Biomechanical comparison of suture-button,bioabsorbable screw,and metal screw for ankle syndesmotic repair: A meta-analysis

BackgroundTo compare biomechanically metal screw fixation to suture-button or bioabsorbable screw fixation for ankle syndesmotic injuries.MethodsA literature search of the comparison studies in Pubmed and Google Scholar was conducted. The biomechanical outcomes of interest were syndesmotic stability in the coronal, sagittal, and axial planes as well as torque and rotation at failure.ResultsA total of 11 cadaveric studies were included. In the suture-button group, coronal displacement (MD 1.72 mm, p = 0.02) and sagittal displacement (MD 2.65 mm, p = 0.0003) were increased relative to the metal screw group. In contrast, no difference was found with axial rotation (MD 0.35 degrees, p = 0.57). Bioabsorbable screws exhibited equivalent failure torque (MD ?3.04 Nm, p = 0.53) and rotation at failure (MD 3.77 degrees, p = 0.48) in comparison to metal screws.ConclusionsSuture-button provide less rigidity when compared to metal screw fixation. They afford flexible syndesmotic micromotion which may more closely resemble a physiological state and be helpful for ligament healing. Bioabsorbable screws demonstrate similar mechanical strength properties to metal screws.     

Comparison of Open Anterior Syndesmotic Repair Augmented With Suture-Tape and Trans-syndesmotic Screw Fixation: A Biomechanical Study

The treatment of syndesmotic injuries with ankle fractures is controversial. The purpose of this study was to compare the biomechanical properties of open anterior syndesmotic repair with those of screw fixation. Ten matched pairs of human cadaver specimens were subjected to open syndesmotic repair or screw fixation. Each specimen underwent initial intact physiologic loading, consisting of 10 cycles of external torsional loading with a peak torque of 7.5 Nm at 0.05 Hz. Injuries of the anterior inferior tibiofibular ligament, tibiofibular interosseous membrane, and deltoid ligament were applied to each specimen. Postfixation cyclic loading consisted of 50 cycles of combined axial and external rotation loading with peak torques of 750 N and 7.5 Nm at a rate of 0.05 Hz. After postfixation loading, each specimen underwent failure loading by external rotation at 0.25 degrees/second. Failure torque and failure angle were measured. The paired t test and Wilcoxon signed-rank test were used to analyze the data. Mean failure torques were 95.63 Nm in the open anterior syndesmotic repair augmented with suture-tape group and 108.61 Nm in the screw group. Mean failure angles were 34.93 degrees in the open anterior syndesmotic repair augmented with suture-tape group and 43.55 degrees in the screw group. These data were not statistically significantly different between the groups (p= .7682 and .4133, respectively). Open anterior syndesmotic repair augmented with suture tape for ankle syndesmotic injury provides similar torsional strength to that of screw fixation. Therefore, this technique can be considered as an alternative treatment option for syndesmosis injury.     

Screw fixation of the syndesmosis alters joint contact characteristics in an axially loaded cadaveric model

BackgroundThe purpose of this study was to quantify the effects of rigid syndesmotic fixation on functional talar position and cartilage contact mechanics.MethodsTwelve below-knee cadaveric specimens with an intact distal syndesmosis were mechanically loaded in four flexion positions (20° plantar flexion, 10° plantar flexion, neutral, 10° dorsiflexion) with zero, one, or two 3.5-mm syndesmotic screws. Rigid clusters of reflective markers were used to track bony movement and ankle-specific pressure sensors were used to measure talar dome and medial/lateral gutter contact mechanics.ResultsScrew fixation caused negligible anterior and inferior shifts of the talus within the mortise. Relative to no fixation, mean peak contact pressure decreased by 6%–32% on the talar dome and increased 2.4- to 6.6-fold in the medial and lateral gutters, respectively, depending on ankle position and number of screws.ConclusionsTwo-way ANOVA indicated syndesmotic screw fixation significantly increased contact pressure in the medial/lateral gutters and decreased talar dome contact pressure while minimally altering talar position.     

Comparison of a novel FiberWire-button construct versus metallic screw fixation in a syndesmotic injury model

BACKGROUND: There is minimal experience with less rigid syndesmotic fixation devices which may approximate the normal distal tibio-fibular mechanics during healing. This study evaluates the ability of a FiberWire-button implant (Arthrex, Naples, FL) to maintain syndesmotic reduction as compared with a metallic screw. METHODS: Ten matched fresh-frozen cadaveric ankle pairs with intact ligaments were tested (12.5 Nm external rotation force) to establish physiologic syndesmotic diastasis. The same force was applied to the ankles after sectioning of the syndesmotic and deltoid ligaments. Within the pairs, each limb was randomized to receive a FiberWire-button implant or a metallic screw (Synthes, Paoli, PA); the ankles were tested for syndesmotic diastasis with progressive external rotation force, from 2.5 Nm to 25 Nm (or failure). RESULTS: There was no significant difference in diastasis amongst pairs with intact or sectioned syndesmosis (p=0.64 and p=0.80, respectively). There was a significantly greater diastasis in the FiberWire-button group at all external rotation loads (p<0.0001). Nine of the ten pairs failed (all through fracture of the distal fibula). There were no hardware failures. The metallic screw group failed at a lower load (mean 15 Nm) compared to the FiberWire-button group (mean 18 Nm, p=0.0004). The metallic screw group maintained syndesmotic reduction up to 5 Nm of force. CONCLUSIONS: The FiberWire-button was unable to maintain syndesmotic reduction of the ankles at any of the forces applied. The ankles fixed with the FiberWire-button demonstrated significantly greater widening of the syndesmosis compared to the screw, at all loads. CLINICAL RELEVANCE: The FiberWire-button implant may not maintain adequate ankle syndesmotic reduction in the immediate post-operative period relative to a metallic screw.     

Biomechanical comparison of screw,tightrope and novel double endobutton in the treatment of tibiofibular syndesmotic injuries

BackgroundAdequate reduction and stabilization of the syndesmosis are significant to prevent early degeneration of the ankle joint and get better clinical outcomes. However, the routine surgical methods have diffierent limitations. The purpose of this study was to develop a novel double Endobutton fixation to treat the distal tibiofibular syndesmotic injuries, and determine whether the novel double Endobutton fixation demonstrates a better biomechanical property compare with the intact syndesmosis, the screw fixation and the Tightrope fixation.MethodsTwenty-four normal fresh-frozen ankle specimens with a mean age of 42 ± 8 (range, 28–62) years were randomly divided equally into four groups: (1) the intact group, (2) the screw group, (3) the Tightrope group, (4) the Endobutton group. 3D printer technology was used to establish the personalized distal tibiofibular syndesmotic navigation modules to determine the accurate bone tunnel. Axial loading was applied in five ankle positions: neutral position, dorsiflexion, plantar flexion, varus and valgus. Rotation torque was applied in two ankle rotation of the neutral position: internal and external.ResultsIn most situations, the displacements of the intact group were larger than the screw group, the Tightrope group and the Endobutton group (P < .05), and the displacements of the screw group were smaller than other three groups (P < .05). The displacements of the double Endobutton group were slightly larger than the Tightrope group but no significant differences were found between these two groups except in the dorsiflexion position of axial loading experiments (P < .05). The novel double Endobutton fixation was steadier than intact syndesmosis and more micromotional than screw fixation.ConclusionOur study demonstrated that the novel double Endobutton can be considered as the better fixation in treatment of distal tibiofibular syndesmotic injuries.Level of EvidenceLevel III, retrospective comparative study     

Motion of the fibula relative to the tibia and its alterations with syndesmosis screws: A cadaver study

BackgroundThe motion of the fibula in relation to the tibia is coupled on the motion of the talus in the ankle joint. Several authors investigated this motion with different methods. An injury of the elastic fixation of the fibula to the tibia and its treatment with the syndesmotic set screw has an impact on this motion.MethodsThe motion of the fibula relative to the tibia was measured in eight embalmed human above the knee amputated cadaver specimens using a 3D-motion analysis system. The relative motion was measured from 50° of plantar flexion to 30° of dorsiflexion. Experiments were performed in the following conditions: without fixation and intact ligaments, after sectioning of the four syndesmotic ligaments and the interosseous membrane, and application of either a tricortical screw, or a quadricortical screw or two quadricortical screws.ResultsConcordant movements of the lateral malleolus were a medial translation during plantar flexion, external rotation around the sagittal axis during plantar and dorsiflexion. The motion of the proximal fibula was smaller and more variable than in the distal part. After sectioning of the syndesmosis the range of motion, compared to the intact state increased, particularly in translation along the transversal (118%), sagittal (160%) and the longitudinal (136%) axis and in axial rotation (145%). Syndesmotic screws reduced the range of motion in transversal (p < 0.006) and sagittal translation (p < 0.011) and axial rotation.ConclusionThe small relative motion of the tibia and fibula is increased by syndesmotic injuries. Syndesmosis screws significantly limit this increased relative motion below physiologic values, which makes it necessary to remove the screws before flexion in the ankle joint is performed.     

Tibiotalar contact and fibular malunion in ankle fractures. A cadaver study.

Six cadaveric ankles were dissected, preserving medial and lateral ligaments; an axial load of 455N was applied to the tibia supported by the foot and ankle. The unconstrained tibia was moved through 20 degrees of flexion and extension to simulate walking. The tibiotalar contact area was defined using carbon black suspension, recorded photographically, and measured using computerized area analysis. Osteotomy of the distal fibula was performed and fixed with a specially modified plate; a selection of plates provided fixation with 0 degrees or 30 degrees of external rotation in combination with 0 or 2 mm of shortening. The contact area was measured for each of the plates and after division of the deltoid ligament. There were greater than 30 percent decreases in tibiotalar contact with both fibular shortening and external rotation, doubled with a divided deltoid ligament. Anatomic restoration of both fibular length and rotation is essential for normal ankle mechanics. The deltoid ligament has crucial effects on the stability of the ankle mortise.     

Biomechanical evaluation of stand-alone lumbar polyether-ether-ketone interbody cage with integrated screws

Background contextStand-alone interbody cages with integrated screws potentially provide a biomechanically stable solution for anterior lumbar interbody fusion (ALIF) that alleviates the need for additional exposure for supplemental fixation, thereby reducing the chance of additional complications and morbidity.PurposeTo compare the stability of a stand-alone anterior interbody fusion system with integrated fixation screws against traditional supplemental fixation methods and to evaluate the difference between three and four fixation screws in the stand-alone cage.Study designIn vitro cadaveric biomechanical study.MethodsEight cadaveric lumbar spines (L2–sacrum) were tested using a flexibility protocol consisting of three cycles to ±7.5 Nm in flexion-extension, lateral bending, and axial rotation. The conditions evaluated were intact spine; polyether-ether-ketone cage (zero integrated screws) at L4–L5; cage (zero screws)+bilateral pedicle screws (PS); cage (three screws); cage (four screws); cage (zero screws)+anterior plate; and cage (three screws)+spinous process plate. Motion at the index level was assessed using an optoelectronic system.ResultsThe cage without integrated screws reduced the motion in flexion-extension and lateral bending (p<.001) compared with that in the intact spine. In axial rotation, mean range of motion (ROM) was 8% greater than in intact spine (p>.962). The addition of three integrated screws reduced ROM significantly compared with the cage without screws in all motion planes (p<.001). A fourth screw had no statistically significant effect on the ROM, although there was a trend toward less motion with four screws compared with three. In flexion-extension, the cage with three integrated screws and the spinous process plate was the most rigid condition. There was no significant difference from the bilateral PS (p=.537); however, this was more rigid than all other conditions (p<.024). The most stable condition in lateral bending and axial rotation was the cage with bilateral PS. In lateral bending, the cage (three or four screws) was not significantly different from the cage with anterior plate or the cage (three screws) with spinous process plate fixation; however, only the latter condition was statistically comparable with bilateral PS. In axial rotation, there were no significant differences between the conditions that included integrated screws or supplemental fixation (p>.081).ConclusionsBiomechanical testing revealed that the stand-alone cage with integrated screws provides more immediate stability than a cage alone and provides equivalent stability to ALIF constructs with supplemental fixation in lateral bending and axial rotation. Additional flexion-extension rigidity of the anterior cage maybe realized by the addition of a spinous process plate that was found to be as stable as supplemental bilateral PS.     

Stability of an ankle arthrodesis fixed by cancellous-bone screws compared with that fixed by an external fixator. A biomechanical study.

Twenty-three fresh-frozen human specimens were subjected to ankle arthrodesis and fixation with two cancellous-bone screws. The specimens were then subjected to four newton-meters of manually applied tibial torque, plantar flexion-dorsiflexion moment, and medial-lateral bending moment; relative rotation between the tibia and the talus was recorded for each mode of testing. A Calandruccio triangular compression device was then applied to threaded pins penetrating the tibia and talus, the screws were removed, and the test sequence was repeated. Tibiotalar motions recorded with both systems of fixation were markedly affected by the quality of the bone. When less than 2 degrees of total tibiotalar rotation was recorded in response to four newton-meters of manually applied internal-external tibial torque, all specimens demonstrated less torsional rotation with the screw fixation than with the external fixator. The mean rotations produced by medial-lateral bending moment were equivalent for both systems of fixation. When torsional rotations with the use of screw fixation were greater than 2 degrees, all specimens demonstrated more torsional rotation with the screws than with the external fixator, and all but one specimen had more medial-lateral rotation with the screws than with the fixator. For applied plantar flexion-dorsiflexion moment, twenty-two of the twenty-three specimens demonstrated more rotation with the Calandruccio fixator than with the screws; this was due in part to motion permitted at the hinge points of the frame itself.     

Acute distal tibiofibular syndesmosis injury: a systematic review of suture-button versus syndesmotic screw repair

Purpose

Recently, a new suture-button fixation device has emerged for the treatment of acute distal tibiofibular syndesmotic injuries and its use is rapidly increasing. The current systematic review was undertaken to compare the biomechanical properties, functional outcome, need for implant removal, and the complication rate of syndesmotic disruptions treated with a suture-button device with the current ''gold standard'', i.e. the syndesmotic screw.

Method

A literature search in the electronic databases of the Cochrane Library, EMbase, Pubmed Medline, and Google Scholar, between January 1st 2000 to December 1st 2011, was conducted to identify studies in which unstable ankle fractures with concomitant distal tibiofibular syndesmotic injury were treated with either a syndesmotic screw or a suture-button device.

Results

A total of six biomechanical studies, seven clinical full-text studies and four abstracts on the TightRope system, and 27 studies on syndesmotic screw or bolt fixation were identified. The AOFAS of 133 patients treated with TightRope was 89.1 points, with an average study follow-up of 19 months. The AOFAS score in studies with 253 patients treated with syndesmotic screws (metallic and absorbable) or bolts was 86.3 points, with an average study follow-up of 42 months. Two studies reported an earlier return to work in the TightRope group. Implant removal was reported in 22 (10%) of 220 patients treated with a TightRope (range, 0–25%), in the screw or bolt group the average was 51.9% of 866 patients (range, 5.8–100%).

Conclusion

The TightRope system has a similar outcome compared with the syndesmotic screw or bolt fixation, but might lead to a quicker return to work. The rate of implant removal is lower than in the syndesmotic screw group. There is currently insufficient evidence on the long-term effects of the TightRope and more uniform outcome reporting is desirable. In addition, there is a need for studies on cost-effectiveness of the treatment of acute distal tibiofibular syndesmotic disruption treated with a suture-button device.     

经寰枢关节间隙螺钉和寰椎椎板钩内固定的力学稳定性

目的评价双侧经寰枢关节间隙螺钉和寰椎椎板钩内固定的力学稳定性。方法将6具新鲜尸体颈椎标本（包括枕骨基底部和C1-C4颈椎节段）置于1．5Nm载荷下，测量C1，2节段的三维运动范围（range of motion，ROM）。标本依Gallie内固定、双侧经寰枢关节间隙螺钉和Gallie内固定、双侧经寰枢关节间隙螺钉内固定、双侧经寰枢关节间隙螺钉和寰椎椎板钩内固定、双侧寰椎侧块螺钉和枢椎椎弓根螺钉内固定的顺序实施固定，每次固定后测量三维运动范围。结果包含经寰枢关节间隙螺钉的内固定组在旋转和侧屈方向上具有最小的ROM，其中双侧经寰枢关节间隙螺钉和寰椎椎板钩内固定组在屈伸运动方向上也具有最小的ROM。寰椎侧块螺钉和枢椎椎弓根螺钉内固定组在旋转方向上ROM大于单纯经寰枢关节间隙螺钉内固定组，但在侧屈和屈伸方向上接近经寰枢关节间隙螺钉，差异无统计学意义；其在侧屈和旋转方向上ROM均小于Gallie内固定组，差异有统计学意义。结论双侧经寰枢关节间隙螺钉和寰椎椎板钩“三点”内固定具有最强的生物力学稳定性。虽然双侧寰椎侧块螺钉和枢椎椎弓根螺钉内固定在生物力学稳定性上不及“三点”内固定，但明显优于Gallie内固定。     

Ankle mortise stability in Weber C fractures: indications for syndesmotic fixation

A Weber type C ankle fracture was sequentially reproduced in 12 cadaver lower extremities and an external rotation torque was applied at each interval. The fractures were then repaired in staged fashion and the rotational stability of the mortise evaluated. Maximum external rotation of the talus within the mortise averaged 7.7 degrees in the intact ankle and increased by 311% to 31.8 degrees after creation of a Weber C injury. Rigid fixation of the fibular fracture restored 32% of the rotational stability, whereas isolated fixation of the medial malleolus reconstituted 57%. Fibular fixation combined with a syndesmotic screw restored 51% of original stability, and the addition of medial malleolar fixation improved stability to 101%. Bimalleolar fixation without a syndesmotic screw yielded 73% of the original rotational stability. The results of this study suggest that when rigid medial and lateral osteosynthesis can be achieved, syndesmotic fixation may not be necessary.     

Malleolar tips as reference points for positioning of syndesmotic screw: A preliminary CT based analysis

PurposeThe risk of malpositioning of the syndesmotic screws is very high. A lack of standard radiological or physical references for accurate syndesmotic screw placement is a potential contributing factor in syndesmotic screw malpositioning. Malleolar tips are clinically as well as radiologically appreciable bony references. The purpose of this preliminary CT based study was to investigate the axial relations of the central syndesmotic axis with the malleolar tips.MethodsCT based studies of uninjured adult ankle joints with intact syndesmosis, conducted over a six months period were analysed. The axial differences between the coronal plane along the malleolar tips and that along the central syndesmotic axis in the axial plane were measured. Gender-based variations were also analyzed.ResultsA total of 70 CT studies were analyzed, and the axial difference between the malleolar tips based coronal plane and that along the central syndesmotic axis was observed to be 3.70 ± 5.61°. The male and female measurements were comparable.ConclusionBeing in a static relation to the syndesmosis independent of the foot position and the limb rotation, the malleolar tips can be reliably used as references for directing syndesmotic screw in the axial plane. A knowledge of this axial difference between malleolar tips and central syndesmotic axis can help surgeons in an accurate syndesmotic screw placement.     

Clinical outcomes of an olive wire and external fixator versus a metallic screw in the treatment of inferior tibiofibular syndesmosis injuries in ankle fractures

BackgroundMetal screws are the most widely used in treating syndesmotic injuries, but failure and the rigidity of the screws can threaten the success of the treatment and increase the cost of care. We have provided an alternative with an olive wire and external fixator(OWEF) used for syndesmotic fixation.MethodsA retrospective longitudinal follow-up study was conducted. From February 2011 to January 2018, 58 of 72 patients with ankle fractures and associated syndesmotic disruption were treated with either screw or OWEF fixation. The costs, complications, and clinical outcomes using Olerud-Molander score and Visual Analog score in screw and OWEF fixation group were compared.ResultsWe found the severity of the injury, BMI of the patients and the different fixation methods were determinants of the complications and clinical outcomes. But if no malreduction of the syndesmosis was present, no difference in clinical result was detected.ConclusionThe OWEF method appeared to be at least equally functional and effective to screw fixation while maintaining possible lower complication rate.Levels of clinical evidenceLevel 3     

An anatomical way of treating ankle syndesmotic injuries

Treatment of tibiofibular syndesmotic ankle injury remains controversial in regard to the best method, although surgeons agree that the goal of treatment is reduction and operative stabilization. Ideally, the implant should stabilize the syndesmosis and allow physiologic micromotion and early mobilization, and conventional screws are limited in this regard. We reviewed use of the Ankle TightRope(?) fixation device for repair of syndesmotic injuries. From April to September 2006, 16 patients with evidence of syndesmotic injury were treated by means of ankle fracture open reduction with internal fixation, combined with use of the Ankle TightRope(?) device for repair of the syndesmosis. The mean age of the 16 patients was 36.6 ± 16.71 (range 15 to 69) years; they were followed up for at least 2 years. Mean follow-up duration was 26 ± 3.94 (range 24 to 38) months. The mean American Orthopaedic Foot and Ankle Society score at 2-year follow-up was 86.88 ± 11.49 (range 48 to 100). The mean time to full weight-bearing was 4.5 ± 0.87 weeks. Two (12.5%) patients had postoperative superficial wound infections, each of which was treated with oral antibiotics. One (6.25%) patient had the TightRope(?) removed because of irritation from the knot. There was no failure of syndesmotic fixation, despite early weight-bearing in the postoperative phase. The results of this case series indicate that tibiofibular syndesmosis repair with the Ankle TightRope(?) yields satisfactory results.     

Comparison of the syndesmotic staple to the transsyndesmotic screw: a biomechanical study

BACKGROUND: Controversy still exists about treatment of syndesmotic injuries. This study compared the fixation strengths and biomechanical characteristics of two types of ankle fracture syndesmotic fixation devices: the barbed, round staple and the 4.5-mm cortical screw. METHODS: Cadaveric testing was done on 21 fresh-frozen knee disarticulation specimens in biaxial servohydraulic Instron testing equipment. Submaximal torsional loads were applied to specimens in intact and Weber C bimalleolar fracture states. The specimens were then fixed with one of two techniques and again subjected to submaximal torsion and torsion to failure. Biomechanical parameters measured included tibiofibular translation and rotation, maximal torque to failure, and degrees of rotation at failure. RESULTS: Compared to the intact state before testing, the staple held the fibula in a more anatomic position than the screw for mediolateral and anterior displacements (p < 0.01). With submaximal torsional testing, the staple restored 85% of the tibiofibular external rotation and all of the posterior translation values as compared to the intact state. The screw resulted in 203% more tibiofibular medial translation and 115% more external rotation than the intact state. The degree of tibial rotation during submaximal torsional loading was restored to within 15% of intact values but was 21% less with the screw. There was no statistical difference between the screw and staple when tested in load to failure. Tibiotalar rotation at failure was statistically different with the staple construct, allowing more rotation as compared to the screw. CONCLUSION: The staple restored a more physiologic position of the fibula compared to the syndesmotic screw. Both provided similar performance for the load to failure testing, while the screw reduced tibial rotation more after cyclic loading. There was more tibial rotation before failure for the staple, suggesting a more elastic construct. This study provides biomechanical data to support the clinical use of the syndesmotic staple.     

In vitro biomechanical comparison of transpedicular versus translaminar C-2 screw fixation in C2-3 instrumentation

OBJECT: In instrumentation of the upper cervical spine, placement of pedicle screws into C-2 is generally safe, although there is the potential for injury to the vertebral arteries. Owing to this risk, translaminar screws into C-2 have been used. The aim of this study was to compare the stability of the in vitro cadaveric spine using C-2 laminar compared with C-2 pedicle screws in C2-3 instrumentation. METHODS: Eight fresh frozen human cadaveric cervical spines (C1-6) were potted at C1-2 and C5-6. Pure moments in increments of 0.3 Nm to a maximum of 1.5 Nm were applied in flexion, extension, right and left lateral bending, and right and left axial rotation. Each specimen was tested sequentially in three modes: 1) intact; 2) C2 pedicle screw-C3 lateral mass fixation; and 3) C2 laminar screw-C3 lateral mass fixation. The sequence of fixation testing was randomized. Motion was tracked with reflective markers attached to C-2 and C-3. RESULTS: Spinal levels with instrumentation showed significantly less motion than the intact spine in all directions and with all loads greater than 0.3 Nm (p < 0.05). Although there was no significant difference between C2 pedicle screw-C3 lateral mass fixation and C2 laminar screw-C3 lateral mass fixation, generally the former type of fixation was associated with less motion than the latter. CONCLUSIONS: When pedicle screws in C-2 are contraindicated or inappropriate, laminar screws in C-2 offer a safe and acceptable option for posterior instrumentation.     

Numerical evaluation of the mechanical properties of a novel expandable intramedullary nailing: A new alternative to standard interlocking nailing

Introduction: There has been a great effort in preventing the disadvantages of distal locking in intramedullary nailing to date. From this scope, a novel expandable nail fixation eliminating distal locking screws has been designed. The primary aim of this numerical parametric study is to investigate mechanical behavior of expandable nail fixation on the fractured femur model under different contact parameters which are effective in maintaining the nail position and to specify the appropriate values of these contact parameters for a safe fixation. The second aim is to compare mechanical behavior of the expandable nail fixation with the standard interlocking nail fixation.Materials and Methods: The expandable nail has three wedges which are responsible for distal fixation by compressing the medullary canal in the radial direction. 4th generation Sawbones femur model was used as bone model. A transverse osteotomy with 20 mm gap was created to simulate a subtrochanteric fracture. The fixations have been examined under axial compression with 1200 N and torsion with 7 Nm. In the parametric study, the tightening torque and static friction coefficient in wedge-canal contact were selected as contact parameters. The outputs were stiffnesses of the fixations, equivalent von-Mises stress distribution on the models, and load sharing between the canal and distal locking elements.Results: The results of the parametric study showed that the model with the tightening torque of 3 Nm and friction coefficient of 0.7 was the safest. The load borne by wedges is generally prone to increase with increased tightening torque and friction coefficient. The both fixations showed close stiffness and stress values.Conclusion: The tightening torque of the wedge locking mechanism is directly effective in maintaining the nail position constant in canal, and the safety of the fixation is better ensured with increased tightening torque but stress states on bone must be carefully evaluated. The expandable nail provided comparable results to standard interlocking nails with respect to the fixation stiffness, stress, and contact forces. The expandable nailing may be evaluated as an alternative in the fractures of long bones in the case that the numerical results are supported by future experimental studies.     

Screw versus suture button in treatment of syndesmosis instability: Comparison using weightbearing CT scan

BackgroundThe superiority of screw or suture button fixation for syndesmotic instability remains debatable. Our aim is to compare radiographic outcomes of screw and suture button fixation of syndesmotic instability using weight bearing CT scan (WBCT).MethodsTwenty patients with fixation of unilateral syndesmotic instability were recruited and divided among two groups (screw = 10, suture button = 10). All patients had WBCT of both ankles ≥12 months postoperatively.ResultsIn suture button group, injured side measurements were significantly different from normal side for syndesmotic area (P = 0.003), fibular rotation (P = 0.004), anterior difference (P = 0.025) and direct anterior difference (P = 0.035). In screw group, syndesmotic area was the only significantly different measurement (P = 0.006).ConclusionWhile both screw and suture button didn’t completely restore the syndesmotic area as compared to the contralateral uninjured ankle, external malrotation of the fibula was uniquely associated with suture button fixation.Level of EvidenceIII Retrospective Cohort Study     

Biomechanical Analysis of Tibiofibular Syndesmosis Injury Fixation Methods: A Finite Element Analysis

The optimal treatment strategy after syndesmotic injuries is still controversial. In our study, we aimed to evaluate ideal fixation method in syndesmotic injury by using finite element analysis method. A 3D SolidWorks model file was created by taking computed tomography (CT) images of the area from the right foot base to the knee joint level of a healthy adult male. The intact model, injury model, and 8 different fixation models were created that 3.5 mm screw and suture-button were used in. The models were compared in terms of lateral fibular translation, posterior fibular translation and external rotation of fibula compared to tibia and stress values occurred on screws and suture-buttons. In the hybrid-1 model, lateral fibular translation and external fibular rotation values were obtained as close to the intact model. Von Mises stresses occurred in the screw (435.7 MPa) and suture-button (424.7 MPa) that used in hybrid-1 model was more than single screw at 4 cm model (316.8 MPa) and single suture-button at 2 cm model (160.7 MPa). In the Hybrid-1 model, the screw compensates for posterior fibular translation and external fibular rotation, while the suture-button compensates for lateral fibular translation. Also, the effect of the distal suture-button preventing diastasis in case of proximal screw failure, it was concluded that the hybrid-1 model can be used as a good treatment alternative in the surgical treatment of distal tibiofibular syndesmotic injuries.