Comparison of planned and achieved implant position in total knee arthroplasty with patient-specific positioning guides

Figures & data

Figure 1. Preoperative planning software (Materialise NV) and postoperative CT measurements for frontal femoral component angle (FFCA), sagittal femoral component angle (SFCA), axial femoral component angle (AFCA), frontal tibial component angle (FTCA), and sagittal tibial component angle (STCA).

Table 1. The target angle from the preoperatively planned alignment from planning software and postoperative CT measurements depicted as mean and SD from the 2 observers

	Target	Mean	SD	95% CI	p-value
Femur
Frontal femoral component angle (FFCA)^a	0.0	1.2	1.5	0.8 to1.7	< 0.001
Sagittal femoral component angle (SFCA)^b	–2.8	–4.4	4.0	–5.6 to –3.1	0.01
Axial femoral component angle (AFCA)^a	0.0	0.5	1.4	0.04 to 0.88	0.03
Tibia
Frontal tibial component angle (FTCA)^a	0.0	0.4	2.5	–0.3 to 1.2	0.3
Sagittal tibial component angle (STCA) ^a	–3.0	–3.7	2.3	–4.4 to –3.0	0.07

^a One-sample t-test.

^b Paired-samples t-test.

Positive and negative values for FFCA and FTCA represent varus and valgus, respectively. Positive values for SFCA and STCA represent extension, and negative values indicate that the component is placed in flexion. For the AFCA, internal rotation is represented by negative values and external rotation by positive values.

Table 2. Intraclass correlation (ICC) between observer 1 and observer 2 in postoperative CT measurements

	ICC	p-value
FFCA	0.75	< 0.001
SFCA	0.93	< 0.001
AFCA	0.49	0.001
FTCA	0.89	< 0.001
STCA	0.91	< 0.001

Figure 2. Box plot showing the distributions of FFCA, SFCA, AFCA, FTCA, and STCA. The boxes show the median and interquartile range (IQR). The whiskers represent the range where the lowest and highest values are not more than 1.5 × IQR above the median. Circles represent outliers, i.e. values more than 1.5 × IQR from the median.

Figure 3. Distribution of the postoperative HKA angle. Angles greater and less than 180 degrees represent valgus and varus, respectively.