Robotic-arm Assisted Total Knee Arthroplasty: the Relationship between Bone Resection, Gap Balancing and Resultant Implant Alignment

Document Type : RESEARCH PAPER


1 Royal Infirmary of Edinburgh, Edinburgh, UK

2 Newcastle upon Tyne Hospitals NHS Foundation Trust, UK


Objectives: The primary aim was to assess the association between bone resection and the resultant 
flexion and extension gaps in the medial and lateral compartments of the knee when performing robotic -
arm assisted total knee arthroplasty (rTKA). The secondary aims were to compare medial and lateral 
bone resections and the influence on limb alignment, and whether the amount of bone resection that 
resulted in equal gaps was predictable.
Methods: A prospective study of 22 consecutive patients with a mean age of 66 years undergoing rTKA was 
conducted. The femoral component was mechanically aligned, and the alignment of the tibial component was 
adjusted (+/-3degrees of the mechanical axis) to obtain equal extension and flexion gaps. All knees underwent soft 
tissue balancing using sensor-guided technology. The final compartmental bone resection, gaps, and implant 
alignment were obtained from the robot data archive.
Results: There was a correlation between bone resection and the resultant gap in the medial (r=0.433, p=0.044) 
and lateral (r=0.724, p<0.001) compartments of the knee. There were no differences in bone resection from the 
distal femur and posterior condyles in the medial (p=0.941) or lateral compartments (p=0.604) or for the resultant 
gaps (p=0.341 and p=0.542, respectively). There was more bone removed from the medial compartment compared 
to the lateral aspect: 0.9mm (p=0.005) in extension and 1.2mm (p=0.026) flexion. The differential bone resection 
changed the knee alignment by one degree of varus. There were no significant differences between the actual and 
predicted medial (difference 0.05, p=0.893) or lateral (difference 0.00, p=0.992) tibial bone resection. 
Conclusion: There was a direct association between bone resection and resultant compartment joint gap when 
using rTKA, which was predictable. Gap balancing was achieved when less bone was resected from the lateral 
compartment which resulted in an estimated one-degree varus alignment of the knee. 
 Level of evidence: II


Main Subjects

1. Ng N, Clement ND, Gaston P, Simpson P, Macpherson GJ,
Patton JT. Robotic-arm assisted versus manual total hip
arthroplasty: a systematic review and meta-analysis. Bone
Joint J. 2021; 103-B (6):1009-1020. doi: 10.1302/0301-
2. Khlopas A, Sodhi N, Sultan AA, Chughtai M, Molloy RM, Mont
MA. Robotic Arm-Assisted Total Knee Arthroplasty. J
Arthroplasty 2018; 33(7):2002-2006. doi:
3. Kayani B, Haddad FS. Robotic total knee arthroplasty: clinical
outcomes and directions for future research. Bone Joint Res
2019; 8(10):438-442. doi: 10.1302/2046-3758.810.BJR2019-0175.
4. Hampp EL, Sodhi N, Scholl L, et al. Less iatrogenic soft-tissue
damage utilizing robotic-assisted total knee arthroplasty
when compared with a manual approach: A blinded
assessment. Bone Joint Res 2019; 8(10):495-501. doi:
5. Riviere C, Iranpour F, Auvinet E, et al. Alignment options for
total knee arthroplasty: A systematic review. Orthop
Traumatol Surg Res 2017; 103(7):1047-1056. doi:
6. Jaffe WL, Dundon JM, Camus T. Alignment and Balance
Methods in Total Knee Arthroplasty. J Am Acad Orthop Surg
2018; 26(20):709-716. doi: 10.5435/JAAOS-D-16-00428.
7. Clement ND, Deehan DJ. Knee biomechanics: Will we ever
know the truth? Bone Joint Res 2018; 7(5):325-326. doi:
8. Walker LC, Clement ND, Ghosh KM, Deehan DJ. What is a
balanced knee replacement? EFORT Open Rev 2018;
3(12):614-619. doi: 10.1302/2058-5241.3.180008.
9. Eckhoff DG, Bach JM, Spitzer VM, Reinig KD, Bagur MM,
Baldini TH, Flannery NM. Three-dimensional mechanics,
kinematics, and morphology of the knee viewed in virtual
reality. J Bone Joint Surg Am 2005; 87 Suppl 2:71-80. doi:
10. Oussedik S, Abdel MP, Victor J, Pagnano MW, Haddad FS.
Alignment in total knee arthroplasty. Bone Joint J 2020; 102-
B (3):276-279. doi: 10.1302/0301-620X.102B3.BJJ-2019-
11. Chang JS, Kayani B, Wallace C, Haddad FS. Functional
alignment achieves soft-tissue balance in total knee
arthroplasty as measured with quantitative sensor-guided
technology. Bone Joint J 2021; 103-B (3):507-514. doi:
12. Clement ND, Calliess T, Christen B, Deehan DJ. An alternative
technique of restricted kinematic alignment of the femur and
gap balanced alignment of the tibia using computer aided
navigation. Bone Joint Res 2020; 9(6):282-284. doi:
13. Gustke KA, Golladay GJ, Roche MW, Elson LC, Anderson CR. A
new method for defining balance: promising short-term
clinical outcomes of sensor-guided TKA. J Arthroplasty 2014;
29(5):955-960. 10.1016/j.arth.2013.10.020.
14. Alston GL, Haltom WR. Evidence of Criterion Validity for One
Pharmacy School's Progress Examination Program. Am J
Pharm Educ 2016; 80(8):135. doi: 10.5688/ajpe808135.
15. Shepherd DE, Seedhom BB. Thickness of human articular
cartilage in joints of the lower limb. Ann Rheum Dis 1999;
58(1):27-34. doi: 10.1136/ard.58.1.27.
16. Okazaki K, Miura H, Matsuda S, et al. Asymmetry of
mediolateral laxity of the normal knee. J Orthop Sci 2006; 11(3):264-266. doi: 10.1007/s00776-006-1009-x.
17. Bellemans J, Vandenneucker H, Vanlauwe J, Victor J. The
influence of coronal plane deformity on mediolateral
ligament status: an observational study in varus knees. Knee
Surg Sports Traumatol Arthrosc 2010; 18(2):152-156. doi:
18. Freeman MA, Pinskerova V. The movement of the normal
tibio-femoral joint. J Biomech 2005; 38(2):197-208. doi:
19. McEwen P, Balendra G, Doma K. Medial and lateral gap laxity
differential in computer-assisted kinematic total knee
arthroplasty. Bone Joint J 2019; 101-B (3):331-339. doi:
20. Insall JN. Total knee replacement. Surgery of the knee. 1 Ed.
New York: Churchill Livingston, 1984: pp 587-696.
21. Hutt JR, LeBlanc MA, Masse V, Lavigne M, Vendittoli PA.
Kinematic TKA using navigation: Surgical technique and
initial results. Orthop Traumatol Surg Res 2016; 102(1):99-
104. doi: 10.1016/j.otsr.2015.11.010.
22. MacDessi SJ, Griffiths-Jones W, Chen DB,et al. Restoring the
constitutional alignment with a restrictive kinematic protocol
improves quantitative soft-tissue balance in total knee
arthroplasty: a randomized controlled trial. Bone Joint J 2020;
102-B (1):117-124. doi: 10.1302/0301-620X.102B1.BJJ2019-0674.R2.
23 Decking J, Theis C, Achenbach T, Roth E, Nafe B, Eckardt A.
Robotic total knee arthroplasty: the accuracy of CT-based
component placement. Acta Orthop Scand 2004; 75(5):573-
579. doi: 10.1080/00016470410001448.
24. Clement ND, Deehan DJ. Minimum reporting criteria for
robotic assisted total knee arthroplasty studies: alignment
and balancing techniques should both be defined. Bone Joint
Res 2020; 9(6):279-281. doi: 10.1302/2046-3758.96.BJR2020-0033.R2.
25. Shelton TJ, Gill M, Athwal G, Howell SM, Hull ML. Outcomes in
Patients with a Calipered Kinematically Aligned TKA That
Already Had a Contralateral Mechanically Aligned TKA. J Knee
Surg. 2021; 34(1):87-93. doi: 10.1055/s-0039-1693000.
26. MacDessi SJ, Griffiths-Jones W, Chen DB, et al. restoring the
constitutional alignment with a restrictive kinematic protocol
improves quantitative soft-tissue balance in total knee
arthroplasty: a randomized controlled trial. Bone Joint J 2020;
102-B (1):117-124. doi: 10.1302/0301-620X.102B1.BJJ2019-0674.R2.
27. Held MB, Grosso MJ, Gazgalis A, et al. Improved Compartment
Balancing Using a Robot-Assisted Total Knee Arthroplasty.
Arthroplast Today 2021; 7:130-134. doi:
28. Bardou-Jacquet J, Murgier J, Laudet F, Fabre T. Combining
load sensor and robotic technologies for ligament balance in
total knee arthroplasty. Orthop Traumatol Surg Res 2021;
102889. doi: 10.1016/j.otsr.2021.102889.
29. Kayani B, Konan S, Horriat S, Ibrahim MS, Haddad FS.
Posterior cruciate ligament resection in total knee
arthroplasty: the effect on flexion-extension gaps,
mediolateral laxity, and fixed flexion deformity. Bone Joint J
2019; 101-B (10):1230-1237. doi: 10.1302/0301-