Lateral trochlear inclination (LTI) is the inclination angle between the femoral trochlea and a posterior condylar tangential line 1.
Lateral trochlear inclination (LTI) is used in the assessment of trochlear dysplasia, a dysplastic deformity of the femoral head, which is known risk factor for patellofemoral instability 1-5. It has been primarily introduced for magnetic resonance imaging 1. A review of the quality assessment of measurements for trochlear dysplasia identified the lateral trochlear inclination (LTI) as the most useful measurement 3.
Traditionally the inclination angle is measured between the bony contours of the lateral trochlear facet on the most superior/proximal axial slice containing trochlear cartilage and a posterior condylar tangential line at the same level 1.
Modifications and alternative measurements
Recently a modification has been proposed addressing possible problems with the transitional anatomy of the condyles at the level, where the original version of the lateral trochlear inclination (LTI) was measured. The modification was found more reliable in that study 4,5.
The modified inclination angle is measured between the bony contours of the lateral trochlear facet and a posterior condylar tangential line at the level, where the femoral condyles are best definable 4,5, which is usually further below, about 2 cm above the joint line.
The cut-off angle for the original measurement <11° indicates trochlear dysplasia, with a reported sensitivity and specificity of 93% and 87% respectively 1.
The modified version suggests a threshold at ≤8.9° with a reported sensitivity and specificity of 68% and 90% 5.
History and etymology
The lateral trochlear inclination angle was introduced by Carillon et al in 2000 1.
- 1. Carrillon Y, Abidi H, Dejour D, Fantino O, Moyen B, Tran-Minh VA. Patellar instability: assessment on MR images by measuring the lateral trochlear inclination-initial experience. (2000) Radiology. 216 (2): 582-5. doi:10.1148/radiology.216.2.r00au07582 - Pubmed
- 2. Dietrich TJ, Fucentese SF, Pfirrmann CW. Imaging of Individual Anatomical Risk Factors for Patellar Instability. (2016) Seminars in musculoskeletal radiology. 20 (1): 65-73. doi:10.1055/s-0036-1579675 - Pubmed
- 3. Paiva M, Blønd L, Hölmich P, Steensen RN, Diederichs G, Feller JA, Barfod KW. Quality assessment of radiological measurements of trochlear dysplasia; a literature review. (2018) Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA. 26 (3): 746-755. doi:10.1007/s00167-017-4520-z - Pubmed
- 4. Sheeba M. Joseph, Christopher Cheng, Matthew J. Solomito, J. Lee Pace. LATERAL TROCHLEAR INCLINATION IN CHILDREN AND ADOLESCENTS: MODIFIED MEASUREMENT TECHNIQUE TO CHARACTERIZE PATELLAR INSTABILITY:. (2019) Orthopaedic Journal of Sports Medicine. doi:10.1177/2325967119S00146
- 5. Christopher Cheng, Jon Hedgecock, Matthew Solomito, Sheeba Joseph, J. Lee Pace. DEFINING TROCHLEAR DYSPLASIA VIA THE LATERAL TROCHLEAR INCLINATION ANGLE:. (2020) Orthopaedic Journal of Sports Medicine. doi:10.1177/2325967120S00179