background : Intramedullary breeze through is the “ gold standard ” discussion mood of diaphyseal fractures of the tibia. however, when the same method is used for extra-articular fractures of the proximal tibia, assorted problems may occur, like malalignment, loss of reduction, and non-union. The objective of the deliver biomechanical study was to compare the stability of six tibial nails when these are used for the treatment of mentally ill, extra-articular, proximal tibial fractures. Methods : Thirty composite tibia models were divided into six groups, and a match issue of nails from six manufacturers ( Citieffe, Braun Aesculap, Orthoselect, Orthofix, Stryker, and Depuy Synthes ) was implanted in each group. The maximum count of proximal screws was used for each specimen, and a proximal gap osteotomy was performed. Each bone model was then submitted in dynamic, followed by inactive loading, and the passive manufacture stiffness was calculated, representing the specimen ’ sulfur rigidity. Furthermore, for each specimen, the force needed to cause a displacement of more than one millimeter at the fault locate was calculated. Results : Stiffness values of a firm collar with two proximal screws and a cannulate smash with five screws were significantly higher compared to all other groups. On the other bridge player, a titanium cannulated collar with three screws showed the lowest rigidity.

decision : upstanding nails provide more inflexibility compared to cannulated ones, and the maximal number of proximal screws in all possible directions should be used in ordain to achieve maximum stability. HIPPOKRATIA 2019, 23 ( 2 ) : 58-63. Keywords:

Intramedullary nail, tibia fracture, proximal, screws, biomechanical study


Intramedullary nail remains the treatment of choice for unstable tibial cheat fractures due to excellent mend rates, with minimal procedure-related complications 1, 2. As a resultant role of this reach in popularity, the indications for intramedullary nail down have expanded to more proximal and more distal fracture patterns. soon after the execution of intramedullary nail of proximal and distal tibial fractures, problems such as unacceptable malalignment have surfaced 3. This is chiefly due to the flared trilateral human body of the proximal and distal metaphysis, which prevents cortical contact of the collar. Regarding the distal tibia, it has been shown that it is necessary to achieve an acceptable reduction using meticulous surgical techniques, followed by at least two distal locking screws in order to have the optimum bone-implant interface, which will lead to union 4, 5. treatment of extra-articular proximal tibial fractures with an intramedullary smash remains challenging. Valgus malalignment and anterior angulation of the proximal fragment are coarse deformities that led some authors to advise against the use of intramedullary nails for the treatment of these fractures 6. several reasons for this publish have been identified, such as the anteriorly directed pull of the extensor muscle mechanism of the knee, the mismatch between the diameter of the smash and the metaphysis at this flush, the inappropriate entry point and inability to use at least two proximal locking screws in the short proximal segment 7. assorted adjustments to the standard intramedullary technique have been proposed, which aim to achieve and maintain an acceptable reduction. These include the use of blocking-poller screws 8, a more lateral entrance point 9, nailing with the stifle in an extend status 10, suprapatellar nailing 11, and modification of the proximal interlacing screws position, numeral and orientation course 12. The drive of the stage biomechanical cogitation was to evaluate and compare the properties and behavior of six advanced, commercially available intramedullary nails for the treatment of proximal extra-articular tibial fractures .

Materials and methods

Thirty composite bone models of the tibia were used ( Model number 3401, 4th generation composite bone, Sawbone, Sawbones Europe AB Malmo Sweden ). This validated cram model has been previously used for several biomechanical studies, and its mechanical properties are alike to the tibia of a healthy adult without osteporosis 13, 14. Six commercially available tibial intramedullary nails were used. They were all nine mm in diameter, with distance ranging from 335 to 360 millimeter. The nails were composed of stainless steel steel or titanium admixture, were solid or cannulated, and they had diverse configurations of proximal and distal lock options. The distal holes ranged from two to four, and the proximal ones from two to five. The orientation of the proximal screws besides varied, from the authoritative mediolateral to a combination of mediolateral, external oblique muscle, and anteroposterior ( ). The experiments took place between 2014 and 2017 at the laboratories of the Mechanical Engineering Department, School of Engineering, International Hellenic University, Serres, Greece. execution of this experimental study was approved by the General Assembly of the School of Medicine of the Aristotle University of Thessaloniki. Ethical approval was not required since there are no humans or animals involved in the experiments merely model and material test .

Table 1

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Object name is hippokratia-23-59-i0001.jpgOpen in a separate window Specimen homework The sawbones were divided into six groups of five, and each group was prepared with one of the six nails. The bone model was stabilized using a custom-made clamp, and an identical introduction point was established in all models based on similar landmarks on the tibial tableland. The medullary duct was entered using either an owl or a drill bite, depending on the surgical proficiency suggested by the manufacturer, followed by a guidewire. The canal of all the bone models was reamed up to 10.5 mm in 0.5 increments, and the breeze through was inserted until the proximal goal of the implant stayed hot flash to the surface of the sawbone. Each nail was locked proximally with the maximum phone number of screws it allowed. Distally, all nails were locked with two screws, which were inserted either with the jig provided by the manufacturer or with a freehand technique under trope intensification 15. At this point, all specimens were radiographed with an anteroposterior and lateral opinion. All specimens were marked at a distance of eight and ten centimeter below the articular surface of the tibial tableland. A two curium osteotomy was performed, using a handsaw. This osteotomy represents the worst-case scenario in terms of stability, simulating a 42-C3 fracture, according to the AO categorization of long bones fractures, as in the technique used by Horn et aluminum and Agathangelidis et alabama 4, 16 – 18. mechanical examination All specimens undergo biomechanical load in two modes. The beginning modality was fatigue duty testing with low, character loads for 100,000 cycles, and the second mode was axile static load with higher loads ( ) .An external file that holds a picture, illustration, etc.
Object name is hippokratia-23-60-g0001.jpgOpen in a separate window For the beginning depart of the experiment, the proximal and distal ends of the specimens were potted in a hollow-formed polyamide fastness, filled with fiberglass-reinforced resin. The molds did not encapsulate any screws and ensured that the load was shared evenly on the tibial tableland and plafond surfaces. The custom-made fixtures were marked at a point 23 millimeter medially to the anatomic axis of the tibia proximally and 9 mm medially to the same axis distally. This cancel reproduces the expect top out cargo vector during the pace motorbike 19, 20. The specimens were compressive cyclic loaded on the tire testing machine ( Instron 8801, Instron, Pfungstadt, Germany ) for 100,000 cycles. All the fatigue tests were conducted in load-controlled mode with a haversine load of 2 Hz frequency. The dynamic load, ranging from 200 N to 450 N, was imposed upon a electrostatic preload of 150 N in order to ensure that the specimen ’ second flexure would not lead to contact rest between the specimen and the regular. The load forces represent partial weight-bearing for a subject weighing 65 to 85 kg and were adapted from previous studies 21. During the implementation of the tire tests in every 10.000 cycles, coincident load and displacement data skill were carried out. The quantitative consequence of all tests was the account value of active awkwardness, representing the specimen ’ second rigidity. The cargo and data acquisition protocol was used before by Goett et alabama 22. For the second part of the experiment, the specimens mounted on the custom-made fixtures were loaded on the compression testing machine ( Instron Satec 1200, Instron, Pfungstadt, Germany ), this time with the lode pass along the anatomic axis of the tibia. The specimens were statically loaded for three cycles, with forces ranging from 100 N to 1200 N. In order to calculate each specimen ’ south stiffness, data skill was performed during the fourth cycle. statistical psychoanalysis descriptive statistics are reported as means ± standard deviation. Normality assumptions were evaluated using the Shapiro-Wilk test. One-way ANOVA was used for the comparison of means of autonomous measurements, while Generalized Estimating Equations ( GEE ) model was used for the assessment of the effects of independent factors/covariates on longitudinal measurements. The Sidak correction was used to adjust for multiple screen. Data analysis was performed with Stata 13.1 ( Stata Corp., College Station, TX ).


Fatigue testing During the first mode of the experiment, data skill was performed every 10,000 cycles while the awkwardness of the manufacture was besides calculated. For each specimen, a comparison of the stiffness of every step up to 100,000 cycles was performed in arrange to identify any irregular behavior or mechanical failure of the manufacture. Each specimen ’ south mechanical properties remained stable up to 100,000 cycles without any bankruptcy or abnormality. The average stiffness for each group was compared pairwise in a post hoc fashion ( ). Statistically meaning differences between groups were detected at the 5 % level ( F =36.8, df =5.19, phosphorus < 0.001 ). Results of the post hoc procedure suggest that groups D and E differ from all others, with D having the highest values and E the lowest. The average stiffnesses of Groups F and B are very close ; the same holds for groups A, B, and C. These results are illustrated in .An external file that holds a picture, illustration, etc.
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Table 2

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Object name is hippokratia-23-60-i0001.jpgOpen in a separate window inactive load The average stiffness for each group was recorded in a longitudinal place. Generalized estimate Equations ( GEE ) model was used for inference as a solution. Group D differs from all early models in this set ( p < 0.05 ), giving the highest values, while group E differs from F only ( p =0.024 ). In all early comparisons, there were no statistically meaning differences ( phosphorus > 0.05 ) ( ; ) .An external file that holds a picture, illustration, etc.
Object name is hippokratia-23-61-g0002.jpgOpen in a separate window

Table 3

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Object name is hippokratia-23-60-i0002.jpgOpen in a separate window For each group of specimens, we additionally calculated the force needed to reach the restrict of one millimeter of shift at the fracture site. Group D recorded the highest value. A, B, and C did not differ importantly amongst them, E was alike to C but had importantly lower value both from A and B. Finally, group F had exchangeable values to A and B but differed from all others ( ) .An external file that holds a picture, illustration, etc.
Object name is hippokratia-23-61-g0003.jpgOpen in a separate window


In the present cogitation, we experimented with the biomechanical behavior of six different intramedullary nails. Solid stainless sword nails, with two oblique screws and cannulated titanium nails with five proximal screws, outperformed all other nails in terms of stability. The nails were implanted in composite tibia bone models, which have been wide used in biomechanical studies 23. Their mechanical properties are reproducible and predictable compared to cadaveric tibia ; they are available in large numbers and promise uniformity. As a resultant role, any differences we found between the assorted specimens were attributed to the mechanical properties of the collar and not to the bone model. We besides used a wide osteotomy of the proximal metaphysis like the one used by Hansen et aluminum and Laflamme et alabama, simulating the worst-case scenario of an extra-articular fracture of the proximal tibia in terms of stability, since there is no cortical contact of the fracture fragments, no soft tissue stabilization and the stability of the fracture depends entirely on the plant 12, 16. During tire testing, we loaded the bone models in an axis median to the anatomic bloc of the tibia. This load mood, that was proposed by Gaebler et aluminum and has been implemented in a number of studies, simulates the placement of the expected resultant load during extremum loading 19, 20. During inactive cargo, we used the anatomic axis of the model to apply higher but non-destructive forces. Regarding stiffness, the results were similar in these two testing modes in terms of group : in both tests, group D had the highest severity values, while group E had the lowest ones. however, in the eccentric load, the differences observed between the respective models were more discrete. There are respective studies in the literature which are focused on a proximal tibial fracture and its optimum treatment. In a cadaverous study, Feng et alabama compared a complete with two proximal screws with plat and external fixation systems 24. They found that the collar had adequate mechanical properties in compression but not in bending. The authors concluded that a titanium nail with two screws is not adequately stable and should be assisted with a plate. In our study, we found that titanium nails with more than three screws outperformed titanium nails with merely two or three screws. therefore, more proximal lock options could render the want for adjuvant methods of arrested development unnecessary. Laflamme et aluminum compared a tubular tibial smash to a plate. The authors concluded that in terms of stability, a construct with a nail and four proximal screws was like to a plate osteosynthesis 12. They besides found that the removal of the two external oblique muscle screws, in all testing modes, significantly decreased the inflexibility of the system. Three out of the six nails we tested were tubular, titanium with a stove of three to five screws. We found that group E that had the maximum number of proximal screws in versatile directions was starchy, followed by group A that had three screws, two lateral pass and one anteroposterior, and then by group E that had two external oblique muscle and one dynamic lateral. Our results agree with Laflamme ’ south, in that more screws in more than one management total to the constancy of the breeze through manufacture. In a biomechanical trial, Gollwitzer et alabama, found that two proximal screws were more static than one ; when they used entirely one screw, the construct was stiffer only when they increased the distance of the screws from the stifle joint 25. We did not test any nails with less than two locking options, but we found that the second-best group in terms of stability was with that with the maximal number of screws and the most distal fuck closest to the fault, compared to all early nails. however, the stablest construct had only two devious screws and was relatively close to the stifle joint. This shows that other mechanical factors play a more critical function than the outdistance from the stifle joint. In a biomechanical study, Weninger et aluminum compared solid and cannulate tibial nails for the treatment of precarious distal tibial fractures. The authors concluded that screw failures occurred earlier with cannulated nails than with upstanding ones 26. To the best of our cognition, this is the only study that directly compares these two types of nails and shows that screw numeral and shape are identical important in cannulate nails, since the load shared from the nail to the locking configuration may lead to mechanical failure. In line with the interpretation given by Weninger et aluminum, our data suggest that a solid nail with merely two oblique screws ( group D ) is stiffer than a cannulate one with five screws ( group E ), in both static and dynamic load. There are a few papers in the literature supporting the use of the maximal count of screws for the intramedullary pinpoint of proximal tibial fractures. Hansen proved that three screws provide importantly more stability compared to two. freeman showed that four screws perform better than three, while Kandemir concluded that a nail with four proximal screws provides alike fatigue performance to double locking plates 16, 19, 27. Of the three cannulated nails in our experiment, the stablest of all was the one with five screws ( group F ), while the least stable of all was the nail with three screws, two devious and one lateral ( group E ). Group A that had two lateral pass and one anteroposterior showed better mechanical stability than group E, which we attributed to the locking practice in multiple directions. It has been suggested that controlled micro-motion at a range of 0.2 to 1 millimeter at the fracture site will promote healing 28. however, a arrangement that is besides cadaver or very flexible will lead to delayed union, non-union, and finally implant failure, if left untreated. In our results of static load, we used a cut-off compass point of one millimeter of displacement and compared the forces required to reach that target. We came to the decision that on this mechanical model, a person weighing up to 100 kg can fully weight digest with a nail from group D without creating excessive gesture at the fracture site that is more than one millimeter. On the other hand, nails from group E allow excessive micro-motion, when a person weighs more than 56.1 kilogram when the person amply weight bears. As a resultant role, with regard to postoperative instructions, it is compulsory to take into history the patient ’ randomness weight : Until there are signs of fracture heal, patients are advised to partially weight bear with a load by and large less than 50 kilogram. To the best of our cognition, the present study is the first to compare six different commercially available intramedullary nails for the discussion of mentally ill proximal tibial fractures. Every attempt was made to exclude early mechanical factors and compare only the behavior of the implants in terms of constancy, which is of the extreme importance when it comes to fracture healing. Limitations of our analyze include the relatively small number of specimens and testing in lone two loading modes.

In the past, intramedullary nail down has been considered an insecure method for the discussion of proximal tibial fractures. We believe that with the tractability of proximal screw configuration that recently developed implants offer, intramedullary complete has become a safe and reasonable option for these fractures. The present discipline showed that the solid stainless steel steel pinpoint from Orthofix ( Verona, Italy ) with two oblique proximal screw was better in terms of mechanical constancy, followed by the Expert cannulated titanium pinpoint from Depuy-Synthes ( Oberdorf, Switzerland ) with five proximal screws .

Conflict of interest

The authors declare that there is no conflict of interest and they have no proprietary interests in the materials described in the article .

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