Introduction

Navigation has proven its ability to accurately restore coronal leg axis. For a good clinical outcome sagittal anatomy and balanced gaps are important. In a gap-balanced technique, the size of the flexion gap is equalled to that of the extension gap. Flexion of the femoral component has been described as a theoretical possibility to balance flexion and extension gap.

Aim

Aim of this study was to assess whether intentional femoral component flexion is helpful in balancing TKA gaps and in restoring sagittal anatomy.

Materials And Methods

Out of 331 patients, 146 Knees were chosen randomly, independent of their clinical result based on the completeness of navigation protocols and register data. Implantation was performed in a navigated, gap-balanced, tibia-first cut technique. Limbs where an additional procedure such as an osteotomy was required or where navigation had to be abandoned midway due to technical hitch were excluded from study. The femoral component flexion needed to equal flexion to extension gap was calculated based upon the navigation data. The flexion of femoral component, sagittal diameter, the anterior and posterior femoral offset were measured pre- and postoperatively based on the lateral radiographs. Flexion/extension gap differences pre- and postoperatively were analysed. Additionally, Preoperative and postoperative KNEE SOCIETY SCORES was analysed with a minimum follow up of 3 years. Statistical analysis with IBM-SPSS software was done.

Results

To achieve equal flexion and extension gap, the femoral component was flexed in 90%(131/146) of patients showing mean flexion of 3.6°in navigation analysis (0* minimum to 8* maximum) and 4* flexion in radiological analysis( 0* min – 10* max).Flexion required was <5* in 69% and >5* in 31%. Average flexion of 1.6* reduced flexion gap by 1mm.Based on this technique, it was possible to balance the extension gap and the flexion gap in 95% of patients with maximum difference of 0.5mm. The sagittal diameter was restored in 90%(131/146) of cases with alteration less than 2mm ; however, anterior offset was significantly reduced by 1.3 mm, and posterior offset was significantly increased by 1.6 mm. Average Knee society score improved from 33 preoperatively to 88 postoperatively. Incidence of femoral notching was nil.

CONCLUSION:.
Intentional flexion of the femoral component is definitely an option to reduce the flexion gap and helps to balance the gaps and simultaneously it restores the sagittal anatomy in TKA. At present, Intentional flexion of the femoral component is only possible in a navigated technique. An optional instrument should also be available in order to alter femoral component flexion to reap the benefits of the same in a conventional technique Flexion of the femoral component required to balance flexion and extension gap was >5* in 31% of the patients which was a significant finding . The reason for increased flexion required in Indian population may be due to increased distal femoral bowing in Indian population. Research on the same is necessary.