Selection of internal fixation for intertrochanteric fracture of the femur
Femoral intertrochanteric fracture is one of the most common hip fractures in middle-aged and elderly people, and is also known as the last adult fracture in the West. The characteristics of these fractures are: they are most common in middle-aged and elderly people; they are often combined with more medical diseases such as hypertension and heart disease; and they are caused by low energy and life injuries. After the fracture, the patient often needs to be bedridden for a long time due to local pain and other factors, which brings great inconvenience to the patient’s daily life and work, and long-term bedridden can bring a series of complications, such as crushing pneumonia and deep vein thrombosis of the lower limbs. The goal of treatment of intertrochanteric fractures is to allow patients to guide early bed mobility, thus minimizing complications. The literature demonstrates that conservative treatment has a higher rate of disability and mortality than surgical treatment. In recent years, with the improvement of perioperative management of elderly patients and the improvement of internal fixation devices, surgical treatment is favored for these fractures. The methods of surgical treatment are: extramedullary fixation, intramedullary fixation and external fixation frame. Liu Zhao, Department of Orthopedics, Xuanwu Hospital, Capital Medical University
I. Extramedullary fixation
1 Dynamic hip screw (DHS: Dynamic hip screw)
DHS is an internal fixation device specially designed for intertrochanteric fracture of femur. The screw through the fracture segment is connected to the plate placed on the lateral side of the upper femoral segment by a sleeve, and the load on the femoral head can be decomposed into two parts: inversion of the fracture segment and downward pressure along the screw axis. The DHS internal fixator structure with sliding screws and lateral plates firmly fixes the distal and proximal ends of the fracture with high bending strength, while allowing for inter-end compression and restoring internal stability with few complications, and was once considered the “gold standard” for the treatment of intertrochanteric fractures.
The DHS allows the fracture to move along the sliding femoral neck screw to produce inlay, but due to its eccentric fixation characteristics, it cannot transmit compressive stresses through the femoral spine and is prone to screw bending and fracture. The relative contraindications of DHS are: (1) no effective structural anti-rotation effect, it cannot effectively prevent the fracture segment from rotational displacement; (2) the fracture is not rotatably displaced; and (3) the fracture is not rotatably displaced. (ii) in osteoporotic patients, especially when the integrity of the femoral spur is compromised, the screw is prone to cutting out of the bone, leading to endograft failure. Currently, the accepted recommendation is to use DHS for stable intertrochanteric fractures.
2 Dynamic condyle screw (DCS: Dynamic condyle screw)
The DCS is a compression and sliding screw that allows the fracture to slide along the sliding tension screw, resulting in compression of the fracture end and stress stimulation of the fracture end to accelerate fracture healing. The DCS is placed on the lateral side of the upper femur and acts as a tension band. It is a simple instrument, easy to operate, and does not expose the fracture end, which protects the blood flow of the fracture, minimizes incision trauma and bleeding, and conforms to the principle of biological fixation.
The DCS is designed at an angle of 95° and is fixed in the lower half of the greater trochanter, reducing the complications of screw cutting of the femoral head. In type III and IV intertrochanteric fractures, which involve posterior medial comminuted fractures, hip inversion and posterior tilting of the femoral head are likely to occur, rendering the internal fixation unstable. In the management of these types of fractures, DCS has a significant advantage over DHS in that the two-hole tension screw above the DCS plate can easily reset and fix the posterior medial fracture fragment, which increases the strength of internal fixation. Some scholars believe that for type III and type IV fractures with medial defect in the proximal femur and obvious displacement of the lesser trochanter, DCS should be used for internal fixation with tension screws after repositioning, which can significantly increase the end stability and make the body function well and facilitate the patient’s early weight-bearing kinetic fracture.
3 LISS plate (Less Invasive Stablisation System)
The LISS plate as a new internal fixation technique is now widely used in complex distal femoral fractures and proximal tibial fractures, and it is a very effective internal fixation modality for the treatment of complex distal femoral and proximal tibial fractures.
DHS or DCS fixation can maintain the angular stability, but it requires not only the cortical integrity of the entry point of the compression nail, but also its poor resistance to rotation, even though this deficiency can be corrected by the addition of a long tension screw driven in parallel. The anatomical plate is simple to operate and the fracture is well repositioned, but there is micro-movement between the screw and the screw hole, and the load between the screws is uneven, and loosening, plate fracture, and fracture re-displacement and screw extraction are likely to occur under pressure load, which is not suitable for early functional exercise.
The LISS has solved the limitations inherent in the above internal fixation, and the locking device composed of 5mm thick screws and wide plates makes it a solid one-piece fixation of the fracture end, which plays the role of a stable brace, not only can maintain the cervical stem angle and prevent hip inversion, but also avoid screw extraction, nail breakage and plate fracture. The main advantages of LISS are: ① The LISS splint for femur can meet the requirements of internal fixation of proximal femur fracture from biomechanics and anatomy. The LISS plate relies on the interlocking of the bone and plate to achieve stability, avoiding the pressure of the plate on the periosteum, protecting the periosteal blood supply, and providing a good biological environment for fracture healing. The interlocking between bone and plate can prevent angulation and increase the stability and extraction resistance of screw fixation.
II. Intramedullary fixation
1 Asia-Pacific type proximal femoral intramedullary nail (Asian Intramedullary Hip Screw, Smith-Nephew, referred to as Asian nail)
Asia IMHS is an intramedullary fixation design for proximal femur fractures. The main nail has a proximal diameter of 16.25 mm and a tension screw diameter of 11.0 mm. The proximal end of the main nail is turned out at 4° to facilitate nailing from the tip of the greater trochanter, and the oval hole design provides dynamic or static fixation of the distal locking nail, which can be used selectively during surgery. Only one 11.0 mm diameter tension screw is screwed into the femoral head, which simplifies the operation and shortens the operative time while reducing the exposure of the patient and surgeon to radiation; the presence of a sliding trocar allows for a decreasing trend in the mechanical transmission of the tension screw and allows for intraoperative compression of the fracture end by using the pressure screw in relation to the trocar.
The Intramedullary Hip Screw (IMHS Asian Nail) is a good combination of tension screw and intramedullary fixation techniques, especially for intraoperative compression, reducing the incidence of caudal withdrawal and postoperative local pain. In addition, the Asian nail is designed with a sleeve, which is tolerant to the nail length of the tension screw and allows for optimal length, which is advantageous in the treatment of intertrochanteric fractures in the elderly.
2 PFN-A (proximal femur nail- antirotation, AO)
Composition and characteristics of PFNA: 1) The proximal end of the PFNA nail is 17 mm in diameter with a 6° proximal valgus arc, which is compatible with the anatomical pattern of the proximal femur and can be inserted in the distal femur without marrow expansion. The distal locking nail has a long distance from the distal end of the main nail and is designed with a flexion-reducing groove at the distal end to reduce stress concentration and decrease the incidence of femoral fractures. Distal locking is possible with static (oblique) or dynamic interlocking. The PFNA system is available with multiple primary nails of different diameters to avoid medullary expansion. The standard intramedullary nail length is 240 mm, with a minimum length of 170 mm and a shorter length of 200 mm. extended PFNA lengths of 300, 340, 380, and 420 mm are available for patients with subtrochanteric fractures and combined mid-superior femoral fractures. The most special feature is the spiral blade at the front end of the proximal locking nail, which is 80-120 mm in length. when the spiral blade of the PFNA is inserted, the bone around the screw is not removed but compacted by the spiral blade, thus obtaining a good anchorage, which is important in elderly patients with osteoporotic fractures.
The advantages of PFNA over conventional proximal femoral intramedullary nailing (PFN) are as follows: (1) only one proximal locking nail needs to be drilled in PFNA, whereas PFN requires drilling of proximal tension screws and anti-rotation screws, and the time and number of fluoroscopic views are significantly reduced in PFNA. The spiral blade of PFNA is hammered into the femoral neck of osteoporotic patients, which allows for good bone filling and compression, resulting in good anchorage, less bone removal and resistance to rotational and axial forces compared to the screw system. In contrast, the threads of PFN are easily damaged when screwing in the screw, and therefore the anchorage of the screw to the bone is poor. (iii) In patients with a small femoral neck, the design of the PFN with 2 proximal locking nails limits its use to a certain extent.
External fixator fixation
External fixation frame is an intermediate fixation method between surgery and non-open surgery for femoral intertrochanteric fractures. Most of the patients with intertrochanteric fractures are elderly and have more medical diseases. For patients with poor surgical tolerance and high surgical risk, the surgical injury is greater.
The external fixation brace has the following advantages: ① less trauma: no surgical incision, less blood loss, almost no damage to the local blood flow of the fracture; ② reliable fixation, the external fixation brace is stable and reliable, in line with the biomechanical requirements; ③ short operation time; ④ early activity, postoperative quadriceps contraction functional exercise, early sitting up to perform functional exercise in bed, reducing the complications caused by bed rest such as pulmonary infection, lower limb thrombosis (5) Removal of the external fixation brace after fracture healing is simple and does not require secondary surgery.
To a certain extent, external fixation brace treatment is more suitable for elderly patients with poor general condition. Although the requirements for fracture repositioning are not particularly high in elderly patients, the repositioning effect of the fracture, especially of the lesser trochanter, is the key to the stability of the fracture after surgery.
REFERENCES
1 Parker MJ, Handoll HH. Gamma and other cephalocondylic intramedullary nails versus extramedullary implants for extracapsular hip fractures in adults. Cochrane Database Syst Rev. 2010 Sep 8;(9):CD000093.
2 Haidukewych GJ. Intertrochanteric fractures: ten tips to improve results. Instr Course Lect. 2010;59:503-9.
3 Butler M, Forte M, Kane RL, et al. Treatment of common hip fractures. Evid Rep Technol Assess (Full Rep). 2009 Aug;(184):1-85.
[1] Authors: Liu Limin, Department of Orthopaedics, Xuanwu Hospital, Capital Medical University 100050 E-mail: liulimin@medmail. com