Validity and Reliability of measuring femoral anteversion and neck-shaft angle in patients with cerebral palsy
Seoul National University Bundang Hospital
Seoul National University Children’s Hospital *

 Increased femoral anteversion and coxa valga are common deformities associated with intoeing gait and unstable hips in CP, which need surgical correction
 Physical examination and neck shaft angle measured on hip radiographs are primary tools evaluating femoral anteversion and coxa valga

 Physical examinations measuring femoral anteversion include
 Trochanteric prominence angle test (TPAT)
 Hip internal rotation (IR)
 Hip external rotation (ER)
 CT measurement is accurate, but expensive and involves radiation exposure

 To assess the validity and reliability of physical examinations measuring femoral anteversion and neck shaft angle measured on hip AP radiographs
 Concurrent validity
 Intra- and interobserver reliability

 Prospective study approved by IRB
 36 consecutive patients with CP scheduled for
SEMLS
 Mean age 11.0 years (SD 1.3)
 M : F = 26 : 10
 6 hemiplegia, 25 diplegia, and 5 quadriplegia
 GMFCS I / II / III / IV / V 5 / 11 / 11 / 7 / 2
 Exclusion
 Previous Op, trauma, infection, etc.

Standard method for concurrent validity of P/E

Standard method for concurrent validity of NSA on X-ray

 Physical exam measuring femoral AV
 Correlation with femoral anteversion measured on
2D CT
 NSA measured on X ray
 Correlation with NSA measured on 3D MPR CT image

 Interobserver reliability of physical exam using three orthopaedic surgeons on a single day
 Intra- and interobserver reliability of NSA on
X- ray
 Repeated measurements with an interval of 3 wks

 Validity

Pearson’s correlation coefficients
 Reliability
 Intraclass correlation coefficients (ICCs)
 2 way random effects, single measurement & absolute agreement
 Multiple regression test
 To predict the accurate femoral anteversion (CT) from physical exam

Summary of Measurements
Examiation Mean (deg) SD (deg) Range (deg)
TPAT
Hip IR
Hip ER
Femoral AT on CT
NSA on X ray
NSA on CT
40
60
38
36
142
139
17
17
14
18
10
8
-20 to 70
10 to 85
10 to 70
-26 to 73
119 to 169
118 to 162

Concurrent Validity of Physical exam and NSA on X ray
Examinations R value p-value
TPAT
Hip IR
0.862
0.787
<0.001
<0.001
Hip ER
NSA on X ray
-0.480
0.892
<0.001
<0.001

Interobserver Reliability of Physical exam
Examination ICCs
TPAT
Hip IR
Hip ER
0.809
0.889
0.530
95% CI
0.695 to 0.890
0.817 to 0.937
0.338 to 0.702

Intra- and interobserver reliability of NSA on X ray
Reliability ICCs 95% CI
Intraobserver
1 st examiner
2 nd examiner
3 rd examiner
Interobserver
1 st session
2 nd session
Overall
0.973
0.946
0.929
0.937
0.869
0.912
0.947 to 0.986
0.878 to 0.974
0.694 to 0.974
0.825 to 0.973
0.541 to 0.951
0.806 to 0.958

Femoval AV on CT
= 0.92 x TPAT - 3.2 (R 2 =0.829)

 TPAT and NSA on X ray showed clinically relevant validity and reliability compared with
CT measurement
 CT examination evaluating proximal femoral geometry could be replaced by physical examination and X ray in patients with CP, avoiding unnecessary radiation exposure

This study has been published in JBJS-Am.