Comparison of postoperative alignment using fixed angle versus variable angle distal femoral resection in uncomplicated total knee replacement

PURPOSE

This study aimed to compare the postoperative alignment of the lower limbs using fixed angle versus variable valgus angle distal femur resection in uncomplicated total knee replacement (TKR) and to determine the mean valgus correction angle (VCA) in the study population.

METHODS

This was a prospective comparative study conducted between July 2018 and December 2019 in patients with osteoarthritic knees who underwent primary TKR. Forty-nine patients with 54 knees completed the study. They were randomized into fixed valgus angle (group A) and variable valgus angle (group B) groups. Twenty-four patients with 26 knees were in group A who had distal femur resection with 5-degree valgus correction, while 25 patients with 28 knees were in group B who had distal femur resection with individualized valgus correction angle calculated from hip-knee-ankle scanogram.

RESULTS

The demographic data were comparable in the two groups. There was no statistically significant difference between the groups in the mean preoperative mechanical femorotibial angle (MFTA). The fixed angle group had a mean postoperative MFTA of 2.0 ± 2.8°, while variable angle group had a mean of 1.6 ± 2.4°. However, the difference between the groups did not reach statistical significance (p = 0.60). The mean VCA in the study population was 5.8 ± 1.2° (Range 4-9°).

CONCLUSION

Our study has shown that the use of variable valgus angle for distal femur resection in uncomplicated TKR did not significantly improve the accuracy of restoring the postoperative coronal alignment within 0 ± 3°.

Effect of additional distal femoral resection on flexion deformity in posterior-stabilized total knee arthroplasty

PURPOSE

Flexion deformity after total knee arthroplasty (TKA) is associated with poor function and dissatisfaction and should, therefore, be avoided. In the case of preoperative flexion deformity, an increased distal resection of the femur may be necessary. The degree of resection required has only been determined for cruciate-retaining (CR) prostheses to date and varies considerably from study to study. Although, for many surgeons, the algorithm for the treatment of a flexion deformity includes the resection of the posterior cruciate ligament (PCL) before additional distal resection, the degree of resection necessary for posterior-stabilized (PS)-type prostheses is not known.

METHODS

Fifty consecutive patients (50 knees) who were due to undergo navigated TKA were included in this prospective study. At the end of the operation, the flexion deformity resulting from different sizes of distal femoral augmentations on the trial implants (0-8.5 mm) was determined using the navigation system.

RESULTS

A linear relationship of 2.2° ± 0.3° flexion deformity per mm distal femoral augmentation was found. This was not dependent on age, sex, the preoperative coronal alignment, or the preoperative flexion deformity.

CONCLUSIONS

In conclusion, after the removal of posterior osteophytes and posterior capsule release, around 5 mm of the distal femur must be further resected in the case of 10° flexion deformity and 9 mm in the case of 20° flexion deformity.

LEVEL OF EVIDENCE

II (Prospective cohort study).

Effect of individualized distal femoral valgus resection angle in primary total knee arthroplasty: A systematic review and meta-analysis involving 1300 subjects

BACKGROUND

Proper limb alignment and implant positioning are important for successful total knee arthroplasty (TKA). Whether any differences exist in restoration of limb alignment for valgus knees between fixed and individual femoral valgus correction angle (VCA) for distal femoral resection remains unknown.

METHODS

The PubMed, Medline, Embase, and Wangfang databases were searched to identify studies comparing individualized VCA and fixed VCA in the distal femoral valgus resection. The primary outcomes were the mechanical femorotibial angle (MFT angle) and the proportion of postoperative alignment deviation within ±3°. The secondary outcomes were femoral valgus correction angle (VCA), component angle (α angle and β angle).

RESULTS

Six studies with 1167 TKAs were analyzed quantitatively. The coronal limb alignments in individualized group were closer to neutral than fixed group with a mean 0.77° difference (95% CI, -1.43 to -0.11; P = .022; I² = 71.0%). Moreover, there were more patients' postoperative alignment deviation within neutral ±3° in the individualized group (RR, 1.23; 95% CI, 1.09 to 1.38; P = .00; I² = 36.4%). The α angle were closer to neutral in the individualized group, and there's 1.2° more deviation from neutral in the fixed group (95% CI, 0.99 to 1.41; P = .00; I² = 0%). No difference was found in the β angle between groups (WMD, 0.85; 95% CI, -0.09 to 1.78; P = .075; I² = 88.3%).

CONCLUSIONS

This systematic review and meta-analysis demonstrated that the individualized VCA for distal femoral resection could enhance the accuracy of postoperative limb alignment and femoral component alignment in the coronal plane. However, further high-quality RCTs and well-designed trials are still needed.

The intercondylar notch ceiling: an accurate reference for distal femoral resection in total knee arthroplasty for severely degenerated varus knees

PURPOSE

To measure the distance from the intercondylar ceiling to the lowest point of the medial and lateral femoral condyles in a healthy population so to obtain a clearly discernible and accurate landmark for proper distal femoral resection during total knee arthroplasty (TKA).

METHODS

Three-dimensional models of the lower extremities of 100 healthy Chinese subjects were constructed using computed tomography scans. The distance between the distal surface of the medial femoral condyle and the intercondylar notch ceiling, in the direction of the femoral mechanical axis, was measured.

RESULTS

The mean distance from the distal surface of the medial femoral condyle to the intercondylar notch ceiling was 9.1 ± 1.4 and 8.2 ± 1.4 mm in male and female subjects, respectively. Interestingly, this distance did not differ significantly with varying sizes of the distal femur.

CONCLUSIONS

The intercondylar notch ceiling could be used as an accurate landmark to determine the proper distal femoral resection level during TKA. For the clinical relevance, the distal femoral bone cut should be at the level of the intercondylar notch ceiling when using the most of the current TKA prosthesis systems.