End caps prevent nail migration in elastic stable intramedullary nailing in paediatric femoral fractures: a biomechanical study using synthetic and cadaveric bones

Paediatric femoral shaft fractures: an instructional review for the FRCS examination

This review presents the principal features of paediatric femoral shaft fractures including the contemporary management strategies and relevant supporting evidence. The article is an overview of information relevant to clinical practice, in addition to preparation for the FRCS (Orth) examination.

Mechanical behaviors of titanium, nickel-titanium, and stainless elastic intramedullary nail in fixation of tibial diaphyseal fractures

INTRODUCTION

Elastic nails have been widely used in the diaphyseal fracture fixation of long bones in adolescents. However, high complication rates have been reported in cases involving weights exceeding 55 kg. The existing nails are fabricated with different metals in clinical settings; however, the effect of the materials on the mechanical responses of the fractured bone remains unclear. Hence, the present study is conducted to compare the mechanical responses of typically used metals, namely titanium, stainless, and nickel-titanium, for elastic nails in the fixation of tibial diaphyseal fractures.

MATERIAL AND METHODS

A sawbone tube is used to determine the contact force, which is developed after constraining the nail inside the narrow canal using different nail materials. Furthermore, a finite element (FE) model of the tibial diaphyseal fracture is developed to predict the fracture gap deformation based on different nail materials under axial compression and bending loads. The push-out force in the FE simulation is compared with that of a case without an end cap.

RESULTS

In the sawbone tube, the results indicate that the contact force developed by the titanium nail is significantly higher than those developed by stainless and nickel-titanium nails. The contact forces developed by the titanium, stainless steel, and nickel- titanium nails are 385 (SD 34), 358 (SD 49), and 258 (SD 42) N, respectively. In the FE simulation, the titanium nail yields the highest push-out force when an end cap is not used, and the push-out forces in axial compression are 201, 183, and 87 N in the titanium, stainless, and nickel-titanium nails under axial compression, respectively. By contrast, the stainless nail yields the smallest gap deformation when an end cap is used.

CONCLUSION

Results of the present study show that the end cap is an important factor affecting the mechanical responses of nails fabricated using different materials. Titanium nails are preferred when an end cap is not used, whereas stainless nails are preferred when an end cap is used.

The clinical features, management options and complications of paediatric femoral fractures

This article discusses the incidence, applied anatomy and classification of paediatric femoral fractures based on critical appraisal of the available evidence. The aim is to identify techniques that are relevant to contemporary practice whilst excluding the technical details of individual procedures that are beyond the scope of this review. Injuries of the proximal, diaphyseal and distal segments are considered individually as there are considerations that are specific to each anatomical site. Femoral neck fractures are rare injuries and require prompt anatomical reduction and stable fixation to minimise the potentially devastating consequences of avascular necrosis. Diaphyseal fractures are relatively common, and there is a spectrum of management options that depend on patient age and size. Distal femoral fractures often involve the physis, which contributes up to 70% of femoral length. Growth arrest is common consequence of fractures in this region, resulting in angular and length-related deformity. Long-term surveillance is recommended to identify deformity in evolution and provide an opportunity for early intervention. Deliberate injury should be considered in all fractures, particularly distal femoral physeal injuries and fractures in the non-walking child.

Length unstable femoral fractures: A misnomer?

BACKGROUND

Flexible intramedullary nailing (FIMN) is relatively contraindicated for pediatric length unstable femoral fractures.

AIM

To evaluate FIMN treatment outcomes for pediatric diaphyseal length unstable femoral fractures in patients aged 5 to 13 years.

METHODS

This retrospective study includes pediatric patients (age range 5-13 years) who received operative treatment for a diaphyseal femoral fracture at a single institution between 2013 and 2019. Length unstable femur fractures treated with FIMN were compared to treatment with other fixation methods [locked intramedullary nailing (IMN), submuscular plating (SMP), and external fixation] and to length stable fractures treated with FIMN. Exclusion criteria included patients who had an underlying predisposition for fractures (e.g., pathologic fractures or osteogenesis imperfecta), polytrauma necessitating intensive care unit care and/or extensive management of other injuries, incomplete records, or no follow-up visits. Patients who had a length stable femoral fracture treated with modalities other than FIMN were excluded as well.

RESULTS

Ninety-five fractures from ninety-two patients were included in the study and consists of three groups. These three groups are length unstable fractures treated with FIMN (n = 21), length stable fractures treated with FIMN (n = 45), and length unstable fractures treated with either locked IMN, SMP, or external fixator (n = 29). P values < 0.05 were considered statistically significant. Patient characteristic differences that were statistically significant between the groups, length unstable with FIMN and length unstable with locked IMN, SMP, or external fixator, were average age (7.4 years vs 9.3 years, respectively), estimated blood loss (29.2 mL vs 98 mL, respectively) and body mass (27.8 kg vs 35.1 kg, respectively). All other patient characteristic differences were statistically insignificant. Regarding complications, length unstable with FIMN had 9 total complications while length unstable with locked IMN, SMP, or external fixator had 10. Grouping these complications into minor or major, length unstable with locked IMN, SMP, or external fixator had 6 major complication while length unstable with FIMN had 0 major complications. This difference in major complications was statistically significant. Lastly, when comparing patient characteristics between the groups, length unstable with FIMN and length stable with FIMN, all characteristics were statistically similar except time to weight bearing (39 d vs 29 d respectively). When analyzing complication differences between these two groups (9 total complications, 0 major vs 20 total complications, 4 major), the complication rates were considered statistically similar.

CONCLUSION

FIMN is effective for length unstable fractures, having a low rate of complications. FIMN is a suitable option for length stable and length unstable femur fractures alike.

Advanced interlocking systems to improve heavy-load-bearing characteristics of flexible intramedullary nailing

Flexible intramedullary nailing (FIN) is a minimally invasive and widespread standard method for osteosynthesis of pediatric long bone fractures. In the case of unstable fractures of the lower extremity, interlocking systems need to be used to prevent axial shortening and subsequent perforation of the nail at its insertion site. In the present study, four different screw-fixed interlocking systems for FINs (Hofer TwinPlug with two 3-mm titanium interlocking screws, Hofer FixPlug with 3-mm titanium interlocking screw, Hofer Plug with 3.5-mm titanium interlocking screw, and Hofer Plug with 3-mm titanium interlocking screw) in comparison with the commonly used Ender stainless steel nails (locked with 3.5-mm screw) were experimentally investigated in cadaveric lamb tibiae, regarding their load characteristics and failure modes in the case of heavy loading. The specimens were subjected to sequential axial cyclic loading of 5000cycles with stepwise increase of the load amplitude until failure. Migration of locking screws and internal damage of bone tissue was quantified by micro-computed tomography (CT) imaging. Ender nails failed on average at a peak load of 800 N, TwinPlugs at 1367 N, FixPlugs at 1222 N, Plugs 3.5mm at 1225 N and Plugs 3.0mm at 971 N. TwinPlugs, FixPlugs, and Plugs 3.5mm failed in a slow manner over several hundred loading cycles, whereas Ender nails and Plugs 3.0mm exhibited abrupt failure without any prior indication. Our results confirm that axial stability of FIN can be further improved by screw-fixed plugs by simultaneously avoiding shortcomings of an eye-locked system, which the Ender nails are. Considering biomechanical results, plug interlocking systems with 3.5-mm screws should be favored over conventional Ender nails and plugs with 3-mm screws.

Minimally invasive intramedullary nailing of clavicular fractures by a new titanium elastic nail

Objectives

The aim of this study was to evaluate clinical results of a new design titanium elastic nail (TEN) for displaced midshaft clavicular fractures.

Patients and methods

Between February 2012 and December 2013, a total 36 patients with displaced midshaft clavicular fractures were treated with intramedullary nailing stabilization with our new design TEN. Blood loss, mean times of operation, postoperative complications, hospital stays and time to bone union was recorded. The outcomes were evaluated with radiographic assessment, visual analog scale (VAS) score, the Constant-Murley, and the disabilities of the arm, shoulder, and hand (DASH) scores.

Results

The mean blood loss was 50.278 ± 10.753 ml, while the mean operation, hospital stay and bone union times were 46.417 ± 9.232 min, 10.056 ± 2.672 days and 11.583 ± 2.729 weeks, respectively. After removal of the TENs at a mean of 10.2 months (range, 8-13 months) after surgery, no re-fracture and nonunion was found in any patient. Two cases of shoulder back stabbing pain were spontaneously resolved later. The mean fracture healing time was 12 weeks. The VAS score and motion ranges of shoulder joint were significantly improved postoperatively (P < 0.001). The shoulder function recovery showed the excellent results with the mean Constant-Murley score of 93.389 ± 2.749 and DASH scores of 2.528 ± 1.567.

Conclusion

Our new TEN design used in intramedullary fixation might be a safe and effective technique for treatment of displaced midshaft clavicular fractures.

Level of evidence: Level IV, therapeutic study.

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A new our self designed TEN was used for clavicular fractures.

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The new TENs were individual designed with various types for different patients.

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Satisfactory clinical therapeutic effects and few complications were obtained.