Medical School · Year 4 · Radiology · includes a quiz and discussion video
Musculoskeletal Imaging
Year 4: Radiology Elective
Learning Objectives
By the end of this seminar, students will be able to:
- Apply a systematic approach to skeletal radiograph interpretation using the ABCS method to evaluate alignment, bones, cartilage spaces, and soft tissues
- Describe and classify fractures using standard terminology including location, type, displacement, and angulation
- Identify characteristic fracture patterns in the upper and lower extremities and understand their mechanisms and clinical significance
- Recognize arthritis patterns on radiography and MRI and distinguish osteoarthritis from inflammatory arthropathies
- Evaluate bone tumors using imaging features that suggest benign versus aggressive lesions and identify common primary tumors
- Select appropriate musculoskeletal imaging modalities for specific clinical scenarios including fractures, joint pathology, and soft tissue masses
I. Radiograph Interpretation
Systematic evaluation of musculoskeletal radiographs follows the ABCS approach that ensures comprehensive assessment of all skeletal structures. Alignment is assessed first, evaluating the anatomic relationships between bones at joints and along the length of long bones. Bones are examined for cortical integrity, medullary density, periosteal reaction, and trabecular architecture. Cartilage is indirectly assessed through joint space width, which reflects the combined thickness of the articular cartilage on opposing surfaces. Soft tissues are evaluated for swelling, calcification, foreign bodies, and fat planes that may be displaced or obliterated by pathology.
Technical assessment ensures that radiographic quality is adequate for diagnosis before pathology is evaluated. Patient identification must be confirmed and laterality verified. A minimum of two views obtained at ninety degrees to each other is required for most skeletal evaluations to avoid missing injuries visible only in one projection. Penetration should be appropriate to visualize both cortical and trabecular bone detail, and patient positioning should follow standard techniques to enable comparison with normal anatomy and prior examinations.
Bone evaluation includes assessment of cortical integrity, looking for subtle breaks or step-offs that may indicate fracture. The medulla should demonstrate normal trabecular pattern and density, with focal lucency or sclerosis suggesting tumor, infection, or metabolic disease. Periosteal reaction, visible as new bone formation along the outer cortical surface, indicates underlying pathology and may appear solid, lamellated, or aggressive depending on the process. The overall bone density should be assessed, with diffuse osteopenia suggesting osteoporosis or other metabolic bone disease.
Joint assessment evaluates the articulating surfaces for congruity and the joint space for uniform width. Narrowing of the joint space indicates cartilage loss and may be uniform as in inflammatory arthritis or non-uniform as in osteoarthritis. The subchondral bone is evaluated for sclerosis, cysts, and erosions that characterize different arthropathies. Periarticular structures including osteophytes, calcifications, and soft tissue swelling provide additional diagnostic information about the underlying joint pathology.
<image>Panel A: Normal knee radiograph demonstrating the ABCS evaluation approach with annotations. Panel B: Comparison of adequate and inadequate radiographic technique affecting diagnostic quality. Panel C: Periosteal reaction patterns from benign solid reaction to aggressive sunburst pattern. Panel D: Joint space narrowing with subchondral changes in osteoarthritis.</image>
II. Fracture Description
Fracture description follows standardized terminology that enables clear communication between radiologists, emergency physicians, and orthopedic surgeons. The location is specified by bone, anatomic region within the bone such as proximal, mid-shaft, or distal, and relationship to specific landmarks. The fracture type describes the orientation and pattern of the break, including transverse, oblique, spiral, and comminuted configurations. Displacement describes the position of the distal fragment relative to the proximal fragment in terms of direction and percentage of bone width. Angulation describes the direction in which the apex of the fracture angle points.
Special fracture types have specific mechanisms and clinical implications that inform treatment decisions. Pathologic fractures occur through abnormal bone weakened by tumor, infection, or metabolic disease and often occur with minimal trauma. Stress fractures result from repetitive loading that exceeds the bone's ability to remodel and may not be visible on initial radiographs. Avulsion fractures occur when a tendon or ligament pulls a fragment of bone away from its attachment site. Pediatric fractures include greenstick fractures with cortical disruption on only one side and torus or buckle fractures with cortical deformation without complete break.
The distinction between open and closed fractures has critical implications for management and infection risk. Open fractures have communication between the fracture site and the external environment through a break in the overlying skin. Radiographic signs suggesting an open fracture include air in the soft tissues adjacent to the fracture site. All open fractures require urgent surgical debridement and irrigation to prevent infection. Closed fractures maintain intact soft tissue coverage but may still be associated with significant soft tissue injury requiring careful assessment.
Fracture healing proceeds through predictable phases that can be monitored radiographically. The inflammatory phase occurs immediately and is characterized by hematoma formation and soft tissue swelling. Soft callus forms over weeks as granulation tissue organizes and begins to bridge the fracture gap. Hard callus develops as the soft callus mineralizes and becomes visible radiographically as fuzzy periosteal new bone. Remodeling continues for months to years as the callus matures and excess bone is resorbed. Complications include delayed union, nonunion with persistent fracture gap, and malunion with healing in abnormal position.
<image>Panel A: Fracture types illustrated including transverse, oblique, spiral, and comminuted patterns. Panel B: Avulsion fracture of the tibial tuberosity demonstrating tendon attachment site injury. Panel C: Open fracture with subcutaneous air visible on radiograph indicating soft tissue communication. Panel D: Fracture healing progression showing callus formation and remodeling over time.</image>
III. Upper Extremity Fractures
Shoulder fractures encompass injuries to the clavicle, proximal humerus, and scapula, each with characteristic mechanisms and treatment considerations. Clavicle fractures most commonly occur at the middle third where the bone is thinnest and lacks muscular attachment. Proximal humerus fractures are classified using the Neer system based on involvement of the anatomic neck, surgical neck, greater tuberosity, and lesser tuberosity. Greater tuberosity fractures often result from rotator cuff avulsion and may be associated with shoulder dislocation. Scapular fractures typically result from high-energy trauma and should prompt evaluation for associated thoracic injuries.
Elbow fractures require careful radiographic evaluation due to complex anatomy and the frequency of associated injuries. Radial head fractures are the most common elbow fracture in adults, typically resulting from a fall on an outstretched hand. Olecranon fractures result from direct trauma or triceps avulsion and demonstrate varying degrees of displacement. Supracondylar fractures are most common in children and carry significant risk of vascular injury to the brachial artery. The posterior and anterior fat pad signs indicate joint effusion and suggest occult fracture when radiographic findings are otherwise subtle.
Wrist fractures predominantly affect the distal radius with additional injuries to the carpal bones. Colles fracture, the classic distal radius fracture in older adults, demonstrates dorsal displacement and angulation with shortening. Smith fracture is the reverse pattern with volar displacement, often resulting from a fall on a flexed wrist. Scaphoid fractures are common in young adults and may be radiographically occult initially, requiring clinical suspicion based on anatomic snuffbox tenderness and follow-up imaging. Triquetral fractures often appear as small dorsal chip fragments visible on the lateral radiograph.
Hand fractures are common injuries with specific patterns that influence treatment and prognosis. Boxer's fracture affects the fifth metacarpal neck, typically from a direct blow, and demonstrates volar angulation of the metacarpal head. Bennett fracture is an intra-articular fracture-dislocation of the thumb carpometacarpal joint requiring surgical fixation. Gamekeeper's or skier's thumb involves injury to the ulnar collateral ligament of the thumb metacarpophalangeal joint, often with an associated avulsion fracture. Mallet finger results from disruption of the extensor tendon at its distal phalanx insertion, either by avulsion or direct laceration.
<image>Panel A: Clavicle fracture at the middle third with typical displacement pattern. Panel B: Posterior fat pad sign on lateral elbow radiograph indicating occult radial head fracture. Panel C: Colles fracture with dorsal angulation and impaction of the distal radius. Panel D: Scaphoid fracture through the waist with subtle lucent line requiring careful evaluation.</image>
IV. Lower Extremity Fractures
Hip fractures represent a major source of morbidity and mortality in elderly patients and require prompt diagnosis and treatment. Femoral neck fractures occur intracapsularly and carry risk of avascular necrosis due to disruption of the blood supply that courses along the femoral neck. The Garden classification grades femoral neck fractures by displacement, with higher grades indicating greater displacement and poorer prognosis. Intertrochanteric fractures occur between the greater and lesser trochanters and are extracapsular with preserved blood supply. Disruption of Shenton line, the smooth arc from the femoral neck to the inferior pubic ramus, indicates hip pathology.
Knee fractures may involve the distal femur, proximal tibia, patella, or fibula, each with specific injury mechanisms. Tibial plateau fractures result from axial loading combined with valgus or varus stress and may demonstrate depression, split, or combined patterns. Lateral tibial plateau fractures are more common due to the typical valgus mechanism of injury. Patellar fractures may be transverse from direct trauma or avulsion from quadriceps contraction, with bipartite patella representing a developmental variant that should not be confused with fracture. The Segond fracture is an avulsion of the lateral tibial plateau indicating anterior cruciate ligament injury, while the lipohemarthrosis sign on lateral radiograph indicates intra-articular fracture.
Ankle fractures are classified by the Weber system based on the level of the fibular fracture relative to the ankle syndesmosis. Weber A fractures occur below the syndesmosis and are typically stable. Weber B fractures occur at the level of the syndesmosis with variable stability depending on associated injuries. Weber C fractures occur above the syndesmosis and indicate disruption of the syndesmotic ligaments with inherent instability. The Maisonneuve fracture combines a high fibular fracture with syndesmotic disruption and medial ankle injury, making full-length tibia-fibula radiographs essential when medial ankle injury is present.
Foot fractures include calcaneal, talar, metatarsal, and phalangeal injuries with specific clinical significance. Calcaneal fractures typically result from axial loading as in a fall from height and are evaluated using Bohler angle, which is decreased when the posterior tuberosity is compressed. Talar fractures carry risk of avascular necrosis similar to femoral neck fractures due to the precarious blood supply. Jones fracture involves the proximal fifth metatarsal diaphysis and has a propensity for nonunion requiring careful distinction from avulsion fractures of the tuberosity. Lisfranc injuries affect the tarsometatarsal joints and may be purely ligamentous or associated with fractures.
<image>Panel A: Femoral neck fracture with disruption of Shenton line indicating displacement. Panel B: Tibial plateau fracture with depression of the lateral plateau and lipohemarthrosis. Panel C: Weber B ankle fracture at the level of the syndesmosis with associated medial clear space widening. Panel D: Calcaneal fracture with decreased Bohler angle indicating loss of tuberosity height.</image>
V. Spine Imaging
Cervical spine evaluation begins with assessment of radiographic alignment using the anterior vertebral line, posterior vertebral line, spinolaminar line, and spinous process tips. All four lines should demonstrate smooth lordotic curves without step-offs or abrupt angulation. Prevertebral soft tissue swelling suggests underlying injury and should measure less than seven millimeters at the C2 level and less than twenty-two millimeters at C6. Each vertebral body is examined for height loss, cortical disruption, and abnormal density. The intervertebral disc spaces should be uniform in height and the facet joints aligned.
Cervical spine fractures follow characteristic patterns based on mechanism of injury. Jefferson fracture is a burst fracture of the C1 ring resulting from axial loading, visualized as lateral displacement of the lateral masses on the open-mouth odontoid view. Hangman's fracture involves bilateral fractures through the C2 pars interarticularis and results from hyperextension. Odontoid fractures are classified by location, with Type II fractures at the base of the dens being most common and most prone to nonunion. Flexion teardrop fractures indicate severe ligamentous injury and potential spinal cord damage, representing unstable injuries.
Thoracolumbar spine fractures are classified by mechanism and pattern to guide treatment decisions. Compression fractures result from flexion and produce anterior wedging of the vertebral body with relative preservation of the posterior elements. Burst fractures result from axial loading and produce retropulsion of bone fragments into the spinal canal with potential cord compression. Chance fractures, or seatbelt injuries, result from flexion-distraction and produce horizontal fractures through the vertebral body, pedicles, and posterior elements. Fracture-dislocation injuries combine multiple mechanisms and represent the most unstable injury pattern.
CT has largely replaced radiography as the primary imaging modality for acute spinal trauma due to superior sensitivity for fracture detection. Multiplanar reconstructions in sagittal and coronal planes complement axial images for complete evaluation. MRI is indicated when neurological deficit is present, when ligamentous injury is suspected, or when cord compression requires evaluation. MRI demonstrates spinal cord signal abnormality, epidural hematoma, disc herniation, and ligamentous disruption that may not be apparent on CT. Imaging findings must be correlated with clinical examination to guide management.
<image>Panel A: Lateral cervical spine radiograph with alignment lines demonstrating normal lordotic curve. Panel B: Jefferson fracture on open-mouth odontoid view with lateral mass displacement. Panel C: Thoracic compression fracture with anterior wedging and preserved posterior wall height. Panel D: MRI of thoracic spine showing cord compression with signal abnormality indicating myelopathy.</image>
VI. Joint Imaging
Arthritis patterns on radiography help distinguish osteoarthritis from inflammatory arthropathies based on characteristic findings. Osteoarthritis demonstrates joint space narrowing that is typically asymmetric within the joint, subchondral sclerosis from increased mechanical stress, osteophyte formation at joint margins, and subchondral cysts. The distribution favors weight-bearing joints and specific locations within joints such as the medial knee compartment and first carpometacarpal joint. The hip demonstrates superior joint space narrowing in osteoarthritis, while the rheumatoid hip shows axial migration.
Rheumatoid arthritis produces a different pattern characterized by periarticular osteopenia, symmetric joint space narrowing, and marginal erosions at the bare areas where bone is not covered by cartilage. The distribution classically affects the hands and feet with involvement of the metacarpophalangeal and proximal interphalangeal joints while sparing the distal interphalangeal joints. Cervical spine involvement includes atlantoaxial subluxation that may threaten the spinal cord. The erosive pattern and symmetric distribution distinguish rheumatoid arthritis from osteoarthritis.
Crystal arthropathies including gout and calcium pyrophosphate deposition disease produce characteristic imaging findings. Gout demonstrates well-defined erosions with overhanging edges, often described as punched-out lesions with sclerotic margins. Soft tissue tophi may calcify and are visible on radiographs. Gout classically affects the first metatarsophalangeal joint but may involve any joint. Calcium pyrophosphate deposition disease produces chondrocalcinite visible as calcification within cartilage, particularly the knee menisci and triangular fibrocartilage of the wrist, along with degenerative changes in unusual locations such as the patellofemoral and radiocarpal joints.
MRI provides superior evaluation of internal joint structures and is the modality of choice for suspected internal derangement. In the shoulder, MRI evaluates rotator cuff tears that may be partial or full thickness, with full-thickness tears demonstrating fluid signal extending through the tendon. Labral tears including SLAP lesions and Bankart lesions associated with instability are well demonstrated. In the knee, meniscal tears appear as linear signal extending to the articular surface, while ligament injuries demonstrate edema and fiber discontinuity. Cartilage defects are directly visualized on MRI, enabling assessment of the articular surfaces.
<image>Panel A: Hand radiograph showing osteoarthritis with Heberden nodes at DIP joints and first CMC involvement. Panel B: Rheumatoid arthritis with symmetric MCP erosions and periarticular osteopenia. Panel C: Gout with punched-out erosions and overhanging edges at the first MTP joint. Panel D: Shoulder MRI demonstrating full-thickness rotator cuff tear with tendon retraction.</image>
VII. Bone Tumors
Imaging features suggesting benign bone lesions include well-defined margins with a narrow zone of transition between normal and abnormal bone. Geographic patterns of bone destruction with smooth, sclerotic borders indicate slow growth allowing the bone to mount a response. The absence of periosteal reaction suggests that the lesion is not irritating the periosteum or is growing slowly enough to allow incorporation of new bone. No soft tissue mass should be present, as cortical containment indicates the lesion respects anatomic boundaries. Stability or slow growth on serial imaging supports a benign diagnosis.
Aggressive imaging features raise concern for malignancy and include permeative or moth-eaten patterns of bone destruction with wide transition zones. Periosteal reaction patterns such as sunburst, with spicules radiating from the cortex, and Codman triangle, representing elevated periosteum at the lesion margin, indicate rapid growth that outpaces the periosteum's ability to form organized new bone. Soft tissue mass extending through cortical destruction indicates lack of containment. Rapid growth on serial imaging and pathologic fracture through the lesion support aggressive behavior.
Common benign bone tumors have characteristic locations and imaging appearances. Enchondromas occur in the small bones of the hands and feet, demonstrating chondroid matrix calcification with rings and arcs pattern. Osteochondromas arise from the metaphysis and demonstrate cortical and medullary continuity with the parent bone. Non-ossifying fibromas appear as eccentric metaphyseal lucent lesions with sclerotic borders in children and adolescents. Simple bone cysts are central metaphyseal lesions that may demonstrate the fallen fragment sign after pathologic fracture.
Primary malignant bone tumors occur in characteristic age groups and locations. Osteosarcoma most commonly affects adolescents and young adults, arising in the metaphysis of long bones with aggressive features and tumor matrix ossification. Ewing sarcoma affects children and young adults, typically arising in the diaphysis with permeative destruction and periosteal reaction producing an onion-skin appearance. Chondrosarcoma occurs in older adults and demonstrates chondroid matrix calcification but with aggressive features distinguishing it from enchondroma. Multiple myeloma produces punched-out lytic lesions without reactive sclerosis in patients over fifty.
<image>Panel A: Enchondroma in the proximal phalanx with chondroid matrix calcification and benign features. Panel B: Osteosarcoma of the distal femur with aggressive periosteal reaction and soft tissue mass. Panel C: Ewing sarcoma of the femoral diaphysis with permeative destruction and lamellated periosteal reaction. Panel D: Multiple myeloma with multiple punched-out lytic lesions throughout the skull.</image>
VIII. Soft Tissue Imaging
Soft tissue calcification patterns provide diagnostic information about the underlying pathology. Dystrophic calcification occurs in damaged tissue with normal calcium metabolism and appears as amorphous calcification in areas of prior trauma, infection, or tumor. Metastatic calcification results from abnormal calcium metabolism, typically hypercalcemia, and deposits in otherwise normal tissues. Tumoral calcinosis produces large periarticular calcified masses, often in patients with renal failure. Vascular calcification outlines vessel walls and may be distinguished from phleboliths, which are calcified venous thrombi appearing as round calcifications with lucent centers.
Soft tissue mass evaluation begins with radiography to assess for calcification, ossification, and bone involvement. Ultrasound effectively distinguishes cystic from solid lesions and can characterize superficial masses. MRI is the modality of choice for complete characterization of soft tissue masses, demonstrating tissue composition, anatomic extent, and relationship to neurovascular structures. CT is used when MRI is contraindicated and provides complementary information about calcification and cortical bone involvement.
Common benign soft tissue lesions have characteristic imaging appearances that may enable specific diagnosis. Lipomas demonstrate homogeneous fat signal on all MRI sequences, matching subcutaneous fat. Ganglia appear as well-defined cystic lesions with thin walls adjacent to joints or tendon sheaths. Hemangiomas demonstrate T2 hyperintensity with serpiginous vessels and may contain phleboliths visible on radiography. Giant cell tumors of tendon sheath appear as solid masses adjacent to tendons with characteristic low signal on all MRI sequences due to hemosiderin content.
Muscle pathology is well evaluated with MRI, demonstrating characteristic signal changes in different conditions. Muscle strains and tears demonstrate edema and hemorrhage with T2 hyperintensity and possible fiber discontinuity. Myositis produces diffuse muscle edema that may be infectious, inflammatory, or related to rhabdomyolysis. Fatty atrophy replaces muscle with fat signal, indicating chronic denervation or disuse. Intramuscular abscess appears as a rim-enhancing fluid collection requiring drainage and appropriate antimicrobial therapy.
<image>Panel A: Dystrophic calcification in the quadriceps following prior muscle injury. Panel B: Lipoma on MRI demonstrating homogeneous fat signal identical to subcutaneous fat. Panel C: Ganglion cyst adjacent to the dorsal wrist with thin wall and homogeneous fluid content. Panel D: Muscle strain with T2 hyperintensity and partial fiber disruption in the hamstring.</image>
IX. Pediatric Musculoskeletal Imaging
Pediatric skeletal imaging requires understanding of normal developmental anatomy and age-specific injury patterns. Growth plates, or physes, represent the weakest point in the pediatric skeleton and are more susceptible to injury than ligaments, which explains why physeal fractures are more common than ligamentous injuries in children. Ossification centers appear at predictable ages and should not be confused with fractures. Secondary ossification centers may appear irregular and should be compared with the contralateral side when concerning. Familiarity with normal pediatric skeletal development prevents misdiagnosis.
The Salter-Harris classification describes physeal fractures based on the relationship of the fracture line to the growth plate. Type I fractures pass directly through the physis without involving the metaphysis or epiphysis and may be radiographically occult. Type II fractures extend through the physis and exit through the metaphysis, producing the Thurston-Holland fragment. Type III fractures extend through the physis and exit through the epiphysis, involving the articular surface. Type IV fractures cross the metaphysis, physis, and epiphysis, disrupting the growth plate. Type V fractures are crush injuries to the physis that may not be visible initially but lead to growth disturbance.
Developmental conditions affecting the pediatric hip require timely imaging diagnosis. Developmental dysplasia of the hip is evaluated with ultrasound in infants before ossification of the femoral head, assessing acetabular coverage and stability. Legg-Calve-Perthes disease produces avascular necrosis of the femoral head, demonstrating fragmentation, sclerosis, and eventual reossification on radiographs. Slipped capital femoral epiphysis affects adolescents, with the femoral epiphysis slipping posteriorly and inferiorly relative to the metaphysis, best seen on frog-leg lateral radiograph. Osgood-Schlatter disease involves traction apophysitis at the tibial tubercle in active adolescents.
Non-accidental trauma produces specific skeletal injury patterns that should raise concern for child abuse. Classic metaphyseal lesions, also termed corner or bucket-handle fractures, are highly specific for abuse and result from shearing forces at the metaphyseal-physeal junction. Posterior rib fractures in infants without history of major trauma are concerning for abuse from squeezing. Multiple fractures at different stages of healing indicate repeated injury. Long bone fractures in non-ambulatory infants require careful explanation, as abuse should be considered when the history does not match the injury.
<image>Panel A: Salter-Harris type II fracture of the distal radius with metaphyseal fragment. Panel B: Developmental dysplasia of the hip on ultrasound showing inadequate acetabular coverage. Panel C: Slipped capital femoral epiphysis on frog-leg lateral showing posterior displacement of the epiphysis. Panel D: Classic metaphyseal lesion at the distal femur concerning for non-accidental trauma.</image>
X. Choosing Musculoskeletal Imaging
Fracture evaluation typically begins with radiography, which remains the first-line modality for suspected skeletal injury. Standard protocols include a minimum of two orthogonal views to avoid missing injuries visible only in one projection. When clinical suspicion remains high despite negative radiographs, CT provides superior fracture detection, particularly for anatomically complex areas such as the wrist, foot, and spine. MRI is indicated for suspected stress fractures that may not be visible on initial radiographs and for evaluating associated soft tissue injuries. Comparison views of the contralateral extremity may be helpful in pediatric patients.
Joint pain evaluation depends on the suspected pathology and the information required for management. Radiography is appropriate for initial evaluation of traumatic injury and provides information about bone alignment, joint space, and degenerative or inflammatory changes. MRI is the modality of choice when internal derangement is suspected, including meniscal tears, ligament injuries, and labral pathology. Ultrasound can evaluate superficial structures including tendons and may be used for dynamic assessment of instability. CT arthrography provides an alternative when MRI is contraindicated.
Soft tissue mass evaluation follows a structured approach beginning with radiography to assess for calcification and bone involvement. MRI is the imaging modality of choice for characterizing soft tissue masses, determining tissue composition, and assessing anatomic extent for surgical planning. Biopsy is typically required for definitive diagnosis unless imaging findings are pathognomonic for a benign lesion such as lipoma. The imaging-guided biopsy approach should be planned in consultation with the treating surgeon to avoid compromising subsequent surgical margins.
Back pain imaging depends on clinical presentation and red flag symptoms. In the absence of red flags, imaging is often not indicated for acute low back pain, which typically improves with conservative management. Urgent MRI is indicated when spinal cord compression, cauda equina syndrome, or epidural abscess is suspected based on neurological deficits or infection risk. CT is preferred for acute trauma to evaluate for fracture. Radiography may be appropriate for initial evaluation of chronic pain or when osteoporotic compression fracture is suspected. The imaging decision balances diagnostic benefit against the costs and potential for incidental findings.
<image>Panel A: Algorithm for imaging selection in suspected fracture based on clinical probability and initial radiograph results. Panel B: MRI indication decision tree for joint pain based on clinical presentation and examination findings. Panel C: Soft tissue mass imaging pathway from radiography through MRI and biopsy. Panel D: Back pain imaging algorithm incorporating red flag symptoms and neurological examination.</image>
Summary
Systematic radiograph interpretation using the ABCS approach evaluates alignment, bones, cartilage spaces, and soft tissues. Fracture description includes location, type, displacement, and angulation using standardized terminology. Special fracture types such as pathologic, stress, and avulsion fractures have specific clinical implications. Fracture healing proceeds through inflammatory, soft callus, hard callus, and remodeling phases.
Upper extremity fractures include clavicle, proximal humerus, elbow, wrist, and hand injuries with characteristic patterns. Colles fracture demonstrates dorsal angulation while scaphoid fractures may be radiographically occult. Lower extremity fractures include hip, knee, ankle, and foot injuries with classification systems guiding treatment. Femoral neck fractures carry avascular necrosis risk while Weber classification describes ankle fracture stability.
Spine imaging evaluates alignment, vertebral body integrity, and soft tissues. Cervical fractures include Jefferson, hangman's, and odontoid fractures with specific mechanisms. Thoracolumbar fractures include compression, burst, and Chance patterns. MRI is indicated for neurological deficit or suspected cord compression.
Arthritis patterns distinguish osteoarthritis from inflammatory and crystal arthropathies. MRI evaluates internal joint derangement including meniscal and ligamentous injuries. Bone tumor imaging distinguishes benign from aggressive features. Pediatric imaging requires knowledge of normal development and Salter-Harris classification for physeal injuries.
Key Terms
Comminuted: Fracture pattern with multiple fragments, indicating higher-energy injury mechanism and potentially more complex treatment requirements.
Avulsion: Fracture type where a tendon or ligament attachment pulls a bone fragment from its origin, indicating the force was transmitted through the soft tissue.
Salter-Harris: Classification system for pediatric physeal fractures based on the relationship of the fracture line to the growth plate, with higher types indicating greater potential for growth disturbance.
Osteophyte: Bone spur forming at joint margins in osteoarthritis, representing an attempt at joint stabilization in response to cartilage loss and mechanical stress.
Erosion: Bone loss at joint margins characteristic of inflammatory arthritis, occurring at bare areas where bone is not protected by articular cartilage.
Periosteal Reaction: New bone formation along the outer cortical surface indicating underlying pathology, with pattern ranging from benign solid reaction to aggressive sunburst.
Lipohemarthrosis: Fat-blood level visible on horizontal beam radiograph indicating intra-articular fracture, as bone marrow fat has escaped into the joint.
Codman Triangle: Triangular area of elevated periosteum at the margin of an aggressive bone lesion, indicating rapid growth that has outpaced organized periosteal new bone formation.
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