THE DISTAL RADIO-ULNAR JOINT

The forearm comprises of two bones: - Radius - Ulnar The radius and ulna are joined to each other at 2 places: - The superior(or proximal) radio-ulnar joint - The inferior(or distal) radio-ulnar joint They are also connected in the middle, by the interosseous membrane.

Pronation and Supination Rotatory movements of the forearm around a vertical axis. The vertical axis passes through the centre of the head of the radius above, and through the ulnar attachment of the articular disc below. However, axis is not stationary. It is displaced laterally in pronation and medially in supination.

Muscles causing these movements:- PRONATION : -chiefly brought about by pronator quadratus - aided by pronator teres when the movt is rapid and against resistance - gravity also helps SUPINATION : - brought about by supinator and biceps brachii. - Slow supination(with elbow extended) : done by the supinator - Rapid supination (with elbow flexed) and against resistance : mainly by the biceps

FRACTURES The radius and ulna are commonly fractured together. Sometimes, there might be a fracture of either of the bones without much displacement. Displacements :common in adults. a) Angulation – commonly medial and anterior b) Shift – in any direction c) Rotation – proximal/distal fragments maybe pronated/supinated

ISOLATED FRACTURES:- A) Of Radius: - in the lower fourth region - commonly occurs in children due to a fall - a green-stick fracture Rx:- Below-elbow plaster cast for 3weeks B) Of Ulna: - occurs in adults following a direct blow Rx:- Above-elbow plaster cast for 6weeks Displaced fractures may need open reduction and internal fixation

Fractures at and near the distal radio-ulnar joint 1) GALEAZZI FRACTURE -fracture of the lower third of the radius with dislocation or subluxation of the distal radio-ulnar joint. -commonly results from a fall on an outstretched hand. Displacement : - the radius fracture is angulated medially and anteriorly. - the distal radio-ulnar joint is disrupted, resulting in dorsal dislocation of the distal end of the ulna

Rx :- - Closed reduction rarely succeeds(except in children) -Treatment of choice is ORIF with plates and screws - Post-op above-elbow plaster cast for 4-6weeks Complications :- -Mal union( because of displacement of fragment) - deformity and limitation of pronation and supination

2) COLLES’ FRACTURE This is a fracture at the distal end of the radius, at its cortico-cancellous junction, in adults with typical displacement. Commonest fracture >40yrs, particularly common in women because of postmenopausal Osteoporosis Nearly always results from a fall on an outstretched hand. Patho-Anatomy:- - fracture line runs transversely - one or more of the following displacements are seen : 1)Impaction of fragments 2)Dorsal displacement 3)Dorsal tilt 4)Lateral displacement 5)Lateral tilt 6)Supination

Injuries commonly associated with Colle’s fracture :- 1) Fracture of the styloid process of ulna 2)Rupture of the ulnar collateral ligament 3)Rupture of the triangular cartilage of the ulna 4)Rupture of the interosseous radio-ulnar ligament, producing radio-ulnar subluxation. Clinical presentation :- - Classic ‘ dinner-fork deformity’ - the radial styloid process comes to lie at the same level or a little higher than the ulnar styloid process - Dorsal tilt is the most characteristic displacement

Rx:- - For undisplaced : immobilization in a below-elbow cast for 6 weeks is sufficient. - For displaced : manipulative reduction followed by immobilization in Colles’ cast. - In comminuted fractures : incidence of redisplacement is high therefore these are sometimes transfixed percutaneously using two K-wires which are incorporated into the plaster cast. In some cases, external fixator maybe used. Complications:- 1)Stiffness of joints 2)Mal-union 3)Subluxation of the inf radioulnar jt 4)Carpal-tunnel syndrome 5)Sudeck’s Osteodystrophy 6) Rupture of the EPL tendon

SMITH’S FRACTURE Its an uncommon fracture seen in adults and old people. Reverse of Colles’ fracture – occurs at the same site but the distal fragment displaces ventrally and tilts ventrally Rx:- -Closed reduction and above-elbow plaster cast immobilization for 4-6weeks with elbow in flexion and forearm in full supination. - ORIF by buttress plate and screws if closed reduction fails

BARTON’S FRACTURE It is an intra-articular fracture of the lower end of radius, with the fracture line running obliquely from the distal articular surface of the radius to either its anterior or posterior cortices. Accordingly, there is a Volar Barton’s fracture (anterior marginal type) and a Dorsal Barton’s fracture(posterior marginal type) Rx:- 1) Closed manipulation followed by an above elbow plaster cast for 4-6 weeks. 2) ORIF if closed reduction fails or in case of redisplacement.