Residency · Residency · Orthopedic Surgery

Intramedullary Nailing: Principles and Techniques

Biomechanical Principles

Load-Sharing Device

Intramedullary (IM) nails function as internal splints that share mechanical load with the bone, distinguishing them from plates which may function as load-bearing devices. They provide relative stability, stimulating secondary bone healing with callus formation. The nail itself resists bending and rotational forces, while interlocking screws at each end resist shortening and provide additional rotational control.

Advantages Over Plating

IM nailing offers several biomechanical and biologic advantages over plate fixation for diaphyseal fractures. The nail is positioned along or near the mechanical axis of the bone, resulting in a much shorter moment arm compared to plates applied eccentrically to the cortex. The closed insertion technique preserves the soft tissue envelope and minimizes periosteal stripping, maintaining the biologic environment for healing. These advantages translate into earlier weight-bearing for many clinical scenarios and lower infection rates in open fractures compared to plate fixation.

Nail Design

Modern nail design incorporates several variables. Nails may be solid or cannulated (the latter allowing passage over a guidewire for insertion). The cross-section may be slotted (permitting controlled deformation) or closed. Most contemporary nails are manufactured from titanium alloy, which has a lower modulus of elasticity than stainless steel and thus produces less stress shielding, though stainless steel offers greater stiffness and higher fatigue strength. Nail diameter is a critical design parameter because bending stiffness is proportional to the fourth power of the radius. The nail must be of sufficient length to span from the entry point to the distal metaphysis.

Reaming

Reamed Nailing

Reaming involves progressively enlarging the medullary canal before nail insertion. This permits use of a larger-diameter nail, which significantly increases construct stability. The reaming debris acts as autologous bone graft at the fracture site, potentially enhancing healing. Increased cortical contact between the nail and the inner cortex improves rotational stability. The trade-off is that reaming generates endosteal heat and temporarily destroys the endosteal blood supply, though this recovers within weeks as periosteal collateral flow compensates.

Unreamed Nailing

Unreamed nailing inserts a smaller-diameter nail without prior canal preparation. It preserves the endosteal blood supply and produces less cortical necrosis. Historically, it was advocated for open fractures and polytrauma patients to reduce the pulmonary inflammatory insult associated with reaming and intramedullary pressurization.

Reamed vs. Unreamed: The Evidence

The SPRINT trial provided important evidence on this debate. For closed tibial fractures, reamed nailing was associated with lower reoperation rates. For open tibial fractures, no significant difference in reoperation rates was found between reamed and unreamed techniques. Current consensus favors reamed nailing for most closed fractures because the larger nail provides superior mechanical stability. For open fractures, reamed nailing is increasingly accepted when combined with adequate debridement. The theoretical concerns about a "second hit" inflammatory response from reaming in polytrauma patients have not been consistently supported by high-level evidence.

Entry Points

Femur -- Antegrade

Two principal entry points exist for antegrade femoral nailing. The piriformis fossa is the traditional entry point, positioned directly in line with the femoral canal axis. However, it risks damage to the medial femoral circumflex artery (the primary blood supply to the femoral head) and is less commonly used today. The greater trochanter tip is now the most commonly used entry point with modern trochanteric-entry nail designs. The nail incorporates a proximal lateral bend to compensate for the slightly lateral starting point. This approach offers easier surgical access and less risk to femoral head vascularity, though it carries a risk of valgus malalignment if the entry point is placed too laterally. In young patients with open growth plates, the greater trochanteric apophysis should not be violated.

Femur -- Retrograde

Retrograde femoral nailing enters through the intercondylar notch, positioned anterior to the PCL origin at Blumensaat's line. Fluoroscopic guidance in both AP and lateral planes is essential. Specific indications include ipsilateral femoral neck and shaft fractures (allowing separate fixation of each), pregnancy (avoiding abdominal radiation), morbid obesity, bilateral femoral fractures, floating knee injuries, and ipsilateral acetabular fractures. Contraindications include active knee infection, severe articular cartilage damage, and a canal too narrow to accept the nail. Potential concerns include knee pain, risk of knee sepsis from violating the joint, and articular cartilage damage at the entry site.

Tibia -- Antegrade

Several approaches exist for tibial nail insertion. The parapatellar approach (medial or lateral) retracts the patellar tendon with the knee in flexion. The transpatellar tendon-splitting approach is less commonly recommended now due to its association with anterior knee pain. The suprapatellar (semiextended) approach has gained considerable popularity. The knee is positioned in only 15-20 degrees of flexion, and the nail is inserted through the quadriceps tendon and patellofemoral joint. This approach improves access for proximal third fractures, provides better alignment control, and reduces the risk of apex anterior angulation that plagues infrapatellar approaches for proximal fractures. Concerns about chondral damage appear to be minimal based on current evidence. On the AP fluoroscopic view, the entry point should be in line with the lateral tibial spine. On the lateral view, it should be at the anterior cortex slope.

Humerus

Antegrade humeral nailing enters through the rotator cuff (supraspinatus tendon) at the greater tuberosity, carrying risks of rotator cuff dysfunction and shoulder pain. Retrograde entry through the olecranon fossa risks supracondylar fracture and has limited indications. Overall, humeral nailing is less commonly performed than plating because of higher rates of shoulder pain and functional impairment at the entry site.

Interlocking Strategies

Static Locking

Static locking places interlocking screws through nail holes both proximally and distally, controlling length, rotation, and alignment. This is the standard configuration for most fractures and creates a fixed-length construct that prevents shortening.

Dynamic Locking

Dynamic locking places screws on only one side of the fracture (typically the side farther from the fracture). This configuration allows axial micromotion and compression at the fracture site during weight-bearing. It is reserved for fractures with good cortical contact where shortening is not a concern. Dynamic locking may be used as the primary fixation strategy or as a secondary procedure (dynamization).

Dynamization

Dynamization is the removal of interlocking screws on one side of the fracture (usually the side closest to the fracture) to convert a static construct into a dynamic one. It is performed for delayed union, typically at 8-12 weeks, with the goal of allowing axial loading and compression to stimulate callus formation. The risks include uncontrolled shortening (particularly in comminuted fractures) and loss of rotational control. Dynamization is not indicated for fractures with significant bone loss or comminution.

Blocking (Poller) Screws

Blocking screws are placed in the bone adjacent to the nail within the wide metaphyseal canal. They narrow the effective canal diameter, redirecting the nail trajectory and improving both reduction and stability. These screws are critical for proximal and distal tibial fractures where the wide metaphysis predisposes to malalignment. They are placed on the concavity of the deformity to "block" the nail from drifting into the malaligned position.

Femoral Shaft Fractures

Indications for Nailing

Intramedullary nailing is the gold standard treatment for diaphyseal femoral fractures in adults. Antegrade nailing is the most common approach, with retrograde reserved for specific clinical scenarios.

Technique Highlights

The patient is positioned in lateral decubitus or supine on a fracture table. The fracture is reduced by traction and manipulation before nail insertion. The entry point is verified on both AP and lateral fluoroscopy. The canal is reamed sequentially to 1.0-1.5 mm above the intended nail diameter. Static locking is performed with both proximal and distal interlocking screws. Rotation is confirmed by comparing hip and knee fluoroscopic images with the contralateral side.

Complications

Malalignment, particularly rotational (which is the most commonly missed deformity and must be assessed clinically), is the most frequent technical complication. Ipsilateral femoral neck fractures may be missed if dedicated hip radiographs are not obtained before and after nailing. Heterotopic ossification can develop at the entry site. Knee pain is common with the retrograde approach. Nail failure or breakage at the fracture site indicates delayed union or nonunion requiring revision.

Tibial Shaft Fractures

Indications

Intramedullary nailing is indicated for displaced or unstable tibial shaft fractures, open fractures (after debridement), cases of failed nonoperative management, and polytrauma patients requiring early stabilization.

Proximal Third Challenges

The wide proximal tibial metaphysis makes malalignment (apex anterior angulation and valgus) a common problem with standard nailing techniques. Solutions include using the semiextended (suprapatellar) approach, placing blocking screws, using a unicortical plate as a reduction aid, and employing multiplanar provisional fixation with K-wires. The lateral entry point bias tends to push the nail into valgus, which is counteracted by placing blocking screws on the medial side.

Distal Third Challenges

Distal tibial fractures present similar malalignment risks as proximal fractures due to the widening metaphysis. Blocking screws are essential for maintaining alignment. Fibular fixation may help restore length and improve tibial alignment. If acceptable alignment cannot be achieved with the nail alone, supplemental plating should be considered.

Complications of Intramedullary Nailing

Infection

Infection rates with IM nailing are lower than with open plating for diaphyseal fractures, approximately 1-2% for closed fractures and higher for open fractures in proportion to the Gustilo-Anderson grade.

Malunion / Malalignment

Rotational malunion is the most commonly missed deformity because it is difficult to detect on standard radiographs and requires clinical assessment. Valgus and apex anterior angulation are particular problems in proximal tibial fractures. Prevention depends on proper entry point selection, use of blocking screws, and meticulous intraoperative alignment verification.

Hardware Failure

Interlocking screw breakage may paradoxically be a sign of healing, as it indicates increased load transfer through consolidating bone. In contrast, nail breakage at the fracture site indicates nonunion and requires revision surgery.

Fat Embolism and Pulmonary Complications

Intramedullary reaming forces marrow contents (fat, marrow elements) into the venous circulation. This can rarely cause fat embolism syndrome, presenting with the classic triad of petechiae, hypoxia, and altered mental status. Oxygen saturation should be monitored intraoperatively during reaming. Slower reaming and unreamed techniques may reduce the embolic load.

Anterior Knee Pain (Tibial Nailing)

Anterior knee pain is reported in 10-70% of patients after tibial nailing, making it the most common long-term complaint. Its etiology is multifactorial, involving the entry site disruption, patellar tendon injury, infrapatellar nerve damage, and nail prominence. The suprapatellar approach may reduce rates, though evidence continues to evolve. Nail removal after fracture healing improves symptoms in some patients.

<image>An anatomical illustration showing the entry points for antegrade femoral nailing. Display an anteroposterior view of the proximal femur with two entry points marked: (1) the piriformis fossa entry, shown in line with the femoral canal axis, and (2) the greater trochanter tip entry, shown slightly lateral with the nail's proximal lateral bend compensating for the offset. Include the relevant vascular anatomy (medial femoral circumflex artery) and label the femoral head, neck, and trochanter.</image>

<image>A diagram illustrating the concept of blocking (Poller) screws in a proximal tibial fracture treated with intramedullary nailing. Show an AP and lateral view of the proximal tibia with a nail in situ. Demonstrate how blocking screws placed adjacent to the nail in the wide metaphysis redirect the nail trajectory and prevent valgus and apex anterior malalignment. Show the incorrect nail position without blocking screws (malaligned) versus the corrected position with blocking screws.</image>

<image>A comparison illustration of reamed versus unreamed intramedullary nailing of a tibial shaft fracture. On the left, show the reamed technique with sequential reamers enlarging the canal, a larger-diameter nail with good cortical contact, and debris at the fracture site acting as bone graft. On the right, show the unreamed technique with a smaller-diameter nail, preserved endosteal blood supply, and less cortical contact. Label the key differences in each approach.</image>

Clinical Pearls

Dedicated hip radiographs (AP pelvis or dedicated hip views) must always be obtained before and after femoral nailing to rule out associated femoral neck fractures, which can be catastrophic if missed. Blocking (Poller) screws are the most important tool for achieving and maintaining reduction in metaphyseal fractures treated with IM nailing. Reamed nailing is the standard of care for closed femoral and tibial shaft fractures because the larger nail diameter provides superior mechanical stability. The suprapatellar approach in semiextension improves alignment in proximal tibial fractures compared to infrapatellar techniques. Rotation must be assessed intraoperatively by comparing the cortical step sign on fluoroscopy and clinical examination of limb rotation. Dynamization should not be performed in fractures with significant comminution or bone loss because of the risk of uncontrolled shortening. Anterior knee pain remains the most common long-term complaint after tibial nailing, and patients should be counseled preoperatively. The entry point determines the final alignment; even small errors in starting point produce significant angular deformity in the finished construct.

References

• Bhandari M, et al. (SPRINT Investigators). Randomized trial of reamed and unreamed intramedullary nailing of tibial shaft fractures. J Bone Joint Surg Am. 2008;90(12):2567-2578.
• Ricci WM, et al. Angular malalignment after intramedullary nailing of femoral shaft fractures. J Orthop Trauma. 2001;15(2):90-95.
• Krettek C, et al. The use of Poller screws as blocking screws in stabilising tibial fractures treated with small diameter intramedullary nails. J Bone Joint Surg Br. 1999;81(6):963-968.
• Tornkvist H, Hearn TC, Schatzker J. The strength of plate fixation in relation to the number and spacing of bone screws. J Orthop Trauma. 1996;10(3):204-208.
• Winquist RA, Hansen ST Jr. Comminuted fractures of the femoral shaft treated by intramedullary nailing. Orthop Clin North Am. 1980;11(3):633-648.

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