Optimal Intersurface Stability for Unicompartmental Femoral Component Design with Two Pegs Placed on the Distal Resection Surface: 5 Mm Peg Length Increment and 10° Peg Inclination

PurposeThe present study aimed to identify the optimal design of the unicompartmental femoral component through parameter analysis and stability evaluation.MethodsA finite element (FE) analysis was applied to analyse and adjust the parameter combinations of the anterior tilt angle of the posterior condyle resection surface, the position of the peg, the length of the peg and the inclination angle of the peg, resulting in 10 different FE models. Setting three knee flexion angles of 8.4 degrees (maximum load state during walking), 40 degrees (maximum load state during stair climbing) and 90 degrees (maximum load state during squatting exercise), quantitatively analysing the micromotion values of the bone-prosthesis interface and defining a weighted scoring formula to evaluate the stability of different FE models. The validity of the FE analysis was verified using the Digital Image Correlation (DIC) device.ResultsThe errors between the FE analysis and the DIC test at three flexion angles were 5.6%, 1.7% and 11.1%. The 10 different femoral component design models were measured separately. The FE analysis demonstrated that the design with a 0 degrees anterior tilt angle of the posterior condyle resection surface, both pegs placed on the distal resection surface, lengthened 5 mm pegs and a 10 degrees peg inclination angle provided the best stability.ConclusionThe current study proposed a method for evaluating the stability of the femoral component design. The optimal intersurface stability design of the unicompartmental femoral component was achieved with two pegs placed on the distal resection surface, a 5-mm peg length increment and a 10 degrees peg inclination. These results might provide a reference for the selection of unicompartmental femoral components in clinical practice and therefore improve the survival rate of future unicompartmental knee arthroplasty.Level of EvidenceLevel III.