Greater Trochanter:  
A large projection on the end of the femur near the hip.   Numerous muscles attach to the femur at this location.

Intramedullary Canal or Medullary Canal:  
The canal that runs up the center of the femur.  The prosthetic stem is placed in this canal as part of hip replacement surgery.

Lap Sponge:  
A sterile gauze pad used to absorb blood and fluids or clean surgical areas during surgery.

Osteoarthritis:  
The most common type of arthritis. It affects many joints in the body, including the hip.  It is a chronic disease and is characterized by destruction of cartilage, overgrowth of bone, bone spur formation and impaired function.  This type of arthritis occurs when bone rubs against bone. Most people develop osteoarthritis as they age.

Osteophytes:  
Abnormal projections of bone, also known as bone spurs.   These are usually caused by increased stress on the ends of the bones.

Osteotome:  
A chisel-like surgical instrument used to remove osteophytes or bone spurs during hip surgery.

Plastic Liner:  
This goes inside the metal acetabular cup and cushions the metal ball of the hip prosthetic.  The liner serves much the same function as cartilage does in a healthy hip – it prevents the metal parts of the prosthetic from rubbing against each other.

Piriformis Tendon:  
The tendon that connects the piriformis muscle to the head of the femur.

Piriformis Muscle:  
The piriformis muscle travels behind the hip joint, running horizontally from the lower spine to the top of the femur. The piriformis runs over the sciatic nerve and it aids in external rotation, or turning out, of the hip joint.

Prosthesis (plural, Prostheses): 
An artificial body part designed to supplement or replace natural parts.  In hip replacement surgery, the prosthetic components replace the end of the femur, the ball of the hip (head of the femur) and the cup of the hip, or acetabulum.

Range of Motion:  
The acceptable amount of movement a joint should be able to perform.  Range of motion tests are performed in all joint replacement surgeries to ensure that the prosthetic joints work appropriately.

Rasp:  
A surgical tool used to remove small amounts of bone by shaving or sanding the bone down.  Rasps are used to size the femur to accept the stem prosthetic in hip replacement surgery.

Rongeur:  
A surgical instrument used to remove osteophytes, or bone spurs, during hip replacement surgery.

Sciatic Nerve:  
The largest single nerve in the human body.  The sciatic connects to nearly all of the skin of the leg, the muscles of the back of the thigh, the leg and the foot.  It passes out of the pelvis below the Piriformis muscle. It descends the back of the thigh to about its lower third, where it divides into two large branches.

Stem:  
The metal prosthetic piece that goes in the femur during a hip replacement surgery.

Subcutaneous:  
Literally ‘under the skin.’  In surgeries, this usually refers to this usually refers to the layer of fat that exists just beneath the skin.  This layer is often sutured together separately from the skin to make the surgical closure more secure.

Template:  
A plastic guide used to help surgeons determine the correct size of replacement prosthetics to use for a patient.  The surgeon uses the plastic template to measure the size of the acetabulum and the canal in the femur by holding it up against an enlarged x-ray.

Tensor Fascia Lata:  
Aids in muscle movements and can also provide an attachment site for muscles and act as a cushioning layer between them.  The tensor fascia lata runs from the hip down the thigh and provides stability for the leg as well as medial rotation, or rotation in toward the other leg.