Localisation of Osteochondral Lesions of the Talar Dome: MRI
Transcription
Localisation of Osteochondral Lesions of the Talar Dome: MRI
Volume 03 / Issue 01 / March 2015 boa.ac.uk Page 46 JTO Peer-Reviewed Articles Localisation of Osteochondral Lesions of the Talar Dome: MRI Compared With Clinical Findings - Can The Site Of The Pain Predict The Site Of The Lesion? Mark Davies Osteochondral lesions (OCL) of the talar dome are defects of the cartilaginous surface and underlying bone1. The lesions range from a small defect in the talar articular surface, to lesions associated with a subchondral cyst, or a large detached osteochondral fragment2. Berndt and Harty3 proposed that such lesions are resultant on an intra-articular fracture, although others have suggested a possible genetic predisposition1,4. of poor scientific quality with anecdotal reporting of the sites of tenderness. Other pathologies frequently coexist with OCL, and this can lead to confusion in diagnosis. The purpose of this study was to investigate the relationship between the site of perceived pain, physical findings on examination and the location of the OCL on MRI scanning. Materials and Methods Recently Computerised Tomography (CT) and Magnetic Resonance Imaging (MRI) have led to more accurate imaging of these lesions, which in turn has led to new classifications. The new classifications record subchondral cysts9 and acute bone marrow oedema.10 Berndt and Harty described lesions as being antero-lateral or posteromedial, whilst MRI scanning localised 43% to the lateral and 57% to the medial sides of the talus. Lesions in the middle of the talus are rare, but have been reported1,12. Mark Davies Acutely OCL’s occur in 6.5% of all ankle sprains5,13. Chronically they are found in 20.5% of ankle sprains and 57% of cases of ankle disability14. OCL’s are one of the most important causes of residual pain after ankle sprain15. The clinical diagnosis is regarded as difficult10, and delay in establishing the diagnosis is common3. The pain associated with OCL’s has been noted to be generalised and non-specific8, similar to the symptoms of osteoarthritis. Localised tenderness is frequently lacking3,5,15, although localised tenderness has been described, usually postero-medially or antero-laterally in accordance with the site of the lesions3,5,8. Nevertheless, these studies are Patients identified as having chronic talar dome OCL’s on MRI were asked to indicate the point of maximal pain in their ankle and a removable skin marker was positioned at this site. Chronic OCL was defined as the presence of pain for more than three months. The position was independently measured and the skin marker was then removed. The patient was then examined to elicit the point of maximal tenderness in the ankle joint. The position was again marked and measured. The examiner was blinded to the first location and the measurements were taken blindly, the instrument readout was not visible whilst measurements were being made. The measurer and the examiner were both blind to the MRI findings, to eliminate bias. An adapted technique of anthropometrics was used to obtain orthogonal dimensions of >> Volume 03 / Issue 01 / March 2015 boa.ac.uk Page 48 JTO Peer-Reviewed Articles Figure 1: Digital callipers positioned to take the measurements the locations16,17,18. A frame with a moveable 90o angle bracket was constructed to use as a reference point for the measures. This base was level and marked with parallel lines for reference. Digital callipers were then positioned to take the measurements (Figure 1). For the best comparison of the measurements with MRI, a standard position was used. The subject placed their foot in the frame in the same position as their foot was in for the MRI (Figure 1). Figure 2: Measurements taken in the 3 axes Measurements were made using digital callipers held at 90 degrees to the axis measured, using the bracket to ensure that the calliper was in the correct position. Trial measures were taken to test for reliability and repeatability. Measures were then taken in three axes, moving the 90 degree angle bracket into the correct position to measure from the landmarks below (Figure 2). X (medial to lateral) - from the medial malleolus in a lateral direction Y (caudal to cranial) - from the plantar surface in a superior direction Z (posterior to anterior) - from the Achilles tendon insertion in an anterior direction The MRI scan and reports were then reviewed for each patient. Digital measures were replicated from the same landmarks above, to the centre of the lesion. Reference lines were added between each view and between the slices of each view (Figure 3). Measures were taken from these reference lines on separate occasions to test reliability and repeatability. The orientation of the foot in each view was set with reference lines through each slice, using equivalent landmarks used in the direct measurements. Coronal View – a line parallel to the orientation of the leg (Figure 3) Axial View – a line parallel to the anatomical axis of the foot, through the second ray (Figure 4) of the ankle joint, was taken as the equivalent (Figure 4). Axial views were disregarded if the plane of the image did not correspond to the plane of the foot, such as occurs in a very plantar flexed foot position at the time of MRI (Figure 4). The “Z” (posterior to anterior) measure taken in this view thus represented the hypotenuse not the direct measure. Figure 3: MRI of ankle in the coronal plane showing reference line; a line parallel to the orientation of the leg and measurements taken from this line Sagittal View – a line parallel to the plantar surface of the foot If the image did not show the landmark sufficiently well due to the size of area shown or the number of slices taken, we used equivalent points that were found to be representative. This occurred mostly in the axial view, if there were insufficient slices for the second ray to be visualised. A line through the centre of the Achilles tendon to the lateral border of the tibialis anterior tendon, at the level Analysis of the data was carried out to test for correlations between measures made of the lesion as identified by the subject, the examiner and the measures from the MRI in all three axes. The Euclidean distance between the measures was calculated and descriptive statistics produced for each measure group. In addition, the 95% confidence interval was calculated to show the range of measures to be expected in any population, to show the degree of association between them. Results A total of 19 patients with OCL were recruited. The methods and equipment used, proved to be repeatable and reproducible (unpublished data). Using the frame and callipers was repeatable and reproducible to within 2.7mm. The tools on the computer system for the MRI were repeatable to within 3.4mm. In terms of whether the lesion was medial or lateral; the subject and examiner agreed in 84% of cases, the subject’s location of pain agreed with the MRI in 58% of cases and the examiner’s location of tenderness agreed with the MRI in 63% of cases. Figure 4: MRI of ankle in the axial plane showing reference line; a line parallel to the anatomical axis of the foot, through the second ray and measurements taken from this line Agreement with respect to the localisation between quadrants in two planes, i.e. antero-lateral, postero-medial etc., the subject Volume 03 / Issue 01 / March 2015 boa.ac.uk Page 49 © 2015 British Orthopaedic Association Journal of Trauma and Orthopaedics: Volume 03, Issue 01, pages 46-49 Title: Localisation of Osteochondral Lesions of the Talar Dome: MRI Compared With Clinical Findings - Can The Site Of The Pain Predict The Site Of The Lesion? Authors: Mark Davies and examiner agreed in 63% of cases, the subject’s location of pain agreed with the MRI in 42% of cases and the examiner’s location of tenderness agreed with the MRI in 37% of cases. Figures 5, 6 and 7 show these location points as scatter plots with Pearson correlation coefficients. These plots in each plane demonstrate the degree of spread. Scatter plots of the locations between the subject and examiner show the best correlation with the highest correlation in the coronal plane (X axis, 0.87), whilst the lowest correlation was in the sagittal plane (Z axis, 0.38). The subjects’ localisation of pain and the location of the OCL on MRI were generally more poorly correlated with the lowest correlation also in the coronal plane (X axis, 0.49). Correlation between the maximum tenderness as assessed by the examiner and the location of the OCL on MRI was higher in all three planes compared to that localised by the subject correlated with the MRI. It was highest in the axial plane (Y axis, 0.82) and again lowest in the coronal plane (X axis, 0.62). The range of Euclidean distances, between the locations was high, ranging from 6mm to 59mm. The location as assessed by the subject was, on average, 30mm away from the location found by the examiner. The subject generally localised pain further from the lesion on MRI than did the examiner on palpation. Discussion Figure 6: Location points as scatter plots with Pearson correlation coefficients between Subject Locations vs. MRI Locations in all 3 planes Different authors suggest symptoms differ between lesion sites and that pinpoint tenderness can be elicited1,19,20. References to physical findings include tenderness in the antero-lateral corner of the tibio-talar joint for lateral lesions and in the antero medial corner for medial lesions8. Fransom21 and Berlet22 found that with the addition of plantar flexion and dorsiflexion respectively, antero-lateral lesions can be palpated antero-laterally, and postero-medial lesions may be palpated posterior to the medial malleolus; however neither group provided supporting evidence for these claims. Verhagen, in their prospective study on diagnostic strategies, did not evaluate the findings on physical examination in isolation15. Although they specified the locations of lesions and endeavoured to determine the diagnostic value of clinical findings, they did not relate them to routine radiological examination. Figure 5: Location points as scatter plots with Pearson correlation coefficients between Subject Locations vs. Examiner Locations in all 3 planes Figure 7: Location points as scatter plots with Pearson correlation coefficients between Examiner Locations vs. MRI Locations in all 3 planes The scale of the measures has to be taken into account when considering any relationship. The dimension of an average sized talus is approximately 50mm in both the sagittal and coronal planes, thus a separation between the subject’s localisation of pain and the examiner’s assessment of maximal tenderness of 50mm represents the whole width or depth of the articular surface of the talus. Thus, a medial lesion may present with lateral pain and tenderness and vice versa. The source of pain when there is damage to articular cartilage and subchondral bone is unclear. Articular cartilage is not innervated and is therefore not the direct source of the pain23,24,25. Associations between subarticular bone marrow changes and pain are strong and these are analogous to the changes seen in OCL, but whether this is a direct source of pain is unclear23,24,26. In this study, the pain experienced by the patient and the area of tenderness found, were as variable to each other as to the actual site of the lesion. We suggest that OCL of the talar dome result in pain that is poorly localised, with respect to the site of the lesion, and the area of maximum tenderness. As a result, vaguely located ankle pain with poor clinical localisation would warrant MRI to exclude an OCL. Care must be taken when attributing an OCL on an MRI to the subject’s pain. Mark Davies is a Consultant Orthopaedic Surgeon at Northern General Hospital, Sheffield specialising in elective and trauma of the adult foot and ankle. He co-ordinates the research activity for the Sheffield Foot and Ankle Unit. Correspondence: Email: [email protected] References can be found online at www.boa.ac.uk/publications/JTO or by scanning the QR Code. References 1. Mandracchia, VA; Buddecke, DE; Giesking JL: Osteochondral Lesions of the Talar Dome. Clinics in Podiatric Medicine and Surgery. 16(4): 725-42, 1999. 2. Assenmacher, JA; Kelikian, AS; Gottlob, C; et al: Arthroscopically Assisted Autologous Osteochondral Transplantation for Osteochondral Lesions of the Talar Dome: An MRI and Clinical Follow-Up Study. Foot and Ankle Int. 22(7): 544-51, 2001. 3. Berndt, AL; Harty, M. Transchondral Fractures (Osteochondritis Dissecans) of the Talus. J. Bone and Joint Surg. 41-A(6): 988-1020, 1959. 4. Bohndorf, K. 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