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Healio
September 01, 2008
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Computer-assisted Surgery: A Wine Before Its Time

Mark W. Pagnano, MD
Mark W. Pagnano		  

In 2008, computer-assisted surgery in total knee replacement (TKR) remains a cumbersome, time-consuming, expensive tool with no proven clinical benefit. As surgeons, we all share common goals in TKR. We want to make this procedure as reliable, durable, and safe as possible as we try to deliver pain relief and improve function for our patients. Unfortunately, the computer does not help us attain any of those goals. This might be acceptable if computer navigation were a brand new technology, came at no cost, added no unique complications, and did not increase operative time. In contrast, we are now entering the second decade of clinical use with navigation systems (with some manufacturers trumpeting 10 years of clinical experience in media advertisements). They remain costly to obtain and maintain, fracture through pin sites are a reported complication, and they all add time to surgery. An article in the Journal of Bone and Joint Surgery reported a comprehensive meta-analysis of 11 randomized, controlled trials of total knee navigation. Bauwens et al1 concluded that “the navigated knee replacement provides few advantages over conventional surgery and its clinical benefits are unclear and remain to be defined.”

The fundamental premise of computer-assisted surgery is that axial alignment along a neutral mechanical axis will result in better TKR survivorship in the mid or long term. However, the scientific support for that contention is surprisingly weak (Table). Every study that has been considered evidence to support the contention of a neutral mechanical axis is limited for various reasons. Some studies only included short-leg radiographs that cannot calculate the mechanical axis.3-6 Another study is a rudimentary implant design consisting of a noncondylar roller and trough design.7 Moreland8 published a review article that includes no new scientific data.

Table: Substantial Scientific Limitations of Prior Research on Alignment in TKR

A study by Jeffery et al7 included long-term follow-up with long-leg radiographs that reported the results of the Denham knee design. The Denham knee is unfamiliar to most surgeons and includes many features that are no longer deemed desirable: a roller in a trough articulation, no trochlear groove, an all-polyethylene tibial component through which a Steinman pin is placed to help with alignment, and a long fixed intramedullary stem on the femoral side. With 10-year follow-up, Jeffery et al7 reported that 4 more Denham knees loosened when they were aligned outside a neutral mechanical axis.

Given the lack of quality long-term data, we recently reviewed the Mayo Clinic experience to examine the effect of mechanical axis alignment on 15-year survival of modern cemented, condylar TKR designs.9 This study included 400 TKRs with 3 modern condylar designs (kinematic condylar, press-fit condylar, and genesis I). Preoperative and postoperative long-leg radiographs were available in every case so that the mechanical axis could be measured. Fifteen-year survival was not better when the mechanical axis was restored to 0±3°, the typical target for computer-assisted surgery. These findings held up for each of the 3 knee designs, as well as for each type of preoperative alignment (varus, valgus, neutral). Therefore, at 15 years we were unable to confirm the underlying premise of computer-assisted surgery. This data allows us to report that factors other than alignment were more important than alignment along a neutral mechanical axis for 15-year survival.

We are not adverse to new technology. In fact, we want to harness the power of the computer for TKR, but in a way that improves efficiency, decreases costs, and avoids complications. One way to accomplish this is to move the computer part of computer-assisted surgery out of the operating room, take advantage of marked advances in 3-dimensional reconstruction technology, and generate patient-specific solutions, not generic average solutions that are encouraged by current navigation systems.

Moving the computer out of the operating room may save time, resources, and most importantly the mental energy to focus on balancing the soft tissues and not have to worry about driving a pin through the femur and puncturing the popliteal artery.

Navigation in 2008 remains a cumbersome, time-consuming, expensive tool with no proven clinical benefit. It is a valuable research tool, and we hope that it will help us define the right alignment and rotational targets for individual patients and groups of patients. For you and me as clinicians, however, the power of the computer likely lies outside the operating room.

References

  1. Bauwens K, Matthes G, Wich M, et al. Navigated total knee replacement. A meta-analysis. J Bone Joint Surg Am. 2007; 89(2):261-269.
  2. Ritter MA, Faris PM, Keating EM, Meding JB. Postoperative alignment of total knee replacement. Its effect on survival. Clin Orthop Relat Res. 1994; (299):153-156.
  3. Lotke PA, Ecker ML. Influence of positioning of prosthesis in total knee replacement. J Bone Joint Surg Am. 1977; 59(1):77-79.
  4. Bargren JH, Blaha JD, Freeman MA. Alignment in total knee arthroplasty. Correlated biomechanical and clinical observations. Clin Orthop Relat Res. 1983; (173):178-183.
  5. Hvid I, Nielsen S. Total condylar knee arthroplasty. Prosthetic component positioning and radiolucent lines. Acta Orthop Scand. 1984; 55(2):160-165.
  6. Rand JA, Coventry MB. Ten-year evaluation of geometric total knee arthroplasty. Clin Orthop Relat Res. 1988; (232):168-173.
  7. Jeffery RS, Morris RW, Denham RA. Coronal alignment after total knee replacement. J Bone Joint Surg Br. 1991; 73(5):709-714.
  8. Moreland JR. Mechanisms of failure in total knee arthroplasty. Clin Orthop Relat Res. 1988; (226):49-64.
  9. Parratte S, Pagnano MW, Trousdale RT, Berry DJ. The mechanical axis may be the wrong target in computer assisted TKA. Paper presented at: 75th Annual American Academy of Orthopaedic Surgeons Meeting; March 5-7, 2008; San Francisco, CA.

Authors

Drs Alden and Pagnano are from the Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota.

Dr Alden has no relevant financial relationships to disclose. Dr Pagnano receives royalties from DePuy and Zimmer. Institutional research support to Mayo Clinic is provided by Stryker, DePuy, and Zimmer.

“Orthopaedic Crossfire” is a registered trademark of A. Seth Greenwald, DPhil(Oxon).

Correspondence should be addressed to: Mark W. Pagnano, MD, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St SW, Rochester, MN 55944.