Tendon and Ligamentous Trauma 5

G. M. Allen, DCH, MRCP, FRCR

The Royal Orthopaedic Hospitals NS Trust, Bristol Road South, Northfi eld, Birmingham, B31 2AP, UK

Tendon and Ligamentous Trauma 5

Gina M. Allen

Box 5.1. Ultrasound

● Best spatial resolution and assessment of internal architecture

● Imaging technique of choice for superfi cial tendons and ligaments

● Dynamic examination

● Comparison with normal side

● Colour Doppler may assess neovascularity

● Calcifi cations are better seen than on MRI

5.1

Introduction

To appreciate the effects of trauma on a ligament and tendon, it is important to review the basic function and anatomy of these structures. It is also necessary to understand some of the biomechanical properties of tendons and ligaments. In this chapter, these issues will be discussed to help understand the concepts that support diagnostic imaging.

Box 5.2. MR Imaging

● Best contrast resolution

● Imaging technique of choice for deep lying tendons and intra-articular ligaments

● Fat suppressed T2-weighted imaging useful for assessment of paratenonitis

● Demonstrates intra-articular lesions and bone injury

C O N T E N T S

5.1 Introduction 61

5.2 The Microstructure 62

5.2.1 Composition of Tendons and Ligaments 62 5.2.2 Tendon Anatomy and

Imaging Correlation 62 5.2.3 Ligament Anatomy and Imaging Correlation 63

5.3 Biomechanical Properties of Ligaments and Tendons 64

5.4 Imaging of Tendon Disease 65 5.4.1 Tendon Disorders 65

5.4.1.1 Tendinosis and Insertion Tendonopathy 65 5.4.1.2 Tenosynovitis, Paratenonitis and

Tendinobursitis 65 5.4.1.3 Tendon Rupture 66

5.4.1.4 Tendon Dislocation or Subluxation 66 5.4.2 Imaging of Tendon Disease 66 5.4.2.1 Plain Radiographs 66 5.4.2.2 Computed Tomography 67 5.4.2.3 MR Imaging 67

5.4.2.4 Ultrasound 67

5.5 Imaging of Ligament Disease 69 5.5.1 Intra-Articular Ligaments 69 5.5.2 Extra-Articular Ligaments 69 5.5.2.1 Acute Ligament Injury 69 5.5.2.2 Chronic Ligament Injury 70 5.6 Conclusion 71

Things to Remember 71 References 71

5.2

The Microstructure

5.2.1

Composition of Tendons and Ligaments

The fi rst division of tendons and ligaments is the fascicle; this is then broken down systematically into progressively smaller units. The fascicle is made up of fi brils, which are the essential building blocks of tendons and ligaments. The fi bril is divided into sub-fi brils, which are composed of micro-fi brils and fi nally tropocollagen (Fig. 5.1) (Kastelic et al.

1978). The mechanical behaviour of the ligaments and tendons depends largely on collagen, as this is the principal tensile constituent. Collagen is a fi brous protein which is made up of three polypeptide chains.

These amino-acid residue chains consist of a left- handed helix named an alpha-chain. Three of these alpha-chains are then arranged in a right-handed helix (named the gamma-chain) which makes up a molecule of collagen. The collagen molecules are then arranged with overlapping regions within the microfi bril (Robinson et al. 2004).

Depending on the variation of amino-acids within the alpha-chains, the collagen is divided into different types. The principal element in adult ligaments and tendons is type 1 and this is important in providing tensile strength. Type 3 collagen is found in imma-

ture and healing ligaments. Type 3 collagen is always found in association with type 1 and the proportion of type 1 increases as ageing or healing occurs. Type 3 collagen is therefore thought to be an intermediate material. Other types of collagen are found in car- tilage and muscle and synovial membrane (Cooke 1989).

The collagen in ligaments is more elastic than in tendons, as more fl exibility is necessary for their function.

5.2.2

Tendon Anatomy and Imaging Correlation The collagen is arranged in a longitudinal orientation building up through microfi brils and subfi brils to eventually make up a fi bril. The overlap of the colla- gen fi bres is approximately one-quarter of the length of its neighbour and this is stabilised by covalent bonds forming crosslinks (Robinson et al. 2004). The fi brils are the smallest element of the tendon that can be seen by imaging. Only high resolution ultrasound is capable of visualising these elements (Figs. 5.2 and 5.3). A linear fi brillar arrangement results from the highly oriented nature of extracellular collagen in tendons (Adler 2005). This fi brillar pattern is not visible with MR imaging.

Tendons are highly refl ective because of the strong refl ection of the US beam. Because of the arrange- ment of extracellular collagen, tendon echogenicity is dependent on the angle of incidence of the US beam.

Rocking the transducer by as little as 5–10° can make the tendon appear hypoechoic, a phenomenon which is better known as anisotropy (Adler 2005).

Scarcity of mobile protons causes normal ten- dons to have a low signal intensity on all MR pulse sequences. Care must be taken to avoid misinterpret- ing all increased signal within a tendon as abnor- mal. There are two major causes for increased signal within a normal tendon. If multiple tendon slips are converging to form a single tendon, as seen in the quadriceps tendon, longitudinal striations of inter- mediate signal may be seen within the tendon sub- stance (Zeiss et al. 1992). Tendon alignment relative to the magnetic fi eld can also result in increased signal intensity caused by the so-called “magic angle phenomenon” (Erickson et al. 1991).

The fi brils of tendons range in diameter depend- ing on their maturity. In immature tissues they are smaller. The fi brils then make up the fascicles by mingling between fi broblast and ground substance.

Fig. 5.1. Line diagram of the hierarchical structure of tendons and ligaments

←

←

←

←

←

←

Again they are arranged in a parallel longitudinal position. The fascicles are then enclosed within a reticular membrane that separates them from the surrounding tissue.

Tendons attach a muscle to bone and often cross joints. Some tendons are therefore named con- tentiously, for example the patellar tendon which joins the patella to the tibial tuberosity (Webb and Bulstrode 2004).

There are two types of tendon. Those that have a synovial sheath which provides a cover to reduce friction as they cross joints, bone or where they

pass through fi bro-osseous tunnels. These have a covering of connective tissue that is the visceral synovium and are joined to a second cover, the pari- etal synovium by a mesotenon. There is a thin layer of fl uid, the synovial fl uid, that lies between these layers and this reduces friction. The neurovascular supply of the tendon enters via the mesotenon. Some tendons need to be kept close to bone as they cross joints for example the fi nger fl exor tendons are held down by pulleys. The osseous tunnels are formed by fi brous bands crossing the roof such as the carpal tunnel (Fig. 5.2).

The other types are tendons without a synovial sheath. In these tendons the epitendineum, a dense connective tissue layer is tightly bound to the tendon.

On ultrasound images, the epitendineum is seen as a refl ective line surrounding the tendon (Fornage 1986). Connective tissue fi bres permeate the fascicles, causing the epitendineum to adhere to the tendon.

Blood vessels and nerves enter the tendon along these fi bres. Loose connective tissue, the paratenon, envelops the epitendineum (Van Holsbeeck and Introcaso 2001).

This again is broadly formed of two layers that are loosely held together (Valle et al. 2005). The Achilles tendon is an example of such a tendon (Fig. 5.3).

At the insertion of the tendon to bone, a narrow band of avascular fi brocartilage is present. This part of the tendon is hypoechoic on ultrasound exami- nation. This effect may be the result of the cartilage in its substance or the anisotropic characteristics of the curved fi bres in the tendinous attachment (Van Holsbeeck and Introcaso 2001). On MRI, similar increased intratendinous signal intensity on proton density MR images has been described. This may be related either to intratendinous fi brocartilage and/or magic angle phenomenon seen in the curved fi bres (Defaut et al. 2003).

5.2.3

Ligament Anatomy and Imaging Correlation Ligaments join bones together.

Ligaments are composed of dense, regular connec- tive tissue similar to that of tendons. Their structure differs from that of tendons in that there is more interweaving of collagen fi bres giving them a less regular histological and sonographic appearance (Bloom and Fawcett 1980).

Ultrasound and MRI are the only diagnostic methods suited for examination of ligaments. CT has

Fig. 5.2. Normal fl exor tendon shown on ultrasound. This shows the fi brillary structure of the fl exor tendon at the meta- carpal-phalangeal joint and the A1 pulley attaching the tendon to bone

Fig. 5.3. Normal Achilles tendon. This ultrasound shows the normal Achilles tendon at its attachment into the calcaneum.

Incidental note is made of a low lying insertion of the soleus muscle in this ballet dancer – an accessory soleus

A1 Pulley

insuffi cient contrast resolution to defi ne ligaments (Van Holsbeeck and Introcaso 2001).

The advantages of ultrasound examination over MRI are its excellent near fi eld resolution, the short examination time, the ability to perform a dynamic examination and the ease of comparison with the normal side.

Although ultrasound examination is a valuable technique for the study of extra-articular ligaments, it is of little use in the assessment of intra-articular ligaments, such as the cruciate ligaments of the knee.

MRI is the preferred method for the study of intra- articular ligaments (see Chap. 17).

Using MR imaging, normal ligaments have a variable appearance dependent on their location.

Although most ligaments are hypointense on all pulse sequences, some may show a mixed signal intensity due to the presence of internal fi bro-fatty tissue (e.g. the deep layer of the deltoid ligament and the anterior cruciate ligament). MR is technically more demanding as ligaments may be small and scan planes have to be exact. This means that it is diffi cult to orientate an MR section along the course of a specifi c ligament. If the sections cross the liga- ment it may erroneously cause it to appear absent or defi cient. The slice thickness must be small to avoid volume averaging artefacts and to study these thin structures. Poor examination technique commonly leads to errors on the part of the inexperienced interpreter. Detailed discussion of this variability is beyond the scope of this chapter (see specifi c topo- graphic chapters in this book).

Using ultrasound ligaments appear as refl ective bands joining bone surfaces. They vary in size; the anterior tibiofi bular ligament is one to two millime- tres thick whilst the calcaneofi bular ligament is much more substantial being up to 5 mm in depth. The alignments of ligaments vary considerable between individuals. When using ultrasound it is easier for the examiner to rotate the probe to align with the expected course of the ligament as this plane can be adjusted to fi t the subtle normal variations in bone shape.

Absence or defi ciency of a ligament, especially the thinner ones, is more reliably determined using ultrasound.

5.3

Biomechanical Properties of Ligaments and Tendons

Longitudinal forces applied across the ligament and tendon lead to a non-linear load extension curve.

As the load is increased the ligament stiffens and this continues until subsequent rupture. The shape of the load extension curve changes, however, with external factors such as orientation of the load and temperature and the rate at which the load is applied.

Once a load exceeds a certain point, the ligament or tendon becomes permanently deformed and this is when a failure occurs (Kastelic and Baer 1980;

Towers et al. 2003). Repeated loading on a cyclical basis can train the ligament and tendon to take on more load, this is shown in vitro as a pre-condition- ing of the tendon and ligament, but in vivo shows the importance of an athlete warming up prior to an event (Kannus et al. 1997) (Fig. 5.4).

Fig. 5.4. The characteristic load/deformation plot for collag- enous tissues. Initially a small load produces a relatively large extension of the collagen (region 1). As the load is increased, the ligament or tendon stiffens (region 2) until a constant linear relationship is reached (region 3) This continues until yield and subsequent rupture occurs

Ligaments and tendons rupture at the weakest point. The most vulnerable location depends on the age of the patient (Fig. 5.5).

For example in the adult the musculotendinous junction is weakest point (O’Connor and Groves 2005).

In the child, the bone is the most vulnerable and therefore tendon injuries are extremely uncommon.

In the adolescent, injuries to muscle often occur at the site of the apophysis so that bone avulsion

injuries are the most common in this age group (see Chap. 26).

As for tendons, ligaments are stronger than the metaphyseal growth plate in youth, and therefore trauma to children’s joints often results in injury to the growth plate (see Chap. 26) (Salter-Harris epiph- yseal fractures). In the adult athlete, the ligaments are more vulnerable than the adjacent bone.

5.4

Imaging of Tendon Disease

5.4.1

Tendon Disorders

The tendon and adjacent structures can react in a number of ways to (repetitive) trauma.

5.4.1.1

Tendinosis and Insertion Tendonopathy

Repetitive injury and a high level of athletic activity leads to degeneration or tendinosis of the tendon (Wang et al. 2006). Loss of cross-linking between collagen fi bres, edema, myxoid degeneration, vascu- lar proliferation (angiofi broblastic hyperplasia) and reparative phenomena (collagenous type 3 matrix production) are seen on histologic examination. Neo- vascularity is a specifi c sign of disease and attempted repair. There is associated ingrowth of nerve endings that explains the increased pain in most of these patients. Rarely calcium deposits may occur within the tendons as a result of hypoxia. These histological changes will result in changes in morphology and internal architecture on imaging. They will be exhib- ited as swelling due to edema and matrix production (hypoechogenicity on US examination, raised signal

intensity on T2-weighted MR studies), loss of fi brillar structure and calcium deposits.

Insertion tendonopathy occurs commonly in ath- letes. It is limited to the fi bro-cartilaginous insertion of the tendon to bone. Differentiation from tendi- nosis is very important because there is no indica- tion for surgery for insertion tendonopathy (Van Holsbeeck and Introcaso 2001).

5.4.1.2

Tenosynovitis, Paratenonitis and Tendinobursitis The involvement of structures surrounding the tendon can result in different disease entities, depen- dent on the affected region.

In tendon with a synovial sheath, fl uid may sur- round the tendon. Tenosynovitis (or tenovaginitis) is swelling and abnormality of the synovium within the tendon sheath, which is often associated with increased fl uid in that sheath. In acute tenosynovitis, the tendon itself is of normal thickness, whereas in subacute tenosynovitis, the tendon may be thickened.

In chronic forms, there is frequently no increase in synovial fl uid and comparison with the normal side is required to make the diagnosis.

In tendons without a synovial sheath, the epiten- dineum and surrounding paratenon can be involved resulting in a paratenonitis. Edema and swelling is present in the paratenon surrounding the tendon.

This is seen as a hypoechoic appearance on ultra- sound and high signal on T2-weighted MR imaging.

It is a much more conspicuous sign on fat suppressed T2-weighted MRI than when seen as hypoecho- genicity using ultrasound (Fig. 5.6). The tendon itself is not always affected. The involvement of one of the peritendinous bursae may be described as tendino- bursitis (Fig. 5.6).

Acute tenovaginitis or paratenonitis often precede tendinous lesions. They are associated with infl am- matory infi ltration and can be treated with antifl o-

Bone

Apophysis

Musculotendinous junction

Muscle Young child Adolesent

Tendon

Adult Elderly Fig. 5.5. Muscle–tendon–apophy- sis–bone (diagram). This depicts the area of weakness in the tendon–bone chain according to the age of the patient

gistic therapy (NSAID or corticosteroids). In contra- distinction, infl ammation is not found in tendinosis;

the tendon itself will not benefi t from antifl ogistic therapy.

5.4.1.3

Tendon Rupture

A sudden explosive force can lead to rupture of the tendon – whether partial or complete. Tears are more common in older patients as the tendon is less fl exible and has a poorer blood supply. In addition pre-exist- ing tendinosis may result in internal splits and tears, which may predispose to complete rupture.

5.4.1.4

Tendon Dislocation or Subluxation

Displacement of tendons from their proper location may occur in athletes, often as a result of chronic trauma. Dislocation of the peroneal tendons may be seen in American footballers, soccer players and gymnasts (Van Holsbeeck and Introcaso 2001).

Dislocation of the long head of the biceps tendon may be combined with tears of the rotator cuff that involve the subscapularis tendon.

Grading of tendon injury has little value. It is very dependent on the method of imaging employed and bears little relationship to the symptoms that will result. The primary role of imaging is to locate the problem and to determine if the tendon is abnor- mal. It is of less use in defi ning the severity of the problem.

5.4.2

Imaging of Tendon Disease

5.4.2.1

Plain Radiographs

Radiographs will not show tendon damage unless there is a massive loss of the normal tissue planes as is seen in some cases of rupture of the quadriceps tendon. Radiographs may, more importantly, show an associated fracture at the tendon insertion. For example, avulsion on the dorsum and at the base of the distal phalanx in an extensor tendon rupture of the hand (mallet fi nger) (Fig. 5.7). Occasionally calcifi cation in a tendon may be observed. Unfor-

Fig. 5.6. Achilles tendinobursitis and paratenonitis. Sagittal fat suppressed T2-weighted MR image. The distal Achilles tendon is enlarged, with internal linear areas of intermediate signal.

Note associated deep retrocalcaneal bursitis and paratenonitis

Fig. 5.7a,b. Avulsion of fl exor digitorum profundus while play- ing volleyball. a Plain radiograph showing an avulsion fracture from the base of the distal phalanx that has moved proximally up the fi nger (arrows). b Ultrasound showing the same avul- sion fracture and the attached fl exor tendon (oval) that has been pulled proximally with the fracture fragment

b a

tunately plain radiographs are not very sensitive because many tendons are injured without any bony injury.

5.4.2.2

Computed Tomography

CT is useful if there has been bony trauma. It may be particularly helpful for detection and assessment of subtle fractures, which are not seen on plain fi lms.

Before the advent of MRI, CT arthrography was used to image tendons indirectly. It can still be useful in patients who are unable to tolerate an MR scan or have cardiac pacemakers.

5.4.2.3 MR Imaging

MR imaging has become the main imaging tech- nique for assessing both soft tissue and bones in one examination. Twenty percent of the population are claustrophobic and therefore in these patients MRI is a frightening experience. The introduction of more open MR scanners may help although some will remain intolerant to the method.

MRI can identify fl uid in the tendon sheath and can start to appreciate internal change within a tendon (Figs. 5.6 and 5.8). Fat suppressed T2-weighted images are very effective in demonstrating parate- nonitis (Fig. 5.6). MRI cannot identify the distinction between synovitis and fl uid within a tendon sheath without the use of intravenous contrast. Whilst MRI contrast agents are fairly safe they still carry a very small risk of adverse reaction including death.

The microfracturing that often accompanies tendon injuries can be detected by MRI which is much more common than the fractures seen on CT

or plain fi lms. Certain patterns of microfracturing help the clinician to assess the mechanism of injury and increase awareness of accompanying injuries to soft tissue (see Chap. 6).

MRI is unfortunately not currently a dynamic method of imaging and therefore in chronic injury abnormalities may be missed. Although MRI will usually demonstrate full thickness tears with retrac- tion, partial tears or tears without retraction may be very diffi cult to detect. Finding calcifi cation within an injured tendon can be diffi cult as can fi brosis and scarring when using MRI alone (Adler and Finzel 2005).

5.4.2.4 Ultrasound

Ultrasound is the microscope of tendon and ligament disease. With the latest high resolution of ultrasound machines the fi brils can be visualised and more subtle abnormalities appreciated (Fig. 5.9). The intrinsic line pair resolution of US well exceeds that of com- mercially available MR systems and the detail seen within tendons is much greater using US. The infl ux of neovascularisation (angiofi brous hyperplasia) can also be appreciated by using Colour or Power Doppler without the need for contrast injections (Fig. 5.10).

This can help detect subtle injuries.

If the patient has pain at a particular site that coin- cides with new vessels, this will confi rm the origin of the symptoms. This can be useful in assessing response to treatment, when the vessels are shown to decrease in number at follow up examinations (Ohberg and Alfredson 2002).

The examination can be directed at the site of the sportsman’s painful area. Ultrasound is extremely useful when the patient can point to an area of pain.

Fig. 5.8. Flexor tendinosis in a rower.

Axial SE T1-weighted MR image show- ing thickening and signal changes within the fl exor tendon of the fourth fi nger (arrow)

If the area is extensive and ill defi ned then MR may be a better way to image in the fi rst instance.

Fluid and synovitis in tendon sheaths can be iden- tifi ed as separate entities without the need for con- trast injections. Ultrasound is an excellent means of differentiating fl uid from solid matter.

US can detect small areas of calcifi cation and scar tissue. Dynamic movement can assess the full extent of tendon rupture. Moving the tendon actively (muscle contraction) or passively (the operator moves the limb) may give different information as these actions apply force to different ends of the tendon. Stressing the tendon can make a tear more obvious and allow assessment of a gap in the tendon (Fig. 5.11). This separation can be measured assisting the surgeon in planning their repair. Movement will differentiate between full and partial thickness tears. Partial tears

may open under load when they are diffi cult to iden- tify on static imaging but they will not separate or show paradoxical movement of the tendon ends.

Ultrasound is becoming easier for the clinician to interpret since the advent of extended fi eld of view images. These can demonstrate a whole limb to the surgeon who needs to know the site of rupture of a tendon. Electronic recording and display provides a composite image of an area many times the width of the ultrasound probe so that the full length of a tendon and its muscle can be visualised on one image (Fig. 5.12).

Dynamic examination with stress manoeuvres is mandatory to assess tendon dislocation or sublux- ation (e.g. dorsifl exion and eversion stress for evalu- ation of peroneal tendon subluxation)

Fig. 5.9. Proximal patellar tendinosis in an elite goalkeeper.

Longitudinal ultrasound. There is thickening, loss of fi bril- lar structure and hypoechogenicity at the proximal patellar tendon affecting the central patellar tendon most marked posteriorly

Fig. 5.10. Proximal patellar tendinosis in an elite goalkeeper.

Colour Doppler shows marked neovascularity in the proximal patellar tendon

Fig. 5.11. Full thickness tear of the supraspinatus tendon in a weekend tennis player. Longitudinal ultrasound shows a fl uid fi lled gap within the supraspinatus tendon

Fig. 5.12. Complete Achilles rupture in non-professional foot- baller. Extended fi eld of view ultrasound image showing a tendon gap within the Achilles tendon

5.5

Imaging of Ligament Disease

5.5.1

Intra-Articular Ligaments

Although some investigators have been successful in demonstrating tears of intra-articular ligaments of the knee and the wrist, the examination for injuries to intra-articular ligaments is best performed using MRI (Van Holsbeeck and Introcaso 2001).

5.5.2

Extra-Articular Ligaments

Ultrasound provides a reliable means of assessing acute ligament injury, in cases when clinical exami- nation is made difficult by pain and swelling (Van Holsbeeck and Introcaso 2001). Some argue that ultrasound is only required in a limited number of athletes with equivocal clinical findings, especially when surgery is being considered (Van Dijk et al.

1996). Others would hold that prognosis and reas- surance are important factors in management and a test that is non-invasive and safe like ultrasound examination has a useful supportive role.

5.5.2.1

Acute Ligament Injury

Ligaments respond to injury by either complete rup- ture or partial rupture (spraining).

In case of partial rupture, the involved area of the ligament appears markedly thickened and decreased in echogenicity on ultrasound examination. Com- plete ruptures are demonstrated as a discontinuity of the ligament and the free ends may be separated by a haematoma. The fl uid occupying the gap will appear hyperechoic or of reduced echogenicity, depending on how long after the injury imaging is performed. The diagnosis tends to be made most easily when imaging occurs as soon after injury as possible although in the fi rst few minutes the appear- ances may be confusing. Some retraction of the ends of ligament may result in a slightly rounded appear- ance (Van Holsbeeck and Introcaso 2001). Avul- sion fractures at the insertion of the ligaments may be detected using ultrasound (Fig. 5.13) and may not all be seen by standard radiography.

Ultrasound is particularly valuable for assessment of stability of a joint, because dynamic examination can be performed, putting stress on the ligament and opening the bone gap.

MR imaging is rarely performed for assessment of acute ligament disorders. It can however detect associated microfracturing (bone bruise, see Chap. 6) (Figs. 5.14 and 5.15). The main indication for MR imaging is to detect associated intra-articular abnor- mality, such as meniscal lesions or injuries of intra- articular ligaments. For simple medial collateral liga- ment lesions of the knee, a three-grade MR staging system has been developed which correlates well with clinical staging (see Chap. 17).

Fig. 5.13a,b. Avulsion fracture at the distal insertion of the anterior talofi bular ligament. a Ultrasound. The avulsed frag- ment is seen as a linear refl ection, representing cortical bone from the talus. b The corresponding plain radiograph con- fi rms the avulsion fracture

a

b

5.5.2.2

Chronic Ligament Injury

With suitable treatment, partial ruptures heal com- pletely within two months, whilst complete ruptures can take six months to recover.

Inappropriate or delayed treatment may result in ligamentous non union. Persisting ligament interrup- tion occurs in a minority of patients (10%), and this can be demonstrated using both US or MR imaging as a residual gap or focal thinning of the ligament.

Hypertrophic non-union is a more frequent com- plication of untreated partial ligament ruptures that result in excessive formation of granulation tissue and mucoid degeneration.

Clinically, pain and tenderness is present over the lesion. This type of non-union may be seen at differ- ent locations, including the ankle ligaments, sinus tarsi, coracoacromial ligament (common in impinge- ment syndrome in tennis players), plantar fascia (long distance runners) and the medial collateral ligament of the knee (soccer, football, basketball, hockey...). It is characterised by thickening seen both on ultra- sound and MRI examination. Ultrasound may dem- onstrate few internal refl ections within a hypoechoic mass. In repair stages granulation tissue and reactive synovitis may lead to new blood vessels which can be identifi ed using power Doppler imaging. Internal calcifi cations may be observed (Van Holsbeeck and Introcaso 2001).

As with tendon disease, ultrasound will show cal- cifi cation better than MRI (Fig. 5.16).

Pelligrini-Stieda disease is perhaps part of the spectrum of hypertrophic non-union of the MCL of the knee although the location of the calcifi cation is

Fig. 5.15. Ligament rupture on MRI: ankle ligaments. Axial oblique fat suppressed FSE T2 weighted MR image. Note a rupture of the anterior talofi bular ligament in an elite athlete with microfracturing of the postero-medial talus

Fig. 5.14a,b. Ligament rupture on MRI: knee ligaments. a Sagittal fat suppressed proton density MR image. Note ruptures of the ACL and PCL with microfracturing. b Coronal fat suppressed proton density MR image. Note rupture of the LCL with a fracture of the proximal fi bula

a b

sometimes more proximal and may refl ect associated damage to the distal adductor muscles.

5.6

Conclusion

Ligaments and tendons are complex collagenous soft tissue elements that respond to injury in a number of ways according to the age group of the patient and the mechanism of injury.

They can be imaged in a number of ways but MRI and ultrasound are the most informative techniques for assessing these structures.

References

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Cooke P (1989) The effects of mechanical characteristics of ligaments upon joint function and degeneration. Bristol, p 20

Delfaut EM, Demondion X, Bieganski A et al. (2003) The fi bro- cartilaginous sesamoid: a cause of size and signal varia- tion in the normal distal posterior tibial tendon. Eur Radiol 13:2642–2649

Erickson SJ, Cox IH, Hyde JS et al. (1991) Effect of tendon ori- entation on MR imaging signal intensity: a manifestation of the «magic angle» phenomenon. Radiology 181:389 Fornage B (1986) Achilles tendon: US examination. Radiology

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Kannus P, Jozsa L, Natri A et al. (1997) Effects of training, immobilization and remobilization on tendons. Scand J Med Sci Sports 7:67–71

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dons and ligaments. Springer, Berlin Heidelberg New York Van Dijk CN, Moll BW, Lim LS (1996) Diagnosis of ligament

rupture of the ankle joint. Physical examination, arthrog- raphy, stress radiography and sonography compared in 16 patients after inversion trauma. Acta Orthop Scand 67:566–570

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Fig. 5.16. Ligament rupture on ultrasound: ankle ligaments.

Ultrasound shows calcifi cation (arrow) at the site of a previ- ously ruptured anterior talofi bular ligament in an elite athlete

Things to Remember

1. Tendons respond to injury in a number of ways, dependent on the patients‘ age.

2. Ultrasound is the best way of imaging super- fi cial tendons and ligaments as it best demon- strates their microstructure.

3. MR Imaging is the preferred method of assess- ing associated injuries, especially those in bone. It can also assess ligament and tendon damage. This combination is especially useful in the knee.

4. Imaging is an important adjunct to the clini- cian who should fi rst take a good history and perform a clinical examination. The imaging fi ndings must fi t the clinical picture, other- wise further investigation is mandatory.