Radiological evaluation of the causes of patellar instability.

Transcription

1 Radiological evaluation of the causes of patellar instability. Poster No.: C-0054 Congress: ECR 2014 Type: Authors: Keywords: DOI: Educational Exhibit J. M. Spaccesi Pau, D. Pomato, N. CEDOLA; La Plata/AR Diagnostic procedure, Plain radiographic studies, Musculoskeletal joint, Extremities, Dysplasias /ecr2014/C-0054 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 11

2 Learning objectives An accurate radiological assessment of predisposing factors to patellar instability. Background Although patellar instability is a clinical syndrome and MRI is the best method to assess tisular injuries, radiographs as an initial method are able to deliver a good perspective into the cause of instability. Findings and procedure details The most important predisposing factors for Patellar Instability are: 1) Trochlear Dysplasia. 2) Patella Alta. 3) Lateralization of Tibial Tuberosity. 1) Trochlear Dysplasia is the most important factor because it is found in nearly 100% of patellar dislocations, it can be evaluated in radiographs by the crossing sign (Fig. 1) and the supratrochlear spur (Fig. 2), which are of great diagnostic value since they are present in 96% of the objective instabilities, 12% of knee pain syndromes, and only 2% of normal knees. 2) Patella Alta is observed in % of objective instabilities, it is occasionally bilateral and is frequently found in recurrent dislocations. It is produced by an abnormally long patellar tendon, which can be assessed by the Insall-Salvati index (Fig. 3). 3) The lateralization of Tibial Tuberosity (TT) generates a valgus strenght vector when the extensor apparatus is put to work, which predisposes to lateral dislocation of the patella. Although CT is the best way to evaluate the position of the TT, it can be indirectly assessed in plain radiographics by the quadriceps angle (Q angle) (Fig. 4). Images for this section: Page 2 of 11

3 Fig. 1: Crossing Sign. The green line and the yellow line represent the anterior portion of both femoral condyles. The red line represent de bottom of the trochlea. Normally, the red line should never cross the others. Page 3 of 11

4 Fig. 2: Supratrochlear Spur. A line tangent to the last 10cm of the femur cortex is drawn, then the prominence ahead that line is measured. A spur of more than 3mm is considered pathological. Page 4 of 11

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6 Fig. 3: Insall-Salvati Index. Is the ratio between the distance from the inferior margin of patella to the tibial insertion of the patella tendon, and the lenght of the patella. Normally the ratio is 0,8 to 1,2. An Insall-Salvati Index greater than 1,2 is considered Patella Alta. Page 6 of 11

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8 Fig. 4: Q Angle. The angle formed by a line drawn from the ASIS to central patella and a second line drawn from central patella to tibial tubercle. A Q Angle greater than 15 is considered a risk factor to patellar dislocation. Page 8 of 11

9 Conclusion There are several factors that influence Patelar Instability. All of them can be evaluated by plain radiology, which is a fast, economical and highly available method to provide an approximated diagnose. Personal information J. M. Spaccesi Pau, Department of Radiology, CIMED, Calle 5 n 416, La Plata, Argentina. D. Pomato, Department of Radiology, CIMED, Calle 5 n 416, La Plata, Argentina. N. Cedola, Department of Radiology, CIMED, Calle 5 n 416, La Plata, Argentina. References [1]Rev. Asoc. Arg. Ortop. y Traumatol., 1990;55(4): Desequilibrios Femoro-Patelares Paús V [2]Knee Surg Sports Traumatol Arthrosc. 1994;2(1): Factors of patellar instability: an anatomic radiographic study. Dejour H, Walch G, Nove-Josserand L, Guier C. [3]Radiology Oct;101(1):101-4 Patella position in the normal knee joint. Insall J, Salvati E. [4]Arch Iranian Med 2007; 10 (1): Page 9 of 11

10 Q-angle: An Invaluable Parameter for Evaluation of Anterior Knee Pain Emami MJ, Ghahramani MH, Abdinejad F, Namazi H. [5]Radiographics Jul-Aug;30(4): MR imaging of patellar instability: injury patterns and assessment of risk factors. Diederichs G, Issever AS, Scheffler S. [6]Revista Chilena de Radiología. Vol. 16 Nº 3, año 2010; IMAGING STUDIES OF THE PATELLOFEMORAL JOINT: OUR CURRENT REALITY Drs Edith Miranda V, Sara Muñoz Ch (1), Paola Paolinelli G (1), Claudia Astudillo A (1), [7]Acta Orthop Belg. 1989;55(3): Patella alta in patellofemoral instability. Geenen E, Molenaers G, Martens [8]Am J Roentgenol 1993; 161: Transient lateral patellar dislocation: diagnosis with MR imaging. Kirsch MD, Fitzgerald SW, Friedman H, Rogers LF. [9]Radiol Med Jan-Feb;101(1-2): Radiologic assessment of femoro-patellar instability. Personal experience and review of the literature Cusmano F, Adravanti P, Pedrazzini M, Ampollini A, Pavone P. [10]J Am Acad Orthop Surg Jan;19(1):8-16. The role of trochlear dysplasia in patellofemoral instability. Bollier M, Fulkerson JP. Page 10 of 11

11 [11]Surg Radiol Anat. 1990;12(2): An anatomical and radiological study of the femoropatellar articulation. Galland O, Walch G, Dejour H, Carret JP. [12]Rev Chir Orthop Reparatrice Appar Mot. 1990;76(1): Dysplasia of the femoral trochlea Dejour H, Walch G, Neyret P, Adeleine P. [13]Acta Orthop Belg. 1989;55(3): Radiology in femoro-patellar pathology Walch G, Dejour H. [14]Radiology Dec;225(3): Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar softtissue restraints and osteochondral injuries of the inferomedial patella. Elias DA, White LM, Fithian DC. Page 11 of 11