M. Maas, MD, PhD M. de Jonge, MD
Department of Radiology, Academic Medical Center, PO Box 22660, Suite C1-210, 1105 AZ Amsterdam, The Netherlands R. A. W. Verhagen, MD, PhD
Ziekenhuis Hilversum, Department of Orthopedics Surgery
& Traumatology, P.O. Box 10016, 1201 DA Hilversum, The Netherlands
Ankle and Foot: 20
Osteochondral Injuries
Mario Maas, Milko C. de Jonge, and Ronald A. W. Verhagen
Box 20.1. Standard radiography
● Used for initial survey and to defi ne additional pathology
● AP view helpful, lateral not in detecting OCL
● When negative, OCL is not ruled out
● Additional AP view with 4 cm heelrise may be benefi cial
Box 20.2. MRI
● Very powerful in detecting OCL
● Bone marrow edema detection is important, yet hampering adequate true lesion demarcation
● All three imaging planes must be used to rule out or to detect concomitant lesions
Box 20.3. MDCT
● Axial high resolution (0.5/0.6 mm) acquisition with coronal and sagittal MPR
● Is as powerful as MRI in the diagnostic workup of a patient with chronic ankle pain
● Enables exact delineation of the OCL
● Provides surgeon with adequate information on location and especially the extent of the OCL
20.1 The Ankle
20.1.1
Osteochondral Injuries
20.1.1.1
Introduction: Specifi c Anatomy and Incidence
The anatomy of the ankle will not be described in detail. In order to understand better the occurrence and location of osteochondral injuries of the ankle we thought it would be wise to discuss the cartilagi- nous anatomy briefl y.
C O N T E N T S
20.1 The Ankle 337
20.1.1 Osteochondral Injuries 337 20.1.1.1 Introduction: Specifi c Anatomy and
Incidence 337
20.1.1.2 Bone Bruise 338
20.1.1.3 Osteochondral Lesion (OCL) 339 20.1.2 Osseous Injury 345
20.1.2.1 Snowboarder’s Fracture 346
20.2 The Foot 347
20.2.1 Osteochondral Injury 347
20.2.2 Sports Specifi c Acute Foot Injury 347 20.2.2.1 Turf Toe 347
20.2.2.2 Skimboarder’s Toe 347 20.2.3 Overuse Injury of the Foot 347 20.2.3.1 Navicular Stress Fracture 347 20.2.3.2 Sesamoid Overuse Injury 347
Things to Remember 348 References 348
Since the sports related biomechanics of osteo- chondral injuries of the ankle is closely related to the sports in which ligamentous ankle injuries and ankle sprains occur, the reader is advised to read the chap- ter by D. Wilson (Chap. 19).
20.1.1.1.1
Cartilage Anatomy
Osteochondral injuries in the ankle most often occur in the tibiotalar joint most frequently in the talar dome. It is interesting to know that the talus is cov- ered with cartilage not only on top of the talar dome, but also on the medial and lateral facets facing the medial malleolus and the fi bula. In a recent cadaver study Sugimoto et al. (2005) examined the thick- ness of the cartilage at the talar surface. Specifi c interest was paid to those regions where osteochon- dral injuries predominantly occur (Sugimoto et al.
2005). In 29 cadaver ankles (22 male) a coronal pie- wedge shaped section of the mid talar dome was obtained, with 2 mm width and 5 mm depth. With the use of radiographs (high resonance X-ray ana- lyzer) measurements were obtained at nine areas in each specimen. The average cartilage thickness of the total area was 1.35 mm (±0.22) in males and 1.11 mm (±0.28) in females. The difference was con- sidered statistically signifi cant between the sexes (p=0.025). The mean thickest area was found in the medial talar corner (1.56 mm in males, 1.42 mm in females). The thinnest cartilage was found in the lateral fi bular surface (1.00 mm in males, 0.86 mm in females). The fact that only a small sample was measured, a great variation between the samples was found and only one cross section was measured, are study limitations. Compared to the knee, where the cartilage is much thicker, the cartilage in the ankle is thin. This is thought to be due to the fact that the ankle joint is a congruent joint, compared to the knee.
20.1.1.1.2 Incidence
Osteochondral injuries very often are described as sequellae of inversion sprains. Inversion sprains of the ankle are common injuries at all levels of sports worldwide. Approximately 25% of the sprains occur in soccer, 40% in basketball and 23% in athletics (Bergfeld 2005). In 2002, in the Netherlands, 78,000 patients presented at hospital emergency departments with ankle injuries, 59% of which were treated for
an inversion sprain (Consumer Safety Institute 2004). In more than 40% of cases the injuries were sports-related. Although most patients go on to an uncomplicated recovery, those who continue to have pain in the ankle and hind-foot can present as a diag- nostic problem. The athletes present themselves with chronic ankle pain (Verhagen et al. 1995).
20.1.1.2 Bone Bruise
With the introduction of fat suppressed MR imag- ing the radiological diagnosis of a bone bruise is introduced in the fi eld of sports medicine. A bone bruise (bone contusion) usually happens during an inversion injury of the ankle. The impaction and rotation forces that occur cause microfractures in the trabecular bone, hyperemia and hemorrhage ( Sijbrandij et al. 2002; Rosenberg et al. 2000).
While standard radiography will not detect these lesions, the MRI image consists of ill-defi ned retic- ular areas of low signal on T1-weighted and high signal on fat suppressed (TSTIR, fat sat T2-weighted) sequences. There usually is a broad based contact with the articular surface, with an intact cortical surface. On Multi Detector Computed Tomography (MDCT) this might show as areas of increased scle- rosis, also broad based with the articular surface.
The clinical manifestation of these lesions is often non-specifi c and the clinical signifi cance in the ankle is yet unknown; the clinical consequences of bone bruise around the knee is recently reported (Vincken et al. 2006). The clinical history is essential, because when bone marrow edema is an isolated fi nding it can be caused by various pathologies such as ischemia, (migrating) osteoporosis, infection or high level of mechanical stress. It is known that in high performing athletes this edema without clinical signifi cance is a frequent encountered phenomenon and should be interpreted with clinical correlation.
The appearance of bone bruise on MRI can persist for quite some time. Although there is literature stat- ing that it will persist for 6–12 weeks, in the authors experience in high performing athletes it will persist even longer, since athletes will not stay inactive when there is no physical limitation (Horton and Timins 1997; Morrison 2003).
It is debatable whether bone bruise is a precursor
of the development of a talar osteochondral defect
(Martinek et al. 1998). It has however become
increasingly known that repetitive stress can also be
causing and maintain the presence of these lesions
and when continued may lead to the development of a complete osteochondral lesion (Rosenberg et al. 2000). The location of bone bruises at sides where osteochondral talar lesion most frequently occur supports this theory. Reporting such a bone bruise as a precursor of a talar osteochondral lesion by the radiologist may be benefi cially for patient manage- ment and is therefore advised.
20.1.1.3
Osteochondral Lesion (OCL)
20.1.1.3.1
Background, Defi nition and Etiology
In 1738 the famous anatomist Alexander Monro I was the fi rst to describe the presence of cartilaginous bodies in the joint in his Medical Essays and Obser- vations, six volumes (1732–1744) (Monro 1738).
König described free bodies in the joint and coined the term osteochondritis dissecans in 1888, and Kappis was the fi rst to describe the osteochondral lesion of the talus in 1922 (König 1888; Kappis 1922;
Bohndorf 1998; Linz et al. 2001). A lot of aliases appeared in the literature, (such as osteochondral fracture, talar dome fracture and fl ake fracture) of which osteochondritis dissecans (OCD) probably is the most common designation (Barnes and Ferkel 2003; Stroud and Marks 2000; Linz et al. 2001;
Bohndorf 1998). The accepted term to use nowa- days is the osteochondral lesion of the talus (OCL), which is defi ned as the separation of a fragment of articular cartilage, with or without subchondral bone (Bohndorf 1998; Berndt and Harty 1959;
Alexander and Lichtman 1980).
The incidence of an OCL after an ankle sprain is probably underestimated because these lesions often remain undetected, not clinically signifi - cant or are misdiagnosed as other ankle pathology (Barnes and Ferkel 2003; Benthien et al. 2002).
The incidence has been reported to be as high as 6.5% after ankle sprains (Flick and Gould 1985;
Verhagen et al. 1995; Benthien et al. 2002). Con- comitant pathology in the ankle frequently occurs, with anterior impingement, synovitis and adhe- sive capsulitis being the most frequent pathology ( Benthien et al. 2002). Bilateral lesions occur in 10–25% of cases, suggesting underlying patient susceptibility: etiology is thought to be ossifi cation defects, vascular anomalies and endocrine abnor- malities ( Verhagen et al. 2003; Bohndorf 1998;
Benthien et al. 2002).
An OCL is usually located in the anterolateral or posteromedial aspect of the talar dome. In a recent meta-analysis of over 600 lesions, it was demonstrated that 56% were located medially and 44% located laterally (Tol et al. 2000). Histologically the medial and lateral lesions are identical, but morphologically they differ. The lateral lesions are shallow and more wafer shaped, indicating a shear mechanism of injury (Stroud and Marks 2000; Canale and Belding 1980; Berndt and Harty 1959). The experiments of Berndt and Harty showed a forcible inversion and dorsifl exion with impaction of the talus to the fi bula to be the cause of this lesion (Berndt and Harty 1959; Linz et al. 2001). It is thought that all lateral lesions are of a posttraumatic nature (Benthien et al. 2002; Flick and Gould 1985; Tol et al. 2000;
Stone 1996).
In contrast, medial lesions are located over the posteromedial surface of the talar dome. They gen- erally are deep, cup shaped, and located posterior, indicating a mechanism of torsion impact (Davis and Alexander 1990; Berndt and Harty 1959).
Literature reports only 60% of medial lesions to be posttraumatic from origin (Flick and Gould 1985;
Tol et al. 2000; Benthien et al. 2002).
Although initial symptoms may be absent, in chronic cases most patients present with intermittent pain located deep in the ankle joint which increases on weight bearing. On physical examination signs are often lacking. A discrete limitation of range of motion with some synovitis may be present. Local tenderness on palpation with recognition is absent in most cases.
Since the OCL is described as an associated injury in patients with chronic lateral ankle instability, a high index of suspicion in this latter patient group may help in detecting the OCL as cause of ankle pain (DiGiovanni et al. 2000).
Since there are no specifi c pathognomonic signs
or symptoms, it is of key importance that the exam-
ining physician and radiologist are aware of the fact
that an osteochondral lesion could be present: his-
tory of fl exion inversion injury, exercise related deep
ankle pain, sensations of clicking and catching and
persistent swelling will raise the suspicion-index
(Thompson and Loomer 1984).
20.1.1.3.2
Diagnostic Imaging
Standard Radiography
Standard antero-posterior radiography of the ankle, which is weight-bearing mortise an AP view (20q of endorotation), enables clear delineation of the tib- iotalar joint, including a good view of the medial and lateral facets. The talar dome is clearly defi ned (Fig. 20.1). The weight-bearing lateral view is very useful for detecting accompanying pathology (bony impingement, loose fragment, os trigonum) but will not aid in detecting an OCL. It should be noted that with a normal mortise AP view an OCL is not excluded (Fig. 20.2).
Additional Views
Additional views of value can be AP mortise in plan- tar fl exion. The weight-bearing plantar fl exion view is easily accomplished with 4 cm heel rise, which enables a better delineation of the posterior aspect of the talus. Thus the posteromedial located OCL might be better visible (Fig. 20.3).
Although in our experience the adding of this view is benefi cial in selected cases, as is shown in Figs. 20.3 and 20.4, a recently performed study could not con- fi rm the potential value of heelrise views in a studied
population of patients with chronic ankle pain (Ver- hagen et al. 2005). The true extent of the lesion is the most important information necessary for surgical planning. This information will not be provided with the heel rise view.
Fig. 20.1. Osteochondral lesion (OCL) AP radiograph. Stan- dard radiograph weight-bearing Mortise view. OCL is sug- gested at the medial talar dome (arrow)
Fig. 20.2a,b. Cystic OCL, with a negative standard radiogra- phy and positive coronal MPR of MDCT. AP Mortise view (a) and MDCT with coronal MPR (b). No abnormalities are seen on the AP standard radiography. On MDCT the cystic OCL is clearly seen as a hypodense lesion surrounded by sclerosis
b a
MRI
MRI enables cartilage imaging as well as surrounding bone and soft tissue. When imaging the ankle atten- tion should be focused on coil choice and slice thick- ness. In the authors opinion it is advisable to image
only one ankle using a surface coil. Slice thickness can be three-four mm in three anatomical planes;
angulation is not necessary. For detecting an OCL, the MRI protocol is tailored to detect bone marrow edema, cartilage defects and effusion of the joint.
However since concomitant ankle pathology fre- quently is present, this should be taken into account in defi ning the defi nite MRI protocol in patients with chronic ankle pain. In our opinion all three anatomi- cal imaging planes are helpful. Sagittal TSTIR and T1-weighted, axial FSE short TE (PD or T1-weighted), coronal fat suppressed T2-weighted and a 3D Gra- dient T2* sequences with isotropic voxels enabling MPR would be suffi cient (Morrison 2003). Cartilage lesions nowadays may be best evaluated using high- resolution FSE intermediate sequences with long echo trains and adding fat saturation (Manaster et al. 2005). The normal cartilage will appear interme- diate, whereas a defect will show a heterogeneous or high signal intensity.
Hallmarks for detection of an OCL are edema (high signal intensity) on fat suppressed T2-weighted MR images or TSTIR, low signal on short TE MR images and a high signal intensity within the intermediate cartilage as sign of a defect (Fig. 20.4).
Although the detection of bone marrow edema is a very powerful feature of MR imaging, it also can have its disadvantage. From a surgical point of view it can obscure the true extent of the lesion, making the OCL
Fig. 20.3. Value of heelrise view: AP 4 cm mortise heelrise view.
The same patient as in Fig. 20.1, in which heelrise view tangen- tiates the posterior medially located OCL (arrow)
Fig. 20.4a–c. OCL appearance on various MR sequences. Sagittal TSTIR (a), sagittal T1-weighted SE (b), sagittal Dess 3D (c). On TSTIR the edema surrounding the cystic lesions is seen (arrow). The true extent of the lesion is not clearly delineated. On the T1 weighted MR image a clearly defi ned hypointense region is seen, without differentiation between cysts and edema (arrow).
On the Dess 3D sequence the cystic changes within the lesion are hyperintense, whereas the sclerosis is hypointense (arrow)
b c
a
larger in size than truly is the case. This is unhelpful since the planning of the surgical procedure will be hampered. Questions that the surgeon will have and that imaging needs to answer are: “Can this lesion be operated through anterior ankle arthroscopy?”,
“is a posterior arthroscopy preferable?” or “should a medial malleolus osteotomy be performed?” or “is an arthrotomy indicated?” or “is the subtalar joint involved?”. In our daily practice, working in a ter- tiary referral center for ankle pathology, the use of multidetector helical CT (MDCT) with Multi Planar Reformatting (MPR) is of great value in answering these questions (Fig. 20.5).
Multi Detector Computed Tomography (MDCT) CT scanning is described as a successful tool, superior to standard radiography in detecting OCLs. Further- more, it is known to describe the true extent and heal- ing of fragments (Zinman et al. 1988; Stone 1996).
The introduction of multidetector helical CT (MDCT) enables the acquisition of very thin slices (0.5 mm) in a 3D data set. Multiplanar Reformatting (MPR) of this data creates sagittal and coronal plane images, easy to use and interpret, also by non-radi- ologists. We have been fortunate to gain experience in using MDCT in patients with chronic ankle pain since the mid-1990s. In a recent study it was shown that MDCT with MPR performed as good as diagnostic
arthroscopy in detecting or excluding OCLs. Further- more no statistical signifi cant difference was found between MRI and MDCT in this study ( Verhagen et al. 2005). Helical CT gave more certainty than MRI that an OCL was present, where MRI was more cer- tain in a negative test result.
In order to emphasize the gaining role of MDCT in diagnosing OCL, various appearances of arthroscopi- cally proven OCLs are shown (Fig. 20.6). There is a wide spectrum of aspects of OCL on MDCT, ranging from a clear defect in the talar surface, with or without frag- ments within (Fig. 20.6), a small defect on the lateral fi bular surface (Fig. 20.7), to a subtle disturbance of normal bony architecture of the talar bone (Fig. 20.8).
Arthrography Combined with Cross-Sectional Imaging
MR arthrography, both direct and indirect, is described valuable in assessing osteochondral lesions in the ankle (Morrison 2003). It is thought to increase the depiction of unstable lesions; when gadolinium extends under the osteochondral lesion, it is classifi ed as unstable (Morrison 2003; DeSmet et al. 1996). In this way a differentiation can be made between a true unstable lesion and a stable lesion.
The MRI protocol needs adjustment, with inclu- sion of fat suppressed T1-weighted SE MR images ( Morrison 2003).
Fig. 20.5a,b. Extent of an OCL. Coronal TSTIR (a) and coronal reformatted MDCT (b). On the TSTIR images a cystic lesion is seen, however the surrounding edema masks the true extent of the lesion making it diffi cult for the surgeon to decide whether ankle arthroscopy is suffi cient, or whether osteotomy is necessary. The MDCT clearly defi nes the extent of the OCL
a b
There have been no reports on the accuracy of CT arthrography for detection of osteochondral lesions in the ankle. However, case reports and small studies suggest that CT arthrography may be a useful tool for assessing the stability or progno- sis of osteochondral lesion (Heire 1988; Davies 1989).
More recently it was shown that CT arthrogra- phy was superior to MRI, in evaluating cartilage lesions (MR arthrography), or cartilage thickness in the ankle (Schmid et al. 2003; El-Kouhry et al.
2004). The authors however do not have experience with this technique; the results of the study com- paring MDCT, MRI and arthroscopy do not make
Fig. 20.6a–c. Various appearances of OCL on MDCT. Coronal (a), sagittal (b) 2-mm MPR of MDCT dataset of the left ankle. A huge defect at the posteromedial part of the talus is seen (white arrows), while standard radiography was negative. A large osteochondral lesion is seen with multiple fragments within the defect (arrows) (b). A multicystic OCL, with a sclerotic border is seen on the lateral talar dome in another patient (black arrows) (c)
Fig. 20.7. Subtle OCL of the talus. Coronal 2-mm MPR. A very small osteochondral lesion is seen in the lateral talar surface with disrupted architecture (arrow)
Fig. 20.8. Subtle appearance of a talar OCL. Coronal MPR. The talar bony structure is disturbed in the posteromedial part (white arrow)
it necessary to make MRI an invasive technique in patients with an OCL of the ankle (Verhagen et al. 2005).
20.1.1.3.3 Staging
Classifi cation systems are described based on the various techniques described earlier. A short sum- mary is provided.
Radiographic
The classifi cation described by Berndt and Harty (1959) is still the still most frequently used. Stage I lesions are small areas of compressed subchondral bone (7%), stage II lesions are partially detached yet stable (25%), stage III lesions are completely detached but nondisplaced, located in the fragment bed (40%) and stage IV are displaced osteochondral fragments (28%) (Berndt and Harty 1959; Benthien et al.
2002).
MRI
One of the earliest MR based grading of OCLs in the talus was made in the late 1980s (Anderson et al.
1989). Stage I is bone marrow edema, nowadays called bone bruise, stage IIa shows a subchondral cyst, stage IIb incomplete separation of the fragments, stage III complete separation without dislocation, with dis- location in stage IV (Anderson et al. 1989; Josten and Rose 1999). The MRI criteria for instability of the fragment as defi ned by DeSmet et al. (1990), including high signal intensity on T2-weighted, fl uid passing through the subchondral bone or a fl uid- fi lled cyst located deep to the lesion correlated with arthroscopy (Manaster et al. 2005).
Computed Tomography
Using single slice CT Ferkel proposed a CT-based classifi cation of OCD lesions (Ferkel 1992; Ferkel and Scranton 1993; Linz et al. 2001; Benthien et al. 2002). Stage I lesion shows a subchondral cyst with an intact articular surface. Stage IIA shows communication between the cyst and the joint at the talar dome. A stage IIB lesion communicates with an overlying non-displaced fragment. A stage III lesion has a radiolucency around a non-displaced fragment and stage IV shows an unstable displaced fragment.
Arthroscopy
Various classifi cation systems are described, which are not all generally accepted. The most widely accepted staging classifi cation is from Ferkel; it shows grade A being smooth, intact cartilage which is soft and bal- lotable, stage B has got a rough surface, stage C shows fi brillation or fi ssures, in stage D a cartilage fl ap is present. Stage E shows a loose undisplaced fragment, with displacement of the fragment in stage F (Ferkel and Scranton 1993; Bohndorf 1998; Barnes and Ferkel 2003). However a good reproducibility study on arthroscopic staging is lacking.
Discussion on Staging
An interesting observation concerning radiological staging was described in a recent review (Verhagen et al. 2003). It was observed that the radiological classi- fi cation used varied, widely and that only a minority of authors had based their decision for selection of treat- ment on staging according to Berndt and Harty. It was concluded that preoperative staging is of minor impor- tance, and that intraoperative staging might be more appropriate. Not the staging of the lesion, but the clini- cal situation is the important feature. This is important for clinical practice. Radiologists are advised to check with their orthopedic surgeons whether a radiological classifi cation of the OCL is mandatory in preoperative planning. In this way the radiological strategy can be tailored to the need of the surgeon.
20.1.1.3.4 Treatment
Treatment options can be divided into operative or
non-operative options. Non-operative options such
as immobilization with casting for six to eight weeks
in early stages were described as being successful
( Pettine and Morrey 1987). Recent ISAKOS consen-
sus stated that asymptomatic or minor symptomatic
patients can be treated conservatively, consisting of
rest, ice, temporarily reduced weight bearing and in
some cases orthosis (Van Dijk 2005). Open surgical
procedures also have shown to produce good results
in the era prior to arthroscopy (Berndt and Harty
1959; Flick and Gould 1985). However nowadays
the most widely accepted therapy in case of any talar
OCL is arthroscopic excision, curettage (debridement)
and drilling. Many authors reported favorable results
(Benthien et al. 2002; Barnes and Ferkel 2003). A
recent systematic review, in which the effectiveness of
various treatment options was evaluated, confi rmed these results (Verhagen et al. 2003).
A newer operation technique, not included in previous mentioned systematic review is cartilage transplantation with mosaicplasty. It has been shown successful in a large cohort (Hangody et al. 2001).
However it should be reserved for those patients that do not respond to fi rst choice treatment of excision, curettage and drilling (Hangody 2004)
20.1.1.3.5 Pitfalls
The presence of kissing lesions, both in talus and tibia, is a well known entity (Sijbrandij et al. 2000;
Morrison 2003). It should not be mistaken for osteo- arthritis, especially when other signs of osteoarthritis (increased sclerosis, joint space narrowing and bone formation) are lacking.
When using MRI bone marrow edema is seen on both sides of the joint, while no focal pathology may be visible on T1-weighted images. MDCT may aid in correctly diagnosing the kissing lesions; this will guide arthroscopic intervention (Fig. 20.9).
Postoperative evaluation of an OCL is diffi cult. The anatomical situation has totally changed and without
adequate information concerning prior arthroscopy and current clinical situation of the patient the read- ing radiologist can be misguided (Fig 20.10).
Although arthroscopy is extremely accurate in detection talar OCLs, it seems less powerful in detect- ing the accompanying tibial lesions (Verhagen et al. 2005). It was stated that “satisfaction of search”
may be the mechanism being responsible for this:
the treating orthopedic surgeon is comfortable with the idea that the cause has been treated (i.e. the talar OCL), and fails to inspect the tibial plafond system- atically (Verhagen et al. 2005). This phenomenon is known from (osteo)-radiological studies and the sports radiologist dealing with OCL in the ankle should be aware of this phenomenon (Samuel et al.
1995; Ashman et al. 2000). Stressing the presence of lesions in both tibia and talar articular surface in the radiological report is advised.
20.1.2
Osseous Injury
In any sports an unexpected movement may cause acute osseous injury. The trauma mechanism will easily explain the fracture extension. The more fre-
Fig. 20.9a–c. Kissing OCL. Coronal TSTIR 3-mm MR image (a), T1-weighted spin echo (b) and axial 0.6-mm MDCT (c). On TSTIR edema is seen in the medial talus. In the cranial talar surface a separate cystic lesion is seen (arrow). More subtle bone marrow edema can be seen in the medial malleolus (double arrows). The T1-weighted MR image clearly defi nes the talar OCL.
No clear lesion in the medial malleolus is seen (b). The axial 0.6-mm CT clearly defi nes the kissing lesions in both talus and medial malleolus (arrows). A preserved joint space width is seen, therefore no osteoarthritis is diagnosed
b c
a
quent encountered fractures in the ankle are beyond the scope of this chapter. However a specifi c sports related fracture is discussed below.
20.1.2.1
Snowboarder’s Fracture
A well-documented sports related fracture is the fracture of the lateral process of the talus. In a pro- spective study of foot and ankle injuries in snow-
Fig. 20.11a,b. Snowboarder’s fracture. Coronal STIR (a), and sagittal (b) MPR of MDCT. Twenty-fi ve-year-old male with chronic ankle pain after ski trauma. Standard radiography was negative. MRI only showed edema in the lateral facet of the talus. No fracture was seen.
Additional MDCT with MPR enabled the diagnosis of a fracture (arrows)
a
b
Fig. 20.10a,b. Post opera- tive pitfall. Pre operative (a) and post operative (b) images of an OCL.
Coronal MPR MDCT.
The osteochondral defect is clearly seen with a large fragment (a). Two year postoperative (b), the OCL has healed.
Although no normal anatomy is achieved, the patient is without any complaints, so this must be regarded as a normal postoperative situation
a b
boarders a very high incidence of these fractures
was found (Kirkpatrick et al. 1998). It should be
noted that many of these fractures are not visible
on standard radiography. When MRI is performed,
usually in a later stage, when the patient is com-
plaining of chronic lateral ankle pain, bone marrow
edema is seen. However it may still be hard to diag-
nose the fracture. MDCT will aid in diagnosing this
lesion and can help the surgeon to tailor therapy
(Fig. 20.11).
20.2 The Foot
20.2.1
Osteochondral Injury
Osteochondral lesions of the foot can occur in the toes, especially in the fi rst toe. Although there is not much literature on the subject, in our experience this is not an uncommon encountered phenomenon.
It has been described in adolescent soccer players and elite ballet dancers and is characterized by pain, swelling and tenderness at the interphalangeal joint (Van Dijk et al. 1995; Kinoshita et al. 1998). Radio- graphic appearance is similar to the OCL in the ankle.
Therapy can also be arthroscopic curettage and drill- ing.
20.2.2
Sports Specifi c Acute Foot Injury
20.2.2.1 Turf Toe
Originally described in 1976 is the hyper extension injury of the fi rst metatarsophalangeal joint, occur- ring on a surface of artifi cial turf, hence turf toe and resulting in partial or complete disruption of the fi brocartilaginous plantar plate (Bowers and Martin 1976; Allen et al. 2004; Ashman et al. 2001).
This entity is described in detail in Chap. 19.
20.2.2.2
Skimboarder’s Toe
More recently an injury of the dorsal aspect of the fi rst metatarsophalangeal joint is described as a skimboarder’s toe (Donnely 2005). In this beach- side sport a hyperdorsal fl exion of the MTP joint causes injury to the extensor muscle, and the extensor expansion. On MRI a soft tissue swelling with edema is seen. The dorsal aspect of the extensor expansion is disrupted, while the plantar plate is intact. Bone marrow edema or joint effusion can accompany the lesion.
20.2.3
Overuse Injury of the Foot
20.2.3.1
Navicular Stress Fracture
Stress fractures of the navicular bone are famil- iar lesions in athletes (Pec´ina and Bojanic´ 2004).
They most often occur in explosive athletic activi- ties, involving jumping, sprinting and hurdling.
Chronic stress usually produces sagittal fractures of the navicular bone. The patients usually complain of a vague pain on the dorsum of the foot. On physical examination a localized painful point may be found on the proximal dorsal border. The navicular stress fracture will generally not be detected by plain radi- ology. As a rule of thumb, standard radiography is not sensitive enough to detect these stress fractures.
When there is a high clinical suspicion, further modalities can be used. Bone marrow edema is the key fi nding in diagnosing stress fractures with MRI.
A linear hypointense confi guration on T1-weighted MR sequences should be present when diagnosing a true fracture. The use of high resolution MDCT with 0.6-mm axial source images and MPR in any given plane aids in making a fi nal diagnosis. In order to detect navicular stress fracture the axial plane will be adequate (Fig. 20.12).
20.2.3.2
Sesamoid Overuse Injury
Stress related injury to the sesamoid bones, also known as sesamoiditis, is a common problem in athletes, who require maximum dorsiflexion of the great toe. Athletes at risk are joggers, sprint- ers, figure skaters, ballet dancers, basketball play- ers, football players and tennis players (Linz et al. 2001). It is a painful condition increased with weight bearing under the first metatarsal head, usually in the region of the medial rather than the lateral sesamoid.
Sesamoiditis on imaging can be seen as a broad
spectrum: A true stress fracture of the sesamoid
bone may be seen. However this has to be dif-
ferentiated from bipartite sesamoids, which can
occur in up to 75% of patients. Other findings,
include bone marrow edema without a fracture
line, reactive soft tissue edema, and tendinosis of
the flexor hallucis tendon. Synovitis and bursitis
are frequently associated. Some authors state that
when edema is seen on TSTIR or fat suppressed T2-
weighted MR images with absence of abnormali- ties on T1-weighted MR images, this is favorable for sesamoiditis. We have experience that MDCT can be helpful in these cases (Fig. 20.13).
References
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Things to Remember
1. Think about an osteochondral lesion of the ankle in a patient with chronic ankle pain.
2. Standard radiography can detect but will not exclude this lesion.
3. The most important feature of the osteochon- dral defect of the talus is the exact location and extent. This is the surgical question that radiology needs to answer.
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