Ch 54 - Radius and Ulna

Question 1

What percentage of weight at the elbow is transmitted through the radius and the ulna?

Answer 1

• Radius 51%
• Ulna 49%

Question 2

The tendons of which muscle insert on the medial side of the radius and ulna?

Answer 2

• Biceps brachii
• Brachialis

Question 3

What muscles share their origin with both the radius and the ulna in the mid-diaphysis?

Answer 3

• Pronator quadratus
• Deep digital flexor
• Abductor pollicus longus

Question 4

What is the radioulnar ligament?

Answer 4

Distal extension of the antebrachiocarpal joint capsule between the radius and ulna. Merges proximally to the interosseus ligament

Question 5

How much of the growth below the elbow is the distal ulna physis responsible for?
Proximal radial physis?

Answer 5

• Distal ulnar physis 100%
• Proximal radial physis 30-50%

Question 6

What age do the physes of the antebrachium close?

Answer 6

222-250d (in Beagles)

Question 7

What is the mean radial procurvatum of Labs?

Answer 7

26.6 degrees

Question 8

How do you calculate procurvatum?

Answer 8

On sagittal view:

Procurvatum = CORA magnitude + (90-aCdPRA) + (90-aCdDRA)

Question 9

What is the sensitivity and specificity of rads for diagnosing radioulnar incongruity?

Answer 9

• Sensitivity 78%
• Specificity 86%

Radial shortening needed to be between 1.5-4mm for a 90% sensitivty

Question 10

What is the sensitivty and specificity of arthroscopy for diagnosing radioulnar incongruity?

Answer 10

• Sensitivity 94%
• Specificity 81.9%

Question 11

What it he sensitivity, specificity and interobserver agreement for radioulnar incongruency on 3D printed models with a 1mm incongruence

Answer 11

• Sensitivity 82%
• Specificity 100%
• Interobservor agreement 87%

Question 12

How much radial lengthening has been reported with the use of an ESF and distraction osteogenesis?

Answer 12

Up to 50% of the original radial length

Question 13

What are the options for radial lengthening?

Answer 13

• Distraction osteogenesis
• Transverse osteotomy and acute correction
• Sagittal sliding osteotomy (acute correction)

Can alternatively perform ulnar ostectomy above the interosseous ligament with an IM pin. Can be left for gradual shortening or can be acutely shortened with hemicerclage

Question 14

What percentage of physeal insults is made up of distal ulnar physeal injury?
(not clear question…)

Answer 14

63%

Question 15

What are the typical changes in the radius secondary to premature closure of the distal ulnar physis?

Answer 15

• Procurvatum
• Shortening
• Distal valgus
• Torsion

Question 16

What are the surgical options for ulnar lengthening?

Answer 16

• Dynamic ulnar ostectomy/osteotomy
• Distal ulnar ostectomy
• CESF and distraction osteogenesis
• Distracted osteotomy and plating
• Sagittal sliding osteotomy

Question 17

What can be done to aid in stability of a proximal dynamic ulnar osteotomy/ostectomy?

Answer 17

• Oblique cut (proximocaudal to craniodistal)
• IM pin

Question 18

What methods can reduce the chances of permature healing of the ostectomy?

Answer 18

• Ostectomy gap greater than 1.5x diameter of the bone (Key’s hypothesis)
• Stripping of the periosteum in the vicinity
• Insertion of free fat graft into ostectomy

Question 19

What had been associated with unsuccessful outcomes after a distal ulnar ostectomy to treat ulnar shortening?

Answer 19

Radial valgus greater than 25 degrees

If varus, recurvatum or internal torsion are present then radial corrective measures will be necessary

Question 20

What is the Heuter-Volkmann law (aka Delpech’s law)?

Answer 20

Physeal growth is slowed by excessive compression and is accelerated by distraction

Question 21

What percentage of antebrachial deformities are biapical in chondrodystrophic breeds?

Answer 21

80%

Question 22

What percentage of dogs with an antebrachial deformity corrected with a CESF has improvement in function?

Answer 22

60%

Question 23

What percentage of radial deformities in an oblique plane were accurately correced using a radial or cylindrical saw?

Answer 23

44%

Question 24

A true domes osteotomy ascribes to which low of osteotomies?

Answer 24

Paley’s second rule

Question 25

What are the treatment options for congenital radial head luxation?

Answer 25

• Conservative managment
• Open surgical reduction and fixation (50% retained reduction of between 50-80%, 50% reluxated)
• Radial head ostectomy
• Arthrodesis

Question 26

What are the surgical options for proximal radial fractures?

Answer 26

• T-plate
• CESF
• Proximal ulna stabilised to the distal radius with ESF (a type Ib or Type II would be better than Ia shown in picture)

Question 27

What is the tension surface of the radius?

Answer 27

Cranial

Question 28

What percentage of r/u fracture in toy breed treated with external coaptation resulted in malalignment or nonunion?

Successful return to function with bone plate?
Complication rate?

Answer 28

Coaptation 83%

Bone plate
- Successful 70 - 85%
- Complications 54%

Question 29

What should you do if there is evidence of stress protection (osteopaenia) on rads?

Answer 29

Staged screw removal once clinical union is evident (dynamization?)
- Start with screws closest to the fracture on each side
- Waiting 3-4 weeks after removal prior to removing the next set (allows holes to fill with osteons)

Question 30

What is the tension surface of the ulna?

Answer 30

Caudal

Question 31

What are the 4 types of Monteggia fracture?

Answer 31

• Type I: Cranial luxation of the radial head with cranioproximal angulation of ulnar fracture
• Type II: Caudal luxations of the radius and caudal angulation of ulnar fracture
• Type III: Lateral luxation of the radius
• Type IV: Fracture of the proximal part of the radius and the ulna diaphysis with cranial luxation of the radial head

*If the radioulnar joint is no longer intact, will have to stabilise once radial head is reducedas annular ligament will be compromised (screw from caudal to cranial between ulna and radio)