Is an x-ray of the knee sufficient to assess the alignment of the leg? A study of total joint replacement with surgical navigation.

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Daniel Vaquero


Background: Understanding the femorotibial mechanical axis (FTMA) of the leg is a necessary requirement to assess the outcome of total knee replacement (TKR). Short radiographs, which only capture the knee joint and do not include the center of the femoral head and center of the ankle, only provide us the anatomical axis (FTAA), and not the FTMA. The purpose of this study was to compare the FTMA and FTAA before and after navigated TKR.

Methods: In 130 patients undergoing surgery to implant the same TKR model, an x-ray was taken including the hip, knee and ankle. Images were analysed using a computer program that calculates the mechanical and anatomical axis of the femur, tibia and femorotibial joint. An image-free navigation system with femorotibial tensioned gap technique was used for the arthroplasty implantation. After surgery, a new long x-ray was taken, where the measurements indicated above were taken again.

Results: Pre-operative x-rays showed a mean difference of 6º between FTAA and FTMA (p<0.001). No significant interaction was seen with patient height, but it was in patients with varus deformity and higher BMI (p=0.029); the greatest discrepancy between the anatomical and mechanical axis of the limb was found in individuals with excess weight. After TKR, the mean FTMA was modified to achieve a neutral axis (180° ±3°), as well as a concentration of the figures that showed great pre-procedure disparity, which was verified by the difference in the pre- and post-operative SD (11.85 versus 3.13). The maximum difference between FTAA and FTMA, which stood at 18º before decreased to 5.5º post-TKR.

Conclusions: There is a major discrepancy between the FTAA and FTMA that increases when there is pre-operative varus deformity and in patients with excess weight. After TKR, the FTMA became concentrated, and the mean axis shifted towards the neutral axis. Performing x-rays that only include the knee is not useful for assessing the limb’s alignment prior to or after TKR.

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VAQUERO, Daniel. Is an x-ray of the knee sufficient to assess the alignment of the leg? A study of total joint replacement with surgical navigation.. Medical Research Archives, [S.l.], v. 10, n. 7, july 2022. ISSN 2375-1924. Available at: <>. Date accessed: 08 aug. 2022. doi:
Research Articles


1.-Evans JT, Walker RW, Evans JP, Blom AW, Sayres A, Whitehouse MR. How long does a knee replacement last? A systematic review and meta-analysis of case series and national registry reports with more than 15 years of follow-up. Lancet. 2019; 393:655-63. doi: 10.1016/S0140-6736(18)32531-5.
2.-Mahdi A, Svantesson M, Wretenberg P, Hälleberg-Nyman M. Patients’ experiences of discontentment one year after total knee arthroplasty- a qualitative study. BMC Musculoskelet Disord. 2020; 21:29. doi: 10.1186/s12891-020-3041.
3.-Nakano N, Shoman H, Olavarria F, Matsumoto T, Kuroda R, Khanduja V. Why are patients dissatisfied following a total knee replacement? A systematic review. Int Orthop.2020; 44:1971-2007. doi: 10.1007/s00264-020-04607-9.
4.- Sharkey PF, Hozack WJ, Rothman RH, Shastri S, Jacoby SM. Why Are Total Knee Arthroplasties Failing Today? Clin Orthop. 2002; 404:7-13. doi: 10.1097/00003086-200211000-00003.
5.-Liu H-X, Shang P, Ying X-Z, Zhang Y. Shorter survival rate in varus‑aligned knees after total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. 2016; 24:2663–71. doi: 10.1007/s00167-015-3781-7.
6.- Glenday JD, Wright TM, Lipman JD, Sculco PK, Mayman DJ, Vigdorchik JM, Quevedo-Gonzalez FJ. Effect of varus alignment on the bone-implant interaction of a cementless tibial baseplate during gait. J Orthop Res. 2021; 40:816-25. doi: 10.1002/jor.25129.
7.- Kazarian GS, Haddad FS, Donaldson M, Wignadasan W, Nunley RM, Barrack RL. Implant malalignment may be a risk factor for poor patient-reported outcomes measures (PROMs) following total knee arthroplasty (TKA). J Arthroplasty. 2022; 37: S129-S33. doi: 10.1016/j.arth.2022.02.087.
8.- Begum FA, Kayani B, Magan AA, Chang JS, Haddad FS. Current concepts in total knee arthroplasty: mechanical, kinematic, anatomical, and functional alignment. Bone Jt Open. 2021; 2:397-404. doi: 10.1302/2633-1462.26.BJO-2020-0162.R1.
9.-Waldt S , Eiber M, Woertler K. Measurements and classifications in musculoskeletal radiology. Edit Thieme, Munich, Germany; 2014.
10.- Mikulicz J. The side curvatures on the knee and theirs healing methods. Arch Klin Chir. 1879;23:561-29.
11. Moreland Jr, Bassett LW, Hanker GJ. Radiographic analysis of the axial alignment of the lower extremity. J Bone Joint Surg. 1987;69-A:745-9.
12. Griffiths-Jones W, Chen DB, Harris IA, Bellemans J, MacDessi SJ. Arithmetic hip-knee-ankle angle (aHKA): An algorithm for estimating constitutional lower limb alignment in the arthritic patient population. Bone Jt Open. 2021;2:351-8. doi: 10.1302/2633-1462.25.BJO-2021-0028.R1.
13.- Huang NFR, Dowsey MM, Ee E, Stoney JD, Babazadeh S, Choong PF. Coronal alignment correlates with outcome after total knee arthroplasty. Five-year follow-up of a randomized controlled trial. J Arthroplasty. 2012; 27:1737-41. doi: 10.1016/j.arth.2012.03.058.
14.- Hungerford DS, Krackow KA. Total joint arthroplasty of the knee. Clin Orthop. 1985; 192:23-33.
15.- Insall JN, Binazzi R, Soudry M, Mestriner LA. Total knee arthroplasty. Clin Orthop. 1985;192:13-22.
16.-Freeman MAR, Swanson SAV, Todd, RC. Total replacement of the knee using the Freeman-Swanson knee prosthesis. Clin Orthop. 1973. 94:153-70.
17.- Abdel MP, Oussedik S, Parratte S, Lustig S. Haddad FS. Coronal alignment in total knee replacement. Historical review, contemporary analysis and future direction. Bone Joint J.2014;96-B:857-62. doi: 10.1302/0301-620X.96B7.33946.
18.- Krackow KA. The technique of total knee arthroplasty. Edit The C.V.Mosby Company, St Louis, EEUU; 1990.
19.- Gromov K,Korchi M, Thomsen MG, Husted H,Troelsen A. What is the optimal alignment of the tibial and femoral components in knee arthroplasty? An overview of the literature. Acta Orthop. 2014; 85 : 480-7. doi: 10.3109/17453674.2014.940573.
20.- Oh S.M, Bin S-I, Kim J-Y, Lee B-S, Kim J-M. Short knee radiographs can be inadequate for estimating TKA alignment in knees with bowing. Knee Surg Rel Res. 2020; 32:9. doi: 10.1186/s43019-019-0020-4.
21.-Hernandez-Vaquero D, Noriega-Fernandez A, Suarez-Vazquez A, Roncero-Gonzalez S, Sierra-Pereira AA, Gil-Martinez L, Fernandez-Carreira JM. Frontal alignment in total knee arthroplasty. Comparative study between radiographic measurement and surgical navigation. Rev Esp Cir Ortop Traumatol. 2017. 61:313-8. doi: 10.1016/j.recot.2017.03.007.
22.- Wunderlich F, Azad M, Westphal R, Klonschinski T, Belikan P, Drees P, Eckhard L. Comparison of postoperative coronal leg alignment in customized individually made and conventional total knee arthroplasty. J Pers Med. 2021.11:549. doi: 10.3390/jpm11060549.
23.- Gielis WP, Rayegan H, Arbabi V, Brooghani SYA, Lindner C, Cootes TF, de Jong PA, Weinans H, Custers RJH. Predicting the mechanical hip–knee–ankle angle accurately from standard knee radiographs: a cross-validation experiment in 100 patients. Acta Orthop. 2020; 91:732-7. doi: 10.1080/17453674.2020.1779516.
24. Lee SA, Choi S-H, Chang MJ. How accurate is anatomic limb alignment in predicting mechanical limb alignment after total knee arthroplasty? BMC Musculoskelet Disord. 2015; 16:323. doi: 10.1186/s12891-015-0756-2.
25.- Park A, Stambough JB, Nunley RM, Barrack RL, Nam D. The inadequacy of short knee radiographs in evaluating coronal alignment after total knee arthroplasty. J Arthroplasty. 2016; 31: 878-82. doi: 10.1016/j.arth.2015.08.015.
26.- Nam D, Vajapey S, Nunley RM, Barrack RL. The impact of imaging modality on the measurement of coronal plane alignment following total knee arthroplasty. J Arthroplasty. 2016; 31:2314-9. doi: 10.1016/j.arth.2016.02.063.
27.- Tammachote N, Kriengburapha N, Chaiwuttisak A, Kanitnate S, Boontanapibul K. Is regular knee radiograph reliable enough to assess the knee prosthesis position? J Arthroplasty. 2018; 33:3038-42. doi: 10.1016/j.arth.2018.05.014.
28.- Stickley CD, Wages JJ, Hetzler RK, Andrews SN, Nakasone CK. Standard radiographs are not sufficient for assessing knee mechanical axis in patients with advanced osteoarthritis. J Arthroplasty. 2017; 32:1013-7. doi: 10.1016/j.arth.2016.09.024
29.- Colebatch AN, Hart DJ, Zhai G, Williams FM, Spector TD, Arden NK. Effective measurement of knee alignment using AP knee radiographs. Knee. 2009; 16:42-5. doi: 10.1016/j.knee.2008.07.007.
30.- Felson DT, Cooke TDV, Niu J, Goggins J, Choi J, Yu J, Nevit MC, OAI Investigators Group. Can anatomic alignment measured from a knee radiograph substitute for mechanical alignment from full limb films? Osteoarthritis Cartilage. 2009;17:1448-52. doi: 10.1016/j.joca.2009.05.012.
31.- Graden NR, Dean RS, Kahat DH, DePhillipo NN, LaPrade RF. True mechanical alignment is found only on full-limb and not on standard anteroposterior radiographs. Arthrosc Sports Med Rehabil. 2020; 15:e753-e759. doi: 10.1016/j.asmr.2020.06.010.
32.- Shatrov J, Parker D. Computer and robotic - assisted total knee arthroplasty: a review of outcomes. J Exp Orthop. 2020; 7:70. doi: 10.1186/s40634-020-00278-y.
33.- Bendich I, Kapadia M, Alpaugh K, Diane A. Vigdorchik J,Westrich G. Trends of utilization and 90-day complication rates for computer-assisted navigation and robotic assistance for total knee arthroplasty in the United States from 2010 to 2018. Arthroplasty Today. 2021; 11:134-9. doi: 10.1016/j.artd.2021.08.005.
34.- Kirwan DP, B Imis YP, Harris IA. Increased early mortality in bilateral simultaneous TKA using conventional instrumentation compared with technology-assisted surgery. A study of 34,908 procedures from a National Registry. J Bone Joint Surg Am. 2021;103:2177-80. doi: 10.2106/JBJS.21.00029.
35.- Matar HE, Platt SR, Bloch BV, Board TN, Porter ML, Cameron HU, James PJ. Three orthopaedic operations, over 1,000 randomized controlled trials, in over 100,000 patients. What have we learnt? Bone Joint Res. 2022;11 :23-5. doi: 10.1302/2046-3758.111.BJR-2021-0341.