Can I have an MRI after hip replacement surgery? Don’t worry!

Author: Guo Donghong, attending physician, Nanfang Hospital, Southern Medical University

Reviewer: Wang Jian, Chief Physician, Nanfang Hospital, Southern Medical University

Artificial hip replacement is a common orthopedic surgery that improves the quality of life for many patients. However, postoperative rehabilitation and related precautions are crucial, among which prevention of artificial hip dislocation is an issue that both patients and medical staff need to pay close attention to.

At the same time, with the continuous development of medical technology, MRI examinations play an important role in disease diagnosis. However, for patients who have undergone artificial hip replacement, they may have doubts: Can they still undergo MRI examinations after this operation? This is not only related to the accurate diagnosis of subsequent diseases, but also affects the patient's treatment plan and confidence in recovery.

1. How to prevent artificial hip dislocation after surgery?

In the early stage after artificial hip replacement, the hip joint is still in a relatively unstable state, which can cause dislocation of the joint prosthesis, and dislocation is the most common later. Therefore, after artificial hip replacement, patients should try to avoid excessive flexion, adduction, and internal rotation of the hip joint. The measures to prevent artificial hip dislocation are as follows.

Sitting position: The height of the chair should be higher than the knee joint, ensuring that the hip joint is in a relatively straight position, and the knee joint should be kept lower than or equal to the height of the hip. When the patient sits down, try to keep the toes slightly outward, do not cross your legs, and do not sit cross-legged. The sitting time should not be too long within 3 months after surgery to avoid lower limb edema.

Lying position: Place a pillow between the legs to keep the joints in the proper position. When turning over, keep the body and legs in a straight line at the same time. When lying on the healthy side, place a thick pillow between the legs to avoid crossing the legs. After the wound has healed and the pain has eased, you can lie on the affected side.

Toilet: It is not recommended to use a squat toilet. You can use a sitting toilet instead. Be careful to keep the hip joint not lower than the knee. Install handrails near the toilet to assist the patient in sitting down and standing up.

Picking up objects: Do not bend over to pick up objects on the ground within 6 weeks after surgery, and do not turn around suddenly or reach out to pick up objects behind you.

Riding: When getting on the bus, sit down with your buttocks first; when sitting, sit with your buttocks forward, lean your body back, and stretch your legs forward as much as possible.

Figure 1 Copyright image, no permission to reprint

Does it mean that I cannot have an MRI after having a hip replacement?

This is one of the problems that bothers patients with femoral head necrosis. A patient's family member once asked me that her mother had undergone artificial hip replacement and was recently suspected of having a stroke, and needed a head MRI to confirm the diagnosis. After hip replacement, if there is metal in the body, can an MRI examination still be performed? Generally speaking, an MRI examination can be performed after artificial hip replacement.

Figure 2 Copyright image, no permission to reprint

The strong magnetic field of MRI can attract iron-containing substances (called ferromagnetism), causing them to shift suddenly. However, today's artificial joint prosthesis materials are generally low-magnetic materials, which do not affect MRI examinations.

The artificial hip joint is composed of 4 parts: acetabular cup, acetabular liner, artificial femoral head and femoral stem. Among them, the materials of acetabular cup and femoral stem are mainly titanium alloy or tantalum metal. These two metals are low-magnetic metals and will not be affected by the magnetic field in the MRI machine, so they will not be sucked by the machine. There are 3 kinds of materials for artificial femoral head: ① ceramic; ② cobalt-chromium or cobalt-chromium-molybdenum alloy; ③ zirconium-niobium alloy. They are all non-ferromagnetic materials.

There are two types of materials for the acetabulum lining, one is ceramic and the other is polyethylene, which is plastic. Both of these are not metal and will not be affected by magnetic fields. Therefore, the four components of the artificial hip joint, whether they are metal or not, will not be significantly affected by the MRI machine, so it is safe for patients to undergo MRI examinations after surgery.

However, one thing needs to be reminded that some patients' artificial hip joints use steel wires, screws and other materials that may be ferromagnetic, so they cannot undergo MRI examinations.

Therefore, whether you can do an MRI examination after hip replacement surgery must be confirmed with your attending physician.