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Dr Patrick HOUVET/F.I.H.S
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What is Ulnar Impaction Syndrome (UIS) ?

Ulnar Impaction Syndrome( or " syndrome du cubitus long" for French spoken people) is a positive ulnar variance, that is, that the cubitus is too long regarding the radius.

UIS may be congenital or acquired.
This median is measured by posterioanterior radiographs under various methodologies :

The lower radio-cubital median is given by the distance of the radial point measured on the perpendicular passing over the radial point in the cubital line.
The lower radio-cubital median or ulnar variance is neutral when its values are around 2 mm. It is positive when the radial point is above the cubital line.
Along life, the ulna tends to "depression" caused by forces, and the distal radial ulnar median settles with time. Finally, the cubitus is long in the congenital malformations such as the Madelung's disease.

The form of the lower extremity of the ulnar is variable :

the convexity of the lower extremity may be prominent and susceptible to causing conflicts with the carpal when developing a long ulna provided the distal radio-ulnar median is normal.

the ulnar sytloid may be very long and touch upon the triquetrum, causing potential conflict. Sometimes the ulnar styloid is non existent.

These elements have their own pathologies, similar to those of the UIS. Most often, 80% of the forces from the radius to the carpal pass through the radial-carpal compartment. The longer the cubitus, the more forces travel through the ulno-carpal compartment, causing internal hyperpressure of the carpal.
Post-traumatic lesions are variable :
triangular ligament dislocations, distal or proximal ulnar styloid fracture, ulnar fracture, ulnar luxation or subluxation, which modify the pressure on the carpal. The most common result of fractures of the radius is the long ulna, with its secondary pathology :
most frequent pains after fracture of radius occur in the internal compartment of this joint.
Pre-existent degenerative lesions and traumatic lesions may also occur.

Prono-supination repetitive motion may cause :

degeneration of the central avascular part of the triangular ligament, with fairly broad perforation.
cartilage wear and tear connected first to the lunatum and then to the triquetum, with full separation of the cubito-carpal interline elements.

What are the symptoms ?

Clinical symptoms involve prono-supination pains. Reduction of motion and strength may occur at ulnar flexion of the wrist.

Which complimentary examinations are helpful ?

Sometimes plain radiographs are normal, except for results of distal radius fracture. It is important to have postanterior views of the forearm to determine if the radius and the ulnar are parallel. Subluxation of the ulnar, usually posterior, will be observed, as this may be the cause for painful complication after most of the treatment methodologies of a long ulna.

        

Both arthroscanner and arthroscopy allow precise diagnosis of the lesions (ulnar abutment syndrome).

Lesions observed involve perforations, usually central and degenerative of the triangular ligament, cartilage erosions of the proximal cup of the semilunate and the triquetal.

Ulno-carpal and secondly distal ulno-carpal arthrosis is the cause of pain. These have been ignored for long due to standard radiographs.


How is it treated ?


Procedures that keep the distal radial-ulnar joints :

The treatment involves ulnar shortening :
There are various techniques : ulnar section above the distal extremity of the bone, and plaque fixation, preferably through compression, as these osteotomies do not fix easily. For other progressive osteotomies, resection of two small osseous fragments is performed.


Ulnar shortening is indicated each time the distal radial-ulnar is well positioned (rounded), congruent and non arthrosic.
Osteotomy will be directional, that is with oblique resection at the anterior base if the ulnar is subluxed on the back side.


It is sometimes difficult to establish congruity of this joint, at this level secondary arthrosis may develop.

The Wafer's procedure, which actually is the resection of the ulnar distal cup may be performed either surgically or through arthroscopy. Despite the apparent benignancy of the surgical procedure, the postoperative period usually lasts long, maybe because this is an intra-articular operation
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Procedures that resect the distal radial-ulnar joint :

The oldest procedure was introduced by Darrach. It consists in suppressing 12 mm of the distal ulnar part. This resection should be accompanied by an arthroplasty and a stabilisation of the remaining ulnar diaphysis. Fibrous interposition, capsule closure and readjustment of the ECU tendon should be part of the procedure, which is not a plain osseous excision.

Variations of the Darrach procedure are Bowers and Watson's : the former is through oblique resection of the bone, and the latter resection of the diaphysis over a very long oblique bone.

The Sauvé-Kapandji procedure is a distal radial-ulnar arthrodesis accompanied by resection of the osseous cylinder proximal to the joint. Prono-supination is performed in this space created upstream to the arthrodesis.

All the procedures achieve decomposition of the carpal, most of the forces are transmitted through the radio carpal and pain disappears. Results in terms of prono-supination vary.


Which are the specific risks ?

In any procedure that involves resection of the distal ulnar extremity pathology of the ulnar stump may occur, above all if protrudring on the back side: this causes pain and a tendon protrudring when at prono-supination.
Progressive approximation of the two diaphysis which are in contact and cause pain at pronosupination. Stabilisation of this stump may be performed in the first procedure or afterwards.
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