Canine Panosteitis: Pathophysiology, Definition and Synonyms

Developmental Bone Diseases Overview

• These diseases are primarily inflammatory and common in younger breeds.
• They typically manifest during the growth phase of large and giant breed dogs.

Canine Panosteitis: Definition and Synonyms

• It is a disease of young dogs, characterized by lameness and bone pain.
• Endosteal bone production with occasional periosteal bone production is associated.
• Synonyms include enostosis, eosinophilic panosteitis, juvenile osteomyelitis, and osteomyelitis of young German Shepherd dogs.
• 80% of those affected are male.

Canine Panosteitis: Pathophysiology

• The exact cause is unknown but is suspected to be genetic, viral, or autoimmune
• An osseous compartment syndrome is involved.
• A protein-rich, high-calorie diet may be a potential cause, caution is advised against overfeeding.
• Excessive protein intake could lead to intraosseous edema.
• Secondary increased medullary pressure and ischemia occurs.
• This can cause death of bone marrow, and lead to endosteal bone thickening.
• New endosteal bone is formed as marrow invaded by bone trabeculae.
• This ailment affects the adipose bone marrow.

Canine Panosteitis: Clinical Presentation - Signalment and History

• Signalment includes mainly male, large-breed dogs, more frequently affecting young dogs under 2 years old.
• Older dogs in rare cases can be diagnosed
• The hallmark of panosteitis is shifting leg lameness which may shift from forelimb to hindlimb.
• Deep bone palpation elicits pain.
• Presentation can be acute lameness on a single limb.
• Many dogs with panosteitis will still bear weight.
• A history of chronic intermittent shifting leg lameness may be reported.

Canine Panosteitis: Physical Examination

• Gait analysis reveals single or multiple leg involvement, with the owner typically focusing on one leg.
• Lameness varies, often described as weight-bearing lameness of generally mild to moderate severity.
• Direct palpation of affected bones induces pain.
• Possible to be seen in dogs after growth has ceased.

Canine Panosteitis: Diagnostic Imaging and Findings

• Radiographic signs are typically progressive.
• Clinical signs can appear up to 10 days before radiographic changes are visible.
• Radiographs should be repeated in 7 to 10 days if initial imaging is normal because early stages are often normal.
• Radiographic findings show a widening of the nutrient foramen.
• Radiopaque patchy or mottled bone is detected forming "clouds" with medullary canal of bone trabeculae.
• Intramedullary radiopacity can be seen using radiography
• There is blurring and accentuation of trabecular patterns.
• Endosteal thickening occurs and represents inflammation.
• Periosteal new bone formation exists.

Canine Panosteitis: Treatment and Prognosis

• Medical treatment involves self-limiting disease management and resolves with or without treatment.
• Nonsteroidal anti-inflammatory drugs (NSAIDs) provide comfort.
• Exercise restriction is advised when the dog is lame and aids in pain management.
• Owner recurrence should be warned, as they are common
• Self limiting meaning the condition heals within 2 weeks
• Surgical intervention is generally not indicated.
• The long-term prognosis is excellent for complete recovery, typically within a couple of weeks.

Hypertrophic Osteodystrophy (HOD): Definitions and Etiology

• HOD is a disease disrupting metaphyseal trabeculae in the long bones of young and rapidly growing dogs.
• Synonyms include skeletal scurvy, canine scurvy, and Moeller-Barlow disease among others..
• The exact cause is unknown, but decreased levels of Vitamin C and excess dietary calcium are suspected in the etiology.
• Viral causes have been proposed

Hypertrophic Osteodystrophy (HOD): Etiology and Pathophysiology

• Recent history of GI or respiratory problems is typical.
• There may be a connection to distemper virus vaccination, specifically with certain protocols that can increase risk of developing HOD in Weimaraner puppies.
• Disturbance of metaphyseal blood supply occurs
• There are changes identified in the physis and adjacent metaphyseal bone, along with delayed ossification of the physeal hypertrophic zone and a widening of the physis.

Hypertrophic Osteodystrophy (HOD): Pathophysiology and Clinical Presentation

• No bone is formed on calcified cartilage.
• Inflammatory infiltration of neutrophils and mononuclear cells occurs instead of bone formation, with no eosinophils present.
• Osteoclastic resorption affects recently formed metaphyseal trabecular bone.
• Affects young, rapidly growing large-breed dogs at 3-4 months old, or earlier
• Males are more affected than females.
• Clinical signs usually appear between 3 to 4 months, but can be seen as early as 2 months.
• Weimaraners are at an increased risk.

Hypertrophic Osteodystrophy (HOD): Clinical Presentation and Physical Examination

• Acute onset of lameness may occur.
• Can be severely affected and may exhibit not walking.
• Other clinical signs include inappetence and lethargy accompanied with recent diarrhea preceding lameness.
• Mild to severe lameness is present in all four limbs, with severely affected animals are unable to stand or walk.
• Affected long bones are swollen, warm, and painful on palpation.
• Swelling is often present in all four limbs.
• Swelling in forelimbs may be more obvious, especially in distal radial metaphyses.

Hypertrophic Osteodystrophy (HOD): Differential Diagnosis and Radiographic Findings

• Rule outs for the differential diagnosis includes septic arthritis, septic physitis, & panosteitis
• Radiographic findings indicate an irregular radiolucent line on the metaphyseal side of the physis.
• A "double physis" hallmark exists.
• There is widening of the physis.
• Periosteal new bone formation develops as the diseases progresses, potentially spanning the active physis.
• Usually evidence is seen in multiple limbs.

Hypertrophic Osteodystrophy (HOD): Radiographic Findings

• Osteolysis on the metaphyseal side of active physis leads to the appearance of a "second growth plate."
• Radiological findings indicate increased bone opacity within femoral head showing femoral head deformity

Hypertrophic Osteodystrophy (HOD): Treatment and Prognosis

• The focus of treatment aims to be supportive.
• Analgesics aid in controlling pain with NSAIDs or opioids, as needed.
• Severely affected animals need intravenous fluid support, possibly corticosteroids, antibiotics, and Vitamin C.
• Antibiotics use should be considered given many bacterial infections
• It is a self-limiting disease.
• Most recover fully in 7 to 10 days; with possibility of relapes might occur.
• Euthanasia is considered for severe debilitation or multiple severe relapses due to the high cost, hospitalization, and animal pain.

Retained Ulnar Cartilaginous Core: Characteristics

• This conditions involves cones or flames of growth plate cartilage projecting from the distal ulnar growth plate into the distal metaphysis.
• It's also named retained endochondral cartilage for core reasons.
• The core is formed of retrained hypertrophic chondrocytes.
• This condition can affect large to giant immature canines.

Retained Ulnar Cartilaginous Core: Manifestation and Forelimb Deformities

• A growth plate manifestation of osteochondrosis (OC) can be possible.
• It may be associated with reduced ulnar length growth, causing cranial bowing of the radius, rotation, and valgus deviation of the forepaw.
• Possible to be identified as premature closure of distal ulnar & radial growth plates
• Those who develop this may develop carpal valgus with feet that point outwards and carpus that points inward

Retained Ulnar Cartilaginous Core: Diagnosis and Radiographic Findings

• Radiographs should pinpoint the cause of deformity. _ A radiolucent core (triangle) can be seen of cartilage in distal ulnar metaphysis.with a sclerotic zone that extends 3-4 cm into the metaphysis.
• No correlation between size of lesion, histopathology, & severity of forelimb deformity.

Retained Ulnar Cartilaginous Core: Treatment Options

• No treatment is given when there's no forelimb deformity.
• Surgical correction may be necessary if moderate to marked forelimb deformities are present.
• Patients are to be prescribed with a balanced-controlled diet.
• Cores may disappear spontaneously in time.

Legg-Calve-Perthes Disease: Definition and Synonyms

• It is a noninflammatory aseptic necrosis of femoral head in young patients before capital femoral physis closure.
• Synonyms: osteochondritis dissecans of femoral head, avascular necrosis of femoral head.

Legg-Calve-Perthes Disease: Pathophysiology and Proposed Theories

• Collapse of the femoral epiphysis occurs due to interruption of blood flow.
• Etiology is considered unknown.
• Theories for the disease include hereditary factors, hormonal influence, anatomic conformation, intra-capsular pressure, & infarction of femoral head.
• Autosomal recessive gene is possible

Legg-Calve-Perthes Disease: Pathophysiology Part 2

• A lack of vascular supply to the femoral head occurs in young animals.
• Epiphyseal vessels surface along the femoral neck and feed nourishment to the femoral epiphysis.
• Metaphyseal vessels do not cross the physis
• Synovitis or sustained abnormal limb position can increase intra-articular pressure.
• Fragile veins collapses due to their vulnearability to pressure, and this leads to necrosis which can collapse fragiles veins

Legg-Calve-Perthes Disease: Pathophysiology Part 3

• Cell death and bone substance weakening occurs, triggering the reparative process during revascularization.
• Normal physiologic weight-bearing forces can cause collapse & fragmentation of involved femoral epiphysis.
• Incongruence of femoral epiphysis & acetabulum contributes to degenerative joint disease (DJD).
• The fragmentation and DJD causes pain & lameness.

Legg-Calve-Perthes Disease: Clinical Presentation - Signalment

• Seen in young, small-breed dogs generally under 10 kg.
• Peak incidence between 6 to 7 months old with a range of 3 to 13 months.
• Males and females are affected equally.
• Mainly unilateral, with only 10% to 17% of affected animals will have bilateral disease.

Legg-Calve-Perthes Disease: Clinical Presentation - History

• Slow-developing cases of weight-bearing lameness develop to a more severe state.
• Lameness can progress to non-weight bearing (NWB) states.
• Could have acute onset
• Sudden collapse of epiphysis can occur
• Irritability, reduced appetite, plus chewing at skin over hip are other identifiers.
• Might present as acute presentation

Legg-Calve-Perthes Disease: Physical Examination

• Hip joint pain exists
• Those with advanced disease experience limited range of motion (ROM), muscle atrophy, & crepitus.
• Should be rule outs for physeal trauma & medial patella luxation (MPL).

Legg-Calve-Perthes Disease: Diagnostic Imaging

• Femoral head deformity is diagnostic using radiographs.
• Other findings display femoral neck shortening &/or lysis and foci of decreased bone opacity in femoral epiphysis

Legg-Calve-Perthes Disease: Medical Management

• In early stages of the condition is made, medical management if not painful.
• This includes medical management, rehabilitation and medications
• Medical treatments include
• Limited weight bearing during limit bearing via ex)swimming is given to revascualrize
• Conservative treatment incorporates anti-inflammatory medication (NSAIDs) along with limited leash of NWB
• Swimming helps to provide pain relief in small percentage of dogs.

Legg-Calve-Perthes Disease: Medical & Surgical Management

• Diagnosis of disease made after the collapse of epiphysis is when surgery is only the option
• Recommended for dogs with persistent pain and/or functional disability
• This intervention can provide pain relief and restore limb function.
• Surgical management includes the removal of the femoral head and neck (FHO).
• Follow-up care is required for FHO

Legg-Calve-Perthes Disease: Postoperative Care and Prognosis

• Post-op includes limb usage directly after surgery which incorporates rehabilitation exercises
• NSAIDs are subscribed and given to encourage early function by easing their function to walk more.
• Passive flexion-extension of hip is performed 2x daily when patient allows and is recommended
• Good prognosis is possible after FHO of Small affected dogs.
• Poor results are likely when non weight exists or when there's a severe preoperative muscle atrophy
• Can have some light intermittent lameness, specially when there's heavy exercise or period of inactivity occurs.

Additional Information

• Gait analysis can be used as a first step for orthopedic case diagnosis.
• Jump Down Syndrome refers to a fragmented coronoid process of the ulna.
• Osteodystrophy involves abnormal bone formation or remodeling, leading to bone deformities, exemplified by HOD.
• Osteochondrosis involves cartilage destruction or issues with endochondral ossification, exemplified by OCD.

Overview of developmental bone diseases common in young, large-breed dogs. Focus on Canine Panosteitis: its definition, synonyms, and pathophysiology. The exact cause is unknown but may be genetic, viral, or autoimmune.