2017 ISAKOS Biennial Congress ePoster #1226

 

Femoral Shaft Bowing in the Coronal Plane has More Significant Effect on the Coronal Alignment of TKA than Proximal or Distal Variations of Femoral Shape

Jae-Young Kim, MD, Seoul, Song-pa KOREA, REPUBLIC OF
Seong-Il Bin, MD, PhD, Seoul KOREA, REPUBLIC OF
Jong-Min Kim, MD, PhD, Seoul KOREA, REPUBLIC OF
Bum-Sik Lee, MD, Seoul KOREA, REPUBLIC OF
Sung-Mok Oh, MD, Seoul KOREA, REPUBLIC OF

Asan Medical Center, Seoul, Seoul, KOREA, REPUBLIC OF

FDA Status Not Applicable

Summary

The femoral intramedullary guide angle was mainly influenced by femoral shaft bowing among femoral deformities in the coronal plane.

ePosters will be available shortly before Congress

Abstract

Purpose

The aim of this study was to determine (1) variations in the shape of the proximal, middle, and distal
femur in a series of Korean patients who had undergone total knee arthroplasty (TKA), (2) the preoperative relationship between these three parameters and the distal valgus cutting angle referenced off the femoral intramedullary guide, and (3) whether there was any relationship between femoral bowing and variations in the shape of the proximal or distal femur in the coronal plane.

Methods

The preoperative long-standing anteroposterior radiographs of 316 consecutive osteoarthritis patients who underwent primary TKA from 2009 to 2011 were examined. The femoral neck shaft angle, the femoral shaft
bowing angle, and the mechanical lateral distal femoral angle were measured to assess the shape of the proximal,
middle, and distal femur, respectively. The valgus cutting angle of the femur was defined as the angle between the distal anatomical and mechanical axes of the femur.

Results

The study population showed large variations in femoral shape. The mean femoral intramedullary guide angle
was 6.5° ± 1.3° (range: 4°–13°). The femoral shaft bowing angle was the factor that showed the strongest correlation with this angle (P<0.001). The mechanical lateral distal femoral angle showed only a weak correlation (P = 0.001), and the femoral neck shaft angle showed no correlation (n.s.). The femoral shaft bowing angle showed a weak correlation with the mechanical lateral distal femoral angle (P = 0.001), but was
not significantly correlated with the femoral neck shaft angle (n.s.). Apparent femoral bowing (>3° of lateral or medial bowing) was found in 42 (13.3 %) of cases (37 cases of lateral bowing and five of medial bowing). Cases with lateral apparent femoral bowing >3° had a distal cutting angle of 8.6° ± 2.2° relative to the femoral intramedullary guide.

Conclusion

The femoral intramedullary guide angle was mainly influenced by femoral shaft bowing among femoral deformities in the coronal plane. Therefore, to increase the accuracy of distal femoral cut during TKA, it is necessary to confirm femoral deformities and to measure the femoral intramedullary guide angle preoperatively from coronal radiographs covering the whole femur.

Level of evidence IV.

Keywords Femoral bowing in the coronal plane, Alignment, Total knee arthroplasty, Angle of femoral intramedullary guide