The annular ligament binds the head of the radius to the radial notch of the ulna, preventing any separation of the two bones laterally. Therefore, the humeroradial joint is not functionally a ball and socket joint, although the joint surface in itself allows movement in all directions.
The annular ligament secures the head of the radius from dislocation, which would otherwise tend to occur, from the shallowness of the cup-like surface on the head of the radius. Without this ligament, the tendon of the biceps brachii would be liable to pull the head of the radius out of the joint.
The head of the radius is not in complete contact with the capitulum of the humerus in all positions of the joint.
The capitulum occupies only the anterior and inferior surfaces of the lower end of the humerus, so that in complete extension a part of the radial head can be plainly felt projecting at the back of the joint.
In full flexion the movement of the radial head is hampered by the compression of the surrounding soft parts, so that the freest rotatory movement of the radius on the humerus (pronation and supination) takes place in semiflexion, in which position the two articular surfaces are in most intimate contact.
Flexion and extension of the elbow-joint are limited by the tension of the structures on the front and back of the joint; the limitation of flexion is also aided by the soft structures of the arm and forearm coming into contact.
A subluxation of the humeroradial joint is called a "nursemaid's elbow", also known as radial head subluxation.[1] It is generally caused by a sudden pull on the extended pronated forearm, such as by an adult tugging on an uncooperative child or by swinging the child by the arms during play.
In radial head subluxation, there is little complaint of pain, and the person generally reports pain in the proximal forearm. The mechanism is slippage of the head of the radius under the annular ligament. The distal attachment of the annular ligament covering the radial head is weaker in children than in adults, allowing it to be more easily torn. The older child will usually point to the dorsal aspect of the proximal forearm when asked where it hurts. This may mislead one to suspect a buckle fracture of the proximal radius.[2] There is no tear in the soft tissue (probably due to the pliability of young connective tissues).[2]
Dislocationedit
A radial head dislocation is mainly caused by trauma, or by a congenital state. The traumatic form is usually seen in infancy and childhood as an isolated injury.[3]
The radiocapitellar line is used in the detection of radial head dislocation on lateral X-rays. It normally goes through the capitulum of the humerus.[4]
Abnormally pointed radiocapitellar line, indicating radial head dislocation.[4]
Additional imagesedit
Capsule of elbow-joint (distended) seen from front
Capsule of elbow-joint (distended) seen from back
Left elbow-joint showing anterior and ulnar collateral ligaments
Left elbow-joint showing posterior and radial collateral ligaments
This article incorporates text in the public domain from page 321 of the 20th edition ofGray's Anatomy(1918)
^Toupin, P; Osmond, M. H.; Correll, R; Plint, A (2007). "Radial head subluxation: How long do children wait in the emergency department before reduction?". CJEM. 9 (5): 333–7. PMID 17935648.
^Dr Jeremy Jones and A.Prof Frank Gaillard. "Radial head dislocation". Radiopaedia. Retrieved 2017-10-20.
^ abKilborn, Tracy; Moodley, Halvani; Mears, Stewart (2015). "Elbow your way into reporting paediatric elbow fractures – A simple approach". South African Journal of Radiology. 19 (2). doi:10.4102/sajr.v19i2.881. ISSN 2078-6778.
External linksedit
Wikimedia Commons has media related to Humeroradial joints.
Anatomy photo:10:st-1106 at the SUNY Downstate Medical Center - "Joints of the Upper Extremity: Elbow joint"
humeroradial, joint, humeroradial, joint, joint, between, head, radius, capitulum, humerus, limited, ball, socket, joint, hinge, type, synovial, joint, left, elbow, joint, showing, anterior, ulnar, collateral, ligamentsdetailsidentifierslatinarticulatio, humer. The humeroradial joint is the joint between the head of the radius and the capitulum of the humerus is a limited ball and socket joint hinge type of synovial joint Humeroradial jointLeft elbow joint showing anterior and ulnar collateral ligamentsDetailsIdentifiersLatinarticulatio humeroradialisTA98A03 5 09 003TA21774FMA38855Anatomical terminology edit on Wikidata Contents 1 Structure 2 Clinical significance 2 1 Subluxation 2 2 Dislocation 3 Additional images 4 See also 5 References 6 External linksStructure editThe annular ligament binds the head of the radius to the radial notch of the ulna preventing any separation of the two bones laterally Therefore the humeroradial joint is not functionally a ball and socket joint although the joint surface in itself allows movement in all directions The annular ligament secures the head of the radius from dislocation which would otherwise tend to occur from the shallowness of the cup like surface on the head of the radius Without this ligament the tendon of the biceps brachii would be liable to pull the head of the radius out of the joint The head of the radius is not in complete contact with the capitulum of the humerus in all positions of the joint The capitulum occupies only the anterior and inferior surfaces of the lower end of the humerus so that in complete extension a part of the radial head can be plainly felt projecting at the back of the joint In full flexion the movement of the radial head is hampered by the compression of the surrounding soft parts so that the freest rotatory movement of the radius on the humerus pronation and supination takes place in semiflexion in which position the two articular surfaces are in most intimate contact Flexion and extension of the elbow joint are limited by the tension of the structures on the front and back of the joint the limitation of flexion is also aided by the soft structures of the arm and forearm coming into contact Clinical significance editSubluxation edit Further information Nursemaid s elbow A subluxation of the humeroradial joint is called a nursemaid s elbow also known as radial head subluxation 1 It is generally caused by a sudden pull on the extended pronated forearm such as by an adult tugging on an uncooperative child or by swinging the child by the arms during play In radial head subluxation there is little complaint of pain and the person generally reports pain in the proximal forearm The mechanism is slippage of the head of the radius under the annular ligament The distal attachment of the annular ligament covering the radial head is weaker in children than in adults allowing it to be more easily torn The older child will usually point to the dorsal aspect of the proximal forearm when asked where it hurts This may mislead one to suspect a buckle fracture of the proximal radius 2 There is no tear in the soft tissue probably due to the pliability of young connective tissues 2 Dislocation edit A radial head dislocation is mainly caused by trauma or by a congenital state The traumatic form is usually seen in infancy and childhood as an isolated injury 3 nbsp The radiocapitellar line is used in the detection of radial head dislocation on lateral X rays It normally goes through the capitulum of the humerus 4 nbsp Abnormally pointed radiocapitellar line indicating radial head dislocation 4 Additional images edit nbsp Capsule of elbow joint distended seen from front nbsp Capsule of elbow joint distended seen from back nbsp Left elbow joint showing anterior and ulnar collateral ligaments nbsp Left elbow joint showing posterior and radial collateral ligamentsSee also editElbow Humeroulnar jointReferences edit nbsp This article incorporates text in the public domain from page 321 of the 20th edition of Gray s Anatomy 1918 Toupin P Osmond M H Correll R Plint A 2007 Radial head subluxation How long do children wait in the emergency department before reduction CJEM 9 5 333 7 PMID 17935648 a b Nursemaid Elbow at eMedicine Dr Jeremy Jones and A Prof Frank Gaillard Radial head dislocation Radiopaedia Retrieved 2017 10 20 a b Kilborn Tracy Moodley Halvani Mears Stewart 2015 Elbow your way into reporting paediatric elbow fractures A simple approach South African Journal of Radiology 19 2 doi 10 4102 sajr v19i2 881 ISSN 2078 6778 External links edit nbsp Wikimedia Commons has media related to Humeroradial joints Anatomy photo 10 st 1106 at the SUNY Downstate Medical Center Joints of the Upper Extremity Elbow joint Portal nbsp Anatomy Retrieved from https en wikipedia org w index php title Humeroradial joint amp oldid 1206228025, wikipedia, wiki, book, books, library,
