Cortical Bone Screws Research Articles

Treatment of Mandibular Fractures With Michelet Technique: Manual Fracture Reduction Without Arch Bars

In our Bordeaux maxillofacial surgery unit, we have used the Michelet technique described for 40 years: manual fracture reduction and semi-rigid miniplate osteosynthesis fixation. No maxillomandibular fixation (MMF) with arch bars or with screws was used for reduction during osteosynthesis. The aim of this work was to evaluate results of this unknown manual reduction method. A total of 184 patients were reviewed. We recorded epidemiology of mandible fracture, clinical and radiologic evaluation before and after surgery, and treatment. Anatomic and functional manual reductions were the basic principle: manual maxillomandibular immobilization (functional) and manual fracture reduction (anatomic). In cases of condylar fractures without severe displacement, MMF with cortical bone screws was indicated (orthopedic treatment). Physiotherapy was also possible (functional treatment). In all, 315 mandible fractures sustained by 184 patients were reviewed into the study. Of the patients, 80% were treated by osteosynthesis: 54% by osteosynthesis treatment alone, 26% by osteosynthesis and orthopedic treatments. The average time required for osteosynthesis or osteosynthesis and orthopedic treatment was 56 minutes. We observed 0.67% of disturbed occlusion, 0.67% of pseudarthrosis, and 0.67% of bilateral temporomandibular joint internal derangement. Manual fracture reduction suppresses systematic MMF using arch bars during osteosynthesis of mandible fractures. Operating time and risk of complications are reduced. Functional results seem to be similar to that reported in the literature.

The effect of the screw pull-out rate on cortical screw purchase in unreamed and reamed synthetic long bones

Orthopaedic fracture fixation constructs are typically mounted on to human long bones using cortical screws. Biomechanical studies are increasingly employing commercially available synthetic bones. The aim of this investigation was to examine the effect of the screw pull-out rate and canal reaming on the cortical bone screw purchase strength in synthetic bone. Cylinders made of synthetic material were used to simulate unreamed (foam-filled) and reamed (hollow) human long bone with an outer diameter of 35 mm and a cortex wall thickness of 4 mm. The unreamed and reamed cylinders each had 56 sites along their lengths into which orthopaedic cortical bone screws (major diameter, 3.5 mm) were inserted to engage both cortices. The 16 test groups (n = 7 screw sites per group) had screws extracted at rates of 1 mm/ min, 5 mm/min, 10 mm/min, 20 mm/min, 30 mm/min, 40 mm/min, 50 mm/min, and 60 mm/ min. The failure force and failure stress increased and were highly linearly correlated with pull-out rate for reamed (R2 = 0.60 and 0.60), but not for unreamed (R2 = 0.00 and 0.00) specimens. The failure displacement and failure energy were relatively unchanged with pull-out rate, yielding low coefficients for unreamed (R2 = 0.25 and 0.00) and reamed (R2 = 0.27 and 0.00) groups. Unreamed versus reamed specimens were statistically different for failure force (p = 0.000) and stress (p = 0.000), but not for failure displacement (p = 0.297) and energy (0.054 < p < 1.000). This is the first study to perform an extensive investigation of the screw pull-out rate in unreamed and reamed synthetic long bone.

Retrospective study on efficacy of intermaxillary fixation screws

Background: We evaluated the efficacy of intermaxillary fixation (IMF) screws in the treatment of mandibular fractures. Methods: Two hundred patients with mandibular fractures, treated by IMF using these screws, were evaluated by pre and postoperative panoramic radiographs. Clinical testing was carried out for vitality and abnormal mobility of teeth adjacent to the site of screw insertions. Other factors such as possible iatrogenic dental injuries, loss, breakage or screw cover by oral mucosa and postoperative occlusion were also studied. Result: The most important complication noticed was iatrogenic damage to dental roots. Conclusion: Use of intraoral cortical bone screws for IMF is a valid alternative to arch bars in the treatment of mandibular fractures. Iatrogenic injury to dental roots is the commonest problem which can be minimized by an experienced surgeon.

Result of Maxillomandibular Fixation Using Intraoral Cortical Bone Screws for Condylar Fractures of the Mandible

Treatment of mandibular condylar fractures is not standardized. The maxillomandibular cortical bone screw fixation technique carries many advantages. The aim of this work was to evaluate this technique for routine method. Fifty patients treated by maxillomandibular fixation (MMF) by use of cortical bone screws from 2004 to 2006 were retrospectively analyzed. In our maxillofacial surgery unit in Bordeaux, France, our indication is to treat extra-articulated fractures without severe displacement by MMF. The mean time required for MMF was 13 minutes, and fixation occurred after a mean of 16 days. Screw removal was performed after a mean of 26 days, and this required local anesthesia. Of the patients, 48 had good occlusion. Two patients had persistent lateral cross bites. Two patients had mandible deviation when they opened their mouths, and mouth opening was limited in one patient. Two patients had temporomandibular joint pain. MMF screws have more advantages and fewer disadvantages than arch bars when closed treatment has been selected as the treatment of choice.

O.665 Use of plates and screws in flxation of condylar fractures

Treatment of mandibular condylar fractures is not standardized. The maxillomandibular cortical bone screw fixation technique carries many advantages. The aim of this work was to evaluate this technique for routine method.Fifty patients treated by maxillomandibular fixation (MMF) by use of cortical bone screws from 2004 to 2006 were retrospectively analyzed. In our maxillofacial surgery unit in Bordeaux, France, our indication is to treat extra-articulated fractures without severe displacement by MMF.The mean time required for MMF was 13 minutes, and fixation occurred after a mean of 16 days. Screw removal was performed after a mean of 26 days, and this required local anesthesia. Of the patients, 48 had good occlusion. Two patients had persistent lateral cross bites. Two patients had mandible deviation when they opened their mouths, and mouth opening was limited in one patient. Two patients had temporomandibular joint pain.MMF screws have more advantages and fewer disadvantages than arch bars when closed treatment has been selected as the treatment of choice.

Effect of surface topography on removal of cortical bone screws in a novel sheep model

Difficulty in removing implants used in trauma patients can be a complication, and increased bone-implant adhesion likely is a major contributing factor. In vitro studies have shown that surface morphology of implant materials has the ability to influence cellular responses, with polished surfaces decreasing the potential for mineralization. This study examined the effect of polishing commercially pure titanium (cpTi) and the titanium alloy TAN on the removal torque and percentage bone-implant contact in cortical and cancellous bone of sheep. Polishing had a significant effect on both removal torque and percentage bone-implant contact, with the polished implants demonstrating a lower removal torque in both cortical and cancellous bone. Polished cpTi and stainless steel were similar in terms of surface roughness and removal torque. However, polished TAN, which was not as smooth as polished cpTi, did not show the same low level for reducing removal torque. Improved polishing of TAN should reduce the removal torque further. The results of the study show that polishing is promising in improving the ease of implant removal after fracture fixation and repair.

The Effect of Pilot Hole Size on the Insertion Torque and Pullout Strength of Self-Tapping Cortical Bone Screws in Osteoporotic Bone

All surgical screws can experience failure if the torsional, tensile, and flexion loads exerted on the screws are excessively high. The use of self-tapping screws (STS) results in higher insertion torques (IT) as these screws cut their own threads in the pilot hole drilled in the bone. In this study, the torque for inserting the STS into an osteoporotic bone block for different pilot hole sizes (PHS) was measured and the pullout strength (PS) for extraction of the screws was determined for different depths of insertion, 0 mm, 1 mm, and 2 mm beyond the far cortex. Seventy-two Synthes stainless steel STS (40 mm length and 3.5 mm diameter) were inserted into pilot holes of sizes 2.55 (A: 73% OD), 2.50 (B: 71.5%), 2.45 (C: 70%), and 2.8 mm (D: 80%). Using a digital torque screwdriver, screws were inserted to 0 mm, 1 mm or 2 mm past the far cortex. Pullout tests were conducted with an Instron materials testing system. Analysis of variance and Student-Neuman-Keuls tests were performed to determine the effect of DOI and PHS on the loading energy, PS, and IT. Results demonstrated that IT of the screws inserted into pilot holes A, B, and C were higher than those in D. It was also observed that PS and loading energy for 1 mm and 2 mm penetration past the far cortex were higher than those for 0 mm regardless of PHS. This study also found that an increase in PHS to 2.8 mm will reduce IT but will also reduce the PS relative to a PHS of 2.5 mm, the current standard for 3.5 mm screws. The results of previously published studies regarding the effect of pilot hole size on PS in healthy cortical bone cannot be applied to the osteoporotic environment. The findings presented in this research support using PHS no larger than 71.5% of the screw outer diameter (i.e., pilot hole size of 2.5 mm for 3.5 mm screws) and inserting screws at least 2 mm beyond the far cortex to maximize PS and minimize iatrogenic damage in osteoporotic bone.

Maxillomandibular Fixation Using Intraoral Cortical Bone Screws and Specially Designed Metal Hooks (Ottenhaken) in the Conservative Treatment of Mandibular Fractures

The present work evaluated the success of maxillomandibular fixation (MMF) by intraoral cortical bone screws and specially designed metal hooks (Ottenhaken) in nondislocated or slightly dislocated mandibular fractures. A total of 44 patients who sustained various types of mandibular fractures were treated at the University Hospital for Craniomaxillofacial and Oral Surgery, Vienna Medical School by MMF with Ottenhaken only. The patients were evaluated by preoperative and postoperative radiography, and clinical testing was performed by thermal testing with a cold spray and by assessing the degree of tooth mobility adjacent to the inserted screws. To determine the success of the treatment, various parameters, including screw or hook fracture, screw loosening, local infection of the punctured mucosa, and iatrogenic tooth damage, were considered. The screws and hooks were successfully inserted and MMF was engaged with tight elastics in all cases. The most frequent complication was rupturing of the elastics, necessitating replacement. In 5 patients, local infection of the mucosa around the screw led to severe pain that was treated successfully with analgesics. The screws could be left in place in all 5 cases. Hook fracture and screw loosening each occurred in 1 patient. No iatrogenic injuries of the dental roots were noted. After screw removal, all wounds healed uneventfully. The use of intraoral cortical bone screws and specially designed metal hooks (Ottenhaken) for MMF is a useful, valid alternative to arch bars that carries only rare, mild complications.

Surgical correction of metacarpophalangeal valgus deformity in an alpaca

A 1-month-old alpaca cria presented with a 13 degree valgus deformity of the left metacarpophalangeal joint. The angular limb deformity was centered on the distal metacarpal physes. Transphyseal bridging of the physes was recommended. Two 2.7 mm cortical bone screws were placed either side of the distal metacarpal physes and a figure of eight wire was placed medially around the screw heads. The screws extended through the medial metacarpus into the axial cortex of the lateral metacarpus. Seven weeks after surgery the limb was straight and the screws and wire were removed. Transphyseal bridging of the distal metacarpal physes can be effectively used for the treatment of metacarpophalangeal valgus in crias with open physes.

Measurement of Orthopedic Cortical Bone Screw Insertion Performance in Cadaver Bone and Model Materials

In this study, a method was developed for distinguishing insertion and driving performance between different self-tapping bone screw designs. To measure screw starting load, torque and displacements, a test apparatus was developed utilizing a modified drill press with the capability to measure in-line torque, axial compression load, and axial displacement. Specimens were inserted into cadaver bone to measure a baseline response and a bone analog was developed to mimic the bicortical application of screws in the cadaver model. Recorded data could be used to measure a distinguishable screw starting load and the torque for the insertion of bone screws. The results were similar between the cadaver bone and the bone analog. The average insertion load ranged from 5.4 to 64.5 N in cadaver tests and 9.0–41.0 N in the construct tests. Average first cortex insertion torques ranged from 0.53 to 0.66 N-m in the cadaver tests and 0.29–0.32 N-m in the construct test. Average second cortex insertion torques ranged from 0.70 to 1.03 N-m in the cadaver tests and 0.60–0.63 N-m in the construct tests. This method successfully illuminated differences between several different self-tapping screw designs and was also successfully employed to determine the impact of design and manufacturing methods on screw performance. An interesting finding in this study is that axial starting load is very sensitive to screw tip design whereas insertion torque is not.

Investigation on the Potential of Magnesium Alloy AZ31 as a Bone Implant

Degradable implants have been in use for bone surgery for decades. However, degradable metal implants are one of the new research areas of biomaterials science. There is a potential for application of degradable metal implants as screws and plates in bones. Magnesium alloys are one of the new candidate materials for degradable implants. Magnesium has good biocompatibility due to its low toxicity, and it is a corroding, i.e. dissolvable, metal. Furthermore, magnesium is needed in human body, and naturally found in bone tissue. Mechanical properties of magnesium alloys are dimensionally comparable to the cortical bone substance. In this study, corrosion behavior of magnesium metal at the bone interface and the possibility of new bone cell formation have been investigated. Cortical bone screws were machined from magnesium alloy AZ31 extruded rod and implanted to hip-bones of sheep via surgery. Three months after surgery, the bone segments carrying these screws were removed from the sacrificed animals. Samples were sectioned to reveal Mg/bone interfaces and investigated using optical microscope, SEM-EDS and radiography. Optical and SEM images showed that there was a significant amount of corrosion on the magnesium screw. The elemental mapping results indicate, due to the presence of calcium and phosphorus elements, that there exists new bone formation at the interface. From the results of this study, it may be stated that the potential for using magnesium alloys as a bone implant material is expected to be significant.

Factors affecting the stability of screws in human cortical osteoporotic bone

We investigated several factors which affect the stability of cortical screws in osteoporotic bone using 18 femora from cadavers of women aged between 45 and 96 years (mean 76). We performed bone densitometry to measure the bone mineral density of the cortical and cancellous bone of the shaft and head of the femur, respectively. The thickness and overall bone mass of the cortical layer of the shaft of the femur were measured using a microCT scanner. The force required to pull-out a 3.5 mm titanium cortical bone screw was determined after standardised insertion into specimens of the cortex of the femoral shaft. A significant correlation was found between the pull-out strength and the overall bone mass of the cortical layer (r(2) = 0.867, p < 0.01) and also between its thickness (r(2) = 0.826, p < 0.01) and bone mineral density (r(2) = 0.861, p < 0.01). There was no statistically significant correlation between the age of the donor and the pull-out force (p = 0.246), the cortical thickness (p = 0.199), the bone mineral density (p = 0.697) or the level of osteoporosis (p = 0.378). We conclude that the overall bone mass, the thickness and the bone mineral density of the cortical layer, are the main factors which affect the stability of a screw in human female osteoporotic cortical bone.

Evaluation of compression generated by self compressing Orthofix bone pins and lag screws in simulated lateral humeral condylar fractures

A simulated lateral humeral condylar fracture was created in each of the 52 humeri collected from 26 dogs. One humerus from each pair was stabilized with a 2.0 mm cortical bone screw which was inserted in lag fashion. The other humerus from each pair was stabilized with a 2.2 mm threaded diameter Orthofix pin inserted across the condyle. Prior to each repair, an antirotational K-wire was placed and then the Pressurex Sensitive film was inserted in the osteotomy site in order to determine the compressive pressure (MPa), compressive force (KN), and area of compression (cm(2)) achieved during fixation. The maximum insertional torque achieved before stripping was measured for each implant. The mean compression generated by insertion of a 2.0 mm lag screw was 20.36 +/- 1.51 MPa compared to 18.88 +/- 1.76 MPa generated by a 2.2 mm Orthofix pin (p < 0.003). The mean area of compression generated by insertion of a 2.0 mm lag screw was 2.39 +/- 1.29 cm(2), compared to 1.16 +/- 0.84 cm(2) generated by insertion of a 2.2 mm Orthofix pin (p < 0.0001). The mean compressive force (compression x area compressed) generated by insertion of a 2.0 mm lag screw was 4.96 +/- 2.90 Kn, compared to 2.20 +/- 1.65 Kn generated by insertion of a 2.2 mm Orthofix pin (p < 0.0001). The mean insertion torque to failure for the lag screws was 0.49 +/- 0.07 NM, compared to 0.91 NM +/- 0.18 NM generated by the Orthofix pins (P < 0.0001). Both repair methods are likely to be acceptable for the repair of similar fractures in small breed dogs.

Treatment of old scaphoid fractures by internal fixation with modified common screws

目的 探讨普通螺钉简单改制成加压螺钉内固定治疗陈旧性腕舟骨骨折的临床疗效.方法 1995年1月～2002年12月采用改制的加压螺钉内固定治疗陈旧性腕舟骨骨折25例,其中延迟愈合17例,骨不连接、假关节形成8例.将普通的皮质骨螺钉去掉部分螺纹后,使之变成具有加压作用的螺钉,通过简单的手术器械将其拧入复位后的舟骨内,对舟骨断端加压固定.结果 19例获得随访,时间1～6年(平均3年),14例骨折愈合,平均愈合时间7个月,腕关节活动范围在106°～128°之间;3例未愈合,2例舟骨近端塌陷变形.结论改制加压螺钉治疗腕舟骨骨折具有对骨折端有加压作用、固定稳固、可经关节面置入、对关节干扰小、材料易取及操作简单等优点,是治疗陈旧性腕舟骨骨折的有效方法。

Stripping torque as a predictor of successful internal fracture fixation

Internal fixation of fractures using plates and screws is a common method of treatment. Occasionally the internal fixation fails prior to fracture healing. This often requires revision surgery. Determining the force that internal fixation needs to withstand postoperatively would enable this force to be applied intraoperatively as a test to predict successful fixation. The purpose of the present paper was to determine the minimum stripping torque needed to predict successful internal fixation strength. The pull-out strength and stripping torque relationships of 4.5-mm cortical bone screws in Sawbones polyurethane foam were determined. Screw forces were directly measured using an LCM load cell washer on a model intertrochanteric neck of femur fracture fixed with 135 degrees 4-hole pin and plate loaded to single leg stance conditions. Additionally a 135 degrees 4-hole pin and plate was mounted on foam blocks and loaded until failure of the shaft screws from the foam occurred. Predicted stripping torque/yield load was determined. Pull-out strength and stripping torque of 4.5-mm cortical bone screws in polyurethane foam have a high degree of linear correlation R(2) = 0.95. Direct measurement of shaft screw forces at single leg stance conditions were 585-686 N. This correlated with a stripping torque of 0.9 Nm. Load to yield testing at single leg stance conditions corresponded to a stripping torque of 1.8 Nm. Withstanding 0.9-1.8 Nm of torque during insertion of the femoral shaft screws of a 135 degrees 4-hole pin and plate predicts that the construct will successfully withstand single leg stance.

Biomechanical Comparison of Orthofix Pins and Cortical Bone Screws in a Canine Humeral Condylar Fracture Model

To compare shear stability of simulated humeral lateral condylar fractures reduced with either a self-compressing pin or cortical bone screw. In vitro biomechanical tests. Bilateral cadaveric canine humeri (n=18) without evidence of elbow disease. Lateral condylar fracture was simulated by standardized osteotomy. Bone fragments were stabilized with a self-compressing pin or a cortical bone screw (2.7 or 3.5 mm) inserted in lag fashion. Specimens were mounted in a materials testing system and the condylar fragment displaced in a proximal direction until failure. Mechanical testing variables derived from load-deformation curves were compared between stabilization methods using a Student's paired t-test. There were no statistically significant differences for mechanical testing variables between pin and screw stabilized specimens at expected walk and trot loads. Three yield points subjectively coincided with yield of the interfragmentary interface (Y1), bone at the implant interface (Y2), and implant deformation (Y3). Displacements at Y1 were 48-156% greater for pin than screw stabilized specimens. Y2 and Y3 loads were higher for screw than pin stabilized specimens, but likely supraphysiologic for dogs convalescing after surgical repair. A self-compressing pin or a cortical bone screw inserted in lag fashion both provided adequate strength in applied shear to sustain expected physiologic loads through the repaired canine elbow during postoperative convalescence. Because self-compressing pins were easy to implant and mechanical properties were not significantly different than cortical screws at expected physiologic loads, pins should be considered for the repair of traumatic humeral condylar fractures.

An audit of mandibular fractures treated by intermaxillary fixation using intraoral cortical bone screws

During the last 10 years, intermaxillary fixation using intraoral cortical bone screws has been introduced for the treatment of mandibular fractures. The aim of this work was to evaluate the indications and possible complications of this method. Sixty-two patients with mandibular fractures, treated by intermaxillary fixation using these screws, were evaluated by preoperative and postoperative panoramic radiographs. Clinical testing was carried out for vitality and abnormal mobility of teeth adjacent to the site of screw insertions. To evaluate the efficacy of this method, different factors were considered such as possible iatrogenic dental injuries, loss, breakage or screw cover by oral mucosa and postoperative occlusion. The most important complication was iatrogenic damage to dental roots (1.5%), 4.9% of the screws were covered by oral mucosa and 1.9% were lost, while none were broken. Malocclusion was observed in one patient (1.6%) and lack of consolidation of a displaced fracture of the mandibular body in another patient. Use of intraoral cortical bone screws for intermaxillary fixation is a valid alternative to arch bars in the treatment of mandibular fractures. Iatrogenic injury to dental roots is the most important problem of this procedure, but can be minimized by an experienced surgeon.

Mechanical effects of high density polyethylene Dynamic Compression Plate hole inserts on bone-plate constructs

This study was conducted in order to investigate the mechanical effects of high density polyethylene screw hole inserts in 4.5 mm Dynamic Compression Plate (DCP)--synthetic bone constructs. A mid-shaft 'osteotomy' was created in synthetic bone cylinders. The bisecting 'osteotomy' was reduced using six-hole broad DCPs and 4.5 mm cortical bone screws. The screws adjacent to the 'osteotomy' were placed using a load-guide. The remaining screws were placed in neutral position. High density polyethylene DCP screw hole inserts were incorporated with each screw in neutral position, in the experimental group. The bone plate constructs were tested in four point cyclical bending with the plates loaded at 2,000 Newtons, for a total of 6,000 cycles. Osteotomy gap was measured at 3,000 and 6,000 cycles. Screw head deflection adjacent to the osteotomy was measured. Kruskal-Wallis non-parametric testing was used for statistical comparisons. There was significantly less gapping at the osteotomy site in the treatment group after 3,000 cycles (0.49 +/- 0.18 mm [control] vs. 0.06 +/- 0.14 mm [treated], P=0.02) and 6,000 cycles (0.6 +/- 0.18 mm [control] vs. 0.1 +/- 0.22 mm [treated], P=0.02). The screws adjacent to the gap were significantly more deformed in the control group than those in the treated constructs (3.63 +/- 1.81 [control] vs. 1.06 +/- 1.55 [treated], P=0.0002). The polyethylene inserts improved the interface between bone plate and screw head, resulting in decreased relative movement of the implant and bone. The polyethylene inserts also resulted in less bending of the loaded screws.

Cortical bone screw fixation in ionically modified apatite cements

Hydroxyapatite cements are used in reconstruction of the face; usually in well-defined cavities where the cement can be stabilized without the need for internal fixation. A hydroxyapatite cement that could enable screw fixation and some loading therefore has considerable potential in maxillofacial reconstruction. It has been demonstrated recently that water demand of calcium phosphate cements can be reduced by ionically modifying the liquid component. This study investigated the capacity of an ionically modified precompacted apatite cement to retain self-tapping cortical bone screws. Screw pullout forces were determined in the direction of the screw long axis and perpendicular to it, using cortical bone and polymethylmethacrylate cement as a control. In bending pullout tests, measured forces to remove screws from ionically modified precompacted cement were insignificantly different from cortical bone. However, pullout forces of bone screws from hydroxyapatite cement decreased with aging time in vitro.

UNDIFFERENTIATED SARCOMA RESOLVED BY FORELIMB AMPUTATION AND PROSTHESIS IN A RADIATED TORTOISE (GEOCHELONE RADIATA)

An adult female, radiated tortoise (Geochelone radiata) presented with a grossly swollen left forelimb that restricted mobility and prevented limb withdrawal. Clinical pathology revealed leukopenia (1.9 x 10(9)/L) and hyperproteinemia (69 g/L) that on protein electrophoresis was attributed to increased acute-phase proteins in the alpha fraction (26.4 g/L). Biopsy revealed a poorly differentiated soft tissue sarcoma. Surgical amputation at the proximal humerus was curative. To encourage postoperative mobility, a novel methylmethacrylate prosthesis, molded from a lubricated transected tennis ball, was adhered to the plastron using three cortical bone screws. This is the first recorded case of a sarcoma in the genus Geochelone.