Mechanical axis of the lower extremity determined by a new digital photographic method.
Assessment of the mechanical axis is routine during the examination of patients with lower extremity pain. Long-leg radiographic examination is the gold standard for exact measurement, but it is associated with a significant radiation dose. An alternative method to examine the mechanical axis has been warranted. This article validates a newly developed computerized photograph method to calculate the mechanical axis using a digital photograph. The location of the center of the femoral head was calculated using ink marks on both superior iliac spines. Twenty-five patients (10 women and 15 men) had both legs examined using the photographic method and long-leg radiography examination. The digital photograph method was found to be highly reliable. The interobserver absolute mean difference was 0.99°±0.85°, and the intraobserver absolute mean difference (day-to-day variation) was 1.04°±0.81°. The mechanical axis determined by the 2 methods was highly correlated (R=0.943). The long-leg radiography method was within an average of ±1.88° of the photographic method, with a 95% probability. The photographic method appears to be an effective alternative to conventional long-leg radiography. The photographic method seems convenient in the routine examination of patients with leg pain and children with suspected axial deformity and for follow-up after treatment for malalignment. Calculation coefficients for children and a possible racial difference remain to be studied.
Ole Højgaard
OH
Simonsen
Hanne
H
Thomsen
Søren Thorgaard
ST
Skou
Mikkel Meyer
MM
Andersen
D000328:Adult; D000368:Aged; D053587:Arthrometry, Articular / Q000379:methods*; D005260:Female; D006801:Humans; D007596:Joints / Q000033:anatomy & histology* / Q000502:physiology*; D007866:Leg / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010781:Photography / Q000379:methods*; D010808:Physical Examination / Q000379:methods*; D016059:Range of Motion, Articular / Q000502:physiology*; D015203:Reproducibility of Results; D012399:Rotation; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted