Traumatic Disorders

R.-J. Schroeder, M. Lorenz, J. Jerosch, and J. Maeurer

2 Traumatic Disorders

Fractures

Definition

A fracture is a complete or incomplete break in a bone, with or without dislocation, following direct or indirect trauma or in the absence of trauma.

Pathology

macroscopic:

– disruption in cortical and/or cancellous bone

– varus/valgus malalignment

– bone marrow contusion

– associated soft tissue injury

microscopic:

– edema

– hemorrhage

– cortical disruption

– trabecular disruption

– compressed trabecular bone

– periosteal tear

– cartilage defects/disruption

Open/Closed Fractures

soft tissue damage:

– closed fracture

– grade I open fracture: destruction of soft tissue (due to cartilage fragments) from inside

– grade II open fracture: destruction of soft tissue from outside

– grade III open fracture: extensive soft tissue destruction involving skin, muscle, vessels, and/or nerves

Fracture Types

complete fractures:

– chisel fracture

– transverse fracture

– oblique fracture

– bending fracture

– torsion or spiral fracture

– segmental fracture (blow to larger surface area)

– defect fracture

– comminuted fracture (more than six fragments)

incomplete fractures:

– infraction

– fissure

– occult fracture

– bone bruise

– greenstick fracture

Clinical Signs

Deformity

abnormal mobility

crepitation

functional loss

localized spontaneous pain, tenderness, pain with movement

local swelling

local bruising

Diagnostic Evaluation

(→ method of choice for detecting fractures)

localization and extent of fracture

fracture type (according to AO classification, if possible)

joint involvement

fragment (dis)location:

– axially

– laterally

– longitudinally with/without contracture

– peripherally

(→ supplementary method, depending on the physician’s preference)

joint effusion

hematomas

associated injury to ligaments, tendons, muscles, menisci, joint capsules

functional test (abnormal mobility, instability)

fracture diagnosis (gap width, joint surface involvement, signs of consolidation)

(→ complementary method of choice)

optimized fracture typing (preferably according to AO classification)

exact determination of localization and extent of fracture

longitudinal displacement and degree of malrotation, comparing sides

joint involvement

associated soft tissue damage

fragment (dis)placement

number and size of fragments

intra-articular loose bodies

Keywords

knee joint, conventional radiography, ultrasound, computed tomography, magnetic resonance imaging

(→ complementary method)

occult fractures

detection/confirmation of fatigue breaks and stress fractures

osteochondral fractures/dissection

cartilage damage

intra-articular loose bodies

associated soft tissue damage (tendons, muscles, collateral ligaments, cruciate ligaments, patella retinaculae, menisci)

effusion, hematoma

functional test

Fracture Causes

Traumatic Fractures

Keywords

knee joint, traumatic fracture, bone marrow hematoma, bone bruise

Definition

A traumatic fracture is a complete or incomplete break in a bone with or without dislocation, caused by one-time excessive stress on its physiological elasticity from a direct or indirect blow.

Role of Imaging

demonstrate anatomy of bony and soft tissue structures

demonstrate full extent of cortical and cancellous bone fractures and soft tissue damage

demonstrate fragment shape, position and localization, intrarticular loose bodies, and articular surface involvement

demonstrate relationship of injured bony and soft tissue structures to one another

demonstrate local or systemic processes causing bone destruction and soft tissue infiltration

Pathology

macroscopic:

– disruption in cortical and/or cancellous bone

– varus/valgus malalignment

– bone marrow contusion

– associated soft tissue injury

microscopic:

– edema

– hemorrhage

– trabecular disruption

– compressed trabecular bone

– periosteal tear

– cartilage defects/disruption

Fracture Localization

distal femur:

– extra-articular metaphyseal

– partially/completely intra-articular

– wedge fracture

– simple/multifragmentary

– unicondylar/bicondylar

proximal tibia:

– extra-articular metaphyseal

– partially/completely intra-articular

– split/depression fracture

patella:

– differential diagnosis (DD) bipartite/tripartite patella (congenital, asymptomatic, predominantly among men, unilateral in 50%, craniolateral in three-quarters of cases, otherwise lateral or cranial, no hematoma/edema, no bone bruise)

Tibial Plateau Fracture Classification (Based on Mueller)

grade I: undisplaced vertical or wedgeshaped fracture

grade II: central depression of medial or lateral joint surface

grade III: vertical or wedgeshaped fracture with central depression of medial or lateral joint surface and proximal fibula fracture

grade IV: comminuted fracture involving medial and lateral joint surface and proximal fibula fracture

Tibial Plateau Fracture Classification (Based on Hohl)

grade I: undisplaced vertical sagittal fracture

grade II: central depression of medial or lateral joint surface

grade III: displaced vertical sagittal fracture with central depression of medial or lateral joint surface and sometimes proximal fibular head fracture

grade IV: displaced entirely medial joint surface depression without comminution

grade V: undisplaced vertical coronal anterior or posterior fracture without depression

grade VI: comminuted fracture involving medial and lateral joint surfaces and possibly fibular head fracture

Clinical Signs

Deformity

abnormal mobility

crepitation

functional loss

local spontaneous pain, tenderness, and pain with movement

local swelling

local hematoma

Diagnostic Evaluation (Figs. 2.1–2.6)

(→ method of choice)

Recommended Radiography Projections

standard projections:

– anteroposterior (AP) projection

– lateral projection, mediolateral roentgen ray path

special projections (depending on fracture localization):

– Tunnel view/Notch view to demonstrate intercondylar fossa and eminence

– axial projection of the patella

– “defilée” views (axial projection with knee bent 30°, 60°, 90°) of the patella to demonstrate the patellofemoral joint

– 45° oblique views for better evaluation of the tibial plateau and proximal fibula

conventional tomography:

– almost entirely replaced by multislice CT and two-dimensional/three-dimensional (2-D/3-D) reconstructions

– maybe indicated for postoperative surveillance (position, “knitting together” of bones) if more extensive metal implants are causing artifacts in CT

Findings

Path of fracture lines

fracture localization and extent

fragment (dis)placement

number of fragments

fracture type (according to AO classification, if possible)

joint involvement

Fig. 2.1 a–e Complex lateral tibial plateau fracture (left side).

a, b AP projection and lateral view. Conventional radiography demonstrates a complex lateral tibial plateau fracture on the left side with involvement of the tibial plateau (arrow), split fracture (arrowheads; type II based on Moore/B3 in AO classification) and dorsal displacement (small arrows in b).

c Axial CT demonstrates full extent of lateral infraction of the tibial plateau (arrow).

d Split fracture documented in coronal 2-D reconstruction (arrow tips).

e After osteosynthesis using plates (arrow-heads) and screws (small arrows) the tibial plateau is completely reduced (large arrow).

Fig. 2.2 a–f Lateral tibial plateau fracture.

a, b Radiography projection in two planes of a lateral tibial plateau fracture ascending to medial (small arrows) involving the intercondylar eminence (arrow-head), and exhibiting a tibial plateau depression (dotted arrow) corresponding to a type II fracture (based on Moore).

c, d Coronal two-dimensional CT reconstructions.

e, f A three-dimensional CT reconstruction facilitates operation planning and shows clearly the extent of articular surface involvement (arrowheads), degree of depression, and fragment position, especially at the intercondylar eminence (large arrow).

Fig. 2.3 a–f Complex tibial plateau fracture.

a, b AP and lateral projections. Even conventional radiographic projections allow detection of a complex tibial plateau fracture with lateral plateau depression (arrows) following dislocation of the knee joint.

c, d 2-D reconstruction of the CT data set enables exact classification as a type IV fracture (based on Moore) with a lateral tibial plateau depression (arrows).

e, f 3-D reconstruction offers a better view of the overall situation and extent of the lateral depression (arrow), thus providing the surgeon with valuable additional information.

Fig. 2.4 a–k Comminuted fracture of the tibial plateau.

a, b AP and lateral projections show the extensive involvement of the articular surface (small arrows) and separation of the intercondylar eminence (arrow) from the shaft (arrowhead) and from both condyles (broken arrow) as a type V fracture (based on Moore).

c, d Coronal and sagittal 2-D reconstructions.

e-i 3-D reconstruction is especially advantageous for surgical planning with such complex fractures. The joint fragments (small arrows), shaft fracture (arrow-heads), and separation (large arrows) of the intercondylar eminence are clearly demonstrated in their complex relationship to one another.

j, k Postoperative condition after osteosynthesis using plates (small arrows) and a screw (large arrow).

Fig. 2.5 a–i Complex comminuted fracture of the tibial plateau.

a, b AP and lateral projections show a complex comminuted fracture of the tibial plateau with extensive involvement of the articular surface (small arrows), separation of the intercondylar eminence (large arrow) from the shaft (arrowhead) and separation of both condyles (striped arrow) as in a type V fracture (based on Moore).

c, d 2-D reconstruction, in the coronal and sagittal planes, allows an exact depiction of the overall situation.

e–i 3-D reconstructions, in particular, provide important additional information for surgical planning. Joint fragments (small arrows), the shaft fracture (arrowheads), separation of the condyles (striped arrow), and the separation (large arrow) of the intercondylar eminence are clearly visible here in their relation to one another.

Fig. 2.6 a–i Avulsion of the cruciate ligament and fracture of the tibial plateau.

a, b This AP radiograph shows a bony avulsion of the anterior cruciate ligament (large arrow), lateral projection additionally shows a displaced fracture of the dorsal tibial plateau (small arrows).

c Using MRI a T1 SE sequence shows the small bony fragment from the tibial avulsion of the anterior cruciate ligament and a surrounding hypointense bone bruise.

d, e 2-D CT reconstructions in the sagittal and coronal planes are best suited for showing the extent of the fracture of the dorsal tibial plateau as well as fragment position (small arrows).

f, g This also applies to the corresponding planes on the T1 SE sequence.

h, i 3-D reconstruction can optimize the overall view, demonstrating the extent of fracture (bold arrow) of the posterolateral tibial plateau and the intercondylar eminence fragment (dotted arrow).

(→ complementary method, not clinically relevant for fracture diagnosis)

Recommended Imaging Planes

suprapatellar longitudinal and transverse scan

infrapatellar longitudinal scan

medial and lateral imaging plane

posterior longitudinal plane

Findings

effusion

associated injury to ligaments, tendons, muscles, menisci, joint capsule

functional test (abnormal mobility, instability)

fracture diagnosis (gap width, joint surface irregularity, signs of consolidation)

(→ complementary method of choice)

Recommended Imaging Mode

standard CT:

– slice thickness: 1–2 mm

– table increment: 1–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction: if joint surface involvement, subtraction of unfractured bones for an unobstructed view of position of fractured articular surface

(multislice) spiral CT:

– slice thickness: 0.5–2 mm

– table increment: 2–5 mm/rotation

– increment: 0.5–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction: if joint surface involvement, subtraction of unfractured bones for an unobstructed view of position of fractured articular surface

Findings

exact determination of localization and extent of fracture

longitudinal displacement and degree of malrotation, comparing sides

joint involvement

number and size of fragments

fragment (dis)placement

intra-articular loose bodies

optimized fracture typing (preferably according to AO classification)

(→ complementary method, especially for occult fractures, DD bipartite/tripartite patella vs. fracture)

Recommended Sequences

fat-suppressed sequences whenever possible (with the exception of plain T1-weighted [T1] sequence)

coronal plain short tau inversion recovery (STIR) sequence

sagittal and possibly coronal plain T1 and T2-weighted (T2) turbo spin-echo (TSE) sequences (depending on clinical question)

axial (patellar chondral surface) and/or coronal or sagittal plain fat-saturated, proton density-weighted spin-echo (PD SE) or fat-saturated 2-D or 3-D gradient-echo (GE) sequences for cartilage imaging

possibly 15–20° angled T1 sequences parallel to the course of the anterior cruciate ligament (ACL) and/or posterior cruciate ligament (PCL) (preferably following administration of a contrast agent if contrast enhancement used in exam)

possibly angled T1 sequences parallel to the course of the suspected ruptured tendon

possible contrast enhancement:

to identify fracture gap

– with osteochondral fragments for demonstrating the extent and degree of perfusion/tissue viability

– to better differentiate between traumatic and inflammatory lesions

– postsurgery to differentiate between ligament replacement and granulation tissue or between traumatic and postoperative scarring and granulation tissue

Findings

general:

– cartilage, bone, or osteochondral fractures

– determination of fracture age

– cartilage damage

– detection of earlier occult fractures (possibly more than one year old)

– pseudarthrosis

– lateral contusion zone with medial ligament lesion

– medial contusion zone with lateral ligament lesion

– posterolateral contusion zone with ACL lesion (recognizable for up to three-quarters of a year, localization always epimetaphyseal)

– potential simulation of bone bruise by nonfatty areas in the bone marrow

– potential fracture simulation by incomplete ossification of the epiphyseal plate

– possible simulation of traumatic lesions by benign (nonossifying fibroma, fibrous cortical defect, benign fibrous histiocytoma, cysts, giant cell tumor) or malignant tumors

plain T1 SE sequence:

– hypointense fracture gap or pseudarthrosis

– patchy, poorly demarcated hypointense bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense demonstration of an osteochondral fragment/surrounding sclerotic margin/osteochondral defect

plain STIR/T2-weighted (T2) SE sequence:

– hyperintense fracture gap or pseudarthrosis

– patchy, poorly demarcated hyperintense bone bruise (bone marrow hematoma/bone marrow edema)

– hyperintense edematous osteochondral fragment/osteochondral lesion

– hypointense demonstration of sclerotic osteochondral fragment/surrounding reactive sclerotic margin

contrast-enhanced T1 SE sequence (preferably fat saturated):

– hypointense fracture gap, hyperintense/hypointense pseudarthrosis (depending on extent of granulation tissue and sclerosis)

– patchy, poorly demarcated hyperintense or hypointense bone bruise (bone marrow hematoma/bone marrow edema)

– hyperintense to hypointense demonstration of osteochondral fragment

– hypointense demonstration of sclerotic margin/osteochondral lesion

fat-saturated PD 2-D GE/3-D GE sequences:

– hyperintense areas of cartilage damage

Basic Treatment Strategies

conservative or operative treatment depending on fracture type

especially with joint involvement: open reduction and internal fixation (ORIF)

Pathologic Fracture

Definition

A pathologic fracture is a complete or incomplete disruption in continuity of bone with local or diffuse pathologic osseous changes. Fracture mayoccur without trauma or as the result of insignificant trauma with or without dislocation.

The cause of fracture may be a result of benign or malignant processes.

Keywords

knee joint, pathologic fracture, spontaneous fracture, insufficiency fracture, osteolysis

Pathology

macroscopic:

– disruption in cortical and/or cancellous bone

– destruction of bone surrounding the fracture

– dislocation, varus/valgus malalignment

– bone marrow hematoma

– associated soft tissue injury

– soft tissue changes related to local destructive bone processes

microscopic:

– edema

– hemorrhage

– trabecular disruption/compressed trabecular bone

– absence of callus formation

– bone and soft tissue changes related to local destructive bone processes

– traumatic and nontraumatic uninterrupted or interrupted periosteal reaction

– cartilage defects

Role of Imaging

demonstration of full extent of cortical and cancellous fractures as well as injury to soft tissue structures

demonstration of fragment shape, position, and localization

demonstration of joint and joint surface involvement

evaluation of local (in)stability

demonstration of full extent of intraosseous and extraosseous pathologic processes

relation to surrounding vessel–nerve structures

signs of additional tumor manifestations

Clinical Signs

deformity

abnormal mobility

crepitation

functional loss

localized spontaneous pain, tenderness, pain with movement

local swelling

local bruising

local soft tissue changes associated with local destructive processes of the bone or underlying systemic disease

Diagnostic Evaluation

(→ method of choice)

Recommended Radiography Projections

standard projections:

– AP projection

– lateral projection, mediolateral roentgen ray path

special projections (depending on fracture localization):

– Tunnel view/Notch view to demonstrate intercondylar fossa and eminence

– axial projection of the patella

– “defilée” views (axial projection with knee bent 30°, 60°, 90°) of the patella to demonstrate the patellofemoral joint

– 45° oblique views for better evaluation of the tibial plateau and proximal fibula

conventional tomography:

– almost entirely replaced by multislice CT and 2-D/3-D reconstructions

– at most may be indicated for postoperative surveillance (position, integration) if extensive metal implants are causing artifacts in CT

Findings

path of fracture lines

fracture localization and extent

fragment (dis)placement

number of fragments

fracture type (preferably according to AO classification)

joint involvement

local destructive bone processes

thickening of soft tissue

systemic changes in bone structure (e.g., osteoporosis)

(→ complementary method)

Recommended Imaging Planes

suprapatellar longitudinal and transverse scan

infrapatellar longitudinal scan

medial and lateral imaging plane

posterior longitudinal plane

Findings

effusion

associated injury to ligaments, tendons, muscles, menisci, joint capsule

functional test (abnormal mobility, instability)

fracture diagnosis (gap width, joint surface involvement, signs of consolidation)

cortical destruction

soft tissue masses/infiltration

associated soft tissue reaction

(→ complementary method)

Recommended Imaging Mode

standard CT:

– slice thickness: 1–2 mm

– table increment: 1–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction for complete imaging of destruction or masses

(multislice) spiral CT:

– slice thickness: 0.5–2 mm

– table increment: 2–5 mm/rotation

– increment: 0.5–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction for complete imaging of destruction or masses

Findings

exact determination of localization and extent of fracture

joint involvement

number and size of fragments

fragment (dis)placement

intra-articular loose bodies

optimized fracture typing (preferably according to AO classification)

local bone destruction associated with underlying disease

soft tissue involvement associated with local destructive bone processes

systemic changes to bone structure (e.g., osteoporosis)

longitudinal displacement and degree of malrotation, comparing sides

(→ complementary method of choice)

Recommended Sequences

fat-suppressed sequences should be used whenever possible (with the exception of plain T1 sequence)

coronal STIR sequence

plain sagittal T2 TSE sequences

plain sagittal or coronal T1 SE sequences (depending on clinical question)

contrast-enhanced axial and sagittal and/or coronal T1 SE sequences (depending on clinical question) to identify fracture gap and intramedullary or extramedullary tumor infiltration

if needed, contrast-enhanced opposed-phase sequences to identify further tumor manifestations in the axial skeleton

Findings

plain T1 SE sequence:

– hypointense fracture gap

– patchy, poorly demarcated hypointense bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense and/or hyperintense intramedullary and extramedullary connective tissue tumor

plain STIR/T2 SE sequence:

– hyperintense fracture gap

– patchy, poorly demarcated hyperintense bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense and/or hyperintense intramedullary and extramedullary connective tissue tumor

contrast-enhanced T1 SE sequence (fat saturated except with lipomatous tumors):

– hypointense fracture line

– patchy, poorly demarcated hyperintense to hypointense bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense intramedullary and extramedullary connective tissue tumor (depending on tumor perfusion)

– contrast-enhanced opposed-phase sequences of axial skeleton:

– hyperintense demonstration of additional tumor manifestations

(→ complementary method)

Recommended Imaging Mode

planar (whole body) and/or SPECT (spot imaging) skeletal nuclear medicine

administration of 550–750 MBq or 7.4–11.1 MBq/kg ^99mTc-MDP per i.v.

Findings

demonstration of extent of local tumor infiltration

increased uptake at sites of additional tumor manifestations in the skeletal system

Basic Treatment Strategies

Benign processes

single or (possibly) two-session removal and reconstruction using autograft or allograft

Joint preservation

compound osteosynthesis

Joint replacement

total knee endoprosthesis

allograft reconstruction

composite allograft reconstruction

Fatigue Fracture, Stress Fracture

Definition

A complete or incomplete disruption in continuity of a healthy bone resulting from repetitive overuse with or without dislocation is known as a fatigue fracture or stress fracture.

Pathology

macroscopic:

– disruption in cortical and/or cancellous bone

– endosteal and periosteal new bone formation

– bone marrow hematoma

– associated reactive soft tissue changes

microscopic:

– microfractures

– imbalance in osteoblastic and osteoclastic cell activity

– osteoclastic resorption zones with areas of new lamellar bone formation

– edema

– hemorrhage

– trabecular disruption/compressed trabecular bone

– reactive soft tissue changes related to local bone processes

– cartilage defects

Clinical Signs

pain at rest, pain with excessive activity (e.g., long-distance runners)

localized spontaneous pain, tenderness, pain with movement

local swelling

functional loss

other fracture signs generally mild if present at all

often no symptoms

often low body weight (especially among women)

Keywords

knee joint, stress fracture, fatigue fracture, bone marrow edema

Role of Imaging

primary detection of stress fracture

demonstration of full extent of fracture or area of bone transformation

demonstration of fragment position

demonstration of articular surface involvement and cartilage lesions

demonstration of possible soft tissue injury

demonstration of additionally overloaded osseous structures at risk for fracture as well as soft tissue structures demonstrating inflammatory reactive processes or at risk of rupture

evaluation of local (in)stability

Diagnostic Evaluation

(→ method of choice)

Recommended Radiography Projections

standard projections:

– AP projection

– lateral projection, mediolateral roentgen ray path

special projections (depending on fracture localization):

– Tunnel view/Notch view to demonstrate intercondylar fossa and eminence

– axial projection of the patella

– “defilée” views (axial projection with knee bent 30°, 60°, 90°) of the patella to demonstrate the patellofemoral joint

– 45° oblique views for better evaluation of the tibial plateau and proximal fibula

conventional tomography:

– almost entirely replaced by multislice CT and 2-D/3-D reconstructions and MRI

Findings

mild or early-stage fracture:

– minimal surrounding soft tissue edema possible

– increased cortical transparency and blurriness

– positive scintigram

moderate or later-stage fracture:

– lamellar periosteal reaction

– bone marrow edema

– positive MRI

severe or late-stage fracture:

– ossifying periostitis (reactive apposition of osteosclerotic lamellar bone)

– endosteal thickening

– poorly defined, sclerotic, linear condensation of cancellous and cortical bone along the fracture line

– surrounding soft tissue edema or hematoma

– positive radiograph

Basic Treatment Strategies

Without dislocation

relatively early physical therapy

temporary immobilization

possible temporary orthosis

possible temporary orthopedic shoes

possible short-term calcium and vitamin D supplements

With dislocation

reduction

fixation

(→ complementary method)

Findings

no diagnostic value

(→ complementary method)

Recommended Imaging Mode

standard CT (no longer up-to-date):

– slice thickness: 1–2 mm

– table increment: 1–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction generally of little use given lacking dislocation

(multislice) spiral CT, possibly in addition to MRI:

– slice thickness: 0.5–2 mm

– table increment: 2–5 mm/rotation

– increment: 0.5–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction of little use given lacking dislocation

Findings

detection and demonstration of fracture line

demonstration of surrounding reactive sclerotic zone

(→ complementary method of choice)

Recommended Sequences

fat-suppressed sequences should be used whenever possible (with the exception of plain T1 sequence)

coronal STIR sequence

plain sagittal T2 TSE sequences

plain axial, sagittal, and/or coronal T1 SE sequences (according to clinical question) depending on suspected fracture localization

contrast-enhanced imaging to identify fracture gap and potential intramedullary/extramedullary tumor infiltration or osteomyelitis

MRI Classification Based on the Cincinnati Knee Rating System

grade I:

– hyperintense on STIR images

– unremarkable on T1 sequences

– involving marrow cavity only

grade II:

– hyperintense on STIR images

– hypointenseon T1 sequences

– involving marrow cavity only

grade III:

– hyperintense on STIR images

– hypointenseon T1 sequences

– involving marrow cavity and cortical bone

grade IV:

– hyperintense on STIR images

– hypointense on T1 sequences

– involving marrow cavity, cortical bone, and cartilage

Findings

plain T1 SE sequence:

– hypointense fracture gap, if detectable

– patchy, poorly defined hypointense bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense demonstration of cancellous and cortical sclerosis

– hypointense demonstration of surrounding soft tissue edema/hematoma (the latter depending on hemorrhage age)

plain STIR/T2 SE sequence:

– hyperintense fracture gap

– patchy, poorly defined hyperintense bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense demonstration of cancellous and cortical sclerosis

– hypointense demonstration of surrounding soft tissue edema/hematoma (the latter depending on hemorrhage age)

contrast-enhanced T1 SE sequence (preferably fat saturated):

– hypointense fracture gap

– patchy, poorly defined hyperintense to hypointense bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense demonstration of cancellous and cortical sclerosis

(→ complementary method)

Recommended Imaging Mode

planar (whole body) and/or SPECT (spot imaging) skeletal nuclear medicine

administration of 550–750 MBq or 7.4–11.1 MBq/kg ^99m Tc-MDP per i.v.

Findings

increased uptake at fracture sites even in the earliest stages

Chondral and Osteochondral Fractures

Definition

Chondral and osteochondral fractures involve traumatic damage to the cartilage and the subchondral bone, caused by excessive shearing and/or rotational forces, and may be associated with the formation of loose intra-articular osteochondral fragments.

Pathology

traumatic chondral, cortical, and cancellous fragment separation

compression, impaction, and/or cancellous subchondral fracture with intact cartilage

isolated traumatic cartilage damage

surrounding bone marrow edema/hematoma

Stages (Based on A. Greenspan)

stage I:

– undisplaced subchondral bone fragment

stage II:

– undisplaced cartilage and subchondral bone fragment

stage III:

– displaced cartilage, undisplaced subchondral bone fragment

stage IV:

– displaced cartilage and bone fragment

Clinical Signs

pain at rest, weight-bearing pain

nonspecific pain and limited function

joint obstruction

hemarthrosis/joint effusion

Diagnostic Evaluation

(→ initial method)

Recommended Radiography Projections

standard projections:

– AP projection

– lateral projection, mediolateral roentgen ray path

special projections (depending on fracture localization):

– Tunnel view/Notch view to demonstrate intercondylar fossa and eminence

– axial projection of the patella

– “defilée” views (axial projection with knee bent 30°, 60°, 90°) of the patella to demonstrate the patellofemoral joint

– 45° oblique views for better evaluation of the tibial plateau and proximal fibula

conventional tomography:

– almost entirely replaced by multislice CT and MRI

Findings

disruption/irregularity in cortical bone

subchondral condensation of bone

partial or complete fragment separation

displaced osteochondral fragment/intra-articular loose bodies

empty osteochondral lesion

(→ complementary method)

Recommended Imaging Planes

suprapatellar longitudinal and transverse scan

infrapatellar longitudinal scan

medial and lateral imaging plane

posterior longitudinal plane

Findings

joint effusion

associated reaction in surrounding soft tissues (low to high echogenicity possible)

demonstration of irregularity in cortical bone or empty osteochondral lesion

often fruitless however

(→ complementary method)

Recommended Imaging Mode

standard CT:

– slice thickness: 1–2 mm

– table increment: 1–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction

(multislice) spiral CT:

– slice thickness: 0.5–2 mm

– table increment: 2–5 mm/rotation

– increment: 0.5–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction

Findings

subchondral sclerosis

subchondral impaction of bone

empty osteochondral lesion

loose intra-articular osseous bodies

localization of the defect and fragments

(→ complementary method of choice)

Recommended Sequences

coronal STIR sequence

plain sagittal T2 TSE sequences

plain axial, sagittal, and/or coronal T1 SE sequences (according to clinical question) depending on presumed fracture localization

(fat-saturated) PD or 2-D GE/3-D GE sequences to demonstrate cartilage

contrast-enhanced imaging for evaluation of perfusion and demonstration of fracture gap

Findings

plain T1 SE sequence:

– hypointense fracture gap

– patchy, poorly defined hypointense subchondral bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense demonstration of cortical and cancellous sclerosis

– hypointense demonstration of fragment

plain STIR/T2 SE sequence:

– hyperintense fracture gap

– patchy, poorly defined hyperintense subchondral bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense demonstration of cortical and cancellous sclerosis

– hypointense demonstration of fragment

T1 SE sequence after administering a contrast agent (preferably fat saturated):

– hypointense fracture gap

– patchy, poorly defined hyperintense to hypointense bone bruise (bone marrow hematoma/bone marrow edema)

– hypointense demonstration of cortical and cancellous sclerosis

– hypointense to hyperintense demonstration of fragment depending on perfusion conditions

PD/GE sequences (preferably fat saturated):

– demonstration of cartilage damage

Keywords

knee joint, osteochondral fracture, flake fracture, cartilage lesion, bone marrow edema

Role of Imaging

demonstration of entire region of detachment and fragment size

demonstration of detachment site localization

demonstration of fragment displacement and intra-articular localization

demonstration of perfusion in the area of detachment

demonstration of surrounding osseous reaction and ligament condition

Basic Treatment Strategies

Without dislocation

temporary immobilization

possible relief of affected segment with a brace

With dislocation

arthroscopic or open reduction of the fragment

osteochondral cylinder transplantation (OCT)

Occult Fracture, Bone Bruise

Definition

An occult fracture is a subchondral bone contusion caused by trauma, which can only be identified by means of MRI.

Keywords

knee joint, bone marrow edema, bone bruise, occult fracture

Pathology

macroscopic:

– disruption in cancellous bone

– associated soft tissue injury

– bone marrow hematoma/edema

– epimetaphyseal localization

– localization more often lateral than medial

– often associated with contralateral collateral ligament injury

– posterolateral bone bruise of tibial plateau often with ACL rupture

– detectable up to 3/4 of a year post trauma

microscopic:

– edema

– hemorrhage

– no cortical disruption

– trabecular disruption

– compressed trabecular bone

– periosteal tear

– cartilage defects/disruption

Common Localizations

anterior femoral condyle/anterior tibial plateau with PCL rupture

posterior femoral condyle/posterolateral tibial plateau with ACL rupture

medial dorsal patella/lateral femoral condyle with patella dislocation

Role of Imaging

primary detection of fracture

extent of bone bruise

demonstration of potential cartilage damage

exclusion of (previously unnoticed) cortical disruption

demonstration of possible, associated soft tissue damage

Clinical Signs

localized tenderness

localized pain with movement

local swelling

joint effusion

Diagnostic Evaluation (Fig. 2.7)

(→ to exclude fracture)

Recommended Radiography Projections

standard projections:

– AP projection

– lateral projection, mediolateral roentgen ray path

special projections (depending on fracture localization):

– Tunnel view/Notch view to demonstrate intercondylar fossa and eminence

– axial projection of the patella

– “defilée” views (axial projection with knee bent 30°, 60°, 90°) of the patella to demonstrate the patellofemoral joint

– 45° oblique views for better evaluation of the tibial plateau and proximal fibula

conventional tomography:

– not indicated

Findings

generally does not assist in diagnosis

local thickening due to swelling/effusion

Findings

does not yield any diagnostic clues

(→ not very helpful, supplementary method)

Recommended Imaging Mode

standard CT:

– slice thickness: 1–2 mm

– table increment: 1–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction generally of little use given lacking dislocation

(multislice) spiral CT:

– slice thickness: 0.5–2 mm

– table increment: 2–5 mm/rotation

– increment: 0.5–2 mm

– 2-D reconstruction (sagittal and coronal): 1–2 mm slice thickness

– 3-D reconstruction generally of little use given lacking dislocation

Findings

joint effusion

hypodense edema/hematoma

generally does not assist in diagnosis

(→ procedure of choice for exact diagnosis)

Recommended Sequences

STIR sequence

plain T2 TSE sequences

plain T1 SE sequences

contrast-enhanced imaging only for excluding inflammatory or malignant lesions

Findings

general:

– differentiation between linear (previously undetected, undisplaced fracture with risk of dislocation) and purely diffuse (without recognizable fracture line demarcation) contusion

– depending on severity of primary fracture, detection of bone bruise up to two or even (rarely) nine months later

plain T1 SE sequence:

– inhomogeneously structured, irregular, and poorly demarcated (linear in occult fractures), hypointensity near the epimetaphyseal cortical bone

plain STIR/T2 SE sequence:

– inhomogeneously structured, irregular, and poorly demarcated (linear in occult fractures), hyperintensity (edema) to hypointensity (blood) near the epimetaphyseal cortical bone

contrast-enhanced T1 SE sequence (preferably fat saturated):

– marked inhomogeneous enhancement, except at fracture line

Fig. 2.7a,b Partially occult tibial plateau fracture.

a A conventional AP radiographic image can barely allow evaluation, of a partially, occult right lateral paramedian tibial plateau fracture (arrow).

b On a coronal T2 FR-FSE sequence the full extent of the fracture can now be seen running through the entire lateral tibial plateau and involving the intercondylar eminence (long arrow) with surrounding contusion (bone bruise, arrowhead).

Possible Classifications

Mink, Deutsch 1989:

– a bone bruise, like a stress fracture, belongs to a subgroup of occult fractures

Lynch et al. 1989:

– bone marrow contusion without (type 1) or with (type 2) disruption in cortical bone

Vellet et al. 1991:

– “reticular bone bruise” (= netlike alterations on MR views without subchondral involvement) or

– “geographic bone bruise” (=foci of discretely altered signal intensity involving subchondral bone) depending on contusion pattern and localization

Detmer 1986:

grade I: bone edema (increased signal intensity on T2 MRI sequences)

grade II: periosteal inflammation or edema

grade III: additional involvement of muscle

DD-Important Note

hematopoietic bone marrow: hypointense on T1 views, discretely hyperintense on T2 sequences

unclosed epiphyseal plate: intermediary signal on T1 views, slightly hyperintense on T2 sequences, mostly sharply contoured without surrounding blurry area

fibrous cortical defect, nonossifying fibroma: eccentric, clearly demarcated, involving cortical bone, often sclerotic margin (hypointense on T1 and T2 sequences), no contrast enhancement

Basic Treatment Strategies

possible temporary immobilization depending on clinical symptoms

Osteochondritis Dissecans

Definition

Osteochondritis dissecans describes the tendency of cartilage and/or bone fragments (usually elliptical in shape) to separate from a circumscribed area of subchondral osteonecrosis, causing an osteochondral defect and the formation of an intra-articular loose body. Disease etiology remains uncertain, though trauma, microembolisms, and constitutional factors have been suggested. There is no sex predilection. Traumatic causes are more often found among younger patients active in sports. Spontaneous osteonecrosis of the knee (SONK) is more often found among older, women patients and is frequently associated with cartilage or meniscal lesions and joint effusion.

Pathology

may be similar to osteonecrosis depending on stage

osteonecrosis found more frequently among women (75%), older ages, combined with cartilage/meniscal lesions and joint effusion

Stages

(Modified Based on J. Kramer et al.)

stage I:

– subchondral edema, nonspecific

stage II (undisplaced cartilage and bone fragment):

– demarcated by narrow sclerotic margin

– possible limited bone marrow changes next to demarcation

stage III (undisplaced cartilage and bone fragment):

– fibrovascular scar within sclerotic border

– separation beginning near the edges

– sometimes cyst formation in adjacent bone

stage IV (displaced cartilage, undisplaced bone fragment):

– completely loose fragment at the detachment site, usually surrounded by fluid

stage V (displaced cartilage and bone fragment):

– dislocation of the fragment

– increasing bony flattening of the osteochondral defect

Keywords

knee joint, ischemic disease, posttraumatic lesion, osteochondritis dissecans, osteonecrosis

Role of Imaging

primary detection of lesion

demonstration of extent and severity of cartilage damage

demonstration of intra-articular loose bodies

evaluation of viability and subchondral stability

evaluation of condition of surrounding bone

Localization

ca. three-quarters on the medial surface of medial femoral condyle

ca. one-tenth on the weight-bearing surface of the medial femoral condyle

ca. one-tenth on the weight-bearing surface of the lateral femoral condyle

clearly less frequent in other regions of the femoral condyles or patella

SONK is more common on weight-bearing surfaces of the medial femoral condyle while osteochondritis dissecans is more common on its non-weight-bearing surfaces