Hip replacements are among the most common orthopedic procedures. When a hip replacement is performed, the arthritic, damaged hip joint is removed. The ball-and-socket hip joint is then replaced with an artificial implant. The materials used in the implant depend on several factors, including the age of the patient, the activity level of the patient, and the surgeon’s preference.
Below are brief descriptions of some of the most commonly used hip replacement implants. Not all implants are options for all patients. These are general statements about the different implants; if you have specific questions about a particular implant you must discuss this with your doctor!
TYPE OF FIXATION
Cemented had traditionally been used but in the 1980’s a uncemented design was developed. The cementless design is a porous implant. The intent is, through biologic fixation, that bone grows into and through the pores in the implant, thereby securing it.
The cementless joint replacements are expected to reduce the chance of infection and loosening of the prosthesis, which are the two major complications of hip replacement surgery. However, indicates that both the cemented and cement less joints do very well.
Patients having hip replacement surgery experience significant pain relief and improved range of motion
Cemented prosthesis: –
in this process the prosthesis is fixed to the bone with the help of special bone cement. In that variety only available in head having 2 types metal & ceramic head.
The design of uncemented prosthesis is a porous implant. The intent is,
through biologic fixation, that bone grows into and through the pores in the implant./p>
Advantage in uncemented fixation is that bone loss will not occur despite loosening, in contrast to the dramatic osteolysis seen in loose cemented implants. A much lower rate of thromboembolism has been shown in uncemented THR.
Type of bearing surfaces in total hip replacement prosthesis:
1). Metal on poly implant:
The metal and plastic implants are the most commonly used hip replacement implants. Both the ball and the socket of the hip joint are replaced with a metal prosthesis, and a plastic spacer is placed in between.
The metals used include titanium, stainless steel, and cobalt chrome. The plastic is called polyethylene. The implant is secured to the bone by one of two methods; it is either press-fit or cemented into place. In the press-fit method, the implant is fit snuggly into the bone, and new bone forms around the implant to secure it in position. When an implant is cemented, special bone cement is used to secure the prosthesis in position.
2). Metal on metal implant:
Metal-on-metal implants use similar materials, but there is no plastic piece inserted between. They are now being withdrawn from the market because of high rate f metallosise related complication.
3). Ceramic on poly implant
The ceramic and poly implant in that the ball of the hip joint are replaced with a ceramic prosthesis, and a plastic spacer is placed in between.
4). Ceramic on ceramic implant:
Ceramic-on-ceramic implants are designed to be the most resistant to wear of all available hip replacement implants. They wear even less than the metal-on-metal implants. Ceramics are more scratch resistant and smoother than any of these other implant materials.