Kinematic Versus Mechanical Alignment in Total Knee Replacement

Kinematic Versus Mechanical Alignment in Total Knee Replacement: a Randomized Double-blinded Controlled Study

This prospective controlled double-blind randomized study compares kinematic and mechanical alignment in TKA (Total knee arthroplasty). A total of 120 patients will be included and the surgery will be performed using CT based 3D printed PSI(Patient Specific Instruments) Cutting guides.

Total knee arthroplasty (TKA) is known, to significantly improve function and satisfaction in arthritic knee patients; nevertheless, a substantial percentage of these patients are not fully satisfied. Thus, several authors reported significantly improved outcomes after slightly under correcting varus knees after TKA. The concept of kinematic alignment (KA) even more addresses the patient´s individual anatomy with three-dimensional restoration of individual axes, joint lines and joint envelope of laxity. The aim of this prospective randomized study was to demonstrate equivalence between mechanical and kinematic alignment in restoring knee function in terms of subjective and objective outcomes.

In this prospective randomized controlled double-blind study 120 patients with osteoarthritic knees will be treated with a Medial Pivot TKA (Medacta Sphere GMK). The patients are divided into two groups. Group A receive the TKA using mechanical alignment principles, group B receive the kinematic alignment. The surgical technique was equal in both groups. CT-based 3D printed PSI cutting blocks were used for the saw cuts. Pre and postoperative standard x-rays were performed. To determine the subjective and objective outcomes the OKS(Oxford Knee Score), the KSS(Knee Society Sore), the FJS-12(Forgotten Joint Score) and the WOMAC Score were collected.

Inclusion Criteria:

• Symptomatic osteoarthritis of the knee
• Primary TKA
• UCLA Score (University of California, Los Angeles Score)>/= 4
• mMPTA: 85°- 90°
• Sum of mMPTA(mechanical medial proximal tibial angle) and mLDFA(mechanical lateral distal femoral angle) between 3°varus and 2°valgus from neutral

Exclusion Criteria:

• Minor Patient
• Pregnant or breast feeding woman
• Difference in the radius of medial and lateral condyles >2mm
• Previous osteotomy around the knee
• BMI >40
• Ligament instability likely to require higher level of constraint
• Previous infection or inflammatory disease
• Any Patient who cannot or will not provide informed consent for participation in the study