Dr. Pieter J Botha
HIP JOINT REPLACEMENTS - “Hip Arthroplasty”
A total hip replacement is a surgical procedure in which the diseased femur (head of the hip joint) is removed and replaced with the new artificial part. The damaged cartilage articulation surface within the acetabulum is replaced with artificial surfaces.
Incision
There are various lines of insicion. Dr Botha prefers to cut Posterior-Lateral. The cut is made through the skin, fatty tissue and longitudinal (in the length) into the muscle. The muscles are then re-tracted to enable the surgeon to get to the hip capsule.
Femur Preperation
The surgeon will dislocate your hip and will remove the damaged femur head
Your femur shaft will be reamed to prepare the Femur shaft to receive the stem. The stem will be inserted, whereafter the artificial head will be attached.
Acetabulum Preperation
The Acetabulum will be reamed, whereafter the artificial cup and liner will be inserted.
Relocation of new artificial hip components
Hip joint components
There are various implant designs available, but no consensus as to if and which design is better than the other. Your orthopaedic specialist will decide which design is best for you based on: your age, your weight, your activity level, the strength of your bones and the shape and condition of your joint.
Prostheses can be cemented or un-cemented. The use of cement is also based on the above mentioned factors. Each prosthesis is made up of four main parts.
The acetabular component (socket part in the pelvis) replaces the cup like surface in the pelvis called the acetabulum. The acetabular component is usually made of two parts: the metal / plastic cup which attaches directly to the pelvic bone and a plastic or ceramic spacer that is placed within the metal cup to ensure a smooth articular surface with the ball of the stem. The plastic liner is made of High Molecular Weight Polyethylene.
The femoral component (bottom part) replaces the femoral head (ball-like articular surface) of the upper bone (the femur). The femoral component is made of a metal stem, usually a metal alloy – titanium alloy or cobalt-chromium alloy. The stem has a femoral head that attaches to it to mimic the femoral head in the joint. The femoral head can either be made of metal or ceramic.
Cemented Implants VS Un-Cemented Implants
Cemented Implants
Bone cement is used to fix the implants to the bone, the component is fixed within 8 minutes and solid. The bone cement is mixed into a putty-like consistency. The bone cement is pressurized into the porous bone with the cement gun.
Stem
Polyethelene
Cup
Cement
The implants are fixed to the bone due to the fact that the cement is pressurized into the porous bone
Finished cemented hip relacement.
Head can be metal or ceramic
Vacuum mixing bowl
Cement gun
Un-Cemented Implants
Your own bone must grow into the metal particles, this will take up to 6 weeks before it is consolidated.
The implants porous metal coating is impacted onto the porous bone. The bone will grow into the porous metal.
If you have good bone quality the prosthesis will be compacted into your bone where your bone will grow into the metal.
If you have poor bone quality, the surgeon may have to use screws, artificial bone or wedges to secure a better fit.
Finished un-cemented hip relacement
Liner can be either polyethylene or ceramic.
Head can be metal or ceramic
