Introduction to Orthopedic Radiology Kari L Anderson DVM DACVR CVM 6103 Fall Semester 2008 Office C350 Phone 612 625 3762 office 612 625 1200 radiology Email kla umn edu Introduction Radiography is an important diagnostic tool for the detection and diagnosis of musculoskeletal diseases Radiographs permit localization and characterization of a lesion It is imperative to obtain at least two views made at right angles in order to evaluate a three dimensional object the patient with a two dimensional image the radiograph Occasionally a lesion is seen only on one view or perhaps a special projection is necessary to demonstrate the abnormality Poor radiographic technique can lead to inappropriate or missed diagnoses underexposed overexposed improper development inadequate positioning of the animal insufficient number of films etc Other imaging modalities will often provide further information These modalities include computed tomography CT magnetic resonance imaging MRI contrast radiographic procedures arthrogram fistulogram or nuclear medicine The basic radiographic interpretation is recognition of altered size shape margination opacity position distribution and number Radiographic interpretation of musculoskeletal disorders is based upon knowledge of normal anatomy If one cannot decide if a finding is normal it is often helpful to obtain a similar radiographic view of the opposite limb In cases of generalized or bilateral disease a textbook radiographic atlas or radiographs of a similar age and breed of animal may be necessary Several anatomic variations occur that may be confused for a disease process Brief Overview of Normal Long Bone Anatomy Most of the bones of the skeleton develop by endochondral ossification ossification of preformed cartilage matrix Long bones typically develop from a primary center of ossification diaphysis and two secondary centers of ossification epiphyses Many bones also have tertiary centers of ossification from which processes and apophyses develop CVM 6103 MS Radiology Notes Terminology epiphysis the region at each end of the bone This is usually cartilaginous at birth and is therefore not recognized radiographically The outer surface of the epiphysis is covered by articular cartilage physis growth plates the radiolucent cartilage bands separating the epiphysis from the metaphysis seen in skeletally immature animals This is the area where longitudinal growth occurs physeal scar the radiopaque band which represents the junction of the epiphysis and the metaphysis in the skeletally mature animal metaphysis the region of bone opacity adjacent to the physis at each end of the diaphysis This area represents newly formed cancellous bone formed at the physis diaphysis the shaft or body of the bone It is seen as a band of dense compact bone surrounding a more radiolucent medullary cavity apophysis secondary center of ossification This forms later than primary centers of ossification and is a site of muscle ligament attachment ex supraglenoid tubercle medial humeral epicondyle olecranon process greater trochanter tibial tuberosity medial malleolus trabeculae the fine lacy pattern of radiopacity associated with cancellous bone seen in the epiphysis and metaphysis of long bones periosteum the outer covering of the cortex of the bone This is composed of an outer fibrous layer and an inner cellular layer which has osteoblastic and osteoclastic properties This serves as the attachment surface of tendons muscles and ligaments endosteum this is a single layer that lines the medullary cavity This also has osteoblastic and osteoclastic properties 2 CVM 6103 MS Radiology Notes It is important to know the positions of ossification centers and the physeal closure times in the young animal Physes and subsidiary ossification centers may be mistaken for abnormalities Bone Physis Date of Closure Humerus Proximal Medial epicondyle Proximal Distal Proximal apophysis Distal Anconeal Process Femoral head Distal Proximal Tibial Crest Distal 10 months 6 months 8 months 9 months 7 months 10 months 5 months 8 months 8 months 10 months 10 months 9 months Radius Ulna Femur Tibia approximate dates of selected physeal closure in dogs Young animals appear to have very wide joint spaces because of the relatively thick layer of cartilage on articular surfaces Form follows function Each depression irregularity protrusion and bump on a bone is there for a reason muscular attachment ligamentous connection etc Be able to associate radiographic landmarks with these attachments Brief Overview of Synovial Joint Anatomy Synovial or diarthrodial joints consist of a joint cavity joint capsule synovial fluid and articular cartilage Certain joints may also have a meniscus and or ligament The joint capsule consists of a synovial membrane that lines the joint cavity and an outer fibrous capsule The ends of the articulating surfaces are covered with articular cartilage appears as soft tissue opacity beneath which lies a thin plate of dense subchondral bone All of the soft tissues of the joint will be indistinguishable radiographically 3 CVM 6103 MS Radiology Notes Terminology of Radiographic Views Refer to the preceding diagram for the correct nomenclature in naming radiographic views The descriptors dorsal palmar and plantar are used for that portion of the limb distal to the radius and tibia Palmar is used in reference to the forelimbs and plantar is used in reference to the hindlimbs The descriptors cranial and caudal are used in reference to the portion of the limb proximal to the carpus and tarsus When combining descriptive terms the rules are as follows medial and lateral are subservient when used with other descriptive terms rostral cranial and caudal precede other descriptive terms proximal limb dorsal palmar and plantar precede other descriptive terms distal limb Describe the view by designating anatomically the point of entry followed by the point of exit of the x ray beam For example a Dorsoplantar D Pl view of the tarsus indicates that the beam entered the dorsal aspect of the tarsus and exited the plantar aspect of the tarsus Oblique radiographs are named in the same manner as the standard views Angles of obliquity should be designated for completeness although in the clinic we generally 4 CVM 6103 MS Radiology Notes leave out this information For example a Dorsomedial palmarolateral oblique DMPaLO view of the carpus indicates that the beam entered the dorsomedial aspect of the carpus and