Intramedullary nail introduction

Fractures caused by trauma are the most common, with high force and short action time, causing more serious damage to the body. In open reduction fracture surgery, the selection of one-time implants is often the key to surgery. Its main function is to maintain the reduction state of the fracture end, control the length, axis and rotation of the backbone, so as to provide good stability and achieve the purpose of enabling patients to move early and heal. After the fracture heals, the implant is taken out and the hospital handles it properly. At present, the most commonly used one-time implants for fracture treatment include bone plates and intramedullary nails. Let's briefly introduce intramedullary nails:

Intramedullary nailing is the preferred internal fixation for femoral shaft fractures and tibial shaft fractures.

Intramedullary nails are generally suitable for the treatment of the following fractures:

Diaphyseal fracture of tubular bone

· Nonunion after long bone shaft fracture

· Long bone shaft fracture malunion

Bone lengthening/shortening of long bones

·Pathological fracture of the middle part of long bone

·Joint fusion

Articular end fractures in special parts of long bones (femoral neck, intertrochanteric, femoral condyle, etc.)

Introduction of several commonly used intramedullary nails

1. Gamma intramedullary nail

Gamma nails are indicated for all types of fractures from the base of the femoral neck to above the level of the lesser trochanter. Gamma nail internal fixation has no absolute contraindications except infection, and patients with severe osteoporosis need to be restricted in their early postoperative activities.

2. Interlocking intramedullary nail of humerus

The interlocking intramedullary nail of the humerus can be inserted antegradely or retrogradely. Antegrade can fix all kinds of closed fractures and open fractures below the second degree from the fracture line more than 4-5cm above the humeral condyle and 2-3cm away from the greater tuberosity of the humerus.

The antegrade nailing method is a relatively mature internal fixation technique at present. Shoulder pain and shoulder joint dysfunction are the main complications of antegrade nailing. Most scholars believe that the degree of rotator cuff injury is related to the incidence and degree of postoperative shoulder pain. The main reasons include:

①During the operation, the rotator cuff and surrounding tissues are damaged. In the operation of antegrade nailing, the nailing site is usually selected on the medial side of the apex of the greater tuberosity of the humerus, and an incision needs to be made at the rotator cuff, which will inevitably damage the tendon and acromial subsidence membranous vesicle.

②The tail end of the intramedullary nail was not completely buried under the bone surface, and the tail of the nail hit the rotator cuff during shoulder joint movement. In the case of greater tuberosity fractures, in order to prevent excessive separation of the fracture fragments, the intramedullary nail cannot be completely buried under the bone surface, so that the rotator cuff cannot be repaired.

The application of subacromial anterior incision can reduce the incidence of postoperative shoulder complications. Embedding the nail tail cap 3~5mm under the cartilage to avoid the friction of the nail tail on the acromion is also one of the measures to prevent shoulder pain.

Retrograde nailing itself has two advantages:

①The local anatomy of the posterior approach is simple, there are no important blood vessels and nerves, and it is not easy to cause side injuries caused by surgical operations;

②All operations are performed outside the joint, without affecting the rotator cuff or subacromial space, and causing no damage to the elbow and shoulder joints.

When the nail is inserted retrogradely, the stress on the edge of the bone cortex at the entry point increases, and improper operation may cause severe complications such as splitting of the cortex at the entry point, perforation of the contralateral cortex, and supracondylar fracture.

3. Tibial intramedullary nailing

Intramedullary nailing can be used for the following injuries:

Closed fractures from high-energy injuries;

Knee injuries with floating knees;

Multiple injuries: with pelvic, acetabular, and spinal fractures;

With ipsilateral or contralateral femoral shaft fracture;

·With osteofascial compartment syndrome, fasciotomy is required, and then intramedullary nailing is required;

Fractures of the tibia and fibula at the same level;

·Open tibial fractures (Gustilo I, II, IIIa, IIIb)

· Low-energy injuries that cannot be controlled by non-surgical treatment.

For open fractures, even if the trauma lasts for 12 hours, intramedullary nailing can also be applied on the premise of thorough debridement and reasonable application of antibiotics.

The surgical indications for tibial intramedullary nailing can be summarized as follows:

Closed or less severe open tibial shaft fractures with adequate soft tissue coverage;

· Aseptic pseudoarthrosis compression fusion;

Bone graft fusion after fracture nonunion;

·The fixation after diaphyseal lengthening, shortening and rotational osteotomy;

· Fixation of bone defects after diaphyseal tumor resection;

· Pathological fractures of the diaphysis.

In closed fractures, the following conditions are suitable for intramedullary nailing:

·With femur fracture and floating knee syndrome;

With knee ligament injury, the stability of the tibia needs to be reconstructed;

·Accompanied by foot and ankle fractures;

Unstable tibial fractures that cannot be reduced satisfactorily;

·For the convenience of nursing care and early mobilization for tibial fractures in multiple traumas.

In fracture shortening, intramedullary nailing should be used when the fracture shortens more than 1 cm, the varus and varus are greater than 10°, and the rotation exceeds 10°, which cannot be controlled by non-surgical methods.

4. Proximal femoral nailing

The proximal femoral nail system (proximal femoral nail system, PFN) is an intramedullary fixation material for the treatment of proximal femoral fractures developed by the AO Internal Fixation Society based on the improved design of the Gamma nail principle. PFN is suitable for fractures from the base of the femoral neck to 5 cm below the lesser trochanter, that is, all fractures of 31-A in the AO classification and fractures of the femoral shaft at the high trochanter.

Its structural features and advantages:

①The length of the main nail is 240mm, the diameter of the proximal end is 17mm, and the diameter of the distal end is 10, 11, and 12 to choose from; the neck-shaft angle is designed to be 130°, and the valgus angle is 6°

②The screws in the femoral head and neck consist of two pieces, the lower one is the main lag screw with a diameter of 11mm, and the upper one is an anti-rotation screw with a diameter of 6.5mm. The design of the anti-rotation screw can more effectively prevent the rotation of the broken end of the fracture.

③The groove design of the distal end of the main nail is flexible, and the distance between the distal locking nail hole and the nail tip is longer, which minimizes stress concentration and reduces the risk of femoral shaft fracture at the end of the main nail.

④ The distal end of the main nail provides two locking nail holes, static and dynamic.

Features of intramedullary nails

advantage:

1. The intramedullary nail can control the axial line of force at the fracture site; the interlocking intramedullary nail has a better effect on preventing fracture rotation and reduces the risk of intramedullary nail fracture.

2. The closed nail penetration technique is adopted, less soft tissue stripping is required, the fracture site can not be exposed, and the infection rate of the operation is reduced.

3. The fracture hematoma is retained by the closed nailing, which reduces the damage to the periosteal blood supply. At the same time, the debris generated during reaming is deposited on the fracture site, which has the effect of autologous bone grafting.

4. In general, the intramedullary nail does not need to be removed. Even if it needs to be removed, only a small incision should be made at the corresponding place of the locking nail and one end of the intramedullary nail.

5. The intramedullary nail and the damaged bone have a stress dispersion effect to avoid stress shielding.

limitation:

1. The size of the bone marrow cavity limits the diameter of the intramedullary nail, thereby limiting the bending strength of the intramedullary nail. In order to achieve the purpose of increasing the bending strength of the intramedullary nail, the method of reaming is sometimes used, but the reaming destroys the blood supply of the endosteum.

2. Intramedullary nails (especially non-locking intramedullary nails) are not as good as plates or external fixation in controlling the rotation of the fracture.

3. Reaming can destroy the blood supply of the endosteum and affect the medial cortical bone.

4. Marrow reaming causes bone marrow components to enter the blood, which can cause fat embolism.

In order to overcome the above shortcomings, various types of intramedullary nails have been designed. Different types of intramedullary nails have different indications and contraindications. Before using them, you must have a full understanding of them in order to use intramedullary nailing correctly.

The specific intramedullary nail application can be used after comprehensive consideration according to the patient's condition.