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    Is There a Benefit to Using PSI in a Total Knee Arthroplasty?

    In a debate at ICJR’s Pan Pacific Orthopaedic Congress, Dr. Fred Cushner and Dr. Arlen Hanssen squared off on the issue of using patient-specific instrumentation to achieve better alignment in TKA.

    Patients undergo total knee arthroplasty (TKA) to relieve the pain of osteoarthritis and restore functioning of the affected knee. They expect their implant to be stable and problem-free over the long term. They do not expect to undergo the procedure again 6 months, 1 year, or even 5 years later to correct a surgical error.

    For the most part, this is not an issue. TKA is a generally successful procedure with a good track record for longevity of a properly aligned knee.

    And that’s the key: Restoring proper mechanical alignment is essential. A knee that is off the mechanical axis by even a few degrees is prone to failure.

    Patient-specific instrumentation (PSI) has been developed to address the issue of reliably inserting the implant components to achieve proper mechanical alignment and reduce failures. As with most technologies, however, the use of PSI is not without controversy. At the International Congress for Joint Reconstruction’s Pan Pacific Orthopaedic Congress, Fred D. Cushner, MD, and Arlen D. Hanssen, MD, debated the value of using PSI for TKA.

    Below are the abstracts from their presentations.

    Why Patient-Specific Instruments Are Ready for Prime Time
    Fred D. Cushner, MD, LIJ Orthopedic Institute, New York, New York

    It is no secret that as surgeons, we often miss the mark in regards to alignment at the time of TKA. In fact, misalignment has been cited as a primary cause of knee failures, and it has been estimated that 20-30% of the time, a neutral mechanical alignment is not achieved; it is off by more than 3º.

    The benefits of using patient-specific instruments to achieve alignment include the following:

    • Less blood loss
    • Less operative time
    • More accurate coronal alignment
    • Fewer surgical trays
    • Better rotational alignment
    • Ease of use in complex cases
    • Benefit in bilataeral TKAs
    • Retained hardware use
    • Complex previous fractures/nonunions

    While many ways to obtain computer guidance during the TKA procedure, the use of PSI remains a safe, reproducible, easy, and cost-effective method to obtain proper TKA alignment.

    Dr. Cushner’s presentation can be found here.

    Patient Specific Instrumentation Is Not the Future
    Arlen D. Hanssen, MD, Mayo Clinic, Rochester, Minnesota

    Increased interest in the use of patient-specific instrumentation (PSI) for total knee arthroplasty (TKA) has been primarily due to claims of increased radiographic accuracy, increased efficiency with lower operative times and lower cost, and improved clinical outcomes. The question remains, what evidence is there that that these goals have been achieved?

    • Radiographic accuracy. Of the 17 current studies in the literature, 11 have shown no difference in the radiographic alignment and outliers; 3 have shown differences of questionable clinical significance (ie. 1-2 degrees and < 10% difference in outliers), and in 3 studies, PSI was worse. Victor et al, in a Level 1 RCT found that there were more outliers in the PSI group (22%) and that 28% of patients in the PSI group required modification to the procedure.
    • Cost analysis. Barrack et al evaluated savings from decreased operative time and instrument processing costs compared with the additional cost of the MRI and PSI. While the cutting guides had significantly lower total operative time and instrument processing time, the estimated $322 savings was overwhelmed by an $1,500 additional cost of the MRI and the PSI cutting guide.
    • Clinical outcomes. There are no available data demonstrating improvement with the use of PSI.

    The only logical conclusion at this time is that PSI does not achieve its stated goals.

    Dr. Hanssen’s presentation can be found here.

    References

    • Barrack RL, Ruh EL, Williams BM, Ford AD, Foreman K, Nunley RM. Patient specific cutting blocks are currently of no proven value. J Bone Joint Surg Br. 2012 Nov;94(11 Suppl A):95-9.
    • Conteduca F, Iorio R, Mazza D, Caperna L, Bolle G, Argento G, Ferretti A. Are MRI-based, patient matched cutting jigs as accurate as the tibial guides? Int Orthop. 2012 Aug;36(8):1589-93.
    • Lustig S, Scholes CJ, Oussedik SI, Kinzel V, Coolican MR, Parker DA. Unsatisfactory accuracy as determined by computer navigation of VISIONAIRE patient-specific instrumentation for total knee arthroplasty. J Arthroplasty. 2013 Mar;28(3):469-73.
    • Nunley RM, Ellison BS, Ruh EL, Williams BM, Foreman K, Ford AD, Barrack RL.Are patient-specific cutting blocks cost-effective for total knee arthroplasty? Clin Orthop Relat Res. 2012 Mar;470(3):889-94.
    • 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.
    • 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.
    • 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.