August 27, 2012
4 min read

Technology can make a difference in outcomes for most arthroplasty Luddites

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The last 20 years of surgical high technology have not delivered on their initial promise — the Luddite artisan surgeon has delivered equivalent outcomes with simple tools.

Arthroplasty should provide an excellent functional outcome with a lifetime guarantee for our patients. All artisan trades use high-tech assistance, so arthroplasty surgeons should obviously do likewise. Using high-tech assistance, they should offer a better outcome, while the artisan surgeon whose manual skills are all that he or she uses should be consigned to the past.

But is this is true today? Should today’s surgeons embrace what the technology can offer, or wait for the next wave?

Justin P. Cobb 

Justin P. Cobb

Active robotics

From its first use in humans in the early 1990s, active robotics was compelling. RoboDoc (Curexo Technology Corp.; Fremont, Calif., USA) and CASPAR (Orto Maquet GmbH & Co KG; Rastatt, Germany) were going to sweep all before them, with high-tech CT-based hip replacements. The active robotic program fell down for two reasons: the wrong operation and the wrong implementation.

Firstly, they chose hip replacement as their index operation. The entire robotic device was centered around machining a cavity precisely for a press-fit femoral stem. Secondly, they failed to appreciate that femoral rasps do not act in the same way as a high-speed milling tool. By extracting a volume of bone precisely, the robots did not perform the same task as the surgeon who was effectively impaction grafting the edge of the cavity. The robotic cavity, while precisely milled, did not offer the same interference fit as a conventionally rasped femur. This simple error meant that robot-reamed femurs sometimes subsided more than conventionally prepared ones.

This information, coupled with the fact that orthopaedic surgeons are rather good at hammering a square peg into a round hole, undermined the entire “robotic surgery’ program. The active robots were performing a task very well, but not exactly the right task, and certainly not a task that surgeons were incapable of performing themselves with a fair degree of success.

Image-free navigation

Image-free navigation was the first major wave of marketing-based technology sales and the “Brainlab effect” happened to most major implant manufacturers. They would place an expensive tool in the operating theatres, and expect surgeons to perform more operations using more high-priced devices with the marketing hype that the technology would deliver more accurate and therefore better surgery.

This wave of surgical technologies also failed to reach prime time for similar reasons. The index operation for navigation systems was total knee arthroplasty (TKA). This operation is much less successful than total hip arthroplasty, and the theory was that by doing the procedure accurately, success rates would increase. Wrong again. While the operation is performed more accurately with this technology, the aim of “zero degrees” mechanical axis for all patients had not been validated before the surgeons set out to correct worldwide deformity to this apparently desirable state.

Improving TKA

The result of restoring every patient to a mechanical axis of zero via TKA has not meant that all patients are better for the simple reason that all varus patients are a bit happier being left a little varus. At the same time, even accurately planned and precisely performed TKA can still be unsatisfactory: the stability of the joint, its kinematics, and range of motion are far from a normal joint. So while the whole navigation experience globally has seen an increase in standards of care, there is a realization at the same time that the TKA procedure itself has shortcomings that navigation technology alone cannot overcome.

The Da Vinci surgery robot (Intuitive Surgical; Sunnyvale, Calif., USA) is a master/slave robotic system that has been astonishingly successful globally. By its very presence in a hospital, patients feel better and succumb to the allure of robotic precision and are reassured by the huge cost incurred. Mako Surgical Corp. set out on the same track, but with a procedure that would benefit from the technology – unicompartmental knee replacement (UKR).

UKR is a technically unforgiving procedure, so it made sense to pay extra for accuracy with it instead of TKA. The surgeons who used the Mako system had learned from the Acrobot experience that with a UKR there is no need to correct to “zero degrees,” and that accuracy improves outcomes in the long term.

For the first time, the technology really makes a difference. However, there is competition. Do you really need a million dollar robot to perform a unicompartmental knee replacement? The Sculptor RGA (Stanmore Implants; Elstree, United Kingdom) offers a similar robot for a fraction of the price. This active constraint robotic system allows the surgeon to achieve levels of accuracy that still make a significant clinical difference after 7 years.

Only two things are required from surgical technology: a precise plan of surgery, including the size of the devices needed and exactly where they should go, and a timely and cost-effective way of carrying out the plan. In 2012 as a profession, we all know more about what needs to be done in a way that we simply did not in the last century. The 3-D analysis of joint disease is cheap and available, and the ability to place a prosthesis into that 3-D model in the computer, first offered by HipNav (Carnegie Mellon University; Pittsburgh, USA), RoboDoc, and Acrobot in the 1990s, is now offered by every major implant manufacturer.

What has transformed the horizon is the advent of the 3-D printer – a technology that allows surgeons to achieve the plan faster than with conventional surgery and at reduced cost because of reduced instrumentation and inventory. So it may be both cheaper and quicker, but what remains to be seen, however, is whether the reliability matches the robots. This isn’t the end of the artisan. This technology can be used by Luddites. It simply makes them better surgeons.

For more information:
  • Justin P. Cobb, MD, is Chair, Section of Orthopaedics, Imperial College London. He can be reached at Room 7L25, Floor 7, Laboratory Block, St. Dunstan’s Road, Charing Cross Campus, London, W6 8RP, United Kingdom; email:
  • Disclosure: Cobb is a shareholder in and receives royalty payments from Stanmore Implants. He is a paid consultant to MatOrtho, and received grant support from CeramTec, DePuy and Biomet.