Total Knee Replacement Using Patient-Specific Templates

Managed care leaders are striving to make evidence-based decisions about new and emerging health technology. Managed Care and ECRI Institute have collaborated to disseminate bimonthly summaries of the Institute’s Emerging Technology Evidence Reports. ECRI Institute is an independent not-for-profit organization that researches the best approaches to improving patient care by analyzing the research literature and data on clinical procedures, medical devices, and drug therapies.

Total knee replacement using commercially available patient-specific templates takes images from preoperative computed tomography (CT) or magnetic resonance imaging (MRI) scans to create single-use patient-specific templates intended to align knee implants.

Surgeons use one of two methods to align knee implants. Using the more widely accepted method, the surgeon aims to resect the bones in the proper orientation in all planes so that the implant aligns to the mechanical axis of the leg. Generally, up to a 3° deviation from the mechanical axis is accepted to minimize the risk of implant collapse, wear, loosening, instability, and postoperative pain. An alternative alignment method uses three kinematic axes to align the knee implants. This kinematic-based alignment method considers the relative relationships of the femur, patella, and tibia through all flexion angles without applied force. Regardless of method, suboptimal alignment has been associated with shortened implant longevity and poor patient outcomes.

Conventional instrumentation used during total knee replacement includes intramedullary and extramedullary guides to assist with proper orientation of femoral and tibial components. The use of conventional instrumentation has been reported to result in misalignment in approximately 28 percent of total knee replacements. Intraoperative computer-assisted navigation was developed to address alignment errors with conventional instrumentation. The use of intraoperative computer-assisted navigation has been reported to decrease the incidence of misalignment approximately threefold compared to conventional instrumentation.

Total knee replacement using patient-specific templates is an alternative to conventional and intraoperative computer-assisted approaches for patients who are able to undergo MRI or CT and wait several weeks for processing and creation of the templates. During the surgery, the surgeon places the patient-specific templates on the ends of the patient’s distal femur and proximal tibia and adjusts the position of the customized contact faces of each template until locating the exact fit to the bone. In some models, cutting guides within the templates specify where the surgeon should cut the bones, while other template models guide the insertion of pins, which then are used to place standard cutting guides. The surgeon creates the bone cuts, places the component replacement pieces, and uses cement to hold the pieces in place.

Purported benefits of using patient-specific templates during total knee replacement include the following:

• Improved alignment
• Decreased operative time
• Increased patient throughput
• Decreased instrumentation
• Reduced risk of fat embolism and intraoperative bleeding due to minimal bone removal (i.e., no intramedullary canal reaming)
• Decreased tissue loss
• Shorter recovery
• Reduced postoperative pain
• Decreased incidence of infection
• Lowered costs

Key questions and findings

1. Is the clinical efficacy (i.e., alignment, pain relief, stability, range of motion, function, quality of life, activities of daily living, durability, revision rate) of total knee replacement using patient-specific templates better than that of total knee replacement using conventional instrumentation or intraoperative computer-assisted navigation?

This question cannot be answered because of a lack of data on all but one outcome. A very small amount of low-quality data were available on range of motion of patient-specific templates compared to conventional instrumentation, but these data were insufficient to conclusively answer the question. No data were available to address the computer-assisted navigation comparison.

2. Are the perioperative outcomes (i.e., intraoperative blood loss, conversion to conventional total knee replacement, operative time, post-operative pain, length of stay) of total knee replacement using patient-specific templates equivalent to those of total knee replacement using conventional instrumentation or intraoperative computer-assisted navigation?

This question cannot be answered because of a lack of data on all but two outcomes. A very small amount of low-quality data were available on blood loss and operative time of patient-specific templates compared to conventional instrumentation, but these data were insufficient to conclusively answer the question. No data were available to address the computer-assisted navigation comparison.

3. How do the adverse events of total knee replacement using patient-specific templates compare to those of total knee replacement using conventional instrumentation or intraoperative computer-assisted navigation?

This question cannot be answered because of the very small amount of low-quality data available on adverse events of patient-specific templates compared to conventional instrumentation. No data were available to address the computer-assisted navigation comparison.

4. What adverse events are reported for total knee replacement using patient-specific templates?

Two small studies that looked at adverse events during use of patient-specific templates reported that no adverse events occurred.

Coverage and payment

The U.S. Centers for Medicare & Medicaid Services (CMS) has no national coverage determination regarding use of patient-specific templates during total knee replacement. Thus, coverage decisions are left to the discretion of local Medicare carriers.

ECRI Institute routinely searches 11 major private, third-party payers that publish their policies online. Our searches found one major payer with a policy that denies coverage for patient-specific templates and 10 without a specific policy.

Excerpted with permission from ECRI Institute’s database of Emerging Technology Evidence Reports. To download the full report, visit www.ecri.org/managedcare [1].

For inquiries about this report or membership in ECRI Institute’s Health Technology Assessment Information Service, e-mail htais@ecri.org [2].