Overview
A flexible nail is an elastic intramedullary implant used to stabilize selected long bone fractures, most often in children and adolescents with open growth plates. Rather than fixing the bone externally with a plate, the surgeon inserts one or more flexible rods into the medullary canal so the implant helps support alignment from inside the bone. In pediatric fracture care, flexible nailing is mainly discussed for length-stable shaft fractures of the femur and forearm. Its role, however, depends on the bone involved, fracture pattern, patient size, soft-tissue condition, and local surgical practice. Professional references from AAOS, POSNA, AO educational materials, and peer-reviewed pediatric orthopedic literature consistently describe flexible intramedullary nailing as a useful, but not universal, fixation method. (orthoinfo.aaos.org)
For readers comparing implant approaches, flexible nails should be viewed as one option within the wider field of fracture fixation. Their main advantage is that they can provide internal support through smaller incisions while respecting the growth plate when properly planned. Their main limitation is mechanical: they are less suitable for highly unstable, severely comminuted, very proximal, very distal, or heavier-adolescent fracture situations where another construct may control length, rotation, or alignment more reliably.
How flexible nail fixation works
Flexible nailing is often called elastic stable intramedullary nailing, or ESIN. The basic principle is controlled elasticity. The nail is not intended to act like a large rigid adult femoral nail. Instead, flexible nails are commonly pre-bent and inserted so they press against the inner cortex at several points. When two nails are used from opposite sides, their balanced elastic forces can help resist angulation and maintain the reduced fracture position while callus forms.
In practice, the construct works best when the fracture already has enough inherent stability for the nails to share load rather than completely replace the bone’s stability. This is why transverse and short oblique shaft fractures are often more favorable than long oblique, segmental, or highly comminuted patterns. Flexible nails can assist alignment, but they are not designed to lock every fragment in the same way as a plate with multiple screws or a rigid locked intramedullary nail.
Growth plate protection is one reason flexible nails have an important place in pediatric orthopedics. Standard adult-style intramedullary nailing can be problematic in skeletally immature patients if it risks crossing or damaging a physis. AAOS patient education materials note that intramedullary nailing in children and adolescents requires care around growth plates, and pediatric-focused flexible nail techniques are planned with that concern in mind. (orthoinfo.org)
Where flexible nails are commonly considered
Femoral shaft fractures in children
The pediatric femoral shaft is the classic setting where flexible nail fixation is discussed. AAOS OrthoInfo notes that flexible intramedullary nails are often used to stabilize femur fractures in children ages 6 to 10. POSNA study materials describe flexible nailing as a treatment option particularly for length-stable fractures in children roughly 5 to 11 years old and below about 49 kg. Orthopedic teaching references describe similar selection boundaries, while still emphasizing that the final decision depends on the surgeon’s assessment. (orthoinfo.aaos.org)
This age and weight framing is not a strict rule. A smaller older child may still be considered for flexible nailing, while a younger but heavier child, or a child with an unstable fracture pattern, may need another approach. The key point is predictability: femoral flexible nailing is most reliable when the fracture is length-stable, the child has substantial growth remaining, and the implant can control alignment without excessive risk of shortening or rotation.
Forearm shaft fractures
Flexible intramedullary nails are also used in selected pediatric radius and ulna shaft fractures, particularly when closed reduction and casting cannot maintain acceptable alignment. POSNA materials list flexible intramedullary nailing and plating among surgical options for pediatric forearm shaft fractures. Published pediatric technique literature also describes elastic intramedullary nailing as a reliable method for many pediatric both-bone forearm fractures when operative stabilization is indicated. (posna.org)
Forearm decisions are especially sensitive to rotation. Even modest rotational malalignment can affect pronation and supination, so implant choice must support both bone alignment and functional recovery. In some patterns, plating may provide more direct control; in others, flexible nails may provide adequate stability with less soft-tissue exposure.
Other long bones
Flexible nails may be used in selected humeral or tibial shaft fractures, but these indications are more selective. Pediatric humeral shaft fractures are often treated without surgery unless there are complicating factors such as open injury, vascular concern, floating elbow, or inability to maintain alignment. For tibia fractures, surgeons must weigh alignment, soft-tissue injury, and the risk of growth plate involvement. Device labeling and regulatory classifications also matter: FDA-cleared intramedullary systems may define elastic nails for long bone diaphyseal fractures where the medullary canal is narrow or implant flexibility is important. (posna.org)
Patient and fracture factors that shape implant choice
Flexible nail selection is not based on the implant alone. It is a decision made from the combination of patient age, skeletal maturity, body weight, fracture location, fracture stability, soft-tissue condition, and associated injuries. This is why the same implant may be appropriate in one pediatric femur fracture and unsuitable in another that appears similar to a non-specialist.
| Factor | Why it matters for flexible nail fixation |
|---|---|
| Age and skeletal maturity | Younger children often remodel better and may be treated with casting, while adolescents may need stronger or more rigid fixation depending on size and fracture pattern. |
| Weight | Heavier children place greater mechanical demand on elastic implants, which can increase the risk of malalignment or loss of length control. |
| Fracture stability | Length-stable transverse or short oblique patterns are more favorable; comminution and long obliquity may require plating, rigid nailing, or external fixation. |
| Fracture level | Very proximal or very distal fractures may leave too little working segment for elastic nails to control alignment effectively. |
| Soft-tissue injury | Open wounds, severe swelling, or polytrauma can shift the decision toward external fixation or staged treatment. |
| Growth plate proximity | Entry points and implant paths must avoid physeal damage in skeletally immature patients. |
Professional guidance reflects these boundaries. POSNA describes treatment variation by age, weight, fracture pattern, mechanism, and associated injuries, and notes that unstable fracture patterns may be more difficult to control with flexible intramedullary nails. AAOS guidance for pediatric diaphyseal femur fractures has also emphasized flexible intramedullary nailing for selected children, while newer AAOS quality materials list an updated pediatric diaphyseal femur fracture clinical practice guideline published on August 24, 2026. (posna.org)
Flexible nail vs other fixation options
The most useful way to understand flexible nails is to compare them with the alternatives. No fixation method is best for every fracture. Each construct solves one set of problems while introducing its own limitations.
| Method | Typical strengths | Common limitations |
|---|---|---|
| Flexible nail | Smaller incisions, internal support, useful in selected pediatric shaft fractures, can respect growth plates when properly placed. | Less control in unstable, comminuted, very proximal, very distal, or heavier-patient fractures. |
| Cast or spica cast | No implant, often appropriate for younger children and stable patterns. | Immobilization burden, potential loss of reduction, hygiene and mobility challenges. |
| Plate and screws | Strong control of length, rotation, and alignment; useful for unstable or metaphyseal patterns. | Larger exposure, possible later implant-related symptoms, soft-tissue considerations. |
| Rigid locked intramedullary nail | Strong load sharing for larger adolescents or skeletally mature patients. | Requires careful entry point selection and is not appropriate for many younger children. |
| External fixator | Useful for open fractures, severe soft-tissue injury, damage control, or staged management. | Pin-site care, frame burden, refracture and alignment considerations after removal. |
For the femur, AAOS patient information notes that broken bone pieces with too many fragments may not be successfully treated with flexible nails. Alternatives may include bridge plating, external fixation, traction, or rigid nailing, depending on age and fracture characteristics. This is a practical reminder that flexible nails are not a substitute for fracture-specific planning. (orthoinfo.aaos.org)
Surgical planning and follow-up considerations
Although technique details belong in operative training, several planning principles help explain why flexible nailing succeeds or fails. Surgeons generally assess full-length imaging of the injured bone, evaluate adjacent joints, confirm fracture stability, and choose implant diameter and length according to the medullary canal and fracture location. Many pediatric femur techniques use two nails inserted from medial and lateral entry points so that the elastic forces are balanced. See also: Implants.
Intraoperative imaging is commonly used to guide entry, passage across the fracture, reduction, and final implant position. Nail ends also need careful management because prominent ends can irritate soft tissue. Postoperative immobilization varies. Some children may need a cast or brace, while others may begin controlled motion or protected weight bearing depending on the bone, fracture stability, and surgeon protocol.
Follow-up is not a formality. Pediatric fractures change over time, and alignment, length, rotation, pain, wound status, and callus formation must be monitored. Hardware removal is sometimes considered after healing, especially when nail ends irritate the skin or surrounding soft tissues. AAOS OrthoInfo notes that intramedullary nails may need removal after healing if they cause irritation, and POSNA materials describe soft-tissue irritation at the nail tip as a recognized complication in pediatric flexible nailing. (orthoinfo.org)
Benefits, limitations, and complications
The main benefit of flexible nailing is that it can stabilize selected pediatric long bone fractures with less exposure than plating and, in some cases, less immobilization burden than prolonged casting. For school-age children with suitable femoral shaft fractures, professional education materials often discuss flexible nails as part of the move toward earlier mobilization and shorter hospitalization compared with older traction-and-casting pathways. (orthoinfo.aaos.org)
The limitations are both mechanical and biological. Flexible nails depend on adequate fracture stability, balanced nail placement, and appropriate patient size. If the fracture is too unstable, the child is too heavy for the construct, or the fragments are too close to the bone ends, the nails may not control shortening, angulation, or rotation. Malalignment is not merely a radiographic issue; in the femur it can affect gait, and in the forearm it can affect rotation.
Possible complications include entry-site irritation, pain from prominent nail ends, infection, implant migration, delayed union, malunion, limb-length difference, refracture after premature implant removal, and the need for an additional procedure. Reported complication rates vary widely in published series because studies include different bones, ages, fracture patterns, definitions, and follow-up periods. POSNA summarizes that complications related to flexible intramedullary nailing have been extensively studied and reported across a broad range, reinforcing the need to interpret outcomes in context rather than as a single universal number. (posna.org)
The key takeaway is balanced: flexible nail fixation is a proven and widely taught pediatric technique, but it is not simply a synonym for minimally invasive or low risk. Its value is highest when implant mechanics, pediatric anatomy, and fracture selection all point in the same direction.
Frequently asked questions
Is a flexible nail the same as a titanium elastic nail?
In many pediatric fracture discussions, the terms overlap. Titanium elastic nail, elastic stable intramedullary nail, and flexible intramedullary nail are often used to describe elastic rods inserted into the bone canal. However, exact terminology can vary by manufacturer, material, and regulatory labeling.
Are flexible nails used only in children?
They are most strongly associated with pediatric fracture fixation because children have open growth plates and narrower canals. Some systems may have indications in narrow medullary canals or situations where flexibility is important, but adult fracture fixation more commonly uses rigid intramedullary nails, plates, or other constructs depending on the injury.
Do flexible nails always need to be removed?
No single rule applies. Some implants are removed because the nail end irritates soft tissue, the child has symptoms, or the surgeon’s protocol favors removal after healing. Removal timing must be individualized because premature removal may increase refracture risk in some situations.
Why not use a plate for every pediatric long bone fracture?
Plates provide strong control, especially for unstable fractures, but they may require more exposure and can create different implant-related issues. Flexible nails may be preferred when the fracture pattern is suitable and smaller incisions with elastic intramedullary support can achieve the treatment goals.
What should readers remember about flexible nail fixation?
The implant is only one part of the decision. Age, weight, skeletal maturity, fracture stability, fracture level, soft-tissue injury, and growth plate safety all shape whether a flexible nail is appropriate. The treating orthopedic surgeon must make the final decision based on the individual patient and fracture.