Hip Implants

Hip Implants

Hip implants are artificial devices that form the essential parts of the hip joint during a hip replacement surgery. The hip implants vary by size, shape and material. Implants are made of biocompatible materials that are accepted by the body without producing any rejection response. Implants can be made of metal alloys, ceramics or plastics, and can be joined to the bone. The metals used include stainless steel, titanium and cobalt chrome, whereas the plastic used is polyethylene. Various components of a hip implant may be used for a hip replacement surgery. The components used may depend on the extent of damage to the hip joint and the preference of your orthopaedic surgeon.

Components of a hip implant

The hip joint is a ball-and-socket joint. The ball or the spherical head of the thighbone (femur) moves inside a cup-shaped socket (acetabulum) of the pelvis.

The components of a hip implant replicate the natural shape and structure of the ball-and-socket joint. The components used may depend on the size of the body and vary from patient to patient. A total hip replacement implant has three parts:

  • Stem: The stem fits into the femur
  • Ball: The ball replaces the spherical head of the femur
  • Cup: The cup replaces the worn-out hip socket

Types of hip implants

Based on your activity level, any of the following types of hip implants may be used in a hip replacement surgery.

Metal-on-polyethylene implant: The ball is replaced with a metal ball and the socket is replaced with polyethylene or has a polyethylene lining.

Ceramic-on-polyethylene implant: The ball is replaced with a ceramic ball and the socket is replaced with polyethylene or has a polyethylene lining.

Metal-on-metal implant: The ball and socket of the hip joint are replaced with metal prosthesis. Metal-on-metal implants have greater durability compared to metal-on-polyethylene implants.

Ceramic-on-ceramic implant: The ball is replaced with a ceramic ball, and the socket has a ceramic lining. They wear less than metal-on-metal implants, and are most durable among the available hip implants.

Ceramic-on-metal implant:  The ball is replaced with a ceramic ball and the socket has a metal lining.

Types of implant fixation

Depending on your age and activity level, your orthopaedic surgeon may recommend any of the available three types of implant fixation.

Cemented fixation


The femoral and acetabular components are held together with special bone cement. The bone cement is made from a special polymer called polymethylmethacrylate (PMMA). Patients can often immediately be full weight bearing and walk after a cemented fixation. Cemented fixation is an option for less active patients. However, too much stress on cemented fixation can lead to fatigue fractures.

Cementless fixation


Cementless implants are coated with a porous material. They attach to the new bone that grows to the surface of the implant via bone ingrowth. The implant may be fixed using screws or pegs until bone ingrowth. Patients need to limit weight-bearing and use crutches or a walker following cemented fixation to allow the bone to attach itself to the implant. Cementless fixation is an option if you lead a more active lifestyle and have good bone quality.

Hybrid fixation


Hybrid fixation uses a combination of cemented and cementless fixation. The acetabular socket is inserted without cement and the femoral stem is inserted with cement.

Luton and Dunstable University Hospital
  • Spire Healthcare
  • OSD Healthcare
  • The London Clini
  • One Hatfield Hospital
  • http://cobhamclinic.co.uk/
  • The Royal College of Surgeons of Edinburgh