The carpus, metacarpus and digits

Question 1

Name the bones of the carpus.

Answer 1

Question 2

Describe the dorsal ligaments of the carpus.

Answer 2

Question 3

Describe the palmar ligaments of the carpus.

Answer 3

The accessory carpal bone is attached via ligamentous attachments to the ulna carpal bone and fourth carpal bone, as well as the 4th and 5th metacarpals.

Question 4

Describe the attachments of the flexor retinaculum and palmar fibrocartilage.

Answer 4

The flexor retinaculum extends from the accessory carpal bone to the styloid process of the ulna, and distally to the intermedioradial carpal bone and first carpal bones.

The palmar fibrocartilage is attached to the intermedioradial and ulnar carpal bones, the numbered carpal bones, and proximal aspects of metacarpals III through V.

Question 5

What are the three joints of the carpus?

Answer 5

Antebrachiocarpal, middle, carpometacarpal joint.

Question 6

What are the stabilizing structures of the carpus?

Answer 6

Short extra-articular and intra-articular ligaments, an articular disc (or radioulnar ligament), palmer fibrocartilage, and joint capsule.

Question 7

How many sesamoid bones are there at the heads of the metacarpals?

Answer 7

Palmar: Eight numbered, paired sesamoids from medial to lateral. Each have medial, lateral, and cruciate ligaments attaching them to the distal metacarpal and proximal phalanx.

Dorsal: Single sesamoid bones from digits II through V.

Question 8

What are the three parts of the metacarpals?

Answer 8

From proximal to distal: base, body, head.

Question 9

What are two major anatomic differences between the canine and feline manus?

Answer 9

1. The ability to retract the claws due to the anatomy of the dorsal elastic ligaments and structural differences in the middle and distal phalanx.
2. Only a straight component in the feline medial collateral ligament of the carpus (compared to straight and oblique for the dog). This accounts for only partial ligament disruption in instances of feline palmar antebrachiocarpal luxation, making it a less devastating injury than in dogs.

Question 10

Are males or females predisposed to intermedioradial carpal bone fractures?

Answer 10

Males, with a breed predilection for Boxers and Spaniels.

Typically occur in active dogs that have not sustained significant trauma.

Midbody fractures also reported in the right interomedioradial carpal bone of Greyhounds.

Question 11

What are the three common configurations of intermedioradial carpal bone fractures?

Answer 11

Dorsal slab, sagittal mid body, T-fractures. These are proposed secondary to failure of fusion of the 3 centers of ossification.

Question 12

What is the most common configuration of interomedioradial carpal bone fracture in the Greyhound?

Answer 12

Oblique midbody fractures of the right side

Question 13

What are the options for repair of a interomedioradial carpal bone fracture?

Answer 13

Lag screw, headless self compressing cannulated screw, K-wires.

Excision of the fragment if it is small.

Repairs should be augmented with external coaptation for 6 weeks.

Question 14

What are the best surgical approaches for repair of interomedioradial carpal bone fractures?

Answer 14

Dorsal for small dorsal slab fractures, palmaromedial for midbody repairs. Can combine the two approaches for increased exposure.

Question 15

What is the most common presentation of accessory carpal bone fractures?

Answer 15

Type 1 fracture of the right (80%) accessory carpal bone in racing greyhounds

Question 16

What are the five classifications of accessory carpal bone fractures?

Answer 16

Type 1 (67%): attachment between the accessory carpal and ulna carpal bones.

Type 2 (13%): attachment between the accessory carpal and distal radius and ulna.

Type 3 (3%): attachment between the accessory carpal and metacarpals.

Type 4 (12%): avulsion at the tendon of insertion of the flexor carpi ulnaris.

Type 5: comminuted.

Types 1-3 are considered sprain avulsion injuries, with types 1 and 2 being intraarticular.

Question 17

What are the surgical options for accessory carpal bone fractures?

Answer 17

Lag screw fixation or fragment removal via a palmarolateral approach.

Question 18

What are the treatment recommendations for fracture of the ulnar carpal bone or the numbered carpal bones?

Answer 18

Fragment removal and external coaptation.

Question 19

What are the traditional guidelines for metacarpal fracture repair as modified from the human literature?

Answer 19

(1) if more than two metacarpal or metatarsal fractures are present in the same manus
(2) if the fractures involve both of the primary weight-bearing bones (metacarpals or metatarsals III and IV)
(3) if the fractures are articular fractures
(4) if the fracture fragment segments are displaced by >50%
(5) if the fracture involves the base of metacarpal/metatarsal II or V
(6) if the dog is a large-breed or athletic working or show dog

Question 20

What are the 3 types of metacarpal fractures seen most commonly in racing Greyhound?

Answer 20

Type 1: endosteal and cortical bone thickening.
Type 2: minimally displaced hairline fractures
Type 3: complete fractures with fragment displacement

Most commonly seen in metacarpal V of the left thoracic limb, or metacarpal II of the right thoracic limb

Question 21

What is the surgical approach for repair of the metacarpals?

Answer 21

Dorsal for digits 3/4, lateral for digit 5, medial for digit 2.

Question 22

What are surgical repair options for metacarpal fractures?

Answer 22

Intramedullary K-wires, dowel pinning, small bone plates, external fixation.

Question 23

What are the treatment options for digit fractures/luxation?

Answer 23

1. External coaptation (4-8 weeks).
2. Bone plating and screws.
3. Lag screws or K-wires and TBW for avulsion fractures of P1/P2.

Question 24

What is the treatment of sprain/luxation of the proximal interphalangeal joints?

Answer 24

1. Rest, NSAIDs +/- splint.
2. Ligament replacement or repair.

Question 25

What are the breeds most affected by sesamoid disease?

Answer 25

Rottweilers and greyhounds. Sesamoids II and VII most commonly affected (may be due to decreased vascular foramina).

Question 26

What is the recommended treatment for sesamoid disease?

Answer 26

Conservative management with rest for 4-8 weeks (no different to surgical outcomes). Surgery consists of sesamoid removal via a palmar approach and may destabilize the joint.

Question 27

Damage to which structures results in carpal hyperextension injury?

Answer 27

Flexor retinaculum and palmar fibrocartilage. Both medial and lateral collateral ligaments also play a role in preventing carpal hyperextension.

Question 28

What is the distribution of carpal luxation injuries in the dog?

Answer 28

Antebrachiocarpal: 31% Middle carpal: 22% Carpometacarpal: 47%

Question 29

Which is the most common joint injured in the cat with carpal hyperextension injury?

Answer 29

Antebrachiocarpal joint: 50% of the time. Subluxation/luxation more common in the cat compared to dogs where hyperextension without subluxation of a bone was more frequent.

Question 30

In addition to regular radiographs of the carpus, what additional views are recommended when working up possible carpal hyperextension injury?

Answer 30

Stressed radiographs.

Question 31

What is the treatment for carpal hyperextension injuries?

Answer 31

Pancarpal or partial carpal arthrodesis.

Question 32

What grade of strain to the medial or lateral collateral ligaments of the carpus will result in instability?

Answer 32

Grade 3 (complete rupture). Medial damage results in valgus instability, lateral results in varus. Stress radiographs should be performed if instability is suspected.

Question 33

What is the treatment for damage to the radial or ulnar collateral ligaments?

Answer 33

Grade 1 or 2 (sprain): conservative management. Grade 3: primary repair of the ligament with secondary augmentation (drill holes, bone anchors, or screws with wire or suture). Palmar splints/casts are recommended for 4-8 weeks post-operative. Pancarpal arthrodesis may be indicated in severe/chronic cases.

Question 34

Which side of the carpus is most commonly affected with shearing injuries?

Answer 34

Medial aspect (69%)

Question 35

What is the treatment for shearing injuries of the carpus?

Answer 35

Immediate or delayed surgical repair may be required depending on the severity of the soft tissue injuries. Repair options include: 1) Primary ligamentous repair +/- bone anchors and prosthetic ligament support. 2) Transarticular ESF. 3) Pancarpal arthrodesis.

Question 36

What is the primary clinical presentation of a patient with a flexor tendon laceration?

Answer 36

Elevation/hyperextension of the distal interphalangeal joint. Normally a puncture wound or laceration is present on the palmar aspect of the distal limb, above or below the metacarpal pad.

Question 37

Which tendon is most commonly affected in flexor tendon laceration injuries?

Answer 37

The deep digital flexor tendon, because it is situated palmar to the superficial digital flexor tendon from the level of the metacarpophalangeal joint.

Question 38

What is the treatment for flexor tendon laceration?

Answer 38

Direct suturing of the tendon. External coaptation is recommended following repair with the carpus and toes in slight flexion for 6-8 weeks.

Question 39

What are the grades of carpal collateral ligament injury?

Answer 39

Grade 1 or 2: sprains Grade 3: complete rupture

Question 40

What are the indications for pancarpal v partial tarsal arthrodesis?

Answer 40

Pancarpal arthrodesis is recommended if the antebrachiocarpal joint is involved, or if there is displacement of the ulnar carpal or accessory carpal bones.

Question 41

What is the angle used in pancarpal arthrodesis?

Answer 41

10-12 degrees of extension

Question 42

What are the described implant positions for carpal arthodesis?

Answer 42

Medial, dorsal, palmar.

Question 43

What is the tension surface of the carpal joint?

Answer 43

The palmar surface. Not commonly used due to significant soft tissue dissection required for implant placement

Question 44

How far should a pancarpal arthodesis extend on the distal radius during dorsal pancarpal arthodesis?

Answer 44

Distal 1/3. The tendons of the extensor carpi radialis muscle to metacarpals II and III are removed.

Question 45

What are the main complications associated with pancarpal arthrodesis?

Answer 45

Screw loosening, implant breakage, infection, metacarpal bone fracture, implant sensitivity, incomplete arthrodesis, and continual gait abnormality

Question 46

What are general surgical recommendations regarding carpal arthrodesis to limit complications?

Answer 46

Screw diameter should be no more than 40% of the metacarpal bone diameter, plate should span 50% of the length of metacarpal 3, using additional support of IM pins, proper alignment should be ensured, and the articular cartilage should be adequately removed. Splinting post-operative is not required.

Question 47

What types of implants can be used for pancarpal arthrodesis?

Answer 47

DCP, LC-DCP, CastLess plate, hybrid DCP (2.7/3.5mm), single or double stepped carpal arthrodesis plate. Transarticular circular or linear ESF use has also been described.

Question 48

Where is the major stress location in a pancarpal arthrodesis?

Answer 48

Distal to the last metacarpal screw. It is normally the metabone at this location that fails rather than the plate.

Question 49

How much does the antebrachioradial joint contribute to overall carpal movement?

Answer 49

85%

Question 50

What surgery is typically indicated in complete luxation of any carpal joint/bone?

Answer 50

Pancarpal arthrodesis. Complete luxations are uncommon compared to subluxations.

Question 51

What methods of fixation have been described for partial carpal arthodesis?

Answer 51

Cross-pinning, pins placed from the metacarpal bones through the carpometacarpal and middle carpal joints, plating (most commonly a dorsal T-plate). When plating care must be taken to ensure that the T-plate doesn't impinge on the distal radius during carpal extension. The screws should also not be too long in the interomedioradial carpal bone due to potential for irritation to the palmar ligaments.

Question 52

What are the most common metacarpophalangeal joints to be affected by osteoarthritis?

Answer 52

Metacarpals IV and V

Question 53

What is the most common radiographic finding in a dog with metacarpophalangeal osteoarthritis?

Answer 53

Smooth periosteal reaction of the metacarpal bone (up to 33% of the length of the metacarpal bone). Biopsy can be used to differentiate from neoplasia.

Question 54

What is carpal laxity syndrome?

Answer 54

General term used to describe carpal hyperextension, hyperflexion, or carpal flexural deformity in young puppies.

Question 55

Is carpal laxity syndrome more common in female or male dogs?

Answer 55

2:1 male predilection. Normally seen in dogs 5-27 weeks old. Typically caused by an over- or under-supplemented diet.

Question 56

What is the treatment for carpal laxity syndrome?

Answer 56

Appropriate diet, controlled exercise program on flooring that provided good traction. Normally resolves within 2 weeks.

Question 57

What is the most common type of digital mass in dogs?

Answer 57

Squamous cell carcinoma, followed by melanoma, soft tissue sarcoma and mast cell tumour. Subungual SCC has a better prognosis.

Question 58

Pulmonary metastasis from digit masses was most frequent with which type of tumour?

Answer 58

Melanoma (32%)

Question 59

What is the most common type of digital mass in cats?

Answer 59

SCC

Question 60

What structure needs to be preserved with removal of the digit at the distal interphalangeal joint?

Answer 60

The digital pad.

Question 61

What is a paw pad corn?

Answer 61

A circular, firm, raised hyperkeratotic lesion in the center of a digital pad.

Question 62

Where are the majority of paw pad corns found in Greyhounds?

Answer 62

Digits 3 and 4 of the thoracic limbs (90%)

Question 63

What is the recurrence rate of paw pad corns following surgical excision in Greyhounds?

Answer 63

50%

Question 64

In a study by Petazzoni 2022 in JAVMA, was bandaging of carpal flexural contracture deformities associated with an improved outcome over rest alone?

Answer 64

Only in high grade (grade 3 patients).

Question 65

Based on a study by Petazzoni 2022 in JAVMA, what grade of carpal flexural contracture deformity is depicted?

Answer 65

Question 66

Based on a study by Petazzoni 2022 in JAVMA, what grade of carpal flexural contracture deformity is depicted?

Answer 66

Question 67

Based on a study by Petazzoni 2022 in JAVMA, what grade of carpal flexural contracture deformity is depicted?

Answer 67

Question 68

In a study by Milgram 2019 in VCOT, did transection of the palmar ulnocarpal and radiocarpal ligaments have a significant impact on carpal biomechanics?

Answer 68

No - this would suggest that in cases of carpal hyperextension injury more than just the ulno- and radiocarpal ligaments are damaged.

Question 69

In a study by Chong 2022 in VCOT, what was the difference in complications reported when using a titanium hybrid advanced locking plate system (ALPS) v. hybrid dynamic compression plate for pancarpal arthrodesis?

Answer 69

There was no reported difference in complications or outcomes, although the ALPS achieved longer metacarpal coverage (74% v 57%). The hybrid dynamic compression plate tapers distally to facilitate soft tissue closure and use of smaller metacarpal screws, whereas the ALPS is a locking plate designed for use in diaphyseal fractures but facilitates placement of either both larger locking or smaller sized cortical screws (ideal for placement in the metacarpal bones).