Transcript of "Monteggia fracture dislocation of the ulna"
MONTEGGIA FRACTURE-DISLOCATION OF THE ULNA Dr. D. N. Bid
• The injury described by Monteggia in the early nine-teenth century (without benefit of x-rays!) was a fracture of the shaft of the ulna associated with dislocation of the proximal radio-ulnar joint; the radio-capitellar joint is inevitably dislocated or subluxated as well.
• More recently the definition has been extended to embrace almost any fracture of the ulna associated with dislocation of the radio-capitellar joint, including trans-olecranon fractures in which the proximal radio-ulnar joint remains intact.
• If the ulnar shaft fracture is angulated with the apex anterior (the commonest type) then the radial head is displaced anteriorly; if the fracture apex is posterior, the radial dislocation is posterior; and if the fracture apex is lateral then the radial head will be laterally displaced.• In children, the ulnar injury may be an incomplete fracture (greenstick or plastic deformation of the shaft).
Mechanism of injury• Usually the cause is a fall on the hand; if at the moment of impact the body is twisting, its momentum may forcibly pronate the forearm.• The radial head usually dislocates forwards and the upper third of the ulna fractures and bows forwards.• Sometimes the causal force is hyperextension.
Clinical features• The ulnar deformity is usually obvious but the dislocated head of radius is masked by swelling.• A useful clue is pain and tenderness on the lateral side of the elbow.• The wrist and hand should be examined for signs of injury to the radial nerve.
• X-ray With isolated fractures of the ulna, it is essential to obtain a true anteroposterior and true lateral view of the elbow.• In the usual case, the head of the radius (which normally points directly to the capitulum) is dislocated forwards, and there is a fracture of the upper third of the ulna with forward bowing.
• Backward or lateral bowing of the ulna (which is much less common) is likely to be associated with, respectively, posterior or lateral displacement of the radial head.• Trans-olecranon fractures, also, are often associated with radial head dislocation.
Treatment• The key to successful treatment is to restore the length of the fractured ulna; only then can the dislocated joint be fully reduced and remain stable.• In adults, this means an operation through a posterior approach.• The ulnar fracture must be accurately reduced, with the bone restored to full length, and then fixed with a plate and screws; bone grafts may be added for safety.
• The radial head usually reduces once the ulna has been fixed.• Stability must be tested through a full range of ﬂexion and extension.• If the radial head does not reduce, or is not stable, open reduction should be performed.• If the elbow is completely stable, then ﬂexion-extension and rotation can be started after very soon after surgery.• If there is doubt, then the arm should be immobilized in plaster with the elbow ﬂexed for 6 weeks.
Complications• Nerve injury – Nerve injuries can be caused by over-enthusiastic manipulation of the radial dislocation or during the surgical exposure. – Always check for nerve function after treatment. The lesion is usually a neurapraxia, which will recover by itself.
• Malunion – Unless the ulna has been perfectly reduced, the radial head remains dislocated and limits elbow ﬂexion. – In children, no treatment is advised. – In adults, osteotomy of the ulna or perhaps excision of the radial head may be needed.• Non-union – Non-union of the ulna should be treated by plating and bone grafting.
Special features in children• The general features of Monteggia fracture- dislocations are similar to those in adults.• However, it is important to remember that the ulnar fracture may be incomplete (greenstick or plastic deformation); if this is not detected, and corrected, the child may end up with chronic subluxation of the radial head.
• Because of incomplete ossification of the radial head and capitellar epiphysis in children, these landmarks may not be easily defined on x- ray and a proximal dislocation could be missed.• The x-rays should be studied very carefully and if there is any doubt, x-rays should be taken of the other side for comparison.
• Incomplete ulnar fractures can often be reduced closed, although considerable force is needed to straighten the ulna with plastic deformation.• The position of the radial head is then checked; if it is not perfect, closed reduction can be completed by ﬂexing and supinating the elbow and pressing on the radial head.• The arm is then immobilized in a cast with the elbow in ﬂexion and supination, for 3 weeks.
• Complete fractures are best treated by open reduction and fixation using an intramedullary rod or a small plate.