The implants used in total joint replacement procedures can be held in place with cement. Some surgeons routinely use cement to implant new hip joints. Holes are drilled in the acetabulum, the pelvic socket that receives the cup portion of the new hip joint. A special tool called a pressurizer is used to settle the cup in place. The force from the pressurizer can cause the cement to ooze out around the edges of the cup. This is called cement extrusion (CE).
Most of the time, patients have no symptoms from CE. However, in some patients, a small amount of cement in the wrong place can cause problems. Irritation of a nerve can cause burning. Nearby blood vessels are also at risk of being damaged. No one has studied how much CE is too much, or how often CE causes problems in people receiving a cemented hip implant.
The goal of this study was to find a way to measure how much and how far the cement travels beyond the edges of the implant. X-rays can be used to show large amounts of CE and are less costly than MRI (magnetic resonance imaging) scans. Only one patient in the study had poor X-rays and had to be left out. Almost half of the remaining patients (for a total of 111 hips) showed CE on X-rays. No one needed treatment for symptoms from the CE.
The authors of this study conclude that CE is common. No one knows yet how many patients with CE will have problems. Studies have not yet shown how much cement can squeeze out before symptoms occur. This new method of measuring CE will help researchers answer these questions in the future.