Small Animal Orthopedic Radiology Lecture 3 – Acquired Bone Diseases Fracture Healing and Evaluation VCA 341 Fall 2011 Andrea Matthews, DVM, Dip ACVR Assistant Professor of Radiology

Hypertrophic Osteopathy (HO) Occurrence Middle aged to older dogs Usually due to concurrent thoracic or abdominal disease Often pulmonary neoplasia; also reported with pulmonary abscesses, bronchopneumonia, bacterial endocarditis, heartworm disease, esophageal pathology, as well as hepatic and bladder neoplasia Gradual or occasional acute onset in lameness Animal reluctant to move Symmetric, non-edematous, firm swelling of the distal limbs Increased blood flow to the extremities in affected animals

Hypertrophic Osteopathy (HO) Roentgen signs Solid, irregular periosteal reaction Palisading or columnar new bone formation Never confined to a single location - Usually bilaterally symmetrical and generalized

Hypertrophic Osteopathy (HO) Roentgen signs Begins on the abaxial surface of the 2nd and 5th metacarpal/metatarsal bones and progresses proximally Spares the small bones of the carpus and tarsus But is seen on the accessory carpal bone and calcaneus

Hypertrophic Osteopathy (HO) Location of periosteal reaction is diaphysis of tubular bones Radiographs of the thorax and abdomen should be obtained to investigate for underlying disease

Fungal Osteomyelitis Occurrence Usually hematogenous in origin Typically seen in young to middle-aged dogs May be seen in any breed; however, more common large breeds such as working or sporting breeds Usually hematogenous in origin Often systemically ill Fever Lethargy Anorexia Lymphadenopathy, etc…

Fungal Osteomyelitis Roentgen signs Differential Diagnoses Variable radiographic appearance Both lytic and productive changes Periosteal reaction usually semi-aggressive Osteolysis may extend through the cortex Usually in the metaphyseal region of long bones May be joint involvement with extensive bone destruction Often polyostotic but can be monostotic Differential Diagnoses Primary bone tumors Metastatic bone tumors

Fungal Osteomyelitis

Fungal Osteomyelitis and arthritis

Bacterial Osteomyelitis Occurrence Usually secondary to… Direct inoculation (bite wound, open fracture, or surgery) Extension from soft tissue injury May be hematogenous in young or immunocompromised animals Hematogenous route is much less common in small animals

Bacterial Osteomyelitis Roentgen signs Earliest stage No bony abnormalities, just soft tissue swelling May take 7-14 days before periosteal reaction visible Periosteal reaction typically solid and extends along shaft of diaphysis; however, can be lamellar to palisading/columnar

Bacterial Osteomyelitis Nonhematogenous origin Lesion location depends on affected area May affect multiple bones in the same limb Lucencies around surgical implants May see draining tract from surgical implant or foreign body Hematogenous origin Metaphyseal due to extensive capillary network Often multiple limbs affected (polyostotic) Differential Diagnoses Healing fracture Primary or metastatic bone tumor Fungal osteomyelitis

Bacterial Osteomyelitis

Primary Bone Tumors Occurrence Mostly large and giant breed dogs; no breed predilection Mean age = 7 years Bimodal distribution seen in animals as young as 6 months Slightly more common in male dogs May be associated with a previous fracture or metallic implant

Primary Bone Tumors Roentgen signs Radiographic appearance is variable Primarily osteoblastic Primarily osteolytic Combination of both Lytic and/or productive changes are aggressive in nature Typically monostotic Located often in metaphyseal region of a long bone Does not typically cross the joint

Primary Bone Tumors Osteosarcoma Chondrosarcoma Fibrosarcoma Most common primary bone tumor (>85%) “Away from the elbow, toward the knee” Chondrosarcoma Fibrosarcoma Hemangiosarcoma Differential diagnoses Osteomyelitis Metastatic neoplasia

Primary Bone Tumors

Fracture Evaluation and Bone Healing

Fracture Evaluation Initial radiographs Two orthogonal views (90o to one another) Include the joint proximal and distal to the fracture Determine joint involvement Special radiographic views may be necessary to determine the extent of the fracture Oblique, etc

Fracture Recognition Most are visible as abnormal radiolucent lines Some may not be as obvious Ex. Compression, non-displaced or pathologic fracture Occassionally, compression fractures may result in alteration in size or opacity, creating a summation opacity (more opaque than normal)

Fracture Recognition Non-displaced fractures May not be seen initially Seen days later when resorption of bone at fracture margins has occurred Some are recognized by presence of bony callus If clinical suspicion of fracture is high but equivocal  Nuclear medicine

Fracture Description Fracture types Open vs closed Incomplete vs complete Simple vs complex/comminuted Transverse, oblique or spiral Extra-articular, articular, compression, avulsion Displaced vs. non-displaced

Bone Healing Primary bone healing Occurs with rigid internal fixation Results in bony union through direct growth of haversian system across the fracture Minimal to no bony callus Cannot occur across a fracture gap Usually occurs with compression plate reduction

Primary Bone Healing Radiographic signs of primary bone union Lack of callus Gradual loss in opacity of fracture ends Progressive disappearance of fracture line

Most common type of fracture healing in small animals Bone Healing Secondary bone healing Lack of rigid internal fixation and excellent anatomic reduction Bone heals through initial deposition of fibrous tissue Callus formed by series of maturations Granulation tissue  cartilage  mineralized cartilage  replaced by bone Most common type of fracture healing in small animals

Secondary Bone Healing

Secondary Bone Healing

Bone Healing Factors that affect bone healing Fracture location Vascular integrity Degree of immobilization Fracture type Degree of anatomic reduction Degree of soft tissue trauma Degree of bone loss Type of bone involved Presence of infection Local malignancy Metabolic factors Age, breed, species Presence of systemic disease Steroid administration And on and on and on…

Initial Postoperative Evaluation Evaluate; Fracture alignment Degree of fracture reduction Needs to be at least 50% reduction of fracture margins Presence of joint incongruities Step deformities If fracture is articular Rotation of fracture fragments

Initial Postoperative Evaluation Evaluate; Placement of fixation devices With bone plate, ideally want 6 corticies engaged with cortical screws above and below the fracture site Pins of external fixator should be angled 65-70o to bone Not possible with all types of external fixators Cerclage wires should be of adequate size, be perpendicular to the long axis of the bone, be a minimum of 1 cm apart, be adequate in number and fit snugly against the cortex

Growth Plate Injuries Good prognosis Poorer prognosis Guarded prognosis

Growth Plate Injuries Occurrence Etiologies Trauma Severe hypertrophic osteodystrophy (HOD) Retained cartilaginous core Skeletally immature animals <1 year Prognosis Salter Harris Type I and II have better prognosis Type III and IV have poorer prognosis due to disturbance of resting cell layer Type V have guarded prognosis due to damage of proliferative zone

Growth Plate Injuries Roentgen signs Unilateral or bilateral Radiographs both limbs for comparison Affected physis may initially appear normal or may be closed Skeletal deformities Distal ulnar physis is commonly affected due to shape Often type V

Premature Distal Ulnar Physis Closure Roentgen signs Affected ulna is measurably shorter than contralateral side (unless bilateral) Styloid process of ulna may be separated from carpus May have cranial and/or medial bowing of radius Cortical thickening of the concave side of the radius (due to stress remodeling)

Premature Distal Ulnar Physis Closure Roentgen signs Distal radius is subluxated craniomedially from the radiocarpal bone Manus deviates laterally Carpal valgus Humero-ulnar joint space may be widened (subluxation) +/- osteoarthrosis

Premature Distal Ulnar Physis Closure Note widening of the humero-ulnar joint (black arrows) Note the UAP that can occur secondarily (green arrow)

Premature Distal Radial Physis Closure Roentgen signs Shortened length of the radius compared to contralateral side (unless bilateral) Increased radiocarpal joint space Increased humero-radial joint space (subluxation)

Radial physeal closure Growth Plate Injuries The elbow is key to determine origin of slowed growth Normal Radial physeal closure Ulnar physeal closure

Premature Distal Ulnar Physis Closure

Premature Distal Radial Physis Closure

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