Upper forelimb Flashcards
Which bones make up the carpus from proximal to distal
Radius proximally
2 rows of carpal bones:
- Proximal row from medial to lateral = radial CB, intermediate CB, ulnar CB and on the palmarolateral aspect, the accessory carpal bone
- Distal row from medial to lateral = 2nd CB, 3rd CB, 4th CB. The 1st CB may also be present in some horses and can misleadingly appear like a small fracture
2nd, 3rd and 4th metacarpal bones distally
Name and describe the joints of the carpal region, from proximal to distal
Top joint = radiocarpal joint also known as the antebrachial carpal joint
Intercarpal joint = between the proximal and distal row of carpal bone
Carpometacarpal joint = not a hinge joint unlike the other two. This joint communicates with the intercarpal joint so pathology in one can affect the other
Name the ligaments and tendons of the carpal region
Common digital extensor – insets on P3 – extensor of carpus and digital
Lateral digital extensor – inserts on P2 – extensor of carpus and digital
Extensor carpi radialis – inserts on the proximal metacarpus
Medial and lateral collateral ligaments to stabilise the carpus – restricts it to flexion and extension
How can problems of the carpus be investigated using a clinical exam
- Pain/heat/soft tissue swelling
- Reduced ROM, crepitus
- Joint effusion (differentiate from extensor tendon sheath effusion dorsally)
How can problems of the carpus be investigated using diagnostic analgesia
Carpal joint anaesthesia (RC and MC)
Median/ulnar nerve block
How can problems of the carpus be investigated using radiography - which views?
DP, LM, DMPLO, DLPMO, flexed LM
Additional views to skyline carpal bones
How can problems of the carpus be investigated using ultrasonography - which structures can be assessed?
Carpal and digital extensors and sheaths dorsally
Carpal sheath (SDFT/DDFT, ALSDFT) palmarly
What is carpal osteoarthritis
Degenerative joint disease affecting one or more of the carpal joints
What are the causes of carpal osteoarthritis?
- Secondary to joint trauma, sepsis, fracture or soft-tissue injury (e.g. intercarpal ligament injury)
- Poor conformation may predispose to carpal OA
- Arabs predisposed to CMC (carpometacarpal joint) OA – this can then lead to middle carpal joint disease due to communication of these joints
What are the clinical signs of carpal osteoarthritis?
Lameness
Joint effusion
Fibrosis
Reduced ROM
Positive to carpal flexion
Crepitus
New bone formation linked to joints = ?
Osteophytes
New bone formation linked to the joint capsule = ?
Enthesiophytes
How is carpal osteoarthritis diagnosed?
Clinical signs
Intra-articular anaesthesia
Radiography - Soft tissue swelling and new bone formation dorsally
How is carpal osteoarthritis managed?
Intra-articular medication; NSAIDs
Arthrodesis in advanced cases (drilling of CMC)
A carpal chip fracture is also known as?
Osteochondral fragmentation
What is Osteochondral fragmentation?
May be fragmentation of an osteophyte (in OA) or fragmentation of the dorsal articular margin with training (racing breeds)
How does osteochondral fragmentation occur?
- Sclerosis of subchondral bone may predispose pathology
- Can be due to excessive loading on the dorsal aspect of the carpal joint: bone becomes more dense and brittle -> fragmentation
How is Osteochondral fragmentation managed?
Management usually involved arthroscopic removal of the fragment(s)
How do carpal bone fractures usually present?
- Include slab, frontal and comminuted fractures
- Often present as acute single overload but may result from stress maladaptation (e.g. sclerosis from repetitive loading)
- Present as acute lameness + joint effusion with pain/crepitus on palpation
How are carpal bone fractures diagnosed?
Radiography (inc. skyline views)
How are carpal bone fractures managed?
Conservative - Incomplete f#
Surgical
- Usually internal fixation via arthroscopy
- Incomplete or complete f#
What is the main cause of accessory carpal bone fractures?
Trauma/single impact overload
How do horses with accessory carpal bone fractures present?
- Acute lameness with swelling/pain over the palmar carpus
- Horse may stand with carpus semi-flexed
- Antebrachiocarpal joint effusion and/or carpal sheath effusion
Describe management of horses with Accessory carpal bone fractures
Conservative - Most cases heal by fibrosis
Surgical
- Repair difficult (shallow/curved bone)
- Remove any fragments in joint
What is the carpal canal?
Carpal canal = synovial structure – tendon sheath – where tendons form from muscle
Which structure inserts on the SDFT in the carpal canal?
Accessory ligament of the SDFT – superior check ligament
(remember the accessory ligament of the DDFT aka inferior check ligament, is in the metacarpus)
List some causes of carpal canal syndrome
- Idiopathic tenosynovitis - haemorrhage or secondary to other cause
- Septic tenosynovitis - may or may not have a wound; seen secondary to elective tenoscopy
- Tendinitis of the SDFT/DDFT (or muscle tears)
- AL-SDFT (SCL) desmitis
- Radial physeal exostosis
- Osteochondroma of the distal radius: discrete separate centres of cartilage ossification
- Accessory carpal bone (ACB) fracture: ACB forms lateral boundary of carpal sheath through carpus
List the clinical signs of carpal canal syndrome
Carpal sheath effusion
Lameness/pain - Flexion often exacerbates lameness/pain
Puncture wound with sepsis
How is carpal canal syndrome diagnosed?
- Diagnostic anaesthesia (median/ulnar nerve block or carpal sheath anaesthesia)
- Synoviocentesis
- Radiography
- Ultrasonography
How can the underlying causes of carpal canal syndrome be treated?
- Tenoscopic lavage (e.g. sepsis)
- Removal of exostosis/osteochondroma via tenoscopy
- Debridement of damaged tendon/ligament
- Local anti-inflammatories into the carpal sheath
What is the main cause of carpal subluxation?
Usually trauma (e.g. high speed fall)
- Often have additional carpal bone fractures
How does a horse with carpal subluxation present?
Horse is severely lame with marked swelling, carpal instability and overt anatomical derangement
Radiograph to determine level of luxation and presence of fractures
How should a horse with carpal subluxation be managed?
- Stabilise with full limb bandage plus splints (zone 3 external coaptation)
- Euthanasia in many cases esp with fractures/carpal bone collapse
- Surgical partial or complete arthrodesis possible
What is the most common cause of radial fractures?
Usually due to external trauma (e.g. kick) esp. distomedial radius
How do horses with radial fractures present?
Moderate swelling and lameness but can weight-bear (incomplete fractures) - Check for wounds!
Open/complete fractures in adult horses usually euthanased
Describe conservative management of radial fractures?
- Most closed, incomplete fractures in adults managed conservatively
- Full limb bandage plus caudal and lateral splint - Cross-tie but head down for feeding
- Regular monitoring – can still displace!
Which is surgical treatment indicated for radial fractures?
Internal fixation in foals
What is the most common cause of ulnar fractures?
Trauma/kick leading to the fracture of the proximal ulna (olecranon)
How do horses with ulnar fractures present?
Acute lameness +/- wound with swelling/pain around elbow
Dropped elbow stance (ddx radial nerve paralysis, triceps myopathy)
Describe first air for ulnar fractures
Splint carpus as lost stay apparatus
Describe conservative management of ulnar fractures
Tend to get a non-union or delayed union of the fracture in this area due to the pull of the triceps muscle so generally advise against
Describe surgical management of ulnar fractures
- Tension-band principal by converting distractive forces of triceps to compression
- Plate fixation in adults (plate or wire/pins in foals) generally do well
What are the main causes of Fractures of the humerus and scapula?
Usually acute trauma (kick, impact); also stress f# in racehorses
Describe the presenting signs of Fractures of the humerus and scapula
- Moderate to severe lameness with loss of limb function with complete fracture
- Radiography can be difficult in this region
Describe the management of Fractures of the humerus and scapula
- Complete humeral fractures = euthanasia
- Conservative e.g. deltoid tuberosity, scapula spine
- Sporadic reports of surgical repair but difficult!!
How would Osteochondrosis of the elbow appear on radiography?
Osseous cyst-like lesions in proximal radius
How would Osteochondrosis of the shoulder appear on radiography?
Osseous cyst-like lesions in the distal scapula (also proximal humerus)
OCD of the glenoid cavity
Describe management of Osteochondrosis of the elbow
Conservative (intra-articular medication) or surgical (extra-articular drilling)
Shoulder dysplasia and subluxation is most commonly seen in which horses?
Shetland/Miniature breeds
How does shoulder dysplasia and subluxation present?
Malalignment results in pain/instability
Subluxation can occur without dysplasia secondary to trauma
Moderate/severe lameness with pain on shoulder extension/abduction
How does shoulder dysplasia and subluxation present on radiography?
Abnormal alignment of scapulohumeral joint
Often secondary OA present
Describe management of shoulder dysplasia and subluxation
- Reduction under GA possible but often recurs
- Secondary OA managed conservatively
- Shoulder arthrodesis a possibility but most cases euthanased
Describe the typical presentation of shoulder osteoarthritis
- Seen infrequently
- Shetland ponies /Miniature breeds predisposed
- Affected horses/ponies generally moderately to severely lame
Shoulder osteoarthritis occurs secondary to?
Trauma, intra-articular fracture, osteochondrosis , sepsis
How is shoulder osteoarthritis managed?
Palliative treatment; prognosis guarded
Describe the main features of elbow osteoarthritis
Unusual to get OA in the elbow in horses
Secondary to trauma, sepsis, OCLL
Describe diagnosis of elbow osteoarthritis
Can be difficult to diagnose
Diagnostic anaesthesia of the elbow joint difficult!
Radiography
Describe management of elbow osteoarthritis
Intra-articular medication, NSAIDs
Guarded prognosis
