Abstract
Introduction
Proper soft-tissue balance is important for achieving favorable clinical outcomes following TKA, as ligament imbalance can lead to pain, stiffness or instability, accelerated polyethylene wear, and premature failure of implants. Until recently, soft-tissue balancing was accomplished by subjective surgeon feel and by use of static spacer blocks. Now, nanonsensor-embedded implant trials allow surgeons to quantify peak load and center of load in the medial and lateral compartments during the procedure, and to adjust ligament tension and implant positioning accordingly. The purpose of this 3-year, multicenter study is to evaluate 500 patients who have received primary TKA with the use of intraoperative sensors in order to correlate quantified ligament balance to clinical outcomes.
Methods
To date, 7 centers have contributed 215 patients who have undergone primary TKA with the use of intraoperative sensors. Patients are seen at a pre-operative visit (within 3 months prior to surgery), and post-operatively at 6 weeks, 6 months, and at 1, 2, and 3-year anniversaries. Standard demographic and surgical data is collected for each patient, including: age at time of surgery, BMI, operative side, gender, race, and primary diagnosis. At each interval, anatomic alignment and range of motion are assessed; KSS and WOMAC evaluations are administered; and a set of standard radiographs is collected, including: standing anteroposterior, standing-lateral, and the sunrise patellar view. Intraoperative loads were recorded for pre- and post-release joint states. All soft-tissue release techniques were recorded. “Optimal” soft-tissue balance was defined as a medial-lateral load difference of less than or equal to 15 lbs.
Results
The average age of this cohort was 70 years: 63% are female and 37% are male, with a mean BMI of 30.6. Ninety five percent of cases had a primary diagnosis of osteoarthritis. The majority of cases (72.5%) exhibited suboptimal soft-tissue balance (>15 lbs. of medial-lateral compartmental loading difference) prior to ligamentous release. Using the intraoperative sensor for guidance, 82% (p < .01) of patients were released and confirmed to exhibit a state of optimal joint balance at closure. Patient self-reported outcome scores—both KSS and WOMAC—showed significant improvement (p < .01) from the pre-operative interval to the 6-month follow-up interval. The average increase for KSS at 6 months was 60 points.
Discussion
Optimized ligament balance using intraoperative sensors led to significant improvement in KSS and WOMAC scores at a 6-month follow-up interval in 215 knees. Notably, the 60-point average increase in KSS, at 6 months, is approximately 200% greater than historical data, obtained from existing literature, using traditional methods of TKA balancing. Measuring the effect of specific ligamentous releases on subsequent load and balance can potentially enable the development of release algorithms to guide surgeons to balance TKA using sensor data. Further, correlating quantifiable data on peak load and center of load to patient outcomes will help clarify what truly defines “optimum balance.” Additional study subject accrual and further longitudinal follow-up is needed to affirm the early observation that sensor-quantified soft-tissue balancing improves patient outcomes in TKA.
