Skeletal System

Application of Radiological Pathology in Identifying Abnormalities of the Axial and Appendicular Skeleton

Introduction

The skeletal system is composed of 206 separate bones and is responsible for body support, protection, movement, and blood cell production.

It contains more than 98% of the body’s total calcium and up to 75% of its total phosphorus.

Skeletal System

The system is commonly divided into the axial skeleton, which contains 80 bones, and the appendicular skeleton, which contains 126 bones.

Bone is a specialized connective tissue made primarily of collagen and calcium phosphate, which provides strength and flexibility.

The construction of bone classifies tissue as either compact or spongy.

The outer portion of bone is composed of compact bone, and the inner portion, termed the medullary canal, is made up of cancellous bone.

Osteoblasts are specialized bone-forming cells that play a crucial role in the formation of new bone tissue.

They are responsible for bone growth , repair, and remodelling throughout a person's life.

Osteoclasts a bone cell that breaks down bone tissue to help with bone repair and mineral balance.

They break down bone tissue, releasing minerals such as calcium and phosphate into the bloodstream. Osteoclasts work in balance with osteoblasts (bone-forming cells) to maintain bone health and homeostasis.

Axial and Appendicular skeleton radiographic landmarks

The axial skeleton consists of 80 bones that form the central axis of the body, including the skull, vertebral column, and thoracic cage. Key radiographic landmarks include

SKULL

Cranial Bones: Frontal, parietal, occipital, temporal, sphenoid, and ethmoid bones.

Facial Bones:

• Radiographic landmarks
• Maxillae.
• zygomas.

nasal bones, lacrimal bones and palatine bones.

Sutures:

• Radiographic landmarks
• Coronal suture.
• Sagittal suture.
• Lambdoid suture.

squamosal suture.

VERTEBRAL COLUMN

Cervical Vertebrae (C1-C7):

Radiographic Landmarks

Atlas (C1).

• axis (C2).

typical cervical vertebrae (C3-C7).

Thoracic Vertebrae(T1-T12)

• Radiographic landmarks

Vertebral Bodies.

Costovertebral Joints.

Spinous Processes.

• Pedicles.

Intervertebral Foramina.

Lumber vertebrae

• Radiographic landmarks

Vertebral Bodies.

Spinous Processes.

• Pedicles.

Intervertebral Foramina.

Sacrum

• Radiographic landmarks

Sacral Promontory.

Sacral Foramina.

• Sacroiliac Joints (SI Joints).

Sacral Curvature.

Thoracic Cage:

• Sternum
• Radiographic landmarks
• Manubrium.
• Body.

xiphoid process.

Ribs

• Radiographic landmarks
• True ribs (1-7).
• false ribs (8-10).

floating ribs (11-12).

Appendicular Skeleton Radiographic Landmarks

The appendicular skeleton includes 126 bones that form the limbs and their girdles. Key radiographic landmarks include:

Upper Limb:

Pectoral Girdle

• Radiographic landmarks
• Clavicle.

scapula.

Clavicle

• Radiographic landmarks
• Sternal end.

acromial end.

Scapula

• Radiographic landmarks
• Acromion.
• coracoid process.

glenoid cavity.

Arm

• Radiographic landmarks
• Head of humerus.
• greater and lesser tubercles.

olecranon fossa.

Forearm

• Radiographic landmarks
• Radius and ulna.
• olecranon process.

radial head.

Hand

• Radiographic landmarks
• Carpals.
• Metacarpals.

phalanges.

Lower Limb:

Pelvic Girdle

• Radiographic landmarks
• Ilium.
• Ischium.
• Symphysis pubis.

acetabulum.

Thigh

• Radiographic landmarks
• Femur with head.
• Greater and lesser trochanters.

Condyles.

Leg

• Radiographic landmark
• Tibia.
• Fibula.
• Tibial tuberosity.

Fibular head.

Foot

• Radiographic landmark
• Tarsals.
• Metatarsals.

Phalanges.

NORMAL RADIOGRAPHIC PATTERNS OF THE AXIAL AND APPENDICULAR SYSTEM

A normal radiographic pattern refers to the standard appearance of bones and joints in a healthy individual.

Below is an overview of the axial and appendicular skeleton normal radiographic pattern.

Skull

• Radiographic pattern
• 1.Smooth, well-defined outer and inner cortices.
• The bone structure should be without fractures, tumors, or other pathological changes.
• 2.Normal suture lines (e.g., coronal, sagittal, lambdoid).
• Radiolucent lines, symmetric and serrated in young adults
• Sutures should not be mistaken for fractures.
• 3.Clear, aerated paranasal sinuses (frontal, ethmoid, sphenoid, maxillary).

Sinuses are normally: Air-filled and radiolucent areas.

There should no visible fluid or opacities (no signs of infection, inflammation, or obstruction).

4.Sella turcica is intact with normal size.

No fractures, erosions and not enlarged (which could suggest a pituitary tumor) or abnormally small.

Cervical Spine (C1–C7)

• Radiographic pattern

1.Lordotic curvature (concave posteriorly) is maintained.

The spine should retain its natural alignment without excessive flattening, Loss of curvature may indicate muscle spasm 2.Vertebral bodies are well-aligned and rectangular in shape.

The bones of the spine (vertebrae) are properly stacked without abnormal shifts evenly spaced, normal vertebral anatomy (no compression fractures, degenerative changes).

3.Intervertebral disc spaces are equal and maintained.

• The spaces are uniform in height with no significant narrowing or widening.
• No prevertebral soft tissue swelling.

The space between the front of the spine (vertebral bodies) and the airway/pharynx in the neck (cervical region).

Thoracic Spine (T1–T12)

• Radiographic pattern
• 1.Kyphotic curvature
• A normal kyphotic curve prevents excessive spinal stress.
• 2.Intervertebral disc spaces maintained.

The spaces are uniform in height with no significant narrowing or widening.

3.Spinous processes well-aligned.

They form a straight line when viewed from the front (AP view) or side (lateral view), indicating no rotational deformities or misalignments, no signs of vertebral compression or scoliosis.

• 4.Rib articulations are intact.

No fractures, dislocations, or degenerative changes at these junctions.

Lumbar Spine (L1–L5) & Lumbosacral Junction (L5-S1)

• Radiographic pattern
• 1.Lordotic curvature is maintained.
• Loss of lordosis may indicate muscle strain or disc disease.

2.Vertebral bodies are rectangular and aligned.

The bones of the spine (vertebrae) are properly stacked without abnormal shifts, normal vertebral anatomy (no compression fractures, degenerative changes).

3.Intervertebral disc spaces are well-preserved.

• The spaces are uniform in height with no significant narrowing or widening.
• 4.No spondylolisthesis or fractures.
• Spondylolisthesis is suggested if vertebrae are misaligned.

spondylolisthesis

Sacrum & Coccyx

• Radiographic pattern

1.Sacral promontory and foramina are clearly visible.

These structures are well-defined without obscuration by overlying structures or pathology.

• 2.Coccyx is curved anteriorly with no fractures.

Normal the coccyx naturally curves forward, no breaks or dislocations should be seen.

3.Sacroiliac (SI) joints are symmetrical

Both joints appear similar in width, alignment, and bone density, with no unilateral narrowing/widening or erosions.

Shoulder Joint

• Radiographic pattern

1.Normal Glenohumeral Alignment

The humeral head is centered within the glenoid cavity without subluxation (partial dislocation) or widening of the joint space.

2.Well-defined Acromioclavicular (AC) Joint The joint margins are clear and smooth, with normal joint space width (1–3 mm) and no bony irregularities.

3. Smooth Humeral Head and Glenoid Cavity

Both surfaces have well-defined, even contours without irregularities, erosions, or deformities.

Elbow Joint

• Radiographic pattern
• 1.Aligned Humeroradial and Humeroulnar Joints
• Normal anatomical relationship and preserved joint spaces.

2.Normal Olecranon Process and Fossa The olecranon is intact, well-contoured, and articulates smoothly with the fossa without erosions, fractures, or malalignment.

3. Clear Anterior and Posterior Fat Pads

The anterior fat pad appears as a thin, linear shadow (not bulging), and the posterior fat pad is not visible—indicating no significant joint effusion

Wrist Joint

• Radiographic pattern

1.Aligned Carpal Bones

The bones maintain normal anatomical relationships with smooth, parallel joint spaces and no overlapping or step-offs.

2.Symmetric Joint Spaces

Spaces are uniform in width across a joint (radiocarpal wrist joints), with no focal narrowing or widening.

Hip Joint

• Radiographic pattern
• 1.Normal Femoral Head Position
• It should be centered within the acetabulum with no dislocation.

2.Smooth Acetabulum – No bony irregularities The bony margins are well-defined and regular, with no erosions, fractures, or structural abnormalities.

3.Equal Joint Spaces

The spaces are uniform in width across the joint with no focal narrowing or widening.

Knee Joint

• Radiographic pattern

1.Proper Patellar Position

The patella is centered within the trochlear groove without Lateral/medial displacement (subluxation).

2.Symmetric Medial & Lateral Joint Spaces The spaces are equal in width when comparing the medial and lateral compartments indicating joint alignment.

3.No Tibial Plateau Fractures

The bone cortex is smooth and continuous, with no fracture lines and depressions in the medial or lateral plateau.

Ankle Joint

• Radiographic pattern
• 1.Aligned Tibia, Fibula and Talus
• The bones maintain normal anatomical relationships
• 2.Even Joint Space

No narrowing or widening of the joint.

3.No Soft Tissue Swelling

Soft tissues appear normal in thickness and density,

Importance of Normal Radiographic Appearance

• Differentiating Normal Variants from Pathology (e.g., bipartite patella vs. fracture).

Identifying Trauma-Related Changes (e.g., dislocations, fractures).

Detecting Early Degenerative or Infectious Processes (e.g., osteoarthritis, osteomyelitis).

ABNORMAL RADIOGRAPHIC FINDINGS IN THE AXIAL AND APPENDICULAR SYSTEM

Radiographic imaging plays a crucial role in diagnosing abnormalities of the skeletal system.

Abnormal radiographic findings can manifest as structural deformities, fractures, joint misalignments, abnormal bone density, or pathological changes due to infection, tumors, or degenerative conditions.

This discussion will outline the key abnormal radiographic findings, categorized based on congenital, acquired, traumatic, and degenerative disorders.

CONGENITAL DISORDERS

Are abnormalities present at birth, resulting from genetic mutations, developmental defects, or environmental factors affecting fetal bone formation.

These disorders may lead to skeletal deformities, joint misalignment, or abnormal bone growth.

1. Osteogenesis imperfecta (OI)

Also called brittle bone disease

Is a congenital genetic disorder characterized by brittle/fragile bones that fracture easily due to defective collagen production, primarily caused by mutations in the Collagen Type I Alpha 1 Chain genes.

Are genetic disorders of collagen type I Production involving connective tissues and bones.

Skeletal System

NOTE: The hallmark feature of OI is osteoporosis and fragile bones that fracture easily as well as blue sclera, dental fragility and hearing loss.

OI affect both quality and quantity(i.e bone mass)

Clinical presentation

• Major clinical features characterize of OI
• Osteoporosis with abnormal bone fragility
• Blue sclera
• Dentinogenesis imperfecta

Hearing impairment

Other features include ligamentous laxity and hypermobility of joint, short stature and easy bruising

Radiological Features of OI

Osteopenia

Bones appear less dense and more radiolucent due to reduced bone mass(loss of bone density).

Multiple Fractures

Fractures at various stages of healing are common, often with deformities or angulation.

Bone Deformities

• Long bones, such as the femur or tibia, may show bowing or curvature.

Wormian Bones

• Small, irregular bones within the cranial sutures.

Thin Cortices

• The outer layer of bones appears thinner than normal.
• Zebra stripe sign

occurs in long bones due to treatment with cyclic bisphosphonate therapy.

Wormian bones

2. Osteopetrosis

It is caused by genetic mutations that affect the function of osteoclasts, the cells responsible for breaking down bone tissue.

Radiological Findings of osteopetrosis

• Increased bone density(generalized osteosclerosis)
• Bones appear abnormally white (sclerotic)or appearing denser than normal on x-ray.
• Loss of medullary cavity
• No visible marrow space due to bone overgrowth.

Sandwich Vertebrae Sign

Alternating dense and less dense bands in vertebral bodies creating a "sandwich-like" appearance.

Bone-within-bone

• Bones may show alternating dense and radiolucent bands, resembling a bone within a bone.

Thickened Cortices

• The outer layer of bones is excessively thickened, encroaching on the medullary cavity.

Metaphyseal Flaring

Widened metaphyses of long bones

3. Diaphyseal Aclasis (Hereditary Multiple Exostoses/Osteochondromatosis)

Is an inherited skeletal disorder characterized by the development of multiple osteochondromas (benign cartilage-capped bony outgrowths) near the growth plates of long bones, particularly in the metaphyses and diaphyses.

An exostosis is a general term for any benign bone growth that extends outwards from the surface of a bone.

An osteochondroma, on the other hand, is a specific type of exostosis characterized by being capped with cartilage "aclasis" refers to the continuity of structure between normal and pathological tissue.

It essentially describes a situation where there's a lack of a clear separation or "breaking" between normal and abnormal tissue.

Radiological findings

Multiple Osteochondromas

• Bony growths near the metaphysis of long bones, often bilateral and symmetrical.

Reduced Joint Space

• Osteochondromas near joints can lead to narrowing of the joint space.
• Bone deformity or bowing

Especially in long bones due to pressure from exostoses

4. Scoliosis

Is the Lateral bending or curvature of the spine, visible as "C" or "S" shapes.

Radiological findings

Lateral Spinal Curvature

• A visible abnormal curve of the spine.
• Wedge-shaped Vertebrae
• Vertebrae may appear compressed or deformed on one side, contributing to the curvature.

Vertebral Rotation

The vertebrae may appear rotated, often assessed by the position of the pedicles on the X-ray.

Wedge-shaped Vertebrae

ACQUIRED DISORDERS

Refer to medical conditions that develop after birth, often due to environmental factors, lifestyle, infections, injuries, or age.

1.Osteoporosis

It is a condition characterized by the weakening of bones, making them fragile and more likely to fracture.

NOTE: Metabolic bone disease characterized by decreased bone mass and skeletal fragility.

Radiological features

Generalized Osteopenia

• Bones appear less dense and more radiolucent due to reduced bone mass.

Vertebral Compression Fractures

• Flattening or collapse of vertebral bodies, often seen in the spine.
• pencilling of vertebrae
• Thinning of Cortical Bone

The outer layer of bones becomes thinner, contributing to fragility.

2. Osteomyelitis

Is an infection of the bone, typically caused by bacteria (like Staphylococcus aureus) or fungi involving the medullary cavity.

It can result from bloodstream infections, nearby tissue infections, or direct exposure due to injury or surgery. The condition leads to inflammation, bone destruction, and sometimes necrosis.

Radiological features

• Regional osteopenia-Bone destruction
• Areas of radiolucency (dark spots) indicating bone loss.
• Periosteal Reaction/thickening

New bone formation along the periosteum, often seen as layers or spiculated patterns.

Periosteum is a fibrous sheath that covers bones(a dense layer of vascular connective tissue enveloping the bones except at the surface of the joints.

Sequestrum

• Dead, necrotic bone fragments visible as dense areas within the affected bone.
• Involucrum
• A shell of new bone formed around the sequestrum, indicating chronic infection.

Note: An effusion may be seen in an adjacent joint.

4. Tuberculosis of the Spine/ spondylitis (Pott's Disease)

Is a form of tuberculosis that affects the spine, caused by the bacterium Mycobacterium tuberculosis.

Radiological features

Vertebral Body Destruction

• Visible bone loss or collapse of the affected vertebrae.

Intervertebral Disc Space Narrowing

• The disc space between infected vertebrae appears reduced due to disc destruction.
• Paraspinal Abscess or Gibbus Deformity

Evidence of soft tissue swelling or a sharp angular deformity of the spine.

5. Paget’s disease

It is a chronic disorder that disrupts the normal bone remodeling process.

It causes bones to grow larger, weaker and misshapen due to excessive breakdown and abnormal regrowth of bone tissue.

Paget disease of the bone is a common, chronic metabolic bone disorder characterized by excessive abnormal bone remodeling.

The classically described radiological appearances are expanded bone with a coarsened trabecular pattern.

Bone remodeling is a continuous process where old or damaged bone tissue is replaced with new bone tissue.

Clinical presentation

The majority (approximately three-quarters) of patients are asymptomatic at the time of diagnosis, the diagnosis being an incidental finding on imaging. Presenting symptoms include:

• Localized pain and tenderness (most common symptom)
• Increased focal temperature due to bony hypervascularity (not fever)
• Increased bone size: historically, changing hat size was a giveaway
• Bowing deformities
• Kyphosis
• Decreased range of motion

Signs and symptoms relating to complications (see below)

The most frequent sites of involvement are:

• spine
• pelvis (often asymmetric)
• skull

proximal long bone

Radiological features

Coarsened Trabecular Pattern

The affected bones show thickened and irregular trabeculae, giving them a "woven" appearance.

Bone Expansion

• Enlarged bones with cortical thickening, often seen in the pelvis, skull, or long bones.

Mixed Lytic and Sclerotic Lesions

Areas of bone destruction (lysis) alongside regions of increased density (sclerosis), creating a patchy appearance.

Coarsened trabecular trabeculae pattern :- a non uniform or abnormal arrangement of

Plain radiographic features

Plain radiographic features will depend upon the phase of the disease.

The early phase features osteolytic (lucent) regions which are later followed by coarsened trabeculae and bony enlargement. Sclerotic changes occur much later in the disease process.

Additional destructive features may become apparent if malignant transformation occurs

Skull

osteoporosis circumscripta: large, well-defined lytic lesions involving the inner aspect of the outer table of the skull (stage one) with a preserved inner table.

cotton wool appearance: mixed lytic and sclerotic lesions of the skull.

diploic widening: both inner and outer calvarial tables are involved, with the former usually more extensively affected Tam o' Shanter sign: platybasia and basilar invagination with the appearance of the skull falling over the facial bones, like a Tam o' Shanter hat; this is said to be a pathognomonic appearance

Spine

picture frame sign: Paget disease of the spine frequently manifests with cortical thickening and sclerosis encasing the vertebral margins, which gives rise to this appearance on radiographs in mixed-phase disease this is said to be a pathognomonic appearance 25 squaring of vertebrae: on lateral radiographs, flattening of the normal concavity of the anterior margin of the vertebral body also adds to the rectangular appearance vertical trabecular thickening: coarser than the more delicate pattern seen in intraosseous hemangiomas with which it may be confused

Pelvis

cortical thickening and sclerosis of the iliopectineal and ischiopubic lines results in the pelvic brim sign and leads to obliteration of Köhler's​ teardrop acetabular protrusion

enlargement of the pubic rami and ischium These findings are often asymmetric, and for some reason, are more commonly seen on the right side.

Long bones

blade of grass or candle flame sign: begins as a subchondral area of lucency with advancing tip of V-shaped osteolysis, extending towards the diaphysis in rare cases, the disease is isolated to the diaphysis, most commonly in the tibia, rather than subchondral bone, which can cause diagnostic confusion.

• shepherd crook deformity
• lateral curvature (bowing) of the femur

anterior curvature of the tibi

6. Spondylolisthesis

Is a condition where one vertebra slips forward or backward over the vertebra below it, disrupting the alignment of the spine. This slippage can cause back pain, nerve compression, or other symptoms, depending on its severity.

Clinical presentation

• When symptomatic, patients present with
• Low back pain
• Radiculopathy and/or

Neurogenic claudication

Pathology

Spondylolisthesis can occur anywhere in the vertebral column but is most frequent in the lumbar spine, particularly when due to spondylolysis at L5/S1 , and when due to degeneration at L4/5 .

• Classification
• Wiltse classification: divides into types by aetiology
• Meyerding classification: grades by severity of the slip

NOTE: In Radiology report

To adequately describe a spondylolisthesis, the type and grade must be stated and the presence or absence of instability

Radiographic Findings

Vertebral Misalignment

Visible forward or backwards displacement of one vertebra relative to the adjacent vertebra.

Step-off Sign

A noticeable "step" in the alignment of the posterior vertebral cortices on lateral X-rays.

• Narrowing of Disc Space

Reduced height of the intervertebral disc at the level of the slippage.

Consider the following on Plain Radiographic features

On lateral lumbar spine x-rays, a "step" in the alignment of the posterior cortices can be visible and then graded by the Meyerding classification.

7. Rickets

Is a condition that affects children, causing their bones to become soft and weak due to a deficiency in vitamin D, calcium, or phosphate.

Radiological features

Widened Growth Plates

• The growth plates appear abnormally wide due to defective mineralization.

Bowing of Long Bones

Visible curvature of the long bones, particularly in the legs, due to weakened bone structure.

8. Ankylosing Spondylitis

Is a chronic inflammatory disease that primarily affects the spine and sacroiliac joints Ankylosing spondylitis (less commonly known as Bechterew disease or Marie-Strümpell disease) is a seronegative spondyloarthropathy, which results in fusion (ankylosis) of the spine and sacroiliac (SI) joints, although involvement is also seen in large and small joints Ankylosing – stiffening / immobility joint

Radiographic features

Sacroiliitis

Inflammation of the sacroiliac joints, visible as joint space widening, sclerosis, or fusion in advanced stage.

Bamboo Spine

Ossification of ligaments and intervertebral discs, creating a rigid, "bamboo-like" appearance of the spine.

On the Spine

early spondylitis is characterized by small erosions at the corners of vertebral bodies with reactive sclerosis (Romanus lesions, which give the shiny corner sign) vertebral body squaring

• noninfectious spondylodiscitis (Andersson lesion)

diffuse syndesmophytic ankylosis can give a "bamboo spine" appearance Syndesmophytes are classically described as paravertebral ossification running parallel to the spine ossification of the supraspinous and interspinous ligaments can give a "dagger spine" appearance on frontal radiographs

9. Rheumatoid Arthritis (RA)

Is a chronic autoimmune disease where the immune system mistakenly attacks the lining of the joints (synovium).

This leads to inflammation, pain, swelling, and eventually joint damage.

Radiological features

Joint Space Narrowing

• Symmetrical narrowing of the joint space due to cartilage destruction.

Marginal Erosions

Bone erosions at the edges of the joint, particularly in the "bare areas" not covered by cartilage.

Soft Tissue Swelling

Fusiform or periarticular swelling due to joint effusion and inflammation.

The radiographic hallmarks of rheumatoid arthritis are:

Marginal erosions; important early finding, in the “bare areas”, frequently in the radial side of the metacarpophalangeal (MCP) joints 7 Soft tissue swelling

Fusiform and periarticular; it represents a combination of joint effusion, edema and tenosynovitis This can be an early/only radiographic finding Osteoporosis: initially juxta-articular, and later generalized; compounded by corticosteroid therapy and disuse Joint space narrowing: symmetrical or concentric, uniform

10.Gout

Is a type of inflammatory arthritis caused by the deposition of monosodium urate crystals in and around the joints. It typically results from elevated levels of uric acid in the blood (hyperuricemia).

Radiological features

Punched-Out Erosions

Well-defined bone erosions with overhanging edges, often described as "mouse-bitten" appearance.

Tophi Formation

Soft tissue masses created by urate crystal deposits, sometimes visible as calcified areas.

Preserved Joint Space

Unlike other types of arthritis, the joint space is often maintained until late stages.

In plain radiograph

Characteristic radiologic changes occur in the chronic stage, though not all patients progress to this. There is a predilection for the small joints of the hands and feet.

• Joints
• Joint effusion (earliest sign)
• Preservation of joint space until late stages of the disease
• An absence of periarticular osteopenia

Eccentric erosions

The typical appearance is the presence of well-defined “punched-out” erosions with sclerotic margins in a marginal and juxta-articular distribution, with overhanging edges, also known as rat bite erosions

Bone

• Punched-out lytic bone lesions
• Overhanging sclerotic margins
• Osteonecrosis

Mineralization is normal

Surrounding soft tissues

• Tophi: pathognomonic

Olecranon and prepatellar bursitis

Periarticular soft tissue swelling due to crystal deposition in tophi around the joints is common The soft tissue swelling may be hyperdense due to the crystals, and the tophi can calcify (uncommon in the absence of renal disease)

DEGENERATIVE DISORDERS

Is the progressive breakdown of joints, bones, and connective tissues, primarily due to aging, mechanical stress, or prior injury.

1. Osteoarthritis(OA)

It is a degenerative joint disease where the protective cartilage cushioning the ends of bones wears down over time.

This leads to pain, stiffness, and reduced mobility, commonly affecting joints like the knees, hips, spine, and hands.

• Scoring systems used to assess the severity of osteoarthritis on radiographs include:
• Kellgren and Lawrence classification

Osteoarthritis Research Society International (OARSI) atlas

The Kellgren and Lawrence system is a common method of classifying the severity of osteoarthritis (OA) using five grades

Classification

Numerous variations of the Kellgren and Lawrence classification system have been used in research. Below is the original description:

• grade 0 (none): definite absence of x-ray changes of osteoarthritis
• grade 1 (doubtful): doubtful joint space narrowing and possible osteophytic lipping

grade 2 (minimal): definite osteophytes and possible joint space narrowing grade 3 (moderate): moderate multiple osteophytes, definite narrowing of joint space, some sclerosis and possible deformity of bone ends grade 4 (severe): large osteophytes, marked narrowing of joint space, severe sclerosis and definite deformity of bone ends

Risk factors

• Strong risk factors for developing osteoarthritis include:
• Obesity
• Increasing age
• Female sex (particularly between the ages of 50 and 80)

Family history

Radiological findings

Joint Space Narrowing

• Reduced space between bones due to cartilage loss.
• characteristically asymmetric
• least specific: present in many other pathological processes
• Osteophyte Formation(osteophytosis)
• Bony outgrowths (bone spurs) along joint margins.
• Subchondral Sclerosis (Sclerotic changes occur at joint margins)
• Increased bone density beneath the cartilage

Frequently seen unless severe osteoporosis is present

Subchondral Cysts

• Also known as geodes

Fluid-filled cavities within the bone near the joint.

Radiographic appearance: Usually seen in the setting of degenerative joint disease, geodes are periarticular lesions that are round-to-oval with a thin sclerotic margin.

2. Degenerative Disc Disease(DDD)

Refers to the gradual wear and tear of intervertebral discs in the spine, often associated with aging or repetitive stress.

Radiological Findings

Disc Space Narrowing

• Reduced height of the intervertebral discs, indicating degeneration.

Osteophyte Formation

• Bony outgrowths (bone spurs) along the edges of vertebral bodies.

Endplate Sclerosis

Increased density and thickening of the vertebral endplates.

Irregular Vertebral Alignment:

Misalignment or changes in the curvature of the spine due to disc degeneration.

Traumatic disorders

Refer to conditions or injuries caused by a sudden physical impact, force, or psychological stress.

Classification of fractures and dislocations A fracture is either a complete break in the continuity of a bone or an incomplete break or crack.

• Fractures are subdivided according to their cause:
• Acute traumatic fractures
• Stress fractures

Pathological fractures

ACUTE TRAUMATIC FRACTURE: Is a broken bone caused by a sudden , forced injury , such as a fall or accident STRESS FRACTURE: Is a small crack in a bone caused by repetitive stress or overuse, rather than a single traumatic injury

Acute traumatic fractures are classified as:

• Complete — discontinuity between two or more bone fragments
• Incomplete — portion of cortex remains intact
• Displaced — space between margins of fracture causing deformity
• Undisplaced — bone fragments closely apposed with minimal deformity

Closed/simple — no communication between fracture and skin surface Open/compound — wound extends from skin surface to fracture is also liable to be contaminated and has a high risk of infection.

Descriptive terms used to indicate the shape or pattern of an acute fracture in the adult are:

• Transverse fractures
• Oblique fractures
• Spiral fractures
• Comminuted fractures (2 or more fragments)
• Compression/crush fractures
• Depressed (in skull)

Dislocations

A joint is dislocated (luxated) when its articular surfaces are wholly displaced one from the other, so that apposition between them is lost.

Subluxation exists when the articular surfaces are partly displaced but retain some contact with each other.

Dislocation may occur in isolation or with a fracture (so-called fracture-dislocation).

Is it dislocation or subluxation?

Fractures in children

• The pattern of bony injuries in the child are somewhat different to the adult as the skeleton is more elastic and less brittle.
• Fractures in children are classified as:
• Complete
• Greenstick fracture
• Torus (buckle) fracture
• Pipe fracture
• Bowing injury
• Infant’s (toddler’s) fracture
• Epiphyseal/metaphyseal fractures

Avulsion injuries

Buckling / bending : One side of the bone bulges out or bends.

Skeletal System

A greenstick fracture is an incomplete fracture. The cortex is broken on one side and buckled on the other with a bending deformity concave to the buckled side.

A buckle(torus) fracture is a buckling of the cortex produced by compression (impaction) forces. Typically seen in the metaphysis of long bones particularly the radius and ulna.

A pipe fracture is a combination of an incomplete transverse fracture of one cortex and a torus fracture of the opposite side.

A bowing injury results in the bending of a long bone usually without a fracture, but with an associated fracture of an adjacent bone. Typically affects the radius, ulna and fibula.

What type of bone fractures are these?

Radiographic diagnosis of fractures

A fracture is identified by the loss of continuity of the cortex and a dark line traversing the adjacent bone. The fracture line appears dark because the soft tissue (usually haematoma) between the bone ends is of less density than the bone itself.

A fracture may appear as a dense/sclerotic line if the fracture ends are overlapping. At this site there is therefore twice as much bone attenuating the X-ray beam.

The classic example is the depressed skull fracture but it can also be seen with overlapping long bone fractures

Skeletal System

It is important to obtain two views at right angles for all suspected fractures and dislocations. On occasion a fracture or dislocation may only be visible on one projection.

Two views are also essential to adequately see the degree of deformity at the fracture site.

it is important that the radiographs always show the joint above and below any suspected long bone fracture, unless it is clinically obvious that the injury is only in the most distal part of the limb. But even then, the nearest joint must always be included on the film.

1. Vertebral Fractures

Refer to breaks or collapses in the bones of the spine (vertebrae)

Findings

Loss of Vertebral Height

Compression fractures often show reduced height in the anterior, middle, or posterior dimensions of the vertebral body.

Fracture Lines

• Visible radiolucent lines indicating breaks in the vertebral body or pedicles.
• Displacement or Misalignment

Vertebrae may appear shifted or misaligned, especially in fracture-dislocations.

Bone Fragmentation

Burst fractures may show multiple bone fragments, sometimes displaced into the spinal canal.

2. Pelvic Fractures

Are breaks in one or more bones of the pelvis, often caused by high-energy trauma (e.g., car accidents) or low-energy injuries in individuals with weakened bones (e.g., osteoporosis).

These fractures can range from stable (minor) to unstable (severe) and may involve the pelvic ring, acetabulum, or sacrum.

Findings

Disruption of Pelvic Ring

Fractures often involve breaks in the pelvic ring, which may appear as discontinuities in the bony structure.

Fracture Lines

• Visible radiolucent lines indicating breaks in the pubic rami, acetabulum, or sacrum.

Pelvic Misalignment

Displacement or misalignment of pelvic bones, often seen in high-energy trauma.

3.Clavicle Fracture

Refers to a break in the collarbone, a long, slender bone connecting the shoulder blade to the sternum.

Findings

Fracture Line

• A visible break or crack in the clavicle, often seen in the middle third of the bone.

Bone Displacement

Misalignment of the fractured bone fragments, which may appear overlapping or separated.

3. Colles' Fracture

It is a common type of wrist fracture involving the distal radius.

It typically occurs due to a fall on an outstretched hand, causing the broken fragment of the radius to tilt upward (dorsal angulation).

This injury is often associated with osteoporosis and is more frequent in older adults.

Findings

Dorsal Angulation

• The distal fragment of the radius is displaced and angled upward.
• Impaction

Compression of the distal radius, leading to shortening of the bone.

Fractures of the forearm

Proximal radio-ulnar fracture-dislocation (Monteggia fracture).

Fracture of the proximal or mid-third ulna, associated with a dislocation of the radial head.

The dislocation of the radial head results in disruption of the radio-capitellar line.

radio-capitellar line: Is a radiographic line used to assess alignment of the elbow joint, parcticulary in children

Normal radiocapitellar line

Distal radio-ulnar fracture-dislocation (Galeazzi fracture)

Fracture of the distal third of the radius associated with dorsal dislocation of the distal radio-ulnar joint.

Frequently a distal radio-ulnar joint dislocation can be identified on the lateral projection only.

4. Femoral Neck Fracture

Refers to a break in the femoral neck, the region just below the femoral head (the ball of the hip joint).

It is a common injury, especially in older adults with osteoporosis, and can result from falls or high-energy trauma.

This type of fracture is classified as intracapsular, meaning it occurs within the joint capsule, and it carries a risk of complications like avascular necrosis due to disrupted blood supply.

Findings

Disruption of Shenton's Line

A smooth, curved line formed by the inferior border of the femoral neck and the superior border of the pubic ramus is interrupted in cases of femoral neck fractures.

• Loss of Cortical Continuity
• A visible break or discontinuity in the cortex of the femoral neck.
• Angulation or Displacement

The femoral head may appear misaligned or displaced relative to the femoral shaft.

Shenton's Line:also known as the Shenton arc, is a radiographic line used to assess hip joint health, particularly to detect hip dislocations or fractures

Shentons line

5. Tibial Plateau Fracture

Is a break in the upper part of the tibia that involves the knee joint.

Tibial Plateau : the flat, superior surface of the tibia, the shin bone, where it articulates with the femur (thigh bone) to form the knee joint The tibial plateau consists of two main parts: the medial tibial condyle and the lateral tibial condyle.

Skeletal System

The Schatzker classification is commonly used to categorize tibial plateau fractures based on the fracture pattern and severity. It divides these fractures into six types.

Type I

• Lateral tibial plateau fracture without depression.

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Type II

• Lateral tibial plateau fracture with depression.

Type III

Pure depression fracture of the lateral tibial plateau (subtypes IIIa: lateral depression, IIIb: central depression).

• Type IV

Medial tibial plateau fracture, often associated with higher energy trauma.

Type V

• Bicondylar tibial plateau fracture involving both medial and lateral condyles.
• Type VI

Tibial plateau fracture with diaphyseal discontinuity (metaphyseal-diaphyseal separation)

Findings

Fracture Lines

Visible breaks or cracks in the tibial plateau, often involving the lateral or medial condyles.

• Depression of the Articular Surface

The tibial plateau may appear sunken or compressed due to the impact.

6.Ankle fractures

Refer to breaks in one or more bones that make up the ankle joint, including the tibia, fibula, and talus.

Ankle fractures are classified using the Weber classification

Type A

• Fracture below the syndesmosis.

Type B

Fracture at the level of the syndesmosis.

Syndesmosis :an immovable joint in which bones are joined by connective tissue (e.g. between the fibula and tibia at the ankle)

Type C

Fracture above the syndesmosis.

Findings

Fracture Lines

Visible breaks or cracks in the bones, commonly involving the medial or lateral malleolus.

Joint Misalignment

Disruption of the normal alignment of the ankle joint, indicating instability.

Dislocation of the shoulder

It is the commonest joint dislocated in the body, accounting for 50% of all dislocations. It is however, uncommon in children.

• It can be classified by the direction of the dislocation with respect to the glenoid;

— Anterior (95%)

• — posterior (4%)
• — inferior

— Superior

Anterior dislocation

It is the most common form of shoulder dislocation (95%).

The humeral head is displaced anteriorly and beneath the coracoid or, less commonly, below the inferior rim of the glenoid.

The humeral head is displaced medially and overlies the glenoid; the dislocation is known as anterior.

• 15% associated with fracture of the greater tuberosity.
• 8% associated with fracture of the anterior glenoid.
• 40% of dislocations are recurrent. In chronic cases, there is a compression defect on the posterolateral surface of the humeral head.

Posterior dislocation

Rare form of dislocation, but over 50% are missed at the time of initial examination.

Following dislocation, the humerus is fixed in internal rotation. This gives the so-called “light bulb” appearance to the humeral head.

Other signs on the AP projection include loss of congruity of the glenohumeral joint. The posterior displacement is easily seen on a lateral projection.

Inferior dislocation

COMMUNICATING AXIAL AND APPENDICULAR RADIOGRAPHIC FINDINGS

Structured approach to communicating axial and appendicular radiographic findings for clinical reports or discussions:

Axial Skeleton (Spine, Pelvis, Skull, Ribs)

• Examples:

Degenerative Disc Disease (Lumbar Spine)

"The L4-L5 level shows disc space narrowing with anterior osteophytes and endplate sclerosis, consistent with moderate degenerative disc disease. No spondylolisthesis is noted."

Ankylosing Spondylitis (SI Joints)

"Bilateral sacroiliac joints exhibit erosions and subchondral sclerosis with early ankylosis, hallmark features of ankylosing spondylitis. Vertebral squaring is present at L3-L5."

Pelvic Fracture (Trauma)

"There is a displaced fracture of the right superior pubic ramus with 5 mm medial displacement. The sacroiliac joints remain aligned, indicating a stable injury."

Appendicular Skeleton (Limbs, Joints)

• Examples:

Osteoarthritis (Knee):

"The medial compartment of the knee demonstrates asymmetric joint space narrowing, subchondral sclerosis, and marginal osteophytes, consistent with moderate osteoarthritis. No effusion is seen."

Colles’ Fracture (Wrist)

"A transverse fracture of the distal radius is present with dorsal angulation of 15° and radial shortening, compatible with a Colles’ fracture. The ulnar styloid is intact."

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Skeletal System

Ankle fractures are classified using the Weber classification which categorizes ankle fractures based on the location of the fibula fracture(lateral malleolar fracture) relative to the tibio- fibular syndesmosis. It has a role in determining treatment.

Type A

• The fibula fracture below the syndesmosis(infrasyndesmotic).
• Usually transverse
• Tibiofibular syndesmosis intact

Medial malleolus occasionally fractured Syndesmosis :an immovable joint in which bones are joined by connective tissue (e.g. between the fibula and tibia at the ankle)

Type B

• The fibula fracture at the level of the syndesmosis (trans-syndesmotic).
• Usually spiral
• Tibiofibular syndesmosis usually intact

Medial malleolus may be fractured

Type C

• The tibial fracture above the syndesmosis (suprasyndesmotic).

Medial malleolus fractured

Tibiofibular syndesmosis disruption with widening of the distal tibiofibular articulation.

Dislocation of the shoulder

It is the commonest joint dislocated in the body, accounting for 50% of all dislocations. It is however, uncommon in children.

• It can be classified by the direction of the dislocation with respect to the glenoid;

— Anterior (95%)

— Posterior (4%)

• — Inferior

—

Shoulder joint

Anterior dislocation

It is the most common form of shoulder dislocation (95%).

The humeral head is displaced anteriorly and beneath the coracoid or, less commonly, below the inferior rim of the glenoid.

The humeral head is displaced medially and overlies the glenoid; the dislocation is known as anterior.

Anterior dislocation usually occurs due to forceful external rotation while the arm is out.

• 15% associated with fracture of the greater tuberosity.
• 8% associated with fracture of the anterior glenoid.
• 40% of dislocations are recurrent. In chronic cases, there is a compression defect on the posterolateral surface of the humeral head.

Posterior dislocation

Rare form of dislocation, but over 50% are missed at the time of initial examination.

Following dislocation, the humerus head is fixed in internal rotation, meaning it has a rounded appearance, the so-called “light bulb sign”.

• Other signs on the AP projection include loss of congruity of the glenohumeral joint.

The posterior displacement is easily seen on a lateral projection.

Congruity: degree of matching or agreement btn the shapes and sizes of the articulating bone surface.

Salter-Harris classification

The Salter-Harris classification is a system used to categorize fractures that involve the growth plate, or physis, in children.

It helps determine the severity of the injury and guide treatment decisions. The classification divides fractures into five types (I-V), based on the extent of involvement of the epiphysis, physis, and metaphysis.

Types of Salter-Harris Fractures:

Type I:

• A fracture that passes through the growth plate (physis).

Type II:

A fracture that passes through the growth plate and the metaphysis (the area above the growth plate).

Type III:

A fracture that passes through the growth plate and the epiphysis (the area below the growth plate).

• Type IV:
• A fracture that passes through the growth plate, metaphysis, and epiphysis.

Type V:

A crushing injury to the growth plate, resulting in a decrease in the perceived space between the epiphysis and metaphysis on X-ray.