Pastern And Fetlock MOD 2021/22 Lecture Notes - PDF

Pastern and fetlock MOD 2021/22 Dr Peter Milner Senior Lecturer Equine Orthopaedics BEVA 2009 Learning outcomes • To review the functional anatomy of the pastern and fetlock region • To explain the logical use of diagnostic tests to reach a diagnosis of the fetlock and pastern region • To describ...

Pastern and fetlock MOD 2021/22 Dr Peter Milner Senior Lecturer Equine Orthopaedics BEVA 2009 Learning outcomes • To review the functional anatomy of the pastern and fetlock region • To explain the logical use of diagnostic tests to reach a diagnosis of the fetlock and pastern region • To describe the diagnostic imaging approach to orthopaedic disease in the fetlock and pastern region • To recognise the common orthopaedic pathologies of the fetlock and pastern region • To understand the management options for conditions affecting the pastern and fetlock regions Anatomy of the pastern region • PIPJ – P1/P2 stabilised by collateral ligaments – Supported by distal sesamoidean ligaments and insertion of SDFT branches on palmar/plantar scutum – Low motion joint Oblique sesamoidean ligaments Straight sesamoidean ligament SDFT branch Collateral ligaments of PIPJ Palmar (plantar) scutum P1 • High loading, esp dorsally P2 P1 P2 Anatomy of the fetlock region • MCPJ/MTPJ – P1/Mc(Mt)III/PSBs – Collateral/collateral sesamoidean ligaments – Suspensory ligament (branches) – High motion joint • Hyperextension leads to increased dorsal contact and palmar loading – Fetlock primarily supported by the SL (with contribution by the SDFT) Mc3 PSB P1 Extensor tendon SL branch Mc3 Collateral ligaments PSB Collateral sesamoidean ligament Extensor branch P1 Straight sesamoidean ligament Oblique sesamoidean ligament Investigation of pastern/fetlock problems • Clinical examination – Pain/lameness, swelling (synovial/soft tissue), heat, instability, ROM • Diagnostic anaesthesia – Perineural: ASNB; L4/6NB L4NB:Medial/lateral palmar and palmar metacarpal n. L6NB:Medial/lateral plantar and plantar metatarsal n. dorsal metatarsal n. (med/lat) – Intra-synovial: PIPJ; MCPJ; (DFTS) • Diagnostic imaging – Radiography • Pastern: DP, LM, DMPLO, DLPMO • Fetlock: DP, LM, DMPLO, DLPMO, flexed LM – Ultrasonography – Advanced imaging e.g. nuclear scintigraphy, MRI or CT Radiographic projections of the pastern region LM DLPMO 10o DP DMPLO Radiographic projections of the fetlock region 10o DP LM Flexed LM Note: as well as aiming 10o down in the DP view, we also do this in the DLMPO and DMPLO views DLPMO DMPLO Conditions of the equine pastern • • • • Osteoarthritis Osteochondrosis Soft tissue injuries Fractures/subluxation Osteoarthritis of the pastern • Pastern OA common (“articular ringbone”) • High loading/low motion joint • Progressive destruction of articular cartilage with subchondral bone thickening and osteophyte production – Severe cases may have cystic formation/joint collapse • Maybe insidious or secondary to other problem (e.g. trauma, sepsis, osteochondrosis) • Clinical findings Pastern OA – diagnosis and management – Lameness (mild to moderate) – Bony thickening over dorsal pastern • Diagnostic anaesthesia – Perineural or intra-articular • Radiography – Standard projections – Changes often dorsal • Management – Rest/light exercise, intra-articular medication, shoeing, NSAIDs – Arthrodesis (surgical, chemical) Radiographic signs of pastern OA Red circles indicate marked osteophytosis, entheseous new bone and subchondral bone sclerosis Osteochondrosis • Uncommon in the pastern (c.f. tarsus/stifle) • Manifestations include osseous cysts (P1 or P2) or palmar/plantar osteochondral fragmentation • Guarded prognosis • Management often palliative • (Arthrodesis) Severe secondary OA P1 cysts Soft tissue injuries • These include: – SDFT branch injury – Distal sesamoidean ligament injury • Oblique or straight sesamoidean ligament • Usually present acutely lame following traumatic injury • Moderate lameness and soft tissue swelling • Ultrasonography • Management: rest, NSAIDs, monitor healing by ultrasound P1 and P2 fractures • P1 fractures – Sagittal, frontal, comminuted – Often seen in racehorses (esp. sagittal P1) but also other horses/athletic disciplines – P1 fractures begin at sagittal groove at articular surface • Extend distally (short <30mm; long>30mm) • Complete fractures exit lateral cortex or through PIPJ • P2 fractures – Palmar/plantar eminence, comminuted – Usually due to acute overload injury Pastern fractures - management • Clinical findings – Usually acute onset severe lameness +/- instability +/joint effusion – Radiography usually sufficient for diagnosis (also CT/MRI) • First aid stabilisation – Zone 1 external coaptation – see 3rd yr • Decision making – Conservative • Short, incomplete fractures – Surgical • Internal fixation – most cases – Euthanasia • Comminuted, open, unstable Pastern subluxation • Aetiology – Traumatic event (e.g. cattle grid/fence) – Fracture/subluxation common (e.g. avulsion fracture) • Clinical presentation – Acute lameness/instability – Marked soft tissue swelling • Diagnosis – Radiography +/- stress • Management – Initially stabilise through external coaptation (zone 1) but often require pastern arthrodesis Conditions of the equine fetlock • • • • • • • • PSB fractures Sesamoiditis Osteochondral fragmentation of P1 Osteochondrosis Osteoarthritis Subchondral bone disease/POD Chronic proliferative synovitis Subluxation Proximal sesamoid bone fractures • Include apical (<30% of bone), mid-body, axial, basilar and comminuted – May be uniaxial or biaxial • Usually acute trauma but may be due to non-adaptive modelling • Clinical signs usually acute lameness with swelling and pain on palpation +/- joint effusion • Diagnostic imaging – Standard radiographic projections but may need additional oblique views – Ultrasonography important as may also have concurrent SL injuries PSB fractures - management • Management – Conservative • Uniaxial PSB fractures in foals • Non-articular – Surgical • Fragment removal (e.g. apical fracture removed arthroscopically) • Fracture repair (e.g.mid-body) – Euthanasia • Biaxial/comminuted fractures Sesamoiditis • Inflammation around the soft tissues of the palmar fetlock – Increased size/no. vascular channels • Seen in young performance horses • May be an indicator of SL branch/annular ligament injury (ultrasound exam) • Management – Rest/NSAIDs + local cold therapy – Shockwave therapy in refractory cases Osteochondral fragmentation of P1 • Osteochondral fragmentation of proximal P1 (dorsal or palmar/plantar) – Traumatic origin? • May not be clinically relevant (or relevant at high speed) so need to prove significance (e.g. diagnostic analgesia) • Radiography – Check contralateral limb • Fragment removal frequently performed arthroscopically – Larger eminence fractures can be repaired Osteochondrosis • Includes OCD of the sagittal ridge of Mc/MtIII (top image) and osseous cysts of distal McIII (bottom image) – OCD may be seen as flattening of the sagittal ridge to separate fragmentation • Usually seen in young horses (1-4 fetlocks involved) with joint effusion +/- lameness • Radiography • Management includes surgical removal of fragments (OCD) or curettage of the cyst Fetlock OA • Degenerative joint disease resulting in joint effusion, cartilage loss, osteophyte production and loss of joint function – May be secondary to trauma, sepsis, osteochondrosis • Clinical findings – Lameness exacerbated by fetlock flexion; reduced ROM – Positive i/a anaesthesia This is severe OA showing marked cartilage loss and osteophyte production Radiographic signs of fetlock OA Periarticular osteophyte formation (particularly proximodorsal aspect of P1 and dorsoproximal and dorsodistal margins of PSBs), modelling of proximal aspects of the dorsal and palmar sagittal ridges, subchondral Fetlock OA - management • Mild/early cases: – Intra-articular medication e.g. hyaluranon/ corticosteroids • Moderate: – NSAIDs, i/a corticosteroids, IRAP, polyacrylamide gel • Severe cases – Arthrodesis (salvage); euthanasia • Prognosis – Guarded for athletic use Palmar/plantar osteochondral disease • Degenerative condition of the distal condyles of young racehorses – Repetitive high strain on bone and articular tissues leading to cartilage loss with eventual collapse of the articular surface – Associated with repeated corticosteroid use? • Clinical signs – Mild/moderate lameness in 1 or more limbs localised to the fetlock • Radiography – Minimal signs to focal increases in bone density (sclerosis) and change in contour of the subchondral bone – Advanced imaging include nuclear scintigraphy and MRI • Management – Alteration in exercise schedule Sagittal MRI showing low signal intensity in plantar condyle of MtIII Chronic proliferative synovitis • Aetiology (usually forelimb) – Chronic repetitive trauma to dorsal aspect of fetlock due to hyperextension – Can lead to supracondylar bone lysis • Clinical findings Notch in distal McIII – Lameness, reduced range of motion, heat/pain • Radiography – Crescent shaped bone loss distal McIII – Soft tissue swelling Soft tissue swelling • Ultrasonography – Thickening of dorsal synovial pad • Management – Intra-articular medication; surgical resection This radiograph is deliberately underexposed to highlight the soft tissue swelling Fetlock subluxation • Often due to trauma – Disruption of the collateral ligaments +/- avulsion fracture • Diagnosis – Acute, severe lameness +/overt luxation – Radiography +/- stress • Management – Closed reduction + cast • Will fibrose but may end up with OA – Arthrodesis if unstable