Restricted kinematic alignment achieves similar relative lateral laxity and greater joint line obliquity compared to gap balancing TKA

Abstract

Purpose The purpose of this study was to compare ligament balance and laxity proiles achieved throughout lexion in restricted kinematic alignment (rKA) and gap balancing (GB). rKA and GB both aim to improve soft tissue balance and reduce ligament releases in total knee arthroplasty (TKA). Methods One surgeon performed 68 rKA, another performed 73 GB TKAs using the same CR implant and robotic system. rKA limited femoral valgus and tibial varus to 6°, with tibial recuts performed to achieve balance. GB limited tibial varus and femoral valgus to 2°, with femoral resections adjusted to achieve mediolateral balance throughout lexion using predictive-gap planning software. Final joint laxity was measured using a robotic ligament tensioner. Statistical analyses were performed to compare diferences in mediolateral balance and joint laxity throughout lexion. Further analyses compared alignment, joint line elevation and orientation (JLO), and frequency of ligament releases and bone recuts. Results Both techniques reported greater lateral laxity throughout lexion, with GB reporting improved mediolateral balance from 10° to 45° lexion. GB resected 1.7 mm more distal femur (p ≤ 0.001) and had greater overall laxity than rKA throughout lexion (p ≤ 0.01). rKA increased JLO by 2.5° and 3° on the femur and tibia (p ≤ 0.001). Pre-operative and post-operative coronal alignment were similar across both techniques. rKA had a higher tibial recut rate: 26.5% vs 1.4%, p < 0.001. Conclusions rKA and GB both report lateral laxity but with diferent JLO and elevation. Use of a predictive-gap GB worklow resulted in greater mediolateral gap symmetry with fewer recuts. Level of evidence III, retrospective cohort study.

Arithmetic hip-knee-ankle angle and stressed hip-knee-ankle angle: equivalent methods for estimating constitutional lower limb alignment in kinematically aligned total knee arthroplasty

“…Recent strategies in the pursuit of more favourable outcomes following total knee arthroplasty (TKA) have focused on restoration of constitutional lower limb alignment and joint line obliquity. Termed kinematic alignment (KA), this method has been shown to more reliably restore soft tissue laxities and native joint kinematics [6, 28–30, 43, 54]. However, with the progressive deformity that follows loss of articular cartilage, determination of constitutional lower limb alignment is challenging [10].…”

Ligament Tension and Balance before and after Robotic-Assisted Total Knee Arthroplasty — Dynamic Changes with Increasing Applied Force

“…The OmniBotics System is an imageless roboticassisted TKA tensioning system that that can optimize implant positioning with predictive balance tools. [11][12][13][14][15][16][17] All patients had grade IV degenerative joint disease of the knee, and all knees had varus-type osteoarthritis with a varus deformity of 5.2 AE 3.2 degrees and sagittal deformity (flexion contracture) of 3.7 AE 6.4 degrees. Inclusion criteria included patients who received a robotic-assisted TKA with complete log files and exclusion criteria included any patients with severe ligament deficiencies or prior knee surgery.…”

Predictive Gap-balancing Reduces the Extent of Soft-tissue Adjustment Required After Bony Resection in Robot-assisted Total Knee Arthroplasty—A Comparison With Simulated Measured Resection

“…A digital joint tensioner (BalanceBot; Corin Group, UK) was then inserted into the joint to collect laxity data throughout flexion during an initial balance assessment with forces ranging from 70 to 90 N per side, as shown in Figure 1 a [ 10 , 12 ]. These initial balance assessment data were used as an input for a predictive gap planning software program which virtually placed the femoral component, rendering a postoperative gap prediction throughout flexion.…”

“…These initial balance assessment data were used as an input for a predictive gap planning software program which virtually placed the femoral component, rendering a postoperative gap prediction throughout flexion. Femoral sizing, anteroposterior positioning, flexion, rotation, valgus, and distal and posterior resection depths were all adjusted by the operating surgeon to optimize ligament balance throughout the flexion cycle, as seen in Figure 2 a. Femoral resections were then executed using the robotic cutting guide [ 12 , 13 ]. After femoral resection, the digital tensioner was inserted again to collect a final laxity assessment throughout flexion ( Fig.…”