Bicortical Fixation Research Articles

Tibial fractures after tibial tubercle osteotomies for patellar instability: A comparison of three osteotomy configurations

Tibial tubercle osteotomies (TTOs) are a seemingly straightforward technique; however problems with bony union, implant failure, wound infections, and fractures have been reported in the literature. A database search identified all patients who had a TTO performed for patellofemoral instability between 1 March 2000 and 30 July 2008 by a single surgeon. The TTO technique was modified twice during the study period (December 2003 and June 2007, respectively), thereby creating three similar patient cohorts. TTOs were performed in 101 knees (90 patients), in which 34 knees (29 patients) received the blunt technique (TTO-B), 32 knees (30 patients) the sloped technique (TTO-S), and 35 knees (31 patients) the greenstick technique (TTO-G). Mean age of the patients (75 females, 15 males) was 16.0years (range 12.2-20.2years). Overall, six patients had complications, namely, six tibia fractures and no nonunions, for an overall complication rate of 5.9%. In the TTO-B group, four patients had four tibia fractures for an overall bony complication rate of 11.8%. In the TTO-S group, two patients had two delayed unions which developed into tibia fractures for an overall bony complication rate of 6.2%. There were no complications (0%) in the TTO-G group. No correlation was identified between TTO screw size and complications. The caudal aspect of the osteotomy was the location of the tibia fracture in five knees and the caudal screw in 1 knee, at a mean of 11weeks postoperatively. All fractures were treated only with splint or cast immobilization and protected weight-bearing. The overall bony complication rate was 5.9% for the TTOs in this study. Utilizing the TTO-G technique with rigid two-screw, bicortical fixation the complication rate could be lowered to 0%. Avoidance of periosteal stripping, and secondary cortical devascularization at the caudal aspect of the TTO appears to optimize bony consolidation, thereby minimizing fractures. Bony complications are an infrequent problem after TTO. Greensticking the distal end of the TTO can minimize postoperative tibia fractures. Running and sports should not be permitted until complete cortical healing is documented on the lateral radiograph.

Biomechanical Study of SonicWeld Rx Pin in Cortical Bone Graft Layering Technique

The purpose of this in vitro study was to determine the biomechanical values of the SonicWeld Rx pin system in comparison with titanium screws for use in onlay cortical bone grafting. In this study, 2.1-mm SonicWeld Rx pins and 1.5-mm titanium screws, measuring 7 mm in length, were used. Sawbone blocks were positioned to simulate an onlay bone graft, and the pins and screws were used to replicate bicortical fixation. Four groups were designated for vertical load application, and failure of the fixation was determined when stability was compromised. Study groups consisted of fixation material types and number of fixation appliances. A Bose Electroforce 3300 system was used to deliver the force and to obtain data. Comparison of SonicWeld Rx 1-pin fixation with titanium 1-screw fixation showed similar peak resistance loads. Average peak loading resistance for SonicWeld Rx 1-pin fixation was 65.54 N and that for titanium 1-screw fixation was 59.37 N, with no significant difference (P = .9698). Average peak strength of SonicWeld Rx 2-pin and titanium 2-screw fixations was 110.24 and 97.3 N, respectively, with no significant difference (P = .1041). Based on the measured biomechanical values, SonicWeld Rx fixation can withstand similar peak load forces compared with that of titanium screw fixation. The SonicWeld Rx fixation can be an alternative method of fixation for onlay bone grafting in dentoalveolar ridge augmentation.

Experimental Fracture Model versus Osteotomy Model in Metacarpal Bone Plate Fixation

Introduction. Osteotomy or fracture models can be used to evaluate mechanical properties of fixation techniques of the hand skeleton in vitro. Although many studies make use of osteotomy models, fracture models simulate the clinical situation more realistically. This study investigates monocortical and bicortical plate fixation on metacarpal bones considering both aforementioned models to decide which method is best suited to test fixation techniques. Methods. Porcine metacarpal bones (n = 40) were randomized into 4 groups. In groups I and II bones were fractured with a modified 3-point bending test. The intact bones represented a further control group to which the other groups after fixation were compared. In groups III and IV a standard osteotomy was carried out. Bones were fixated with plates monocortically (group I, III) and bicortically (group II, IV) and tested for failure. Results. Bones fractured at a mean maximum load of 482.8 N ± 104.8 N with a relative standard deviation (RSD) of 21.7%, mean stiffness was 122.3 ± 35 N/mm. In the fracture model, there was a significant difference (P = 0.01) for maximum load of monocortically and bicortically fixed bones in contrast to the osteotomy model (P = 0.9). Discussion. In the fracture model, because one can use the same bone for both measurements in the intact state and the bone-plate construct states, the impact of inter-individual differences is reduced. In contrast to the osteotomy model there are differences between monocortical and bicortical fixations in the fracture model. Thus simulation of the in vivo situation is better and seems to be suitable for the evaluation of mechanical properties of fixation techniques on metacarpals.

Fractures of the Proximal Fifth Metatarsal: Percutaneous Bicortical Fixation

BackgroundDisplaced intraarticular zone I and displaced zone II fractures of the proximal fifth metatarsal bone are frequently complicated by delayed nonunion due to a vascular watershed. Many complications have been reported with the commonly used intramedullary screw fixation for these fractures. The optimal surgical procedure for these fractures has not been determined. All these observations led us to evaluate the effectiveness of percutaneous bicortical screw fixation for treating these fractures.MethodsTwenty-three fractures were operatively treated by bicortical screw fixation. All the fractures were evaluated both clinically and radiologically for the healing. All the patients were followed at 2 or 3 week intervals till fracture union. The patients were followed for an average of 22.5 months.ResultsTwenty-three fractures healed uneventfully following bicortical fixation, with a mean healing time of 6.3 weeks (range, 4 to 10 weeks). The average American Orthopaedic Foot & Ankle Society (AOFAS) score was 94 (range, 90 to 99). All the patients reported no pain at rest or during athletic activity. We removed the implant in all cases at a mean of 23.2 weeks (range, 18 to 32 weeks). There was no refracture in any of our cases.ConclusionsThe current study shows the effectiveness of bicortical screw fixation for displaced intraarticular zone I fractures and displaced zone II fractures. We recommend it as one of the useful techniques for fixation of displaced zone I and II fractures.

Biomechanical analysis of bicortical versus unicortical locked plating of mid-clavicular fractures

Operative fixation of displaced mid-shaft clavicle fractures has been shown to improve the functional outcomes and decrease the likelihood of non-union; however, little is known about the need for locking screws versus traditional screws. We, therefore, evaluated the strength of unicortical locked plating versus traditional bicortical non-locking fixation methods. Ten matched pairs of fresh, frozen cadaver clavicle specimens were obliquely osteotomized through the mid-shaft to represent the most common fracture pattern. After randomization, the clavicles were repaired using pre-contoured plates with either standard bicortical non-locking screws or unicortical locking screws. The constructs were then potted in cement and tested on a MTS machine using a custom gimble and evaluated for load to failure and axial and rotational stiffness. There was no significant difference between the constructs in terms of axial stiffness (locking 688.3 ± 306.2 N/mm, non-locking 674.5 ± 613.0 N/mm; p = 0.77) or load to failure (locking 720.1 ± 232.0 N, non-locking 664.8 ± 167.5 N; p = 0.46). However, rotational stiffness varied significantly (locking 1.70 ± 0.91 N-m/mm, non-locking 2.49 ± 0.78 N-m/mm, p = 0.049) with bicortical non-locking constructs exhibiting higher torque values. Unicortical fixation using pre-contoured plates and locking screws has a similar biomechanical profile compared to gold standard non-locked bicortical screws in cyclic axial compression and axial load to failure. Non-locking constructs were stiffer under rotational testing. This technique may provide a suitable biomechanical environment for bony healing. This may also improve the safety of clavicle plating by protecting infraclavicular structures from injury during drilling or screw penetration as it obviates the need for bicortical fixation.

The role of lateral-entry Steinmann pins in the treatment of pediatric supracondylar humerus fractures

Loss of pin fixation in supracondylar fractures can occur with failure to achieve bicortical fixation. Bicortical fixation may be challenging for those pins that attempt to penetrate the diaphyseal cortex, where the bone is thick. Lateral-entry Steinmann pins may allow for better penetration through cortical bone because they are more rigid than typical Kirschner wires. A retrospective review of 16 children with type III supracondylar fractures treated by a single surgeon using Steinmann pins was undertaken. The average age at presentation was 6years. Following closed reduction, all fractures were maintained with three lateral-entry pins. At least one Steinmann pin was placed in the lateral column of the distal humerus in each pin construct. Follow-up radiographs indicated a mean Baumann's angle of 72.9° (range 64°-82°). There was no statistically significant change in the Baumann's angle or axial alignment at final follow-up. All but one fracture healed in an anatomic position on the lateral view. Steinmann pins placed through a lateral-entry point are effective in controlling the reduction of high-grade supracondylar fractures. The fixation is excellent and avoids potential ulnar nerve complications of medial entry.

Effect of the Degree of Osteoporosis on the Biomechanical Anchoring Strength of the Sacral Pedicle Screws

An in vitro laboratory study. (i) To evaluate the effect of osteoporotic degree in determining the strength of sacral screw fixation and (ii) to compare the strength of unaugmented bicortical pedicle screw and polymethylmethacrylate (PMMA) augmented unicortical pedicle screw in sacral fixation. Screw loosening is a clinical problem in lumbosacral fusions, especially in osteoporotic patients. To improve the screw anchoring strength of sacrum, bicortical and PMMA augmented sacral pedicle screw fixation techniques are widely used in clinical practice. However, the biomechanical strength of the bicortical and PMMA augmented sacral screw fixations remains undetermined in different degrees of osteoporosis. Twenty-five fresh osteoporotic cadavers were used in this study. According to the value of lumbar bone mineral density (BMD) assessed by DEXA, specimens were divided into 3 groups: group A (N=9): BMD=0.7 to 0.8 g/cm, group B (N=8): BMD=0.6 to 0.7 g/cm, and group C (N=8): BMD<0.6 g/cm. In each specimen, S1 pedicle screw was inserted bicortically on the left side, and S1 pedicle screw with PMMA augmentation was inserted unicortically on the right side of the sacrum. Following a dynamic cyclic loading from 30 to 250 N on the screw head for 2000 cycles, the subsidence displacement and axial pull-out strength of each screw were measured. No anchoring failure (defined as the subsidence displacement exceeding 2 mm within 2000 loading cycles) occurred in group A and B. However, in group C, 6 cases (75%) in bicortical fixation and 5 cases (63%) in PMMA augmented fixation failed during cyclic loading. In group A, no significant difference between the bicortical and PMMA augmented fixations was detected in terms of the subsidence and maximal pull-out strength. In group B, significantly less subsidence and higher maximal pull-out strength were demonstrated in the PMMA augmented technique than that in the bicortical fixation. Both techniques exhibited lower subsidence of the screw in group A than in group B. The bicortical technique exhibited higher maximum pull-out strength in group A than that in group B. However, statistical difference in terms of PMMA augmentation was not detected between group A and B. For BMD value more than 0.70 g/cm, bicortical sacral pedicle screw fixation could obtain sufficient anchoring strength comparable with the PMMA augmented technique. When BMD value is within 0.6 to 0.7 g/cm, the PMMA augmented technique would be more beneficial in improving the fixation strength than the bicortical fixation. For BMD values less than 0.6 g/cm, early screw loosening may occur in both bicortical and PMMA augmented fixations.

Mechanical Evaluation of a 4-mm Cancellous “Rescue” Screw in Osteoporotic Cortical Bone: A Cadaveric Study

Obtaining sufficient fracture fixation in osteoporotic bone is challenging. The purposes of the current study were (1) to compare the pullout strength of a 4-mm cancellous screw (cancellous screw group) with that of a 3.5-mm cortical screw (cortical screw group), and (2) to measure the pullout strength of a 4-mm cancellous screw placed as a rescue screw (rescue screw group) in a stripped 3.5-mm cortical screw (stripped screw group) hole while controlling for bone density and cortical thickness. We inserted 4 screws, one from each experimental group, into 11 osteoporotic cadaveric radii, while recording the insertion torque. Radii were mounted on a servohydraulic testing machine, and each screw was pulled out at a rate of 5 mm/min. Pullout strength was recorded. The effects of cortical thickness (near, far, and total), bone density, insertion torque, and the experimental screw group (cortical, cancellous, stripped, and rescue screw groups) on pullout strength were analyzed using multiple linear regression with random effects. Statistical significance was set at P < 0.05. There was no significant difference in pullout strength between the cortical and cancellous screw groups. The rescue screw group had significantly less pullout strength than did the cortical and cancellous screws, and only partly increased pullout strength compared with stripped screws. Bone density significantly affected pullout strength, but insertion torque and cortical thickness were not significant covariates. There seems to be no advantage in using a cancellous screw over a cortical screw in bicortical fixation in osteoporotic bone. Although the rescue screw provided greater pullout strength than the stripped screw, it is unknown if the purchase it provides is clinically sufficient.

C2 Anatomy and Dimensions Relative to Translaminar Screw Placement in an Asian Population

A cadaveric specimen study. To determine the applicability of a modified C2 translaminar screw placement in the general adult population and to provide pertinent clinical data for screw insertion. C2 intralaminar screw fixation has recently been popularized, but this technique carries a potential drawback that the screw may breakout ventrally into the spinal canal. For this reason, a modified C2 translaminar screw fixation technique was developed to intraoperatively verify screw position and thereby decrease the risk or canal compromise. To our knowledge, there has been not an anatomic study evaluating this modification of the translaminar screw technique. The tips of the modified screws were aimed such that they exited the dorsal cortex of the center of the contralateral lateral mass, achieving bicortical fixation. A total of 120 adult C2 vertebrae were evaluated bilaterally for the following: thickness of the cranial, midportion, and caudal edge of C2 lamina; the heights of the spinous process, lamina, and lateral mass; inclination angle of the laminae, screw projection length, and trajectory angle of cranial and caudal C2 translaminar screw. A total of 83.3% specimens had bilateral laminar thicknesses ≥4.0 mm and a spinous process height ≥9.0 mm; 5% had a laminar thickness less than 4.0-mm bilaterally; 9.2% had a laminar thickness less than 4.0 mm on one side; 2.5% had a spinous process height lower than 9.0 mm. A large percentages of C2 laminae are of sufficient size to safely accommodate a bicortical 3.5-mm diameter screw. The thickness of the lamina and the height of the spinous process are the 2 limiting factors for safe translaminar screws placement. Using a bicortical technique confirms the position of the screw and thereby helps to decrease the risk of neurologic injury from screw penetration of the inner cortex of the lamina.

Neurovascular Risks of Anteroinferior Clavicular Plating

Anteroinferior plating has been described for internal fixation of clavicular fractures, citing improved bicortical fixation, less hardware prominence, and safer drill trajectories compared with other plate configurations. This anatomic study defined structures at risk during anteroinferior clavicular plating. Four paired cadaveric specimens (8 clavicles) from ages 75 to 93 years were systematically dissected. Using the screw paths associated with an anteroinferior plate (anteroinferior to superoposterior), the distance from the posterior clavicle cortex to the nearest vital structure was measured at 5 different positions along the clavicle. In the medial half of the clavicle, the subclavian artery is in closest proximity to the clavicle, measuring, on average, 22.95 mm and 15.10 mm at point A and B. At the lateral three-fifths point of the clavicle (point C), the brachial plexus is 12.76 mm from the posterior clavicle and is more at risk than the subclavian artery. Lateral to the three-fifth point of the clavicle, there were no vital structures that could be injured by overdrilling. Our results suggest that more care should be observed with placement of screws in the medial half of the clavicle where subclavian artery damage is more likely.

C1 Pedicle Screws Versus C1 Lateral Mass Screws

In vitro biomechanical study. To compare the pullout strengths and the biomechanical stabilities afforded by C1 lateral mass screws and C1 pedicle screws using bicortical and unicortical fixation techniques. Posterior screw fixation techniques in the atlas including C1 lateral mass screw and C1 pedicle screw. The shortcomings of C1 lateral mass screw technique and potential risks of bicortical fixation method were recently described; C1 pedicle screw technique with unicortical fixation might overcome these anatomic and clinical drawbacks. However, it is unknown whether the biomechanical characteristics of unicortical C1 pedicle screw are comparable with that of bicortical C1 lateral mass screw. METHODS.: Bicortical or unicortical C1 pedicle screws and C1 lateral mass screws were inserted into 12 adult fresh human C1 specimens. Pullout strength was evaluated using a material testing machine. The construct's stability of bicortical C1 lateral mass screws or unicortical C1 pedicle screws incorporating unicortical C2 pedicle screws was compared with bilateral transarticular screws using another 6 fresh cervical cadaver spines. Pullout strength and biomechanical stability differences were compared statistically. Bicortical C1 pedicle screws provided the biggest pullout strength (1757.0 +/- 318.7 N) of all 4 methods, whereas unicortical C1 lateral mass screws provided the weakest(794.5 +/- 314.8 N). However, there were no statistically significant differences between bicortical C1 lateral mass screws (1243.8 +/- 350.0 N) and unicortical C1 pedicle screws (1192.5 +/- 172.6 N). Furthermore, there was no statistically significant difference of biomechanical construct stability between unicortical C1 pedicle screw-rod constructs and bicortical C1 lateral mass screw-rod constructs. C1 pedicle screws are stiffer than C1 lateral mass screws. Unicortical C1 pedicle screw provided the same pullout resistance and three-dimensional stability as bicortical C1 lateral mass fixation. Although lateral mass screw placement into C1 requires bicortical purchase, pedicle screw insertion into the atlas only requires unicortical fixation.

Internal Fixation of Mandibular Angle Fractures: A Comparison of 2 Techniques

To compare treatment outcomes between rigid extraoral fixation and semirigid intraoral fixation for the management of isolated mandibular angle fractures, and to develop a protocol for successfully managing these fractures in an indigent population. This study involved a retrospective analysis of mandibular angle fracture patients treated at Boston Medical Center from 1999 to 2006. All patients were treated by a single attending surgeon, with oral and maxillofacial surgery residents. Data were collected by a review of pertinent inpatient and outpatient clinic records, and radiographic and laboratory results. The criteria for inclusion into the study comprised: 1) patients with isolated unilateral or bilateral mandibular angle fractures; 2) surgical treatment provided within 7 days of injury via 1 of the 2 following techniques: a) open reduction and internal fixation via an intraoral approach (single monocortical miniplate), or b) open reduction and internal fixation (ORIF) via an extraoral approach (inferior border plate with at least 2 holes on either side of the fracture line and bicortical screws); 3) the presence of decayed, partially bony, or full bony impacted third molars requiring removal at time of surgery; 4) the use of postsurgical maxillomandibular fixation (MMF) for 1 week (extraoral rigid-fixation cases) and 2 weeks (intraoral semirigid-fixation cases) and 5) a 1-week duration of postsurgical oral antibiotic therapy. The patient sample ranged in age from 17 to 55 years, with an average age of 24.8 years. The average follow-up was 12.3 weeks (range, 8 to 64 weeks). In total, 98 fractures were treated with intraoral miniplate fixation, whereas 65 fractures underwent rigid fixation using an extraoral approach. The presence or absence of bone gaps in radiographs immediately after surgery had no correlation with surgical success. None of the patients in either group required further surgical intervention in the operating room. Patients with postsurgical infections were successfully managed with localized intraoral incision and drainage, and oral antibiotic therapy. Isolated mandibular angle fractures can be effectively treated in an indigent population with either intraoral monocortical fixation or extraoral bicortical fixation techniques. Use of a standard protocol involving early surgical management with limited periosteal reflection, concomitant removal of third molars, and short-term maxillomandibular fixation ensures predictable success with a low incidence of complications.

Biomechanical comparison of pull-out force of unicortical versus bicortical screws in proximal phalanges of the hand: A human cadaveric study

Backround Bicortical fixation of proximal phalangeal fractures may damage underlying flexor tendons secondary to drilling and screw protrusion in the dorsal–ventral direction. The aim of this study was to measure and compare the pull-out force of unicortical screws compared to bicortical screws in human cadaveric proximal phalanges to identify optimal configuration for internal fixation. Methods Forty proximal phalanges were harvested. Bicortical and unicortical self tapping 1.7 mm screws were inserted into paired phalanges at the distal and proximal metaphysis and at the mid-diaphysis placed in the dorso-ventral direction. Pull-out force of unicortical and bicortical screws were measured and compared. Findings Bicortical screw pull-out force is significantly higher than that of unicortical screws in the dorsal–ventral direction. Pull-out strength of unicortical screws at the mid-diaphysis was significantly higher than the pull-out strength of bicortical screws at the proximal metaphysis (181.8 N versus 31.5 N, P < 0.0001). Interpretation Diaphyseal fixation is stronger than metaphyseal for both unicortical and bicortical configurations. Unicortical mid-diaphyseal is stronger than bicortical proximal metaphyseal screw pull-out strength. This study provides biomechanical data that may be helpful for individualizing fracture fixation techniques at the proximal phalanx.

Postoperative Stability After Sagittal Split Ramus Osteotomies for a Mandibular Setback With Monocortical Plate Fixation or Bicortical Screw Fixation

This comparative study was performed to analyze mandibular stability after bilateral sagittal split ramus osteotomies for a mandibular setback with a monocortical plate fixation or bicortical screw fixation. A total of 60 patients with a skeletal Class III malocclusion who underwent sagittal split osteotomies and mandibular setback were included in the present study. Among the patients, 30 were osteosynthesized monocortically with a titanium plate, while the other 30 were osteosynthesized bicortically with positioning screws. This retrospective study used cephalometric radiographs taken preoperatively (T0), and at 1 week (T1), 3 months (T2), and 1 year (T3) postoperatively. The linear and angular changes of the cephalometric landmarks of the chin region were measured at each time period, and the changes of each cephalometric landmark were determined for 4 different time intervals: T0 to T1 (Delta T1), T1 to T2 (Delta T2), T2 to T3 (Delta T3), and T0 to T3 (Delta T4). Postoperative changes in mandibular shape were analyzed using a paired t test to determine the stability of fixation methods. The surgical changes (Delta T1) could be characterized as posterior movements of the mandibular body and posterosuperior movements of the chin landmark. The results of the cephalometric analysis at 3 and 12 months postsurgery (Delta T2 and Delta T3) could be characterized as anterosuperior movements of the mandible. In both treatment groups, surgical changes were relatively well maintained. Likewise, analysis of the horizontal and vertical movements of the chin landmarks indicated a similar tendency in both groups. There were no statistically significant differences between the measurements of postoperative changes at each time period after surgery. The findings of our study suggest that there were no significant differences in postoperative changes in mandibular shape in both the monocortical and bicortical fixation groups after sagittal split ramus osteotomy. We concluded that monocortical osteosynthesis using a miniplate could be used to obtain stable postoperative changes after mandibular setback.

Reference marker stability in computer aided orthopedic surgery: A biomechanical study in artificial bone and cadavers

In computer assisted orthopaedic surgery, rigid fixation of the Reference Marker (RM) system is essential for reliable computer guidance. A minimum shift of the RM can lead to substantial registration errors and inaccuracies in the navigation process. Various types of RM systems are available but there is little information regarding the relative stabilities of these systems. The aim of this study was to test the rotational stability of three commonly used RM systems. One hundred and thirty Synbones and 15 cadavers were used to test the rotational stability of three different RM systems (Schanz' screw, RM B and RM C adjustment systems). Using a specially developed testing device, the peak torque sustained by each RM system was assessed in various anatomical sites. Comparison of means for Synbone showed that the RM C was the most stable (mean peak torque 5.60 +/- 1.21 Nm) followed by the RM B system (2.53 +/- 0.53 Nm) and the RM A (0.77 +/- 0.39 Nm) (p<0.01). The order of stability in relation to anatomical site was femoral shaft, distal femur, tibial shaft, proximal tibia, anterior superior iliac spine, iliac crest and talus. Results from the cadaver experiments showed similar results. Bi-cortical fixation was superior to mono-cortical fixation in the femur (p<0.01) but not the tibia (p=0.22). The RM system is the vital link between bone and computer and as such the stability of the RM is paramount to the accuracy of the navigation process. In choosing RM systems for computer navigated surgery surgeons should be aware of their relative stability. Anatomical site of RM placement also affect the stability. Mono-cortical fixation is generally less stable than bi-cortical.

Bicortical Biodegradable Screws for Rigid Fixation of Traumatic Sagittal Split Mandibular Fracture

Rigid fixation is the most important issue in the bone healing process. Although internal metallic bone fixation has become increasingly popular over the past 10 years, the presence of several potential problems of metallic bone implants with the popularity of the use of biodegradable plates and screws for craniomaxillofacial fixation have increased in the last 10 years. Rigid fixation of bony fragments was achieved by bicortical applied biodegradable screws in a patient with a sagittal oblique mandibular fracture. Precise bone reduction was maintained with bicortical applied biodegradable screws in the postoperative period. The postoperative period was uneventful and the patient retained the intraoperatively achieved perfect occlusion within a 9-month follow-up period. In this particular case, the advantages of use of resorbable fixation systems are combined with the advantages of bicortical screw fixation of split osteotomy without sacrificing the stability of rigid fixation.

Loss of Pin Fixation in Displaced Supracondylar Humeral Fractures in Children

Although the results are generally good following pin fixation of supracondylar humeral fractures in children, occasionally there is postoperative displacement. The purposes of the present study were to identify the causes leading to loss of fixation after pin fixation and to present methods for prevention. We evaluated 322 displaced supracondylar humeral fractures that had been treated with percutaneous pin fixation. We examined fracture classification, pin configuration, intraoperative alignment after fixation, change in alignment after fixation, details of additional procedures, and final radiographic and clinical outcomes. Adequate radiographs were available for 279 of the 322 fractures. Eight (2.9%) of the 279 fractures were associated with postoperative loss of fixation; all eight were Gartland type-III fractures. Seven of these eight fractures initially had been treated with two lateral-entry pins, and one had been treated with two crossed pins. In patients with Gartland type-III fractures, loss of fixation was successfully avoided more often when three pins were used (with fixation being maintained in thirty-seven of thirty-seven patients) as opposed to when two lateral-entry pins were used (with fixation being maintained in thirty-five of forty-two patients) (p = 0.01). In all cases, loss of fixation was due to technical errors that were identifiable on the intraoperative fluoroscopic images and that could have been prevented with proper technique. We identified three types of pin-fixation errors: (1) failure to engage both fragments with two pins or more, (2) failure to achieve bicortical fixation with two pins or more, and (3) failure to achieve adequate pin separation (>2 mm) at the fracture site. Postoperative displacement following pin fixation of supracondylar humeral fractures in children is uncommon. In the present series, loss of fixation was most likely to occur when Gartland type-III fractures were treated with two lateral-entry pins. There were no failures when three pins were used. In all cases of failure, there were identifiable technical errors in pin placement. Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

Changes in the inferior alveolar nerve following sagittal split ramus osteotomy in monkeys: A comparison of monocortical and bicortical fixation

We aimed to observe the changes in the inferior alveolar nerve (IAN) after bilateral sagittal split ramus osteotomy (SSRO) using monocortical or bicortical screw fixation. Bilateral SSRO for setback of the mandible was done in 12 monkeys, and monocortical or bicortical fixation was applied on opposing sides of each mandible. Sensory nerve action potentials were tested before and immediately after operation, and at 2, 4, 8, and 12 weeks. Six animals selected randomly were killed at 4 and 12 weeks after the operation. Specimens of nerve were harvested and processed for histological examination and electron microscopic analysis. Obvious prolongation of latency and diminution of amplitude in the IAN were found postoperatively. At 4 weeks after operation, Wallerian degeneration was apparent, and there were signs of axonal regeneration in the nerves. The IAN had more abnormalities of evoked potentials and pathological changes after bicortical than after monocortical fixation. Although considerable recovery was found after both forms of fixation at 12 weeks, the function of the nerve after plate fixation was better than after screw fixation. Our results suggest that the nerve damage during SSRO could be temporary and reversible, and monocortical fixation may result in restoration of the nerve function sooner than bicortical fixation.

An In Vitro Biomechanical Evaluation of Fixation Techniques for Sagittal Split Ramus Osteotomy: Mandibular Advancement and Setback

Statement of the Problem: This comparative study was an analysis of a mandibular stability following bilateral sagittal split ramus osteotomies for mandibular setback with monocortical titanuim plate fixation or bicortical screw fixation. Materials and Methods: A total of 57 patients with skeletal Class III malocclusion who underwent sagittal split osteotomies and mandibular setback were included in this study. Of these patients, 29 patients were osteosynthesized monocortically with titanium plate, and 28 patients were osteosynthesized bicortically with positioning screws. Method of Data Analysis: This retrospective study utilized cephalometric radiographs, which were taken preoperatively, and 1 week, and 1 year postoperatively. Cephalometric parameters – gonial angle (GA), mandiblular plane angle (MPA), SNB, upper facial height ratio (U/F) were measured. Postoperative changes in the mandibular shape were analyzed by Wilcoxon signed-rank test to determine the stability of fixation methods. Results: The postoperative changes in gonial angle and mandibular plane angle tended to increase in both monocortical (changes in GA: 2.20, MPA: 1.19) and bicortical fixation group (changes in GA: 2.18, MPA: 1.17). In addition, the upper facial height ratio showed decrease in both monocortical ( 0.64) and bicortical fixation group ( 0.25). However, SNB showed decrease in monocortical fixation group ( 0.62), and increase in bicortical fixation group (0.30). In statistical analysis, there was no significant difference in postoperative changes in gonial angle, mandibular plane angle, SNB, upper facial height ratio in both patient groups. Conclusion: These findings suggested there was no significant difference in postoperative changes in mandibular shape in both monocortical and bicortical fixation group after sagittal split ramus osteotomy. It was concluded that monocortical osteosysnthesis using miniplate could be used to obtain stable postoperative changes after mandibular setback.

Comparison of volumetric bone mineral density in the tibial region of interest for ACL reconstruction

Adequate tibial bone mineral density (BMD) is essential to soft tissue graft fixation during anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare volumetric bone plug density measurements at the tibial region of interest for ACL reconstruction using a standardized immersion technique and Archimedes' principle. Cancellous bone cores were harvested from the proximal, middle, and distal metaphyseal regions of the lateral tibia and from the standard tibial tunnel location used for ACL reconstruction of 18 cadaveric specimens. Proximal tibial cores displayed 32.6% greater BMD than middle tibial cores and 31.8% greater BMD than distal tibial cores, but did not differ from the BMD of the tibial tunnel cores. Correlational analysis confirmed that the cancellous BMD in the tibial tunnel related to the cancellous BMD of the proximal and distal lateral tibial metaphysis. In conjunction with its adjacent cortical bone, the cancellous BMD of the region used for standard tibial tunnel placement provides an effective foundation for ACL graft fixation. In tibia with poor BMD, bicortical fixation that incorporates cortical bone from the distal tibial tunnel region is recommended.