Bicortical Group Research Articles (Page 1)

This study aimed to evaluate the stability of bimalleolar ankle fracture fixation techniques (bicortical and unicortical lag screw) in simulated progressive rehabilitation with a walking boot. Five matched pairs of lower extremities underwent simulated bimalleolar ankle fracture and were randomly assigned into these 2 repair groups. Each specimen was tested under an axial compression cyclic load test for 10000 cycles at a rate of 1 Hz while the ankle was held in 30° inclination. Radiographic assessments (screw attached lengths [length from screw head to far cortex], fracture gap, and joint clear space [medial, superior, and lateral]) by 3 examiners were performed at 0th, 5000th, and 10000th cycles. Three repeated measurements by each examiner. The overall level of intra-rater reliability for all 3 raters and all measurements were found to be within "moderate" to "excellent" agreement. For radiographic screw loosening and fracture displacement, evaluation found that at no time point did either the bicortical group or the unicortical group meet the minimal threshold of clinical failure which defined as 2-mm of screw displacement or 2-mm of fracture displacement. Both bicortical and traditional unicortical lag screw fixation techniques provide equivalent stability for medial malleolar fractures in a bimalleolar ankle fracture during simulated progressive rehabilitation with a walking boot. This could potentially have clinical benefits in patient care with earlier return to function, prevention of stiffness and loss of range of motion, and decreased muscle atrophy during the postoperative rehabilitation period.Level of Evidence: Level V: bench top testing.

This study aims to evaluate the biomechanical properties of polyaxial screws-rod fixation (PSR) in stabilizing a single vertebral motion unit (VMU) fracture model and to compare the effectiveness of different stabilization techniques such as monocortical and bicortical. A total of 12 thoracolumbar vertebral column specimens were harvested from canine cadavers. These specimens were divided into two groups based on the stabilization technique applied: a monocortical group and a bicortical group. Each group underwent biomechanical testing to assess flexion/extension and lateral bending motions. The range of motion (ROM), neutral zone (NZ), and stiffness were measured for each lumbar VMU in three conditions: intact, fractured with unilateral stabilization, and fractured with bilateral stabilization. In the 3-column fracture model, PSR was unable to restore the ROM of an intact spine in flexion/extension. In lateral bending, only bilateral PSR successfully approached the ROM of the intact spine. Notably, PSR failures were observed in four specimens when applied as monocortical and unilateral stabilization. The findings indicate that even bilateral PSR does not fully restore the intact spine's ROM in canine fracture models, highlighting the need for further research to optimize stabilization techniques. The current study demonstrates that a single 3-column lumbar fracture model VMU cannot be adequately stabilized using PSR in a canine model, suggesting potential limitations in both monocortical and bicortical approaches.

ObjectivesLimited data exists on complications associated with robotic image-based system in knee arthroplasty. This study aims to document complications in robotic arm-assisted knee arthroplasties, and evaluate the system’s safety by comparing two femoral pin insertion methods: bicortical diaphyseal with additional stab wounds, and unicortical metaphyseal placement through the main incision. MethodsAll patients undergoing primary knee arthroplasty with the image-based robotic system (Mako, Stryker, Mako Surgical Corp., Fort Lauderdale, FL, USA) from 1st March 2021 to 31st January 2024 with a minimum follow-up of 2 months were included. Demographics, system and non-system-related complications, as well as outcomes were recorded. Complications were categorized as either major (requiring a second surgical intervention) or minor. ResultsA total of 970 consecutive cases (median age 69.3 years) were analyzed. The unicortical group comprised 651 cases, while the bicortical group 319. The incidence of non-system-related complications was 2.37%, with the most common being joint stiffness (10 cases; 1.03%), followed by lateral femoral condyle fracture (4;0.41%). The overall incidence of system-specific complications was 1.03%. Pin-related femoral fractures occurred in 0.2% of cases, all postoperatively and in the unicortical group. There was no statistically significant difference between the femoral pin insertion-related complication rates among the two groups (0.3% in the unicortical, compared to 0% in the bicortical group; p-value= 0.3). Complications included tibia fracture (0.1%), delayed wound healing (0.2%), superficial wound infection (0.1%), tibia osteomyelitis (0.1%), and “exostosis” (0.2%). The major complications rate was 0.3% and minor 0.7%. ConclusionsMinimal system-specific overall complications indicate that robotic arm-assisted surgery is safe. The bicortical diaphyseal femoral pin insertion method does not increase the complication rates compared to the unicortical metaphyseal method. Level of evidenceIII

External fixation of tibial plateau fractures commonly provides temporary stabilization before definitive fixation with plate and screws. The purpose of this study was to determine if an external fixator pin hole distal to a tibial plate in a synthetic fracture model would increase the risk of fracture after fixation. Another objective was to determine the ideal configuration when placing tibial plate screws near an external fixator pin hole. Thirty synthetic tibiae were tested and evenly divided into 5 groups. Tibial plateau plates were placed with 4 different screw configurations for the distal-most screw near the external fixator pin hole. The 5 groups tested were control (fixation with no external fixator hole), unicortical (distal fixation with a unicortical locking screw), bicortical (distal fixation with a bicortical locking screw), oblique (distal fixation with an oblique cortical screw angled 30° proximally from the external fixator hole), and hole-bridging (hole-bridging fixation in which the plate was placed bridging the external fixator hole). The bone surrogates were potted and tested using an Instron 8874 Testing System. There was a significant difference in failure load among the 5 groups (p = 0.005). The mean peak loads were 1,259 N (control), 835 N (unicortical), 831 N (bicortical), 943 N (oblique), and 993 N (hole-bridging). There was a higher failure load in the control group compared with the bicortical group (p = 0.007) and the unicortical group (p = 0.007). There was no difference in failure load between the control group and the hole-bridging group (p = 0.16) and the oblique group (p = 0.067). External fixator pin holes distal to a tibial plateau plate may increase the risk of tibial fracture through the pin hole. This risk may be mitigated by placing the distal screw oblique and angled proximally away from the external fixator pin hole or by placing the external fixator pin proximally with subsequent bridging of the external fixator pin hole with the plate.

Ankle fractures continue to increase in incidence and severity in an older, more challenging geriatric population. Medial malleolus fixation with partially threaded cancellous 4.0-mm screws, a common fixation method, has been shown to fail due to pullout strength. Subsequent cadaveric models have shown increased pullout strength with the use of bicortical screws. The literature has also demonstrated fairly good clinical results with the use of bicortical screw fixation in a general population as well as in a complicated patient cohort. We sought to compare bicortical fully threaded 3.5-mm screw fixation with unicortical partially threaded 4.0-mm fixation in medial malleolus fractures. The aim was to compare postoperative complications such as screw failure/loosening, nonunion, delayed union, painful hardware, time to union, and time to full weightbearing. Of 292 patients retrospectively reviewed, 126 were included following the inclusion and exclusion criteria. The data included 48 patients in the bicortical group and 78 in the unicortical group, with a mean ± SD combined age of 56.0 ± 18.0 years. Complications occurred in three patients (6%) in the bicortical screw fixation group and in six (8%) in the unicortical group, which did not reach statistical significance. These results show that medial malleolus fixation has an overall low complication rate of 7% total combined, which is comparable with the current literature. We demonstrated no significant differences in complications, weeks to ambulation, or time to union between bicortical and unicortical fixation.

Displaced diaphyseal fractures can be reduced using the push-pull technique, wherein a plate is affixed to the distal fragment of the fracture, a post screw is placed proximal to the plate, and a lamina spreader creates distraction. This study evaluated the load to failure and mechanism of failure of bicortical and unicortical post screws during reduction. Four matched pairs of cadaver legs were subjected to a 2-cm oblique osteotomy simulating a displaced, oblique diaphyseal fracture. A 6-hole compression plate was affixed to the distal fragment with 2 unicortical locking screws, and a 12-mm unicortical or 20-mm bicortical screw was inserted as a post screw proximal to the plate. A lamina bone spreader was used to exert a distraction force between the plate and the post screw. A mechanical actuator simulated the distraction procedure until failure. Maximum applied load, displacement, and absorbed energy were recorded and compared across unicortical and bicortical groups by paired t tests. At maximum load, we found statistically significant differences in displacement (P=.003) and energy absorbed (P=.022) between the two groups. All unicortical screws failed through screw toggle and bone cut-out. Bicortical screws failed through bending, with no visible damage to the bone at the screw site. When diaphyseal fractures are significantly shortened and require a greater distraction force to achieve reduction, bicortical screws demonstrate a higher mechanical load to failure and increased bone loss from the screw-removal site. A unicortical post screw may be used if minimal distraction is needed. [Orthopedics. 2024;47(5):308-312.].

Osteoporosis is a common disease that leads to a reduction in bone density and increases the risk of fractures. Stable surgical treatment is particularly important for these fractures. The aim of this study was to examine the influence of bone density in the area of ​​the proximal ulna on the failure of the fixation technique of K-wires in tension band wiring (TBW). We provided 10 ulna specimens with TBW and biomechanically examined the pull-out strength of bi- and tricortical K-wires. Bone density measurement was performed using qCT. In the paired t-test, the tricortical group showed a significantly higher pull-out strength in relation to bone density than the bicortical group (p = 0.001). Furthermore, the Pearson correlation showed a high influence of bone density on pull-out strength in the tricortical group (r = 0.544), but without significance (p = 0.100).Our work shows that bone density has a direct effect on the pull-out strength of K-wires in TBW. TBW should therefore be used as osteosynthesis technique, especially in young patients with non-osteoporotic bones. In the case of osteoporotic fractures, alternative procedures should be preferred.

Surgical navigation technology has recently become more prevalent for total knee arthroplasty. Surgical navigation typically requires pin placement in the proximal tibia diaphysis to stabilize the bone-tracking hardware, and there have been several recent reports of fractures through these residual navigation pin holes. The objective of this biomechanical study was to determine whether a difference exists in the torsional bone strength of a 5-mm navigation pin hole drilled at a single location in three different orientations: unicortical, bicortical, and transcortical. Biomechanical composite sawbone tibias were used to test four conditions: the intact condition with no holes, a unicortical hole, a bicortical hole, and a transcortical hole through the proximal diaphysis. Seven specimens from each group were tested in external rotation to failure at 1 deg/sec. Torque-to-failure, absorbed energy-to-failure, and rotational angle-to-failure were statistically compared across the four groups. All specimens failed proximally by spiral oblique fractures. No statistical differences were found between unicortical and bicortical groups in torque-to-failure, energy-to-failure, and angle-to-failure. However, both unicortical and bicortical groups were markedly lower in all measures than the intact group. The transcortical group was markedly lower in all measures than the intact group and both unicortical and bicortical groups. An appropriately placed navigation residual pin hole, either unicortical or bicortical, markedly decreases the torque-to-failure, energy-to-failure, and angle-to-failure of the tibia compared with the intact condition in a synthetic sawbones model. No notable difference was detected between the unicortical and bicortical holes; however, an errant transcortical residual navigation pin hole markedly decreases all measures compared with an appropriately placed unicortical or bicortical hole.

BackgroundOptical array placement for robotic-assisted knee replacement introduces the rare, but real risk of periprosthetic fracture. The purpose of this retrospective study was to review the incidence of fracture with the conventional technique of bicortical diaphyseal pin placement. We also evaluated a modified method of unicortical periarticular pin placement to mitigate this risk.MethodsWe reviewed 2603 knee arthroplasties that were performed between June 2017 and December 2019. The conventional bicortical diaphyseal technique was used in 1571 knees (bicortical diaphyseal group) and the unicortical periarticular technique was used in 1032 knees (unicortical periarticular group).ResultsA more than 1-year follow-up revealed that 3 femoral shaft fractures (0.19%) occurred in the bicortical diaphyseal group and no fracture took place in the unicortical periarticular group. There was no array loosening in either group.ConclusionsThe modified unicortical periarticular pin placement is a reliable technique for computer-navigated and robotic-assisted knee arthroplasties. It may be associated with a lower incidence of postoperative femoral shaft fractures, compared to conventional bicortical diaphyseal pinning.

“Stress taper” fixation increases torsional failure strength in a cadaveric femur model

A new intramedullary fixation method for distal biceps tendon ruptures: a biomechanical study

Surgical stabilization of rib fractures is an established form of treatment for complex rib fractures. Plate fixation with bicortical screws placement can cause injury to intra-thoracic organs and pleural irritation from protruding screw tips. The aim of this study is to compare the biomechanical properties of monocortical and bicortical plate fixation for rib fractures using a locking plate system. Ten pairs of fresh-frozen cadaveric ribs were harvested. Native ribs were mounted onto a biomechanical tester and statically loaded to failure to induce a rib fracture. The native stiffness of the rib was measured. Next, the ribs were stabilized using the Synthes MatrixRIB (Johnson & Johnson, USA) locking plate. Left-sided ribs were fixed in a bicortical manner and right-sided ribs were fixed in a monocortical manner. The repaired ribs were subjected to cyclic loading of 50,000 cycles between 2 to 6 N to simulate physiological respiration, followed by static loading at a rate of 10 N/min until failure. The pre and post-repaired stiffness were measured. A high-speed camera was used to record the mechanism of failure. One left-sided rib was omitted from the study because the fracture occurred at the drill hole site. Left-sided ribs demonstrated a mean native stiffness of 10.0 N/mm (SD 3.71) and right-sided 11.92 N/mm (SD 3.57). After plate fixation, pre and post cyclic stiffness was 3.32 N/mm (SD 1.21) and 4.41 N/mm (SD 3.29) for the bicortical group; 3.14 N/mm (SD 1.24) and 3.91 N/mm (SD 1.98) for the monocortical group. There is no statistical difference found between the two groups (P=0.872). Our results show that there is no difference in stability between monocortical and bicortical fixation for rib fractures using a locking plate system. Monocortical fixation is recommended to avoid potential complications.

PurposeThe aim of this study was to determine the influence of anatomical conditions on primary stability in the models simulating posterior maxilla.MethodsPolyurethane blocks were designed to simulate monocortical (M) and bicortical (B) conditions. Each condition had four subgroups measuring 3 mm (M3, B3), 5 mm (M5, B5), 8 mm (M8, B8), and 12 mm (M12, B12) in residual bone height (RBH). After implant placement, the implant stability quotient (ISQ), Periotest value (PTV), insertion torque (IT), and reverse torque (RT) were measured. Two-factor ANOVA (two cortical conditions×four RBHs) and additional analyses for simple main effects were performed.ResultsA significant interaction between cortical condition and RBH was demonstrated for all methods measuring stability with two-factor ANOVA. In the analyses for simple main effects, ISQ and PTV were statistically higher in the bicortical groups than the corresponding monocortical groups, respectively. In the monocortical group, ISQ and PTV showed a statistically significant rise with increasing RBH. Measurements of IT and RT showed a similar tendency, measuring highest in the M3 group, followed by the M8, the M5, and the M12 groups. In the bicortical group, all variables showed a similar tendency, with different degrees of rise and decline. The B8 group showed the highest values, followed by the B12, the B5, and the B3 groups. The highest coefficient was demonstrated between ISQ and PTV.ConclusionsPrimary stability was enhanced by the presence of bicortex and increased RBH, which may be better demonstrated by ISQ and PTV than by IT and RT.

Unicortical fixation has some practical and theoretical advantages over bicortical fixation. Questions have been raised to its adequacy for post-operative mobilization. We hypothesized that fixation using a plate and eight unicortical screws would be as strong as using a plate and four bicortical screws. A total of 40 unicortical and 40 bicortical fixations were compared using a cadaveric metacarpal model. Unicortical fixation was performed using an eight-hole parallel plate and bicortical fixation with a four-hole straight plate. Fixations were tested to failure using four-point bending load. The mean load to failure was 414 N SD 38(SE) for the unicortical group and 296 N SD 29(SE) for the bicortical group. Significant differences between these two constructs were observed. The mean stiffness of the fixation was higher for the bicortical group than the unicortical, although this difference did not reach significance. Unicortical fixation alone is sufficient to enable early post-operative mobilization in a live model.

The incidence of periprosthetic fractures is inevitably increasing. Sufficient stabilisation and proper screw placement next to large-volume implants remains difficult. Modern locking plates allow polyaxial, thus bicortical, screw placement around a prosthetic stem. This study analysed the biomechanical properties of different screw configurations in a locking plate construct of a periprosthetic femoral fracture model. A total of 20 Sawbones were used to stabilise a Vancouver-B1 femoral fracture with a locking plate using either four monocortical screws or three bicortical screws for proximal fixation. These were loaded with an increasing axial compression until failure. Bicortical screw purchase was significantly superior to monocortical regarding load to failure (1,510N ± 284N versus 2,350N ± 212N, p < 0.001) and maximal number of cycles (6803 ± 760 versus 4041 ± 923, p < 0.001). However, the mode of failure in the bicortical group was a severe comminuted fracture pattern as opposed to the monocortical group in which a pull-out of the screws without further damage to the bone was observed. Bicortical screw placement enhances the primary stability in treating periprosthetic femoral fractures. Notably, the mode of failure may limit the salvage options in case of revision surgery.

In vitro experimental study. This study aimed to evaluate the biomechanical properties of bicortically placed and laterally oriented screws, which may represent an alternative approach for challenging sites during direct vertebral rotation (DVR). DVR corrects the transverse plane deformity and the thoracic hump in idiopathic scoliosis. However, instrumentation of the convex side of the scoliosis apex may pose a challenge, not allowing the placement of suitable sized screws in adequate direction. Forty-eight calf vertebrae were used and each vertebral body was instrumented with 1 pedicle screw as follows: unicortical group (n=16), a short screw was unicortically placed and directed laterally; bicortical group (n=16), a short screw was bicortically placed again in lateral direction; control group (n=16), a screw with ideal length and direction was placed. Vertebral bodies were rigidly anchored in a custom device. Each screw was rotated using a constant length lever arm while collecting "force to failure" data. Significantly better results were obtained with bicortical screwing when compared with unicortical screwing (335.4±45.6 vs. 239.5±58.50 N, P<0.001). However, mean "force to failure" was significantly higher in the controls than in the bicortical group (415.8±49.2 vs. 335.4±45.6 N, P<0.001). Bicortical screw placement may provide a biomechanically superior construct than unicortical screw placement for resisting DVR maneuver during scoliosis correction. This technique may represent an effective and safe approach, particularly for the convex side of the scoliosis apex, with increased resistance to derotational forces and decreased risk of bone failure. Further clinical studies are warranted for firmer conclusions.

The stability of mandibular prognathism corrected by bilateral sagittal split osteotomies: a comparison of bi-cortical osteosynthesis and mono-cortical osteosynthesis

Effects of lateral cortical anchorage on the primary stability of implants subjected to controlled loads: an in vitro study

Tension-band wiring is the preferred method of treatment for olecranon fractures and is widely used throughout the world. This technique simply and effectively transforms the forces produced by the pulling of the triceps into forces causing compression of the fracture. Although the procedure is associated with a high union rate, the incidence of skin complications is also high. The most frequent complication is symptomatic prominence of the Kirschner wires (K-wires). The purpose of this retrospective study was to identify the optimal fixation of tension-band wiring in the treatment of olecranon fractures using biomechanical techniques. Sixty-two patients were divided into two groups: a bicortical Kirschner wire group and an intramedullary K-wire group. The migration rate of the K-wires and the union rate of fractured bone were measured in both groups. Achievement of radiographic union was similar in the two groups. However, the K-wire migration rate was higher in the intramedullary K-wire group than in the bicortical K-wire group. With appropriate surgical technique, the use of bicortical K-wires is biomechanically superior to the use of intramedullary K-wires in the treatment of olecranon fractures.

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