**3. Design and rationale**

There are a number of ways surgeons can address surgical techniques to help improve efficiency, including, but not limited to, patient-specific instrumentation, navigation assistance, and type of implant. A universal knee system is one way to help improve efficiency and reduce operating room costs. This system optimizes efficiency in a number of ways, one of which involves the implant design itself, which allows the surgeon to utilize the same system for the majority of primary TKA, but also allows the flexibility to progress from a cruciate-retaining primary TKA to a maximally stabilized revision TKA with the same family of instrumentation.

The femur is designed with a specific trochlear groove to accommodate patellar tracking for both left and right knee anatomy. This trochlear groove design is based on the quadriceps, or Q-angle, which describes the vector of the pull of the quadriceps on the patella and is fashioned so that its angle allows for optimal tracking for both left and right knees. Moreover, the universal knee system femur is designed to be compatible with a variety of polyethylene inserts, such as cruciate-retaining (CR); posterior cruciate ligament (PCL) sacrificing (PS) in both a posted posteriorstabilized, or ultra-congruent (UC), with a raised anterior lip for cruciate stabilization; and a varus/valgus constrained; polyethylene inserts, offering a full evolution of stability with one implant and instrumentation system. This alone significantly reduces the number of instruments and implants that must be shipped, sterilized, and stored at the hospital or surgical center. Because the system was designed holistically, cuts, peg locations, and trialing are standardized throughout the workflow, eliminating time-consuming steps when alternative sizing or additional stability is required. For example, a more constrained femoral trial can be utilized before making any further cuts to assess the need for a more constrained polyethylene insert.

The symmetrical tibial baseplate is optimized to fit both right and left proximal tibias using a potbellied design. Throughout development, design surgeons traced native tibial resections during routine TKA, and this gradual anterior bump optimizes fit in most patient anatomy. A plethora of studies have examined the universal tibial design, which suggests there is improved tibial coverage, improved external rotation, and decreased risk for overstuffing components [20, 21]. Additionally, consistent polyethylene thickness to the peripheral edges and matching conforming geometry of the baseplate and polyethylene insert optimize congruency, offering exceptional mid-flexion stability [19]. All baseplates, whether cemented or cementless, offer modularity so that they can accommodate a stem extension in either a primary or revision setting. Studies have shown that stemmed tibial components offer enhanced fixation and additional stability, and improve outcomes in heavier patients [22, 23].

In addition to the components, the instruments and number of trays utilized during the case can also significantly affect efficiency and cost. A majority of the instruments in the tray have multiple functions and are utilized at different times throughout the case. This universal knee system design allows up to 90% of cases, regardless of a workflow (e.g., gap balancing or measured resection technique), to be completed with a single tray of instruments; revision cases require one or two additional trays depending on the level of stability needed (**Figure 2**).

This significant optimization in the number of required instrumentation results in a reduced amount of inventory needed for a TKA which can help improve surgeon and hospital efficiency as well as reduce costs. A recent Harvard Business School study demonstrated that hospitals often underestimate the costs of idle space and equipment resulting in errors in utilization [24].

By reducing the number of trays, studies have also demonstrated that surgeons are able to reduce OR time and sterilization costs, the incidence of infection as well as optimize efficiency and ergonomics [25, 26]. Fewer instrument trays require less time to set up and break down and need less space and time to sterilize. Moreover, with respect to cleaning and sterilization, fewer instruments mean that there is less total exposed instrumentation surface area that is susceptible to contamination. Additional studies have also confirmed that the decreased inventory and instrumentation do not adversely affect patient outcomes but may actually improve them [26].

Studies in Europe have analyzed the cost of sterilizing and packaging reusable instruments somewhere between \$0.59 and \$11.52 (USD) per surgical instrument [27–29]. If a surgeon is able to reduce the number of instrument trays the savings could be huge, with one study looking at a reduction from 7.5 trays in a TKA to three trays. This reduction led to an estimated annual savings of \$159,600 in sterilization costs and \$99,000 in improved turnover times [30]. Each tray costs between \$60 and \$150 dollars to sterilize, and each tray averages 2 minutes to open onto the

#### **Figure 2.**

*With a modern universal total knee system, a single standard instrument tray may be used for up to 90% of primary total knee arthroplasty while following AORN guidelines to weigh less than 25 lbs. A second tray is offered for micro/macro trials, allowing a primary TKA to be performed with two trays or fewer 10% of the time. TJO's Klassic ONE® Knee System single instrumentation tray is featured as an example here.*

sterile field; some systems have estimated a cost savings of up to \$1350 per case compared to a typical eight tray implant system [1, 25, 26, 31, 32]. As a result, there is a significant opportunity to improve value through reducing and making hospital inventory more efficient.
