3.3.1 Intramedullary nailing
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1 Types of intramedullary nails
Intramedullary nailing of shaft fractures of the femur, tibia, and humerus is generally accepted as a standard treatment. Indirect reduction and fixation without opening of the fracture site, implant insertion along the mechanical loading axis of the bone, good bone-implant interface and early load sharing to allow weight bearing are clear advantages of intramedullary nailing. The design and application of intramedullary nails have rapidly evolved since the pioneering work of Küntscher in World War II.
1.1 Classic Küntscher nail (tight fitting, reamed, no locking)
The Küntscher nail was a straight, open section nail with a longitudinal slot and no locking holes. Its use was restricted to relatively simple midshaft fractures because stabilization was dependent upon tight contact between the elastic implant and the stiff bone (intramedullary nailing principle) ( Videos 3.3.1-1 – 2 ). Reaming the medullary cavity increases the area of contact between the intramedullary nail and bone and allows insertion of a larger diameter nail. This extends the indication to fractures that are more complex or more proximal or distal to the isthmus in the shaft.
However, the reaming process itself has some inherent biological disadvantages, especially when performed excessively. These include a considerable rise in intramedullary pressure and temperature, increasing the risk of bone necrosis and infection. In the past, these disadvantages limited the use of reamed nailing to fractures with only minor soft-tissue injuries.
1.2 Universal nail (tight fitting, reamed, locked)
The addition of interlocking screws to the intramedullary nail, introduced by Grosse and Kempf, enhanced the mechanical properties of the intramedullary implant. It widened the range of indications to include more proximal or distal fractures, as well as more complex and unstable fracture patterns. However, if the fracture is more distal, more proximal, or more complex, its fixation will mainly depend on the interlocking screws and much less on the principle of circular press fit. The length of the bone-implant construction is still effectively maintained because the interlocking screws prevent shortening and rotation. However, the longitudinal slot in the tubular universal nail results in decreased rotational stiffness and can lead to rotational instability, especially with small diameter intramedullary nails.
1.3 Intramedullary nailing with neither reaming nor locking
Several groups in Europe and North America have treated shaft fractures with significant soft-tissue injuries using solid, small diameter, intramedullary nails, which were inserted without reaming, and therefore, loose fitting. Since these implants (Ender nail, Lottes nail, and Rush pins) were thin and could not be locked proximally or distally, longitudinal and rotational instability resulted, especially in complex fractures. Thus, a major disadvantage was the frequent need for additional external stabilizers, such as plaster casts.
1.4 Intramedullary nailing without reaming but with mandatory locking (unreamed solid or cannulated nails)
There was an obvious need for a small diameter intramedullary nail that could be locked. The absence of a longitudinal slot considerably increases the torsional stiffness of the tubular implant, and also reduces capacity to adapt to the shape of the bone. If the insertion site is not optimal, or the shape and radius of the intramedullary canal diverge from those of the intramedullary nail′s geometry, a proper fit may be a problem. With a smaller diameter (ie, 9 mm) in the femur, the material strength of the intramedullary nail must be reinforced to keep the risk of implant failure as low as possible. These two demands (low stiffness and high-fatigue strength) were met by a change of material, from stainless steel to a titanium alloy. Titanium nails seem to have a beneficial effect on strength, mineralization, and fracture healing at 12 weeks [1]. The higher strength of the material allows the use of larger, 4.2/4.9 mm diameter interlocking screws. The solid cross-section of the intramedullary nail does not add much to its mechanical bending properties, but it has biological advantages. Results of animal experiments indicate that the susceptibility to infection is lower with the solid intramedullary nail compared with the tubular intramedullary nail with its inner dead space [2]. However, a cannulated system allows for the use of a guide wire, which makes intramedullary nail insertion easier.
1.5 Angular stable locking system (ASLS)
Intramedullary nails with standard locking options provide adequate stability in long-bone shaft fractures. In metaphyseal and segmental fractures, however, the wide diameter of the medullary canal and fracture morphology may cause problems with reduction and stable fixation of the short proximal or short distal fragment because circular press fit of the implant in the wide medullary cavity cannot be obtained. Malunion and/or nonunion are common. The improved 3-D design of proximal and distal locking has expanded the spectrum of indications of intramedullary nailing to metaphyseal and even simple articular fractures of the femur, tibia, and humerus [3]. These implants are cannulated and the instrumentation is modular. Relative movement of the main fragments is effectively reduced by angular stable locking screws. Angular stability is produced by a mechanical couple between the locking screws and the nail. This can be achieved by jamming locking screws or by the use of resorbable sleeves inserted into the locking holes of the nail (ASLS) [4].
2 Pathophysiology of intramedullary nailing
2.1 Intramedullary nailing with reaming
2.1.1 Local response
Reaming the medullary cavity causes damage to the internal cortical arterial and venous blood supply, which, in animal experiments, was shown to be reversible within 8–12 weeks [5]. There is a direct correlation between the extent of reaming and the degree of the reduction in cortical blood flow. Reaming also generates heat and may cause thermal bone necrosis. Large reamers and blunt reaming heads should not be used in clinical practice. The reduced blood supply and thermal bone damage during the early weeks after trauma and reaming might contribute to an increased risk of infection, especially in open tibial fractures. Since the femur has a good soft-tissue envelope, femoral shaft fractures are more often closed than open and treatment by intramedullary nailing is more straightforward and less risky than for the tibia. The infection rates for Gustilo type I and type II open fractures of the femur following intramedullary nailing with reaming are 1–2%, whereas for open fractures with extensive soft-tissue injury (Gustilo type III) the infection rates are 4–5%.
There are some biological advantages of intramedullary reaming, as it enhances the bone healing process by:
Increased perfusion and oxygenation in the adjacent soft tissues
Reaming debris has osteogenic and osteoinductive properties
Local “autografting” of bone debris into the fracture site stimulates osteogenesis
Systemic liberation of growth factors
Allowing the insertion of larger (mechanically more stable) diameter nail
Clinical studies [7] demonstrate a possible benefit for reamed intramedullary nailing in patients with closed fractures, whereas the optimal nailing technique for open fractures remains uncertain.
2.1.2 Systemic response
Systemic effects of intramedullary reaming are pulmonary embolization, humoral, neural, immunological, and inflammatory reactions plus temperature-related changes of the coagulation system. Intramedullary pressures exceeding the diastolic blood pressure result in extravasation of bone marrow content into the venous vascular system (fat embolism). Transesophageal echocardiography (TEE) shows the passage of thrombi into the pulmonary circulation. Pulmonary embolization may cause mechanical vascular obstruction. Systemic liberated fatty acids and bone debris additionally induce vasculitis of vessels within the lung [8]. Liberation of inflammatory mediators, such as thromboxane, serotonin and prostaglandins, cause bronchial spasms and vasoconstriction. Due to shunt systems within the lung, fat embolism may also get access to the systemic circulation, evoking cerebral embolization.
Any device introduced into the medullary canal (awl, guide wire, reamer, intramedullary nail) acts as a piston and forces the contents of the medullary cavity both through the fracture gap into the adjacent tissue and into the venous system. Polytrauma patients with chest injury are especially at risk, since the lungs are sensitive to any additional stress in the period immediately after trauma.
Distal venting of the femur has been shown to reduce the intramedullary pressure during reaming by 50–90%. The clinical efficacy of this technique, however, has not been documented in prospective randomized trials.
There is ongoing controversy between those who recommend reamed intramedullary nailing for all patients with severe trauma, and those with concerns about its role in pulmonary impairment in multiple-injured patients [9]. Recent clinical studies [10] found similar rates of pulmonary embolism and no significant difference in the rate of pulmonary response between reamed and unreamed femoral nailing, provided surgery was delayed until the patient was fully resuscitated (early appropriate care). Comparing reamed femoral nailing with plate fixation in multiple-injured patients with head injury showed that nailing did not increase the risk of neurological complications [11].
2.1.3 Reaming, irrigation, and aspiration
The reaming, irrigation, and aspiration (RIA) system was developed to reduce the amount of systemic fat liberation during the procedure of reaming [12]. Irrigation during the reaming procedure reduces the viscosity of the bone marrow and allows suction of the intramedullary content. Reaming using the RIA technique lowers the maximum reaming temperature and causes less sustained increases in intramedullary pressures in comparison to conventional reaming [8]. A significant reduction of fat embolization compared to conventional reaming could be demonstrated in pig femora [12]. However, values were still higher than with external fixation. Whether RIA reduces systemic complications during nailing of femoral fractures in multiple-injured patients still needs further investigation.
Reaming, irrigation, and aspiration are also used for nailing of pathological fractures and for debridement in patients with acute and chronic osteomyelitis. An additional application of RIA is bone harvesting by sucking the reaming eluate through a filter for surgical procedures, such as treatment of bone defects and nonunions. Similar union rates with significant less donor-site pain in comparison to iliac crest harvesting have been reported [13]. However, extensive thinning of the inner cortex of more than 2 mm may be a risk factor for postoperative fracture of the donor site and the surgical and anesthetic teams must be aware that this procedure can result in considerable blood loss.
2.2 Intramedullary nailing without reaming
Small diameter implants are used for intramedullary nail insertion without reaming. The benefits are less heat production, and, although the insertion of thinner implants certainly disturbs the endosteal blood supply, this occurs to a lesser extent. There is also less bone necrosis, which is one of the risk factors for the development of postoperative infection. However, an explicit clinical benefit of unreamed intramedullary nailing in comparison to reamed nailing has not be demonstrated.
A metaanalysis comparing reamed versus unreamed nailing in closed fractures of the tibia showed a significantly lower risk of nonunion, screw breakage, and implant exchange in the reamed nailing group [14]. Reamed nailing of closed fractures seems to be associated with a higher fracture healing [7, 8].
2.3 Current aspects of femoral intramedullary nailing
2.3.1 Isolated femoral shaft fractures
Both methods of intramedullary nailing (reaming and not reaming) are associated with similar generation of emboli. A prospective, randomized, clinical study [15] found no significant differences in pulmonary physiological response or clinical outcome between patients treated with unreamed or reamed femoral nailing.
Other clinical studies have demonstrated significant benefits of reaming compared to unreamed femoral nailing. In a multicenter, prospective, randomized trial [16], intramedullary nailing of femoral shaft fractures without reaming resulted in a significantly higher rate of nonunion compared to intramedullary nailing with reaming. In addition, reaming led to faster healing and a reduced rate of delayed union.
Femoral nailing with reaming remains the gold standard for the treatment of isolated femoral fractures.
2.3.2. Femoral shaft fractures in polytrauma patients
In multiple-injured patients, especially in the presence of chest trauma, the reamed femoral nail has been implicated as a cause of significant disturbance of pulmonary function. Using an unreamed nail reduces but does not abolish pulmonary sequelae. In addition to the pulmonary consequences of intramedullary nailing, systemic effects on the coagulation system and on the inflammatory response with increased levels of interleukin-6 and C-reactive protein have been reported in clinical and experimental studies for both the reamed and the unreamed femoral nail [17]. No significant differences in the incidence of acute respiratory distress syndrome (ARDS) were observed following reamed and unreamed nailing in a series of 315 multiple-injured patients with femoral fractures, treated with a nail within 24 hours after injury [18].
To limit the physiological insult resulting from operative treatment after trauma, a move from early total care (ETC) to damage-control orthopedics (DCO) in patients with multiple injuries has occurred. Damage-control orthopedics starts with initial external fixation of femoral shaft fractures with a later conversion to an intramedullary nail [19]. This concept has been judged as a viable alternative to obtain temporary fracture stabilization in polytrauma patients, especially those with concomitant injuries to the head, chest, or an exceptionally high injury severity score (ISS) [17, 20].
Definitive primary femoral stabilization by intramedullary nailing imposes considerable stress on a multiple-injured patient with blunt trauma. Principles of management include adequate resuscitation with appropriate timing of reconstruction depending on the patient′s physiological response.
Vallier et al [10] defined clinical conditions that warranted delay for definitive fracture fixation in a retrospective study on 1442 patients with pelvic, spinal, and/or femoral shaft fractures. Chest injury was identified as the greatest predictor of pulmonary complications. The authors emphasized the importance of adequate resuscitation and correction of acidosis before nailing. They recommended early definitive fixation of unstable fractures of the axial skeleton and long bones within 36 hours in patients who demonstrated response to resuscitation. Lactate < 4.0 mmol/L, pH > 7.25, and BE > 5.5 mmol/L were indicators to proceed with definitive fracture fixation.
Pape et al [21] described four pathophysiological cascades, associated with the development of posttraumatic immune dysfunction and endothelial damage. They recommended assessing for hemorrhagic shock, hypothermia, coagulopathy, and soft-tissue injury in all patients with multiple blunt trauma and long-bone fractures. Clinical parameters that characterize an unstable patient (as opposed to a stable or a borderline patient) include blood pressure < 90 mm Hg, body temperature < 33° C, platelets < 90,000, and significant soft-tissue trauma (major extremity injuries, crush trauma, severe pelvic fracture, thoracic and abdominal trauma with AIS > 2).
Even when the initial insult of trauma (the “first hit”) is moderate, a “second hit” resulting from surgical procedures with inappropriate timing can aggravate the overall amount of damage and may lead to an increased morbidity and mortality [9]. Pape et al [21] suggested categorizing patients into one of four categories (stable, borderline, unstable, in extremis) and adapting the treatment approach accordingly. In patients who are unstable or in extremis, damage-control surgery, including rapid external fixation of long-bone fractures, followed by early secondary definitive fracture stabilization, typically within 5–7 days, is recommended.
In patients with delayed definitive fracture fixation (> 2 weeks), or if there is pin-site infection, converting provisional external fixation to intramedullary nailing should include a short fixator-free interval (pin holiday) [19] of 2–3 days, during which patients are placed in skeletal traction to reduce the risk of infection.
2.4 Current aspects of tibial intramedullary nailing
Intramedullary nails are the treatment of choice for most unstable tibial diaphyseal fractures. The incidence of intravasation of intramedullary content and pulmonary embolization after tibial fractures is significantly lower than after femoral shaft fractures (tibia 19% versus femur 78%) as the venous drainage system of the tibia is less extensive than that of the femur.
The use of intramedullary nails with reaming for the treatment of closed tibial fractures results in shorter time to union without an increase of postoperative complications [22]. A higher rate of malunions after unreamed intramedullary nailing has been reported than after reamed intramedullary nailing [22]. A reamed procedure for stabilization of the tibia did not increase the risk of complications in open tibial fractures of the Gustilo type I–IIIA [22].
The SPRINT blinded randomized trial [7] compared healing rates and complications after reamed and unreamed intramedullary nailing of open and closed tibial fractures in a large series of 1,319 adults. The study demonstrated a possible benefit for reamed nailing in closed fractures with fewer screw breakages, whereas there were no significant differences between both procedures in patients with open fractures. The reoperation rate in response to infection was not significantly different between both groups [7].
2.5 Conclusion
The systemic impact of intramedullary nailing of femoral shaft fractures seems to be significantly higher compared to tibial fractures. There is good evidence that reamed femoral intramedullary nailing is the method of choice for isolated femoral shaft fractures. In polytrauma patients, adequate resuscitation before nailing is essential. Early definitive intramedullary stabilization of the femur should not be performed in patients in extremis or who do not respond to resuscitation and continue to have uncorrected acidosis, coagulopathy, or severe hypothermia. The preferred approach is damage-control surgery with temporizing external fixation.
Stabilization of tibial fractures is mostly influenced by local soft-tissue factors. For closed tibial fractures, reamed intramedullary nailing is the method of choice. In open fractures the method of choice remains controversial.
3 Implants
3.1 Femur
The universal femoral nail is a curved, slotted intramedullary nail made of stainless steel and is still widely used in many parts of the world. It has a static and dynamic locking option proximally, and two static locking options distally. The femoral version of the simplified universal nail (SUN) is an unslotted, tubular version of the universal femoral nail. Both the SUN and the SIGN nail have been designed for hospitals without an image intensifier, with a simple mechanical aiming device to allow for interlocking without image guidance.
The unreamed femoral nail is a solid titanium nail with a variety of proximal locking options (static, dynamic, spiral blade, and miss-a-nail). It is curved and requires an entry point in line with the medullary cavity. The cannulated femoral nail allows the insertion along a guide wire. The entry point in the piriformis fossa has been criticized for being technically demanding, with a possible risk of compromising the blood supply to the femoral head. This led to the development of the antegrade femoral nail, which has a bend in the proximal part that allows for insertion at the tip of the greater trochanter. The lateral femoral nail has a starting point even more lateral to the tip of the greater trochanter. The very lateral starting point facilitates nail insertion. The nail has a helical design and rotates by approximately 90° during insertion. Standard and reconstruction locking options provide stability in diaphyseal as well as in subtrochanteric and segmental fractures. The adolescent femoral nail is used in small stature (adolescent) patients with small diameters of the medullary cavity.
The distal femoral nail is specifically designed for retrograde insertion. The proximal locking is performed anteriorly in long nails and lateral to medial in short nails. As part of the expert nail system the retrograde/antegrade femoral nail can be introduced through an antegrade as well as a retrograde entry point. It is cannulated and allows for optional spiral blade locking at the level of insertion with retrograde insertion.
For fractures in the proximal femur (subtrochanteric or intertrochanteric), intramedullary nail-screw combinations are available in different dimensions for different indications. The original proximal femoral nail with two parallel femoral head screws of different sizes has mainly been used outside the US, while in the US the trochanteric femoral nail is popular. The trochanteric femoral nail has a double spiral blade configuration for improved rotational stability in the femoral head/neck area. This design has now been integrated into the proximal femoral nail, resulting in the proximal femoral nail antirotation. Both the proximal femoral nail antirotation and the proximally smaller sized trochanteric femoral nail-advanced can be used with either a blade or a head-neck screw. Perforations at the tip of the blade or screw allow for cement augmentation that aims to reduce failure rates in osteoporotic bone by increasing the implant to bone surface contact area.
Every specific nail has its own specific entry point. Each specific entry point has advantages and potential complications. The piriformis starting point, which is collinear with the axis of the femoral medullary canal, is appropriate for nails that are straight in the AP plane (eg, unreamed femoral nail). Piriformis start nails are better for preventing varus deformity and offer excellent stability specifically in subtrochanteric fractures. Occasional femoral neck fractures have been described after nailing through the piriformis fossa. Concern exists in young patients with an open proximal femoral growth plate about the potential risk of avascular necrosis, resulting from intraoperative damage to the medial circumflex femoral artery [23].
Nails with a lateral bend have a more lateral starting point, usually at or just lateral to the tip of the greater trochanter. Inserting a nail through a lateral entry point is mechanically stable, technically easier to perform and causes less damage to the muscles and vascular structures [24].
Reamers for nails inserted into the tip of trochanter tend to lateralize the center of the entry point as the lateral bone is softer. This can result in varus malalignment when the nail is inserted and these nails must be used with caution for subtrochanteric fractures.
In a prospective randomized trial, Stannard et al [25] compared functional outcome with the piriformis fossa and the greater trochanter entry point in the treatment of femoral shaft fractures. The tip of the trochanter starting point resulted in a better outcome at 6 months but function was equal at 1 year. Pain scale values were equal in both groups [25]. From the technical perspective, operative time and image intensifier time were significantly shorter and incision length was smaller with the trochanter starting point, indicating that nailing through the tip of trochanter entry is a simpler procedure.
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