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KneeFocus On...

Navigation for TKR

R. Walker, M. Monda, S. Chauhan
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Computer navigation in total knee replacement (TKR) has been widely available since 2002. Since then, two key debates have emerged. First, does computer navigation improve accuracy of implant positioning and alignment? and secondly, does any such improvement result in enhanced longevity of the prosthesis?

Accuracy of Alignment

Restoring normal mechanical axis of the limb in the coronal plane has always been one of the main goals for knee arthroplasty surgeons in order to reduce the risk of early implant failure as a result of accelerated wear and aseptic loosening. Early single-centre studies of computer-navigated TKR showed superior alignment in the coronal, sagittal and rotational planes.1,2 Since these early studies, which had relatively small sample sizes, more data have been published to support better alignment with navigation. However, the difference between navigated and conventional TKR is perhaps smaller than was first expected.3

Coronal malalignment of more than 3° has been shown to cause premature implant failure.4-6 A large meta-analysis7 of randomised controlled trials showed that navigation reduces the number of patients with post-operative malalignment of more than 3°, although the mean alignment and mechanical axis do not differ between navigated and conventional TKR groups. The relative risk of a deviation of more than 3° from the straight mechanical axis by using navigation was 0.76 compared with conventional TKR. Another comprehensive meta-analysis8 estimated this risk to be 31.8% for conventional TKR but 9% for navigated TKR. Meanwhile Kim et al9 demonstrated that there was no difference in alignment and orientation between navigated and traditional TKRs at bilateral TKR, with one side being navigated and the other side not.

Predictive finite element analysis on real patient data has shown that contact stresses on the polyethylene tibial insert were reduced by 12% in a series of navigated TKRs compared with conventional TKR.10 Logically, this difference should result in enhanced implant longevity.

Additional Benefits of Navigation

To achieve balance in TKR, careful bone resection and soft-tissue release must be performed. Failure to release contracted collateral ligaments can lead to accelerated implant wear, especially when treating severe deformity,11 although excessive collateral ligament release can lead to instability. Using real-time navigation measurement and two intra-operative tests, Hakki et al12 were able to predict the need for collateral release with high sensitivity and specificity. Release was necessary in only ten of 93 patients (10.8%), significantly fewer than the 50%11 to 76%13 that have been reported elsewhere. Similar results have been demonstrated by other groups,14,15 suggesting that navigation may allow a more quantifiable approach to soft-tissue balance and lead to fewer patients needing a collateral ligament release.

In one randomised controlled trial,16 patients who underwent a navigated TKR suffered 396 ml less blood loss than patients undergoing TKR using intramedullary jigs; this resulted in fewer patients requiring a blood transfusion in the navigated group. In a similar study17 by the same author, patients undergoing navigated TKR had fewer cerebrovascular emboli detected by transcranial duplex Doppler ultrasound. Systemic emboli measured by transoesophageal echocardiography are also reduced in navigated TKR.18 Other authors have reported a reduction in post-operative confusion in patients who have received a navigated TKR.1 There is some evidence that the C-reactive protein level, a marker of systemic inflammatory response, is reduced with a navigated TKR.19 All these positive effects would seem related the avoidance of damage to the medullary cavity of bone at navigated TKR.

Clinical outcome

Clinical outcome can only truly be assessed by properly conducted, randomised controlled trials. These would require at least five years’ follow-up and large numbers of patients to give adequate power to a study, in order to identify a modest reduction in revision rates, or an improvement in knee scores. As yet, no studies meet these criteria and, therefore, there are currently no clinical data to show improved long-term outcomes with navigated TKR. There is some limited evidence of improved function and quality of life within the first post-operative year for patients with a navigated TKR;20 short-term function also appears to be improved by better coronal alignment of the limb after TKR.21 However Spencer et al22 reported no difference in clinical outcome at two years despite superior alignment in their navigated TKR group. As a result of the improved lifespan of modern implants, it may be that many more years of follow-up will be needed in order to demonstrate a difference between the techniques.

Learning Curve

There is a learning curve associated with adopting any new technique. Jenny, Miehlke and Giurea 23 showed in a multicentre trial that there were no differences in implant position, clinical outcome and complications between beginner and established centres. Operative time was longer for beginner centres but this difference disappeared after 30 procedures.


Navigation increases the duration of surgery by 23% or 17 minutes;7 however, there is no increase in the rate of infection. There have been cases of femoral fracture secondary to drill holes used in the placement of infra-red trackers.24-26 Consequently, many would recommend unicortical fixation of trackers to prevent this complication.


As there are no long-term outcome data for the procedure, it is presently impossible to determine whether computer navigation is cost effective. Novak, Silverstein and Bozic 27 performed a cost analysis based on current data and found that if equipment is purchased, computer navigation in the USA adds $1500 to the cost of an operation. However, in the UK most centres lease equipment; this results in a smaller cost increase of approximately £150 per operation. As fewer instrument sets must be sterilised for a navigated procedure, much of this additional outlay is recouped by the hospital. Computer navigation is most likely to be cost effective in high volume centres. Slover et al28 estimated that an annual reduction in revision rates of 2% would be required over 20 years in a centre which performed 250 navigated TKRs per year in order to be cost effective.


Future Technologies

The majority of computer navigation systems currently available rely on infra-red emitting or reflecting trackers; these are fixed to the bones of the patient or to instruments. A frustrating, technical aspect of navigated TKR is loss of the line of sight between trackers and the computer because of intervening theatre personnel and equipment, or contamination of the trackers by blood. Electromagnetic and radiofrequency tracking systems do not require line of sight between the computer and the trackers. These have been shown to be as accurate as infra-red systems in clinical trials.29 Specially-designed instruments such as drills, saw blades and cutting blocks are now available for use with navigation systems. These can reduce the operating time and may also improve accuracy.

Other Applications

Navigation is perfectly suited for use in other areas of knee surgery. Peri-articular osteotomies for osteoarthritis and the correction of deformity can be guided by the real-time measurement of angles determined during pre-operative planning and may be more accurate and reproducible.30 Navigation is also suitable for both minimally invasive TKR31 and unicompartmental knee replacement,32 where restricted access to anatomical landmarks can cause difficulty with implant positioning and the referencing of bone cuts. In addition, navigation may have a role to play in establishing the best location for bone tunnels during anterior cruciate ligament reconstruction.33


Computer-navigated TKR is well established in many centres and appears safe and relatively easy to learn. Its main benefit is a reduction in the number of TKRs that have a coronal malalignment of more than 3°. In the long-term, this may result in fewer revision procedures for early implant failure. However, as yet there are no data to support this claim. In addition, there is some evidence that blood loss and systemic emboli are reduced using navigation as opposed to intramedullary jigs. Navigation may assist the surgeon to achieve a proper soft-tissue balance, thereby reducing the number of patients who require collateral ligament release and the subsequent risk of post-operative instability. Operative time is slightly longer when using navigation but this does not appear to cause additional morbidity. As yet, there is no convincing economic argument favouring computer navigation. However, in high-volume centres, a small reduction in the early revision rate can justify the additional cost. Overall, computer navigation is a useful additional tool for the orthopaedic surgeon who seeks to perform a total knee replacement and to achieve accuracy of alignment.


1.      Chauhan SK, Clark GW, Scott RG, Lloyd S, Sikorski JM. Computer assisted total knee replacement: a controlled cadaver study using a multi-parameter quantitative CT assessment of alignment (the Perth CT Protocol). J Bone Joint Surg [Br] 2004; 86-B:818-23.

2.      Sparmann M, Wolke B, Czupalla H, Banzer D, Zink A. Positioning of total knee arthroplasty with and without navigation support. A prospective, randomised study. J Bone Joint Surg [Br] 2003;85-B:830-5.

3.      Lützner J, Krummenauer F, Wolf C, Günther KP, Kirschner S. Computer-assisted and conventional total knee replacement: a comparative, prospective, randomised study with radiological and CT evaluation. J Bone Joint Surg [Br] 2008;90-B:1039-44.

4.      Miller MC, Berger RA, Petrella AJ, Karmas A, Rubash HE. Optimizing femoral component rotation in total knee arthroplasty. Clin Orthop 2001;392:38-45.

5.      Sharkey PF, Hozack WJ, Rothman RH, et al. Why are total knee arthroplasties failing today? Clin Orthop 2002;404:7.

6.      Fehring TK, Odum S, Griffin WL, et al. Early failures in total knee arthroplasty. Clin Orthop 2001;392:315

7.      Bauwens K, Matthes G, Wich M, Gebhard F, Hanson B, Ekkernkamp A, Stengel D. Navigated total knee replacement. A meta-analysis. J Bone Joint Surg [Am] 2007;89-A:261-9.

8.      Mason JB, Fehring TK, Estok R, Banel D, Fahrbach K. Meta-analysis of alignment outcomes in computer-assisted total knee arthroplasty surgery. J Arthroplasty 2007;22:1097-106.

9.      Kim YH, Kim JS, Choi Y, Kwon OR. Computer-assisted surgical navigation does not improve the alignment and orientation of the components in total knee arthroplasty. J Bone Joint Surg [Am] 2009;91-A:14-9.
10.  M Norris, W Schmidt, A Wang, RA Beaver, S Chauhan. Effectiveness of navigation-based TKR in enhancing the mechanical performance of knee system components [abstract]. ESSKA Congress 2006.

11.  Engh GA. The difficult knee: severe varus and valgus. Clin Orthop  2003;416:58-63.

12.  Hakki S, Coleman S, Saleh K, Bilotta VJ, Hakki A. Navigational predictors in determining the necessity for collateral ligament release in total knee replacement. J Bone Joint Surg [Br] 2009;91-B:1178-82.

13.  Whiteside LA, Saeki K, Mihalko WM. Functional medial ligament balancing in total knee arthroplasty. Clin Orthop 2000;380:45-57.

14.  Saragaglia D, Chaussard C, Rubens-Duval B. Navigation as a predictor of soft tissue release during 90 cases of computer-assisted total knee arthroplasty. Orthopedics 2006;29(10 Suppl):S137-8.

15.  Han SB, Nha KW, Yoon JR, Lee DH, Chae IJ. The reliability of navigation-guided gap technique in total knee arthroplasty. Orthopedics 2008;31(10 Suppl 1).

16.  Kalairajah Y, Simpson D, Cossey AJ, Verrall GM, Spriggins AJ. Blood loss after total knee replacement: effects of computer-assisted surgery. J Bone Joint Surg [Br] 2005;87-B:1480-2.

17.  Kalairajah Y, Cossey AJ, Verrall GM, Ludbrook G, Spriggins AJ. Are systemic emboli reduced in computer-assisted knee surgery?: A prospective, randomised, clinical trial. J Bone Joint Surg [Br] 2006;88-B:198-202.

18.  Church JS, Scadden JE, Gupta RR, Cokis C, Williams KA, Janes GC. Embolic phenomena during computer-assisted and conventional total knee replacement. J Bone Joint Surg [Br] 2007;89-B:481-5.

19.  Shen H, Zhang N, Zhang X, Ji W. C-reactive protein levels after 4 types of arthroplasty. Acta Orthop 2009;80:330-3.

20.  Choong PF, Dowsey MM, Stoney JD. Does accurate anatomical alignment result in better function and quality of life? Comparing conventional and computer-assisted total knee arthroplasty. J Arthroplasty 2009;24:560-9.

21.  Longstaff LM, Sloan K, Stamp N, Scaddan M, Beaver R.. Good alignment after total knee arthroplasty leads to faster rehabilitation and better function. J Arthroplasty 2009;24:570-8.

22.  Spencer JM, Chauhan SK, Sloan K, Taylor A, Beaver RJ. Computer navigation versus conventional total knee replacement: No difference in functional results at two years. J Bone Joint Surg [Br] 2007;89-B:477-80.

23.  Jenny JY, Miehlke RK, Giurea A. Learning curve in navigated total knee replacement. A multi-centre study comparing experienced and beginner centres. Knee 2008;15:80-4.

24.  Panasiuk M, Bończak O. Fatigue fracture of the femur after navigated total knee replacement. Ortop Traumatol Rehabil 2009;11:72-7.

25.  Bonutti P, Dethmers D, Stiehl JB. Case report : femoral shaft fracture resulting from femoral tracker placement in navigated TKA. Clin Orthop 2008;466:1499-502.

26.  Ossendorf C, Fuchs B, Koch P. Femoral stress fracture after computer navigated total knee arthroplasty. Knee 2006;13:397-9.

27.  Novak EJ, Silverstein MD, Bozic KJ. The cost-effectiveness of computer-assisted navigation in total knee arthroplasty. J Bone Joint Surg [Am] 2007;89-A:2389-97.

28.  Slover JD, Tosteson AN, Bozic KJ, Rubash HE, Malchau H. Impact of hospital volume on the economic value of computer navigation for total knee replacement. J Bone Joint Surg [Am] 2008;90-A:1492-500.

29.  Lionberger DR, Weise J, Ho DM, Haddad JL. How does electromagnetic navigation stack up against infrared navigation in minimally invasive total knee arthroplasties? J Arthroplasty 2008;23:573-80.

30.  Bae DK, Song SJ, Yoon KH. Closed-wedge high tibial osteotomy using computer-assisted surgery compared to the conventional technique. J Bone Joint Surg [Br] 2009;91-B:1164-71.

31.  Dutton AQ, Yeo SJ. Computer-assisted minimally invasive total knee arthroplasty compared with standard total knee arthroplasty. Surgical technique. J Bone Joint Surg [Am] 2009;91-A (Suppl 2 Pt 1):116-30.

32.  Seon JK, Song EK, Park SJ, Yoon TR, Lee KB, Jung ST. Comparison of minimally invasive unicompartmental knee arthroplasty with or without a navigation system. J Arthroplasty 2009;24:351-7.

33.  Pearle AD, Kendoff D, Musahl V, Warren RF. The pivot-shift phenomenon during computer-assisted anterior cruciate ligament reconstruction. J Bone Joint Surg [Am] 2009;91-A  (Suppl 1):115-18.