A computed tomography-based analysis of proximal femoral geometry for lateral impingement with two types of proximal femoral nail anterotation in subtrochanteric fractures.
OBJECTIVE
To evaluate and analyse the geometrical discrepancies between the proximal femur and two types of AO/Association for the Study of Internal Fixation (AO/ASIF) Proximal Femoral Nail Anterotation (PFNA/PFNA-II) using computed tomography (CT)-based analysis in Asian patients, and its implication in lateral cortical impingement during reduction intra-operatively in subtrochanteric fractures.


METHODS
Coronal CT images of hips in 50 randomly selected healthy cases were analysed using a unique measurement method with respect to the height, diameter, bending angle and inclination angle of lateral cortex of proximal femur. The data were then compared with dimensions of PFNA and PFNA-II.


RESULTS
The average height of proximal femur was 61.1+/-5.2mm, diameter 18.1+/-1.5mm, bending angle 8.4+/-2.2 degrees and inclination angle of lateral cortex 11.9+/-1.1 degrees . The average impingement length of the lateral cortex was 54.2+/-4.7mm (range 41.4-64.2mm), which was shorter than the height of the proximal femur. On comparison with dimensions of PFNA and PFNA-II, the lateral inclination angle and impingement length were found to be discrepant in PFNA; however, in the latter the flat lateral surface helps avoiding impingement with the lateral femoral cortex.


CONCLUSIONS
Our study provides clear evidence that the flat lateral shape of PFNA-II is better suited for the femur of Asian patients by reducing the chances of impingement with the lateral proximal femoral cortex during intra-operative reduction in subtrochanteric fractures.
Joint Replacement and Trauma Service, Department of Orthopaedic Surgery, Konkuk University Medical Center, 4-12 Hwayang-dong Gwangjin-gu, Seoul 143-729, Republic of Korea.
Vineet
V
Tyagi
Jae Hyuk
JH
Yang
Kwang Jun
KJ
Oh
D044466:Asian People; D001858:Bone Nails; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000601:surgery; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation* / Q000379:methods; D017102:Fracture Healing / Q000502:physiology*; D006620:Hip Fractures / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008297:Male; D014057:Tomography, X-Ray Computed / Q000379:methods