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Improved accuracy and reproducibility of a novel CT-free robotic surgical assistant for medial unicompartmental knee arthroplasty compared to conventional instrumentation: a cadaveric study



Alignment errors in medial unicompartmental knee arthroplasty (UKA) predispose to premature implant loosening and polyethylene wear. The purpose of this study was to determine whether a novel CT-free robotic surgical assistant improves the accuracy and reproducibility of bone resections in UKA compared to conventional manual instrumentation.


Sixty matched cadaveric limbs received medial UKA with either the ROSA® Partial Knee System or conventional instrumentation. Fifteen board-certified orthopaedic surgeons with no prior experience with this robotic application performed the procedures with the same implant system. Bone resection angles in the coronal, sagittal and transverse planes were determined using optical navigation while resection depth was obtained using calliper measurements. Group comparison was performed using Student’s t test (mean absolute error), F test (variance) and Fisher's exact test (% within a value), with significance at p < 0.05.


Compared to conventional instrumentation, the accuracy of bone resections with CT-free robotic assistance was significantly improved for all bone resection parameters (p < 0.05), other than distal femoral resection depth, which did not differ significantly. Moreover, the variance was significantly lower (i.e. fewer chances of outliers) for five of seven parameters in the robotic group (p < 0.05). All values in the robotic group had a higher percentage of cases within 2° and 3° of the intraoperative plan. No re-cuts of the proximal tibia were required in the robotic group compared with 40% of cases in the conventional group.


The ROSA® Partial Knee System was significantly more accurate, with fewer outliers, compared to conventional instrumentation. The data reported in our current study are comparable to other semiautonomous robotic devices and support the use of this robotic technology for medial UKA.

Level of evidence

Cadaveric study, Level V.

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  1. 1.

    Casper DS, Fleischman AN, Papas PV, Grossman J, Scuderi GR, Lonner JH (2019) Unicompartmental knee arthroplasty provides significantly greater improvement in function than total knee arthroplasty despite equivalent satisfaction for isolated medial compartment osteoarthritis. J Arthroplasty 34:1611–1616

    Article  Google Scholar 

  2. 2.

    Hansen EN, Ong KL, Lau E, Kurtz SM, Lonner JH (2019) Unicondylar knee arthroplasty has fewer complications but higher revision rates than total knee arthroplasty in a study of large united states databases. J Arthroplasty 34:1617–1625

    Article  Google Scholar 

  3. 3.

    Kalbian IL, Tan TL, Rondon AJ, Bonaddio VA, Klement MR, Foltz C et al (2019) Reduced opioid requirements following unicompartmental knee arthroplasty compared with total knee arthroplasty. Bone Joint J 101-b:22–27

    CAS  Article  Google Scholar 

  4. 4.

    Kazarian GS, Lonner JH, Maltenfort MG, Ghomrawi HMK, Chen AF (2018) Cost-effectiveness of surgical and nonsurgical treatments for unicompartmental knee arthritis: a Markov model. J Bone Joint Surg Am 100:1653–1660

    Article  Google Scholar 

  5. 5.

    Noticewala MS, Geller JA, Lee JH, Macaulay W (2012) Unicompartmental knee arthroplasty relieves pain and improves function more than total knee arthroplasty. J Arthroplasty 27:99–105

    Article  Google Scholar 

  6. 6.

    The New Zealand Joint Registry. Twenty-one year report January 1999 to December 2019. 2020.

  7. 7.

    Dyrhovden GS, Lygre SHL, Badawy M, Gøthesen Ø, Furnes O (2017) Have the causes of revision for total and unicompartmental knee arthroplasties changed during the past two decades? Clin Orthop Relat Res 475:1874–1886

    Article  Google Scholar 

  8. 8.

    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:S124-130

    Article  Google Scholar 

  9. 9.

    Chatellard R, Sauleau V, Colmar M, Robert H, Raynaud G, Brilhault J (2013) Medial unicompartmental knee arthroplasty: does tibial component position influence clinical outcomes and arthroplasty survival? Orthop Traumatol Surg Res 99:S219-225

    CAS  Article  Google Scholar 

  10. 10.

    Kazarian GS, Barrack TN, Okafor L, Barrack RL, Nunley RM, Lawrie CM (2020) High prevalence of radiographic outliers and revisions with unicompartmental knee arthroplasty. J Bone Joint Surg Am 102:1151–1159

    Article  Google Scholar 

  11. 11.

    Conditt MA, Bargar WL, Cobb JP, Dorr LD, Lonner JH (2013) Current concepts in robotics for the treatment of joint disease. Adv Orthop 2013:948360

  12. 12.

    Dunbar NJ, Roche MW, Park BH, Branch SH, Conditt MA, Banks SA (2012) Accuracy of dynamic tactile-guided unicompartmental knee arthroplasty. J Arthroplasty 27:803-808.e801

    Article  Google Scholar 

  13. 13.

    Lonner JH (2009) Indications for unicompartmental knee arthroplasty and rationale for robotic arm-assisted technology. Am J Orthop (Belle Mead, NJ) 38:3–6

    Google Scholar 

  14. 14.

    Lonner JH, John TK, Conditt MA (2010) Robotic arm-assisted UKA improves tibial component alignment: a pilot study. Clin Orthop Relat Res 468:141–146

    Article  Google Scholar 

  15. 15.

    Lonner JH, Klement MR (2019) Robotic-assisted medial unicompartmental knee arthroplasty: options and outcomes. J Am Acad Orthop Surg 27:e207–e214

    Article  Google Scholar 

  16. 16.

    Lonner JH, Moretti VM (2016) The evolution of image-free robotic assistance in unicompartmental knee arthroplasty. Am J Orthop (Belle Mead NJ) 45:249–254

    Google Scholar 

  17. 17.

    Lonner JH, Smith JR, Picard F, Hamlin B, Rowe PJ, Riches PE (2015) High degree of accuracy of a novel image-free handheld robot for unicondylar knee arthroplasty in a cadaveric study. Clin Orthop Relat Res 473:206–212

    Article  Google Scholar 

  18. 18.

    Allen MW, Jacofsky DJ (2019) Evolution of robotics in arthroplasty. In: Lonner JH (ed) Robotics in Knee and hip arthroplasty: current concepts, techniques and emerging uses. Springer, Cham, pp 13–25.

    Chapter  Google Scholar 

  19. 19.

    Lonner JH, Fillingham YA (2018) Pros and cons: a balanced view of robotics in knee arthroplasty. J Arthroplasty 33:2007–2013

    Article  Google Scholar 

  20. 20.

    Ponzio DY, Lonner JH (2015) Preoperative mapping in unicompartmental knee arthroplasty using computed tomography scans is associated with radiation exposure and carries high cost. J Arthroplasty 30:964–967

    Article  Google Scholar 

  21. 21.

    Parratte S, Price AJ, Jeys LM, Jackson WF, Clarke HD (2019) Accuracy of a new robotically assisted technique for total knee arthroplasty: a cadaveric study. J Arthroplasty 34:2799–2803

    Article  Google Scholar 

  22. 22.

    Seidenstein A, Birmingham M, Foran J, Ogden S (2020) Better accuracy and reproducibility of a new robotically-assisted system for total knee arthroplasty compared to conventional instrumentation: a cadaveric study. Knee Surg Sports Traumatol Arthrosc.

    Article  PubMed  Google Scholar 

  23. 23.

    Lustig S, Scholes CJ, Oussedik S, Coolican MR, Parker DA (2014) Unsatisfactory accuracy with VISIONAIRE patient-specific cutting jigs for total knee arthroplasty. J Arthroplasty 29:249–250

    Article  Google Scholar 

  24. 24.

    Scholes C, Sahni V, Lustig S, Parker DA, Coolican MR (2014) Patient-specific instrumentation for total knee arthroplasty does not match the pre-operative plan as assessed by intra-operative computer-assisted navigation. Knee Surg Sports Traumatol Arthrosc 22:660–665

    Article  Google Scholar 

  25. 25.

    Bell SW, Anthony I, Jones B, MacLean A, Rowe P, Blyth M (2016) Improved accuracy of component positioning with robotic-assisted unicompartmental knee arthroplasty: data from a prospective, randomized controlled study. J Bone Joint Surg Am 98:627–635

    Article  Google Scholar 

  26. 26.

    Bush AN, Ziemba-Davis M, Deckard ER, Meneghini RM (2019) An experienced surgeon can meet or exceed robotic accuracy in manual unicompartmental knee arthroplasty. J Bone Joint Surg Am 101:1479–1484

    Article  Google Scholar 

  27. 27.

    Clark TC, Schmidt FH (2013) Robot-assisted navigation versus computer-assisted navigation in primary total knee arthroplasty: efficiency and accuracy. ISRN Orthop 2013:794827

  28. 28.

    Khare R, Jaramaz B, Hamlin B, Urish KL (2018) Implant orientation accuracy of a hand-held robotic partial knee replacement system over conventional technique in a cadaveric test. Comput Assist Surg (Abingdon) 23:8–13

    Article  Google Scholar 

  29. 29.

    MacCallum KP, Danoff JR, Geller JA (2016) Tibial baseplate positioning in robotic-assisted and conventional unicompartmental knee arthroplasty. Eur J Orthop Surg Traumatol 26:93–98

    Article  Google Scholar 

  30. 30.

    Mofidi A, Plate JF, Lu B, Conditt MA, Lang JE, Poehling GG et al (2014) Assessment of accuracy of robotically assisted unicompartmental arthroplasty. Knee Surg Sports Traumatol Arthrosc 22:1918–1925

    Article  Google Scholar 

  31. 31.

    Smith JR, Riches PE, Rowe PJ (2014) Accuracy of a freehand sculpting tool for unicondylar knee replacement. Int J Med Robot 10:162–169

    Article  Google Scholar 

  32. 32.

    Cobb J, Henckel J, Gomes P, Harris S, Jakopec M, Rodriguez F et al (2006) Hands-on robotic unicompartmental knee replacement: a prospective, randomised controlled study of the acrobot system. J Bone Joint Surg Br 88:188–197

    CAS  Article  Google Scholar 

  33. 33.

    Batailler C, White N, Ranaldi FM, Neyret P, Servien E, Lustig S (2019) Improved implant position and lower revision rate with robotic-assisted unicompartmental knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 27:1232–1240

    Article  Google Scholar 

  34. 34.

    Yoshioka Y, Siu DW, Scudamore RA, Cooke TD (1989) Tibial anatomy and functional axes. J Orthop Res 7:132–137

    CAS  Article  Google Scholar 

  35. 35.

    Liow MH, Tsai TY, Dimitriou D, Li G, Kwon YM (2016) Does 3-dimensional in vivo component rotation affect clinical outcomes in unicompartmental knee arthroplasty? J Arthroplasty 31:2167–2172

    Article  Google Scholar 

  36. 36.

    Clement ND, Bardgett M, Weir D, Holland J, Gerrand C, Deehan DJ (2018) What is the minimum clinically important difference for the WOMAC index after TKA? Clin Orthop Relat Res 476:2005–2014

    Article  Google Scholar 

  37. 37.

    Lizaur-Utrilla A, Gonzalez-Parreño S, Martinez-Mendez D, Miralles-Muñoz FA, Lopez-Prats FA (2020) Minimal clinically important differences and substantial clinical benefits for Knee Society Scores. Knee Surg Sports Traumatol Arthrosc 28:1473–1478

    Article  Google Scholar 

  38. 38.

    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 138:1463–1469

    Article  Google Scholar 

  39. 39.

    Ponzio DY, Lonner JH (2016) Robotic technology produces more conservative tibial resection than conventional techniques in UKA. Am J Orthop (Belle Mead NJ) 45:E465-e468

    Google Scholar 

  40. 40.

    Schwarzkopf R, Mikhael B, Li L, Josephs L, Scott RD (2013) Effect of initial tibial resection thickness on outcomes of revision UKA. Orthopedics 36:e409-414

    Article  Google Scholar 

  41. 41.

    Sires JD, Wilson CJ (2020) CT validation of intraoperative implant position and knee alignment as determined by the MAKO total knee arthroplasty system. J Knee Surg.

    Article  PubMed  Google Scholar 

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We are grateful to the orthopaedic surgeons who performed the cadaveric surgeries: Dr. Jeff Almand, Dr. Tomasz Antkowiak, Dr. Miles Birmingham, Dr. Nathan L. Cafferky, Dr. Michael A. Charters, Dr. Sridhar M. Durbhakula, Dr. Nicholas Frisch, Dr. Thomas John, Dr. Atul F. Kamath, Dr. Barry Kraushaar, Dr. W. Trevor North, Dr. Ari D. Seidenstein, Dr. Ahmed Siddiqi, Dr. Garen Daxton Steele and Dr. Charles Toulson.


This research was funded by Zimmer Biomet.

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Correspondence to Jess H. Lonner.

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Conflict of interest

Dr. Jess H. Lonner is a paid consultant for Zimmer Biomet and Smith & Nephew. Dr. Ari D. Seidenstein, Dr. Michael A. Charters, Dr. W. Trevor North, Dr. Nathan L. Cafferky, Dr. Sridhar M. Durbhakula and Dr. Atul F. Kamath are paid consultants for Zimmer Biomet.

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The study did not include research with animals or living human participants and was declared exempt by the local institutional review board.

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Lonner, J.H., Seidenstein, A.D., Charters, M.A. et al. Improved accuracy and reproducibility of a novel CT-free robotic surgical assistant for medial unicompartmental knee arthroplasty compared to conventional instrumentation: a cadaveric study. Knee Surg Sports Traumatol Arthrosc (2021).

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  • Unicompartmental knee arthroplasty
  • Robotic surgery
  • Conventional instrumentation
  • Bone resection
  • Accuracy
  • ROSA® Partial Knee System