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Adolph V. Lombardi Jr., MD, FACS

AAOS Now

Published 7/1/2014
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Mary Ann Porucznik

Pros and Cons of Patient-Specific Instrumentation

Is it the way of the future or just one way?

During the 2014 Specialty Day of The Knee Society and the American Association of Hip and Knee Surgeons (AAHKS), Adolph V. Lombardi Jr., MD, FACS, and Robert L. Barrack, MD, faced off in a debate over the future of patient-specific instrumentation (PSI) in total knee arthroplasty (TKA).

PSI systems enable orthopaedic surgeons to template the TKA preoperatively using 3-dimensional imaging. Custom-made and custom-fit jigs are used during the surgery so that the implant can be precisely fitted.

It’s the way to go
Taking the affirmative, Dr. Lombardi, a partner at Joint Implant Surgeons, Inc., in New Albany, Ohio, began by noting the two-decade history of PSI. “It is based on proven technology—rapid prototyping technology—which those of us who perform complex joint replacement procedures have used to create three-dimensional models and custom components,” he said. “Ample literature shows that the technology delivers good results.”

Dr. Lombardi pointed out that every major orthopaedic implant manufacturer offers a version of PSI. The technology can be used in several types of surgeries—from unicompartmental knee replacement to total hip replacement, total shoulder replacement, total ankle replacement, and osteotomy alignment correction. “PSI has even been used successfully in revision arthroplasty,” he said.

In today’s healthcare environment, with its emphasis on reducing expenses, PSI fits, insisted Dr. Lombardi. “PSI does not require an initial capital expenditure; you don’t have to buy a fancy computer. It facilitates preoperative planning; most systems offer an interactive program that enables the surgeon to plan and think about the operation before entering the operating room (OR). PSI easily fits into the surgical workflow; most timed studies show that its usage actually decreases operative time.”

He cited studies that show significant reductions in processing and sterilization times, OR turnover times, hospital length of stay, OR time, and number of trays used. Because PSI requires less instrumentation, he noted, OR set up and breakdown times are faster.

“PSI does not require a considerable learning curve,” said Dr. Lombardi. “It’s very intuitive. You can look at the models, you can look at the patient, and you can go back and forth to determine accurate placement of these devices.”

PSI benefits surgeons in other ways as well. “PSI is extremely useful in patients with extra-articular deformity or retained hardware,” said Dr. Lombardi. “And PSI offers a distinct advantage to lower-volume surgeons, by reducing the number of instruments and improving efficiency.”

Plus, said Dr. Lombardi, PSI is attractive to patients. “They like the idea; they want a personalized patient-care approach.” Outcome data also support the use of PSI; PSI has been reported to be associated with significant improvement in Knee Society functional scores in short-term follow-up.

Finally, noted Dr. Lombardi, “PSI is part of the future delivery of implants.” PSI technology is in a state of constant evolution; although current technology is based on preoperative CT/MRI scans, he foresees a day when preoperative radiographs will be sufficient to make PSI guides.

“Combining patient-specific guides with single-use instruments streamlines the delivery of orthopaedic products, increases efficiency, decreases the number of instruments required, and leads to reductions in OR set-up time, OR turnover time, and overall surgical time. This is the wave of the future,” he concluded.

It’s not there yet
For his part, Dr. Barrack noted that he used PSI for about 3 years, but no longer offers it, based on his experiences with the technology. He outlined the following three goals of a patient-specific approach:

  • to increase radiographic accuracy (coronal plane alignment) and minimize outliers
  • to increase efficiency, reduce surgical times, and lower costs
  • to improve clinical outcomes
Adolph V. Lombardi Jr., MD, FACS
Robert L. Barrack, MD

“I agree with Dr. Lombardi,” said Dr. Barrack. “Patients love it; it was not a hard sell. But what is the evidence that PSI achieves those three goals?”

Based on his personal experience with about 200 TKAs performed using PSI, Dr. Barrack found no difference in the incidence of radiographic outliers in any measure of coronal alignment. The target (neutral alignment within 3 degrees) was achieved about 80 percent of the time, regardless of the technology used (PSI or standard).

He also noted that Level 1 studies published by top researchers in the field also found more outliers in the PSI group. In one study on PSI, the technology was abandoned in 22 percent of cases and modified in another 28 percent, “so it really didn’t help them,” Dr. Barrack said.

He also reviewed the current literature comparing PSI and standard technology. Of 17 studies, 11 reported no difference in radiographic alignment or outliers, three showed “differences of questionable clinical significance,” and three showed notably worse results with PSI than with standard technology.

As for efficiency, said Dr. Barrack, “It depends on how you count the numbers. We found that our hospital saves about $300 in processing costs but the guides cost almost $1,000 and the MRI costs almost $1,000. The net cost to the system was about $2,000.

“Patient acceptance was high, but we concluded that the cost/benefit is hard to justify if you don’t have a clinical advantage,” he noted. And improved alignment doesn’t necessarily impart a clinical advantage; “if you’re within 3 or 4 degrees, there’s no difference in either revision rate or satisfaction,” said Dr. Barrack.

“The big difference that we saw,” he continued, “is data that suggest that patients whose TKAs were kinematically aligned (in other words, leaving a varus knee a little varus and a valgus knee a little valgus) felt that their knee replacements were more normal and they had less pain. A lot of data suggest that a mechanical axis is not the ideal target for all patients.”

Dr. Barrack noted that approximately one third of the normal population have a true neutral mechanical alignment. “I think the reason many patients may not feel ‘normal’ after a knee replacement is that we’re changing the rotation. When we try to align all knees the same, we’re really changing rotation dramatically. In this case, ‘custom’ is a misnomer. By aligning all knees the same, we malrotate a high percentage.”

For these reasons, he concluded, “current data do not support an advantage for the current generation of PSI cutting guides in their current form, which is neutral mechanical alignment. Strong evidence is emerging that needs validation, but the ideal alignment target for all patients may not be the same, and we probably should be considering different alignments. Variants such as constitutional varus are relatively common. When PSI technology enables us to make truly patient-specific alignment, we and our patients may realize benefits.”

Disclosure information: Dr. Lombardi—Biomet, Innomed, Pacira, Kinamed, Stryker, Clinical Orthopaedics and Related Research, Journal of Arthroplasty, Journal of Bone and Joint Surgery, Journal of Orthopaedics and Traumatology, Journal of the American Academy of Orthopaedic Surgeons, Knee, Surgical Technology International, Hip Society, Knee Society, Mount Carmel Education Center at New Albany, Operation Walk USA. Dr. Barrack—Stryker, Biomet, Medical Compression Systems, National Institutes of Health, Smith & Nephew, Wright Medical Technology, Inc., The McGraw-Hill Companies, Inc., Wolters Kluwer Health - Lippincott Williams & Wilkins, Journal of Bone and Joint Surgery, Hip Society, Knee Society.

Mary Ann Porucznik is managing editor, AAOS Now. She can be reached at porucznik@aaos.org

Specialty Day Debates
This month, AAOS Now presents several debates on controversial issues presented during the 2014 Specialty Day.

References:

  1. Victor J, Premanathan A. Virtual 3D planning and patient specific surgical guides for osteotomies around the knee: a feasibility and proof-of-concept study. Bone Joint J. 2013 Nov;95-B(11 Suppl A):153-158.
  2. Kerens B, Boonen B, Schotanus M, Kort N. Patient-specific guide for revision of medial unicondylar knee arthroplasty to total knee arthroplasty: beneficial first results of a new operating technique performed on 10 patients.  Acta Orthop. 2013 Apr;84(2):165-9.
  3. Johnson DR. The benefits of customized patient instrumentation to lower-volume joint replacement surgeons: Results from practice. Amer Journal Orthopedics. 2011 Nov;40(11 Suppl):13-16.
  4. Mont MA, McElroy MJ, Johnson AJ, Pivec R, Single-Use Multicenter Trial Group Writing Group. Single-use instruments, cutting blocks, and trials increase efficiency in the operating room during total knee arthroplasty: a prospective comparison of navigated and non-navigated cases. J Arthroplasty. 2013 Aug;28(7):1135-40.
  5. Nunley RM, Ellison BS, Zhu J, Ruh EL, Howell SM, Barrack RL. Do patient-specific guides improve coronal alignment in total knee arthroplasty? Clin Orthop Relat Res. 2012 Mar;470(3):895-902.
  6. Victor J, Dujardin J, Vandenneucker H, Arnout N, Bellemans J. Patient-specific guides do not improve accuracy in total knee arthroplasty: a prospective randomized controlled trial. Clin Orthop Relat Res. 2014 Jan;472(1):263-71.
  7. Lustig S, Scholes CJ, Oussedik S, Coolican MR, Parker DA. Unsatisfactory accuracy with VISIONAIRE patient-specific cutting jigs for total knee arthroplasty. J Arthroplasty. 2014 Jan;29(1):249-50.
  8. Woolson ST, Harris AH, Wagner DW, Giori NJ. Component alignment during total knee arthroplasty with use of standard or custom instrumentation: a randomized clinical trial using computed tomography for postoperative alignment measurement. J Bone Joint Surg Am. 2014 Mar 5;96(5):366-72.