A Randomized Prospective Pilot Trial Comparing Clinical and Economical Benefits of Patient Specific Instruments in Total Knee Replacement

Purpose Arthritis is the most common chronic illness in the United States. TKR provides reliable pain relief and improved function for patients with advanced knee arthritis. Total joint replacement now represents the greatest expense in the national healthcare budget. Surgical costs are driven by two key components: fixed and variable costs. Patient Specific Instruments™ (PSI, Zimmer, Warsaw, IN, USA) has the potential to reduce both fixed and variable costs by shortening operative time and reducing surgical instrumentation. However, PSI requires the added costs of pre-operative MRI scanning and fabrication of custom pin guides. Previous studies have shown reduction in operating room times and required instrumentation, but question the cost-effectiveness of the technology. Also, these studies failed to show improvement in coronal alignment, but call for additional studies to determine any improvement in clinical function and patient satisfaction. Our pilot study aims to compare the incremental PSI costs to fixed and variable OR cost savings, and compare meaningful patient and clinical outcomes between PSI and standard TKR surgeries. Methods This IRB approved, prospective, randomized pilot trial involves 20 TKR patients. Inclusion criteria includes: diagnosis of osteoarthritis, ability to undergo MRI, and consent for primary TKR. Following informed consent, patients are randomized to PSI or standard TKR. Patients randomized to PSI undergo pre-operative non-contrast MRI of the affected knee at least 4 weeks prior to surgery. Custom pin guides are prototyped from 3D pre-operative planning software customizable to individual surgeon and patient. All surgeries will be completed by a single surgeon (DA), using a medial parapatellar arthrotomy and Zimmer Nexgen™ implants. Surgical technique for PSI patients utilizes custom pin guides to determine placement of the femoral and tibial cutting guides, whereas an intramedullary femoral rod and extramedullary tibial guide are used in standard TKR patients. Our pilot study will compare numerous intra-operative and post-operative variables between the two patient cohorts. Intra-operative variables include: bony cutting time, tourniquet time, total OR time, surgical instrumentation, and bony resection height. Post-operative variables include: instrument processing and sterilization, blood transfusion, pain medication usage, length of stay, complications (including hospital readmission), and patient reported outcomes (SF-36, WOMAC, and satisfaction) at 4 weeks, 6 months, and 1 year. Additional economic sensitivity analyses using hospital and national cost-to-charge figures will quantify the potential added revenue or costs of implementing the PSI system. Discussion This pilot study will illustrate the potential benefits of the PSI technology. To our knowledge no clinical trials have been published on the PSI system. Former studies have neglected to include meaningful clinical and patient outcomes, which could potentially add to the cost savings of the technology through reduced blood transfusions, length of stay, and hospital readmission. Additionally, improved rotational alignment may produce superior patient function and satisfaction. Studies recently published on alternative patient-specific TKR systems question the cost-effectiveness and technical improvement of patient-specific instrumentation. Although our sample size may fail to produce statistical significance, the consummate measurement of all the proposed hospital, surgical, and patient factors will inform future randomized multicenter trials.