Russell Parker BVSc MSc DipECVS MRCVS Liphook Equine Hospital LIPHOOK EQUINE HOSPITAL
Graduated Bristol University 2004 Internship at Donnington Grove Equine Hospital 2007-8 Surgical residency then lectureship at Edinburgh University 2008-11 Awarded Msc. by Research with distinction 2011 “Investigating the effects of antibiotics on the gene expression of equine bone marrow derived mesenchymal stromal cells” Awarded ECVS Diploma in Equine Surgery 2012 Currently one of 5 surgeons at Liphook Equine Hospital LIPHOOK EQUINE HOSPITAL
Equine referral hospital, ambulatory practice and commercial laboratory ◦ 5 ECVS surgeons ◦ 3 ECEIM medicine specialists Radiography, ultrasonography, scintigraphy, MRI, CT unit currently being installed Varied equine population LIPHOOK EQUINE HOSPITAL
Major cause of lameness, poor performance and lost training days Economic impact Welfare implications Sites of injury often related to athletic discipline LIPHOOK EQUINE HOSPITAL
Racehorses ◦ 10% clinical incidence (Walsh et al. 2013) ◦ 1.8 joint injuries/100 horse months (Reed et al. 2012) ◦ 33% metacarpophalangeal OA (Neundorf et al. 2010) with incidence increasing with age on PME General population ◦ 13.9% in the GB horse population (Ireland et al 2013) ◦ 97% in geriatric population >30 yo (Ireland et al 2012) as assessed by decreased range of motion LIPHOOK EQUINE HOSPITAL
Good Question! “a group of disorders characterised by a common end stage: progressive deterioration of the articular cartilage accompanied by changes in the bone and soft tissues of the joint” (McIlwraith 2005) LIPHOOK EQUINE HOSPITAL
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Same end stage, different pathways! LIPHOOK EQUINE HOSPITAL
Abnormal stresses Normal stresses on on normal cartilage abnormal cartilage Morphologic breakdown of articular cartilage LIPHOOK EQUINE HOSPITAL
Joint Cyclic athletic Loss of stability incongruity trauma Abnormal stresses Subchondral bone remodelling Direct damage Physical cell to collagen (chondrocyte) matrix damage Enzymatic degradation Matrix and decreased synthesis proteoglycan of PG and collagen loss Cartilage breakdown
Athletic Osteochondrosis trauma Age Inflammation Abnormal (Synovitis and cartilage capsulitis) Enzymatic Decreased degradation of matrix proteoglycan synthesis and collagen Cartilage breakdown
Trauma Synoviocytes Subchondral bone Il-1 TNFα Prostaglandin Free radicals Chondrocytes Matrix Proteinase Collagenase metalloproteinases Hyaluronan degradation Matrix degradation LIPHOOK EQUINE HOSPITAL
Synovitis Subchondral bone remodelling Intra-articular fracture Osteochondral fragmentation Periarticular soft tissue injury LIPHOOK EQUINE HOSPITAL
Increasingly implicated in the pathogenesis of OA (Sutton et al. 2009) Inflamed synoviocytes are a rich source of inflammatory mediators ◦ Prostaglandins ◦ Cytokines ◦ Matrix metalloproteinases LIPHOOK EQUINE HOSPITAL
Subchondral bone is responsible for 30-50% of impact absorption (cartilage 1-2%) and maintenance of joint congruity (Radin et al. 1970) During training the bones are subjected to repeated cyclical loading leading to increased bone density as per Wolff’s law The point at which this physiological response becomes pathological is poorly understood (Boyde 2003) LIPHOOK EQUINE HOSPITAL
Histopathological changes ◦ Thickening of subchondral bone plate ◦ Trabecular thickening ◦ Microvascular necrosis ◦ Osteocyte death ◦ Microcrack formation ◦ Cartilage erosion and loss LIPHOOK EQUINE HOSPITAL
Significant cause of lameness ◦ Racehorses ◦ Sports horses Unknown but suspected role in the pathogenesis of osteoarthritis (Kawcak et al. 2001, Cruz and Hurtig 2008) Often difficult to diagnose ◦ Subtle lameness ◦ Minimal localising signs ◦ Variable response to joint blocks LIPHOOK EQUINE HOSPITAL
Clinical signs Diagnostic analgesia Radiography Ultrasonography Biomarkers Scintigraphy MRI/CT Arthroscopy LIPHOOK EQUINE HOSPITAL
Effusion Heat Soft tissue swelling Reduced ROM Pain on flexion Lameness None…. LIPHOOK EQUINE HOSPITAL
Essential for correct localisation of lameness as radiographic changes are often clinically insignificant Lameness is usually reassessed 10 and 30 minutes post injection of mepivicaine Volume of local anaesthetic varies depending on joint size ◦ Tarsometatarsal joint 2-4ml ◦ Fetlock/carpus 10ml ◦ Stifle 20-30ml each compartment LIPHOOK EQUINE HOSPITAL
Not an exact science! A lower level of improvement may still be significant compared to perineural nerve blocks eg 50% Some significant pathology may respond only partially to diagnostic analgesia eg subchondral bone pain, periarticular soft tissue injury Response to diagnostic analgesia is no predictor of response to IA medication Beware trying to block out a positive response to flexion LIPHOOK EQUINE HOSPITAL
Most commonly performed imaging modality for OA diagnosis Uses ◦ Identification of osteochondral fragmentation ◦ Some indication of disease severity ◦ Allows monitoring of disease progression Limitations ◦ Radiographic changes are no indicator of pain ◦ Provides limited information on soft tissues/subchondral bone ◦ Changes develop at a variable rate after injury ◦ Poor indicator of prognosis LIPHOOK EQUINE HOSPITAL
Periarticular osteophyte Osteochondral fragmentation LIPHOOK EQUINE HOSPITAL
Subchondral bone sclerosis Loss of joint space Bone lysis Ankylosis LIPHOOK EQUINE HOSPITAL
Under used in OA assessment Safe and easily performed Good for detection of soft tissue injury, osteochondral fragmentation, some cartilage injury Limitations ◦ Requires operator experience ◦ Can only assess peripheral structures LIPHOOK EQUINE HOSPITAL
Synovial hypertrophy Capsular thickening Specific soft tissue injury Osteochondral fragmentation Cartilage defects LIPHOOK EQUINE HOSPITAL
Serum biomarkers could potentially identify the early stages of OA (Frisbie et al 2008) ◦ Osteocalcin ◦ GAG ◦ Collagen synthesis/degradation Yet to be fully validated in clinical practice but show some promise in experimental studies LIPHOOK EQUINE HOSPITAL
IRU highly variable depending on bone involvement Non specific indicator of bone injury IRU poorly correlated with injury in some locations eg stifle LIPHOOK EQUINE HOSPITAL
MRI represents a significant advancement in our diagnosis and understanding of subchondral bone pathology MRI: standing low field up to carpus/tarsus Most comprehensive imaging modality available for fetlock pathology (Powell 2012) ◦ 131 horses. Mostly with inconclusive findings on radiography ◦ 35% had early fracture pathology ◦ 54% had palmar/plantar osteochondral disease LIPHOOK EQUINE HOSPITAL
But, MRI still provides only limited assessment of articular cartilage, even with high field MRI LIPHOOK EQUINE HOSPITAL
Still remains the ’gold standard’ for evaluation of articular cartilage Opportunity for lesion debridement Indications ◦ Osteochondral fragmentation ◦ Articular fracture repair ◦ Periarticular soft tissue injury ◦ Poor response to IA medication LIPHOOK EQUINE HOSPITAL
Expensive compared with IA therapy In most cases requires general anaesthesia Does not allow access to some significant areas of pathology ◦ Subchondral bone ◦ Anatomical ‘blind spots’ LIPHOOK EQUINE HOSPITAL
Despite advances in our knowledge of the pathogenesis of OA, damage to articular cartilage is still irreversible LIPHOOK EQUINE HOSPITAL
Early identification of pathology Treatment of underlying primary causes ◦ Osteochondral fragmentation ◦ OCD ◦ Soft tissue injury Reduction of inflammatory mediators Repair of cartilage damage Modification of exercise LIPHOOK EQUINE HOSPITAL
What are the goals of therapy? 1 - Improve clinical signs (symptom modification) ◦ Reduce lameness ◦ Reduce effusion ◦ Improve range of motion 2 - Halt disease progression (disease modification) 3 - Allow ongoing athletic performance 4 - Avoid catastrophic fracture LIPHOOK EQUINE HOSPITAL
Symptom modifying NSAIDS Corticosteroids drugs (SMOADS) ACS Gene therapy Hyaluronic acid Disease modifying drugs PSGAG’s (DMOADS) Green lipped mussel
Rest Physiotherapy Neutraceuticals Systemic medication Intra-articular medication Surgery ◦ Arthroscopy ◦ Arthrodesis LIPHOOK EQUINE HOSPITAL
Allows targeted therapy at the site of pathology with reduced systemic side effects Requires positive identification of affected joints Beneficial effects persist after detection times Repeatable Low morbidity Financially viable LIPHOOK EQUINE HOSPITAL
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