. For scaphoid sagittal measurements, fracture inclination was measured with respect to the scaphoid axis. The ideal starting point for a screw in the proximal pole fragment was then identified on the scaphoid sagittal image that demonstrated the largest dimensions of the proximal pole, and hence the greatest screw thread purchase. Measurements were then taken for a standard screw trajectory in the axis of the scaphoid, and a trajectory that was perpendicular to the fracture line. The fracture inclination in the scaphoid sagittal plane was 25 (SD10) °, lying from proximal palmar to dorsal distal. The fracture inclination in the coronal plane was 9 (SD16) °, angling distal radial to proximal ulnar with reference to the coronal axis of the scaphoid. Using an ideal starting point that maximized the thread purchase in the proximal pole, we measured a maximum screw length of 20 (SD 2) mm when using a screw trajectory that was perpendicular to the fracture line. This was quite different from the same measurements taken in a trajectory in the axis of the scaphoid. We also identified a mean distance of approximately 10 mm from the dorsal fracture line to the ideal starting point. A precise understanding of this anatomy is critical when treating proximal pole scaphoid fractures surgically.

Digital blinding of radiographs to mask allocation in a randomized control trial

AIMTo demonstrate the effectiveness of a digital radiographic altering technique in concealing treatment allocation to blind outcome assessment of distal femur fracture fixation.METHODSDigital postoperative anteroposterior and lateral radiographs from a sample of 33 randomly-selected patients with extra-articular distal femur fractures treated by surgical fixation at a Level 1 trauma center were included. Using commercially available digital altering software, we devised a technique to blind the radiographs by overlaying black boxes over the implant hardware while preserving an exposed fracture site for assessment of fracture healing. Three fellowship-trained surgeons evaluated a set of blinded radiographs twice and a control set of unblinded radiographs once. Each set of radiographs were reviewed independently and in a randomly-assigned order. The degrees of agreement and disagreement among evaluators in identifying implant type while reviewing both blinded and unblinded radiographs were assessed using the Bang Blinding Index and James Blinding Index. The degree of agreement in fracture union was assessed using kappa statistics.RESULTSThe assessment of blinded radiographs with both the Bang Blinding Index (BBI) and James Blinding Index (JBI) demonstrated a low degree of evaluator success at identifying implant type (Mean BBI, far cortical locking: -0.03, SD: 0.04; Mean BBI, standard screw: 0, SD: 0; JBI: 0.98, SD: 0), suggesting near perfect blinding. The assessment of unblinded radiographs with both blinding indices demonstrated a high degree of evaluator success at identifying implant type (Mean BBI, far cortical locking: 0.89, SD: 0.19; Mean BBI, standard screw: 0.87, SD: 0.04; JBI: 0.26, SD: 0.12), as expected. There was moderate agreement with regard to assessment of fracture union among the evaluators in both the blinded (Kappa: 0.38, 95%CI: 0.25-0.52) and unblinded (Kappa: 0.35, 95%CI: 0.25-0.45) arms of the study. There was no statistically significant difference in fracture union agreement between the blinded and unblinded groups.CONCLUSIONThe digital blinding technique successfully masked the surgeons to the type of implant used for surgical treatment of distal femur fractures but did not interfere with the surgeons’ ability to reliably evaluate radiographic healing at the fracture site.

Comparison of S2-Alar and traditional iliac screw pelvic fixation for pediatric neuromuscular deformity

Background ContextMany pelvic fixation options exist for posterior spinal fusion of pediatric neuromuscular scoliosis, including standard iliac screws (SISs) or a more recently introduced S2-Alar (S2A) technique. However, little data exist comparing the clinical and radiographic outcomes of these techniques. PurposeThis study aimed to dentify differences in clinical and radiographic outcomes for pediatric neuromuscular scoliosis patients treated with SIS or S2A pelvic fixation. Study Design/SettingThis was a retrospective cohort study at a pediatric orthopedic clinic. Patient SamplePatients aged 8–19 years undergoing posterior spinal fusion to the pelvis for neuromuscular scoliosis using SIS or S2A technique, with Gross Motor Function Classification System (GMFCS) Level 4 or 5 were included. Outcomes MeasuresPostoperative complication rates associated with pelvic fixation method were the outcome measures. MethodsCharts and radiographs were reviewed for demographics, intra- and postoperative course, levels of instrumentation, operative correction, and implant failure (IF). Postoperative complications were classified according to the Accordion scale. ResultsWe studied 50 patients (28 SIS, 22 S2A) aged 14.0±2.8 years and an average follow-up of 3.5±1.7 years. The average number of levels fused was 16.5±1.1 with an average curve correction of 48°±21° postoperatively. A significant difference in radiographic IF rates was noted between SIS and S2A groups (57% vs. 27%, p=.02). No difference was noted between groups for frequency or severity of postoperative complications, inclusive of wound infections. Subgroup analysis demonstrated equivalent IF rates when comparing the S2A group with the SIS group with cross-links. ConclusionsThe S2A group generally demonstrated improved rates of radiographic IF compared with the SIS group, but the rates became equivalent when a cross-link was added to an SIS construct. Further, no difference in postoperative complication rates were identified between SIS and S2A groups.

Biomechanical comparison of fixation stability using a Lisfranc plate versus transarticular screws

BackgroundTo obtain adequate fixation in treating Lisfranc soft tissue injuries, the joint is commonly stabilized using multiple transarticular screws; however iatrogenic injury is a concern. Alternatively, two parallel, longitudinally placed plates, can be used to stabilize the 1st and 2nd tarsometatarsal joints; however this may not provide adequate stability along the Lisfranc ligament. Several biomechanical studies have compared earlier methods of fixation using plates to the standard transarticular screw fixation method, highlighting the potential issue of transverse stability using plates. A novel dorsal plate is introduced, intended to provide transverse and longitudinal stability, without injury to the articular cartilage. MethodsA biomechanical cadaver model was developed to compare the fixation stability of a novel Lisfranc plate to that of traditional fixation, using transarticular screws. Thirteen pairs of cadaveric specimens were tested intact, after a simulated Lisfranc injury, and then following implant fixation, using one method of fixation randomly assigned, on either side of each pair. Optical motion tracking was used to measure the motion between each of the following four bones: 1st metatarsal, 2nd metatarsal, 1st cuneiform, and 2nd cuneiform. Testing included both cyclic abduction loading and cyclic axial loading. ResultsBoth the Lisfranc plate and screw fixation method provided stability such that the average 3D motions across the Lisfranc joint (between 2nd metatarsal and 1st cuneiform), were between 0.2 and 0.4mm under cyclic abduction loading, and between 0.4 and 0.5mm under cyclic axial loading. Comparing the stability of fixation between the Lisfranc plate and the screws, the differences in motion were all 0.3mm or lower, with no clinically significant differences (p>0.16). ConclusionsDiastasis at the Lisfranc joint following fixation with a novel plate or transarticular screw fixation were comparable. Therefore, the Lisfranc plate may provide adequate support without risk of iatrogenic injury to the articular cartilage.

Accuracy of cannulated pedicle screw versus conventional pedicle screw for extra-pedicular screw placement in dysplastic pedicles without cancellous channel in adolescent idiopathic scoliosis: a computerized tomography (CT) analysis.

This study aimed at studying the accuracy and safety of extra-pedicular screw insertion for dysplastic pedicles in AIS comparing cannulated screw system versus conventional screw system. 104 AIS patients with 1524 pedicle screws were evaluated using CT scan. 302 screws were inserted in dysplastic pedicles using fluoroscopic guidance technique. 155 screws were inserted using a cannulated system (Group 1), whereas 147 screws were inserted using standard screws (Group 2).The pedicle perforations were assessed using a classification by Rao et al.; G0: no violation; G1: <2mm perforation; G2: 2-4mm perforation; and G3: >4mm perforation). For anterior perforations, the pedicle perforations were assessed using a modified grading system (Grade 0: no violation, Grade 1: less than 4mm perforation; Grade 2: 4mm to 6mm perforation; and Grade 3: more than 6mm perforation). The perforation rate in Group 1 was4.5%and in Group 2 was15.6%(p=0.001). Most of the perforations were anterior perforations (53.3%). The anterior perforation rate in Group 1 was 1.9% compared to 8.8% in Group 2 (p=0.009). Group 1 has a medial perforation rate of 1.3% compared to Group 2, 6.1% (p=0.031). The rate of critical pedicle perforation in Group 1 was2.6%and in Group 2 was6.8%(p=0.102). InGroup 1, there wereno critical medial perforationbut there wasone G2 lateral perforation, one G2 superior perforation and two G3 anterior perforations. In Group 2, there werethree G2 medial perforations, one G2 lateral perforation, one G2 anterior perforation and five G3 anterior perforations. Usage of cannulated screw system significantly increases the accuracy of pedicle screw insertion in dysplastic pedicles in AIS.

Development and evaluation of an oral fast disintegrating anti-allergic film using hot-melt extrusion technology.

The main objective of this novel study was to develop chlorpheniramine maleate orally disintegrating films (ODF) using hot-melt extrusion technology and evaluate the characteristics of the formulation using in vitro and in vivo methods. Modified starch with glycerol was used as a polymer matrix for melt extrusion. Sweetening and saliva-simulating agents were incorporated to improve palatability and lower the disintegration time of film formulations. A standard screw configuration was applied, and the last zone of the barrel was opened to discharge water vapors, which helped to manufacture non-sticky, clear, and uniform films. The film formulations demonstrated rapid disintegration times (6-11s) and more than 95% dissolution in 5min. In addition, the films had characteristic mechanical properties that were helpful in handling and storage. An animal model was employed to determine the taste masking of melt-extruded films. The lead film formulation was subjected to a human panel for evaluation of extent of taste masking and disintegration.

The Role of Platelet Rich Plasma on Healing of Induced Femoral Fracture Fixed With Dynamic Compression Plate in Dogs.

The present study was carried out to evaluate the platelet rich plasma (PRP) as a factor for accelerating bone healing and compared with normal healing in 18 apparently healthy male mongrel dogs based on clinical, radiographic and histopathological findings. Induction of femoral fracture was done in all dogs of both groups, a gap (0.5 cm × 0.5cm with the whole depth of the near cortex) was created at the fracture sit bone rongeur and the fracture was fixed with standard dynamic compression plate (DCP) and self taping cortical screws. Dogs were divided into two equal groups, each of 9 dogs. Group I was left as a control. In group II, the gap was packed with autogenous PRP. The results of this study pointed out that PRP slightly improved bone healing.

Iliac Crest Graft and Hydroxyapatite/ Β Tri- Calcium Phosphate for Repairing of Femoral Fracture: an Experimental Study

The present work was conducted for evaluation of the effects of iliac crest autograft (ICBG) and Hydroxyapatite / β tri- calcium phosphate (HA / β -TCP), on the healing process of an experimentally induced right femoral fractures with 0.5 cm × 0.5 cm partial bone defect at the fracture site in dogs fixed with standard dynamic compression plate (DCP) and self taping cortical screws. It was carried out on twenty seven apparently healthy male mongrel dogs divided into three equal groups, each of 9 dogs. Group I left as a control. Groups II and III were treated with ICBG and HA / β -TCP respectively. Clinical, radiographical and histological examinations were carried out for judgment of the healing process. This study came to the conclusion of; ICBG provides the most dense callus formation and the fastest possible healing. While, HA / β -TCP was an excellent substitute for ICGB that solve the problem of two operations on the same animal.

Introducing the \u201cBone-Screw-Fastener\u201d for improved screw fixation in orthopedic surgery: a revolutionary paradigm shift?

BackgroundConventional screws used for fracture fixation in orthopedic surgery continue to rely on the historic buttress thread design. While buttress screws generally provide solid resistance against unidirectional axial loading forces, their design suffers from several limitations, as the buttress thread does not adequately resist multiaxial forces. Furthermore, the buttress screw is prone to stripping at the bone-screw interface and can cause microfracturing of the surrounding bone due to its thread design. Standard buttress screws are therefore at risk of adverse postoperative outcomes secondary to failure of bone fixation. A new patented Bone-Screw-Fastener was recently designed that is based on an interlocking thread technology. This new fastener provides distributive forces from the threads onto the bone and therefore resists loads in multiple directions. The underlying concept is represented by a “female thread” bone cutting technology designed to maximize bone volume, preserve bone architecture, and create a circumferential interlocking interface between the implant and bone that protects the thread from stripping and from failing to multiaxial forces.Presentation of the hypothesisWe hypothesize that the new Bone-Screw-Fastener overcomes the classic shortcomings of conventional orthopedic screws with buttress threads by ease of insertion, improved bone preservation, increased resistance to off-axis multidirectional loading forces and to stripping of the threads. These advanced biomechanical and biological properties can potentially mitigate the classic limitations of conventional buttress screws by providing better resistance to implant failure under physiological loads, preserving bone biology, and thus potentially improving patient outcomes in the future.Testing the hypothesisThe presumed superiority of the new fastener will require testing and validation in well-designed prospective multicenter randomized controlled trials (RCTs), using the conventional buttress screw as control.Implications of the hypothesisOnce validated in multicenter RCTs, the new Bone-Screw-Fastener may drive a change in paradigm with regard to its innovative biomechanical principles and biologic bone preservation for surgical applications requiring screw fixation.

Making internal fixation work with limited bone stock

Fractures are common in small animal practice and there are many options for managing them. Plates and screws remain a popular means to manage many fractures; however, some fractures are...

Screw Stripping After Repeated Cortical Screw Insertion-Can We Trust the Cancellous "Bailout" Screw?

During osteosynthesis standard nonlocking cortical screws often require reinsertion, raising concern over possible decrease in their effectiveness. This study aims to quantify that potential loss of fixation with reinsertions as well as examine the ability of a cancellous "bailout screw" to regain insertion torque in a previously stripped screw hole. Four different types of bone surrogates were chosen to represent normal cortical bone, osteoporotic cortical bone, high-density (normal) cancellous bone, and low-density (osteoporotic) cancellous bone; nonlocked 3.5-mm cortical screws were inserted into the predrilled holes 1, 2, 3, 4, or 5 times before being torqued maximally to the point of stripping. A 4.0-mm cancellous "bailout" screw was then placed into the same hole and torqued until stripping. Torque was measured continuously using a torque-measuring screwdriver and maximal insertion torque (MIT) of 3.5 and 4.0 screws before stripping was recorded. MIT decreased with reinsertion of nonlocked cortical screws. By the third reinsertion in all but the normal bone surrogates, the screws lost approximately one third to one half of their original MIT (50%-71% of original torque). The bailout screw succeeded in restoring the original MIT in the osteoporotic cancellous bone surrogate and the normal cortical bone surrogate. In the normal cancellous and osteoporotic cortical bone surrogates, the bailout screw was only able to restore an average of 50% (range 31%-63%) of the original MIT. Screw reinsertion may significantly reduce the MIT of 3.5-mm nonlocked cortical screws. Use of the bailout cancellous screw for a stripped cortical screw should be expected to restore MIT only in normal cortical bone and osteoporotic cancellous bone. In other scenarios, the bailout screw should not be expected to uniformly restore full insertion torque.

The Detection of Prominent Hardware in Volar Locked Plating of Distal Radius Fractures: Intraoperative Fluoroscopy Versus Computed Tomography

To assess the utility of the dorsal tangential view (DTV) in detecting intraoperative dorsal screw penetration in distal radius fractures treated with volar locked plating. Retrospective cohort study. Academic level 1 trauma center. Skeletally mature patients where open reduction internal fixation with volar locked plating was the definitive treatment. A total of twenty-six patients were evaluated. Intraoperative anteroposterior, lateral, 20 degree tilted lateral, and DTVs were obtained through fluoroscopy in all wrists. Screw exchange and position by fluoroscopic view was recorded. A computed tomography (CT) was taken postoperatively to identify residual prominent screws. Data points included frequency of screw exchange by standard fluoroscopic views, the DTV, and residual prominent screws detected by CT. Eight constructs of thirty (27%) had prominent screws evident on the DTV but not seen on standard fluoroscopic analysis. CT identified 5 additional screws with ≥1 mm dorsal penetration not identified by the DTV. All except 1 screw was in the second dorsal wrist compartment. The DTV was 67% sensitive with a negative predictive value of 97%. It is risky and unnecessary to place bicortical screws in the distal part of a volar plate. Given that the DTV view was not sufficient to avoid dorsal screw prominence, distal screws should be intentionally 2-4 mm shorter than measured. Recent studies propose bicortical distal locking screws are not needed for sufficient construct stiffness in volar locked plating. We suggest caution when using this view to verify acceptable placement of screws in proximity to the second dorsal compartment. Diagnostic level III. See Instructions for Authors for a complete description of levels of evidence.

Does an additional antirotation U-Blade (RC) lag screw improve treatment of AO/OTA 31 A1-3 fractures with gamma 3 nail?

IntroductionPoor bone quality and unstable fractures increase the cut-out rate in implants with gliding lag screws. The U-Blade (RC) lag screw for the Gamma3® nail was introduced to provide monoaxial rotational stability of the femoral head and neck fragment. The purpose of this study was to evaluate whether the use of the U-Blade (RC) lag screw is associated with reduced cut-out in patients with OTA/AO 31A1-3 fractures. Material & methodsBetween 2009 and 2014, 751 patients with OTA/AO 31A1-3 fractures were treated with a Gamma3® nail at our institution. Out of this sample 199 patients were treated with U-blade (RC) lag screws. A total of 135 patients (117 female, 18 male) with standard lag screw (treatment group A) were matched equally regarding age (±4 years) sex, fracture type and location to 135 patients with U-blade (RC) lag screw (treatment group B). Within a mean follow up of 9.2 months (range 6–18 months) we assessed the cut-out rate, the calTAD, lag screw migration, the Parker's mobility score and the Parker’s ratio at postoperatively, six and 12 months following surgery. Furthermore we recorded all complications, ASA-Score, hospital stay and duration of surgery retrospectively. ResultsThe most common fracture among group B with a cut-out of the lag screw were AO/OTA 2.3 and 3.2 fractures whereas in group A cut-out was most commonly seen in AO/OTA 2.1, 2.2 and 2.3 fractures, there was no significant reduction of the cut-out rate in group B 2.2% (n=3) compared to group A 3.7% (n=5). The duration of surgery was significantly shorter in group A (p<0.05). There was no significant difference in lag screw placement, the Parker’s ratio and mobilization. ConclusionIn our study the U-Blade (RC) lag screw did not reduce the cut-out in treatment of OTA/AO 31A1-3 fractures at all. Considering the longer duration of surgery and the higher costs of the U-Blade (RC) lag screw, our results do not justify its use. However, further prospective randomized studies will be necessary.

Fixation strength of four headless compression screws

To promote a quicker return to function, an increasing number of patients are treated with headless screws for acute displaced and even non-displaced scaphoid fractures. Therefore, it is imperative to understand and optimize the biomechanical characteristics of different implants to support the demands of early mobilization. The objective of this study was to evaluate the biomechanical fixation strength of 4 headless compression screws under distracting and bending forces. The Acutrak Standard, Acutrak Mini, Synthes 3.0, and Herbert-Whipple screws were tested using a polyurethane foam scaphoid fracture model. Implants were inserted into the foam blocks across a linear osteotomy. Custom fixtures applied pull-apart and four-point bending forces until implant failure. Pull-apart testing was performed in three different foam densities in order to simulate osteoporotic, osteopenic, and normal bone. The peak pull-apart forces varied significantly between implants and were achieved by (from greatest to least): the Acutrak Standard, Synthes 3.0, Acutrak Mini, and Herbert-Whipple screws. The fully threaded screws (Acutrak) failed at their proximal threads while the shanked screw (Synthes and Herbert Whipple) failed at their distal threads. Similarly, the screws most resistant to bending were (from greatest to least): the Acutrak Standard, Acutrak Mini, Herbert-Whipple, and Synthes. Although the amount of force required for pull-apart failure increased with each increasing simulated bone density (a doubling in density required triple the amount of pull apart force), the mode and sequence of failure was the same. Overall, the fully threaded, conical design of the Acutrak screws demonstrated superior fixation against pull-apart and bending forces than the shanked designs of the Synthes and Herbert-Whipple. We also found a strong relationship between simulated bone density and pull-apart force.