Approximating the maximum tibial coverage in total knee arthroplasty does not necessarily result in implant malrotation

Abstract

Traditionally, the practice of the tibial component placement in total knee arthroplasty has focused on achieving maximum coverage without malrotation. However, the concept of maximizing coverage has not been well defined or researched and yet biased results are often produced. This study aimed to evaluate the effect of a prioritizing maximum coverage positioning strategy on the rotational alignment by using a strict computer algorithm. Computed tomographic scans of 103 tibial specimens were used to reconstruct three-dimensional tibia models. A virtual surgery was performed to generate the resection plane with a posterior slope of 7° on the proximal tibia. Symmetrical and anatomical tibial components were placed and analyzed with an automated program designed for approximating the maximum coverage based on the coherent point drift algorithm. We found that the average tibial coverage achieved across all specimens and implants was 85.62 ± 3.65%, ranging from 83.64 ± 4.10% to 86.69 ± 3.07%. When placed for maximal tibial coverage, the mean degree of rotation related to the Insall line was − 0.73° ± 4.53° for all subjects, 23% of the tibial components were malrotated. The average percentage position of the baseplate anteroposterior axis over the patellar tendon was 26.95 ± 14.71% from the medial edge. These results suggest that with specific design and proper placement of the component, approximating the maximum tibial coverage in total knee arthroplasty does not necessarily result in implant malrotation. the current tibial baseplates have shown good performance on the coverage when aligned parallel to the Insall line with the anteroposterior axis positioned between the medial 1/3 and medial 1/6 of the patella tendon. Insufficient implant coverage and bone support at the osteotomy level could increase the amount of bleeding into the articular cavity of the knee in the immediate postoperative period, which may also increase osteolysis from wear by debris in the long term follow-up, finally resulting in subsidence and instability 1,2. Meanwhile, proper tibial rotation is another key factor that is crucial to the kinematic alignment and long-term survivorship of the prosthesis 3-5. Ideally, a satisfying total knee arthroplasty (TKA) ought to maximize tibial coverage without causing tibial malrotation. Several studies have evaluated both tibial coverage and rotational alignment with virtual matching by using preoperative imageological data 6-13. These studies mainly focused on the comparison between anatomic and symmetric designs which had always been a controversial issue. However, the various definitions of the malrotation and coverage maximizing methods applied in these studies make it hard to draw a firm conclusion on the compromise between coverage and ideal rotation while the latter has an inherent priority 8,14. Theoretically, maximizing coverage usually requires a larger size of the tibial baseplate, which under normal circumstances

Curve-on-curve technique does not improve tibial coverage in total knee arthroplasty in comparison to tibial tuberosity technique with use of anatomical implants: randomized controlled trial

“…It resulted in significantly less malrotated internal components, as it was easier to estimate the relation between tibial rotation and coverage. Results of this study are not confirmed by another study by Shao et al [ 29 ] in which the authors stated that maximizing tibial plateau coverage does not necessarily result in implant malrotation. In our study, choice of technique had a significant impact on the value of tibial baseplate rotation.…”

A computational tool for automatic selection of total knee replacement implant size using X-ray images

“…The design of the base femur component was subtly adjusted for each model to reflect differences in transepicondylar (ML) width between the designs and ensure consistency with the dimensioning used in each of the surgical manuals. The design of the base tibia plate was kept constant and only the 2D profile was used like in prior studies ( Shao et al, 2020 ; Clary et al, 2014 ). A 2D analysis was sufficient for the tibia plate because the components only interface with the resected bone on a singular 2D face.…”

“…Poor implant size selection can result in increased rates of complications, revisions, and patient pain post-surgery ( Culler et al, 2017 ; Schroeder and Martin, 2019 ; Buller et al, 2018 ). The presence of regions of OUH ≥3 mm in particular is highlighted as being clinically significant and directly linked with cases of increased soft-tissue irritation, bleeding, osteolysis, laxity in flexion, subsidence, and instability ( Schroeder and Martin, 2019 ; Dai et al, 2014 ; Shao et al, 2020 ). Despite the importance of achieving a good fit, the accuracy of manual X-ray assessment and templating, for both femur components and tibia plates, can be poor.…”