Breaking your hip with a protheses: a new medical problem investigated
Maud Vesseur, an orthopaedic surgeon in training, encountered a striking issue at Zuyderland Hospital: increasingly, patients with hip prostheses were being admitted after a fall, having fractured their hip. Often this happens precisely around the stem of their prosthesis. Vesseur recently defended her PhD thesis at the Faculty of Science and Engineering.
During the initial surgery for a worn or broken hip, a metal prosthesis is usually inserted into the femur, secured with a long pin. Sometimes, the space between the pin and the bone is filled with cement; sometimes, it isn’t. In the event of a fall the bone can break. “Our research shows that the risk of a fracture is lower if the prosthesis is secured with cement,” explains Vesseur. “But if they do break, the cement makes the repair surgery significantly more difficult.”
In addition to the absence of cement, Vesseur identified other risk factors that can lead up to fracturing the femur: female sex, older age, limited mobility, overweight, and poor overall health.
Major surgery
The repair surgery is technically complex. Bone fragments must be reattached as securely as possible around the, preferably existing, prosthesis. “We often use a metal plate, which we attach to the outside of the bone with metal wires because screws into the prosthesis aren’t an option,” Vesseur explains. “The surgery usually results in a large wound, sometimes running the entire length of the thigh.”
For patients who are already frail, such a procedure is an enormous strain. It’s perhaps not surprising that 17% of them die within a year of the operation. “Yet we still operate them, because realigning the bone is the best way to relieve pain. Fortunately, new pain management methods are emerging, such as permanent nerve blocks. In some cases, patients feel no pain in the leg at all. That raises the question: should we really put people at very high risk of death through such a major surgical procedure?”
Who is at high risk?
Vesseur also investigated which patients are most likely to die within 12 months of the surgery. The main factors she identified were residing in a care home at the time of the fracture, reliance on walking aids, and weight. “Interestingly, higher weight is a risk factor for younger patients, while for the very elderly, it’s actually low weight that’s the problem.” Additionally, this group often already has one or more chronic conditions, which further reduces their chances of recovery.
Not a robot but an aid
Based on all the risk factors, Vesseur developed a model that predicts the likelihood of death within six months after the reconstructive surgery. “Suppose someone has a 90% chance of dying within half a year. The model doesn’t just say, like a robot, ‘Don’t operate!’ It’s primarily a tool to facilitate the conversation with the patient and the family. You can explain that the risk is extremely high and give the patient a choice: pain management and palliative care only or proceed with the surgery.”
As a medical doctor, Vesseur was somewhat of an outsider among the PhD candidates at the Faculty of Science and Engineering. “I did stay in touch with the faculty, mainly through my supervisor Lee Bouwman, and I participated in the training sessions for PhD candidates,” she says. Now that she has earned her PhD, she is focusing first on completing her surgical training. But she wants to continue researching: “Ultimately, I hope to pick up the thread again, but in a coordinating role, perhaps as a mentor for new PhD candidates.”
Text: Patrick Marx
