The Application Research Of Reconstruction Technology Of Constitutional Alignment In Patients With Varus Knees And BFLB In TKA

Objectives:Bilateral coronal femoral lateral bowing(BFLB)contributes to the bilateral constitutional varus of the femoral shaft,and BFLB can decelerate medial knee osteoarthritis(OA)progression.In this sense,the BFLB should be reserved in TKA,and the target knee alignment desired approximates the constitutional alignment(CA)in patients with BFLB.However,to date,no paper reports how to perform it.Methods:Firstly,the proximal and distal femur malorientation test(MOT)was performed by comparing the medial proximal femoral angle(MPFA)and anatomic lateral distal femoral angle(a-LDFA)between 47 patients(n=72 knees)with varus osteoarthritic knees and BFLB(>5°)and 50 volunteers(n=100 knees)with healthy knees and straight femoral shaft.If there is no significant geometric difference,so the virtual center of femoral head(VCFH)fell on the distal femoral mechanical axis(DMA)after accurate correction of the bowing,indicating that the DMA should be the femoral constitutional mechanical axis,i.e.,the CA.Second,the angle of bowing(?),the VCA(valgus correction angle)based on NMA(neutral mechanical axis)in patients and volunteers were measured respectively.Subsequently compare the VCA based on NMA in volunteers with the VCA formed by DMA and DAA(distal femoral anatomic axis)in patients.Finally,the distal femoral osteotomy was performed perpendicular to DMA in TKA.Whether medial soft tissue release was performed or not was assessed,the relationship between the cut surface of posterior condylar and TEA(transepicondylar axis)and whiteside line was assessed by O-Arm scan,central tracking of the patella was evaluated with the "no thumb test",and the postoperative angle formed by DMA and tibial mechanical axis(TMA)was measured to assess whether CA was restored successfully.Revision due to mechanical failure,aseptic loosening,or radiographic wear was registered,whereas revisions due to infection were not as this form of revision has no correlation with alignment following TKA.Results: The proximal and distal femur malorientation test was performed for patients with varus osteoarthritic knees and BFLB prior to TKA.The results showed that the MPFA(84.3° ± 3.8° or 85.1 ± 1.7°,P=0.26)and the a-LDFA(81.2° ± 1.9° or 80.9° ± 1.4°,P=0.44)were not significantly different between volunteers with healthy knees and those without BFLB,the angle of bowing(?)was 7.9° ± 2.9°(range,6-16°)and the preoperative mean VCA in patients was 8.6° ± 1.2°(range,6-11°),indicating a significangtly positive correlation between VCA and ? angle(p<0.01;Pearson's correlation coefficient was 0.613),the VCA based on NMA in volunteers was 5.3° ± 0.7°(range,4-7°)and the preoperative mean DAA-DMA angle in patients was 5.2° ± 0.8°(range,4.1-8.2°),there is no significangtly difference between VCA in volunteers and the preoperative DAA-DMA angle in patients.In the study the most important findings is that the extension and flexion gap balance was achieved after bone cuts without medial soft tissue release when the distal femur cut was performed perpendicular to the DMA,the O-Arm scan reveals that the cut surface of posterior condylar was parrell to TEA and perpendicular to whiteside line,the postoperative tracking of patella was good,and the postoperative mean DAA-TMA angle was 179 ± 0.5°(range,178.2°-179.9°)for all knees included,the preoperative constitutional alignment was restored successfully.None of the knees were revised or being considered for revision due to mechanical failure,aseptic loosening,or radiographic wear was registered at the latest follow-up.Conclusions:This study provides a novel technique to restore preoperative CA in patients with varus knees and BFLB.It is found that the distal femur should be cut perpendicular to DMA,so the lower limb alignment and soft tissue strains can be restored to the pre-arthritic state,and the knees would be stable and in a natural status after TKA.