screw fixation

The screw achieves the purpose of fixing the fracture by the close engagement of the thread with the bone. If properly applied, some fractures can better maintain the role of reduction and internal fixation. The incision of this type of surgery is small, and the peeling of the periosteum is limited, so that it has the advantages of small damage to soft tissues and bone tissues, small foreign matter, and simple operation. However, its fixation strength is limited. In osteoporotic fractures, the fixation effect is poor. If it is fixed with ordinary screws, it must be adequately fixed until the fracture is healed. Treatment of diseases: fracture of the tibia and fibula Indication 1. rupture fractures of tendon, tendon, trochanter or nodule (such as femoral, humeral and external malleolus fractures, ankle fractures, ulnar olecranon fractures, humeral nodular fractures, tibial tuberosity fractures, etc.) It is the one who is involved in the articular surface. These fractures have small bone fragments, large muscle traction, easy displacement, and external fixation is difficult to maintain the purpose of resetting, and screw fixation is most suitable. 2. Long bone spiral fracture, long oblique fracture, and butterfly fracture failed by manual reduction. 3. Femoral neck base fracture, fixed with compression cancellous bone screw and washer, can play a dual role of fixation and compression. Contraindications Older, combined with severe heart, liver, kidney and other diseases and difficult to tolerate surgery. Preoperative preparation 1. Selection of screws: Before the operation, the appropriate length and shortness of the screws should be selected according to the x-ray film. The number of preparations should be more appropriate for selection. The thread of the screw should be sharp, the depth should not be too shallow, the pitch should not be too dense, and the groove of the screw should be complete. Commonly used screws in the clinic are two types of machine screws and ao screws. Compression screws are further divided into cortical bone screws and cancellous bone screws. The cortical bone screw is a full-length thread and is also used for the fixation of the pressure plate. The cancellous bone screw has a wide thread and only 1/3 to 1/2 of the length of the screw, and both have no self-tapping grooves. 2. Choice of drill bit: The drill bit is preferably made of stainless steel. Although it is sharp without tool steel, it is not easy to break. The diameter should be slightly smaller than the screw, generally the same as the diameter of the base of the thread (ie the bottom diameter of the thread). The diameter of the drill bit for the long bone end and the cancellous bone should be smaller, and the screw can firmly bite the bone and fully exert the fixation effect. Pressurized cortical bone screws only have a pressurizing effect when their threads are fixed to the contralateral cortical bone. Therefore, drill the sliding hole (drilling near the screw head), the diameter of the drill should be equal to the diameter of the thread, and the drill hole of the drilled hole (the hole of the contralateral cortical bone) should be smaller than the diameter of the thread. 3. Rotary chisel (screwdriver, screwdriver) requirements: Rotary chisel is divided into three types: ordinary straight, cross and hexagon, the latter two are used for compression screws. The width and thickness of the chisel head must be compatible with the screw groove of the screw (the width preferably exceeds the length of the groove), and the chisel head should be in close contact with the bottom of the groove. If a rotary chisel that does not meet the requirements is used, the screw groove is easily damaged during the screwing process. It is best to use a sleeve type rotary chisel that can fix the screw, and it can advance and retreat stably and quickly without damaging the groove of the screw head. 4. The tap is not automatically screwed out of the groove of the threaded passage at the end of the compression screw. Therefore, the sharp coring screw with a cutting edge must be used to drill the cortical bone and tap the thread. The diameter should match the diameter of the thread. Surgical procedure 1. Keep reset: open reduction, fracture reduction must be maintained stably during the whole process of internal fixation, so as to avoid displacement, otherwise it is necessary to reset the drill hole and increase the damage. Different parts of the fracture need to be replaced by different instruments: the long bones need to be held by the rongeur; the bone protrusions, tendons and ankles can be held by the towel clamp. 2. Protect the surrounding soft tissue: When drilling, the surrounding soft tissue should be pulled apart, and the nerves and blood vessels should be carefully opened to protect them from being damaged by being wound onto the drill bit during the drilling process. Once involved, it is necessary to stop the drill in time, then slowly reverse the drill bit and carefully loosen the tissue that is involved. 3. Drilling: Drill with a suitable size by hand (or electric drill, pneumatic drill), drill in the predetermined direction (generally perpendicular to the fracture line or cortical bone). Start with a small dent and then drill slowly and steadily under constant light pressure. Do not use too much force, so as not to slip the bit and damage the surrounding tissue, especially when drilling on the cortical bone, it is easy to slip, especially pay attention. The backbone of the long tube should be drilled through two layers of cortical bone. When it is about to drill through, there is a feeling of bun. When the contralateral cortical bone has this feeling, it is necessary to control the pressure to avoid drilling into the soft tissue and causing damage. After the drilling is completed, the depth of the bone hole is measured, and the appropriate length of the screw is selected accordingly. In cancellous bone, the drilling depth should be slightly shorter than the length of the screw, and only the cortical bone can be drilled for osteoporosis. When pulling out the drill bit, slowly reverse it and withdraw it. It is not appropriate to swing it hard to avoid the drill bit breaking in the bone. If a cortical bone compression screw is used, the proximal cortical bone should be drilled with a drill bit (4.5 mm) with a screw thread diameter, and then drilled with a drill bit (3.2 mm) that is slightly thicker than the screw stud. The threaded hole of the cortical bone is then unscrewed by the tap (4.5mm). 4. Screw in the screw: Select the screw with the appropriate length and slowly screw it in the direction of the drilling to avoid shaking, so as to avoid the hole or the thread damage and affect the fixing effect. To enhance fixation, the screw must pass through two layers of cortical bone (the tip of the nail just exposes the surface of the contralateral cortical bone), and finally tighten the screw to bring the fracture surface into close contact. If a compression screw is used, when the cortical screw enters the distal threaded hole, the more the screw is tightened, the more pressure is applied to the fracture end. After the cancellous bone compression screw tail and the washer are screwed in, the embossed and unlined parts of the nail must be fixed in the proximal and distal fracture segments respectively, and the screw is tightened to produce a pressurizing effect. 5. Stitching: After the internal fixation is completed, the device that maintains the reset is removed, and the fracture end is checked. If there are conditions, some fractures involving the articular surface should be examined by film. After satisfactory, they can be sutured by layer. complication 1, infection. 2, osteomyelitis.