Faster improvement in outcome scores in posterior stabilised total knee arthroplasty compared to medial congruent system with posterior cruciate ligament retained.

Most studies comparing medial pivot to the posterior stabilised (PS) systems sacrifice the PCL. It is unknown whether retaining the PCL in the Medial Congruent (MC) system may provide further benefit compared to the more commonly used PS system. A retrospective review of a single-surgeon's registry data comparing 44 PS and 26 MC with PCL retained (MC-PCLR) TKAs was performed. Both groups had similar baseline demographics. The PS and MC-PCLR groups had similar pre-operative range of motion (ROM) (PS:104º ± 20º vs. MC-PCLR: 101º ± 19º, p = 0.70), Oxford Knee Score (OKS) (PS: 27 ± 6 vs. MC-PCLR: 26 ± 7, p = 0.62), and Knee Society Scoring System (KS) Function Score (KS-FS) (PS: 52 ± 24 vs. MC-PCLR: 56 ± 23, p = 0.49). The pre-operative KS Knee Score (KS-KS) was significantly lower in the PS group (PS: 44 ± 14 vs. MC-PLR: 53 ± 18, p < 0.05). At 12-months post-operation, there was significant improvement in all parameters (p < 0.01). Both groups had similar ROM (PS: 115º ± 13º vs. MC-PCLR: 114º ± 10º, p = 0.98), OKS (PS: 41 ± 5 vs. MC-PCLR: 40 ± 4, p = 0.50), KS-FS (PS: 74 ± 22 vs. MC-PCLR: 77 ± 16, p = 0.78), and KS-KS (PS: 89 ± 10 vs. MC-PCLR: 89 ± 10, p = 0.89). The PS group had significant improvement in all parameters from preoperation to 3-month postoperation (p < 0.05), but not from 3-month to 1-year postoperation (p ≥ 0.05). The MC-PCLR group continued to have significant improvement from 3-month to 1-year postoperation (p < 0.05). Preserving the PCL when using MC may paradoxically cause an undesired additional restrain that slows the recovery process of the patients after TKA. Compared to MC-PCLR, a PS TKA may expect significantly faster improvement at 3 months post operation, although they will achieve similar outcomes at 1-year post operation.