Monocortical Screws Research Articles

Effect of screw type and distribution on the torsional stability of 3.5 mm string of pearls locking plate constructs.

To evaluate the effects of screw type (mono- [M] versus bicortical [B]), number, and position on torsional stability of String of Pearls (SOP) locking plate constructs. In vitro mechanical study. SOP plates (n = 32) were applied to bone models and divided into 8 groups named according to screw type (M or B) and position in each fragment relative to the fracture gap starting at the outermost plate hole. Positive and negative controls were MMM and BBB, respectively. Specimens were non-destructively tested in torsion. Compliance and angular deformation were statistically compared (P < .002). The MMM construct was most compliant (P < .001). Compliance decreased in groups with a single bicortical screw (P < .001). Compared to the MMM group, torsional compliance decreased in constructs where a single monocortical screw was replaced with a bicortical screw (P < .001). Compared with a centrally positioned bicortical screw, constructs with a bicortical screw in either outer- or innermost position were 15% and 23% less compliant, respectively (P < .001). Addition of a second bicortical screw/fragment further decreased compliance (P < .001). No significant difference was found between groups with 2 bicortical screws. The BBB construct was least compliant (P < .001). Group responses for angular deformation followed the same pattern of significance recorded for compliance. A minimum of 1 bicortical screw/fragment should be used to increase torsional stability of 3.5 mm SOP constructs. Positioning this screw at the inner- or outermost positions relative to the fracture is preferred, with the innermost position providing the greatest improvement in stability. Should further torsional stability be desired, increasing the number of bicortical screws is recommended. Clinically, these results may assist with preoperative planning of various fracture patterns.

A CBCT measurement of the mandibular buccal bone thickness in dentate adults

AbstractAimThis study aims to measure the mandibular cortical bone thickness and the proximity of the tooth roots and the inferior alveolar canal to the outer cortex using cone‐beam computed tomography (CBCT).Materials and methodsEighty CBCT scans were analysed. Buccal cortical plate and trabecular bone thickness were measured. Measurements of canine, first premolar, second premolar, first molar and second molar regions were taken at following levels: cortical plate thickness at the level of the midpoint of the midapical third of the root and at the level of apex, cortical plate and trabecular bone thickness at the level of the midpoint of the midapical third of the root, at the level of apex and at the level of inferior alveolar canal.ResultsCortical bone thickness was greatest at the second molar region with 2.66 ± 0.72 at the root's midapical third, 3.27 ± 0.52 at the apex and 3.12 ± 0.64 at the level of the canal. Cortical plate and trabecular bone thickness was greatest at the second molar region with 4.72 ± 0.86 at the midapical third, 6.49 ± 0.8 at the apex and 5.3 ± 0.6 at the level of the canal.ConclusionsThickness of the outer cortex as well as the distance from cortex to canal and root is greatest at the second molar region, allowing placement of 4 mm monocortical screws safely and providing better implant stability and a thicker bone graft.

Comparison of lower lip hypoesthesia between hybrid fixation and conventional fixation following sagittal split ramus osteotomy

PurposeThe purpose of this study was to compare the recovery period of lower lip hypoesthesia between hybrid fixation and conventional fixation using absorbable plates and screw systems following sagittal split ramus osteotomy (SSRO). Subjects and methodsThe subjects were 66 patients (132 sides) who underwent bilateral SSRO setback surgery. They were divided into a hybrid fixation group (66 sides, 1 u-HA/PLLA plate and 4 mono-cortical screws and a bi-cortical screw in each side) and a conventional fixation group (66 sides, 1 u-HA/PLLA plate and 4 mono-cortical screws in each side). Trigeminal nerve hypoesthesia at the region of the lower lip was assessed bilaterally by the trigeminal somatosensory-evoked potential (TSEP) method. ResultsThe mean measurable periods were 8.1 ± 10.4 weeks in the hybrid fixation group, 5.1 ± 11.5 weeks in the conventional group with no significant difference. However, the maximum in the hybrid fixation group was 27 sides at 4 weeks postoperative and in the conventional fixation group was 37 sides at 1 week postoperative, and there was significant difference in the distribution of the measurable period (P < 0.0001). ConclusionThis study suggested that additional bi-cortical screws could affect the recovery of lower lip hypoesthesia after SSRO with bent absorbable plate fixation.

Use of bioresorbable plating systems in paediatric mandible fractures

AimThe aim of this study is to retrospectively evaluate the use of bioresorbable plating systems in the rigid fixation of paediatric mandible fractures. Patients and methodsOur series consists of fifteen paediatric patients (11 male, 4 female, average age 8.13 years) with mandible fractures of varying severity treated with bioresorbable plates over a 54-month period at our institution. Fractures of the ramus, body, parasymphysis, and symphysis were treated by one surgeon with open reduction and internal fixation with 1.5 mm and 2 mm resorbable plates and monocortical screws, using 3 different plating systems, each with differing polymer concentrations of polyglycolic and poly-l-lactic acid. The patients were followed with respect to the following clinical categories: fracture location, postoperative occlusion, maximum interincisal opening (MIO), segmental mobility at the fracture site, and any abnormal swelling at the operative site. ResultsOur data shows a stable occlusion and maximum interincisal opening of thirty millimetres or greater was achieved in 14 of 15 patients seen in follow up, with 8 patients having an MIO of 40 mm or greater. No segmental mobility noted at any of the fracture sites. Thirteen patients had no postoperative sequelae or implant related complications. Two patients developed a seroma-like collection at the operative site. Postoperative films starting at 1 year showed significant bony osseous fill where the previous screw sites were located. ConclusionsIn our case series we found that the use of resorbable polyglycolic and poly-l-lactic acid plating systems when combined with a brief postoperative period of intermaxillary fixation is an effective method of internal fixation for mandibular fractures in the paediatric population.

Skeletal Stability after Bilateral Sagittal Split Advancement and Setback Osteotomy of the Mandible with Miniplate Fixation

The purpose of this study was to evaluate intraorally placed mini plates and monocortical screws in terms of postoperative skeletal stability after bilateral sagittal split advancement and setback osteotomy of the mandible. Ten patients were included in this study with five requiring advancement (group I) and five requiring setback of the mandible (group II). Bell and Epker modified surgical technique was followed for all the patients. All the patients underwent pre- and postsurgical orthodontics. Cephalometric radiographs were taken preoperatively, immediate, 3, 6, and 12 months postoperatively. Cephalometric tracings were performed by one individual examiner using a modified burstone analysis. Statistical analysis was performed using the student paired t-test. In advancement patients, SNB (sella, Nasion, B point) angle showed relapse at 12th month postoperative period which was statistically significant (2.4 degrees). No changes were observed in anterior facial height, posterior facial height, Frankfort-mandibular incisor angle (FmiA), and overjet during the follow-up period. In setback patients, posterior facial height (p < 0.05), angles between the lower incisors and mandibular plane and pogonion had a statistically significant change position of 1.4 mm (paired t-test, p = 0.03). The SNB angle, anterior facial height, interincisal angle, and FmiA remained constant (0.8-1.2 degrees) during the follow-up period. In advancement cases, the relapse was seen from the third month postoperative period but in setback cases, the relapse was noted from the sixth month onward and the skeletal relapse in these cases were noticed cephalometrically.

A biomechanical comparison of unilateral and bilateral String-of-Pearls™ locking plates in a canine distal humeral metaphyseal gap model.

To compare the in vitro biomechanical performance of two String-of-Pearls (SOP) plate constructs in a canine distal humeral metaphyseal gap model. Seven pairs of canine cadaveric humeri, including the elbow joints, were prepared. One group consisted of a unilateral medially placed SOP plate with bicortical screws (UNI). The second group consisted of bilateral caudo-medial and caudo-lateral SOP plates applied with monocortical screws (BI). A 2 cm ostectomy was performed immediately proximal to the supratrochlear foramen. Constructs were tested in torsion and axial compression. The UNI constructs had significantly lower stiffness in torsion and axial compression than the BI group. However, UNI constructs had a significantly higher ultimate strength than BI constructs. All UNI constructs failed by bending of the transcondylar screw and SOP plate. All BI constructs failed by axial pullout of the distal most screws. In stabilizing canine supracondylar humeral fractures as modeled here, both the UNI model and the BI model demonstrated biomechanical advantages. The incorporation of a transcondylar screw through the medial plate appears to be beneficial to construct strength.

Biomechanical analysis of the efficacy of locking plates during cyclic loading in metacarpal fractures.

Purpose. To analyse the biomechanical characteristics of locking plates under cyclic loading compared to a nonlocking plate in a diaphyseal metacarpal fracture. Methods. Oblique diaphyseal shaft fractures in porcine metacarpal bones were created in a biomechanical fracture model. An anatomical reduction and stabilization with a nonlocking and a comparable locking plate in mono- or bicortical screw fixation followed. Under cyclic loading, the displacement, and in subsequent load-to-failure tests, the maximum load and stiffness were measured. Results. For the monocortical screw fixation of the locking plate, a similar displacement, maximum load, and stiffness could be demonstrated compared to the bicortical screw fixation of the nonlocking plate. Conclusions. Locking plates in monocortical configuration may function as a useful alternative to the currently common treatment with bicortical fixations. Thereby, irritation of the flexor tendons would be avoided without compromising the stability, thus enabling the necessary early functional rehabilitation.

The biomechanical aspects of reconstruction for segmental defects of the mandible: A finite element study to assess the optimisation of plate and screw factors

A bone plate is required to restore the load-bearing capacity of the mandible following a segmental resection. A good understanding of the underlying principles is crucial for developing a reliable reconstruction. A finite element analysis (FEA) technique has been developed to study the biomechanics of the clinical scenarios managed after surgical resection of a tumour or severe trauma to assist in choosing the optimal hardware elements.A computer aided design (CAD) model of an edentulous human mandible was created. Then 4 common segmental defects were simulated. A single reconstruction plate was designed to span the defects. The hardware variations studied were: monocortical or bicortical screw fixation and non-locking or locking plate design. A standardized load was applied to mimic the human bite. The von Mises stress and strain, spatial changes at the screw-bone interfaces were analysed.In general, the locking plate and monocortical screw fixation systems were most effective. Non-locking plating systems produced larger screw “pull-out” displacements, especially at the hemimandible (up to 5% strain). Three screws on either side of the defect were adequate for all scenarios except extensive unilateral defects when additional screws and an increased screw diameter are recommended. The simplification of screw geometry may underestimate stress levels and factors such as poor adaptation of the plate or reduced bone quality are likely to be indications for bicortical locking screw fixation.The current model provides a good basis for understanding the complex biomechanics and developing future refinements in plate or scaffold design.

A biomechanical study on proximal plate fixation techniques in periprosthetic femur fractures

IntroductionProximal plate fixation is a crucial factor in osteosynthesis of periprosthetic femur fractures. Stability and strength of different fixation concepts for proximal plate fixation were compared. Materials and methodsTwelve fresh frozen, bone mineral density matched human femora, instrumented with cemented hip endoprosthesis were osteotomized simulating a Vancouver B1 fracture. Specimens were instrumented with locking compression plates, fixed proximally with either locking attachment plate (LAP), monocortical screws, cerclage plus monocortical screws (1cerclage) or cerclages only (4cerclages). Cyclic testing was performed with monotonically increasing load until failure. Relative movements at the proximal plate–femur interface were registered by motion tracking. ResultsThe LAP construct exhibited a significantly longer cumulative survival (failure criterion 1mm separation at the proximal plate fixation) compared to the monocortical (p=0.048) and 4cerclages constructs (p=0.012) but not to 1cerclage constructs. ConclusionBicortical screw anchorage improves proximal plate fixation in periprosthetic fractures. The cerclage–screw combination is a valuable alternative especially in osteoporotic bone.

In vitro resistance of titanium and resorbable (poly l-co-dl lactic acid) osteosynthesis in mandibular body fracture

This study was a comparative evaluation of the bending resistance of metallic and resorbable plates and screws in a mandibular body fracture model. Forty polyurethane synthetic hemimandibles were used; a vertical linear cut was made between the second and first premolars. These 40 hemimandibles were divided into four groups of 10 and were fixed with titanium plates and screws or resorbable plates and screws, with monocortical screws in the upper sector and bicortical screws in the lower sector. Bending resistance tests were done on a universal testing machine with a linear displacement speed of 1mm/min, a cell load of 500N, and a load cell on the lower central incisor or on the lower second premolar. Results were analyzed using the Student's t-test, with the significance level set at 5%. No statistically significant differences were observed between the groups studied, either in the analysis of the osteosynthesis materials or related to the load-bearing points. The variables of displacement and peak load did not present any significant differences. In this in vitro model of a mandibular body fracture, the mechanical behaviour of a resorbable osteosynthesis was similar to that of a titanium osteosynthesis.

A new ‘k’ shaped miniplate design for mandible angle fractures—mechanical test study

The aim of this study was to evaluate the efficiency of new titanium miniplate design (Modified Champy) resistance against the mechanical forces in mandible angle fracture. Thirty fresh sheep hemimandibles were assigned into three major (n=10) and two subgroups (n=5) and sectioned in the mandibular angle region to simulate the fracture. The bone segments fixed by 6 holes 2.0mm non-compresion titanium miniplate via champy method and 6 holes 2.0mm ‘k’ shaped titanium miniplate with 2.0mm×6mm monocortical screws.

Mandibular Fractures Treated With Small Plates and Screws Reduce Treatment Cost

The efficacy of treating mandibular fractures with open reduction and internal fixation (ORIF) using small titanium plates and monocortical screws is well established. The purpose of this study was to determine whether the use of semirigid (small) titanium plates results in lower treatment charges. Consecutive patients with mandibular fractures were randomly allocated to ORIF with small or large titanium plates. The primary predictor variable for this secondary subset analysis was plate size. The primary outcome variable was total treatment charges. Other outcomes included length of stay (LOS), operating room charges, hardware charges, LOS charge, and charges related to the treatment of complications. A total of 127 consecutive patients were enrolled in the study. Fifty-two patients completed the required 6-week follow-up and had data available for analysis. Adjusted total treatment charges suggested a significant difference, with a mean total treatment charge of $15,308 in the semirigid group and a mean total treatment charge of $16,557 in the rigid group (P = .04). Total treatment charges were 8% higher in the rigid group compared with the semirigid group. The findings of this study suggest that the overall charges associated with treating mandibular fractures with ORIF are significantly lower when semirigid plates are used.

Impairment of wound healing after operative treatment of mandibular fractures, and the influence of dexamethasone

Our aim was to clarify the incidence of impaired wound healing after open reduction and ostheosynthesis of mandibular fractures, and to find out whether the use of dexamethasone during the operation increased the risk. Patients were drawn from a larger group of healthy adult dentate patients who had participated in a single-blind, randomised study, the aim of which was to clarify the benefits of operative dexamethasone after treatment of facial fractures. The present analysis comprised 41 patients who had had open reduction and fixation of mandibular fractures with titanium miniplates and monocortical screws through one or 2 intraoral approaches. The outcome variable was impaired healing of the wound. The primary predictive variable was the perioperative use of dexamethasone; other potential predictive variables were age, sex, smoking habit, type of fracture, delay in treatment, and duration of operation. Wound healing was impaired in 13/41 patients (32%) (13/53 of all fractures). The incidence among patients who were given dexamethasone and those who were not did not differ significantly. Only age over 25 was significantly associated with delayed healing (p=0.02). The use of dexamethasone 30mg perioperatively did not significantly increase the risk of impaired wound healing in healthy patients with clinically uninfected mandibular fractures fixed with titanium miniplates through an intraoral approach. Older age is a significant predictor of impaired healing, which emphasises the importance of thorough anti-infective care in these patients during and after the operation.

Mechanical behavior of fixation components for periprosthetic fracture surgery

BackgroundReliable periprosthetic fracture treatment needs detailed knowledge on the mechanical behavior of the fixation components used. The holding capacity of three conventional fixation components for periprosthetic fracture treatment was systematically investigated under different loading directions. MethodsLocking compression plates were fixed to a 7cm long part of diaphyseal fresh frozen human femur with either a single 1.7mm cerclage cable, a 5.0mm monocortical or a bicortical locking screw (n=5 per group). Constructs were loaded in lateral, torsional and axial direction with respect to the bone axis in a load-to-failure test. Corresponding stress distribution around the screw holes was analyzed by finite element modeling. FindingsBoth screw fixations revealed significantly higher stiffness and ultimate strength in axial compression and torsion compared to the cerclage (all P<0.01). Ultimate strength in lateral loading and torsion was significantly higher for bicortical screws (mean 3968N SD 657; mean 28.8Nm SD 5.9) compared to monocortical screws (mean 2748N SD 585; mean 14.4Nm SD 5.7Nm) and cerclages (mean 3001N SD 252; mean 3.2Nm SD 2.0) (P≤0.04). Stress distribution around the screw hole varied according to the screw type and load direction. InterpretationFixation components may be combined according to their individual advantages to achieve an optimal periprosthetic fracture fixation.

Comparison of postoperative stability of three rigid internal fixation techniques after sagittal split ramus osteotomy for mandibular advancement

IntroductionThe aim of this investigation was to compare the skeletal stability of three different rigid fixation methods after mandibular advancement. Material and methodsFifty-five class II malocclusion patients treated with the use of bilateral sagittal split ramus osteotomy and mandibular advancement were selected for this retrospective study. Group 1 (n = 17) had miniplates with monocortical screws, Group 2 (n = 16) had bicortical screws and Group 3 (n = 22) had the osteotomy fixed by means of the hybrid technique. Cephalograms were taken preoperatively, 1 week within the postoperative care period, and 6 months after the orthognathic surgery. Linear and angular changes of the cephalometric landmarks of the chin region were measured at each period, and the changes at each cephalometric landmark were determined for the time gaps. Postoperative changes in the mandibular shape were analyzed to determine the stability of fixation methods. ResultsThere was minimum difference in the relapse of the mandibular advancement among the three groups. Statistical analysis showed no significant difference in postoperative stability. However, a positive correlation between the amount of advancement and the amount of postoperative relapse was demonstrated by the linear multiple regression test (p < 0.05). ConclusionIt can be concluded that all techniques can be used to obtain stable postoperative results in mandibular advancement after 6 months.

The use of resorbable plates in association with dental arch stabilization in the treatment of mandibular fractures in children

PurposeThe purpose of this study was to investigate the effect of resorbable plate fixation in association with dental arch stabilization in the treatment of displaced mandibular fractures in children. Patients and methodsThirteen children (5 girls and 8 boys, age range 2 years 5 months to 12 years 2 months) with displaced mandibular fractures were included in this case series. Open reduction by intraoral approach was performed on these patients, and the fractures were fixed using resorbable plates and monocortical screws placed at the lower border of the mandible. At the same time, an arch bar or orthodontic wire splint was anchored using stainless steel wires or resin on the teeth to stabilize the whole mandibular dental arch. Postoperatively, follow-up was undertaken to evaluate the fracture healing, mandible movement, and mandible growth. ResultsPostoperatively, all patients achieved uneventful healing; premorbid occlusion restoration and wound healing were achieved, along with unimpaired function and normal growth and development of the mandible. Complications such as damage to tooth buds, infection, malunion, and nonunion were not encountered in these patients. ConclusionResorbable plates use in association with dental arch stabilization can provide good stabilization for mandibular fractures and is a promising approach for the treatment of displaced mandibular fractures in children.

Do Miniplates With Monocortical Screws Fail at an Unacceptably High Rate in Bilateral Sagittal Split Osteotomies? A Retrospective Chart Review

Do Miniplates With Monocortical Screws Fail at an Unacceptably High Rate in Bilateral Sagittal Split Osteotomies? A Retrospective Chart Review

Finite element analysis of the lower jaw implant in different resection scenarios

The goal of the research is to examine the different reconstruction solutions, which are used for the often-occurring jaw cancer resection and finding those areas that show higher potential risks of implant fracture. Within the research some finite element analysis based on data provided by Computer tomography have been concluded. The model in practice is built up with the most frequently used reconstruction plates and monocortical screws. Both lock and non-lock system solutions were examined. The results supporting the practice showed that indeed the maximal stress would rise in the implants closer to the resection in case of screws and in case of plates this will occur in the closer areas of resection within the thinner cross-sections.

Biomechanical Comparison Between Bicortical Pin and Monocortical Screw/Polymethylmethacrylate Constructs in the Cadaveric Canine Cervical Vertebral Column

To compare biomechanical stiffness of cadaveric canine cervical spine constructs stabilized with bicortical stainless steel pins and polymethylmethacrylate (PMMA), monocortical stainless steel screws with PMMA, or monocortical titanium screws with PMMA. Biomechanical cadaver study. Eighteen canine cervical vertebral columns (C2-C7) were collected from skeletally mature dogs (weighing 22-32 kg). Specimens were radiographed and examined by dual energy X-ray absorptiometry. Stiffness of the unaltered C4-C5 intervertebral motion unit was measured in extension, flexion and lateral bending using non-destructive 4-point bend testing. Specimens were then stabilized by (1) bicortical stainless steel pins/PMMA, (2) monocortical stainless steel screws/PMMA, or (3) monocortical titanium screws/PMMA. Mechanical testing was repeated and stiffness data from unaltered specimens and the 3 treatment groups were compared. All 3 surgical methods significantly increased stiffness of the C4-C5 motion unit compared with the unaltered specimen (P < .001 for all treatments), but stiffness was not significantly different among the 3 fixation groups (P = .578). In this model, monocortical screw fixation (with stainless steel or titanium screws) was biomechanically equivalent to bicortical fixation.

Skeletal stability after mandibular setback surgery: Comparison between the hybrid technique for fixation and the conventional plate fixation using an absorbable plate and screws

PurposeThe purpose of this study was to compare the temporal changes in condylar long axis and skeletal stability after sagittal split ramus osteotomy (SSRO) with the hybrid fixation technique and the conventional plate fixation. Patients and methodsOf 44 Japanese patients diagnosed with mandibular prognathism, 22 underwent SSRO with the conventional plate fixation (1 u-HA/PLLA plate and 4 monocortical screws in each side) and 22 underwent SSRO with a hybrid fixation technique (1 u-HA/PLLA plate and 4 monocortical screws and bicortical screw in each side). The temporal changes in condylar long axis and skeletal stability were assessed by axial, frontal, and lateral cephalograms. After surgery, breakage of the plate and screws was checked by 3-dimensional computed tomography (3DCT). ResultsAlthough there was a significant difference between the groups regarding Me–Ag in T1 (P = 0.0138), there were no significant differences between the groups for the other measurements in lateral, frontal and axial cephalometric analysis in each time interval. In two cases, 4 sides in the conventional plate fixation group, failure of the absorbable plate was found by 3DCT. However, there was no breakage in the hybrid fixation group. ConclusionThis study suggested that there were no significant differences in the postoperative temporal changes between the two groups in mandibular setback surgery.