Abstract
Introduction
Aseptic loosening has been reported to be the most common, contemporary mode of total knee arthroplasty failure. It has been suggested that the etiology of revision due to loosening can be attributed, in part, to joint imbalance and the variability inherent in standard surgical techniques. Due to the high prevalence of revision, the purpose of this study was to quantify the change in kinetic loading of the knee joint before versus after the application of the final cement-component complex.
Methods
Ninety-two consecutive, cruciate-retaining TKAs were performed, between March 2014 and June 2014, by two collaborating surgeons. Two different knee systems were used, each with a different viscosity cement type (either medium viscosity or high viscosity). All knees were initially balanced using a microelectronic tibial insert, which provides real-time feedback of femoral contact points and joint kinetics. After the post-balance loads were captured, and the surgeon was satisfied with joint balance, the final components were cemented into place, and the sensor was re-inserted to capture any change in loading due to cementing technique.
Results
Of the 92 TKAs performed, 42% of patients required post-cement correction due to changes in loading. Of the entire cohort, 41% of patients were also classified as “imbalanced”, post-cementing, as defined previously in literature. The average absolute value of the post-cementing change to intercompartmental loading was 28.2 lbs. (±24.8 lbs.). Of those patients with excessive changes to joint loading, 84.2% exhibited the majority of change to loading in the medial compartment, which is theorized to be due to the right-handedness of both surgeons and angle of impaction. There was a highly statistically significant relationship between post-cementation loading changes and proportion of imbalance (P <0.001). There was no significant difference in average loading values, or occurrence of imbalance, between either component systems or cement types.
Discussion
Joint imbalance and loosening substantially contribute to the current 2.7 billion dollar TKA revision burden in the United States. The post-cementing imbalance, as detected by the sensor in this study, demonstrates how using quantified methods in TKA may mitigate imbalance-related complications. By using technology to guide the surgeon through appropriate kinetic correction, the subtleties in imbalance, despite a symmetrical flexion gap, can be corrected for more effectively than by subjective surgeon “feel.” Longer clinical follow-up of these patients will be necessary to track the outcomes associated with quantifiably balanced joint loading.
