Orthopedics Exam 1 Vocabulary Flashcards

Vocabulary flashcards covering embryonic musculoskeletal development, knee and joint pathology, connective tissue histology, fracture mechanics, and lower extremity dislocations.

Paraxial mesoderm

The mesodermal column located immediately lateral to the neural tube and notochord that segments into somites to form the axial skeleton, voluntary muscles, and dermis.

Apical Ectodermal Ridge (AER)

A specialized ectodermal structure at the distal rim of the growing limb bud that secretes FGF8 and FGF4 to direct proximal-distal limb outgrowth.

Zone of Polarizing Activity (ZPA)

A signaling region located in the posterior mesenchyme of the limb bud that secretes Sonic hedgehog (Shh) to control anterior-posterior patterning and digit identity.

Fissure of Von Ebner

The intrasegmental cleft splitting each sclerotome into a loose cranial half and a dense caudal half during vertebral re-segmentation, creating spaces for spinal nerves to exit.

Epaxial muscles

Intrinsic muscles of the back derived from the dorsomedial myotome (epimere) and innervated by posterior rami of spinal nerves.

Hypaxial muscles

Muscles of the anterior neck, torso, limbs, and perineum derived from the ventrolateral myotome (hypomere) and innervated by anterior rami of spinal nerves.

Achondroplasia

Disproportionate dwarfism caused by an FGFR3 gene mutation leading to impaired chondrocyte proliferation and premature growth-plate closure, characterized by short limbs and a mature height ≤147 cm.

Segond fracture

A bony avulsion fracture of the lateral tibial plateau that is pathognomonic for an anterior cruciate ligament (ACL) rupture.

Arcuate sign

An avulsion fracture of the proximal fibular head that is pathognomonic for a posterolateral corner injury of the knee.

Unhappy triad

A severe, unstable knee injury characterized by the simultaneous rupture/injury of the anterior cruciate ligament (ACL), medial collateral ligament (MCL), and medial meniscus.

Baker's cyst

A fluid collection in the popliteal fossa located specifically between the medial head of the gastrocnemius and the semimembranosus tendon, often secondary to intra-articular pathology like osteoarthritis.

Rosenberg view

A weight-bearing flexed-knee (60°) PA radiographic projection used to identify posterior femoral condyle cartilage loss ("bald spot") not visible on extended views.

Merchant view

A sunrise/sub-patellar radiographic view angled to evaluate patellofemoral joint space narrowing, tracking, and articular wear.

Enthesis organ

A specialized anatomic junction where a tendon, ligament, or joint capsule inserts into bone, transitioning through fibrocartilage to dissipate shear stress.

Osgood-Schlatter disease

Traction apophysitis of the tibial tuberosity caused by repetitive quadriceps contraction via the patellar tendon in skeletally immature athletes.

Acute Compartment Syndrome

An ischemic emergency where elevated pressure within an osteofascial compartment halts capillary perfusion, leading to irreversible muscle and nerve necrosis if not treated with fasciotomy.

Salter-Harris classification

A system grading pediatric growth plate (physeal) fractures from Type I to V based on injury pattern relative to the physis, metaphysis, and epiphysis.

Wolff's law

The biological principle stating that bone remodels and deposits matrix along the specific lines of mechanical stress or physical force placed upon it.

Bankart lesion

An avulsion of the anteroinferior glenoid labrum and attached inferior glenohumeral ligament complex caused by anterior shoulder dislocation.

Hill-Sachs lesion

A cortical compression fracture on the posterolateral aspect of the humeral head caused by impaction against the anterior glenoid rim during dislocation.

Nursemaid's elbow

Pediatric subluxation of the radial head resulting from sudden axial traction that slips the immature annular ligament into the radiohumeral joint space.

Maisonneuve fracture

A proximal fibular shaft fracture that occurs secondary to a rotational force transmitted proximally from an ankle injury through the interosseous membrane.

Danis-Weber classification

A system classifying ankle fractures into Types A, B, and C based on the level of the lateral malleolus fracture relative to the ankle mortise.

Lisfranc ligament

An oblique interosseous ligament extending from the medial cuneiform to the base of the second metatarsal that stabilizes the tarsometatarsal joint complex.

Fleck sign

A pathognomonic avulsion fragment in the space between the medial cuneiform and second metatarsal base, indicating a torn Lisfranc ligament.