Orthosensor vs Conventional Total Knee Arthroplasty

In a randomized-controlled fashion, this investigation will evaluate the use of the Verasense technology to achieve optimal TKA balance. Patients will be randomized to either: 1) undergo manual soft tissue balancing or 2) soft tissue balancing with the Verasense. The primary outcomes of interest will include patient-reported outcomes as well knee range of motion at 3 months, 6 months, 1 year, and 2 years. Secondary outcomes of interest will include pain level as assessed by the visual analogue scale (VAS) in the acute post-operative and follow up periods, ambulation distance during inpatient physical therapy postoperatively, surgical time, tourniquet time, amount of opioid consumption, length of hospital stay, incidence of arthrofibrosis and subsequent manipulation under anesthesia. The investigators hypothesize that the use of the Verasense technology will lead to improved soft tissue balancing in TKA and ultimately result in favorable patient-reported outcomes and postoperative knee range of motion.

Total knee arthroplasty (TKA) is one of the most successful surgical procedures performed worldwide, and if conducted properly, has proven to improve pain, knee range of motion, and ultimately quality of life. Approximately 700,000 TKAs are performed annually in the United States, and this number is projected to increase to 3.48 million annually by 2030. Unfortunately, roughly 20% of patients who undergo TKA are dissatisfied with their outcome and this number has remained stagnant for the past decade.Patient satisfaction after TKA is predominantly driven by postoperative pain and function.

Outcomes in TKA are influenced by multiple factors, stemming from patient-specific factors and surgically modifiable factors. Patient specific factors include body mass index (BMI), preoperative range of motion (ROM), psychological status, and other comorbidities; examples of surgically modifiable factors include the type of prosthesis utilized, posterior condylar offset, posterior tibial slope, and soft tissue balancing. Knee arthritis is a disease not only of the condylar surfaces, but of the soft tissues as well. As such, the success of a TKA depends on the ultimate restoration of the integrity of the knee articular surfaces,necessitating two critical elements, beginning with precise osteotomies and ending with soft tissue balancing to realign the lower extremity to a neutral mechanical axis.

In the last three decades, this first element has been addressed by major technological advances to perform precise and reproducible osteotomies, most recently with the development of computer-assisted navigation and validation techniques and modalities that allow osteotomies based on anatomical jigs created by CT imaging of the patient's knee.

Despite these advances, little advancement has been appreciated by the second element-soft tissue balancing.While precise osteotomies are critical to the success of a TKA, they do not address ligamentous stability and balance, which if absent, leads to knee instability, stiffness, accelerated prosthetic wear, aseptic loosening, and premature implant failure. Soft tissue imbalance accounts for 35% of early TKA revisions in the United States. Soft tissue balancing in TKA has traditionally been more of an art than a science, relying exclusively on the surgeon's subjective assessment based on nebulous tactile feedback after completion of the osteotomies. The diseased soft tissues (i.e. ligaments) may be lengthened, tightened, or released to achieve balance, range of motion, and functional stability. However, these methods are numerous, variable, and above all, highly subjective. The individual experience of the surgeon, including fellowship training and procedural volume play a role in their ability to balance a knee properly.

Typically, it is only after many years of experience does the surgeon develop the ability to accurately assess stability in varus, valgus, anterior and posterior planes.Objective balancing of soft tissues in TKA may contribute to a decrease in pain, improve function, patient satisfaction, and ultimately decrease the rate of revision. The need for the transformation of TKA soft tissue balancing from an art to a science has been realized by a technology that allows surgeons to objectively quantify ligament balance by offering real-time, evidence-based data during TKA. The Verasense (Orthosensor Inc., Dania, FL) is a disposable wireless device embedded with force sensors and inserted into the tibial component during the trialing phase of surgery after gross balancing, allowing real-time loading values in the medial and lateral compartments of the knee and fine-tuning of the end result by further soft tissue releases to improve balance and stability.

Balance in TKA is defined as stability in the sagittal plane and less than 15 pounds difference in the medial and lateral compartments of the knee. In a multicenter study, intraoperative sensors were utilized to define balance and to correlate it with improved clinical outcomes. TKAs that had undergone said balancing were compared to unbalanced TKAs, with results showing improved Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) between balanced (172, 14.5 points) and unbalanced (145.3, 23.8 points), respectively. The authors concluded that a well-balanced TKA was the most significant contributing factor to improved postoperative outcomes.

Similarly, Chow et al. investigated six-month patient-reported outcomes in a small retrospective cohort study with short-term follow up of six months comparing sensor-assisted to non-sensor-assisted TKA balancing. They reported that the KSS, Oxford Knee Score, and knee range of motion was significantly higher in the sensor-assisted cohort and that the rate of arthrofibrosis was lower in the sensor-assisted group, however, not statistically significant.

Further, Geller et al. retrospectively compared the incidence of arthrofibrosis before and after the implementation of the Verasense technology to assist with ligament balancing and reported a 5% rate of arthrofibrosis prior to implementation versus 1.6% after. In this same report, median length of surgery was 83 minutes before implementation compared to 115 minutes after. The authors reported that while the implantation of the sensor increased operative time, this additional time does not have a clinical impact and that the benefits outweigh this potential increase in operative time. Multiple reports in the literature have suggested that a well-balanced TKA, which leads to increased activity levels may be part of a cascade effect, which ultimately results in higher patient-reported outcome scores.

Unfortunately, soft tissue balancing is one of the only remaining aspects of TKA that has not benefited from a consensus based on quantitative measures and objective data. As the economic environment changes in medicine, coupled with a five-fold increase in TKAs performed and the subsequent need for less experienced surgeons to perform TKAs, it is imperative that the traditional subjectivity once relied upon be replaced by more empirical and clinical data to construct a scientific consensus of what balance is. In so doing, clinical outcomes may be improved, with a resultant decrease in the rate of early revisions, and ultimately significant savings in healthcare expenditures.While the literature has demonstrated a clear advantage by technology like the Verasense, previous studies have predominantly been underpowered, with short-term follow up, and unstandardized TKAs, including surgical approach, prosthetic designs, manufacturer, and above all, not randomized and controlled.

Eligibility Criteria:
Inclusion Criteria:

* Primary total knee replacement

Exclusion Criteria:

* Revision knee surgery
* Prior knee surgery