Metacarpus/metatarsus Flashcards
Describe the anatomy of the metacarpal/metatarsal region
Cannon bone (3rd metacarpus/tarsus bone) and two splint bones
Which structure runs down the dorsal aspect of the 3rd metacarpal/tarsal bone, how is it different in the FL and HL?
Digital extensor tendon
– made up of the common and lateral in the FL this tendon al extensor tendons in the HL the lateral extensor tendon merges into the long digital extensor tendon to continue down as a single tendon
Which structures are found on the palmar aspect of the 3rd metacarpal/tarsal bone?
- SDFT
- DDFT
- Check ligament/accessory ligament of the DDFT
- Suspensory ligament: divides into two branches that insert onto the proximal sesamoid bones
Describe the Digital flexor tendon sheath
Synovial ‘sleeve’ like structure that allows the SDFT and DDFT to pass through the fetlock canal. Anchored in placed by the annular ligament
What may be found on clinical examination when investigating problems of the metacarpus/metatarsus
Pain/heat/soft tissue swelling
Joint/tendon sheath effusion
Crepitus/pain on percussion
Describe diagnostic analgesia of the metacarpus/metatarsus
- H4/H6 NB
- Subcarpal/subtarsal block
- Lateral palmar nerve/deep branch of lateral plantar
nerve (DBLPN) block
Which radiographic views would you want to take of the metacarpus/metatarsus
Standard projections (DP, LM, DMPLO, DLPMO)
List some bone conditions of the metacarpus/metatarsus
- Fractures of the third metacarpal/metatarsal bone
- Dorsal metacarpal bone disease
- Fractures of the second/fourth metacarpal/metatarsal (“splint”) bones
- Exostosis of the second/fourth metacarpal/metatarsal bones (“splints”)
List some (Palmar) soft tissue conditions of the metacarpus/metatarsus
SDFT/DDFT tendinitis
ALDDFT desmitis
SL desmitis
PAL syndrome
Which 4 types of fractures can occur in the third metacarpus/metatarsus
Condylar fractures (lateral and medial)
Diaphyseal
Transverse
Proximal articular
What are the causes of Fractures of the third metacarpus/metatarsus
Usually single overload injury or external trauma (e.g. kick)
Condylar Fractures of the third metacarpus/metatarsus are usually caused by …?
Condylar fractures usually fail due to repetitive strain cycles
- Pre-existing changes parasagittal to the ridge
How do Fractures of the third metacarpus/metatarsus usually present clinically?
- Lame (moderate/severe, acute), signalment
- Swelling/crepitus/pain on palpation/flexion
- +/- joint effusion
- Displacement (diaphyseal)
- Open/closed
Describe how to carry out radiography for suspected fractures of the third metacarpus/metatarsus
- Standard views plus additional to work out configuration
- Do not over collimate: lateral condylar f# tend to exit laterally above physeal scar whereas medial condylar f# tend to spiral proximally
How do open/closed fractures need to be initially managed?
- Need to make sure a closed fracture doesn’t become an open fracture by stabilising it
- Zone 2 external co-aptation (lateral condylar f# two splints placed lat. and med.)
- Open fractures (especially if infected) have a poor prognosis and are hard to treat
Describe the management options for fractures of the third metacarpus/metatarsus based on the fracture type
- Conservative: Non-displaced, closed, transverse and some proximal articular fractures
- Surgical: Condylar fractures, diaphyseal fractures
- Euthanasia: Displaced, open, comminuted
Dorsal metacarpal disease is also known as?
Also known as “sore shins” or “bucked shin complex” in young racehorses
What is dorsal metacarpal disease?
- Excessive cyclic loading results in painful periosteitis as 2yo
- Some of these horses go on to develop dorsal cortical “stress” fractures as 3yo
How does dorsal metacarpal disease present?
Present with focal pain/swelling/ reduced performance/mild lameness
How is dorsal metacarpal disease managed?
- Alterations in training regime
- Some refractory cases undergo shockwave or osteostixis (drilling)/screw placement
Which splint bone is most commonly fractured?
Often lateral hind splint bone (MtIV)
What are the causes of splint bone fractures?
Usually due to trauma (kick) but distal fractures may be secondary to abnormal stress from fetlock hyperextension
How does a proximal splint bone fracture potentially lead to sepsis?
Proximal f# may communicate with CMC/TMT (joint sepsis)
How are splint bone fractures managed?
- Conservative
- Rest; NSAIDs, AB’s; remove small loose fragments; wound debridement
- Watch out for sequestration! - Surgical - Partial ostectomy; internal fixation (proximal articular)
Exostosis of the second/fourth metacarpal/metatarsal bones (“splints”) is caused by?
Trauma resulting in periosteal bleed then bone formation
(An exostosis is an extra growth of bone that extends outward from an existing bone)
What are the clinical signs of Exostosis of the second/fourth metacarpal/metatarsal bones (“splints”)?
Acute phase: pain, heat, swelling
Chronic phase: bony swelling
How is Exostosis of the second/fourth metacarpal/metatarsal bones (“splints”) diagnosed?
Clinical examination
Radiography (ultrasonography)
How is Exostosis of the second/fourth metacarpal/metatarsal bones (“splints”) managed?
Conservative: rest, cold therapy, NSAIDs, local c/s
Surgical: if recurrent or severe (otherwise avoid sx!)
Describe the clinical findings on a horse with SDFT tendonitis
Swelling/pain/loss of normal borders
Fetlock sinking
(Carpal sheath/DFTS effusion)
Describe the ultrasound findings on a horse with SDFT tendonitis
Core lesion versus generalised changes
Focal anechoic lesions in the SDFT
What are the 3 phases of SDFT tendonitis treatment?
- Acute (hours-days)
- Reparative/proliferative phase (days-weeks)
- Chronic modelling (weeks-months)
Describe the acute treatment of SDFT tendonitis?
Limit inflammation - Cold hosing/NSAIDs
Protect limb/reduce further damage - supporting dressing/box rest
Describe the reparative/proliferative phase treatment of SDFT tendonitis?
- Promote angiogenesis: Tendon splitting, stem cells, PRP, ultrasound
- Minimise formation of excessive scar tissue: PRP, stem cells, ultrasound therapy
- Early exercise: Positive effect on Type III to type I collagen
Describe the chronic modelling phase treatment of SDFT tendonitis?
Controlled exercise programme
Describe the main features of DDFT tendonitis
Less common c.f. SDFT/SL
Seen in digital flexor tendon sheath or digit
Also seen in carpal and tarsal sheath
Markedly enlarged DDFT
Describe the main features of accessory ligament of the DDFT desmitis
Swelling in the proximal palmar metacarpus deeper to SDFT
Tx: rest, cold therapy; NSAIDs
Px: guarded; heals poorly; contractures
How would ALDDFT desmitis appear on ultrasound?
Enlarged ALDDFT with reduced echogenicity
Note that the enlarged ALDDFT is pushing the tendons round to the medial side
Describe the acute and chronic presentation of Suspensory ligament desmitis
Acute: swelling, heat, pain
Chronic: lameness; poor performance (esp. HL)
How is suspensory ligament desmitis diagnosed?
- Palpation
- Local analgesia (e.g. L4/6 NB for branch lesions; lateral palmar n.; deep branch of the lateral plantar n.)
- Ultrasound: shows ligament enlargement with poor fibre pattern
Describe conservative treatment for desmitis of the suspensory ligament
Cold hosing (acute); rest; NSAIDs
3-6 months rest
Monitor healing with ultrasound
Describe surgical treatment for desmitis of the suspensory ligament
Mainly for chronic desmitis of the proximal portion in the hindlimb
- Compartment syndrome alleviated by DBLPN neurectomy and fasciotomy
- 60-80% return to function
List some causes of damage to the digital flexor tendon sheath and palmar/plantar annular ligament in the horse
- DFTS tenosynovitis
- SDFT tear: Manica flexoria
- DDFT tear
- PAL desmitis
- Combination
- (sepsis)
List the clinical signs of palmar annular ligament syndrome in the horse
- DFTS effusion (often marked)
- Notching of limb: PAL constriction
- Lameness (mild-moderate)
- Pain on flexion
- +ve response to DFTS analgesia or perineural analgesia (L4NB)
Describe diagnostic imaging for palmar annular ligament syndrome
Ultrasound (PAL/SDFT/DDFT/MF)
- Reduced echogenicity of the PAL
Assess tendons/PAL thickness (1-2mm)
Describe conservative treatment of palmar annular ligament syndrome
Cold hosing/Rest/controlled exercise
Anti-inflammatories
- Systemic NSAIDs
- Local corticosteroids/HA into sheath
Describe surgical treatment of palmar annular ligament syndrome
Surgical (tenoscopy)
- Assess tendons for damage/tears (SDFT/DDFT/MF): Remove damaged portions
- PAL desmotomy: Relieve compression
