Radius and ulna

Question 1

How much of the proximal thoracic limb weight bearing forces is carried by the proximal radial articular surface at the level of the elbow?

Answer 1

51%

Question 2

At what level doe the interosseous ligament terminate?

Answer 2

Midshaft of the antebrachium

Question 3

How much ulnar growth is the distal ulnar physis responsible for?

Answer 3

100%. The proximal physis is only responsible for elongation of the olecranon.

Physeal closure occurs around 250 days.

Question 4

How much do the proximal and distal radial physes contribute to growth?

Answer 4

Approximately 50/50

Question 5

Describe the bony anatomy of the radius and ulna

Answer 5

Question 6

Describe the important ligamentous structures of the elbow

Answer 6

Question 7

What is the normal angle of procurvatum for the radius?

Answer 7

27 degrees

Question 8

How do you calculate procurvatum of the radius?

Answer 8

⦰ + (90 - aCdPRA) + (90 = aCdDRA)

Question 9

What are the normal joint orientation angles for the canine radial anatomic axes?

Answer 9

Question 10

What is the cause of radial shortening?

Answer 10

Symmetric insult to the distal radial physis. The proximal radial physis assumes the majority of the longitudinal growth but compensatory mechanisms are unable to keep-up, resulting in shortening.

Question 11

What degree of radial shortening can be detected on radiographs and CT respectively?

Answer 11

Radiographs: 1.5 - 4mm
CT: 1mm
Arthroscopy may be better than both of these modalities for assessment of radial shortening.

Question 12

What are surgical options for radial lengthening in the juvenile patient?

Answer 12

Dynamic elongation generally preferred as it allows some adjustability as the dog continues to grow (distraction osteogenesis).

Can include:
1. Transverse osteotomy and placement of pins in the proximal radius and distal humerus with elastic material to apply traction force (semi-controlled).
2. ESF with threaded connecting bar (Stader apparatus).
3. Circular external fixator.

Lengthening of up to 50% of original radial length has been achieved.

Question 13

What are surgical options for radial lengthening in the adult patient?

Answer 13

Either dynamic or acute (typically reserved for less severe discrepancies) elongation techniques can be considered.

Acute elongation techniques include:

1. Osteotomy and stabilization. 2. Sagittal sliding osteotomy (benefit of preserving load sharing).

Question 14

How is adequate positioning of the radial head determined following acute osteotomy correction (too short radius) in adult dogs?

Answer 14

Radiography or arthroscopy (ideal).

Question 15

What is the alternative to radial lengthening techniques for treatment of short radius?

Answer 15

Shortening of the ulnar by ulnar ostectomy. May be preferable in adult patients as juvenile patients may heal prior to cessation of ulnar growth.

Question 16

What is postulated to be the reason for the frequent injury of the distal ulnar physis?

Answer 16

Conical shape converts loading in any direction to compressive injury

Question 17

What changes are frequently seen in the radius following premature closure of the distal ulnar physis?

Answer 17

Shortening, procurvatum, distal valgus, torsion.

Can also result in humeroulnar incongruity.

Question 18

What can cause pure shortening of the ulna without closure of the distal physis and radial angulation?

Answer 18

Any condition that results in radioulnar synostosis.

Question 19

In an immature patient with premature closure of the distal ulnar physis is an ulnar osteotomy or ostectomy procedure preferred?

Answer 19

Ostectomy, as it helps to prevent closure prior to cessation of radial growth.

Question 20

What are the methods to prevent craniocaudal tipping of a proximal ulnar ostectomy?

Answer 20

Intramedullary pinning, bioblique osteotomy (proximocaudal-distocranial)

Question 21

What is the benefit of a distal over proximal ulnar ostectomy for treatment of premature closure of the distal ulnar physis in immature dogs?

Answer 21

Distal location prevents tipping of the ulnar with pull of the triceps due to stabilization by the intraosseous ligament. Comparative efficacy of low versus high ulnar ostectomies remains unknown, however.

Question 22

List 3 methods to prevent premature closure of a distal ulnar ostectomy for treatment of premature closure of the distal ulnar physis in immature dogs?

Answer 22

1. Creation of an ostectomy gap 1.5 times the diameter of bone (Key’s hypothesis).
2. Removal of all periosteum in the vicinity of the ostectomy.
3. Insertion of a fat graft.

Question 23

Aside from ulnar ostectomy, what are some other methods of ulnar lengthening that have been described for premature closure of the distal ulnar physis?

Answer 23

Semi-controlled or controlled distraction systems using elastic bands or ESF, stapling of the distal radius physis, ulnar styloid transposition with ostectomy of the distal ulna.

Question 24

In a mature patient what options exist for surgical correction of the shortened ulnar in premature closure of the distal ulnar physis?

Answer 24

Dynamic ulnar osteotomy procedures (controlled, semi-controlled) or acute one-stage static lengthening techniques (distraction and plating, sagittal sliding osteotomy).

Question 25

In juvenile patients, when might ulnar ostectomy for premature closure of the distal ulnar physis be appropriate without concurrent radial angular limb correction?

Answer 25

In cases when radial angulation is not severe. If radial angulation is severe, or there is abnormal angulation (varus, recurvatum, internal rotation) then radial corrective measures are necessary. In this latter instance concurrent damage of the distal radial physis is likely.

Question 26

When correcting radial angular limb deformities, torsion in excess of ___ degrees results in radiographic miscalculation greater than 5 degrees in the frontal plane?

Answer 26

15. In this instance CT is required for surgical planning.

Question 27

What is the imaging diagnosis in this 5-month old English Bulldog?

Answer 27

Type 1 congenital (humeroradial) luxation of the elbow.

Question 28

What is the difference between partially compensated and noncompensated biapical deformities?

Answer 28

Partially compensated biapical deformities are those in which the planes of the proximal and distal CORAs are in opposite directions. Noncompensated are when they are in the same direction.

Question 29

In chondrodystrophic dogs what percentage of antebrachial deformities are biapical?

Answer 29

80%

Question 30

What are multiapical deformities?

Answer 30

Deformities that possess more than two CORAs.

Question 31

The integrity of what should be assessed prior to surgical correction of antebrachial angular limb deformity?

Answer 31

The carpus via palpation or stress radiography.

Question 32

What are some surgical fixation methods described for antebrachial angular limb correction?

Answer 32

Internal fixation with bone plates, ESF (linear, circular, hybrid linear-circular).

Question 33

What type of osteotomies can be performed for antebrachial angular limb correction.

Answer 33

Closing wedge, opening wedge, radial, cylindrical, dome. Radial and cylindrical osteotomies are not able to correct torsional deformities as they only allow correction around a single axis of rotation.

Question 34

Which of Paley's osteotomy rules can be applied to allow fixation if the antebrachial angular deformity is very close to the joint?

Answer 34

Paley's second law. This allows osteotomy proximal to the CORA. Results in translation of the two segments to maintain alignment.

Question 35

Is a proximal radial varus deformity corrected with a medial or lateral closing wedge osteotomy?

Answer 35

Lateral closing wedge

Question 36

What are prognostic indicators for determining functional outcome following antebrachial angular limb deformity correction?

Answer 36

Severity of preexisting elbow osteoarthritis and more severe functional impairment were negative prognostic indicators. Dogs with biapical deformities are more likely to possess joint deformities.

Question 37

How are Salter Harris fractures of the proximal or distal radial physes typically repaired?

Answer 37

Cross-pinning. Repair of the distal physis should be protected by a caudal splint for 1-2 weeks due to the long lever arm acting at this location.

Question 38

What is a repair technique for proximal comminuted radial fractures in which there is inadequate proximal radial bone stock for implant placement.

Answer 38

Stabilization of the proximal ulna to the distal radius

Question 39

What are the benefits of cranial and medial plating of the radius?

Answer 39

Cranial: tension surface of the bone. Medial: ease of application and less interference with the tendons of the extensor muscles.

Question 40

Why is the use of a type 1b ESF particularly advantageous in the radius?

Answer 40

Will allow for placement of transfixation pins from both a craniomedial and craniolateral direction utilizing a larger bone surface area for pin placement (compared to craniocaudal), and using two soft tissue corridors with minimal soft tissue/bone interference.

Question 41

What is the benefit of repairing diaphyseal fractures of the radius with a type Ib ESF?

Answer 41

Can simultaneously use a craniolateral and craniomedial corridor for pin placement. These corridors have relatively minimal soft tissue coverage and a larger bone surface area for pin placement as compared to placement in a purely medial-to-lateral direction.

Question 42

What is repair technique is shown?

Answer 42

Question 43

What structures can be sacrificed during distal repair of the radius/ulna?

Answer 43

The tendon of the abductor pollicis longus and cephalic vein.

Question 44

How can avulsion injuries of the radial styloid process be repaired?

Answer 44

Pin and TBW or lag screws. Caused as a result of avulsion injury at the site of medial collateral ligament attachment. If an articular fracture is non-repairable, a pancarpal arthodesis may be performed.

Question 45

What is responsible for the delayed healing response often seen in toy-breed dogs with fractures of the distal radius?

Answer 45

Decreased vascular density at the distal diaphyseal-metaphyseal junction. The radii of small breed dogs are also more susceptible to fracture than large breed dogs when loaded proportionally.

Question 46

What percentage of fractured radii in toy breed dogs result in malalignment or nonunion when treated conservatively?

Answer 46

83% (whereas successful return to function has been reported with bone plating in 70 - 85% of patients)

Question 47

What might be the underlying cause of osteopenia if observed on radiographs following distal radius/ulna fracture repair in a toy breed patient?

Answer 47

Stress protection. Staged destabilization could be considered.

Question 48

What are two methods that a fracture of the olecranon can be repaired?

Answer 48

Pin and TBW, plating (should be used for articular fractures below the midpoint of the trochlea notch to ensure more accurate reduction).

Question 49

When plating an olecranon fracture what is the tension surface of the bone?

Answer 49

Caudal. However the soft tissue coverage over this area is limited and may predispose to injury.

Question 50

What are the 4 classifications of Monteggia fractures?

Answer 50

Classified according to the direction of radial head luxation and angulation of the ulna fracture. Type 1: cranial radial head luxation and cranioproximal angulation of the ulna fracture. Type 2: caudal radial head luxation and caudal angulation of the ulna fracture. Type 3: lateral radial head luxation. Type 4: proximal fracture of the radius and ulna with cranial luxation of the radial head.

Question 51

Ulnar fractures below which level inevitably result in disruption to the radioulnar joint and annular ligament?

Answer 51

Below the medial coronoid processes. Proximal ulna fractures may be associated with luxation of the radial head but intact radioulnar articulation.

Question 52

Describe the surgical repair options for Monteggia fractures and how these might differ dependent on disruption of the radioulnar articulation

Answer 52

Intact radioulnar articulation: closed reduction of the luxation and pinning of the ulnar may be possible. Ulnar plating may provide additional stability if required. Disrupted radioulnar articulation: additional stabilization of the radioulnar articulation required following reduction using ulnar radial screws (primary repair of annular ligament is unfeasible in most cases).

Question 53

Placement of ulnar to radial screws in a Monteggia fracture has more significant side-effects in cats or dogs?

Answer 53

Cats, as it limits pronation and supination. Screws should be removed 4-6 weeks following repair.

Question 54

How are fractures of the ulna styloid process repaired?

Answer 54

Pin and TBW.

Question 55

In a study by Senn 2024 in Vet Surg, what was the effect of a radioulnar screw in the proximal, middle or distal radial diaphysis on supination and pronation in cats?

Answer 55

Ability to supinate and pronate reduced by 2/3 regardless of screw location.

Question 56

In a study by Duncan 2023 in JAVMA, which two radial joint orientation angles were significantly different in small breed dogs as compared to large or medium breed dogs?

Answer 56

The aCrPRA and aCdDRA

Question 57

In a study by Muroi 2021 in VCOT, what was the effect of bone plating on radial and ulna density in toy breed dogs (as defined by ratio of pixel values on radiographs)? Was this influenced by age?

Answer 57

Bone density decreased regardless of whether locking or cortical screws were used. Reductions in bone density persisted at 12-months post-operatively in dogs >6 months. In dogs <6 months reductions in density had resolved by 3 months. Removal of the implant led to recovery of bone density in all cases.

Question 58

In a study by Makar 2024 in JFMS, was dual bone fixation of both the radius and ulna associated with an increased chance of successful outcome in cats with antebrachial fracture?

Answer 58

No - 14 x less likely to have a successful outcome as compared to single plate fixation. Also 9 times less likely to have a successful outcome as assessed by owners.