- Discussion:
- may occur from frx (
Galeazzi fracture or
Colles frx), from
radial head frx (as a part of an
Essex Lopresti injury) or as an islated injury;
- injury to the
TFCC is a necessary part of this injury;
-
dorsal subluxation:
- dorsal dislocations are most common and result from fall on pronated hand;
- manifested by prominece of ulnar head and loss of supination;
- reduced by forearm supination;
- RU joints which cannot be closed reduced may have entrapment of the extensor tendons (ECU) - see below;
-
volar subluxation:
- occurs less often and result from forced supination;
-
diff diagnosis:
-
ECU subluxation: elicited when wrist is held in ulnar deviation and wrist is supinated;
- anatomy and stabilizing structures:
- triangular fibrocartilage complex:
- major contributor to the stability of the RU joint;
- it is difficult to imagine RU joint instability with having TFCC tear;
- ligamentous attachements: (see
ligament of the wrist)
- dorsal and palmar radioulnar
ligaments are lax except in the extremes or pronation and supination;
- palmar radioulnar ligaments (ulnolunate and ulnotriquetral) resist dorsal displacement;
- effect of pronation:
- ulna assumes a small relative negaive varience position;
- ulnar head moves dorsally;
- in pronation, the dorsal radioulnar ligament is most important in maintaining joint stability;
- effect of supination:
- ulna assumes a small relative positive varience position;
- ulnar head moves volarly;
- in supination, the palmar radioulnar ligament is most important in maintaining stability;
- Exam:
- subluxation of RU joint should be differentiated from generalized laxity by examing the contralateral wrist;
- limited & painful rotation;
- supination is block by dorsal dislocation;
- pronation is block by palmar dislocation;
-
ECU subluxation:
- is elicited when wrist is held in ulnar deviation and wrist is supinated;
- references:
-
The “Ulnar Fovea Sign” for Defining Ulnar Wrist Pain: An Analysis of Sensitivity and Specificity.
- Radiographic Diagnosis:
- suggestive features of instability:
- widening of RU joint on
AP view;
- fracture (or non union) at base of
ulnar styloid;
- significant
shortening of the radius;
- obvious dislocation on the lateral view;
- dislocation should not be diagnosed from a sinlge
lateral view, since
rotation will affect the relative position of the ulnar head;
- it is essential that the lateral view be taken w/ proper technique so that the radial styloid process overlies the proximal pole of the scaphoid, lunate, and triquetrum;
- when proper positioning is ensured, dorsal or volar subluxation is noted by the relative position of the ulna above or below the radius;
-
CT scan:
- the study of choice for instability;
- w/ suspected dorsal dislocation CT is taken w/ arm in supination;
- w/ suspected volar dislocation CT is taken w/ arm in pronation;
- CT will also reveal RU joint incongruity;
- Treatment of Dorsal Instability:
-
acute instability:
- reduction is achieved w/ supination and direct pressure;
- percutaneous pin fixation: helps maintain the reduction;
- above elbow cast for 4-6 weeks;
- ref:
An anatomic reconstruction of the distal radioulnar ligaments for posttraumatic distal radioulnar joint instability
Brian D. Adams. J Hand Surg 2002;27A:243 251.
-
chronic instability:
- non operative treatment includes forearm and elbow immobilization which limits pronation and supination;
- dorsal capsulodesis w/ either local tissue or tendon graft (using
palmaris longus)
- a radio-ulnar sling using a tendon graft is also effective;
- alternatively consider use of a distally based FCU strip or a proximally based ECU strip;
- the forearm should be held in supination for one month postop;
- ref:
Functional bracing for distal radioulnar joint instability.
- Management of Entrapped Extensor Tendons:
- entrapment of extensor tendons can occur at sites of frxs of frx of distal part of radius w/ distal RU joint involvement (
Galeazzi fracture);
- w/ entrapped extensor tendons,
distal RU joint is irreducible even after internal fixation of radial frx,
& dorsal exploration delineates interposed
ECU tendon, w/ or w/o avulsed styloid;
- at time of injury,
ECU may displace in an ulnar direction around ulnar head or directly radially into the distal radio-ulnar joint;
- open reduction of
distal RU joint, suture repair of ECU fibro- osseous canal, & internal fixation of
ulnar styloid fracture are necessary;
- references:
Irreducible fracture dislocation of the distal radioulnar joint secondary to entrapment of the ECU tendon.
DP Hanel and DK Scheid. CORR Vol 234. 1988. p 56-60.
Acute Dislocations of the Distal RU Joint. J.D. Bruckner MD, A.H. Alexander MD, and D.M. Lichtman MD. JBJS Vol 77-A No 6, June 1995.
Surgical correction of recurrent volar dislocation of the distal radioulnar joint. A case report.
Extensor carpi ulnaris and flexor carpi ulnaris tenodesis of the unstable distal ulna.
Radio-ulnar dissociation. A review of twenty cases.
Stabilization of the distal ulna by transfer of the pronator quadratus origin.
Tenodesis of the chronically unstable distal ulna.
Treatment of chronic post-traumatic dorsal subluxation of the distal ulna by hemi-resection-interposition arthroplasty.
Imbriglia JE, Matthews D. J Hand Surg. 1993; 18 (5): 899-907;
Repair of chronic subluxation of the distal radioulnar joint using FCU tendon. Tsai TM, Stillwell JH. J Hand Surg. 1984; 9 (3) 289-294.
Fractures and dislocations of the distal radioulnar joint. Buterbaugh GA, Palmer AK. Hand Clinics. 1988; 4 (3): 361-375.
Stabilizing mechanism of the distal radioulnar joint during pronation and supination. H. Kihara et al. J. Hand Surg. Vol 20-A. No 6. Nov 1995. p 931.
Stability of the Distal RU Joint: Biomechanics, Pathophysiology, Physical Dx, and Restoration of Function What We Have Learned in 25 Years
