Acta Academiae Medicinae Sinica

Abstract:

Objective To explore the feasibility and clinical value of ultrasonography in evaluating the morphology and function of medial collateral ligaments (MCL) after total knee arthroplasty (TKA). Methods Totally 38 patients undergoing routine KTA (group A) and 22 patients undergoing constrained condylar knee arthroplasty KTA with MCL injury (group B) were included. Long axis views of MCL were taken and the MCL thickness was measured on femur side and tibial side 1 cm away from the joint line, respectively. The thicknesses were compared between the two groups. Subsequently, the gap between the metal part of the femoral prosthesis and the spacer after dynamic valgus stress was measured. The distribution and composition of the gap between the two groups were compared. Results High-frequency ultrasound clearly showed the prosthesis and MCL after TKA. MCL fiber structures of both groups were intact. The MCL thickness on the tibial side in group B was (0.25±0.06)cm, which was significantly thinner than group A [(0.32±0.14)cm] (t=2.12, P=0.040).For the femur side, there was no significant difference (t=1.65, P=0.110) between these two groups [(0.37±0.09) cm in group B versus (0.42±0.12)cm in group A]. Under the condition of valgus stress, the gaps between the metal part of the femoral prosthesis and the spacer could be found in 11 cases in group B but only in 1 case in group A. The proportion of gaps in group B was significantly higher than that in group A (Fisher’s exact test, P=0.000). Conclusions High-frequency ultrasound can clearly show the prosthesis and MCL after TKA. The injured MCL can be well joined but the thickness is thinner. Under the condition of valgus stress of the knee, the stability of the TKA can be evaluated according to the gap between the prosthesis and the spacer.

Key words: total knee arthroplasty, medial collateral ligament, high frequency ultrasound