17 Fracture and Dislocation

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FRACTURE AND DISLOCATION

SKELETAL TRAUMA

one of the most important aspects of orthopaedic radiology

commonest problem presented to the musculoskeletal radiologist

FRACTURE occurs when there is a break in the continuity of bone

either complete or incomplete

When a loading force is applied to bone, it initially deforms elastically, and as the load isremoved, the deformity of the bone is reversed and the bone returns to normal.

As the loading force is increased, however, the elasticity of the bone is overcome, and aplastic fiture' occurs, with the bone remaining deformed after cessation of the load.

Finally, complete failure of the bone will occur, giving rise to a true fracture.

Repetitive loading of a bone at `subfracture' levels may lead to the development ofstress fracture

TERMINOLOGIESOpen fracture

Bone fragments penetrate the skin

A comminuted fracture of the tibia, with medialdisplacement and overriding of the distal fragment. Because ofthe Proximity of the skin surface to the anteromedial aspect ofthe tibia, penetration of the skin is likely, and in fact, air is seenin the soft tissues, indicating that penetration is medialdisplacement, but lateral has occurred. There angulation of thedistal fragment. A segmental fibula fracture is noted.

Radiographic signs of open fracture Obvious prorusion of bone fragments beyond the soft tissue margins

Absence of portions of the bone

Gross soft tissue disruption extending to the bone surface

Subcutaneous gas

Foreign material within the fracture

Closed fracture

fracture remains covered with intact skin

Nature of the fracture lines three major types

o transverseo oblique oro spiralo combination

Comminuted fracture

the injury produces more than one fracture line willoften produce a minor triangular fragment of bone,known as a ` butterfly' fragment

RADIOLOGY FRACTURE AND DISLOCATION Page 1


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Segmental fracture

o one in which a segment of bone isisolated by fractures at each end

Segmental fracture of thefemur: by definition acomminuted fracture. In this

case the isolated segment isclearly malaligned

Incomplete fractures

occur most commonly in children, when bone resilience is greater, and are of

three typeso plastic fractures

occur when there is bending of the bone without cortical disruption, oracute angulation

o `torus' or ` buckle' fracture

fracture of the cortex on the compressive side of the bone with anintact cortex on the tension side (Fig. 43.4):

Torus fracture of the radius. The cortex isbuckled on the dorsal surface. Apart fromminor plastic deformity, the volar surfaceis intact.

o greenstick fracture converse of the torus fracture, occurring only on the tension side, with

cortical interception

Fractures should also be evaluated for continuity and proximity of the fracture fragments apposition position of the major fragments with respect to each other

distracted fragments which are not apposed are described as being displacementalong the long axis of the bone, or displaced, away from the long axis

o fracture should be described according to the direction of displacement of thedistal fragment relative to the proximal bone

Alignment

refers to the relationship along the axis of major fragments

described in two wayso most logical description refers to the alignment of the distal fragment with

respect to the proximal

additional advantage of following the same rules' as apply todisplacement

o describe the angulation as the direction of the apex of the angle at thefracture site

Alternative method, commonly used by orthopaedic surgeons



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Varus and valgus angulation are terms that are commonly used,particularly by orthopaedic surgeons

refer to the alignment of the distal fragment with respect to themidline of the body, with

o varus angulation of the distal fragment towards the

midlineo valgus reverse

Impaction

descriptive term for fractures in which the bone fragments are driven into each other

ASSOCIATED SOFT TISSUE ABNORMALITIESJoint effusion or hamarthrosis

fractures around a joint providing the joint capsule remains intact

useful at the elbow, where elevation of the pads, either anterior or posterior, is goodevidence of injury

Elbow effusion: elevation of the anterior fat pad (arrow).Although not pathognomonic for fracture, anterior fat pad elevationindicates significant effusion, and is frequently associated with afracture. Careful Inspection of the unfused radial head shows a minorcortical stepoff of the metaphysis, indicating a fracture

lipohamarthrosis



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fat fluid level within a joint

most commonly seen in the knee with radiograph made with a horizontal beam

firm presumptive evidence of an intra articular fracture

Fat fluid level is seen in the knee joint on this cross table view.This indicates intra-articular bone injury.

Soft-tissue swelling in the retropharyngcal space

being a reliable sign of cervical spine trauma

Compression fractures of the vertebral bodies of T7, T8and T9 with large paraspinal haematoma, which took

many months to absorb, still being visible after thefracture had consolidated.

FRACTURE HEALING

After a fracture has occurred, the process of healing begins.



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Stages of healing after a fracture

Considerable bleeding occursat the fracture. The blood liesbetween the bone ends andunder the periosteum.

In a few days a blood clot

forms. Soon the clot isinvaded by osteoblasts fromthe nearby bone and from theperiosteum.

The osteoblasts lay downnew bone which fills the gapbetween the fragments andbulges out at the sides. Thisis the callus.

Over a period of manymonths the callus is absorbedby the osteoblasts, and theymake more new bone exactlylike the original one.


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early stages of bone formation are not visible radiographically

healthy person, new bone formation is visible within 4-6 wks, with the healing processcomplete in 4-6 mos for a single fracture in a large tubular bone

delay in union may be evident by a delay in the appearance of new bone, and can occurfrom a variety of causes

EVALUATION OF SKELETAL TRAUMA



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well defined lesion of mixed signal intensity occupies the regionof the iliopsoas. The Mixed signal pattern is common inhaematoma, indicating the complexity of the haematoma, andvariations in haemoglobin, deoxyhaemoglobin, methaemoglobinand haemosiderin levels

COMPLICATION OF FRACTURE most uncomplicated fractures heal readily, in

open fractures have an increased potential for infection at the fracture site and carefulscrutiny of the healing process is warranted

tibia has long been singled out as a bone liable to delayed union or non-uniono reasons

obscure, but poor vascular supply and lack of immobilisation

due to the large number of 'high-energy' Injuries seen in the tibia,particularly from pedestrian bumper' injuries, with a large amount ofresulting necrosis of soft tissue and bone at and around the fracturesite

Causes of delayed union

Mechanical poor appositionInadequate stabilization

Pathological age-decreased osteoblastic activityDietary-vitamin deficiency (C and D)Pathological fracture (underlying abnormality:infection)

Non-uniono absence of bony union over a prolonged periodo radiographic appearance is usually of a persistent fracture line, usually with

sclerotic margins, and marked surrounding sclerosiso MRI may have a role to play in the assessment of non-union with its ability to

detect infective causes

Causes of non union1. Idiopathic (particularly tibia)2. Poor stabilization3. Infection4. Pathological fracture5. Massive initial trauma

Non-union of the tibia despite interosseousbone grafting and surgical wiring. There issclerosis around the fracture line, withoutfirm evidence of bone bridging, 1 yearafter the fracture

Maluniono fracture which heals in an unsatisfactory anatomical

position, either with excessive overlap of fragments,giving rise to shortening of the bone, or unsatisfactoryangulation or displacement of the distal fragment

Malunion of the tibial fracture, which has healed well,but shows lateral angulation of the distal fragment.



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SPECIAL TYPES OF TRAUMAStress (fatigue) fractures

result from chronic repetitive forces which by themselves are insufficient to causefracture, but over the course of time lead to the classical changes of a stress fracture

occur in many bones, and usually at characteristic sites, often as the result of athleticactivity

example: `march' fracture of the second and third metatarsal head, the stress fractureof the mid and distal tibia and fibula in long-distance runners and ballet dancers, andfractures of the proximal fibula in paratroopers

earliest diagnosis can be made by nuclear medicine scanning or MRIo show increased activity before radiographic signs appear. When radiographic

signs appear, they may take several forms, depending upon the stage of

healing or the chronicity of the stresso hairlike lucency may be seen traversing the hone. New Bone formation around

the fracture may be the only radiographic sign, or may accompany thecortical fracture

Multiple stress fractures are seen, some with obvious horizontallucencies running perpendicular to the bone cortex. The Patient was a joggerwho refused to give up jogging despite the pain

TypesSpondylolysis pars interarticularis defects

underlying causeso congenital hypoplasia of the articular processeso degenerative change within the posterior joints

Mild degrees of spondylolisthesiso occur when there is loss of articular cartilage at the posterior intervertebral

joints as in degenerative disease More severe spondylolisthesis

o results from pars interarticularis defectso graded according to severity

Grade I up to 25% displacement of the vertebral body Grade II up to 50%

Grade III up to 75% Grade IV 100% displacement

Avulsion fractures



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occur from avulsion of bone fragments at the site of ligamentous or tendinousattachments throughout the skeleton

osteochondritis which represent avulsion fractures from chronic or repeated traumao Osgood-Schlatter disease

diagnosis is made clinically, although it can he suggestedradiographically when there is clear elevation of fragments of the tibial

tubercle separated from the underlying boneo Sindig-Larsen disease of the tibial tubercle and inferior patella respectively

Common avulsion injuries at the origin of muscle tendon insertions arc seen at theo inferior border of the ischium (hamstrings)o Anterior inferior iliac crest (rectus lemons)o lesser trochanter (iliopsoas)

Sites of avulsion fractures with muscle origin

Site of avulsion fracture Muscle originAnterior superior iliac crest SartoriusAnterior inferior iliac crest Rectus femorisIschial tuberosity HamstringsGreater trochanter GlutealsLesser trochanter IliopsoasPosterior calcaneus Achilles tendonOlecranon process TricepsSuperior patella QuadricepsInferior patella (Sinding-Larsen) Patella ligament

Tibial tuberosity (Osgood-Schlatter) Patella ligament

Pathological fractures

occur through bone that has been weakened by an underlying disease

occur through bone that is weakened by such conditions as osteoporosis orosteomalacia, bone tumours (whether benign or malignant) or even tumour-like lesions

of bone In elderly patients underlying malignancy should be considered, especially if the

fracture occurs in a site other than those usually seen in osteoporosis such as thefemoral neck, or in cases in which the severity of the injury is inappropriate to thefracture created

DISLOCATION

When a joint, instead of a bone, suffers a severe strain

No bones are broken, but one bone is pushed out of its proper place

Dislocated joints are very painful

Usually look deformed because the bones are in wrong positionFrom left to right, dislocation of theelbow,knee, and little finger.

RADIOLOGY FRACTURE AND DISLOCATION Page 10From left to right, dislocation of the elbow,knee, and little finger.
http://www.daviddarling.info/encyclopedia/E/elbow.htmlhttp://www.daviddarling.info/encyclopedia/E/elbow.htmlhttp://www.daviddarling.info/encyclopedia/K/knee.htmlhttp://www.daviddarling.info/encyclopedia/K/knee.htmlhttp://www.daviddarling.info/encyclopedia/F/finger_anatomy.htmlhttp://www.daviddarling.info/encyclopedia/E/elbow.htmlhttp://www.daviddarling.info/encyclopedia/K/knee.htmlhttp://www.daviddarling.info/encyclopedia/K/knee.htmlhttp://www.daviddarling.info/encyclopedia/F/finger_anatomy.htmlhttp://www.daviddarling.info/encyclopedia/K/knee.htmlhttp://www.daviddarling.info/encyclopedia/F/finger_anatomy.htmlhttp://www.daviddarling.info/encyclopedia/E/elbow.htmlhttp://www.daviddarling.info/encyclopedia/K/knee.htmlhttp://www.daviddarling.info/encyclopedia/F/finger_anatomy.htmlhttp://www.daviddarling.info/encyclopedia/E/elbow.html


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Management

Reduction of dislocationo Process of putting the bones back into their normal positions

Anethetic is given to relax the muscles


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17 Fracture and Dislocation