Effect of Coronal Alignment on 10-Year Survivorship of a Single Contemporary Total Knee Arthroplasty

Abstract

Debate remains regarding the utility of mechanical axis alignment as a predictor of durability after total knee arthroplasty (TKA). Our study aimed to assess the effects of coronal alignment on implant durability, clinical outcomes, and radiographic results with a single fixed-bearing TKA design. All patients undergoing primary cemented TKA of a single design (Stryker Triathlon) from 2005-2007 with >10 years of follow-up and available pre-operative and post-operative hip-knee-ankle radiographs were included (n = 89). Radiographs were measured to determine coronal alignment and assessed for loosening. Mean preoperative mechanical axis alignment was -6° ± 6.7° (varus, range, -16°-23°), while mean post-operative alignment was -1° ± 2.7° (varus, range, -3°-15°). The aligned group was defined as knees with a post-operative mechanical axis of 0° ± 3° (n = 73) and the outlier group as those outside this range (n = 16). No patients underwent revision. Ten-year survivorship free from any reoperation was 99% and 100% in the aligned and outlier groups, respectively (p = 0.64). Knee Society scores improved significantly in both groups (p < 0.001) and did not differ at final follow-up (p = 0.15). No knees demonstrated radiographic evidence of loosening. Post-operative mechanical axis alignment within 3° of neutral was not associated with improved implant durability, clinical outcomes, or radiographic results at 10 years following primary TKA.

Keywords: coronal alignment; mechanical axis; survivorship; total knee arthroplasty.

Figure 1

Preoperative (A) and post-operative (B) standing hip–knee–ankle radiographs following primary total knee arthroplasty (TKA) of patient in the outlier group. Line B–F represents the mechanical axis of the limb. The angle formed by lines A–D and C–E represents the mechanical axis of the femur. Angle A–D–B represents the femoral mechanical axis (FMA) angle. The angle formed by lines H–K and G–I represents the mechanical axis of the tibia. The distance from point J to the mechanical axis of the limb represents the post-operative mechanical width.

Figure 2

Bar graph depicting the distribution of the post-operative alignment around the mechanical axis. Negative values indicate varus alignment, and positive values represent valgus alignment.