The carpus, metacarpus and digits Flashcards
Name the bones of the carpus.
Describe the dorsal ligaments of the carpus.
Describe the palmar ligaments of the carpus.
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.
Describe the attachments of the flexor retinaculum and palmar fibrocartilage.
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.
What are the three joints of the carpus?
Antebrachiocarpal, middle, carpometacarpal joint.
What are the stabilizing structures of the carpus?
Short extra-articular and intra-articular ligaments, an articular disc (or radioulnar ligament), palmer fibrocartilage, and joint capsule.
How many sesamoid bones are there at the heads of the metacarpals?
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.
What are the three parts of the metacarpals?
From proximal to distal: base, body, head.
What are two major anatomic differences between the canine and feline manus?
- The ability to retract the claws due to the anatomy of the dorsal elastic ligaments and structural differences in the middle and distal phalanx.
- 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.
Are males or females predisposed to intermedioradial carpal bone fractures?
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.
What are the three common configurations of intermedioradial carpal bone fractures?
Dorsal slab, sagittal mid body, T-fractures. These are proposed secondary to failure of fusion of the 3 centers of ossification.
What is the most common configuration of interomedioradial carpal bone fracture in the Greyhound?
Oblique midbody fractures of the right side
What are the options for repair of a interomedioradial carpal bone fracture?
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.
What are the best surgical approaches for repair of interomedioradial carpal bone fractures?
Dorsal for small dorsal slab fractures, palmaromedial for midbody repairs. Can combine the two approaches for increased exposure.
What is the most common presentation of accessory carpal bone fractures?
Type 1 fracture of the right (80%) accessory carpal bone in racing greyhounds
What are the five classifications of accessory carpal bone fractures?
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.
What are the surgical options for accessory carpal bone fractures?
Lag screw fixation or fragment removal via a palmarolateral approach.
What are the treatment recommendations for fracture of the ulnar carpal bone or the numbered carpal bones?
Fragment removal and external coaptation.
What are the traditional guidelines for metacarpal fracture repair as modified from the human literature?
(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
What are the 3 types of metacarpal fractures seen most commonly in racing Greyhound?
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
What is the surgical approach for repair of the metacarpals?
Dorsal for digits 3/4, lateral for digit 5, medial for digit 2.
What are surgical repair options for metacarpal fractures?
Intramedullary K-wires, dowel pinning, small bone plates, external fixation.
What are the treatment options for digit fractures/luxation?
- External coaptation (4-8 weeks).
- Bone plating and screws.
- Lag screws or K-wires and TBW for avulsion fractures of P1/P2.
What is the treatment of sprain/luxation of the proximal interphalangeal joints?
- Rest, NSAIDs +/- splint.
- Ligament replacement or repair.
What are the breeds most affected by sesamoid disease?
Rottweilers and greyhounds. Sesamoids II and VII most commonly affected (may be due to decreased vascular foramina).
What is the recommended treatment for sesamoid disease?
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.
Damage to which structures results in carpal hyperextension injury?
Flexor retinaculum and palmar fibrocartilage. Both medial and lateral collateral ligaments also play a role in preventing carpal hyperextension.
What is the distribution of carpal luxation injuries in the dog?
Antebrachiocarpal: 31%
Middle carpal: 22%
Carpometacarpal: 47%
Which is the most common joint injured in the cat with carpal hyperextension injury?
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.
In addition to regular radiographs of the carpus, what additional views are recommended when working up possible carpal hyperextension injury?
Stressed radiographs.
What is the treatment for carpal hyperextension injuries?
Pancarpal or partial carpal arthrodesis.
What grade of strain to the medial or lateral collateral ligaments of the carpus will result in instability?
Grade 3 (complete rupture). Medial damage results in valgus instability, lateral results in varus.
Stress radiographs should be performed if instability is suspected.
What is the treatment for damage to the radial or ulnar collateral ligaments?
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.
Which side of the carpus is most commonly affected with shearing injuries?
Medial aspect (69%)
What is the treatment for shearing injuries of the carpus?
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.
What is the primary clinical presentation of a patient with a flexor tendon laceration?
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.
Which tendon is most commonly affected in flexor tendon laceration injuries?
The deep digital flexor tendon, because it is situated palmar to the superficial digital flexor tendon from the level of the metacarpophalangeal joint.
What is the treatment for flexor tendon laceration?
Direct suturing of the tendon. External coaptation is recommended following repair with the carpus and toes in slight flexion for 6-8 weeks.
What are the grades of carpal collateral ligament injury?
Grade 1 or 2: sprains
Grade 3: complete rupture
What are the indications for pancarpal v partial tarsal arthrodesis?
Pancarpal arthrodesis is recommended if the antebrachiocarpal joint is involved, or if there is displacement of the ulnar carpal or accessory carpal bones.
What is the angle used in pancarpal arthrodesis?
10-12 degrees of extension
What are the described implant positions for carpal arthodesis?
Medial, dorsal, palmar.
What is the tension surface of the carpal joint?
The palmar surface. Not commonly used due to significant soft tissue dissection required for implant placement
How far should a pancarpal arthodesis extend on the distal radius during dorsal pancarpal arthodesis?
Distal 1/3.
The tendons of the extensor carpi radialis muscle to metacarpals II and III are removed.
What are the main complications associated with pancarpal arthrodesis?
Screw loosening, implant breakage, infection, metacarpal bone fracture, implant sensitivity, incomplete arthrodesis, and continual gait abnormality
What are general surgical recommendations regarding carpal arthrodesis to limit complications?
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.
What types of implants can be used for pancarpal arthrodesis?
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.
Where is the major stress location in a pancarpal arthrodesis?
Distal to the last metacarpal screw. It is normally the metabone at this location that fails rather than the plate.
How much does the antebrachioradial joint contribute to overall carpal movement?
85%
What surgery is typically indicated in complete luxation of any carpal joint/bone?
Pancarpal arthrodesis. Complete luxations are uncommon compared to subluxations.
What methods of fixation have been described for partial carpal arthodesis?
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.
What are the most common metacarpophalangeal joints to be affected by osteoarthritis?
Metacarpals IV and V
What is the most common radiographic finding in a dog with metacarpophalangeal osteoarthritis?
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.
What is carpal laxity syndrome?
General term used to describe carpal hyperextension, hyperflexion, or carpal flexural deformity in young puppies.
Is carpal laxity syndrome more common in female or male dogs?
2:1 male predilection.
Normally seen in dogs 5-27 weeks old. Typically caused by an over- or under-supplemented diet.
What is the treatment for carpal laxity syndrome?
Appropriate diet, controlled exercise program on flooring that provided good traction. Normally resolves within 2 weeks.
What is the most common type of digital mass in dogs?
Squamous cell carcinoma, followed by melanoma, soft tissue sarcoma and mast cell tumour. Subungual SCC has a better prognosis.
Pulmonary metastasis from digit masses was most frequent with which type of tumour?
Melanoma (32%)
What is the most common type of digital mass in cats?
SCC
What structure needs to be preserved with removal of the digit at the distal interphalangeal joint?
The digital pad.
What is a paw pad corn?
A circular, firm, raised hyperkeratotic lesion in the center of a digital pad.
Where are the majority of paw pad corns found in Greyhounds?
Digits 3 and 4 of the thoracic limbs (90%)
What is the recurrence rate of paw pad corns following surgical excision in Greyhounds?
50%
In a study by Petazzoni 2022 in JAVMA, was bandaging of carpal flexural contracture deformities associated with an improved outcome over rest alone?
Only in high grade (grade 3 patients).
Based on a study by Petazzoni 2022 in JAVMA, what grade of carpal flexural contracture deformity is depicted?
Based on a study by Petazzoni 2022 in JAVMA, what grade of carpal flexural contracture deformity is depicted?
Based on a study by Petazzoni 2022 in JAVMA, what grade of carpal flexural contracture deformity is depicted?
In a study by Milgram 2019 in VCOT, did transection of the palmar ulnocarpal and radiocarpal ligaments have a significant impact on carpal biomechanics?
No - this would suggest that in cases of carpal hyperextension injury more than just the ulno- and radiocarpal ligaments are damaged.
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?
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).
