Nitinol grasping bone plates are three types of medical devices that are implanted in the human body and placed in the body for a long time. The safety of their products is very important, so risk management of nitinol products is particularly important. Through the requirements and regulations of YY / T0316-2008 and ISO14971-2007, the risk management of the nickel-titanium grasping bone plate is carried out. Identify product risk points and control them. Ensure that the risks in the future production, sales and use are minimized.
As a kind of shape memory alloy, nickel-titanium alloy has an expansion rate of more than 20%, a fatigue life of 1 × 107, damping characteristics 10 times higher than ordinary springs, and its corrosion resistance is better than the best medical stainless steel at present. Therefore, it can meet the needs of various engineering and medical applications and is an excellent functional material. In addition to its unique shape memory function, memory alloys also have excellent characteristics such as wear resistance, corrosion resistance, high damping and super elasticity. And it can also meet the requirements of chemistry and biology, that is, good biocompatibility. Nitinol can form a stable passivation film with organisms. Therefore, nickel-titanium alloys have been developed into many medical device products. Most of the medical device products that have been developed and put into the market today are more than two or three types of medical devices, some of which are implanted in the human body, and are placed in the body for comparison. Long, so risk management of nickel-titanium alloy products is particularly important. The risk management of its products will be conducted in accordance with the requirements of medical device risk management standards and procedures.
I. Judgment on the intended use and safety-related characteristics of NiTi alloy grasping bone plate
Intended use: Mainly used for internal fixation of fractures in patients with bone injuries, to help patients with early healing and functional exercise. Nitinol grasping bone plate is a new type of internal fixation instrument for tubular bone fractures of extremities. It uses the shape memory effect of nickel-titanium alloy to achieve circumferential embracing fixation mode of tubular bones of extremities. Its advantage is that it is convenient for surgical operation , Simple; fixed holding firm and reliable, in line with AO and BO fixation theory; the material has good biocompatibility and is an ideal internal fixation implant material. The product is provided to the user in a non-sterile state. The hospital doctor sterilizes the tissue before the operation, and stretches each arm around the ice under salt water to make it larger than the outer diameter of the bone, which is easy to be stuck in the fracture. Heating with warm saline promotes resetting the arms around the arms. This product is a one-time use, which can effectively avoid cross-infection between patients.
2. Judgment of visible or potential hazards
After preliminary analysis, the determination of the related potential hazards is as follows:
- (1) Damage to the patient: bacteria, causing pyrogen reaction or infection, and death in severe cases. Improper model selection results in unreliable fixation and secondary fractures. After being inserted into the human body, it is repeatedly adjusted, resulting in the loss of product function. The micro-crack defects present in the finished product cause crack propagation and failure after the patient is loaded. The doctor did not follow the steps to force the deformation, resulting in incomplete shape recovery and failure. The patient did not follow the doctor’s instructions for post-operative training and was prematurely weight-bearing, which caused fatigue and fracture of the device and caused bone deformity to heal. Due to the thin material wall of the device or insufficient material strength, the patient’s end function is restored to cause fatigue and deformation of the device, causing bone deformity healing or false healing. The inaccurate setting of the functional temperature of the instrument causes premature shape recovery or slow shape recovery, causing delays in surgery.
- (2) Damage to the user: the tines are too sharp, puncturing the patient’s tissue or the operator’s hand. Insufficient supporting equipment for removing the instruments, resulting in cumbersome secondary removal. The device has no memory function and cannot be used normally. The memory function of the device has been artificially damaged and cannot be used normally. Hazards related to use lead to incorrect use.
3. Risk assessment
The degree of damage of the bone plate can be defined as four levels.
Determination of the potential cause of each damage: When the doctor is in normal operation, there must be continuous contact between tools and instruments to facilitate adjustment and reset. There may be scratches on the metal surface, which does not affect normal use. The device is a structure of the arm around the arm, with sharp claws added to the arm around the claws for easy access to the surface of the bone. During production and processing, there is a claw tip that affects the individual length, but does not affect use. Improper selection of specifications may cause unstable fixation or shedding, causing incomplete healing and deformed healing. This problem can be solved by using the instruction manual and training explanation. Such problems are inevitable in metal materials, but the incidence is extremely low. There is no statistical data to check, and ultrasonic secondary flaw detection can be used to reduce this risk to an acceptable level.
Occurrence probability grading criteria can be judged according to qualitative (semi-qualitative) classification and are divided into the following six levels.
4, take risk control measures
The measures that must be taken to reduce the risk are: the material supplier’s previous qualification verification. Raw material ex-factory certificate and quality warranty. Inspection report and third-party verification report. Surface identification of the board. Double-sided flaw detection is carried out on each board in storage, and the coverage rate is 100%. Repeat the flaw detection of the sheet in question, and mark the defect with a red pen and record it. In the process of production and processing, control and label transplantation are carried out according to the operation instructions for traceability. During the brightening process, use a 5x magnifying glass to check one by one to prevent defective products from flowing into the subsequent process. In the product packaging or instruction manual, the product use process is explained step by step and reminded with warning words. The sales staff should make repeated explanations and essential guidance before the operation, and invite experienced doctors to be the chief surgeons; for inexperienced physicians, it is best to arrange on-site lectures and demonstrations by the company’s instructing physicians. Before the operation, the X-ray film should be measured with a steel ruler, and the error should be taken into account. A bone plate with a size one smaller than the bone is selected for the first use, and at the same time, another bone plate with the same bone size is prepared as a spare, and two pieces are sterilized at the same time. After the surgical incision, use a caliper to measure the damaged bone. If it is the same size as the X-ray film, the smaller bone plate is used; if the measurement is larger than the X-ray film, the larger bone plate is selected. Put the two bone plates in the prepared ice brine, the temperature must be <5 ℃. According to the actual measurement results, select a smaller bone plate and use an instrument to expand it to the specified size (larger than the outer edge of the damaged bone) in ice salt. And the amount of deformation cannot be greater than 8%. The operating doctor uses clamping forceps to clamp the bone plate and quickly moves to the affected bone for placement and positioning. After adjusting and resetting, use hot warm saline or gauze at about 40 ℃ to apply heat to the bone plate. The bone plate is affected by temperature, which produces memory recovery, and it can hug the fractured bone. If it is found that the partially damaged bone is not in the clamping arm of the bone plate or the overall fixation is not perfect, the bone plate can be cooled again, and then each arm is opened with pliers to adjust an angle. During the installation process, the doctor was instructed to avoid brutal operation and forced deformation during operation.
Through the operation of each link and details above, the risk level can be controlled and reduced. Compared with other similar operations, the risk is smaller. From the acceptable point of view, its advantages and benefits are much higher than the risk, which is acceptable. .
5. Risk management report
Analyze the potential risks from the whole, which can be prevented during the product processing process, and no new risks will be generated after taking measures. Therefore, the above risks are acceptable to patients, clinical use is safe and reliable, and users can use it with confidence.