Small Animal Orthopedic Radiology

Lecture 4 –

Fracture Complications

Diseases Affecting the Joints VCA 341 Fall 2011

Andrea Matthews, DVM, Dip ACVR Assistant Professor of Radiology

Complications of Fracture Healing

Malunion

Delayed union

Nonunion Viable Nonviable

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Complications of Fracture Healing

Malunion Healed but in an abnormal anatomic

position Malunion involving joints will lead to

osteoarthrosis Many malunions in immature dogs are

difficult to recognize after 6-12 months due to extensive remodeling

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Complications of Fracture Healing

Malunion

Complications of Fracture Healing

Delayed union

Fracture is healing but not as quickly as expected

Duration compared to similar fractures and fixation

Subjective assessment – healing is dependant on many factors

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Complications of Fracture Healing

Delayed union

Complications of Fracture Healing

Causes of delayed union

Severe soft tissue damage (poor blood supply) Distracted or over-riding fragments Improper or inadequate reduction or fixation Significant periosteal stripping Removal of large bone fragments Obstruction or destruction of blood supply by implant

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Complications of Fracture Healing

Nonunion

Fracture that has not healed with no evidence of progression to bony union

Different from delayed union in that healing will not proceed without intervention

Often muscle atrophy and lameness Fragment motion may be present pseudoarthrosis Distal radius and ulna of small breed dogs one of most

common sites

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Complications of Fracture Healing

Nonunion

Viable• Hypertrophic

• Oligotrophic Nonviable (uncommon)

• Dystrophic

• Necrotic

• Defect

• Atrophic

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Complications of Fracture Healing

Viable (reactive or vascular) nonunion1. Hypertrophic

• Excessive lysis at fracture site

• Excessive, nonbridging callus formation (“elephant” or “horse foot”)

• Sclerosis of bone fragments

• Can have angular limb deformity

2. Oligotrophic• Little to no callus - Bridging of fracture fragments with

fibrous tissue

• Difficult to differentiate from nonviable nonunions

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Hypertophic Nonunion

Note the widening of the fracture gap

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Hypertophic Nonunion

Note the excessive, non bridging callus

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Hypertophic Nonunion

Note the sclerotic fracture ends

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Oligotrophic Nonunion

Note the rounded fracture ends, sealed medullary

cavity of the distal fragment and minimal

callus formation

Clin Tech Small Anim Pract 2004; 19:168-179

Complications of Fracture Healing

Nonviable nonunion1. Dystrophic

Poor vascular supply to at least one fracture fragment Little to no callus; lucent fracture gap

2. Necrotic Lack of blood supply causes sequestrum formation Bone fragment retains sharp edges and is sclerotic

3. Defect Large fracture gap cannot be bridged by callus

4. Atrophic Usually progression from one of the other types of

nonunions Little to no callus, loss of vascularity, rounding of bone

margins

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Defect Nonunion

Note the lack of callus formation, resorption and sclerosis of the fracture margins as well as the widening of the fracture gap

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Atrophic Nonunion

Note the large fracture gap, no callus, and varying degrees

of sealing of the medullary cavities

Clin Tech Small Anim Pract 2004; 19:168-179

Diseases Affecting the

Joints

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Osteoarthrosis

Also known as Degenerative Joint Disease

A non-inflammatory disorder of synovial joints = osteoarthrosis Osteoarthritis implies inflammation

Slowly progressive degenerative condition

Occurrence Most frequent in the weight bearing joints

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Osteoarthrosis

Roentgen signs Intracapsular soft tissue swelling due to joint

effusion and/or synovial proliferation Usually first pathologic change

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Osteoarthrosis

Roentgen signs Periarticular osteophytes result from articular

cartilage proliferation in the non-weight bearing areas of the joint

Excessive cartilage proliferation outgrows its nutrient supply the cartilage dies it is invaded by vessels and replaced by bone seen radiographically

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Osteoarthrosis

Roentgen signs Joint space alteration

• Decreased size of joint space due to destruction of the articular cartilage

• Alteration in joint space width is best demonstrated on weight bearing views

Artificial narrowing of joint spaces• Obliquity of joints

• Joints that are not in the center of the film

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Osteoarthrosis

Apparent joint space narrowing

Could be real…may be an artifact

See of dogs leg is straight relative to plate to know if real…

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Osteoarthrosis

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Osteoarthrosis

Osteoarthrosis

Roentgen signs Subchondral sclerosis results from trabecular

hypertrophy, compression and collapse of weakened subchondral bone• Also called eburnation

Subchondral osteolysis caused by necrosis of the bone following loss of articular cartilage

Subchondral bone cysts are formed by proliferation of synovium invading the subchondral bone

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Osteoarthrosis

Subchondral osteolysisSubchondral osteosclerosis

Osteoarthrosis

Roentgen signs “Joint mice” or “joint bodies”

are pieces of articular cartilage that detach and are free within the joint. They are visible radiographically when mineralized

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Cranial Cruciate Ligament Rupture

Anatomy and Function Medial aspect of lateral femoral condyle to

intercondylar area of tibia Cranial cruciate ligament (CCL) prevents cranial

displacement of the tibia, limits internal rotation of the tibia and prevents hyperextension of the stifle

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Occurrence Females > males Young athletic dogs and middle age,

over-weight dogs Acute, non weight-bearing lameness

Roentgen signs Tibia may be displaced cranially

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Cranial Cruciate Ligament Rupture

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Cranial Cruciate Ligament Rupture

CCL rupture Normal

Roentgen signs Intracapsular swelling

• Effusion and/or synovial proliferation

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A – displacement of infrapatellar fat pad

B – displacement of fascial planes caudal to joint

Cranial Cruciate Ligament Rupture

Cranial Cruciate Ligament Rupture

Roentgen signs Secondary osteoarthrosis

• Osteophytes on patella, adjacent to trochlear groove of femur, margins of tibial plateau and fabellae

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Roentgen signs May seen an avulsion fracture in the cranial joint

space

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Avulsion fragment

Cranial Cruciate Ligament Rupture

Septic Arthritis

Occurrence Direct inoculation, extension from soft tissue or

bone infections or hematogenous in origin Can also occur in conjunction with other systemic

diseases (Mycoplasma, Leishmania, etc)

Roentgen signs Early infection may show only soft tissue swelling Once bony changes are apparent, the degree of

damage is significant

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Septic Arthritis

Roentgen signs Osteolysis is often seen early in the disease

process, resulting in rough or irregular articular margins

Usually multiple joint surfaces involved Degree of subchondral erosion is much more

severe than with osteoarthrosis In chronic cases, may see periosteal reaction and

osteophytes

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Septic Arthritis

Osteolysis of subchondral bone

Intracapsular swelling

Columnar periosteal reaction

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Septic Arthritis

Osteolysis of subchondral bone

and ulna

Intracapsular swelling

Erosive Polyarthritis

Etiologies Rheumatoid arthritis

• Most common type in dogs

• Small breeds, especially Shetland sheepdog and poodle

Polyarthritis of greyhounds Periosteal proliferative polyarthropathy (cats)

• Older cats

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Erosive Polyarthritis

Roentgen signs Intracapsular soft tissue swelling

only radiographic changes for first few weeks

Cyst-like lucencies in the subchondral bone at the joint capsule attachments and later at the articular margins

Destruction of joint surfaces

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Erosive Polyarthritis

Roentgen signs Narrow joints spaces due to loss

of articular cartilage Subluxation and luxation of the

joints due to destruction of the ligaments

Suspect rheumatoid arthritis radiograph both carpal and tarsal joints as well as any joint that is swollen and painful

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Erosive Polyarthritis

Non-Erosive Polyarthritis

Etiologies Systemic lupus erythematosus (SLE) Idiopathic polyarthritis Feline nonerosive polyarthritis Arthritis associated with chronic infection Polyarthritis/polymyositis syndrome Polyarthritis/meningitis syndrome Plasmacytic-lymphocytic synovitis

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Non-Erosive Polyarthritis

Roentgen signs Intracapsular swelling (joint effusion and/or

increased synovial mass) No osteolysis is noted Multiple joints involved Common sites include carpus, tarsus and stifle

joints

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Non-Erosive Polyarthritis

Neoplasia of the Joints

Occurrence Middle aged to older medium to large breed dogs Rare in the cat From undifferentiated mesenchymal cells of synovium Stifle and elbow are most commonly affected joints

Roentgen signs Early

• Intracapsular and/or extracapsular swelling Later

• Can affect both sides of the joint due to secondary bone involvement

Metastasis to regional lymph nodes and lungs

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Neoplasia of the Joints

Synovial cell sarcoma

Neoplasia of the Joints

Most common joint neoplasia Histiocytic sarcoma Synovial myxoma Synovial cell sarcoma Other neoplastic conditions that can affect the

joints• Rhabdomyosarcoma• Fibrosarcoma• Chondrosarcoma• Malignant fibrous histiocytoma• Liposarcoma• Undifferentiated sarcoma…

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The End!