Skeletal Dysplasia Definitions


Acromelia - shortening of the terminal parts of the limbs (hands and feet) in relation to the upper and middle limb segments.

Atlantoaxial Instability - abnormal extra motion occurring between the first and second cervical vertebrae (C1 and C2). This extra motion places the spinal cord at risk as it travels between C1 and C2. Typically this results from either an abnormal odontoid process or ligamentous laxity.

Amniocentesis - a procedure typically done with ultrasound guidance in which a needle is passed through the abdominal wall and the uterus and into the fluid which surrounds a baby. Some of the amniotic fluid is then removed thru the needle and this fluid can be used for various types of genetic testing. This is typically done at 16-18 weeks gestation.

Anterior - relating to the front of the body.

Autosomal Dominant - when a condition is caused by having only a single mutant copy of a particular gene and that gene is located on one of the 22 pairs of autosomal chromosomes.

Autosomal Recessive - when a condition is caused by having two mutant copies of a particular gene and that gene is located on one of the 22 pairs of autosomal chromosomes.


Brachydactyly - Short fingers or toes.


Carpals - the eight bones of the wrist.

Central Apnea - temporary cessastion of breathing due to the failure of the respiratory centers in the brain to properly control the process of breathing.

Cerebral vascular system - the system of blood vessels in which blood flows to and from the brain.

Cervical Spine - relating to the vertebrae found at the level of the neck.

Chondrocytes - cartilage cells.

Chorionic Villus Sampling (CVS) - a procedure typically done with ultrasound guidance in which a needle is passed through the abdominal wall and the uterus
and into the developing chorionic tissues. Some of the tissue is removed thru the needle
and can be used for various types of genetic testing. This is typically done at 9-12
weeks gestation.

Cloverleaf Skull - a severe form of craniosynostosis that involves a premature closure of every suture of the skull.

Clubfoot - a congenital anomaly of the hindfoot that restricts the ability to stand with the sole of the foot flat on the ground.

Coxa valga - an abnormality of the hip in which the angle between the top of the femur and the femoral shaft is larger than normal.

Coxa vara - an abnormality of the hip in which the angle between the top of the femur and the femoral shaft is smaller than normal.

Craniosynostosis - a premature closure of the sutures or growth plates in the skull.


Diaphyseal - of or relating to the diaphysis.

Diaphysis - the middle or shaft part of a long bone.

Disproportionate short stature - short stature where the the limbs or trunk are not in proportion to each other.

Distal - on the limb in the direction away from the body.

Ductus arteriosus - one of the two shunts in the fetal heart located between the pulmonary artery and aorta. This passage way allows blood to bypass pulmonary circulation. Oxygen is delivered to the fetus via the placenta and the mothers blood. Once the baby is born and the lungs inflate, the shunt closes so that pulmonary circulation is separated from systemic circulation.

Dysplasia - an abnormality of development of a body tissue or organ.


Echocardiogram - A procedure that uses sound waves and echoes to show the structure and movement of the heart.

Endochondral Bone Formation - the type of bone formation that occurs at the growth plates of the long bones.

Epiphyseal - of or relating to the epiphysis.

Epiphysis - the ends of the bone of the long bones.


Femur - thighbone; long bone located between the hip and knee.

Fibula - the outer and more narrow bone of the two bones connecting the knee
and ankle.

Flexion/Joint Contractures - inability to fully straighten the joints.

Fontanel - the "soft spots" between the incompletely fused cranial bones.

Foramen Ovale - One of the two shunts in the fetal heart that allows blood to flow from the right atrium to the left atrium, so that blood bypasses pulmonary circulation. This shunt should close within the first year of life when the lungs are functional and pulmonary pressure decreases.


Genitourinary tract - the system composed of the urinary and reproductive organs.

Genu Valgus - bowing of the legs inward so that the knees point inward. This is also called knock-knees.

Genu Varus - bowing of the legs outward so that the knees turn to the sides. This is also called bow-legged.


Hydrocephalus - a condition that is characterized by a dilatation of the cerebral ventricles caused by an obstruction of the fluid passages inside the brain. The fluid accumulates, causes increased pressure and can lead to enlargement of the head, mental or neurological problems. Also called water on the brain.

Hydromelia - dilated spinal canal.

Hyperplasia - an abnormal increase in tissue/bone growth.

Hypoplasia - underdevelopment of body tissue or organ.

Hypotonia - A decrease in muscle tone or strength.

Hypoxia - Inadequate amount of oxygen getting to the bodily tissues.


Ilia - The wide, upper part of the pelvis.

Interpediculate Distance - The width of the vertebrae of the spine, as measured between the pedicles.


Kyphosis - A rounding or hunching over of the back.


Lateral - away from the midline of the body.

Ligamentous Laxity - loose joints.

Lumbar Lordosis - the forward bending of the lower spine. Also called sway back.

Lumbar Spine - relating to the vertebrae found in the lower back.


Macrocephaly - abnormally large head size.

Medial - towards the midline of the body.

Mesomelia - shortening of the middle parts of the limbs (forearm and foreleg) in relation to the upper and terminal segments.

Metacarpals - the bones of the hand located between the fingers and wrist.

Metaphyseal - of or relating to the metaphysis.

Metaphysis - the widening region of the long bone in which the epiphysis and
diaphysis meet.

Microcephaly - a small head.

Micrognathism - a small jaw.

Micromelia - a symmetric shortness of the limbs.

Mosaicism - phenomenon in which genetically different tissues occur in the
same organism.

Mutation - when the sequence of the nucleotides of DNA is incorrect, possibly due to a deletion or repeat of a certain nucleotide base. The result is a defect in the protein for which the gene encodes. In other words, there is a change in the recipe for a certain protein that causes a problem in the final product.

Myelopathy - disturbance of the spinal cord.


Obstructive Apnea - temporary cessation of breathing due to the blockage of airflow into and out of the lungs with normal respiratory drive.

Odontoid Process - normal bony peg of the second cervical vertebrae that allows the neck to rotate.

Ossification - process by which cartilage calcifies and changes into bone.

Osteotomy - surgical cutting of bone as a realignment procedure.


Patent - open.

Pavlik harness - a soft brace with straps worn to maintain the hip joint in the
correct position.

Pectus Carinatum - "Pigeon Chest" due to a protruding sternum.

Phalanges - bones of the fingers.

Philtrum - space between the upper lip and nose.

Platyspondyly - flatness of the vertebral bodies.

Polydactyly - having extra fingers or toes.

Posterior - relating to the back of the body.

Proximal - on the limb in the direction toward the body.


Rhizomelia - shortening of the upper parts of the limbs (upper arm and thigh) in relation to the middle and terminal segments.


Scoliosis - a curvature or lateral deviation of the normally straight vertical line of
the spine.

Spondylo - of or relating to the spine.

Stenosis - narrowing or stricture of a passageway such as the windpipe or spine.

Subluxation - abnormal bone movement within a joint; similar to a dislocation.

Symphalangism - fusing together of the finger joints.


Thoraco-lumbar Kyphosis (TLK) - a forward bending of the spine occurring in the middle and lower back.

Thoracic Spine - relating to the vertebrae found at the level of the ribs and chest.

Thorax - area of the body between the neck and lower rib cage.

Tibia - the inner and wider bone of the two bones connecting the knee and ankle.

Trachea - the tube through which inhaled air will flow on its way to the lungs.

Tracheobronchial Tree - The structure within the chest consisting of the trachea and branching bronchi; its shape is likened to an upside-down tree.

Tracheostomy - a surgical procedure in which an opening is made in the trachea in the region of the neck in order to create an airway.


Ventilation - a state in which a mechanical piece of equipment is used to breath for a patient. The machine is connected to a tracheostomy tube.


X-linked - when a condition is caused by having a single mutant copy of a particular gene and that gene is located on the X chromosome.