Standard Screw Research Articles

Standardizing Screw Head Orthopaedic Trauma Implants. Is There an Interest? An OTA Member Survey.

To determine the level of interest in standardization of design for fracture fixation implants within the orthopaedic trauma community. A survey regarding implant removal concerns and implant design preferences was electronically distributed to members of Orthopaedic Trauma Association (OTA). Three hundred thirty respondents participated in the survey (response rate of 19%) Only 2.4% of respondents indicated a consistent ability to identify the implant vendor and/or manufacturer of retained implants in the preoperative planning phase of care; >75% of respondents reported investing a minimum of an additional 30 minutes to their operative times to remove screw(s) to successfully extract a plate. More than 80% of respondents reported multiple occurrences requiring modification of their surgical plans because of implants that could not be removed, preventing the completion of the planned procedure. The majority of respondents expressed interest in the adoption of standardized locking head screws for mini, small, and large screw sizes sets (63.5%); 84.8% of respondents desire standardization of screw head and driver sizes across the industry. Also, 83.6% of respondents expressed interest in the adoption of a standardized locking screw head for each cannulated screw, regardless of manufacturer. Members of the orthopaedic community, as represented in the membership of the OTA, are interested in the adoption of universal standards in implant design. Establishing standard screw heads and drivers will optimize the delivery of operative care.

Comparative biomechanical performance of two configurations of screw constructs and types used to stabilize different sites of unstable Pauwels type II femoral neck fractures: A finite element analysis

A smaller dimension of the femoral neck in the Asian population may have difficulty placing inverted triangle multiple screws configuration for treatment. Posterior triangle configuration, which is suitable in limited space of the femoral neck, is a promising alternative treatment approach. This study aimed to investigate the biomechanical performance of inverted and posterior triangles of multiple screws fixation configuration for both cannulated and standard solid-core screws in stabilizing Pauwels type II femoral neck fracture sub-capital, mid-cervical, and basilar regions using Finite Element (FE) method. A 3D femur model was created for Pauwels type II femoral neck fractures. The fracture sites were in the mid-cervical, sub-capital, and basilar regions, with a spacing of 7 mm between adjacent fracture lines. Both cannulated and solid-core screws were configured in the inverted and posterior triangle patterns. The applied physiological loads to the FE models included muscle and hip contact forces. Equivalent von Mises (EQV) stresses were used to monitor fixation strength whereas elastic strain of each configuration indicated the degree of stability of a fracture site. EQV stress on the screws for posterior and inverted triangle configuration ranged from 212.1 to 290.2MPa, and 224.4-314.8MPa, respectively. The EQV stress the posterior triangle configuration was lower than the inverted triangle configuration by 5.5-10.8%. The stress exhibited on the screw was greatest when the fracture site was at basilar regions, 1.1-1.3 times greater than fracture in sub-capital region. Elastic strain at fractures retained by cannulated screw was greater than solid-core screw with maximum difference of 68 microstrains. Cannulated screw provided less stability than the solid-core screw. The screws used in the posterior triangle configuration exhibits lower screw stress in all fracture regions of the femoral neck. The solid-core screw shows superior biomechanical properties compared with cannulated screw with lower EQV stress and better fracture stability. Posterior triangle configuration is considered an alternative treatment of choice for the patient with a small dimension of the femoral neck.

An Anatomic Study of the Proximal Tibial Epiphysis With Relevance to Percutaneous Epiphysiodesis Using Transphyseal Screws (PETS).

Percutaneous epiphysiodesis using transphyseal screws (PETS) is a common procedure to correct lower extremity limb-length discrepancies in the pediatric population. A potential complication of this procedure is development of tibial valgus deformity, which may occur secondary to decreased screw purchase in the thinner medial proximal tibial epiphysis. The thickness of the proximal tibial epiphysis has not yet been well quantified, which was the aim of this study. Three-dimensional surface scans of 32 cadaveric proximal tibial epiphyses in specimens aged 3 to 17 years old were obtained and computer modeling software was utilized to measure the thickness of the proximal tibial epiphysis at 20 standardized potential screw insertion points according to a generated 5×4 map. When normalized to the total width of the proximal tibial epiphysis, the lateral side is thicker compared with the medial side. The positions with the greatest thickness are located at the midline in the sagittal plane and 33% of the total physeal width away from the medial and lateral edges in the coronal plane (0.265 and 0.261 normalized thickness, respectively). The proximal tibial epiphysis is particularly thin 25% from the medial edge (normalized thickness range: 0.196 to 0.221). Multiple regression analysis revealed a significant relationship between increasing age and female sex with thinner normalized medial and lateral heights. During PETS, areas for greater screw purchase are located centrally in the sagittal plane and 33% of the total width away from the medial and lateral edges of the proximal tibial epiphysis in the coronal plane. Caution should be taken when inserting screws in the medial 25% of the proximal tibial epiphysis as it is thinner relative to the lateral edge, particularly in females. This study provides quantitative, anatomic data on the thickness of the proximal tibial epiphysis, which can direct screw placement during PETS for correcting limb-length discrepancies. These data may help lessen the risk of developing tibial valgus deformity although future clinical studies are necessary to fully evaluate this possibility.

Mechanical evaluation of canine sacroiliac joint stabilization using two short screws.

To assess the feasibility and mechanical stability of sacroiliac (SI) joint stabilization using 2 short 3.5 mm cortical screws, each spanning an average of 23% of the width of the sacral body. Cadaveric experimental study. Twenty-four canine pelvis specimens. Pelvis specimens were prepared by disarticulation of the left SI joint and osteotomy of the left pubis and left ischium, and stabilized using a single long lag screw (LLS), 2 short lag screws (SLS) or 2 short positional screws (SPS). Computed tomography (CT) imaging was used to determine standardized screw lengths for each group and was repeated following implant insertion. Specimens were secured within a servohydraulic test frame and loaded through the acetabulum to simulate weight bearing under displacement control at 4 mm/min for 20 mm total displacement. Group mechanical testing data were compared. Peak load, yield load, and stiffness were more than 2 times greater in both the SLS and SPS groups when compared with the LLS group. No mechanical difference was identified between the short-screw groups. Sacroiliac luxation fixation using 2 short screws created a stronger, stiffer construct when compared with fixation using a single lag screw spanning 60% of the width of the sacral body. No mechanical advantage was observed between short screws inserted in positional vs. lag fashion. Sacroiliac luxation fixation using 2 short screws creates a mechanically superior construct with a larger region of acceptable implant positioning and potentially reduced risk of iatrogenic injury compared with conventional fixation.

Biomechanical comparisons of hook plate and screw fixations in split-type greater tuberosity fractures of the humerus.

Screws and plate are commonly utilized for the fixation of split-type humeral greater tuberosity (GT) fractures. However, the mechanical properties of these 2 types of fixation methods have not been compared directly. The aim of the present study was to evaluate the classic 2 screws fixation with hook locking plate from a mechanical perspective. Sixteen synthetic humerii (Sawbones Pacific Research Laboratories, Vashon, WA, USA) were divided into 2 groups. An osteotomy was performed to simulate a split-type GT fracture. Group A (n=8) was fixed with 2 standard parallel screws. Group B (n=8) was fixed with a hook plate. Each specimen was tested with traction force at 45° shoulder abduction. Following the 20-N preload, a 500-cycle loading test was applied with a force ranging from 20 to 200N (valley/peak), and the interfragmental displacement was measured periodically at intervals of 100 cycles. Finally, all the specimens were pulled with destructive force at a rate of 5mm/min until catastrophic failure. The hook plate exhibited greater construct stiffness than the screw fixation (63.2±6.1N/mm vs. 40.9±3.4N/mm, P<.001). All of the specimens completed the entire cyclic loading test without catastrophic failure, and the fragment displacement after 500 cycles was 0.4±0.2mm for the hook plate and 2.1±0.3mm for screw fixation, which was statistically lower in the plate group (P<.001). In terms of failure load, the hook plate group exhibited a significantly greater value than the screw group (770.6±94.6 vs. 427.5±45.1N/mm, P<.001). The failure modes of both fixation methods were distinct. In humeral GT fracture fixation, hook plate fixation appears to offer greater construct stiffness and failure load while maintaining fragment stability to resist a physiological traction force. The current study provides support from a mechanical perspective for the clinical application of the hook plate.

The role of orthopedic screws threads properties on the success of femoral fracture fixation

Stress shielding is created following a reduction in bone density due to the reduction or elimination of mechanical stimuli and the resultant stresses around the implant site in bone tissue. Increased stress shielding can cause the implant or screw to detach or loosen over time, which in turn can lead to severe side effects such as pain, infection, necrosis, and dysfunction. The geometric shape and characteristics of the screws are among the most important factors involved in creating the stress shielding. Hence, the current study aimed to evaluate the influence of bone screw design parameters (i.e., thread profile, thread pitch, screw diameter, and elastic modulus) on stress shielding around the standard screws after implantation in the proximal femur using a viscoelastic finite element modelling. Stress transfer parameters (STP) and strain energy density transfer parameters (SEDTP) were used to evaluate the stress shielding and the risk of screw loosening using the finite element method. This study was performed on screws with titanium and beta-titanium alloy materials as well as HB, HC, and HD ISO threads that are considered as implants for fracture fixation. The results indicated that the HB ISO thread has the least stress shielding and looseness. It was also found that reducing the modulus of elasticity of the screws, increasing the number of threads per screw, reducing the pitch of the screws and the diameter of the screws shaft reduce the amount of the stress shielding and loosening of the screws. This study can provide surgeons with valuable quantitative data for selecting the effective types of screws for bone fracture fixations towards enhanced clinical outcomes.

Keyhole Sliding Hip Screw Fixation for Stable Intertrochanteric Hip Fractures: A Novel Technique.

Intertrochanteric hip fractures are common orthopaedic injuries and the incidence is growing with increasing life expectancy. Several randomized controlled studies have shown the advantages of intramedullary devices over hip screw fixation in unstable intertrochanteric fractures. However, the proven advantage of the intramedullary device in stable intertrochanteric fractures, OTA (Orthopaedic Trauma Association) classification 31-A1 and some 31-A2 fractures are in less blood loss compared with standard hip screw fixation. In the current technical note, we describe a novel minimally invasive technique of hip screw fixation that use a keyhole size incision to fix stable intertrochanteric fractures using sliding hip screw. The less invasive nature and potentially reduced blood loss makes this technique an attractive option for stabilizing stable intertrochanteric hip fractures.

357 Novel Osteoconductive, Bioresorbable Bone Adhesive Provides Superior Cranial Flap Fixation Strength and Reduced CSF Leak Potential in a Cadaver Model

INTRODUCTION: Plates and screws are the gold standard for cranial flap fixation. Unfortunately, hardware may be associated with loosening and migration. Osseous union of the fixated flap to the surrounding skull is typically incomplete. Furthermore, titanium plates and screws do not provide a watertight closure of the bone and cannot mitigate CSF leakage. METHODS: 64 craniotomies were performed in 16 cadavers by a single neurosurgeon. Frontal, pterional, parietal, and parieto-occipito-temporal flaps were created in each skull. The 64 bone flaps were fixated by 16 different neurosurgeons (4 flaps/surgeon). Each flap was secured with standard cranial plates and screws, then biomechanically tested using either quasi-static compression (1mm/min) or staircase impact (up to 60J impact energy at increments of 6J) to analyze mechanical strength. Next, the plates and screws were removed and the same bone flap was secured by the same neurosurgeon using a novel bone adhesive, Tetranite®(TN). The TN-secured flaps were then biomechanically tested in similar fashion. A subset of the TN-fixated flaps was subjected to hydrostatic fluid pressure (up to 40mm Hg at steps of 5mm Hg) to determine resistance to simulated CSF leakage prior to mechanical testing. RESULTS: TN fixation was approximately 41 times stiffer and 48 times stronger than metal fixation under quasi-static loading (stiffness 4216±1544N/mm and peak force 5456±1920N for TN vs. 103 ±81N/mm and 113±89N for metal hardware: n=32). At an impact energy of 6J, cranial flaps fixated using metal hardware migrated to a peak deflection 13 times greater than TN-fixated specimens; the residual plastic deformation was 30 times greater (peak elastic deflection 2.94± 0.81mm and plastic deflection of 1.69±0.93mm for metal hardware vs. 0.24±0.07mm and 0.06±0.04mm for TN; n=31). Of 16 TN-fixated specimens tested hydrostatically, none leaked under pressures up to 35mmHg held for 5 secs, and only 2 specimens leaked at 40mmHg. CONCLUSION: TN was biomechanically superior to standard cranial hardware for flap fixation. Additionally, TN acted to prevent fluid leakage. TN holds promise for improving cranial bone flap fixation biomechanically, cosmetically, and hydrostatically.

Improved fixation stability for repairing pedicle screw loosening using a modified cement filling technique in porcine vertebrae

Polymethylmethacrylate (PMMA) has been applied clinically and biomechanically repair loose pedicle screws. Controversies have arisen over data due to uncontrolled cement properties, various locations and sizes of fenestrated holes in repair screws, irregular holes and different bone densities of specimens. In this study, the pullout strength was compared for two techniques, the modified technique to use PMMA to augment a threaded hole and the traditional technique with retrograde injection of a PMMA filling, for standard loose screws in porcine vertebrae. Both techniques provided statistically significant results for sufficiently randomized specimens and experimental procedures. The difference in the pullout strength between conical and cylindrical screws for the aforementioned cement augmentation techniques was also investigated. Twenty-four single-level fresh-frozen lumbar vertebrae from L1 to L6 were harvested from four mature pigs. A total of 0.8 ml of PMMA was retrograde injected into screw holes with a 5.5 mm diameter, followed by insertion of a 5.0 mm diameter repair screw in the traditional group (n = 12). A stiff threaded PMMA hole was created with a 4.5 mm tapping screw before insertion of repair screws in the modified group (n = 12). Two screw geometries were randomly assigned as cylindrical (n = 6) and conical (n = 6) in each group. The correlations between filling techniques, screw geometries and axial pullout strength were analyzed. An appropriate screw trajectory and insertion depth were confirmed using X-ray imaging prior to pullout testing in both groups. For a given screw geometry (cylindrical or conical), the pullout force of the modified group was significantly higher than that of the traditional group. There was no significant difference in the pullout force between the screw geometries for a given filling technique. The cement augmentation technique is far more influential than the screw outer geometry. The modified PMMA technique created a greater anchor force than the traditional method and could be an alternative for revision of pedicle screw loosening.

Functionalization of screw implants with superelastic structured Nitinol anchoring elements

BackgroundDemographic change is leading to an increase in the number of osteoporotic patients, so a rethink is required in implantology in order to be able to guarantee adequate anchoring stability in the bone. The functional modification of conventional standard screw implants using superelastic, structured Ti6Al4V anchoring elements promises great potential for increasing anchoring stability.MethodsFor this purpose, conventional screw implants were mechanically machined and extended so that structured-superelastic-positionable-Ti6Al4V anchoring elements could be used. The novel implants were investigated with three tests. The setup of the anchoring elements was investigated in CT studies in an artificial bone. In a subsequent simplified handling test, the handling of the functional samples was evaluated under surgical conditions. The anchorage stability compared to standard screw implants was investigated in a final pullout test according to ASTM F543—the international for the standard specification and test methods for metallic medical bone screws.ResultsThe functionalization of conventional screw implants with structured superelastic Ti6Al4V anchoring elements is technically realizable. It was demonstrated that the anchoring elements can be set up in the artificial bone without any problems. The anchorage mechanism is easy to handle under operating conditions. The first simplified handling test showed that at the current point of the investigations, the anchoring elements have no negative influence on the surgical procedure (especially under the focus of screw implantation). Compared to conventional standard screws, more mechanical work is required to remove the functional patterns completely from the bone.ConclusionIn summary, it was shown that conventional standard screw implants can be functionalized with Ti6Al4V-structured NiTi anchoring elements and the new type of screws are suitable for orthopedic and neurosurgical use. A first biomechanical test showed that the anchoring stability could be increased by the anchoring elements.

Опыт применения биодеградируемых имплантов на основе магния при хирургическом лечении вальгусной деформации первого пальца стопы методикой mini-Scarf

The use of biodegradable implants is becoming increasingly popular, especially in operations on small bones of the skeleton, including operations on the anterior part of the foot. 23 surgical interventions were performed to correct the first metatarsal using the mini-Scarf technique and fixation of fragments with a biodegradable implant. All the operated patients did not have a severe radiological stage of osteoarthritis of the first metatarsophalangeal joint and stiffness. The results of treatment were evaluated using AOFAS and Groulier questionnaires. Out of 23 patients, it was possible to track and obtain data according to the questionnaires in 18 patients (78.3% (16 had grade III deformity (88.9%)). Six months after surgical treatment, the proportion of excellent and good results was 77.8% (14) according to the AOFAS questionnaire and 83.3% (15) according to the Groulier questionnaire. The achieved results suggest a favorable prognosis for the widespread use of magnesium oxide implants, however, further research and comparison of the results of treatment in patients with hallux valgus who underwent surgery with the use of standard titanium screws are needed.

An Oblique Trans-Syndesmotic Screw to Augment Fixation of Distal Fibula Fractures: A Technique Guide

Category:Trauma; AnkleIntroduction/Purpose:A subset of patients with low, transverse fractures of the lateral malleolus are at increased risk of malreduction and late loss of reduction. In patients with poor bone quality and transverse or short oblique fractures at or distal to the tibiotalar joint, distal fixation is often inadequate with a single interfragmentary lag screw. Furthermore, these fractures are susceptible to malreduction by pre-contoured locking plates. To address this, a technique was developed to augment fixation of the distal fragment and decrease the likelihood of loss of reduction. The senior author's technique for this procedure, as well as indications for the technique and a few representative cases, are provided.Methods:This technique involves placement of an oblique tricortical or quadricortical screw from the distal fibula into the tibia in an distal-lateral to proximal-medial direction. The screw is placed either outside of or through the distal-most hole of a one-third tubular plate placed in a neutralization position. The screw trajectory is similar to that of a typical syndesmosis screw in the sagittal plane but is aimed proximally rather than parallel to the tibial plafond. The screw enters the tibia at Chaput's tubercle, just lateral to the joint. The indications for this technique are transverse and short oblique Danis-Weber B distal fibular fractures in which there is inadequate purchase between the plate and the distal fragment. While the purpose of this screw is not to stabilize the syndesmosis, it can be used with other augmentation techniques, such as trans-syndesmotic screws, in high-risk patients with osteoporosis and/or neuropathy.Results:This technique has been used for many years by the senior author. There have been no implant failures (e.g. broken screws) or major complications associated with this technique. Three representative cases demonstrate appropriate indications and outcomes for this technique. These include patients with significant neuropathy or osteoporosis who present with a particularly troublesome fracture pattern (transverse fibular fracture at or below the level of the tibiotalar joint). This screw, along with any other syndesmotic screws, is removed at 3-4 months according to the senior author's protocol.Conclusion:A distal oblique trans-syndesmotic screw can be used to supplement current fibular fracture fixation constructs. It is easy to place under fluoroscopic guidance and generally is removed after fracture union, similar to standard syndesmosis screws. The use of this screw helps prevent the malreduction that can potentially occur when treating transverse or short-oblique Weber B distal fibular fractures with a locking plate. In our series of patients at a large urban tertiary referral center, this technique has produced good outcomes with no reportable complications.

Comparison of Mechanical Resistance to Maximal Torsion Stress in Original and Nonoriginal or Compatible Prosthetic Implant Screws: An In Vitro Study.

Micromovements of the implant-abutment connection influence peri-implant bone preservation. The maximal torque after a cycle of implant prosthetic screw tightening using original components of different manufacturers and replicas produced by other companies is evaluated and quantified in this study. A total of 30 Mis Seven® standard platform implants and 30 interfaces were used, and 30 standard platform screws were tested, 10 Mis®, 10 Iconekt®, and 10 Exaktus®. The screws were tightened with an MIS® torquemeter until their respective fracture, and the fracture point was measured through the equipment's load cell, CS-Dental Testing Machine®. The screws were analyzed under an Olympus® SZ61 microscope. The fracture points were recorded and compared among all samples. To compare the mean values of the fracture torques, t-tests were performed using the reference values associated with each brand and the sample results. The variable “Place of Fracture” between the original Mis® brand and the Exaktus® replica compared to the Iconekt® replica presented a statistically significant difference (p < 0.001). When analyzing the variable “Fracture Torque,” although it was verified that the replica screws (Iconekt® and Exaktus®) had a lower maximum torque, 65.11 Nm and 62.89 Nm, respectively, compared to the original Mis® brand (70 Nm and 69 Nm), there were no statistically significant differences p > 0.05. Nonoriginal screws did not present different fracture resistances compared to the original Mis® brand screws. The fracture site of Iconekt® screws showed a different pattern compared to the other brands.

Cervical lateral mass screw length analysis in men versus women.

Posterior fixations with lateral mass screws have become popular. The Roy-Camille and the Magerl techniques have been established and screw length was identified as a particularly important element. Sex and ethnicity are significant factors in cervical spine morphology, but few studies have been performed for screw length. We performed measurements using computed tomography (CT) images of adult patients hospitalized for surgery of the cervical spine, with targeted 3D data analysis. The final number of patients was 47 (33 men, 14 women) and 235 vertebrae. With the Roy-Camille technique, the screw length was longest at C3 (men: 13.0 mm ± 1.9 mm, women: 13.0 mm ± 1.9 mm) and smallest at C7 (men: 10.8 mm ± 1.8 mm, women: 9.4 mm ± 1.2 mm). With the Magerl technique, the screw length was smallest at C3 (men: 14.8 mm ± 1.6 mm, women: 14.3 mm ± 1.6 mm) and longest at C7 for men (16.8 mm ± 2.8 mm), and at C6 for women (15.4 mm ± 3.0 mm). To differ from spinal canal or pedicle, cervical lateral mass showed no obvious morphological differences from that of subjects of other ethnicity. The placement of a standard lateral mass screw would not cause complications in Japanese patients, even with the use of devices designed in North America or Europe. However, the anatomical background is essential because it is important to optimize the selection for each patient to avoid complications considering sex and individual differences.

Suture Tape Augmentation of Screw Fixation Reduces Fragment Migration in Tibial Tubercle Osteotomy: A Biomechanical Study.

Background:Tibial tubercle osteotomy (TTO) is a complex surgical procedure with a significant risk of complications, which include nonunion and tibial fracture.Purpose:To determine whether an additional suture tape augmentation can provide better biomechanical stability compared with standard screw fixation.Study Design:Controlled laboratory study.Methods:Five matched pairs of human cadaveric knees were divided into 2 groups: the first group underwent standard TTO fixation with 2 parallel screws (standard group). The second group underwent a novel fixation technique, in which a nonabsorbable suture tape (FiberTape) in a figure-of-8 construct was added to the standard screw fixation for extra stabilization in the inferior-superior direction (augmented group). The specimens were biomechanically tested using a multistep cyclic loading protocol from 400 N up to 800 N to simulate the rehabilitation process. Tubercular fragment migration of >50% of the initial distalization length was defined as clinical failure. A pull-to-failure test was applied to the specimens that survived cyclic loading. Tubercular fragment displacement during cyclic loading and pull-to-failure force were recorded and compared between the 2 groups.Results:Two specimens of the standard group exhibited clinical failure during cyclic loading to 400 N. All other specimens survived cyclic loading to 800 N. The augmented group showed less cyclic tubercular fragment displacement after every load level compared with the standard group, with statistically significant differences starting from 500 N (P < .05; power > 0.8). Mean ± standard deviation tubercular fragment displacement at the end of cyclic loading was 2.56 ± 0.82 mm for the augmented group and 5.21 ± 0.51 mm for the standard group. Mean ultimate failure load after the pull-to-failure test was 2475 ± 554 N for the augmented group and 1475 ± 280 N for the standard group.Conclusion:The specimens that underwent suture tape augmentation showed less tubercular fragment displacement during cyclic loading and higher ultimate failure forces compared with those that underwent standard screw fixation.Clinical Relevance:The augmentation technique could potentially increase the success of a TTO.

Preparation and In Vitro/In Vivo Evaluation of Orally Disintegrating/Modified-Release Praziquantel Tablets.

This study was designed to develop orally disintegrating/sustained-release praziquantel (PZQ) tablets using the hot-melt extrusion (HME) technique and direct compression, and subsequently evaluate their release in in vitro and in vivo pharmacokinetics. For the extrusion process, hypromellose acetate succinate (HPMCAS)-LG was the carrier of pure PZQ, with a standard screw configuration used at an extrusion temperature of 140 °C and a screw rotation speed of 100 rpm. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) and Fourier-transform infrared spectroscopy (FTIR) were performed to characterize the extrudate. Orally disintegrating/sustained-release praziquantel tablets (PZQ ODSRTs) were prepared by direct compression after appropriate excipients were blended with the extrudate. The release amount was 5.10% in pH 1.0 hydrochloric acid at 2 h and over 90% in phosphoric acid buffer at 45 min, indicating the enteric-coating character of PZQ ODSRTs. Compared with the pharmacokinetics of marketed PZQ tablets (Aipuruike®) in dogs, the times to peak (Tmax), elimination half-life (t1/2λ) and mean residence time (MRT) were extended in PZQ ODSRTs, and the relative bioavailability of PZQ ODSRTs was up to 184.48% of that of Aipuruike®. This study suggested that PZQ ODSRTs may have potential for the clinical treatment of parasitosis.

Évaluation des performances de réduction et de fixation d’une nouvelle technique de fusion lombaire instrumentée utilisant des vis de réglage : étude biomécanique

BackgroundInstrumented posterior lumbar fusion with top-loading pedicle screw systems (PSS) requires fully tightened set screws to achieve a secure fixation and symmetric load condition. This assumes a complete reduction of the rod by 90°, which is not always attainable in situ, especially under constraint. The objective of this work is to compare the mechanical performance of different innovative set screw technologies, which should improve the tightening process. HypothesisThe hypotheses of the study are that modifications to the screw and screwdriver unit can (1) improve the quality of set screw tightening and (2) increase the axial gripping capacity of the construct. Materials and MethodsThe four set screw technologies under investigation include a standard set screw with a flat surface (F-S; control group), a set screw with a convex surface (C-S) and a shaft tip method screwdriver used in combination with both flat (F-STM) and convex set screws (C-STM). The quality of set screw tightening is categorized as follows: failed=the rod is not completely reduced; reduced=the rod is successfully reduced but the set screw is not correctly fixed; good=remaining cases. An axial gripping capacity test is performed by a universal testing machine (Instron®) with a force capacity of 5kN. ResultsRegarding the quality of set screw tightening, comparisons between F-S vs. F-STM, F-S vs. C-STM and between C-S vs. C-STM show statistically significant differences (p<0.001). The axial gripping capacity test shows mean gripping forces of 1223N (STD 331) in the F-STM group and of 1724N (STD 168) in the C-STM group with statistically significant differences between both groups (p=0.003). DiscussionSeveral biomechanical and clinical case studies have identified possible effects of misaligned rod-screw interfaces such as screw pull-out during rod reduction, screw loosening, screw or rod breakage, misalignment, adjacent segment degeneration and worsening of the clinical outcome. C-STM-technology thus supports controlled fixation in the sense of applying appropriate forces for correction or fixation during PSS assembly as well as friction-reduced final alignment and tightening with the aim to reduce implant loosening, hardware failure and reoperations, while respecting anatomical and biomechanical balance.

Additional use of anti-rotation U-blade (RC) decreases lag screw sliding and limb length inequality in the treatment of intertrochanteric fractures

The purpose of this study is to compare the cut-out rate and sliding distance associated with limb length inequality between operations using a standard non-sliding lag screw versus those using a non-sliding lag screw with U-blade (RC) in the Gamma3 nail. This is a retrospective review of two case series involving different lag screws for the Gamma3 nail. Propensity score matching analysis was used to adjust the confounding factors. A comparative analysis of 304 patients who treated with Gamma3 nail with either a standard non-sliding lag screw or a U-Blade (RC) lag screw was performed. Between 2014 and 2018, 152 patients were treated with U-blade (RC) lag screws, and these patients were matched with those treated with standard lag screws. There was no significant difference in cut-out rate between groups. However, additional use of anti-rotation U-blade (RC) could significantly decrease lag screw sliding, with the group treated with U-Blade (RC) lag screws exhibiting shorter sliding, especially in AO/OTA31 A2 and A3 fractures. Also, in A2 and A3 fractures, the mean lag screw sliding distance was greater than that seen in A1 fractures in both groups. These findings can help trauma surgeons choose the proper implant to reduce leg length inequality.

Patient-specific template-guided versus standard freehand lumbar pedicle screw implantation: a randomized controlled trial.

Patient-specific template-guided (TG) pedicle screw placement currently achieves the highest reported accuracy in cadaveric and early clinical studies, with reports of reduced use of radiation and less surgical time. However, a clinical randomized controlled trial (RCT) eliminating potential biases is lacking. This study compares TG and standard freehand (FH) pedicle screw insertion techniques in an RCT. Twenty-four patients (mean age 64 years, 9 men and 15 women) scheduled consecutively and independently from this study for 1-, 2-, or 3-level lumbar fusion were randomized to either the FH (n = 12) or TG (n = 12) group. Accuracy of pedicle screw placement, intraoperative parameters, and short-term complications were compared. A total of 112 screws (58 FH and 54 TG screws) were implanted in the lumbar spine. Radiation exposure was significantly less in the TG group (78.0 ± 46.3 cGycm2) compared with the FH group (234.1 ± 138.1 cGycm2, p = 0.001). There were 4 pedicle screw perforations (6.9%) in the FH group and 2 (3.7%) in the TG group (p > 0.99), with no clinical consequences. Clinically relevant complications were 1 postoperative pedicle fracture in the FH group (p > 0.99), 1 infection in the FH group, and 2 infections in the TG group (p > 0.99). There were no significant differences in surgical exposure time, screw insertion time, overall surgical time, or blood loss between the FH and TG groups. In this RCT, patient-specific TG pedicle screw insertion in the lumbar region achieved a high accuracy, but not better than a standardized FH technique. Even if intraoperative radiation exposure is less with the TG technique, the need for a preoperative CT scan counterbalances this advantage. However, more difficult trajectories might reveal potential benefits of the TG technique and need further research.

Bone density optimized pedicle screw instrumentation improves screw pull-out force in lumbar vertebrae

Pedicle screw instrumentation is performed in the surgical treatment of a wide variety of spinal pathologies. A common postoperative complication associated with this procedure is screw loosening. It has been shown that patient-specific screw fixation can be automated to match standard clinical practice and that failure can be estimated preoperatively using computed tomography images. Hence, we set out to optimize three-dimensional preoperative planning to achieve more mechanically robust screw purchase allowing deviation from intuitive, standard screw parameters. Toward this purpose, we employed a genetic algorithm optimization to find optimal screw sizes and trajectories by maximizing the CT derived bone mechanical properties. The method was tested on cadaveric lumbar vertebrae (L1 to L5) of four human spines (2 female/2 male; age range 60–78 years). The main boundary conditions were the predefined, level-dependent areas of possible screw entry points, as well as the automatically located pedicle structures. Finite element analysis was used to compare the genetic algorithm output to standard clinical planning of screw positioning in terms of the simulated pull-out strength. The genetic algorithm optimization successfully found screw sizes and trajectories that maximize the sum of the Young’s modulus within the screw’s volume for all 40 pedicle screws included in this study. Overall, there was a 26% increase in simulated pull-out strength for optimized compared to traditional screw trajectories and sizes. Our results indicate that optimizing pedicle screw instrumentation in lumbar vertebrae based on bone quality measures improves screw purchase as compared to traditional instrumentation.