Archives of Orthopaedic and Trauma Surgery

, Volume 139, Issue 2, pp 241–248 | Cite as

Risk factors of postoperative valgus malalignment in mobile-bearing medial unicompartmental knee arthroplasty

  • Qidong Zhang
  • Qian Zhang
  • Wanshou Guo
  • Man Gao
  • Ran Ding
  • Weiguo WangEmail author
Knee Arthroplasty



The aim of this observational study was to investigate the risk factors of postoperative valgus malalignment after mobile-bearing medial unicompartmental knee arthroplasty (UKA).


We retrospectively evaluated radiographic and surgical characteristics in 122 consecutive Oxford phase 3 UKAs. According to postoperative hip–knee–ankle angle (HKAA), 24 knees were sorted into group valgus with HKAA > 180° and 98 knees were sorted into group non-valgus with HKAA ≤ 180°. Logistic regression was performed to analyze risk factors including age, gender, BMI, side, preoperative limb alignment HKAA, preoperative LDFA, MPTA, FTFA, thickness of polyethylene bearing insert, tibial prothesis size, femoral prothesis size, medial tibial cut thickness, thickness of distal femoral mill, prothesis angle of coronal, and sagittal plane.


The mean mechanical preoperative HKAA of 174.39°±4.23° was corrected to 178.18°±3.49° postoperatively (t = − 13.45, p = 0.000). The mean of postoperative HKAA in valgus group and non-valgus group was 183.45 ± 2.21° and 176.88 ± 2.35°, respectively (t = 12.44, p = 0.000). After statistical analysis with univariate analysis, eight risk factor variables among 16 independent variables were identified as potential predictors with p value ≤ 0.1. Multivariate logistic regression analysis for these eight potential predictors revealed that tibial cut (p = 0.046), LDFA (p = 0.003), MPTA (p = 0.011), and FTFA (p = 0.008) were significant risk factors predicting postoperative valgus malalignment after mobile-bearing UKA.


Preoperative smaller LDFA, FTFA, larger MPTA and less medial tibial cut thickness were significantly associated with postoperative valgus malalignment in mobile-bearing UKA.


Unicompartmental knee arthroplasty Risk factor Alignment Radiologic Surgical technique 



We would like to thank the patients included in the study for their cooperations. We would also like to thank Mr Omar M. Fakhr, Department of Biological Science, The University of Tulsa, Tulsa, OK, 74104, USA, for the English improvement.


This study was funded by Beijing municipal science and technology commission (Grant number Z171100001017209), National Natural Science Foundation of China (Grant number 81703896), and the Capital Health Research and Development of Special (Grant number 2016-2-4062).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent for study participation was obtained from each patient.


  1. 1.
    Price AJ, Svard U (2011) A second decade lifetable survival analysis of the Oxford unicompartmental knee arthroplasty. Clin Orthop Relat Res 469:174–179Google Scholar
  2. 2.
    Emerson RH, Alnachoukati O, Barrington J, Ennin K (2016) The results of Oxford unicompartmental knee arthroplasty in the United States: a mean ten-year survival analysis. Bone Jt J 98-B:34–40Google Scholar
  3. 3.
    Repicci JA, Eberle RW (1999) Minimally invasive surgical technique for unicondylar knee arthroplasty. J South Orthop Assoc 8:20–27, 27Google Scholar
  4. 4.
    Ozcan C, Simsek ME, Tahta M, Akkaya M, Gursoy S, Bozkurt M (2018) Fixed-bearing unicompartmental knee arthroplasty tolerates higher variance in tibial implant rotation than mobile-bearing designs. Arch Orthop Trauma Surg 138:1463–1469Google Scholar
  5. 5.
    Panzram B, Bertlich I, Reiner T, Walker T, Hagmann S, Gotterbarm T (2017) Cementless Oxford medial unicompartimental knee replacement: an independent series with a 5-year-follow-up. Arch Orthop Trauma Surg 137:1011–1017Google Scholar
  6. 6.
    Guo WS, Zhang QD, Liu ZH, Cheng LM, Yue DB, Wang WG, Zhang NF, Li ZR (2015) Minimally invasive unicompartmental knee arthroplasty for spontaneous osteonecrosis of the knee. Orthop Surg 7:119–124Google Scholar
  7. 7.
    Campi S, Pandit HG, Oosthuizen CR (2018) The Oxford Medial Unicompartmental Knee Arthroplasty: The South African Experience. J Arthroplasty 33:1727–1731Google Scholar
  8. 8.
    Pandit H, Hamilton TW, Jenkins C, Mellon SJ, Dodd CA, Murray DW (2015) The clinical outcome of minimally invasive Phase 3 Oxford unicompartmental knee arthroplasty: a 15-year follow-up of 1000 UKAs. Bone Jt J 97-B:1493–1500Google Scholar
  9. 9.
    van der List JP, Zuiderbaan HA, Pearle AD (2016) Why do medial unicompartmental knee arthroplasties fail today?. J Arthroplasty 31:1016–1021Google Scholar
  10. 10.
    Felson DT, Niu J, Gross KD, Englund M, Sharma L, Cooke TD, Guermazi A, Roemer FW, Segal N, Goggins JM, Lewis CE, Eaton C, Nevitt MC (2013) Valgus malalignment is a risk factor for lateral knee osteoarthritis incidence and progression: findings from the Multicenter Osteoarthritis Study and the Osteoarthritis Initiative. Arthritis Rheum 65:355–362Google Scholar
  11. 11.
    Hernigou P, Deschamps G (2004) Alignment influences wear in the knee after medial unicompartmental arthroplasty. Clin Orthop Relat Res 423:161–165Google Scholar
  12. 12.
    Wen PF, Guo WS, Gao FQ, Zhang QD, Yue JA, Cheng LM, Zhu GD (2017) Effects of lower limb alignment and tibial component inclination on the biomechanics of lateral compartment in unicompartmental knee arthroplasty. Chin Med J (Engl) 130:2563–2568Google Scholar
  13. 13.
    Kang KT, Son J, Baek C, Kwon OR, Koh YG (2018) Femoral component alignment in unicompartmental knee arthroplasty leads to biomechanical change in contact stress and collateral ligament force in knee joint. Arch Orthop Trauma Surg 138:563–572Google Scholar
  14. 14.
    Kim SJ, Bae JH, Lim HC (2012) Factors affecting the postoperative limb alignment and clinical outcome after Oxford unicompartmental knee arthroplasty. J Arthroplasty 27:1210–1215Google Scholar
  15. 15.
    Mullaji AB, Shetty GM, Kanna R (2011) Postoperative limb alignment and its determinants after minimally invasive Oxford medial unicompartmental knee arthroplasty. J arthroplasty 26:919–925Google Scholar
  16. 16.
    Hopgood P, Martin CP, Rae PJ (2004) The effect of tibial implant size on post-operative alignment following medial unicompartmental knee replacement. Knee 11:385–388Google Scholar
  17. 17.
    Murray DW (2005) Mobile bearing unicompartmental knee replacement. Orthopedics 28:985–987Google Scholar
  18. 18.
    Marx RG, Grimm P, Lillemoe KA, Robertson CM, Ayeni OR, Lyman S, Bogner EA, Pavlov H (2011) Reliability of lower extremity alignment measurement using radiographs and PACS. Knee Surg Sports Traumatol Arthrosc 19:1693–1698Google Scholar
  19. 19.
    Moreland JR, Bassett LW, Hanker GJ (1987) Radiographic analysis of the axial alignment of the lower extremity. J Bone Jt Surg Am 69:745–749Google Scholar
  20. 20.
    Zhang Q, Yue J, Wang W, Chen Y, Zhao Q, Guo W (2018) FTFA change under valgus stress force radiography is useful for evaluating the correctability of intra-articular varus deformity in UKA. Arch Orthop Trauma Surg 138:1003–1009Google Scholar
  21. 21.
    Pandit H, Jenkins C, Gill HS, Barker K, Dodd CA, Murray DW (2011) Minimally invasive Oxford phase 3 unicompartmental knee replacement: results of 1000 cases. J Bone Jt Surg Br 93:198–204Google Scholar
  22. 22.
    Lisowski LA, van den Bekerom MP, Pilot P, van Dijk CN, Lisowski AE (2011) Oxford Phase 3 unicompartmental knee arthroplasty: medium-term results of a minimally invasive surgical procedure. Knee Surg Sports Traumatol Arthrosc 19:277–284Google Scholar
  23. 23.
    Badawy M, Espehaug B, Indrekvam K, Havelin LI, Furnes O (2014) Higher revision risk for unicompartmental knee arthroplasty in low-volume hospitals. Acta Orthop 85:342–347Google Scholar
  24. 24.
    Niinimaki T, Eskelinen A, Makela K, Ohtonen P, Puhto AP, Remes V (2014) Unicompartmental knee arthroplasty survivorship is lower than TKA survivorship: a 27-year Finnish registry study. Clin Orthop Relat Res 472:1496–1501Google Scholar
  25. 25.
    Epinette JA, Brunschweiler B, Mertl P, Mole D, Cazenave A (2012) Unicompartmental knee arthroplasty modes of failure: wear is not the main reason for failure: a multicentre study of 418 failed knees. Orthop Traumatol Surg Res 98:S124–S130Google Scholar
  26. 26.
    Vasso M, Corona K, D’Apolito R, Mazzitelli G, Panni AS (2017) Unicompartmental knee arthroplasty: modes of failure and conversion to total knee arthroplasty. Joints 5:44–50Google Scholar
  27. 27.
    Weale AE, Murray DW, Crawford R, Psychoyios V, Bonomo A, Howell G, O’Connor J, Goodfellow JW (1999) Does arthritis progress in the retained compartments after ‘Oxford’ medial unicompartmental arthroplasty? A clinical and radiological study with a minimum ten-year follow-up. J Bone Jt Surg Br 81:783–789Google Scholar
  28. 28.
    Emerson RJ, Higgins LL (2008) Unicompartmental knee arthroplasty with the oxford prosthesis in patients with medial compartment arthritis. J Bone Jt Surg Am 90:118–122Google Scholar
  29. 29.
    Lewold S, Robertsson O, Knutson K, Lidgren L (1998) Revision of unicompartmental knee arthroplasty: outcome in 1,135 cases from the Swedish Knee Arthroplasty study. Acta Orthop Scand 69:469–474Google Scholar
  30. 30.
    Mullaji AB, Shah S, Shetty GM (2017) Mobile-bearing medial unicompartmental knee arthroplasty restores limb alignment comparable to that of the unaffected contralateral limb. Acta Orthop 88:70–74Google Scholar
  31. 31.
    Kim KT, Lee S, Kim TW, Lee JS, Boo KH (2012) The influence of postoperative tibiofemoral alignment on the clinical results of unicompartmental knee arthroplasty. Knee Surg Relat Res 24:85–90Google Scholar
  32. 32.
    Gulati A, Pandit H, Jenkins C, Chau R, Dodd CA, Murray DW (2009) The effect of leg alignment on the outcome of unicompartmental knee replacement. J Bone Jt Surg Br 91:469–474Google Scholar
  33. 33.
    Mercier N, Wimsey S, Saragaglia D (2010) Long-term clinical results of the Oxford medial unicompartmental knee arthroplasty. Int Orthop 34:1137–1143Google Scholar
  34. 34.
    Xue H, Tu Y, Ma T, Wen T, Yang T, Cai M (2017) Up to twelve year follow-up of the Oxford phase three unicompartmental knee replacement in China: seven hundred and eight knees from an independent centre. Int Orthop 41:1571–1577Google Scholar
  35. 35.
    Maderbacher G, Baier C, Springorum HR, Zeman F, Grifka J, Keshmiri A (2016) Lower limb anatomy and alignment affect natural tibiofemoral knee kinematics: a cadaveric investigation. J Arthroplasty 31:2038–2042Google Scholar
  36. 36.
    Peersman G, Slane J, Vuylsteke P, Fuchs-Winkelmann S, Dworschak P, Heyse T, Scheys L (2017) Kinematics of mobile-bearing unicompartmental knee arthroplasty compared to native: results from an in vitro study. Arch Orthop Trauma Surg 137:1557–1563Google Scholar
  37. 37.
    Ahn JH, Kang HW, Yang TY, Lee JY (2016) Risk factors of post-operative malalignment in fixed-bearing medial unicompartmental knee arthroplasty. Int Orthop 40:1455–1463Google Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Qidong Zhang
    • 1
  • Qian Zhang
    • 2
  • Wanshou Guo
    • 1
  • Man Gao
    • 2
  • Ran Ding
    • 1
  • Weiguo Wang
    • 1
    Email author
  1. 1.Department of Orthopaedic Surgery, Beijing Key Lab Immune-Mediated Inflammatory DiseasesChina-Japan Friendship HospitalBeijingChina
  2. 2.Beijing University of Chinese MedicineBeijingChina

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