Introduction

OtisMed Shape Match ® patient specific implant cutting jigs were designed to place TKA in kinematic alignment (KA) rather than traditional mechanical alignment (MA). This product was withdrawn from the market in 2013.

It has been hypothesised that KA might lead to early implant failure. Initial evidence has not supported this.

We present 10 year outcome data for the largest single centre cohort to date.

Methodology

Between 2010 and 2013, 127 Shape Match® TKAs were implanted in 119 individuals.

Retrospective review of long leg post-operative radiographs assessed femoral mechanical anatomical angle (FMA), tibial mechanical angle (TMA), hip-knee-ankle angle (HKA), posterior tibial slope (PTS) and femoral component flexion.

Oxford Knee Scores (OKS), revision and further surgery rates were reviewed.

Results

4 (3.1%) patients underwent revision for instability, recurrent haemarthrosis, stiffness and infection respectively. In this subgroup, PTS ranged from 9–25° (SD 7.5°). PTS range for non-revision subgroup was 1–23° (SD 4.6).

1 patient with a PTS of 21° had failure of quadriceps tendon, but was not revised.

Mean OKS at 1year = 38.1 (SD 1.08), 2 years = 39.3 (SD 1.08), 5 years = 40.8 (SD 4.11).

PTS had the largest impact on OKS, with <10° slope conferring a higher OKS.

Conclusions

At 10 year follow up, this cohort did identify several cases where excessive PTS was evident. This may have led to revision surgery and contributed post-operative complications. PTS, unlike other alignment measures, impacted OKS results. Overall revision rate and OKS were consistent with registry and other published data.