Clinical outcomes of kinematically aligned medial pivot total knee arthroplasty: A systematic review and meta-analysis of current evidence

Abstract

Purpose: Kinematic alignment (KA) in total knee arthroplasty (TKA) focuses on restoring the natural joint line and ligament balance, potentially improving biomechanics and outcomes over mechanical alignment (MA). The medial pivot (MP) implant enhances joint stability by mimicking physiological knee motion. Still, its role within a KA protocol and the effects of retaining versus sacrificing the posterior cruciate ligament (PCL) are unclear. This study aimed to evaluate the clinical effectiveness, functional outcomes and biomechanical benefits of KA-TKA with MP implants based on the available literature. It also aimed to assess whether PCL retention or sacrifice leads to better postoperative function.

Methods: A systematic review and meta-analysis were conducted following PRISMA guidelines. A comprehensive search of PubMed, Embase and Web of Science up to January 2025 identified studies assessing KA-TKA with MP implants. Primary outcomes included patient-reported outcome measures (PROMs), range of motion (ROM), complication rates and implant survivorship. Subgroup analysis compared PCL retention and sacrifice.

Results: Fourteen studies (955 patients) met inclusion criteria. KA-TKA with MP implants resulted in significant ROM improvements (+11.35°, increased to +12.50° after sensitivity analysis) and enhanced PROMs (Oxford Knee Score +18.23, increased to +22.27 after sensitivity analysis; Knee Society Score [KSS] +49.61, functional KSS +42.50). No aseptic loosening or implant failures were reported. PCL sacrifice was associated with greater postoperative flexion (125.4° ± 12.1° vs. 116.4° ± 11.8°, p < 0.001), but functional outcomes were comparable.

Conclusions: KA-TKA with MP implants improves functional recovery, patient satisfaction, and short- to mid-term survivorship, supporting its adoption as a viable alternative to conventional TKA. Further long-term, randomized trials are needed to optimize PCL management and confirm its durability.

Level of evidence: Level IV.

Keywords: biomechanics; kinematic alignment; medial pivot; posterior cruciate ligament; total knee arthroplasty.

Figure 1

Preferred reporting items for systematic review and meta‐analyses (PRISMA) flow diagram of the studies included in the analysis. KA, kinematic alignment; TKA, total knee arthroplasty.

Figure 2

Assessment of the risk of bias of the individual studies included in the analysis according to the ROBINS‐I tool.

Figure 3

Forest plot. Comparison of Flexion Range results between preoperative and postoperative values. Giustra #1: PCL retained; Giustra #2: PCL sacrificed; Elorza #1: BiC; Elorza #2: MC; Cacciola #1: Reduced slope; Cacciola #2: Native slope. BiC, ball‐in‐socket; CI, confidence interval; MC, medial conformity; p, p‐value; PCL, posterior cruciate ligament; SD, standard deviation.

Figure 4

Forest plot. Comparison of KSS results between preoperative and postoperative values. Giustra #1: PCL retained; Giustra #2: PCL sacrificed. CI, confidence interval; KSS, Knee Society Score; p, p‐value; PCL, posterior cruciate ligament; SD, standard deviation.

Figure 5

Forest plot. Comparison of Oxford results between preoperative and postoperative values. Elorza #1: BiC; Elorza #2: MC. BiC, ball‐in‐socket; CI, confidence interval; MC, medial conformity; p, p‐value; PCL, posterior cruciate ligament; SD, standard deviation.

Figure 6

Forest plot. Comparison of functional KSS results between preoperative and postoperative values. Giustra #1: PCL retained; Giustra #2: PCL sacrificed. CI, confidence interval; KSS, Knee Society Score; p, p‐value; PCL, posterior cruciate ligament; SD, standard deviation.

Figure 7

Forest plot. Sensitivity analysis. Comparison of flexion range results between preoperative and postoperative values after exclusion of outlier studies. Giustra #2: PCL sacrificed; Elorza #1: BiC; Elorza #2: MC; Cacciola #1: Reduced slope; Cacciola #2: Native slope. BiC, ball‐in‐socket; CI, confidence interval; MC, medial conformity; p, p value; PCL, posterior cruciate ligament; SD, standard deviation.

Figure 8

Forest plot. Sensitivity analysis. Comparison of Oxford results between preoperative and postoperative values after exclusion of outlier studies. CI, confidence interval; p, p value; SD, standard deviation.