In addition to John Insall, who applied the first total knee prosthesis in 1973, the first total hip replacement was applied on the patient by another British orthopedic surgeon, John Charnley, about 10 years before him. John Charnley, who put forward the definition of ‘low friction arthroplasty’, applied the ‘Ultra high molecular weight polyethylene’ design as an acetabular component, but also designed the non-modular metal femoral component. Dr. Charnley also found cement to fix components to bone, paving the way for its widespread use in the Orthopedics world. For this reason, it deserved to be a pioneer in hip replacement surgery.
The simple designed polyethylene implants used in the first total hip prosthesis have turned into much more different and perfect materials today as technology has developed. On the other hand, All poly design prostheses are still used cemented by many surgeons.
Total hip prostheses consist of four separate components: femoral component, acetabular component, modular or non-modular neck head and insert. Although cemented prosthesis designs are also available today, the most common use is cementless prosthesis designs. For this reason, features of cementless prosthesis will be explained in detail.
Acetabular component consists of titanium material; The inner surface is designed as smooth and shiny, and the outer surface as a porous coating to provide osseointegration with the bone. Sometimes the outer surface can be used as a hydroxyapatite coating. In cases where primary stability cannot be achieved, stability is provided with one or two screws. The inner surface of the acetabular component is produced in accordance with the placement of polyethylene or ceramic inserts according to the patient’s age or the surgeon’s preference.
The femoral component is again made of titanium material; The outer surface is designed as a porous coating to provide osseointegration. Like the acetabular shell, the femoral component also has a hydroxyapatite coating feature. HA(hydroxyapatite) coated prostheses can be preferred to increase adhesion (osseointegration), especially in young patients. There is no screw-like attachment like an acetabular shell to increase adhesion on the femoral component. For this reason, primary stability is provided as press-fit. In this context, reaming and broaching should be done very carefully. The femoral component can be used with a modular or non-modular neck. Since corrosion and associated wear are common in modular neck prostheses, non-modular neck femoral components are generally preferred. The head can be preferred as Co-Cr or ceramic. Ceramic heads should be preferred in young patients to reduce wear.
It can be preferred as an insert (core) ceramic or polyethylene. While ceramic insert may be preferred to reduce wear in young patients, care should be taken that it is fully compatible with Shell. Otherwise, insert breaks and squeak sound become a serious problem. For this reason, young surgeons should prefer polyethylene inserts that can compensate for some component placement errors, as well as having very close wear property to the ceramic insert.
