Trochanteric Fractures: Intramedullary Devices

11 Trochanteric Fractures


Intramedullary Devices




Orthopaedic surgeons are fundamentally reconsidering the fracture fixation objectives that have defined the standard of care since the late 20th century. The principles pioneered in the 1960s focused on primary fracture healing and did not ascribe sufficient weight to the importance of secondary fracture healing factors. Open reduction and internal fixation with precise realignment of fracture fragments were the dominant treatment strategies. New materials and revised surgical techniques developed since the mid-1990s have allowed for innovative approaches in which the biologic aspects of fracture fixation are paramount.


Intramedullary nailing was introduced in 1940 by Küntscher.1 He advanced the technique of closed intramedullary nailing by using an open section, straight, cloverleaf nail for femoral shaft fractures. Since the 1940s, intertrochanteric fractures have been treated with intramedullary nailing, and intramedullary fixation became standard treatment for femoral shaft fractures in the 1950s. In 1967, Zickel2,3 produced good results with intramedullary nailing for fixation of proximal femur fractures. Antegrade nailing became the standard fixation mode for these fracture types after the introduction of the Gamma nail in 1988, a trochanteric nail with an interlocking lag screw.4


Over the years, intramedullary fracture fixation became increasingly popular, and indications expanded to tibial and humeral shaft fractures. Since 1990, in response to advances in nailing systems, designs, and techniques, the indications for intramedullary fracture fixation have spread to the metaphyseal area of the long bones. Varying the distal and proximal screw positioning within the nail, the use of “Poller” screw techniques5 (using blocking screws to narrow the metaphyseal canal, for increased nail stability), and the availability of nails with percutaneous insertable interlocking screws have made intramedullary nailing the preferred treatment for diaphyseal and metaphyseal fractures in the proximal and distal third of the long bones.


Discussion is ongoing about extracapsular hip fracture treatment in terms of plate or nail preference. The rationale for plating intertrochanteric fractures may be explained by the widespread treatment of intracapsular hip fractures with a sliding hip screw (SHS) system: the technique is familiar. Another reason may relate to problems inherent in early cephalomedullary nail design for the proximal femur.6 Outcomes with the early cephalomedullary nails were not significantly better compared with hip screw outcomes, and the nails commonly produced complications such as femoral shaft fractures at the tips of short nails.79


In contrast to other fracture sites, however, the proximal femur provides the surgeon with a combined head-neck fragment, which represents a solid and durable fixation matrix for nail implantation. The development of second-generation nails with a cephalomedullary component made possible the direction-guided implantation mode of interlocking screws into the femoral head that allows stable fixation of the femoral head-neck complex.


Modern nail design and newer surgical techniques have made intramedullary nailing an increasingly attractive procedure for extramedullary hip fracture fixation.10 The biomechanical advantages of this approach have led to the development of various implants that represent the best current treatment for intertrochanteric fractures in a rising number of hospitals all over the world.




Rationale for Intramedullary Nailing of Extracapsular Hip Fractures


Fracture fixation with intramedullary nails matches the Arbeitsgemeinschaft für Osteosynthesefragen (AO) principles for fracture treatment that have been followed since the 1960s: reduction, stability, preservation of blood supply, and early active mobilization. The biologic objectives of fracture treatment are achievable with percutaneous, minimally invasive intramedullary nailing techniques that allow biologic osteosynthesis patterns with a minimum of collateral damage to the local soft tissue surrounding the fracture site.


The need for intramedullary nailing fixation of intertrochanteric fractures becomes even more apparent when the effect of local forces is understood. High compressive forces along the medial cortex (Adams arch) and high tensile forces at the lateral cortex of more than 1000 psi create high biomechanical stress in the area of the proximal femur.11,12 The chosen implant must be adequately stable to maintain reduced fracture positioning until the fracture site is consolidated. In these cases, intramedullary nailing is clearly advantageous for fracture fixation. In biomechanical testing, intramedullary nails had greater stiffness and provided more rigid fixation with higher combined bending and compressive loads compared with plates.13 This effect is based on the design and location of the implant. Compared with extramedullary implants, intramedullary devices create a shorter lever arm because of their centered position in the shaft and subsequent position adjacent to the head-neck complex. The shorter lever arm results in decreased torque, which itself reduces the risk of mechanical failure until the fracture is completely consolidated.14


In comparison with extramedullary implants such as plates, intramedullary devices shift the weight-bearing axis and forces to the medial aspect of the proximal femur, with resulting load sharing.1518 The main advantage of intramedullary fracture fixation in intertrochanteric fractures is the lateral buttress effect provided by the nail itself. The proximal part of the nail acts as an intramedullary brace in the greater trochanter. It provides stable fixation against medialization of the shaft and total collapse of the fracture fragments, fixation that cannot be provided by monocortical plating. This characteristic makes the use of extramedullary implants a suboptimal fracture fixation strategy in unstable and reverse oblique fractures (AO/OTA 31A3 fractures).19 In unstable and reverse oblique fracture types, extramedullary implants do not offer any additional fixation of the proximal fragment besides the lag screw. Unstable intertrochanteric fractures treated with the SHS or other extramedullary implants have significantly higher rates of malunion and shortening of the femoral neck and shaft.20,21 Because of these complications, many investigators have reported that the SHS and other extramedullary implants are not suitable for these fracture types.9,2227 Based on the known biomechanical advantages of intramedullary nailing in treating femoral shaft fractures, newer-generation cephalomedullary nails have come into use for intertrochanteric fracture treatment.2832



Indication and Fracture Types


According to the AO/Orthopaedic Trauma Association (OTA) classification, extracapsular hip fractures are classified as 31A fractures.33 Even though these injuries comprise a heterogeneous group of stable and unstable fractures with different mechanical characteristics, intramedullary nailing is indicated for all fractures types in this group. Type 31A fractures are subclassified into groups A1, A2 and A3, which can be further divided into subgroups.






Operative Technique


The choice of the right implant to fix intertrochanteric fractures is an important factor in successful treatment. Equally important are the surgical approach and the fixation technique. Successful treatment starts with correct patient positioning, fracture reduction (accounting for varus dislocation and dislocation of flexed fragments), appropriate skin incision, choice of the correct nail entry point, perfect lag screw positioning within the femoral head-neck fragment, and distal locking.




Reduction


Adequate fracture reduction is accomplished while the patient is in the supine position on the fracture table. Fracture reduction must take place before proximal reaming is performed. Once reaming has occurred, the nail will follow the direction of the reamed canal, and the proximal fragment will be fixed in varus or flexion deformity.



Closed and Percutaneous Reduction Techniques


Proper reduction for most hip fractures is achieved by applying slight traction, adduction, and internal rotation to the lower limb on the fracture site until the patella is facing supine. The fractured leg should be positioned slightly upward. If radiographs do not show satisfactory reduction, the surgeon can modify these vectors to achieve better results. In unstable fractures, this approach may be impractical, because dislocation cannot be addressed properly by fracture table traction force modification.



Gaining Control of Flexion Dislocation


In patients with a remaining proximal fragment in flexion dislocation, the surgeon has several options for fracture reduction. The most elegant one is to insert a ball spike through a 5-mm stab incision over the ventral thigh. The ball spike applies down-vectored force to the malaligned fragment and leads to fracture reduction. Once adequate reduction is obtained, proximal reaming and nail insertion can be performed (Fig. 11-6).



An additional option for fracture reduction in flexion deformity is the use of radiolucent reduction aids mounted on the fracture table that push the shaft upward. If these aids are not available, a wooden crutch can be packed in sterile fashion and positioned under the limb. Reduction is obtained by lowering the table to the crutch (Fig. 11-7).


Aug 24, 2016 | Posted by in ORTHOPEDIC | Comments Off on Trochanteric Fractures: Intramedullary Devices
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