Sagittal component alignment is less reliable than coronal component alignment in a Chinese population undergoing navigated TKA

Abstract

BackgroundThe purpose of our study was to determine whether postoperative sagittal component alignments of primary total knee arthroplasty (TKA) using the conventional and navigated technique differed significantly. Additionally, we determined whether the use of navigation systems resulted in hyperextension of the femoral components in Chinese patients.MethodsThis retrospective study reviewed 36 consecutive patients (72 knees) who underwent simultaneous bilateral primary TKAs at our hospital from February 2011 to March 2012. One knee was replaced using a computer-assisted navigation system, and the contralateral knee was replaced with the conventional technique. The radiographic and clinical results of both groups were compared. The relationship between preoperative anatomic angles and component alignments in conventional TKA and navigated TKA was examined.ResultsThe radiographic results showed statistically significant differences only between the navigated and conventional groups for individual femoral coronal and sagittal component alignment. Femoral sagittal component alignment showed less deviation and tended to have hyperextension using the navigated technique (−0.35°) compared with the conventional technique (2.77°). There was no significant difference observed for the Knee Society Score (KSS) between the two groups at 2 years postoperatively.ConclusionsThe sagittal component alignment of primary TKA obtained using the conventional and navigated techniques differed significantly. Navigated TKAs resulted in a higher risk of hyperextension of the femoral components in Chinese patients.

Is the Femoral Component Flexion Affected by the Sagittal Femoral Shaft Bowing in Conventional Intramedually Guided TKA?

“…Young-Hoo Kim et al [30] studied 3018 patients who underwent total knee arthroplasty, they thought that when total knee components in the position of:femoral coronal alignment, 2-8°valgus; femoral sagittal alignment, 0-3°; tibial coronal alignment, 90°; tibial sagittal alignment, 0-7°; femoral external rotational alignment, 2-5°; tibial external rotational alignment, 2-5°; and overall anatomical knee alignment at an angle of 3-7.5°valgus, the survival rate of the prosthesis could improve. Whether coronal femoral shaft bowing or sagittal femoral shaft bowing, the femoral component alignments in the coronal plane or sagittal plane were affected [7,23]. The view was further con rmed in our study.…”

“…The overall incidence of mechanical tibiofemoral angle outliers was lower in the navigation group (15.4% versus 24.9%) [23]. However, there was controversial, Chen et al [7] found that navigated TKAs resulted in a higher risk of hyperextension of the femoral components and Jae Han Ko et al [7] found that the femoral implant position was more extended in navigated TKAs than in conventional TKAs. Xu et al [24] invented an extramedullary device which was easy and convenient and this instrument could help the surgeons perform TKAs with achieving better alignment in both coronal and sagittal planes.…”

“…Postoperatively, a standing whole-limb AP and lateral radiograph taken was used to measure mechanical tibiofemoral angle [22] for coronal femoral prosthesis alignment and sagittal femoral angle [7] for sagittal femoral prosthesis alignment. As a surrogate of overall limb alignment, mTFA(mechanical tibiofemoral angle of the knee), was de ned as the angle formed by the intersection between the mechanical axes of the femur (the line from the femoral head center to the femoral intercondylar notch center) and the tibia (the line from the ankle talus center to the center of tibial spine tips)(Fig.…”

“…Malalignment of components can cause premature component loosening, abnormal wear [5] and patellofemoral complications such as anterior knee pain [6]. Sagittal alignment of the femoral component may in uence the clinical results of TKA in various ways [7]. If a femoral component is placed in an overly exed position, the extension or polyethylene post wear resulting from impingement between the anterior part of the polyethylene insert and the intercondylar box in TKA [8].…”

Variation in Optimal Sagittal Alignment of the Femoral Component in Total Knee Arthroplasty

“…Numerous studies have detailed that the use of navigation during TKA can increase the risk of anterior femoral notching because of an increased risk of placing the component in extension. 12,24,29,[36][37][38] The risk of sagittal malalignment during navigated TKA increases in patients with shorter femurs and those with increased anterior bowing, which is commonly seen in women and patients who are Asian. 15,18,[36][37][38][39] The current study showed a significant correlation between the degree of DFF and the radius of curvature of the femur.…”