Superior patient satisfaction in medial pivot as compared to posterior stabilized total knee arthroplasty: a prospective randomized study

Purpose

Medial pivot (MP) total knee arthroplasty (TKA) aims to restore native knee kinematics due to highly conforming medial tibio-femoral articulation with survival comparable to contemporary knee designs. Posterior stabilized (PS) TKAs use cam-post mechanism to restore native femoral rollback. However, there is conflicting evidence regarding the reported patient satisfaction with MP TKA designs when compared to PS TKAs. The primary aim of this study is to compare the patient satisfaction between MP and PS TKA and the secondary aim is to establish potential reasons behind any differences in the outcomes noted between these two design philosophies.

Methods

In this IRB-approved single surgeon, single centre prospective RCT, 53 patients (mean age 62 years, 42 women) with comparable bilateral end-stage knee arthritis undergoing simultaneous bilateral TKA were randomized to receive MP TKA in one knee and PS TKA in the contralateral knee. At 4 years post-surgery, all patients were assessed using Knee Society Score (KSS)-Satisfaction and -Expectation scores, and Oxford Knee Score (OKS). In addition, all the patients underwent standardized radiological and in vivo kinematic assessment.

Results

Patients were more satisfied with the MP TKA as compared to PS TKA: mean KSS-Satisfaction [34.5 ± 3.05 in MP and 31.7 ± 3.16 in PS TKAs (p < 0.0001)] and mean KSS-Expectation scores [12.5 ± 1.39 in MP TKAs and 11.2 ± 1.41 in PS TKAs (p < 0.0001)]. No significant difference was noted in any other clinical outcomes. The in vivo kinematics of MP TKAs was significantly better than those of PS TKAs.

Conclusion

MP TKAs provide superior patient satisfaction and patient expectations as compared to PS TKA. This may be related to better replication of natural knee kinematics with MP TKA.

Level of evidence

I.