Rotational control of various pediatric femur fractures stabilized with titanium elastic intramedullary nails. J Pediatr Orthop. 2004;24:172-177. [PMID: 15076602 DOI: 10.1097/01241398-200403000-00007]

The use of flexible nails in the treatment of paediatric long bone fractures: Experience at a level one paediatric trauma centre, a cohort study

Introduction

Fractures occur in children at an incidence only surpassed by women >85 years and account for 25 % of paediatric injuries. Over the last three decades, there has been a trend towards operative management of children's fractures including utilisation of flexible nails as popularised by the Nancy group in the 1980s. Between 5 and 11 % of paediatric forearm fractures are now fixed in this manner with complication rates of 12-42 %. This study shares the experience of a paediatric level one major trauma centre using this technique in managing long bone fractures in children.

Methods and materials

This retrospective cohort study comprises a sequential series of 109 cases (71 children) of upper and lower limb fractures in children (aged 16 years and below) who underwent fracture fixation using flexible intramedullary nails between 1st April 2015 and 31st March 2019. Radiological and clinical outcomes and complications were assessed.

Results

Ninety-three cases (10 in the lower limb, 83 in the upper limb) satisfied the inclusion criteria in 57 children with a mean age of 8.6 years. All cases were successfully reduced intra-operatively and 92 (98.9 %) achieved union. Taking into account all complications in the upper and lower limb, the overall complication rate is 30.1 % (28 cases) with the vast majority (13 cases, 46.4 %) occurring in the upper limb due to prominence of metalwork prompting early removal.

Conclusions

This study has shown flexible intramedullary nailing to perform well with good stabilisation of a wide variety of paediatric long bone fractures with restoration of bone alignment, satisfactory outcomes with good union rates and a return to normal function. The technique is also safe and in the upper limb can be performed as day-case surgery by a generalist orthopaedic surgeon. Although the overall complication rate is not insignificant, major complications are rare.

Assessing the risks of children with preoperative comorbidities undergoing comminuted fracture surgery

Introduction

Comminuted fractures are characterized by bones broken in at least two places, destabilizing the bone and requiring surgery. Children whose bones are still developing and maturing tend to have a higher risk of sustaining comminuted fractures as the result of trauma. Trauma is a major cause of death in children and constitutes a major issue in orthopedics because of the unique properties of children's bones compared to adult bones and the associated complications.

Methods

This retrospective, cross-sectional study aimed to refine the association between comorbid disease and comminuted fractures in pediatric subjects using a large, national database. All data were extracted from the National Inpatient Sample (NIS) database from 2005 to 2018. Logistic regression analysis was used to evaluate associations between comorbidities and comminuted fracture surgery and between various comorbidities and LOS or unfavorable discharge.

Results

A total of 2,356,483 patients diagnosed with comminuted fractures were selected initially, of whom 101,032 patients aged younger than 18 years who underwent surgery for comminuted fractures were included. Study results suggest that patients with any comorbidities undergoing orthopedic surgery for comminuted fracture appear to have longer LOS and a higher proportion of discharge to long-term care facilities.

Discussion

Almost all comorbidities were significantly associated with poor in-hospital outcomes and longer LOS. The analysis of comminuted fractures in children may provide useful information to help first responders and medical personnel evaluate and manage comminuted fractures appropriately.

External fixator-augmented flexible intramedullary nailing of an unstable pediatric femoral shaft fracture model: a biomechanical study

The objective of this study was to test the compressive strength and torsional stiffness provided by the addition of a two-pin external fixator to an unstable pediatric femoral shaft fracture model after being instrumented with flexible intramedullary nailing (FIMN), and to compare this to bridge plating and FIMN alone. A length-unstable oblique diaphyseal fracture was created in 15 pediatric sized small femur models. Fracture stabilization was achieved by three constructs: standard retrograde FIMN with two 3.5-mm titanium (Ti) nails (Group 1), FIMN augmented with a two-pin external fixator (Group 2), and a 4.5-mm bridge plate (Group 3). Groups I and II were tested in 10 cycles of axial rotation to 10° in both directions at 0.1 Hz under 36 kg of compression. Torsional stiffness was calculated. Compressive strength was calculated by applying an axial load of 5 mm/min until failure was encountered. Failure was defined as the force required to achieve 10° varus at the fracture site or shortening of 2 cm. Group II demonstrated a greater compressive strength compared to Group I (1067.32 N vs 453.49 N, P < 0.001). No significant difference in torsional stiffness was found between Groups I and II (0.45 vs 0.38 Nm/deg, P = 0.18). Group III showed superior compressive strength and rotational stiffness compared to Groups I and II. In an unstable pediatric femoral shaft fracture model, augmenting FIMN with a two-pin external fixator increased the compressive strength by 147%, but did not increase torsional stiffness. Bridge plating with a 4.5-mm plate provided superior compressive strength and torsional stiffness.

Retrograde Stainless Steel Flexible Nails Have Superior Resistance to Bending in Distal Third Femoral Shaft Fractures

BACKGROUND

It has been shown that retrograde titanium flexible intramedullary nails (Ti FIN) provide superior resistance to bending compared to antegrade Ti FIN in distal femur fractures. The purpose of this study was to compare resistance to torsional and bending forces of stainless steel (SS) FIN, with or without a locking screw, and Ti FIN in distal third femoral shaft fractures. We hypothesize that locked retrograde SS FIN will demonstrate greater resistance to both bending and torsional forces.

METHODS

Thirty adolescent synthetic femur models were used to simulate transverse distal femoral fractures at either 60 mm or 90 mm proximal to the distal femoral physis. The femurs were instrumented with antegrade Ti FIN, antegrade SS FIN, retrograde Ti FIN, retrograde SS FIN, or retrograde locked SS FIN. Three models for each construct at both osteotomy levels were tested. Models were analyzed to determine maximum resistance to bending and torsion.

RESULTS

In fractures 60 mm from the physis, retrograde SS FIN demonstrated statistically superior resistance to bending when compared with both antegrade and retrograde Ti FIN (P=0.001 and 0.008, respectively) and antegrade SS FIN (P=0.0001). Locked SS constructs showed a trend towards greater resistance to bending forces when compared with unlocked constructs (P>0.05). No significant difference was seen in resistance to bending when fractures were 90 mm proximal to the distal femoral physis between the five groups. No significant differences were observed in resistance to torsion in either the proximal or distal fracture models, regardless of construct type.

CONCLUSIONS

Retrograde SS FIN confer significantly greater resistance to bending forces for fractures 60 mm proximal to the distal femoral physis compared with Ti FIN or antegrade entry SS FIN. In fractures 90 mm from the physis, no differences were noted in our model. Our results support the use of retrograde SS nails in the pediatric patient with distal femoral shaft fractures.

LEVEL OF EVIDENCE

Level II-comparative biomechanical study.

Elastic stabile intramedullary nailing (ESIN) of diaphyseal femur fractures in children and adolescents: A strobe-compliant study

Elastic stabile intramedullary nailing (ESIN) is a well-established method to stabilize diaphyseal fracture of the femur (DFF) in children. We aimed to evaluate the minimal medullary canal diameter (MMCD) of the fractured femur relative to the diameter of the nails. We also analyzed the real anteversion angle (AVA) of the affected femur in comparison to the healthy femur.We retrospectively reviewed the medical records and plain X-ray images of children aged 2-15 years treated with ESIN for unstable femoral shaft fractures between 2004 and 2012. We measured MMCD on preoperative plain X-ray images. Nail diameter (ND) and any postoperative complications were extracted from the medical records. At follow-up conducted at a median of 40 months (range: 4-103 months) after the operation, we obtained Dunn X-ray images of both hips. Particular emphasis was placed on postoperative torsional differences in relation to age, weight, and maturity of the growth plate.We analyzed the relationship between postoperative rotational malalignment and the ratio of ND to MMCD.Median age of the 22 children at the time of injury was 7.5 years (range: 2-15 years). Median body weight was 25 kg (range: 13-57 kg). Median MMCD amounted to 8.6 mm (range: 5.5-11.0 mm). Median ND/MMCD was 36.9% (range: 27.3%-47.4%). Radiological analyses revealed a median of 27.0° (range: -22.0° to +49.0°) of real AVA in the affected leg and 32.5° (range: 18.0°-48.0°) in the healthy leg.Three children (13.6%) experienced a grade III complication (Clavien-Dindo classification of surgical complications; CDCSC). Two of these children suffered retrotorsion of the femoral neck, while the third child experienced diminished anteversion.Overall, 3 of 22 children (13.6%) suffered a CDCSC-grade III complication (i.e., retrotorsion of the femoral neck in two children and diminished anteversion of the femoral neck in one child). We recommend obtaining Dunn images at the end of the operation to confirm correct rotational alignment after stabilization with ESIN. Further prospective studies are required to confirm our findings.

Outcome of antegrade intramedullary fixation for juvenile fifth metacarpal neck fracture with titanium elastic nail

The purpose of the current study was to assess the outcome of antegrade intramedullary fixation with titanium elastic nail (TEN) in displaced fifth metacarpal neck fractures. The present study included 69 consecutive juvenile patients with displaced fifth metacarpal fractures. The head-shaft angle of the fifth metacarpal and range of motion (ROM) of the metacarpophalangeal (MCP) joint were evaluated. A disabilities of the arm, shoulder and hand (DASH) questionnaire was used to assess upper arm function. The head-shaft angle of the affected side was significantly improved postoperatively (P<0.05). No marked difference was observed between the affected and unaffected side in head-shaft angle and ROM. The average DASH score was 1.7 (range, 0-6.0). All patients obtained anatomical reduction postoperatively and the average healing time was 5.7±1.09 weeks (range, 5-10 weeks) with no non-union cases. Therefore antegrade intramedullary fixation with TEN is recommended as an easy, reliable and minimally invasive surgical technique for treating displaced fifth metacarpal neck fractures.

Titanium elastic nailing in diaphyseal femoral fractures of children below six years of age

AIM

To report the clinical and radiographic results of titanium elastic nail (TEN) in diaphyseal femoral fractures of children below age of six years.

METHODS

A retrospective analysis of 27 diaphyseal femoral fractures in children younger than six years treated with TEN between 2005 and 2015 was conducted. Patients were immobilized in a cast for 5 wk and the nails were removed from 6 to 12 wk after surgery. Twenty-four cases were clinically and radiographically re-evaluated using the Flynn’s scoring criteria, focusing on: Limb length discrepancy, rotational deformity, angulation, hip and knee range of motion (ROM), functional status, complications, and parent’s satisfaction.

RESULTS

Sixteen males and eight females with a mean age of 3.2 years at the time of treatment were re-evaluated at an average follow-up of 58.9 mo. No cases of delayed union were observed. The mean limb lengthening was 0.3 cm. Four cases experienced limb lengthening greater than 1 cm and always minor than 2 cm. Twelve point five percent of the cases showed an angulation < 10°. Complete functional recovery (hip and knee ROM, ability to run and jump on the operated limb) occurred in 95.7% of cases. Complications included two cases of superficial infection of the TEN entry point, one case of refracture following a new trauma, and one TEN mobilization. According to the Flynn’s scoring criteria, excellent results were obtained in 79.2% of patients and satisfactory results in the remaining 20.8%, with an average parent’s satisfaction level of 9.1/10.

CONCLUSION

TEN is as a safe, mini-invasive and surgeon-friendly technique and, considering specific inclusion criteria, it represents a useful and efficacy option for the treatment of diaphyseal femoral fractures even in patients younger than six years of age.

Biomechanical investigation of titanium elastic nail prebending for treating diaphyseal long bone fractures

This study numerically investigated the deformation of titanium elastic nails prebent at various degrees during implantation into the intramedullary canal of fractured bones and the mechanism by which this prebending influenced the stability of the fractured bone. Three degrees of prebending the implanted portions of the nails were used: equal to, two times, and three times the diameter of the intramedullary canal. Furthermore, a simulated diaphyseal fracture with a 5-mm gap was created in the middle shaft portion of the bone fixed with two elastic nails in a double C-type configuration. End caps were simulated using a constraint equation. To confirm that the simulation process is able to present the mechanical response of the nail inside the intramedullary, an experiment was conducted by using sawbone for validation. The results indicated that increasing the degrees of nail prebending facilitated straightening the nails against the inner aspect of canal after implantation, with increase in stability under torsion. Furthermore, reducing nail prebending caused a larger portion of the nails to move closer to the loading site and center of bone after implantation; the use of end caps prevented the nail tips from collapsing and increased axial stability. End cap use was critical for preventing the nail tips from collapsing and for increasing the stability of the nails prebent at a degree equal to the diameter of the canal with insufficient frictional force between the nail and canal. Therefore, titanium elastic nail prebending in a double C-type configuration with a degree three times the diameter of the canal represents a superior solution for treating transverse fractures without a gap, whereas that with a degree equal to the diameter of the intramedullary canal and combined with end cap use represents an advanced solution for treating comminuted fractures in a diaphyseal long bone fracture.

Computational comparison of tibial diaphyseal fractures fixed with various degrees of prebending of titanium elastic nails and with and without end caps

INTRODUCTION

Elastic stable intramedullary nailing (ESIN) is a treatment strategy for the management of diaphyseal long-bone fractures in adolescents and children, but few studies have investigated the mechanical stability of tibial diaphyseal fractures treated with various degrees of prebending of the elastic nails. Therefore, the aim of this study was to compare the mechanical stability, including the gap deformation and nail dropping, of a tibia fracture with various fracture sites and fixed with various degrees of prebending of the elastic nails by the finite element method. Furthermore, the contribution of end caps to stability was taken into consideration in the simulation.

METHODS

A tibia model was developed with a transverse fracture at the proximal, middle and distal parts of the diaphysis, and fixed with three degrees of prebending of elastic nails, including those equal to, two times and three times the diameter of the intramedullary canal. The outer diameter of the nail used in the computation was 3.5mm, and the fractured tibia was fixed with two elastic double C-type nails. Furthermore, the proximal end of each nail was set to free or being tied to the surrounding bone by a constraint equation to simulate with or without using end caps.

RESULTS

The results indicated that using end caps can prevent the fracture gap from collapsing by stopping the ends of the nails from dropping back in all prebending conditions and fracture patterns, and increasing the prebending of the nails to a degree three times the diameter of the canal reduced the gap shortening and the dropping distance of the nail end in those without using end caps under axial compression and bending. Insufficient prebending of the nails and not using end caps caused the gap to collapse and the nail to drop back at the entry point under loading.

CONCLUSIONS

Using end caps or increasing the prebending of the nails to three times the diameter of the canal is suggested to stop the nail from dropping back and thus produce a more stable structure, with less gap deformation, in the management of a simulated tibial diapyhseal fracture by using titanium elastic nails with a double C-shape.

Comminuted long bone fractures in children. Could combined fixation improve the results?

Comminuted diaphyseal fractures in the pediatric age group represent a major orthopedic problem. It is associated with a high incidence of complications and poor outcomes because of the instability and difficulty in treatment. The aim of this study was to evaluate the efficacy of combined external skeletal fixation and flexible intramedullary nails in reconstruction of comminuted diaphyseal fracture in skeletally immature patients. Combined external fixator and elastic stable intramedullary nails were used in the management of 27 pediatric patients (15 males and 12 females) with unstable comminuted diaphyseal fractures of the tibia and femur. There were 19 fractures of the femur and eight fractures of the tibia. The average age of the patients was 8.7 years (range 7-14 years) for the femur and 10.8 years (range 6-15 years) for the tibia. Fractures were classified according to the system of Winquist and Hansen as grade II (five cases), grade III (nine cases), and grade IV (13 cases). All cases were operated within 6 days (range 0-6 days) after injury. The mean follow-up period was 2.8 years (range 2-3.5 years). The average duration of the external fixation was 1.6 months for fractures of the tibia, whereas it was 1.4 months for fractures of the femur. The average time for tibia fracture union was 2.8 months for fractures of the tibia, whereas it was 1.9 months for fractures of the femur. Malalignment in varus less than 5° was noted in one patient. One patient had a limb-length discrepancy of 1.5 cms. There were five cases (18.5%) with pin-tract infection. According to the Association for the Study and Application of the Methods of Ilizarov evaluation system, bone results were excellent in 23 cases (85.2%), good in three cases (11.1%), and poor in one case (3.7%). Functional results were excellent in 22 (81.5%) cases and good in five (18.5%) cases. Combined use of external fixators and elastic intramedullary nails is a good method for the treatment of comminuted long bone fractures in children.

Improving stability of elastic stable intramedullary nailing in a transverse midshaft femur fracture model: biomechanical analysis of using end caps or a third nail

BACKGROUND

Elastic stable intramedullary nailing (ESIN) is accepted widely for treatment of diaphyseal femur fractures in children. However, complication rates of 10 to 50 % are described due to shortening or axial deviation, especially in older or heavier children. Biomechanical in vitro testing was performed to determine whether two modified osteosyntheses with end caps or a third nail could significantly improve the stability in comparison to classical elastic stable intramedullary nailing in a transverse femur fracture model.

METHODS

We performed biomechanical testing in 24 synthetic adolescent femoral bone models (Sawbones®) with a transverse midshaft (diaphyseal) fracture. First, in all models, two nails were inserted in a C-shaped manner (2 × 3.5 mm steel nails, prebent), then eight osteosyntheses were modified by using end caps and another eight by adding a third nail from the antero-lateral (2.5-mm steel, not prebent). Testing was performed in four-point bending, torsion, and shifting under physiological 9° compression.

RESULTS

The third nail from the lateral showed a significant positive influence on the stiffness in all four-point bendings as well as in internal rotation comparing to the classical 2C configuration: mean values were significantly higher anterior-posterior (1.04 vs. 0.52 Nm/mm, p < 0.001), posterior-anterior (0.85 vs. 0.43 Nm/mm, p < 0.001), lateral-medial (1.26 vs. 0.70 Nm/mm, p < 0.001), and medial-lateral (1.16 vs. 0.76 Nm/mm, p < 0.001) and during internal rotation (0.16 vs. 0.11 Nm/°, p < 0.001). The modification with end caps did not improve the stiffness in any direction.

CONCLUSIONS

The configuration with a third nail provided a significantly higher stiffness than the classical 2C configuration as well as the modification with end caps in this biomechanical model. This supports the ongoing transfer of the additional third nail into clinical practice to reduce the axial deviation occurring in clinical practice.

Biomechanical comparison of semi-rigid pediatric locking nail versus titanium elastic nails in a femur fracture model

BACKGROUND

The treatment for length-unstable diaphyseal femur fractures among school-age children is commonly intramedullary elastic nails, with or without end caps. Another possible treatment is the semi-rigid pediatric locking nail (PLN). The purpose of this biomechanical study was to assess the stability of a length-unstable oblique midshaft fracture in a synthetic femur model stabilized with different combinations of intramedullary elastic nails and with a PLN.

METHODS

Twenty-four femur models with an intramedullary canal diameter of 10.0 mm were used. Three groups with various combinations of titanium elastic nails (TEN) with end caps and one group with a PLN were tested. An oblique midshaft fracture was created, and the models underwent compression, rotation, flexion/extension, and a varus/valgus test, with 50 and 100 % of the forces generated during walking in corresponding planes.

RESULTS

We present the results [median (range)] from 100 % loading during walking. In axial compression, the PLN was less shortened than the combination with two 4.0-mm TEN [by 4.4 (3.4-5.4) mm vs. 5.2 (4.8-6.6) mm, respectively; p = 0.030]. No difference was found in shortening between the PLN and the four 3.0-mm TEN [by 7.0 (3.3-8.4) mm; p = 0.065]. The two 3.0-mm TEN did not withstand the maximum shortening of 10.0 mm. In external rotation, the PLN rotated 12.0° (7.0-16.4°) while the TEN models displaced more than the maximum of 20.0°. No model withstood a maximal rotation of 20.0° internal rotation. In the four-point bending test, in the coronal and the sagittal plane, all combinations except the two 3.0-mm TEN in extension withstood the maximum angulation of 20.0°.

CONCLUSIONS

PLN provides the greatest stability in all planes compared to TEN models with end caps, even though the difference from the two 4.0-mm or four 3.0-mm TEN models was small.

Modification of elastic stable intramedullary nailing with a 3rd nail in a femoral spiral fracture model - results of biomechanical testing and a prospective clinical study

Background

Elastic stable intramedullary nailing (ESIN) is the standard treatment for displaced diaphyseal femoral fractures in children. However, high complication rates (10-50%) are reported in complex fractures. This biomechanical study compares the stiffness with a 3rd nail implanted to that in the classical 2C-shaped configuration and presents the application into clinical practice.

Methods

For each of the 3 configurations of ESIN-osteosynthesis with titanium nails eight composite femoral grafts (Sawbones®) with an identical spiral fracture were used: 2C configuration (2C-shaped nails, 2 × 3.5 mm), 3CM configuration (3rd nail from medial) and 3CL configuration (3rd nail from lateral). Each group underwent biomechanical testing in 4-point bending, internal/external rotation and axial compression.

Results

2C and 3CM configurations showed no significant differences in this spiroid type fracture model. 3CL had a significantly higher stiffness during anterior-posterior bending, internal rotation and 9° compression than 2C, and was stiffer in the lateral-medial direction than 3CM. The 3CL was less stable during p-a bending and external rotation than both the others. As biomechanical testing showed a higher stability for the 3CL configuration in two (a-p corresponding to recurvation and 9° compression to shortening) of three directions associated with the most important clinical problems, we added a 3rd nail in ESIN-osteosynthesis for femoral fractures. 11 boys and 6 girls (2.5-15 years) were treated with modified ESIN of whom 12 were ‘3CL’; due to the individual character of the fractures 4 patients were treated with ‘3CM’ (third nail from medial) and as an exception 1 adolescent with 4 nails and one boy with plate osteosynthesis. No additional stabilizations or re-operations were necessary. All patients achieved full points in the Harris-Score at follow-up; no limb length discrepancy occurred.

Conclusion

The 3CL configuration provided a significantly higher stiffness than 2C and 3CM configurations in this biomechanical model. These results were successfully transmitted into clinical practice. All children, treated by 3CL or 3CM according to the individual character of each fracture, needed no additional stabilization and had no Re-Do operations. As a consequence, at our hospital all children with femoral diaphyseal fractures with open physis are treated with this modified ESIN-technique.

Biomechanical performance of flexible intramedullary nails with end caps tested in distal segmental defects of pediatric femur models

BACKGROUND

Unstable distal femoral fractures in children are challenging lesions with restricted surgical options for adequate stabilization. Elastic nails have become popular for treating femoral shaft fractures, yet they are still challenging for using in distal fractures. The aim of this study was to test whether end caps (CAP) inserted into the nail extremity improved the mechanical stabilization of a segmental defect at the distal femoral metaphyseal-diaphyseal junction created in an artificial pediatric bone model.

METHODS

Two 3.5-mm titanium elastic nails (TEN) were introduced intramedullary into pediatric femur models, and a 7.0-mm-thick segmental defect was created at the distal diaphyseal-metaphyseal junction. Nondestructive 4-point bending, axial-bending, and torsion tests were conducted. After this, the end caps were inserted into the external tips of the nails and then screwed into the bone cortex. The mechanical tests were repeated. Stiffness, displacement, and torque were analyzed using the Wilcoxon nonparametric test for paired samples.

RESULTS

In the combined axial-bending tests, the TEN+CAP combination was 8.75% stiffer than nails alone (P<0.01); in torsion tests, the TEN+CAP was 14% stiffer than nails alone (P<0.01). In contrast, the 4-point bending test did not show differences between the methods (P=0.91, stiffness; P=0.51, displacement). Thus, the end caps contributed to an increase in the construct stability for torsion and axial-bending forces but not for 4-point bending forces.

CONCLUSIONS

These findings indicate that end caps fitted to elastic nails may contribute to the stabilization of fractures that our model mimics (small distal fragment, bone comminution, and distal bone fragment loss).

CLINICAL RELEVANCE

Type II [therapeutic study: lesser-quality randomized controlled trial (eg, <80% follow-up, no blinding, or improper randomization)].

Increasing stability by pre-bending the nails in elastic stable intramedullary nailing: a biomechanical analysis of a synthetic femoral spiral fracture model

Elastic stable intramedullary nailing (ESIN) is generally acknowledged to be the treatment of choice for displaced diaphyseal femoral fractures in children over the age of three years, although complication rates of up to 50% are described. Pre-bending the nails is recommended, but there are no published data to support this. Using synthetic bones and a standardised simulated fracture, we performed biomechanical testing to determine the influence on the stability of the fracture of pre-bending the nails before implantation. Standard ESIN was performed on 24 synthetic femoral models with a spiral fracture. In eight cases the nails were inserted without any pre-bending, in a further eight cases they were pre-bent to 30° and in the last group of eight cases they were pre-bent to 60°. Mechanical testing revealed that pre-bending to 60° produced a significant increase in the stiffness or stability of the fracture. Pre-bending to 60° showed a significant positive influence on the stiffness compared with unbent nails. Pre-bending to 30° improved stiffness only slightly. These findings validate the recommendations for pre-bending, but the degree of pre-bend should exceed 30°. Adopting higher degrees of pre-bending should improve stability in spiral fractures and reduce the complications of varus deformity and shortening.

Does the extent of prebending affect the stability of femoral shaft fractures stabilized by titanium elastic nails? A biomechanical investigation on an adolescent femur model

BACKGROUND

Elastic stable intramedullary nailing (ESIN) is a common procedure for stabilization of femoral shaft fractures in childhood. Prebending of the nail is generally recommended to achieve optimal nail tension at the fracture site. To our knowledge there are no published data on the effects of prebending on stability. The purpose of this biomechanical study was to compare the effects of different degrees of prebending on the stability of transverse femoral fractures after ESIN using a bone model.

METHODS

Standardized transverse midshaft fractures were created in 20 synthetic, biomechanically validated adolescent bones (4th Generation Composite Femur--Sawbones Europe AB, Sweden) that were stabilized with 2 titanium nails (TEN) each (4 mm diameter, Synthes) and inserted in standardized retrograde technique. The 4 test series addressed nail prebending at 0 degree, 30 degrees, 45 degrees, and 60 degrees. The models were tested biomechanically in 4-point bending in the coronal and sagittal planes, relative stiffness was determined and analyzed statistically. The level of significance was set at P < 0.05.

RESULTS

Comparison of the individual groups showed no significant differences in stiffness for different degrees of prebending in the coronal plane. Significantly reduced stiffness was found in the sagittal plane for the group with 60-degree prebending compared with the 0-degree, 30-degree, and 45-degree prebending groups. Intragroup comparison in the coronal and sagittal planes yielded a significantly reduced stiffness in the sagittal plane compared with the coronal plane in the group with 60-degree prebending. The 45-degree prebending group showed a similar tendency and in the 0-degree and 30-degree prebending groups there were no significant differences.

CONCLUSIONS

On a synthetic bone model, prebending of TEN was found to affect the stability of transverse fractures of the femoral shaft, whereby indiscriminate prebending will reduce stability in the sagittal plane.Despite limited extrapolation of the findings to the in vivo situation, it can be stated that prebending of TEN by 0 to 30 degrees offers the greatest stability in the coronal and sagittal planes for transverse fractures of the femoral shaft.

Biomechanical analysis of a synthetic femoral spiral fracture model: Do end caps improve retrograde flexible intramedullary nail fixation?

Background

Elastic Stable intramedullary Nailing (ESIN) of dislocated diaphyseal femur fractures has become an accepted method for the treatment in children and adolescents with open physis. Studies focused on complications of this technique showed problems regarding stability, usually in complex fracture types such as spiral fractures and in older children weighing > 40 kg. Biomechanical in vitro testing was performed to evaluate the stability of simulated spiral femoral fractures after retrograde flexible titanium intramedullary nail fixation with and without End caps.

Methods

Eight synthetic adolescent-size femoral bone models (Sawbones^® with a medullar canal of 10 mm and a spiral fracture of 100 mm length identically sawn by the manufacturer) were used for each group. Both groups underwent retrograde fixation with two 3.5 mm Titanium C-shaped nails inserted from medial and lateral entry portals. In the End Cap group the ends of the nails of the eight specimens were covered with End Caps (Synthes Company, Oberdorf, Switzerland) at the distal entry.

Results

Beside posterior-anterior stress (4.11 Nm/mm vs. 1.78 Nm/mm, p < 0.001), the use of End Caps demonstrated no higher stability in 4-point bending compared to the group without End Caps (anterior-posterior bending 0.27 Nm/mm vs. 0.77 Nm/mm, p < 0.001; medial-lateral bending 0.8 Nm/mm vs. 1.10 Nm/mm, p < 0.01; lateral-medial bending 0.53 Nm/mm vs. 0.86 Nm/mm, p < 0.001) as well as during internal rotation (0.11 Nm/° vs. 0.14 Nm/°, p < 0.05). During compression in 9°- position and external rotation there was no statistical significant difference (0.37 Nm/° vs. 0.32 Nm/°, p = 0.13 and 1.29 mm vs. 2.18 mm, p = 0.20, respectively) compared to the "classic" 2-C-shaped osteosynthesis without End Caps.

Conclusion

In this biomechanical study the use of End Caps did not improve the stability of the intramedullary flexible nail osteosynthesis.

Biomechanical analysis of a synthetic femur spiral fracture model: Influence of different materials on the stiffness in flexible intramedullary nailing

BACKGROUND

Flexible intramedullary nail fixation of dislocated diaphyseal femur fractures has gained wide acceptance for children and adolescents with open physes. Studies with a special emphasis on complications reveal frequent problems regarding stability, usually in complex fracture types such as spiral fractures and in older children weighing >40kg. This biomechanical study analyses how much the material of the nails influences the stiffness in a synthetic bone model.

METHODS

Twenty-four composite grafts (Sawbones®, 4th generation, medullar canal of 10mm) with an identical spiral fracture were used in three configurations of eight grafts. Elastic stable intramedullary nailing was performed in a retrograde C-shaped manner with two nails of equal size (2×3.5mm). Close contact of the fragments could be achieved. We compared Group A (steel nails) with Group B and C (two types of titanium nails). All specimens underwent 4-point bending, torsion and axial compression in the 0° and 9° positions, and the results were analysed.

FINDINGS

Group A (steel nails) revealed a significantly higher stiffness in all directions than Group B. Apart from compression in the 9° position this steel nail fixation showed significant higher stiffness than titanium nails of Group C. Comparing Group B and C did not show an systematic difference.

INTERPRETATION

In this biomechanical study with composite artificial bones the use of steel Nails demonstrated the highest stiffness in our model when compared to two different titanium nail configurations. Apart from in cases of known allergy or planned MRI-examinations our results and data from the literature question the use of titanium nails.

Residual deformity after treatment of pediatric femur fractures with flexible titanium nails

INTRODUCTION

Procurvatum or anterior bow deformity is a potential complication after treatment of femur fractures with flexible titanium nails (FTNs). This article reports on a clinical evaluation of angulation after treating pediatric femur fractures with FTNs. The article also reports on a complementary investigation of potential causes of these deformities using a biomechanical model.

METHODS

All pediatric femoral shaft fractures treated with FTNs over a 4-year period were reviewed. Fracture location, pattern, angulation, and nail shoe tip orientation were recorded from postoperative radiographs. Malunion was defined as greater than 10 degrees of angulation on the AP radiograph or greater than 15 degrees on the lateral view. As an adjunct to the clinical study, a synthetic femur model was created using midtransverse fractures. These femurs were nailed using 2 FTNs inserted so as to create constructs having the following combinations of nail shoe tip orientation: both anterior (AA), both posterior (PP), both neutral (NN), or 1 anterior and 1 posterior(AP). The resulting angular deformities noticeable upon gross inspection were then measured.

RESULTS

Of the 70 fractures reviewed, malunion occurred in 16 fractures, of which 11 had increased anterior bow. A majority of malunions was observed in older children with middle third of the femur fractures. They were significantly more prevalent in transverse fractures compared with all other fracture patterns. Clinically, increased anterior bowing did not occur if 1 of the nails was positioned to resist procurvatum, as seen in the lateral radiograph. Depending on nail tip orientation, the biomechanical femur fracture model showed significant differences in mean deformations after nail placement: AA had 12.6 degrees of posterior bow compared with 14.8, 3.7, and 0.3 degrees of anterior bow for PP, NN, and AP, respectively.

CONCLUSION

Anterior bowing greater than 15 degrees is the most common malunion noted in this series of femur fractures that were nailed using FTN's. We conclude that final nail shoe tip orientation influences the likelihood of anterior bow deformity. The likelihood of large anterior bowing may be reduced if at least 1 of the nails is inserted with the tip pointing in an anterior direction. LEVEL OF EVIDENCE/CLINICAL RELEVANCE: Level III.

Flexible interlocked nailing of pediatric femoral fractures: experience with a new flexible interlocking intramedullary nail compared with other fixation procedures

BACKGROUND

The optimal treatment of femoral shaft fractures in older children and adolescents remains controversial. We hypothesized that fixation with a flexible interlocking intramedullary nail (FIIN) reduces perioperative complications and improves outcomes, including leg-length discrepancy, time to healing, and time to weight bearing compared with other fixation procedures (OFPs) including standard elastic nail implants.

METHODS

Using a retrospective cohort study design, we reviewed medical records and radiographs of children, 7 to 18 years of age, with femoral shaft fractures requiring open treatment between July 1, 1998, and June 30, 2003. Patients selected for the study had unilateral fracture sites proximal to the supracondylar region and distal to the lesser trochanter, presence of open femoral growth plates, and open surgical treatment. Analyses compared inpatient measures and patient outcomes between FIIN and OFP groups.

RESULTS

Of the 160 patients eligible for inclusion, 23 were lost to follow-up. The remaining 137 patients had a mean follow-up of 396.3 days (SD, 320.4 days), with 58 receiving FIIN fixation and 79 OFP. Although the difference was not statistically significant, complications occurred in 19.0% of patients in the FIIN group and 30.4% in the OFP group. Trochanteric heterotopic ossification was the most common complication (13.8%) noted in the FIIN group and superficial infection (12.8%) in the OFP group. The FIIN group experienced less blood loss (P = 0.042) and shorter time to weight bearing (P = 0.001) without disturbance of proximal femoral geometry or avascular necrosis of the femoral head. In children weighing less than 45.5 kg (100 lb), complications were less common with FIIN (3.6%) compared with OFP (24.4%). A subgroup of patients less than 45.5 kg (100 lb) with standard elastic nail implants (n = 24) had 8.1 times the complications of patients with FIIN.

CONCLUSIONS

Older children and adolescents with femoral shaft fractures treated with a FIIN showed improved outcomes compared with patients treated with OFP.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Fatigue performance of composite analogue femur constructs under high activity loading

Synthetic mechanical analogue bone models are valuable tools for consistent analysis of implant performance in both equilibrium and fatigue biomechanical testing. Use of these models has previously been limited by the poor fatigue performance when tested under realistic service loads. An objective was to determine whether a new analogue bone model (Fourth-Generation) using enhanced analogue cortical bone provides significantly improved resistance to high load fracture and fatigue as compared to the current (Third-Generation) bone models in clinically relevant in situ type testing of total hip implants. Six Third-Generation and six Fourth-Generation mechanical analogue proximal femur models were implanted with a cemented mock hip arthroplasty. Each specimen was loaded at 5 Hz in simulated one-legged stance under load control with a maximum compressive load of 2670 N and load ratio of 0.1. Average complete structural failure in Third-Generation femurs occurred at 3.16 million cycles; all specimens exhibited substantial displacement and crazing at well below 3 million cycles. In contrast, all Fourth-Generation femurs sustained 10 million cycles without complete structural failure and showed little change in actuator deflection. The Fourth-Generation femur model performance was sufficient to allow the model to be used in biomechanically relevant load bearing levels with an intramedullary device without model compromise that would affect test results.

Antegrade versus retrograde titanium elastic nail fixation of pediatric distal-third femoral-shaft fractures: a mechanical study

OBJECTIVES

To determine whether the stability of elastic stable intramedullary nail (ESIN) constructs differ in terms of antegrade versus retrograde insertion for the fixation of pediatric distal-third transverse femoral-shaft fractures.

METHODS

Ten synthetic composite adolescent-sized femur models and 20 flexible titanium (Ti) intramedullary (IM) nails were divided into antegrade and retrograde groups. A simulated transverse fracture was created in each of 10 models in the distal-third region of the shaft (more precisely near the distal fifth). The fractures were then stabilized with ESIN. The specimens were subjected to four-point bending and then axial torsion. Flexural forces were applied to the medial aspect of the model across the fracture site at a rate of 0.05 mm/s to a maximum displacement of 3.7 mm (7 degrees). Torsional moments were applied to the distal aspect of the model in internal and external rotation at a rate of 0.75 degrees/s to a maximum of 10 degrees. Loads and stiffnesses were determined between consistent displacement limits; differences were compared using t tests (alpha = 0.05, two tailed).

RESULTS

Flexural stiffness was significantly greater in the retrograde group (350 +/- 72 N/mm) compared with antegrade (195 +/- 95 N/mm; P = 0.02). A 66-kg load placed across the fracture displaced the site 3.7 mm for the antegrade group, whereas the retrograde group required a load 89% greater (125 kg). Although torsional stiffness tended to be greater in the antegrade group, the differences were not statistically significant (P = 0.2).

CONCLUSIONS

Although the recommendation for distal-third femur fractures is antegrade nail insertion, this study demonstrates that given satisfactory cortical starting points in the distal fragment, retrograde insertion provides greater stability. These mechanical testing data are the first to address this specific fracture scenario and may aid surgical decision making.

Treatment options in pediatric femoral shaft fractures

Fracture of the femur in a pediatric patient presents special problems, and a variety of treatment options. Child abuse and neglect should be considered and evaluated. Fractures in infants (0-18 months) may be treated successfully in a Pavlik Harness. Spica casting is safe and effective in children up to about 6 years or 100 pounds, although complications can occur and careful attention to technique is important. Surgical treatment is superior in most older or larger children or adolescents, and in cases of multiple trauma, soft tissue injury, obesity or head injury. External fixation is minimally invasive, but carries a risk of malunion and refracture. Rigid antegrade intramedully nailing is possible in adolescents of acceptable size, but has a risk of avascular necrosis. Flexible nailing is minimally invasive and well suited to fractures of the central 2/3 of the diaphysis. In comminuted fractures, it may require supplemental external support. Plate fixation is stable and addresses the entire length of the femur. Soft tissue concerns due to surgical exposure can be minimized by the use of submuscular placement technique.

A biomechanical study on flexible intramedullary nails used to treat pediatric femoral fractures

Flexible intramedullary nails have been indicated to treat femoral fractures in pediatric patients. The purpose of this study was to examine the stability of simulated transverse fractures after retrograde intramedullary flexible nail fixation. Various nail diameter combinations were tested using composite femurs in bending, torsion, and a combined axial/bending test where a vertical compressive force was applied to the femoral head. The cross-sectional percent area fill of the nails within the femurs was also determined. In 4 point bending, the greatest repair stiffness was 12% of the intact stiffness. In torsion, the greatest stiffness was 1% of the intact stiffness for either internal or external rotation. The greatest repair stiffness was 80% of the intact stiffness for a compressive load applied to the femoral head. Nail combinations with single nail diameters greater than 40% of the mid-shaft canal width, as measured from an AP radiograph, prevented the fracture from being reduced and left a posterior gap. Flexible intramedullary nails may be of value in the treatment of pediatric femoral fractures, but care must be taken to insert nails that are correctly sized for the canal and to protect the healing fracture from high torsional and bending loads.