Fluoroscopic analyses were performed 13.5±7.8 months after surgery. At the time of analysis, the mean age of the patients was 74.8±7.2 years, the mean height was 155.0±7.8 cm, and the mean body weight was 64.6±10.6 kg. Of the 61 knees included in the analysis, 9 belonged to males and 52 belonged to females.
Flexion angle and rotation angle
The knees were gradually flexed from −2.9 ± 6.4° to 109.5 ± 13.34°. In the rotation angle, the femoral component displayed an external rotation angle of 3.2 ± 3.1° relative to the tibial component from 0° to 50° of flexion. Beyond 50° of flexion, there was no significant movement (Fig. 1).
AP translation
At the medial contact point, the femoral component showed 3.9 ± 2.0 mm of posterior movements from 0°–20° of flexion, followed by 1.8 ± 2.4 mm of anterior movements up to 80° of flexion. Beyond 80° of flexion, the femoral component showed 2.8 ± 1.4 mm posterior movements (Fig. 2).
At the lateral contact point, the femoral component showed 7.7 ± 2.8 mm of posterior movement from 0° –20° of flexion with no significant movement up to 80° of flexion. Beyond 80° of flexion, a posterior movement of 3.5 ± 1.8 mm was observed (Fig. 3).
The improvement of PROMs-SP
As summarised in Table 1, all function, sports, and recreational activities subscales in the KOOS improved postoperatively (p<0.01).
Table 1. The improvement of patient-reported outcome measures concerning sports (PROMs-SP)
KOOS (Function, sports and recreational activities)
|
Preoperative
|
Postoperative
|
Improvement
|
Squatting
|
5.0±5.5
|
11.3±6.6
|
6.3±7.4
|
Running
|
2.6±3.7
|
9.1±6.2
|
6.5±6.4
|
Jumping
|
2.5±3.6
|
8.9±6.1
|
6.4±6.4
|
Twisting/pivoting
|
5.6±4.8
|
13.9±6.3
|
8.4±7.5
|
Kneeling
|
5.0±4.7
|
11.2±6.2
|
6.2±6.6
|
Correlation between the kinematics and PROMs-SP
In the rotation angle, femoral external rotation was observed from 0°-50° of flexion. The amount of femoral external rotation did not correlate with PROMs-SP (Table 2).
Table 2. The correlation between rotation and patient-reported outcome measures concerning sports (PROMs-SP)
Flexion angle
|
KOOS (Function, sports and recreational activities)
|
|
Squatting
|
Running
|
Jumping
|
Twisting/pivoting
|
Kneeling
|
0-50°
|
rs
|
0.16
|
0.16
|
0.03
|
0.22
|
0.12
|
p-value
|
0.21
|
0.23
|
0.82
|
0.08
|
0.37
|
In medial AP translation, posterior translation was observed at 0-20° and 80-110° of flexion. The mild anterior translation was observed from 20-80° to flexion. Beyond 80° of flexion, posterior translation was positively correlated with squatting (Table 3).
Table 3. The correlation between medial anteroposterior translation and patient-reported outcome measures concerning sports (PROMs-SP)
Flexion angle
|
KOOS (Function, sports and recreational activities)
|
|
Squatting
|
Running
|
Jumping
|
Twisting/pivoting
|
Kneeling
|
0-20°
|
rs
|
-0.04
|
-0.23
|
-0.22
|
-0.02
|
0.03
|
p-value
|
0.72
|
0.07
|
0.1
|
0.87
|
0.8
|
20-80°
|
rs
|
0.14
|
0.12
|
0.08
|
-0.09
|
-0.07
|
p-value
|
0.27
|
0.33
|
0.52
|
0.48
|
0.57
|
80-110°
|
rs
|
0.34
|
0.14
|
0.11
|
0.21
|
0.25
|
p-value
|
0.008
|
0.27
|
0.42
|
0.11
|
0.06
|
In lateral AP translation, posterior translation was observed from 0-20° and to 80-110° of flexion. Beyond 80° of flexion, posterior translation was positively correlated with running, jumping, twisting/pivoting, and kneeling (Table 4).
Table 4. The correlation between lateral anteroposterior translation and patient-reported outcome measures concerning sports (PROMs-SP)
Flexion angle
|
KOOS (Function, sports and recreational activities)
|
|
Squatting
|
Running
|
Jumping
|
Twisting/pivoting
|
Kneeling
|
0-20°
|
rs
|
-0.11
|
-0.23
|
-0.19
|
0.06
|
-0.06
|
p-value
|
0.36
|
0.07
|
0.15
|
0.64
|
0.67
|
80-110°
|
rs
|
0.16
|
0.42
|
0.3
|
0.34
|
0.28
|
p-value
|
0.23
|
0.001
|
0.02
|
0.009
|
0.03
|
KOOS: Knee Injury and Osteoarthritis Outcome Score