Comparison of the radiological parameters between dynamic-referencing tactile guidance robotic system and Microplasty® instrumentation in unicompartmental knee arthroplasty

Abstract

Objectives: This study aims to compare the radiological outcomes of unicompartmental knee arthroplasty (UKA) performed by a navigation-based robotic system versus Microplasty® instrumentation.

Patients and methods: Between January 2018 and January 2019, a total of 90 knees of 75 patients (65 males, 10 females; mean age: 62.0±9.4 years; range, 50 to 73 years) were included. Among these, 54 knees underwent Oxford mobile-bearing UKA with an Microplasty® instrumentation set and 36 knees were operated with the aid of a Restoris® MCK with MAKO navigation-based robotic system. Postoperative anteroposterior and lateral X-rays of all patients were evaluated according to nine different parameters. On the femoral side, femoral varus-valgus angle, flexion-extension angle, femoral condyle posterior fit; on tibial side, tibial component varus/valgus, tibial posterior slope, medial, anterior, posterior and lateral fit of tibial component assessed.

Results: There was no significant difference between groups in terms of age, sex, and affected side. On the femoral side, no significant difference was observed in the component position between groups. On the tibial side, tibial component medial fit (p=0.032) and anterior fit (p=0.007) were better in navigation-based robotic system group.

Conclusion: Microplasty® instrumentation may lead to comparable implant positioning compared to a tactile-based navigated robotic instrumentation.

Figure 1. Study flowchart.

Figure 2. Measurements of implant positions in anteroposterior and lateral X-rays. (a) Measurements of implant positions in AP (A-Femoral component varus-valgus angle, red line indicates mechanical axis of femur and blue is the axis of femoral component. (b) Tibial component varus-valgus angle, red and blue lines are the mechanical axis of tibia and coronal axis of the tibial component, respectively. (c) Tibial component medial and lateral congruency, blue dashed line indicates medial border of tibial plateau, red and yellow dashed line is the medial and lateral borders of tibial component, green dashed line is the medial border of medial tibial eminence) and (d) Lateral femoral component flexion-extension angle, red dashed line is parallel to the posterior cortical line of femur, blue dashed line indicates the sagittal axis of femoral component and peg holes. (e) Femoral and tibial component posterior congruency, red dashed line is the posterior border of tibial component and blue dashed line is posterior border of tibial plateau, green dashed line indicates posterior condylar axis and yellow dashed line is started from the tip of posterior border of femoral component and goes to the parallel of the green line. (f) Tibial component anterior congruency and posterior tilt, Red line indicates tibial mechanical axis, blue line is the sagittal axis of tibial component, green dashed line is anterior margin of tibial component and parallel to sagittal axis of tibial component, yellow dashed line anterior border of tibial plateau and goes parallel to the green dashed line) radiographic views.

Figure 3. Restoris® MCK UKA has a 30° angle between the femoral condyle axis and the femoral peg. UKA: Unicompartmental knee arthroplasty.