ULNAR VARIANCE

Question 1

Normal ulnar variance

Answer 1

1mm negative per Symes or < 1mm per Orthobullets

Question 2

Effect of ulnar variance on load transmission through the wrist

Answer 2

Normal = 80% through distal radius, 20% through distal ulna

2. 5mm positive = 60% through distal radius, 40% through distal ulna (so 100% increase through distal ulna)
3. 5mm negative = 95% through distal radius, 5% through distal ulna

Question 3

Aetiology of positive ulnar variance

Answer 3

Congenital vs. acquired
Congenital = Madelung's deformity
Acquired
1. Traumatic 
- Distal radial physeal injury and premature arrest
- Distal radius fracture and malunion 
- DRUJ injury = Essex-Lopresti injury
2. Iatrogenic
- Joint levelling procedure = radial shortening osteotomy
- Radial head excision 
3. RA

Question 4

Aetiology of negative ulnar variance

Answer 4

Congenital vs. acquired
Congenital = reverse Madelung’s deformity
Acquired
1. Traumatic
- Distal ulna physeal injury and premature arrest
- Distal ulna fracture and malunion
- DRUJ injury = Galeazzi injury
2. Iatrogenic
- Joint levelling procedure = ulnar shortening osteotomy

Question 5

Best radiograph to assess ulnar variance

Answer 5

PA wrist xray in 90-90 position with forearm in neutral rotation
Draw line along articular surface of ulnar head perpendicular to long axis of ulna
Draw line along articular surface of lunate fossa perpendicular to long axis of radius
Difference between them is the UV
** MRI is not useful to quantify UV as the position of the wrist is not consistent **

Question 6

Special view to assess ulnar variance

Answer 6

Pronated grip PA view = increases apparent ulnar variance

Other option is contralateral comparison view

Question 7

Effect of following variables on ulnar variance:
Age
Gender 
Forearm rotation
Grip

Answer 7

1. Age = UV increases with age
2. Gender = UV is more negative in males
3. Rotation = pronation increases UV, supination decreases UV
4. Grip = making a fist increases UV

Question 8

5 associations with positive ulnar variance

Answer 8

1. Ulnocarpal abutment syndrome
2. TFCC tears
3. LT ligament tears
4. Scapholunate dissociation (SLD)
5. Arthrosis = ulnar head/ lunate/ triquetrum

Question 9

2 associations with negative ulnar variance

Answer 9

1. Kienbock’s Disease

2. Ulnar impingement syndrome = impingement between the ulna and radius proximal to the sigmoid notch