Component position and overall limb alignment following total knee arthroplasty (TKA) have been shown to influence prosthetic survivorship and clinical outcomes. Robotic-assisted (RA) total knee arthroplasty has demonstrated improved accuracy to plan in cadaver studies compared to conventionally instrumented (manual) TKA, but less clinical evidence has been reported. The objective of this study was to compare the three-dimensional accuracy to plan of RATKA with manual TKA for overall limb alignment and component position. A non-randomized, prospective multi-center clinical study was conducted to compare RATKA and manual TKA at 4 U.S. centers between July 2016 and August 2018. Computed tomography (CT) scans obtained approximately 6 weeks post-operatively were analyzed using anatomical landmarks. Absolute deviation from surgical plans were defined as the absolute value of the difference between the CT measurements and surgeons’ operative plan for overall limb, femoral and tibial component mechanical varus/valgus alignment, tibial component posterior slope, and femoral component internal/external rotation. We tested the differences of absolute deviation from plan between manual and RATKA groups using stratified Wilcoxon tests, which controlled for study center and accounted for skewed distributions of the absolute values. Alpha was 0.05 two-sided. At the time of this abstract, data collections were completed for two centers (52 manual and 58 RATKA).Introduction
Methods
While TKA procedures have demonstrated clinical success, medial/lateral overhang of the femoral component in total knee arthroplasty (TKA) of ≥3mm may be associated with an increased risk of knee pain, and distal femoral size may vary across ethnic populations. The aim of this study was to determine and compare the prevalence of femoral component overhang among an inclusive (non-segmented) and Asian-identified (Asian-segmented) population, using a flexible intramedullary-rod, posterior referencing method. CT Scans from bilateral lower limbs of skeletally mature subjects (981 inclusive, 267 Asian-identified), without bone pathology were prospectively acquired. Bones were segmented and landmarks were modeled using a flexible intramedullary-rod, posterior referencing method. Femoral components were virtually positioned by aligning the lateral implant edge with the lateral bone edge, where the anterior flange meets the anterior chamfer. Medial and lateral component overhang was measured at three zones: (1) intersection of the anterior flange and anterior chamfer (medial only), (2) anterior chamfer mid-line, and (3) distal face mid-line. The central tendency of the samples was determined using the observed mean and median and the 95% confidence interval.Introduction
Methods
Restoration of a neutral mechanical axis has been a widely held tenet of primary total knee arthroplasty (TKA), however new technologies are recently being marketed which claim correction of alignment deformity is unimportant. This study was undertaken to determine whether the outcome of aseptic loosening was associated with post-operative mal-alignment of the mechanical axis. A 1:9 matched case-control analysis was conducted within a cohort of 1,030 consecutive cemented posterior stabilized TKAs with 7 to 11.5 yrs follow-up (average 9 yrs). Aseptic loosening had occurred in 10 knees (1.0%). Nine controls were randomly selected for each case within matching criteria for age and minimum time in situ. Post-operative mechanical alignment was determined using retrieved long leg radiographs. Age-adjusted relative risk was estimated using conditional logistic regression.Introduction
Methods
Restoration of physiologic rotational kinematics after total knee replacement has been difficult to achieve using modern dual M/L radius knee designs. This study was undertaken to determine whether a change in femoral shape substituting for the effect of the menisci in load sharing and motion accommodation would result in more normal rotational post arthroplasty kinematics. 17 knees reconstructed more than twelve months previously with a tricompartmental cemented knee replacement using a single F/E radius, miniscal substituting, a fixed bearing total knee were studied fluoroscopically while performing closed chain activities. The patients were studied during level gait, deep knee bending, rising from a chair, and kneeling. Images were converted from 2 to 3d and joint kinematics were measured using edge recognition softwear.Background
Methods
To determine the effect of altering tibial slope on the two-year range of motion (ROM) of patients undergoing condylar total knee replacements (TKR). A single surgeon performed 74 primary cemented posterior stabilised tri-compartmental TKR’s on 56 patients (19 male, 37 female) with mean age of 67.1 years, height 66.7in., weight 187.4 lb, and BMI 29.58 kg/m2. 51 had osteoarthritis, and five had rheumatoid arthritis. A standard surgical technique was employed utilising flexion axis localisation to position the femoral components. Patients were followed for two years minimum using outcome measures and x-rays. Knees where tibial slope was restored to a degree angle equal to, or slightly greater than, their pre-op slope (group 1) were compared to knees where tibial slope was decreased (group 2). The average 2 year post-op ROM in Group 1 was significantly greater than that of Group 2 (129.3 degrees vs. 120.5 degrees, p=.001). The average pre-op to post-op increase in ROM in Group 1 was significantly greater than Group 2 (38.1 degrees vs.27.7 degrees, p=.003). Correlational analysis revealed that restoration of pre-op tibial slope was the primary determinant of post-op ROM, followed by pre-op ROM, then weight and BMI (each to significance of p<
0.05). Restoration of tibial slope clearly produced increased ROM in this study. Using one standard slope cut for every tibia may prevent many patients from achieving their maximum potential ROM.
