Hip

Hip replacement surgery, or total hip arthroplasty, involves removing a diseased
hip joint and replacing it with an artificial joint called a prosthesis/
hip implant.

Hip implants consist of:

• a socket (acetabular cup/shell), which has an insert or liner made of plastic, ceramic, or metal
• a ball component (femoral head), made of metal or ceramic
• a metal stem (femoral stem) made of titanium- or cobalt/chromium-based alloys (In some designs, the stem and ball are one piece; other designs are modular, allowing for additional customization)

Hip implants are usually made of cobalt chrome (e.g. ASTM F1537), titanium (e.g. Ti6Al4V ELI), or medical-grade stainless steel (316LVM).

Properties:

• Fixturing is a challenge
• Small batch production
• Some forged and cast blanks for the stem
• Bar work for the femoral head and cup

The machines typically used for the component include multiaxis machines, 3-axis lathes, 5-axis VMCs, and multitask machines (e.g. Mazak Intergrex E410e).

Circular ramping machining of the internal sphere is a highly effective and secure process, with the benefits of longer tool life, less tool breakage, and short cycle time, resulting in high-quality surfaces. Preferably use positive round inserts.

Benefits of machining the external sphere include increased tool life and a secure process.

External head machining gives high-quality surfaces and increased tool life in a secure process. Preferably use positive round inserts.

Head taper hole machining is an effective process for a flat bottom.

Selected component features

• Acetabular cup
• Femoral head