🥇 ARTICULACIONES DE LA MANO. (Carpianas, Carpometacarpianas, Metacarpofalangicas e Interfalangicas)

Introduction to Hand Joints

Overview of the Video

• The video is presented by Juan José Sánchez, focusing on the anatomy of hand joints.

• It emphasizes the importance of understanding the arrangement of hand bones before diving into joint discussions.

Structure of Joint Study

• The study will progress from proximal (closer to the body) to distal (further from the body), starting with carpal joints.

• Joints will be categorized into five main groups: carpal joints, metacarpal-carpal joints, intercarpals, metacarpophalangeal joints, and interphalangeal joints.

Understanding Carpal Bones

Review of Carpal Bones

• There are eight carpal bones in total; their identification is crucial for understanding joint articulations.

• The upper row consists of scaphoid, lunate, triquetrum, and pisiform; while the lower row includes trapezium, trapezoid, capitate, and hamate.

Metacarpals and Phalanges

• Five metacarpals are counted from lateral to medial; phalanges include proximal phalanx (attached to metacarpals), middle phalanx (between proximal and distal), and distal phalanx.

• Notably, the thumb has only a proximal and a distal phalanx without a middle one.

Carpal Joint Articulations

Grouping Carpal Joints

• The discussion begins with articulations among the first row of carpal bones: scaphoid, lunate, triquetrum, and pisiform.

Characteristics of Joints

• These bones do not all connect directly; they form flat-type or arthrodial joints due to their relatively flat surfaces.

Understanding Carpal Ligaments and Joints

Overview of Interosseous Ligaments

• The interosseous ligaments connect the bones in the wrist, specifically between adjacent carpal bones. These ligaments are crucial for maintaining stability within the wrist structure.

Identifying Anterior and Posterior Views

• The dorsal tubercle of the radius helps distinguish between anterior and posterior views. The presence of specific bones like the hamate indicates an anterior view, while others like pisiform confirm this orientation.

Palmar and Dorsal Ligaments

• Palmar radiated ligaments (green) originate from the ulna and radius, while dorsal ligaments connect carpal bones in a more complex arrangement. Understanding these groups is essential for studying wrist anatomy.

Articulations of Carpal Bones

• The first row of carpal bones includes scaphoid, lunate, and pisiform. Their articulations are vital for wrist movement; notably, the pisipyramidal joint forms between pisiform and piriformis.

Pisiform Joint Structure

• The pisipyramidal joint features a convex shape from piriformis fitting into a concave shape from pisiform. This flat-type joint allows for limited but necessary movement within the wrist.

Key Ligaments Supporting Pisiform

• Five key ligaments stabilize the pisiform:

• Pisicubital ligament connects to ulna.

• Pisigarchous ligament links to hamate.

• Pisiunciform ligament connects to uncinate process.

• Additional connections include those with metacarpals.

Exploring Second Row Carpal Bones

Identification of Trapezium and Adjacent Bones

• Starting laterally with trapezium (attached to thumb), followed by trapezoid, large bone (capitate), and hamate. Recognizing these relationships aids in understanding hand mechanics.

Joint Types Among Carpal Bones

• Most joints among carpal bones are classified as arthroid joints (flat-type). This classification is significant as it influences mobility patterns across different movements in the wrist.

Internal Ligament Connections

• Three internal ligaments connect:

• Hamate with large bone,

• Large bone with trapezoid,

• Trapezoid with trapezium.

These connections play a critical role in maintaining structural integrity during motion.

Visualizing Thumb Orientation

• A clear visual representation helps identify thumb-related structures: trapezium is lateral; other bones follow sequentially towards medial alignment. This visualization simplifies anatomical learning for students.

Understanding the Midcarpal and Carpometacarpal Joints

Overview of the Midcarpal Joint

• The midcarpal joint connects the upper row of carpal bones with the lower row, known as a joint in anatomy.

• It is divided into two inter-articular lines: external (lateral) and internal (medial), which help classify the type of joint.

• The external line involves articulation between scaphoid, trapezium, and trapezoid; it is classified as an arthrodia due to flat facets.

• The internal line includes scaphoid, lunate, piriformis from the upper row articulating with capitate and hamate from the lower row, forming a condylar cavity.

• This condylar joint allows flexion, extension, abduction, and adduction movements.

Ligaments Associated with Midcarpal Joint

• Key ligaments include an external lateral ligament connecting scaphoid to trapezium and a lateral ligament linking piriformis to hamate.

• Palmar view shows additional ligaments reinforcing midcarpal joints; one connects trapezium below to scaphoid above.

• Dorsal ligaments also connect various carpal bones within both inter-articular lines.

Transition to Carpometacarpal Joints

• The carpometacarpal joints connect carpal bones with metacarpals; they often share synovial cavities with midcarpal joints for fluid movement.

• These joints are categorized into two groups; notably, the first carpometacarpal joint (trapeziometacarpal joint or thumb joint).

Unique Features of Thumb Joint

• The thumb's carpometacarpal joint is saddle-type or reciprocal socket joint allowing extensive movement including opposition.

• This unique structure enables flexion/extension and abduction/adduction movements that are not possible in other fingers.

Structure of Other Carpometacarpal Joints

• Second metacarpal fits into a mortise formed by trapezium, trapezoid, and capitate allowing limited movement compared to thumb.

• Third through fifth metacarpals articulate primarily with capitate or hamate; these joints are arthrodia allowing sliding movements.

Understanding the Hand's Anatomy

Overview of Metacarpal and Intermetacarpal Joints

• The thumb has a unique joint capsule that acts as a protective muff, distinguishing it from other fingers.

• Intermetacarpal joints exist between metacarpals, with ligaments connecting the second to fifth metacarpals, allowing for articulation.

• Interosseous metacarpal ligaments are crucial for stability; palmar and dorsal metacarpal ligaments reinforce these joints but are absent in the thumb.

Metacarpophalangeal Joints

• The transition from metacarpals to phalanges forms the metacarpophalangeal joints, which are classified as condylar joints.

• These joints allow biaxial movements: flexion/extension and abduction/adduction, essential for finger mobility.

• Lateral ligaments provide reinforcement; each joint has external and internal lateral ligaments for added stability.

Sesamoid Bones and Their Function

• Sesamoid bones located in the first metacarpophalangeal joint can vary among individuals but serve important muscular attachment functions.

Interphalangeal Joints Structure

• Interphalangeal joints are categorized as hinge or trochlear type joints, primarily allowing flexion and extension movements.

• They consist of proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints; the first finger only has one interphalangeal joint due to its structure.

Reinforcement of Interphalangeal Joints

• Similar to metacarpophalangeal joints, interphalangeal joints have external and internal lateral ligaments providing structural support.