Response to: Is fixed distal femoral cutting angle still justifiable in total knee replacement” – Letter to editor

letter

. 2018 Nov 6;10(3):635. doi: 10.1016/j.jcot.2018.11.001

PMCID: PMC6492233 PMID: 31061606

We are thankful to the reader who found our article¹ well researched and would like to respond to their queries, as follows –

1.
The reader has raised a concern about the changes in the alignment on weight bearing. We agree that the overall alignment of the limb may change on weight bearing, but there would not be any change in the femoral valgus angle (FVA). In the present article, we have measured the femoral valgus angle (FVA) based on the CT scan of the lower limb. Since the study was measuring the FVA only and did not keep the overall alignment of the lower limb, as the outcome measure, we believe the weight bearing measurement would not change FVA.
2.
The FVA of the lower limb is calculated between the anatomical and mechanical axis. Mullaji et al.² had described a three-point relationship of the distal femur in their study, whereas all the other studies have measured the FVA, using the standard technique mentioned in the article.³ The purpose of our study was to calculate the overall FVA and evaluate the factors causing variations of the same.
3.
The decision regarding using a fixed FVA or individualizing the FVA is a matter of debate, in the current arthroplasty literature. We beg to differ from the reader that the FVA would dramatically change if the deformity of the knee is high. We believe that the factors affecting the distal FVA are bowing of the femoral shaft and alterations in the neck-shaft angle and not the overall deformity of the knee.

References

1.Vaishya R., Vijay V., Edomwonyi E.O., Agarwal A.K. Fixed distal femoral valgus cutting angle is still justifiable in total knee replacement. J Clin Orthop Trauma. 2018 Apr-Jun;9(2):112–115. doi: 10.1016/j.jcot.2017.02.007. [DOI] [PMC free article] [PubMed] [Google Scholar]
2.Mullaji A.B., Marawar S.V., Mittal V. A comparison of coronal plane axial femoral relationships in Asian patients with varus osteoarthritic knees and healthy knees. J Arthroplasty. 2009 Sep;24(6):861–867. doi: 10.1016/j.arth.2008.05.025. [DOI] [PubMed] [Google Scholar]
3.Bardakos N., Cil A., Thompson B., Stocks G. Mechanical axis cannot be restored in total knee arthroplasty with a fixed valgus resection angle: a radiographic study. J Arthroplasty. 2007 Sep;22(6 Suppl 2):85–89. doi: 10.1016/j.arth.2007.04.018. [DOI] [PubMed] [Google Scholar]