Abstract
Background
Currently, an anteroposterior radiograph of the knee is judged based on a centered position of the patella between the femoral condyles. We are not aware of any anatomic literature supporting this recommendation.
Questions/Purposes
Orthogonal images are required for accurate assessment of knee deformity. Although an image with the patella centered at the distal femur is generally accepted as a true anteroposterior (AP) radiograph of the knee, there is minimal anatomic data to support that this view is orthogonal to a true lateral view of the knee where the condyles are overlapped. We designed an anatomical study to test the relationship between these two radiographic views.
Methods
We studied 428 well-preserved cadaveric skeletons ranging from 40 to 79 years of age at death. Centering of the patella was calculated based on distal femoral and patellar widths. Multiple regression analysis was then performed to determine the relationship between patellar centering and age, gender, ethnicity, mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), femoral anteversion, and contralateral centering.
Results
Average patellar centering was 0.13 ± 0.04, indicating that the average patella was laterally positioned in the distal femur. Only mLDFA and contralateral centering showed statistically significant independent correlations with patellar centering with modest standardized beta coefficients of 0.10 and 0.23, respectively.
Conclusions
In the average specimen, the patella is laterally deviated by 13% of the condylar width. Clinicians should be aware that a lateral view with the femoral condyles overlapped is not always orthogonal to a patella-centered AP view when planning and implementing deformity correction.
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References
Colebatch AN, Hart DJ, Zhai G, Williams FM, Spector TD, Arden NK. Effective measurement of knee alignment using AP knee radiographs. Knee. 2009; 16(1): 42-45.
Fang DM, Ritter MA, Davis KE. Coronal alignment in total knee arthroplasty: just how important is it? J Arthroplasty. 2009; 24(6 Suppl): 39-43.
Hollister AM, Jatana S, Singh AK, Sullivan WW, Lupichuk AG. The axes of rotation of the knee. Clin Orthop Relat Res. 1993; 290: 259-268.
Kawahara S, Matsuda S, Okazaki K, et al. Relationship between the tibial anteroposterior axis and the surgical epicondylar axis in varus and valgus knees. Knee Surg Sports Traumatol Arthrosc. 2012; 20(10): 2077-2081.
Liu RW, Toogood P, Hart DE, Davy DT, Cooperman DR. The effect of varus and valgus osteotomies on femoral version. J Pediatr Orthop. 2009; 29(7): 666-675.
Luo CF. Reference axes for reconstruction of the knee. Knee. 2004; 11(4): 251-257.
Merchant A. Radiologic evaluation of the patellofemoral joint. In: Aichroth P, Cannon WD, Patel DV, eds. Knee surgery: current practice. London: CRC Press; 1992: 380-388.
Nagamine R, Miura H, Inoue Y, et al. Reliability of the anteroposterior axis and the posterior condylar axis for determining rotational alignment of the femoral component in total knee arthroplasty. J Orthop Sci. 1998; 3(4): 194-198.
Paley D. Principles of deformity correction. New York: Springer; 2002.
Paley D, Herzenberg JE, Tetsworth K, Mckie J, Bhave A. Deformity planning for frontal and sagittal plane corrective osteotomies. Orthop Clin N Am. 1994; 25(3): 425-465.
Whiteside LA, Arima J. The anteroposterior axis for femoral rotational alignment in valgus total knee arthroplasty. Clin Orthop Relat Res. 1995; 321: 168-172.
Disclosures
Conflict of Interest
Ademola A. Ajuwon, MD, Ronak Desai, MD and Kathleen Farhang, BS have declared that they have no conflict of interest. Colin E. Lasko reports other from ArthroCare Corp and Zimmer Inc., outside the work. Raymond W. Liu, MD reports other from Orthopediatrics LLC, outside the work.
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This article does not contain any studies with human or animal subjects performed by the any of the authors.
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Ajuwon, A.A., Desai, R., Farhang, K. et al. An Anatomic Study on Whether the Patella is Centered in an Ideal Anteroposterior Radiograph of the Knee. HSS Jrnl 11, 117–122 (2015). https://doi.org/10.1007/s11420-014-9419-3
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DOI: https://doi.org/10.1007/s11420-014-9419-3