The bone cement used in knee replacement and other types of surgery has been associated with numerous intraoperative and post-operative complications, including a condition known as bone cement implantation syndrome (BCIS) and aseptic loosening.
The latter term refers to the failure of the prosthesis when there is no bacterial infection present. Aseptic loosening caused by bone cement appears to be associated with the use of high viscosity cement, or HVC. While this can save time during the actual operation, the long-term consequences for the patient can be catastrophic.
About Bone Cement
Made from polymethymethacrylate (more commonly known as acrylic, used for Plexiglas), bone cement is an adhesive used to fix the prosthesis to the bone surface. This product is available in high, medium and low viscosity; research indicates that high viscosity cement (HVC) provides less adhesion power than thinner formulations.
Surgeons prefer HVC because it sets up in a shorter amount of time. However, this shorter working period provides less time for the cement to create a firm bond. It may also make it more difficult for the surgeon to work the adhesive into the various grooves and cracks in the bone. This is especially problematic if air bubbles entered the adhesive while it was being mixed.
There is a “cementless” type of total knee arthroplasty available, but the recovery period is longer, as it requires time for new bone tissue to grow and integrate with the prosthesis.
Symptoms of Aseptic Loosening
The signs of aseptic loosening of the prosthesis are similar to those caused by a bacterial infection. These include:
- chronic pain at the surgical site
- swelling and inflammation
- decreased mobility, stiffness, and loss of range of motion
- low fever and generalized fatigue
The onset of symptoms may be days, weeks or months following the surgery.
While aseptic loosening can present many of the same symptoms as an infection-related loosening, the latter can be readily treated with antibiotic medications and irrigation of the surgical site. The consequences of aseptic loosening due to failure of the cement bond are more serious, however.
Because the chemical used to manufacture the cement is able to enter the blood vessels and surrounding tissues, the patient may show signs of toxicity, which include:
- hypoxia (lack of oxygen)
- hypotension (low blood pressure)
- irregular heartbeat
- blood clotting
These symptoms can result in stroke, cardiac arrest, loss of consciousness and may even be fatal.
Manufacturers of Bone Cement
Bone cement products currently available on the market are:
- CMW 1 and 2 (DePuy)
- Simplex HV (Howmedica)
- DJO Surgical Cobalt G-HV (Biomet)
- Palacos R (Zimmer)