Abstract
INTRODUCTION
The cost associated with the TKA revision burden is projected to reach 13 billion dollars, annually. Complications reported by post-TKA patients include: pain (44%, multilocational), sensation of instability (21% reason for revision), and joint stiffness (17% reason for revision); problems that may be attributed to soft-tissue imbalance. One of the possible reasons for the substantial prevalence of such complications is the subjectivity associated with defining soft-tissue balance. A priority must be placed on developing new objective methods with which to avoid costly post-operative complications, including the integration of intraoperative sensing technology. The purpose of this evaluation was to report on the disparity between the patient-reported outcomes scores of quantitatively balanced versus unbalanced patients, at 1-year, using a group of 135 multicenter patients.
METHODS
135 prospective patients, from 8 U.S. sites, have had primary TKA performed with the use of intraoperative sensors. Patients were classified by two groups: “balanced” and “unbalanced”. Quantitative “balance” was defined as a mediolateral intercompartmental loading difference of ≤ 15 pounds; all loading exceeding 15 pounds was classified as “unbalanced”. For all patients, the following kinematic data was captured: varus/valgus stability, anteroposterior stability, flexion contracture (if any), extension lag (if any), anatomic alignment, and ROM. Also at each clinical follow-up visit, activity levels and two patient-reported outcomes measures were administered, including: the American Knee Society Score (KSS), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).
RESULTS
Of the 135 patients with sensor-assisted surgery, 13% were unbalanced. Pre-operatively, via ANOVA analyses, there was also no statistical difference in alignment, ROM, outcomes measures, or demographic data between the two groups. At one year post-operatively, the average total KSS score of balanced patients exceeded that of unbalanced patients by 23.3 points (P<0.001). The balanced group averaged 8 points more improvement in WOMAC scores than the unbalanced group. The balanced group's average activity level score was 48.6, which corresponds with the light to moderate labor categories. The unbalanced patient's average activity level score was 26.7, which corresponds to the upper limits of the semi-sedentary range (P=0.015). The regression model revealed that the variable exhibiting the most significant effect of improvement on KSS and WOMAC score was balanced joint state (p=0.001; p=0.014). Joint state was the most highly significant variable when analyzed independently, as well as with every other possible combination of variables included in the model (p=0.001).
DISCUSSION
In this evaluation, the efficacy of using intraoperative sensing technology to verify ligament balance was assessed. At 1-year post-operatively, the KSS, WOMAC, and activity level scores of balanced patients surpassed those of the unbalanced patients by 23.2, 8, and 22 points, respectively (P=0.001, P=0.085, P=0.015). This suggests that verifiably balanced patients not only obtain statistically significant improvement in both pain and function levels versus unbalanced patients, but that they do so in a shorter amount of time than their unbalanced counterparts. Evidence from this evaluation suggests that sensor-guided, quantifiably balanced TKA patients are statistically more likely to achieve reduced pain, improved function, and greater activity levels sooner than unbalanced patients.
