Paper # 6: Influence of Intra-operative Soft Tissue Balance on Post-operative Flexion Angle in Cruciate-retaining Total Knee Arthroplasty

AbstractRecently, kinematically aligned total knee arthroplasty has been found to achieve better clinical outcomes than mechanically aligned TKA. Despite the good clinical outcomes that are reported at short- to mid-term follow-up, intraoperative variables that are associated with a better outcome have not been measured. Therefore, this study was conducted to compare intraoperative kinematics/soft tissue balance and the clinical outcomes of patients who underwent modified kinematically (restricted tibial cut) or mechanically aligned total knee arthroplasty. Sixty cruciate-retaining total knee arthroplasties (30 modified kinematically [3-degree varus and 7-degree posterior slope in tibial cut] and 30 mechanically aligned) were performed in patients with varus-type osteoarthritis using a navigation system. Intraoperative kinematics assessed by the navigation system and soft tissue balance assessed by an offset-type tensor were compared between the groups. One year postoperatively, the range of motion and 2011 Knee Society scores were compared between the groups. Kinematic assessment exhibited that tibial internal rotation during flexion was significantly maintained in the kinematic compared with the mechanical group (p < 0.05). Varus/valgus ligament balance at 90 and 120 degrees of flexion significantly maintained lateral laxity in the kinematic compared with the mechanical group (p < 0.05). Improvement of flexion angles, functional activity scores, and patient satisfaction were significantly better in the kinematic than in the mechanical group (p < 0.05). Modified kinematically aligned cruciate-retaining total knee arthroplasty maintained more tibial internal rotation and lateral laxity during flexion than mechanically aligned total knee arthroplasty; thus, the former may result in better clinical outcomes.

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Rotational Soft-Tissue Balance Is Highly Correlated with Rotational Kinematics in Total Knee Arthroplasty

The Journal of Knee Surgery ◽

10.1055/s-0041-1729619 ◽

2021 ◽

Author(s):

Tomofumi Kinoshita ◽

Kazunori Hino ◽

Tatsuhiko Kutsuna ◽

Kunihiko Watamori ◽

Hiromasa Miura

Keyword(s):

Total Knee Arthroplasty ◽

Soft Tissue ◽

Knee Arthroplasty ◽

Navigation System ◽

Knee Kinematics ◽

Soft Tissue Balance ◽

Posterior Stabilized ◽

Cruciate Retaining ◽

Rotational Kinematics ◽

Total Knee

AbstractRecovery of normal knee kinematics is critical for improving functional outcomes and patient satisfaction after total knee arthroplasty (TKA). The kinematics pattern after TKA varies from case to case, and it remains unclear how to reproduce normal knee kinematics. The present study aimed to evaluate rotational knee kinematics and soft-tissue balance using a navigation system and to assess the influence of intraoperative soft-tissue balance on the rotational knee kinematics. We evaluated 81 osteoarthritic knees treated with TKA using a posterior stabilized (50 knees) or cruciate retaining (31 knees) prosthesis. Rotational kinematics were assessed at 0, 30, 45, 60, and 90 degrees flexion angles by using a computer-assisted navigation system. Correlation between femorotibial rotational position and measured soft tissue balance was assessed by using Spearman's rank correlation coefficient. Rotational soft-tissue balance (the median angle of rotational stress) was significantly correlated with rotational kinematics (rotational axis of the femur relative to the tibia throughout the range of motion) at all measured angles after TKA. The correlation coefficients between the median angle of rotational stress and rotational kinematics were 0.97, 0.80, 0.74, 0.71, and 0.70 at 0, 30, 45, 60, and 90 degrees of flexion, respectively (p-values <0.0001 in all measured angles). The correlation coefficient increased as the knee approached full extension. Our findings suggest that soft-tissue balance is a key factor for rotational kinematics, following both cruciate-retaining and posterior-stabilized TKA.

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