Total Joint Replacement: Metal, Plastic and Ceramic Hips and Knees?

Total joint replacements are performed for severe degenerative disease of the hip, knee, ankle, shoulder and even wrist, fingers and spinal segments. The two most common procedures are total hip and knee replacements and this it where we’ll start today.

Each year, over 62,000 hip and knee joint replacement surgeries are performed across Canada. The number of these surgeries performed actually doubled over the ten year period prior to 2007 as governments and hospital systems recognized the health and wellness benefits of providing patients with the ability to keep moving into their elder years. With the “move it or lose” philosophy finally encouraged by funding bodies, programs to shorten wait times and increase access to total hip and knee replacement surgeries were launched Canada wide.knee_gsf_nexgen_glass2_200px

Hip and knee joint replacement requires removal of the degenerative joint surfaces and resurfacing with a prosthetic implant or implants. For knees, the ends of the femur (thigh) bone and the tibia (leg) bone are shaved or cut and replaced with a metal component that articulates against a space age plastic insert. The components may be cemented in place in most cases or made of a porous material that allows bone to grow into the pores to bond metal to bone over time. Although the plastic is extremely durable, it may wear away over years and require revision with a new insert. The metal components may loosen over the years and also require revision. Total knee replacements can last up to 20 or more years in many patients.

hip_mltaper_kinectiv_continuum_glass_200Hip replacements require arthroplasty of the ball and socket joint which connects the thigh (femur) bone to the pelvic cup (acetabulum). We typically remove the ball, or head of the femur bone, and replace it with a metal or ceramic ball that inserts into the marrow canal of the femur with a metal stem. The acetabulum, or socket part of the joint, is resurfaced with a metal shell typically and a plastic, ceramic or metal liner that articulates with the ball portion of the implant. Some hip replacements will last over 30 years in patients. Revision takes place for loosening, wear of the liner, instability or failure of the integrity of the prosthetic components or the bone around the components. Total hips and knees can also fail for other reasons including infection.

A patient undergoing hip or knee replacement will stay in the hospital anywhere between 2 and 5 days and start physical therapy and rehabilitation while there. Pain management and the prevention of blood clots in the legs are two of the most important post operative issues that the medical team will address. Medications are given for pain either by intravenous injections or by mouth. The use of pain patches, epidural anesthesia or spinal anesthesia has improved post operative pain management for total joint patients. Patient controlled pain pumps are also commonly used in most

The field of joint replacement is huge with billions of dollars worldwide directed at research and development of more durable, longer-lasting and better functioning prosthesis. Alternate bearing surfaces such as ceramics, and highly cross linked plastics with antioxidants to prevent degradation are currently the hottest topics in joint replacement research.

The Canadian Joint Replacement Registry (CJRR) was launched in 2000 to create a database of patients and implants used for arthroplasty procedures in order to offer insights into successes, failures, trends and complications that surgeons and patients experience. We can also see some interesting statistics about who is undergoing these procedures, in what regions, and by whom.

For example, the CJRR tells us that compared to men, Canadian females have higher age-adjusted rates per 105 for both total knee replacements and total hip replacements. Accordingly, women account for 57% of patients receiving total hips and 61% of patients receiving total knees. Using CJRR data, a strong relationship between obesity and subsequent risk of undergoing both hip and knee replacements was found.  The largest increases in both total hip and knee surgery rates occurred in the 45–65-year age groups, where the greatest increases in Canadian obesity rates have also occurred.

The CJRR also highlights some of the differences in hip and knee replacement surgeries across the globe. In Sweden, the incidence of total knee replacements in females for 2006–2007 was 136 per 105, and in Canada it was 182 per 105. Although the reasons for these differences may have many factors, it is likely that the higher rates of total knee replacement in Canada may be related to a higher levels\ of obesity among Canadians.

By adding revision surgery information to the database, we should eventually be able to develop survivorship information for specific implant types, the addition of antibiotic to cement, to surgical approach, and many others factors that are involved in procedure, implant selection and post operative care.

For more information about the CJRR please visit the website.

And for more information about total joint replacements, please visit one of zimmerthe largest manufacturers of prosthetic joint products, Zimmer.

Disclosure: the author has not received any remuneration for this blog from Zimmer. Zimmer is currently the author’s affiliate hospital’s primary hip and knee arthroplasty vendor.