Background
Computer navigation and robotic assistance technologies are used to improve the accuracy of component positioning in total knee arthroplasty (TKA), with the goal of improving function and optimizing implant longevity. The purpose of this study was to analyze trends in the use of technology-assisted TKA, identify factors associated with the use of these technologies, and describe potential drivers of cost.
Methods
The Nationwide Inpatient Sample database was used to identify patients who underwent TKA using conventional instrumentation, computer navigation, and robot-assisted techniques between 2005 and 2014. Variables analyzed include patient demographics, hospital and payer types, and hospital charges. Descriptive statistics were used to describe trends. Univariate and multivariate analyses were performed to identify differences between conventional and technology-assisted groups.
Results
Our analysis identified 6,060,901 patients who underwent TKA from 2005 to 2014, of which 273,922 (4.5%) used computer navigation and 24,084 (0.4%) used robotic assistance. The proportion of technology-assisted TKAs steadily increased over the study period, from 1.2% in 2005 to 7.0% in 2014. Computer navigation increased in use from 1.2% in 2005 to 6.3% in 2014. Computer navigation was more likely to be used in the Western United States, whereas robot-assisted TKAs were more likely to be performed in the Northeast. Increased hospital charges were associated with the use of technology assistance ($53,740.1 vs $47,639.2).
Conclusions
The use of computer navigation and robot-assisted TKA steadily increased over the study period, accounting for 7.0% of TKAs performed in the United States in 2014. Marked regional differences in the use of these technologies were identified. The use of these technologies was associated with increased hospital charges.
The purpose of this study was to measure the effects of variation in placement of the femoral tunnel upon knee laxity, graft pretension required to restore normal anterior-posterior (AP) laxity and graft forces following anterior cruciate ligament (ACL) reconstruction. Two variants in tunnel position were studied: (1) AP position along the medial border of the lateral femoral condyle (at a standard 1 1 o'clock notch orientation) and (2) orientation along the arc of the femoral notch (o'clock position) at a fixed distance of 6--7 mm anterior to the posterior wall. AP laxity and forces in the native ACL were measured in fresh frozen cadaveric knee specimens during passive knee flexion-extension under the following modes of tibial loading: no external tibial force, anterior tibial force, varus--valgus moment, and internal-external tibial torque. One group (15 specimens) was used to determine effects of AP tunnel placement, while a second group (14 specimens) was used to study variations in o'clock position of the femoral tunnel within the femoral notch. A bone-patellar tendon-bone graft was placed into a femoral tunnel centered at a point 6-7 nim anterior to the posterior wall at the 11 o'clock position in the femoral notch. A graft pretension was determined such that AP laxity of the knee at 30 deg of flexion was restored to within 1 mm of normal; this was termed the laxity match pretension. All tests were repeated with a graft in the standard 1 I o'clock tunnel, and then with a graft in tunnels placed at other selected positions. Varying placement of the femoral tunnel 1 h clockwise or counterclockwise from the 1 I o'clock position did not significantly affect any biomechanical parameter measured in this study, nor did placing the graft 2.5 mm posteriorly within the standard l l o'clock femoral tunnel. Placing the graft in a tunnel 5.0 mm anterior to the standard 1 1 o'clock tunnel increased the mean laxity match pretension by 16.8 N (62%) and produced a knee which was on average 1.7 mm more lax than normal at 10 deg of flexion and 4.2 mm less lax at 90 deg. During passive knee flexion-extension testing, mean graft forces with the 5.0 mm anterior tunnel were significantly higher than corresponding means with the standard 11 o'clock tunnel between 40 and 90 deg of flexion for all modes of constant tibial loading. These results indicate that AP positioning of the femoral tunnel at the 1 1 o'clock position is more critical than o'clock positioning in terms of restoring normal levels of graft force and knee laxity profiles at the time of ACL reconstruction.
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