Sidewise movement of the leg away from the body.

Acetabular Cup

When inserting a hip implant, the acetabulum is kept intact, but is hollowed out to make room for a cup that is inserted into the hip socket to make the other half of the hip joint fit smoothly. This cup is called the acetabular cup.


A cup-shaped depression on the external surface of the hipbone into which the head of the femur fits. The “socket” part of the ball and socket hip joint.


Sideward movement of the leg towards the body.


Method to produce loss of sensation with or without loss of consciousness.

Arthritis, Rheumatoid

Inflammation of a joint or joints characterized by pain and stiffness of the affected parts.


An orthopedic surgery in which joint cartilage is replaced by artificial joint components to correct advanced degenerative arthritis or some types of trauma.

Articular Cartilage

A resilient tissue that covers the surface of bones where they meet in a joint. The cells of articular cartilage are grouped in small clusters separated by a matrix of collagen fibers and protein-carbohydrate molecules, allowing bones to glide smoothly over each other.


A resilient white tissue found in various parts of the body, such as the joints (see: articular cartilage), outer ear, and larynx.


Short for ‘Computer-assisted (or aided) surgery’. See: Image-guided Surgery

CAT Scan

A computed axial tomography (CAT) scan is a non-invasive diagnostic test that uses rotating X-Ray equipment, combined with a computer, to obtain images of the body. Also known as computed tomography (CT) scan.

Computer Navigated Surgery

See: Image-guided Surgery

Computer-Aided Surgery

See: Image-guided Surgery

Computer-Assisted Surgery

See: Image-guided Surgery Computer-Assisted Intervention See: Image-guided Surgery

Conventional Hip Replacement

Hip replacement surgery done without the assistance of a navigation system.


Non-inflammatory degenerative disease of the hip joint which usually appears in late middle or old age. It is characterized by growth or maturational disturbances in the femoral neck and head, as well as acetabular dysplasia.


A computed tomography (CT) scan or computed axial tomography (CAT) is a noninvasive diagnostic test that uses rotating x-ray equipment, combined with a digital computer, to obtain images of the body.


Movement of an extremity posterior to or behind the body.

External Rotation

Turning the thigh outward.


Of or relating to the femur or thigh bone.

Femoral Head

Rounded ball at the end of the upper femur or thighbone, which articulates or moves within the acetabulum or cup of the pelvis.

Femoral Neck

Supports the femoral head and gives the femur leverage.


The long bone of the thigh.


Movement of an extremity anterior to or in front of the body.

Functional Outcome

A measurement of how well an anatomical part or organ performs after surgery. Better functional outcome is a goal of surgical procedures.


Is the partial replacement of bone with a prosthesis. It is generally used for a patient with a fractured hip, but is also effective in other areas, such as the shoulder.


Region on each side of the pelvis; made up of three sections: ilium, ischium and pubis; the upper part of the femur (thighbone) fits into the hip via a ball-and-socket joint; the socket is the cup-shaped bone of the pelvis called the acetabulum and the ball is the head of the femur.

Hip Abductors

Muscles of the outer hip, attached to the thighbone.

Hip Adductors

Muscles of the inner thigh.

Hip Replacement

Substituting a diseased hip joint with an artificial hip joint to correct for mechanical disorders or painful conditions as created e.g. by advanced degenerative arthritis. Hip replacement surgery can be performed as a total hip replacement or a hip resurfacing.

Hip Resurfacing

A hip resurfacing system is a hip replacement system that does not remove a part of the patient's femur to accommodate the femoral component. Instead, the top of the femur is simply capped with a prosthetic replacement and a acetabulum is inserted into the pelvis (as in a total hip replacement).

Hip Socket

Part of the ball-and-socket hip joint between the head of the thigh bone and hip bone.


A disease having no known cause.


Short for ‘image guided surgery’.

Illiofemoral Ligament

A ligament that connects the femur to the pelvis. A strong band of dense fibrous tissue that connects the femur to the pelvis.


The upper part of the pelvic bone which forms the receptacle of the hip.

Image-Guided Surgery

A tool used in orthopedic surgery that utilizes infrared cameras, digitized bone images and tracking devices to give surgeons increased visualization during the procedure; the benefits may include better alignment and greater accuracy in hip replacement surgeries. Also known as computer-assisted intervention, computer navigated surgery, image guided surgery (IGS), information-guided surgery, navigated surgery, software-guided surgery, surgical navigation.


Instrument used to place the cup in the accetabulum. Also called ‘Cup Inserter’.


A condition where malpositioned bones restrict movement . If these bones squeeze tendons or other soft tissues, inflammation and pain may result.


A physical response to an injury at the site of damage. The signs of inflammation are: redness, heat, swelling, pain and loss of function, although, not all of these signs are necessarily present.

Infrapubic Angle

Angle below the pubis.

Infrared Camera

Infrared is a type of light that we cannot see with our eyes. Our eyes can only see what we call visible light. Infrared cameras scan, detect and provide visual representation of infrared light emitted by objects. In navigated surgery, an infrared camera picks up the location and motion of special reflective spheres attached to human anatomy and surgical instruments.

Inguinal Ligament

The inguinal ligament runs from the pubic tubercle to the anterior superior iliac spine.

Internal Rotation

Rotating or turning the hip inward.


Occurring, carried out, or encountered during the course of surgery.

Ischiofemoral Ligament

The ischiocapsular ligament consists of a triangular band of strong fibers on the posterior side of the hip joint. Its fibers span from the ischium at a point below and behind the acetabulum to blend with the circular fibers at the posterior end of the joint capsule and attach at the intertrochanteric line of the femur.


The curved bone forming the base of each half of the pelvis.


Where ends of two or more bones meet.

Joint Replacement

Substituting a diseased joint with an artificial joint to correct mechanical disorders or painful conditions created e.g. by advanced degenerative arthritis. Hip replacement surgery can be performed as a total hip replacement or hip resurfacing.


A fibrocartilaginous rim attached to the margin of the acetabulum of the hipbone.


Lying on the side or with the face sideward.

Lateral rotator muscle group

The Lateral rotator group is a group of muscles of the hip which all externally (laterally) rotate the femur in the hip joint.

Leg Length Discrepancy

Limb length discrepancy (LLD) is a difference in anatomic or functional leg lengths.

Leg Length Offset/Femoral Offset

Femoral offset is the distance from the center of rotation of the femoral head to a line dissecting the long axis of the femur. In case of total replacement hip the the offset is considered as the distance from the center of rotation of the femoral head to a line bissecting the long axis of the stem.


A band of fibrous tissue that connects two bones, cartilages or other structures.

Magnetic Resonance Imaging (MRI)

A type of diagnostic radiography that uses a powerful magnetic field to create images of tissues and organs.

Marker Spheres

Special reflective spheres are attached to the human anatomy and surgical instruments during navigated surgery; an infrared camera picks up their location and motion. Also known as ‘reference spheres’.

Minimally Invasive Surgery

A technique used to perform surgery on the joints; involves a small incision and therefore less cutting of normal tissue and muscles resulting smaller scar and possibly less post-operative pain and a faster return to normal activity.


Short for: ‘Magnetic Resonance Imaging’

Navigated Surgery

See: Image-guided Surgery Navigation System A combination of infrared cameras, digitized bone images and tracking devices that give surgeons increased visualization during a surgical procedure. Also known as software-guided system.


Premature death of living cells and tissue. Usually, necrosis occurs as a result of infection, toxins, or trauma to the area.

Obturator Artery

An artery with origin in the internal iliac artery, with distribution to the ilium, pubis, obturator and adductor muscles and with pubic, acetabular, anterior, and posterior branches.

Obturator Nerve

Arises from the lumbar plexus, conveying fibers from the second, third, and fourth lumbar nerves in the psoas muscle, crosses the brim of the pelvis, and enters the thigh through the obturator canal; it supplies muscles of the medial compartment of the thigh (adductors of thigh at the hip joint) and terminates as the cutaneous branch of the obturator nerve, supplying a small area of medial thigh above knee.

Orthopedic Surgeon

A specialized physician that performs surgical procedures to correct or prevent deformities, disorders, or injuries of the skeleton and associated structures.


A branch of medicine concerned with the correction or prevention of deformities, disorders, or injuries of the skeleton and associated structures, such as tendons and ligaments.


Arthritis marked by degeneration of the cartilage and bone of joints. Also known as: OA, degenerative arthritis, degenerative joint disease, hypertrophic arthritis.


The death of bone, often as a result of obstruction of its blood supply.


Loss of bone or atrophy of skeletal tissue that causes bones to weaken and become brittle and prone to fracture. Preventive measures include adequate calcium intake and regular exercise to stimulate bone metabolism.


Literally: ‘bone cutting’. Used to describe surgical procedures in which bone is cut and realigned.

Partial Hip Replacement

Partial hip replacement, also referred to as a hemiarthroplasty, generally only replaces the femoral head, though it may in some cases only replace the acetabular cup.


Flat triangular bony disc protecting the knee joint; also known as kneecap.


Having to do with the pelvis, the lower part of the abdomen, located between the hip bones.


The massive cup-shaped ring of bone in the lower half of the trunk, formed by the hip bone on either side and in front, and the sacrum and coccyx in the back.

Pelvis Tilt

Rotation of the pelvis around either a horizontal (forward or backward tilt) or vertical (tilt to the left or right side) axis.


A type of thermoplastic used to make surgical implants, prostheses and medical tubing.


Occurring before a surgical operation.


Manufactured substitute for a diseased or missing part of the body.


Front center portion of the pelvis.

Pubofemoral Ligament

The pubofemoral ligament (pubocapsular ligament) is a ligament on the inferior side of the hip joint.


The greater extensor muscle of the front of the thigh that is divided into four parts. Also known as quadriceps femoris; quadriceps muscle.

Range of Motion (ROM)

How far a joint can move: active range of motion is the extent to which a joint can be moved actively by surrounding muscles; passive range of motion is the extent to which a joint can be moved by an external force.


A rotating drilling tool used to shape or enlarge a hole, such as for placement of hip implant components.

Reference Markers

See: ‘Marker spheres’

Resection Arthroplasty

A procedure in which the surfaces of diseased bone are removed, allowing fibrocartilage to grow in its place.

Revision Surgery

Surgery to remove, replace or reposition a defective prosthesis or prosthesis component.

Sacroiliac joint

The joint formed by the articulation of the sacrum and ilium.


One of the three bones that make up the pelvic ring.

Sartorius Muscle

A muscle in the thigh that helps to rotate the leg into the sitting position assumed by a tailor; the longest muscle in the human body.


The data or image obtained from the examination of organs or regions of the body with an imaging device, such as a CT or MR scanner.

Software-Guided Surgery

See: ‘Image-guided Surgery’


Looseness or slipping of the femoral head within the acetabulum.


Lying on the back with the face upward.

Surgical Navigation

See: ‘Image-guided Surgery’

Synovial Fluid

A clear lubricating fluid lining joints and secreted by the synovial membrane.

Synovial Membrane

Thin connective membrane lining joints and secreting synovial fluid


Fibrous connective tissue joining muscle to bone.


Short for ‘Total hip replacement’.

Total Hip Arthroplasty

See: ‘Total Hip Replacement’

Total Hip Replacement

Surgical replacement of hip joint with prosthesis. In general, the surgery consists of replacing the diseased or damaged joint surfaces of the hip with metal, plastic or ceramic components shaped to allow continued motion of the hip; also known as THR or total hip arthroplasty.

Traumatic Arthritis

Arthritis marked by degeneration of the cartilage and bone of joints caused by injury or accident; also known as post-traumatic arthritis or injury-induced arthritis.


One of two bony ridges (the greater and lesser trochanters) near the upper end of the femur.


Electromagnetic radiation used to produce images of bones.