Abstract
Background
Total knee arthroplasty (TKA) was primarily considered a successful procedure, several new knee implants were introduced in recent years that seek to obtain improved stability and higher flexion. One of the implant, Vanguard XPTM BiCruciate retaining (BCR), Zinmmer-Biomet, USA recreates a specific kinematic model through the principle of normal joint.
Patients and Method
An unselected consecutive series of sixty-two patients undergoing primary TKA using the cemented total knee system between August 2016 and April 2018 were studied. Twenty-seven knees was operated using Vanguard XP, subsequently thirty-five knees were received a TKA using cruciate retaining cemented total knee system FINETMCR, Nakashimamedical, Japan.
Postoperatively standing AP hip-to-ankle radiographs were obtained, from which the lower extremity mechanical axis, component angle were measured. The alignment goals were a neutral mechanical axis defined as a hip-to-ankle angle of 0°with the femoral and tibial components aligned perpendicular to the mechanical axis. The total operating time were quantified utilising an operating room database. The total operating time between TKAs performed with Vanguard XP BCR and those performed with FINE CR was compared in each group. All patients postoperatively was evaluated of clinical results the Japan Orthopedics Association(JOA) Knee scores. We evaluated femoral component posterior offset (PFCO) in both of two group. The maximal protrusion of the posterior condyle, posteriorly to the extension line parallel to the tibial shaft from the edge of the posterior tibial component was measured on true lateral radiographs.
Results
The JOA Knee score of Vanguard XP BCR group was 86.5±4.7 points, and the score of FINE group was 82.7±5.9 points, there was no statistical significance between the two groups on the clinical score. The operative time in Vanguard XP BCR was 137.2±14.6 minutes and significantly more compared to the time of FINE group 111.3±11.9 minutes. The mechanical axis angle in Vanguard XP BCR group was −1.3°±2.7, while FINE CR group was −0.7°±3.2, there was no statistical significance. The number of outliers for mechanical axis angle was Vanguard XP BCR group 25%, the FINE group 24%, between the two groups there was no statistical significance.
The mean value of the femoral component posterior offset ratio of Vanguard XP BCR was 14.4%±0.1. The mean value of the posterior offset ratio of FINE group was 16.7%±0.1, between the two groups there was statistical significance.
Discussion
Bellemans et al. first defined the concept of posterior condylar offset. They demonstrated that the maximum active flexion possible was limited by direct impingement of the posterior aspect of the tibial component against the posterior aspect of the femur. However, the offset also reduces the extension gap. An enlarged posterior femoral component may reduce the extension gap due to posterior tissue tightness. In this study, the femoral component posterior offset ratio of Vanguard XP BCR was good results compared to the CR type FINE. Clinical results and the mechanical axis angle was good both of the group, but the operative time in Vanguard XP BCR was significantly more compared to the time of FINE group.
Conclusion
Good early clinical results were obtained with Vanguard XP BCR knee implant, long-term follow-up studies are needed to confirm our findings.
